AIDS. Lesions of the oral cavity. Preventive and therapeutic means.

 

Human immunodeficiency virus infection / acquired immunodeficiency syndrome (HIV/AIDS) is a disease of the human immune system caused by infection with human immunodeficiency virus (HIV). During the initial infection, a person may experience a brief period of influenza-like illness. This is typically followed by a prolonged period without symptoms. As the illness progresses, it interferes more and more with the immune system, making the person much more likely to get infections, including opportunistic infections and tumors that do not usually affect people who have working immune systems.

Signs and symptoms

There are three main stages of HIV infection: acute infection, clinical latency and AIDS.

Acute infection

The initial period following the contraction of HIV is called acute HIV, primary HIV or acute retroviral syndrome. Many individuals develop an influenza-like illness or a mononucleosis-like illness 2–4 weeks post exposure while others have no significant symptoms. Symptoms occur in 40–90% of cases and most commonly include fever, large tender lymph nodes, throat inflammation, a rash, headache, and/or sores of the mouth and genitals. The rash, which occurs in 20–50% of cases, presents itself on the trunk and is maculopapular, classically. Some people also develop opportunistic infections at this stage.  Gastrointestinal symptoms such as nausea, vomiting or diarrhea may occur, as may neurological symptoms of peripheral neuropathy or Guillain-Barre syndrome.  The duration of the symptoms varies, but is usually one or two weeks.

Due to their nonspecific character, these symptoms are not often recognized as signs of HIV infection. Even cases that do get seen by a family doctor or a hospital are often misdiagnosed as one of the many common infectious diseases with overlapping symptoms. Thus, it is recommended that HIV be considered in patients presenting an unexplained fever who may have risk factors for the infection

Clinical latency

The initial symptoms are followed by a stage called clinical latency, asymptomatic HIV, or chronic HIV. Without treatment, this second stage of the natural history of HIV infection can last from about three years  to over 20 years  (on average, about eight years). While typically there are few or no symptoms at first, near the end of this stage many people experience fever, weight loss, gastrointestinal problems and muscle pains. Between 50 and 70% of people also develop persistent generalized lymphadenopathy, characterized by unexplained, non-painful enlargement of more than one group of lymph nodes (other than in the groin) for over three to six months.

Although most HIV-1 infected individuals have a detectable viral load and in the absence of treatment will eventually progress to AIDS, a small proportion (about 5%) retain high levels of CD4+ T cells (T helper cells) without antiretroviral therapy for more than 5 years. These individuals are classified as HIV controllers or long-term nonprogressors (LTNP). Another group is those who also maintain a low or undetectable viral load without anti-retroviral treatment who are known as “elite controllers” or “elite suppressors”. They represent approximately 1 in 300 infected persons.

Acquired immunodeficiency syndrome

Acquired immunodeficiency syndrome (AIDS) is defined in terms of either a CD4+ T cell count below 200 cells per µL or the occurrence of specific diseases in association with an HIV infection.  In the absence of specific treatment, around half of people infected with HIV develop AIDS within ten years. The most common initial conditions that alert to the presence of AIDS are pneumocystis pneumonia (40%), cachexia in the form of HIV wasting syndrome (20%) and esophageal candidiasis. Other common signs include recurring respiratory tract infections.

Opportunistic infections may be caused by bacteria, viruses, fungi and parasites that are normally controlled by the immune system. Which infections occur partly depends on what organisms are common in the person’s environment.  These infections may affect nearly every organ system.

People with AIDS have an increased risk of developing various viral induced cancers including: Kaposi’s sarcoma, Burkitt’s lymphoma, primary central nervous system lymphoma, and cervical cancer.  Kaposi’s sarcoma is the most common cancer occurring in 10 to 20% of people with HIV. The second most common cancer is lymphoma which is the cause of death of nearly 16% of people with AIDS and is the initial sign of AIDS in 3 to 4%. Both these cancers are associated with human herpesvirus 8. Cervical cancer occurs more frequently in those with AIDS due to its association with human papillomavirus (HPV).

Additionally, people with AIDS frequently have systemic symptoms such as prolonged fevers, sweats (particularly at night), swollen lymph nodes, chills, weakness, and weight loss. Diarrhea is another common symptom present in about 90% of people with AIDS.  They can also be affected by diverse psychiatric and neurological symptoms independent of opportunistic infections and cancers.

Transmission

HIV is transmitted by three main routes: sexual contact, exposure to infected body fluids or tissues, and from mother to child during pregnancy, delivery, or breastfeeding (known as vertical transmission). There is no risk of acquiring HIV if exposed to feces, nasal secretions, saliva, sputum, sweat, tears, urine, or vomit unless these are contaminated with blood. It is possible to be co-infected by more than one strain of HIV—a condition known as HIV superinfection.

1.    Sexual

The most frequent mode of transmission of HIV is through sexual contact with an infected person. The majority of all transmissions worldwide occur through heterosexual contacts (i.e. sexual contacts between people of the opposite sex); however, the pattern of transmission varies significantly among countries. In the United States, as of 2009, most sexual transmission occurred in men who had sex with men, with this population accounting for 64% of all new cases.

As regards unprotected heterosexual contacts, estimates of the risk of HIV transmission per sexual act appear to be four to ten times higher in low-income countries than in high-income countries. In low-income countries, the risk of female-to-male transmission is estimated as 0.38% per act, and of male-to-female transmission as 0.30% per act; the equivalent estimates for high-income countries are 0.04% per act for female-to-male transmission, and 0.08% per act for male-to-female transmission. The risk of transmission from anal intercourse is especially high, estimated as 1.4–1.7% per act in both heterosexual and homosexual contacts. While the risk of transmission from oral sex is relatively low, it is still present. The risk from receiving oral sex has been described as “nearly nil” however a few cases have been reported. The per-act risk is estimated at 0–0.04% for receptive oral intercourse. In settings involving prostitution in low income countries, risk of female-to-male transmission has been estimated as 2.4% per act and male-to-female transmission as 0.05% per act.

Risk of transmission increases in the presence of many sexually transmitted infections and genital ulcers.[35] Genital ulcers appear to increase the risk approximately fivefold. Other sexually transmitted infections, such as gonorrhea, chlamydia, trichomoniasis, and bacterial vaginosis, are associated with somewhat smaller increases in risk of transmission.

The viral load of an infected person is an important risk factor in both sexual and mother-to-child transmission. During the first 2.5 months of an HIV infection a person’s infectiousness is twelve times higher due to this high viral load. If the person is in the late stages of infection, rates of transmission are approximately eightfold greater.

Commercial sex workers (including those in pornography) have an increased rate of HIV. Rough sex can be a factor associated with an increased risk of transmission. Sexual assault is also believed to carry an increased risk of HIV transmission as condoms are rarely worn, physical trauma to the vagina or rectum is likely, and there may be a greater risk of concurrent sexually transmitted infections.

2.    Body fluids

The second most frequent mode of HIV transmission is via blood and blood products. Blood-borne transmission can be through needle-sharing during intravenous drug use, needle stick injury, transfusion of contaminated blood or blood product, or medical injections with unsterilised equipment. The risk from sharing a needle during drug injection is between 0.63 and 2.4% per act, with an average of 0.8%. The risk of acquiring HIV from a needle stick from an HIV-infected person is estimated as 0.3% (about 1 in 333) per act and the risk following mucus membrane exposure to infected blood as 0.09% (about 1 in 1000) per act. In the United States intravenous drug users made up 12% of all new cases of HIV in 2009, and in some areas more than 80% of people who inject drugs are HIV positive.

HIV is transmitted in About 93% of blood transfusions involving infected blood. In developed countries the risk of acquiring HIV from a blood transfusion is extremely low (less than one in half a million) where improved donor selection and HIV screening is performed; for example, in the UK the risk is reported at one in five million. In low income countries, only half of transfusions may be appropriately screened (as of 2008), and it is estimated that up to 15% of HIV infections in these areas come from transfusion of infected blood and blood products, representing between 5% and 10% of global infections.

Unsafe medical injections play a significant role in HIV spread in sub-Saharan Africa. In 2007, between 12 and 17% of infections in this region were attributed to medical syringe use. The World Health Organisation estimates the risk of transmission as a result of a medical injection in Africa at 1.2%.  Significant risks are also associated with invasive procedures, assisted delivery, and dental care in this area of the world.

People giving or receiving tattoos, piercings, and scarification are theoretically at risk of infection but no confirmed cases have been documented. It is not possible for mosquitoes or other insects to transmit HIV.

3.    Mother-to-child

HIV can be transmitted from mother to child during pregnancy, during delivery, or through breast milk. This is the third most common way in which HIV is transmitted globally. In the absence of treatment, the risk of transmission before or during birth is around 20% and in those who also breastfeed 35%. As of 2008, vertical transmission accounted for about 90% of cases of HIV in children.  With appropriate treatment the risk of mother-to-child infection can be reduced to about 1%. Preventive treatment involves the mother taking antiretroviral during pregnancy and delivery, an elective caesarean section, avoiding breastfeeding, and administering antiretroviral drugs to the newborn.  Many of these measures are however not available in the developing world. If blood contaminates food during pre-chewing it may pose a risk of transmission.

Virology

Classification

HIV is a member of the genus Lentivirus, part of the family Retroviridae.  Lentiviruses have many morphologies and biological properties in common. Many species are infected by lentiviruses, which are characteristically responsible for long-duration illnesses with a long incubation period. Lentiviruses are transmitted as single-stranded, positive-sense, enveloped RNA viruses. Upon entry into the target cell, the viral RNA genome is converted (reverse transcribed) into double-stranded DNA by a virally encoded reverse transcriptase that is transported along with the viral genome in the virus particle. The resulting viral DNA is then imported into the cell nucleus and integrated into the cellular DNA by a virally encoded integrase and host co-factors.Once integrated, the virus may become latent, allowing the virus and its host cell to avoid detection by the immune system. Alternatively, the virus may be transcribed, producing new RNA genomes and viral proteins that are packaged and released from the cell as new virus particles that begin the replication cycle anew.

Two types of HIV have been characterized: HIV-1 and HIV-2. HIV-1 is the virus that was initially discovered and termed both LAV and HTLV-III. It is more virulent, more infective, and is the cause of the majority of HIV infections globally. The lower infectivity of HIV-2 compared to HIV-1 implies that fewer of those exposed to HIV-2 will be infected per exposure. Because of its relatively poor capacity for transmission, HIV-2 is largely confined to West Africa.

Structure and genome

The genome and proteins of HIV (human immunodeficiency virus) have been the subject of extensive research since the discovery of the virus in 1983. Each virion comprises a viral envelope and associated matrix enclosing a capsid, which itself encloses two copies of the single-stranded RNA genome and several enzymes. The discovery of the virus itself was not until two years after the first major cases of AIDS associated illnesses were reported in 1981.

Structure

HIV is different in structure from other retroviruses. It is around 120 nm in diameter (around 60 times smaller than a red blood cell) and roughly spherical.

HIV-1 is composed of two copies of non-covalently linked positive single-stranded RNA enclosed by a conical capsid comprising the viral protein p24, typical of lentiviruses (Figure 1).

Fig. 1. Diagram of HIV

 

Lysine tRNA is the primer of the magnesium dependent reverse transcriptase. It packages two copies of its positive strand, unspliced, 5’guanosine-capped and 3′-polyadenylated RNA genome which is used for strand-transfer-mediated recombination and enables the virus to rapidly evolve under stress or pressure from the environment. The RNA component is 9749 nucleotides long.  This genome bears a 5’ cap (Gppp), a 3’ poly(A)tail, and many open reading frames (ORFs). Viral structural proteins are encoded by long ORFs, whereas smaller ORFs encode regulators of the viral life cycle: attachment, membrane fusion, replication, and assembly. This is in turn surrounded by an envelope of host-cell origin. The single-strand RNA is tightly bound to the nucleocapsid proteins, p6, p7 and enzymes essential to the development of the virion, such as reverse transcriptase and integrase. The nucleocapsid (p7 and p6) associates with the genomic RNA (one molecule per hexamer) and protects the RNA from digestion by nucleases. A matrix composed of an association of the viral protein p17 surrounds the capsid, ensuring the integrity of the virion particle. Also enclosed within the virion particle are Vif, Vpr, Nef, p7 and viral protease. The envelope is formed when the capsid buds from the host cell, taking some of the host-cell membrane with it. The envelope includes the glycoproteins gp120 and gp41.

As a result of its role in virus-cell attachment, the structure of the virus envelope spike, consisting of gp120 and gp41, is of particular importance. It is hoped that determining the envelope spike’s structure will contribute to scientific understanding of the virus and its replication cycle, and help in the creation of a cure. The first model of its structure was compiled in 2006 using cryo-electron tomography and suggested that each spike consists of a trimer of three gp120–gp41 heterodimers. However, published shortly after was evidence for a single-stalk “mushroom” model, with a head consisting of a trimer gp120s and a gp41 stem, which appears as a compact structure with no obvious separation between the three monomers, anchoring it to the envelope.  There are various possibilities as to the source of this difference, as it is unlikely that the viruses imaged by the two groups were structurally different. More recently, further evidence backing up the heterodimer trimer-based model has been found.

Genome organization

HIV has several major genes coding for structural proteins that are found in all retroviruses as well as several nonstructural (“accessory”) genes unique to HIV. The HIV genome contains three major genes, 5’gag-pol-env-3′, encoding major structural proteins as well as essential enzymes. These are synthesized as polyproteins which produce proteins for virion interior, called Gag, group specific antigen; the viral enzymes (Pol, polymerase) or the glycoproteins of the virion env (envelope). In addition to these, HIV encodes for proteins which have certain regulatory and auxiliary functions as well. HIV-1 has two important regulatory elements: Tat and Rev and few important accessory proteins such as Nef, Vpr, Vif and Vpu which are not essential for replication in certain tissues. The gag gene provides the basic physical infrastructure of the virus, and pol provides the basic mechanism by which retroviruses reproduce, while the others help HIV to enter the host cell and enhance its reproduction. Though they may be altered by mutation, all of these genes except tev exist in all known variants of HIV; see Genetic variability of HIV.

HIV employs a sophisticated system of differential RNA splicing to obtaiine different gene products from a less than 10kb genome. HIV has a 9.2kb unspliced genomic transcript which encodes for gag and pol precursors; a singly spliced, 4.5 kb encoding for env, Vif, Vpr and Vpu and a multiply spliced, 2 kb mRNA encoding for Tat, Rev and Nef.

Viral structural proteins

–         gag (group-specific antigen) codes for the precursor gag polyprotein which is processed by viral protease during maturation to MA (matrix protein, p17); CA (capsid protein, p24); SP1 (spacer peptide 1, p2); NC (nucleocapsid protein, p7); SP2 (spacer peptide 2, p1) and P6 protein.

–         pol codes for viral enzymes reverse transcriptase (RT) and RNase H, integrase (IN), and HIV protease (PR). HIV protease is required to cleave the precursor Gag polyprotein to produce structural proteins, RT is required to transcribe DNA from RNA template, and IN is necessary to integrate the double-stranded viral DNA into the host genome.

–         env (for “envelope”) codes for gp160, which is cleaved by a protease, furin, within the endoplasmic reticulum of the host cell. The post-translational processing produces a surface lipoprotein, gp120 or SU, which attaches to the CD4 receptors present on lymphocytes, and gp41 or TM, which embeds in the viral envelope to enable the virus to attach to and fuse with target cells.

–         tat (HIV trans-activator) plays an important role in regulating the reverse transcription of viral genome RNA ensuring efficient synthesis of viral mRNAs as well as regulating the release of the virions from the infected cells. Tat is expressed as 72-amino acid one-exon Tat as well as the 86-101 amino-acid two-exon Tat playing an important role early in HIV infection.Tat(14-15kDa) binds to the bulged genomic RNA stem-loop secondary structure near the 5′ LTR region forming the Tat Responsive element (TAR)

Essential regulatory elements

rev (regulator of expression of virion proteins): The Rev protein binds to an arginine-rich RNA-binding motif of the viral genome which acts as NLS (nuclear localization signals), required for the transport of Rev to the nucleus from cytosol during viral replication. Rev recognizes a complex stem-loop structure of the mRNA env located in the intron separating coding exon of Tat and Rev which is known as the Rev response element (RRE). Rev is important for the synthesis of major viral proteins and is hence essential for viral replication.

vpr (lentivirus protein R): Vpr is a virion-associated, nucleocytoplasmic shuttling regulatory protein. It is believed to play an important role in replication of the virus, specifically, nuclear import of the preintegration complex. Vpr also appears to cause its host cells to arrest their cell cycle in the G2 phase. This arrest activates the host DNA repair machinery which may enable integration of the viral DNA. HIV-2 and SIV encode an additional Vpr related protein called Vpx which functions in association with Vpr.

Accessory regulatory proteins

vif – Vif is a highly conserved, 23 kDa phosphoprotein important for the infectivity of HIV-1 virions depending on the cell type. HIV-1 has been found to require Vif to synthesize infectious viruses in lymphocytes, macrophages, and certain human cell lines. It does not appear to require Vif for the same process in HeLa cells or COS cells, among others.

nef- Nef, negative factor, is a N-terminal myristoylated membrane-associated phosphoprotein. It is involved in multiple functions during the replication cycle of the virus. It is believed to play an important role in cell apoptosis and increase in virus infectivity.

vpu (Virus protein U) – Vpu is specific to HIV-1. It is a class I oligomeric integral membrane phosphoprotein with numerous biological functions. Vpu is involved in CD4 degradation involving the ubiquitin proteasome pathway as well as in the successful release of virions from infected cells.

tev: This gene is only present in a few HIV-1 isolates. It is a fusion of parts of the tat, env, and rev genes, and codes for a protein with some of the properties of tat, but little or none of the properties of rev.

Tropism

The term viral tropism refers to the cell types a virus infects. HIV can infect a variety of immune cells such as CD4+ T cells, macrophages, and microglial cells. HIV-1 entry to macrophages and CD4+ T cells is mediated through interaction of the virion envelope glycoproteins (gp120) with the CD4 molecule on the target cells and also with chemokine coreceptors.

Macrophage (M-tropic) strains of HIV-1, or non-syncitia-inducing strains (NSI) use the β-chemokine receptor CCR5 for entry and are, thus, able to replicate in macrophages and CD4+ T cells. This CCR5 coreceptor is used by almost all primary HIV-1 isolates regardless of viral genetic subtype. Indeed, macrophages play a key role in several critical aspects of HIV infection. They appear to be the first cells infected by HIV and perhaps the source of HIV production when CD4+ cells become depleted in the patient. Macrophages and microglial cells are the cells infected by HIV in the central nervous system. In tonsils and adenoids of HIV-infected patients, macrophages fuse into multinucleated giant cells that produce huge amounts of virus.

T-tropic isolates, or syncitia-inducing (SI) strains replicate in primary CD4+ T cells as well as in macrophages and use the α-chemokine receptor, CXCR4, for entry. Dual-tropic HIV-1 strains are thought to be transitional strains of HIV-1 and thus are able to use both CCR5 and CXCR4 as co-receptors for viral entry.

The α-chemokine SDF-1, a ligand for CXCR4, suppresses replication of T-tropic HIV-1 isolates. It does this by down-regulating the expression of CXCR4 on the surface of these cells. HIV that use only the CCR5 receptor are termed R5; those that use only CXCR4 are termed X4, and those that use both, X4R5. However, the use of coreceptor alone does not explain viral tropism, as not all R5 viruses are able to use CCR5 on macrophages for a productive infection and HIV can also infect a subtype of myeloid dendritic cells, which probably constitute a reservoir that maintains infection when CD4+ T cell numbers have declined to extremely low levels.

Some people are resistant to certain strains of HIV. For example, people with the CCR5-Δ32 mutation are resistant to infection with R5 virus, as the mutation stops HIV from binding to this coreceptor, reducing its ability to infect target cells.

Sexual intercourse is the major mode of HIV transmission. Both X4 and R5 HIV are present in the seminal fluid, which is passed from a male to his sexual partner. The virions can then infect numerous cellular targets and disseminate into the whole organism. However, a selection process leads to a predominant transmission of the R5 virus through this pathway. How this selective process works is still under investigation, but one model is that spermatozoa may selectively carry R5 HIV as they possess both CCR3 and CCR5 but not CXCR4 on their surface and that genital epithelial cells preferentially sequester X4 virus. In patients infected with subtype B HIV-1, there is often a co-receptor switch in late-stage disease and T-tropic variants appear that can infect a variety of T cells through CXCR4.  These variants then replicate more aggressively with heightened virulence that causes rapid T cell depletion, immune system collapse, and opportunistic infections that mark the advent of AIDS. Thus, during the course of infection, viral adaptation to the use of CXCR4 instead of CCR5 may be a key step in the progression to AIDS. A number of studies with subtype B-infected individuals have determined that between 40 and 50 percent of AIDS patients can harbour viruses of the SI and, it is presumed, the X4 phenotypes.

HIV-2 is much less pathogenic than HIV-1 and is restricted in its worldwide distribution. The adoption of “accessory genes” by HIV-2 and its more promiscuous pattern of coreceptor usage (including CD4-independence) may assist the virus in its adaptation to avoid innate restriction factors present in host cells. Adaptation to use normal cellular machinery to enable transmission and productive infection has also aided the establishment of HIV-2 replication in humans. A survival strategy for any infectious agent is not to kill its host but ultimately become a commensal organism. Having achieved a low pathogenicity, over time, variants more successful at transmission will be selected.

Fig. 2. HIV Mature and Immature.

 

Replication cycle

Entry to the cell

HIV enters macrophages and CD4+ T cells by the adsorption of glycoproteins on its surface to receptors on the target cell followed by fusion of the viral envelope with the cell membrane and the release of the HIV capsid into the cell.

Entry to the cell begins through interaction of the trimeric envelope complex (gp160 spike) and both CD4 and a chemokine receptor (generally either CCR5 or CXCR4, but others are known to interact) on the cell surface. gp120 binds to integrin α4β7 activating LFA-1 the central integrin involved in the establishment of virological synapses, which facilitate efficient cell-to-cell spreading of HIV-1. The gp160 spike contains binding domains for both CD4 and chemokine receptors.

The first step in fusion involves the high-affinity attachment of the CD4 binding domains of gp120 to CD4. Once gp120 is bound with the CD4 protein, the envelope complex undergoes a structural change, exposing the chemokine binding domains of gp120 and allowing them to interact with the target chemokine receptor. This allows for a more stable two-pronged attachment, which allows the N-terminal fusion peptide gp41 to penetrate the cell membrane. Repeat sequences in gp41, HR1, and HR2 then interact, causing the collapse of the extracellular portion of gp41 into a hairpin. This loop structure brings the virus and cell membranes close together, allowing fusion of the membranes and subsequent entry of the viral capsid.

After HIV has bound to the target cell, the HIV RNA and various enzymes, including reverse transcriptase, integrase, ribonuclease, and protease, are injected into the cell. During the microtubule-based transport to the nucleus, the viral single-strand RNA genome is transcribed into double-strand DNA, which is then integrated into a host chromosome.

HIV can infect dendritic cells (DCs) by this CD4-CCR5 route, but another route using mannose-specific C-type lectin receptors such as DC-SIGN can also be used. DCs are one of the first cells encountered by the virus during sexual transmission. They are currently thought to play an important role by transmitting HIV to T-cells when the virus is captured in the mucosa by DCs. The presence of FEZ-1, which occurs naturally ieurons, is believed to prevent the infection of cells by HIV.

Fig. 3. Mechanism of Viral Entry/Membrane Fusion

1.Initial interaction between gp120 and CD4. 2. Conformational change in gp120 allows for secondary interaction with CCR5. 3. The distal tips of gp41 are inserted in to the cellular membrane. 4. gp41 undergoes significant conformational change; folding in half and forming coiled-coils. This process pulls the viral and cellular membranes together, fusing them.

 

Replication and transcription

Shortly after the viral capsid enters the cell, an enzyme called reverse transcriptase liberates the single-stranded (+)RNA genome from the attached viral proteins and copies it into a complementary DNA (cDNA) molecule. The process of reverse transcription is extremely error-prone, and the resulting mutations may cause drug resistance or allow the virus to evade the body’s immune system. The reverse transcriptase also has ribonuclease activity that degrades the viral RNA during the synthesis of cDNA, as well as DNA-dependent DNA polymerase activity that creates a sense DNA from the antisense cDNA. Together, the cDNA and its complement form a double-stranded viral DNA that is then transported into the cell nucleus. The integration of the viral DNA into the host cell’s genome is carried out by another viral enzyme called integrase.

Fig. 4. The HIV replication cycle

 

This integrated viral DNA may then lie dormant, in the latent stage of HIV infection.  To actively produce the virus, certain cellular transcription factors need to be present, the most important of which is NF-κB (NF kappa B), which is upregulated when T-cells become activated. This means that those cells most likely to be killed by HIV are those currently fighting infection.

During viral replication, the integrated DNA provirus is transcribed into mRNA, which is then spliced into smaller pieces. These small pieces are exported from the nucleus into the cytoplasm, where they are translated into the regulatory proteins Tat (which encourages new virus production) and Rev. As the newly produced Rev protein accumulates in the nucleus, it binds to viral mRNAs and allows unspliced RNAs to leave the nucleus, where they are otherwise retained until spliced. At this stage, the structural proteins Gag and Env are produced from the full-length mRNA. The full-length RNA is actually the virus genome; it binds to the Gag protein and is packaged into new virus particles.

HIV-1 and HIV-2 appear to package their RNA differently; HIV-1 will bind to any appropriate RNA, whereas HIV-2 will preferentially bind to the mRNA that was used to create the Gag protein itself. This may mean that HIV-1 is better able to mutate (HIV-1 infection progresses to AIDS faster than HIV-2 infection and is responsible for the majority of global infections).

Recombination

Two RNA genomes are encapsidated in each HIV-1 particle (see Structure and genome of HIV). Upon infection and replication catalyzed by reverse transcriptase, recombination between the two genomes can occur. Recombination occurs as the single-strand (+)RNA genomes are reverse transcribed to form DNA. During reverse transcription the nascent DNA can switch multiple times between the two copies of the viral RNA. This form of recombination is known as copy-choice. Recombination events may occur throughout the genome. From 2 to 20 events per genome may occur at each replication cycle, and these events can rapidly shuffle the genetic information that is transmitted from parental to progeny genomes.

Viral recombination produces genetic variation that likely contributes to the evolution of resistance to anti-retroviral therapy.  Recombination may also contribute, in principle, to overcoming the immune defenses of the host. Yet, for the adaptive advantages of genetic variation to be realized, the two viral genomes packaged in individual infecting virus particles need to have arisen from separate progenitor parental viruses of differing genetic constitution. It is unknown how often such mixed packaging occurs under natural conditions.

Bonhoeffer et al. suggested that template switching by the reverse transcriptase acts as a repair process to deal with breaks in the ssRNA genome. In addition, Hu and Temin suggested that recombination is an adaptation for repair of damage in the RNA genomes. Strand switching (copy-choice recombination) by reverse transcriptase could generate an undamaged copy of genomic DNA from two damaged ssRNA genome copies. This view of the adaptive benefit of recombination in HIV could explain why each HIV particle contains two complete genomes, rather than one. Furthermore, the view that recombination is a repair process implies that the benefit of repair can occur at each replication cycle, and that this benefit can be realized whether or not the two genomes differ genetically. On the view that that recombination in HIV is a repair process, the generation of recombinational variation would be a consequence, but not the cause of, the evolution of template switching.

HIV-1 infection causes chronic ongoing inflammation and production of reactive oxygen species. Thus, the HIV genome may be vulnerable to oxidative damages, including breaks in the single-stranded RNA. For HIV, as well as for viruses generally, successful infection depends on overcoming host defensive strategies that often include production of genome-damaging reactive oxygen. Thus, Michod et al. suggested that recombination by viruses is an adaptation for repair of genome damages, and that recombinational variation is a byproduct that may provide a separate benefit.

Assembly and release

The final step of the viral cycle, assembly of new HIV-1 virions, begins at the plasma membrane of the host cell. The Env polyprotein (gp160) goes through the endoplasmic reticulum and is transported to the Golgi complex where it is cleaved by furin resulting in the two HIV envelope glycoproteins, gp41 and gp120. These are transported to the plasma membrane of the host cell where gp41 anchors gp120 to the membrane of the infected cell. The Gag (p55) and Gag-Pol (p160) polyproteins also associate with the inner surface of the plasma membrane along with the HIV genomic RNA as the forming virion begins to bud from the host cell. The budded virion is still immature as the gag polyproteins still need to be cleaved into the actual matrix, capsid and nucleocapsid proteins. This cleavage is mediated by the also packaged viral protease and can be inhibited by antiretroviral drugs of the protease inhibitor class. The various structural components then assemble to produce a mature HIV virion.  Only mature virions are then able to infect another cell.

Classifications of HIV infection

Two main clinical staging systems are used to classify HIV and HIV-related disease for surveillance purposes: the WHO disease staging system for HIV infection and disease,  and the CDC classification system for HIV infection.  The CDC’s classification system is more frequently adopted in developed countries. Since the WHO’s staging system does not require laboratory tests, it is suited to the resource-restricted conditions encountered in developing countries, where it can also be used to help guide clinical management. Despite their differences, the two systems allow comparison for statistical purposes.

The World Health Organization first proposed a definition for AIDS in 1986. Since then, the WHO classification has been updated and expanded several times, with the most recent version being published in 2007. The WHO system uses the following categories:

Primary HIV infection: May be either asymptomatic or associated with acute retroviral syndrome.

Stage I: HIV infection is asymptomatic with a CD4+ T cell count (also known as CD4 count) greater than 500 per microlitre (µl or cubic mm) of blood.May include generalized lymph node enlargement.

Stage II: Mild symptoms which may include minor mucocutaneous manifestations and recurrent upper respiratory tract infections. A CD4 count of less than 500/µl.

Stage III: Advanced symptoms which may include unexplained chronic diarrhea for longer than a month, severe bacterial infections including tuberculosis of the lung, and a CD4 count of less than 350/µl.

Stage IV or AIDS: severe symptoms which include toxoplasmosis of the brain, candidiasis of the esophagus, trachea, bronchi or lungs and Kaposi’s sarcoma. A CD4 count of less than 200/µl.

The United States Center for Disease Control and Prevention also created a classification system for HIV, and updated it in 2008. This system classifies HIV infections based on CD4 count and clinical symptoms, and describes the infection in three stages:

Stage 1: CD4 count ≥ 500 cells/µl and no AIDS defining conditions

Stage 2: CD4 count 200 to 500 cells/µl and no AIDS defining conditions

Stage 3: CD4 count ≤ 200 cells/µl or AIDS defining conditions

Unknown: if insufficient information is available to make any of the above classifications

For surveillance purposes, the AIDS diagnosis still stands even if, after treatment, the CD4+ T cell count rises to above 200 per µL of blood or other AIDS-defining illnesses are cured.

 

Oral Manifestations of HIV

1.    FUNGAL LESIONS

Candidiasis

Oral candidiasis is most commonly associated with Candida albicans, although other species, such as C. glabrata and C. tropicalis, are frequently part of the normal oral flora. A number of factors predispose patients to develop candidiasis: infancy, old age, antibiotic therapy, steroid and other immunosuppressive drugs, xerostomia, anemia, endocrine disorders, and primary and acquired immunodeficiency. Candidiasis is a common finding in people with HIV infection. Reports describe oral candidiasis during the acute stage of HIV infection,(10) but it occurs most commonly with falling CD4+ T-cell count in middle and late stages of HIV disease. Several reports indicate that most persons with HIV infection carry a single strain of Candida during clinically apparent candidiasis and when candidiasis is quiescent.

Clinical Features

The clinical appearances of oral candidiasis vary. The most common presentations include pseudomembranous and erythematous candidiasis, which are equally predictive of the development of AIDS,  and angular cheilitis. These lesions may be associated with a variety of symptoms, including a burning mouth, problems eating spicy food, and changes in taste (Figure 6 -8). All three of these common forms may appear in one individual.

Fig. 6.  Pseudomembranous Candidiasis

Fig. 7. Pseudomembranous Candidiasis

 

Pseudomembranous Candidiasis (Thrush)

Characteristic creamy white, removable plaques on the oral mucosa are caused by overgrowth of fungal hyphae mixed with desquamated epithelium and inflammatory cells. The mucosa may appear red when the plaque is removed. This type of candidiasis may involve any part of the mouth or pharynx.

Fig. 8. Erythematous Candidiasis

 

Erythematous Candidiasis

Erythematous candidiasis appears as flat, red patches of varying size. It commonly occurs on the palate and the dorsal surface of the tongue. Erythematous candidiasis is frequently subtle in appearance and clinicians may easily overlook lesions, which may persist for several weeks if untreated.

Angular Cheilitis

Angular cheilitis appears clinically as redness, ulceration, and fissuring, either unilaterally or bilaterally at the corners of the mouth. It can appear alone or in conjunction with another form of candidiasis.

Fig. 9. Angular cheilitis and pseudomembranous candidiasis.

 

Hyperplastic Candidiasis

This type of candidiasis is unusual in persons with HIV infection. The lesions appear white and hyperplastic. The white areas are due to hyperkeratosis and, unlike the plaques of pseudomembranous candidiasis, cannot be removed by scraping. These lesions may be confused with hairy leukoplakia. Diagnosis of hyperplastic candidiasis is made from the histologic appearance of hyperkeratosis and the presence of hyphae. Periodic acid-Schiff (PAS) stain is often used to demonstrate hyphae.

Fig. 10. Chronic hyperplastic candidiasis.

 

Differential Diagnosis

Erythematous candidiasis should be differentiated from other red lesions, such as Kaposi’s sarcoma or erythroplakia. Histologically, oral candidiasis contains Candida hyphae in the superficial epithelium when viewed under a PAS stain. The inflammatory responses often associated with Candida infection may be absent in immunocompromised patients. The creamy white plaques of pseudomembranous candidiasis are removable; the white lesions of hairy leukoplakia are nonremovable.

Diagnosis

Candida is a commensal organism in the oral cavity. Candidiasis is diagnosed by its clinical appearance and by detection of organisms on smears. Smears taken from clinical lesions are examined using potassium hydroxide (KOH), PAS, or Gram’s stain. Smears are taken by gently drawing a wooden tongue depressor across the lesion. The specimen is then transferred into a drop of KOH on a glass slide and protected by a cover slip. The smear is examined under the microscope and Candida is detected by finding hyphae and blastospores. Hyphae and spores are only seen in smears from lesions and are rarely seen in the healthy individual in the carrier state. Cultures are grown on specific media, such as Sabouraud’s agar; they may be positive and yet reveal very low colony counts. This probably represents a carrier state rather than active infection.  Culture is useful for establishing the Candida species but may not be useful for diagnosis.

Treatment

Oral candidiasis may be treated either topically or systemically. Treatment should be maintained for 7 days. Response to treatment is often good; oral lesions and symptoms may disappear in a fairly short period (ranging from 2 to 5 days), but relapses are common because of the underlying immunodeficiency. As with other causes of oral candidiasis, recurrences are common if the underlying problem persists.

Topical Treatment

Topical treatments are preferred because they limit systemic absorption, but the effectiveness depends entirely on patient compliance. Topical medications require that the patient hold medications in the mouth for 20 to 30 minutes. If the patient uses formulations containing sweetening agents for long periods, consider as concurrent treatment daily fluoride rinses (e.g., ACT or Fluorigard, available as over-the-counter preparations) for 1 minute once a day and then expectorated.

Clotrimazole is an effective topical treatment (one oral troche [10-mg tablet]) when dissolved in the mouth five times daily. Used less frequently, one vaginal troche can be dissolved in the mouth daily. Nystatin preparations include a suspension, a vaginal tablet, and an oral pastille. Regimens are nystatin vaginal tablets (one tablet, 100,000 units, dissolved in the mouth three times a day), or nystatin oral pastille (available as a 200,000-unit oral pastille, one or two pastilles dissolved slowly in the mouth five times a day). Nystatin suspension has a high sugar content and cannot be held in the mouth long enough to be effective. Topical creams and ointments containing nystatin, ketoconazole, or clotrimazole may be useful in treating angular cheilitis. Another therapeutic choice is amphotericin B (0.1 mg/ml). Five to 10 ml of oral solution is used as a rinse and then expectorated three to four times daily.

Systemic Treatment

Several agents are effective for systemic treatment. Ketoconazole (Nizoral) is a 200-mg tablet taken with food once daily. Patient compliance is usually good. Careful monitoring of liver function is necessary for long-term use because of reported side effects, including hepatotoxicity. Lack of efficacy of ketoconazole may occur because of poor absorption in those with an abnormally high gastric pH.

Fluconazole (Diflucan) is a triazole antifungal agent effective in treating candidiasis (100-mg tablet taken once daily for 2 weeks).  Several studies suggest fluconazole is effective as a prophylactic agent, although the most effective prophylaxis dosing regimen is still unclear. Numerous reports, however, describe oral and esophageal candidiasis failing to respond to treatment with fluconazole, and in some of these cases investigators isolated resistant strains. Itraconazole (100-mg capsules) may be used for the treatment of oral candidiasis (200 mg daily orally for 14 days).  Itraconazole oral suspension is now available (200 mg daily for 2 weeks. Salivary levels of itraconazole are maintained for several hours after administration.

Ketoconazole, fluconazole, and itraconazole may interact with other medications including rifampicin, phenytoin, cyclosporin A, terfenadine, digoxin, coumarin-like medications, and oral hypoglycemic medications.

Prognostic Significance

Both erythematous and pseudomembranous oral candidiasis are associated with increased risk for the subsequent development of opportunistic infections classifying the patient as having AIDS as defined by the Centers for Disease Control (CDC).Several studies have shown a statistical correlation between frequency of oral candidiasis in HIV infection and falling CD4+ T-cell counts.

 

2.    VIRAL LESIONS

Herpes Simplex

Herpes simplex causes both primary and secondary or recurrent disease in the oral cavity. Primary herpetic gingivostomatitis commonly occurs in children and young adults and may be followed by frequent recurrences. Following the primary episode, the virus becomes latent in the trigeminal ganglion. Recurrent oral herpes occurs at any age extraorally or intraorally.

Clinical Features

Recurrent herpes labialis occurs on the vermilion border of the lips. The patient may report a history of itching or pain, followed by the appearance of small vesicles. These rupture and form crusts. Recurrent intraoral herpes appears as clusters of painful small vesicles that rupture and ulcerate and usually heal within 1 week to 10 days. The lesions usually occur on the keratinized mucosa, such as the hard palate and gingiva, although lesions may arise on the dorsal surface of the tongue.

Fig. 11. Herpes simplex lesion

Fig. 12. Herpes simplex on the patients lips.

Differential Diagnosis

Rising antibody titers from initial and convalescent sera confirm primary herpetic gingivostomatitis. Examining smears of lesions (treated with Papanicolaou stain) for multinucleated giant cells confirms recurrent herpes. It is possible to demonstrate herpes simplex type 1 or type 2 by applying monoclonal antibodies to smears from the lesions (the Syva Kit, Syva Corporation, Palo Alto, CA). Swabs taken from fluid-filled vesicles may grow herpes simplex in culture if vesicles are a few days or less old. Clinicians can distinguish between recurrent intraoral herpes simplex lesions, which always occur on keratinized mucosa (such as the hard palate and gingiva), and recurrent aphthous ulcers, which always appear oonkeratinized mucosa. Recurrent intraoral herpes may appear more frequently in HIV-infected patients. The lesions may be painful and slow to heal.

Treatment

No treatment will permanently eradicate oral herpes simplex infections, but acyclovir may shorten the healing time for individual episodes. The optimum oral dosage of acyclovir is 1,000 to 1600 mg daily for 7 to 10 days. Topical acyclovir is not useful for treating intraoral lesions and may not be effective for lesions on the lips. Recurrent outbreaks of acyclovir-resistant herpes have been reported, including a case involving the facial skin, lips, nose, and mouth. In this case, the lesions resolved after treatment with foscarnet Phosphonoformate may also prove effective.

Prognostic Significance

There is no known association between recurrent intraoral herpes and more rapid progression of HIV disease. However, there is a clinical impression that recurrent herpes simplex infections may be more common in patients with symptomatic HIV disease.

Herpes Zoster

The reactivation of varicella zoster virus (VZV) causes herpes zoster (shingles). The disease occurs in the elderly and the immunosuppressed.

Clinical Features

Oral herpes zoster generally causes skin lesions. Following a prodrome of pain, multiple vesicles appear on the facial skin, lips, and oral mucosa. Skin and oral lesions are frequently unilateral and follow the distribution of the maxillary and/or mandibular branches of the trigeminal nerve. The skin lesions form crusts and the oral lesions coalesce to form large ulcers. The ulcers frequently affect the gingiva, so tooth pain may be an early complaint.

Fig. 13. Herpes zoster

Fig. 14. Herpes zoster in mouth.

Differential Diagnosis

The appearance of the lesions and their distribution are pathognomonic.

Treatment

Acyclovir limits the duration of the lesions. For herpes zoster, the standard oral dosage is 800 mg five daily for 7 to 10 days, which is considerably higher than that recommended for treatment of herpes simplex.

Human Papillomavirus Lesions

Oral warts, papillomas, skin warts, and genital warts are associated with the human papillomavirus (HPV). Lesions caused by HPV are common on the skin and mucous membranes of persons with HIV disease. Anal warts have frequently been reported among homosexual men. Because the HPV types found in oral lesions in HIV-infected persons are different from the HPV types associated with anogenital warts, clinicians should probably not use the term condyloma acuminata to describe oral HPV lesions.

Clinical Features

HPV lesions in the oral cavity may appear as solitary or multiple nodules. They may be sessile or pedunculated and appear as multiple, smooth-surfaced raised masses resembling focal epithelial hyperplasia or as multiple, small papilliferous or cauliflower-like projections (Figure 3). I have identified HPV types 7, 13, and 32 in some of these oral warts.(26) Malignant transformation of HPV oral lesions has not been reported, but the identification of four new HPV types in these lesions warrants further study.

Fig. 15. HPV in mouth.

Differential Diagnosis

A biopsy is necessary for histologic diagnosis.

Prognosis

There is no known association between oral HPV lesions and more rapid progression of HIV disease, but oral warts are seen more commonly in HIV-infected persons than in the general population.

Treatment

Oral HPV lesions can be removed surgically using local anesthetic. Carbon dioxide laser surgery can remove multiple flat warts, but relapses occur and several repeat procedures may be necessary.

Cytomegalovirus

Oral ulcers caused by cytomegalovirus (CMV) have been reported. These ulcers can appear on any mucosal surface and may be confused with aphthous ulcers, necrotizing ulcerative periodontitis (NUP), and lymphoma. Unlike aphthous ulcers, however, which usually have an erythematous margin, CMV ulcers appear necrotic with a white halo. Diagnosis of CMV ulcers is made from a biopsy. Immunohistochemistry may be helpful.

CMV ulcers in the oral cavity usually occur in individuals with disseminated CMV disease. Therefore, diagnosis of CMV-infected oral ulcers should be followed by examination for the systemic disease. CMV ulcers resolve when ganciclovir is used to treat CMV disease.

Hairy Leukoplakia and Epstein-Barr Virus

Oral hairy leukoplakia (HL), which presents as a nonmovable, corrugated or “hairy” white lesion on the lateral margins of the tongue, occurs in all risk groups for HIV infections, although less commonly in children than in adults. HL occurs in about 20% of persons with asymptomatic HIV infection and becomes more common as the CD4+ T-cell count falls. HL is in group 4, category C2 of the original Centers for Disease Control (CDC) definition of AIDS and in B3 of the 1993 criteria.No report describes HL in mucosal sites other than the mouth. HL has occurred ion-HIV-infected people including recipients of bone marrow, cardiac, and renal transplants.

Fig. 16. Oral hairy leukoplakia

Hairy Leukoplakia and Progression of HIV Disease

Diagnosis of HL is an indication of both HIV infection and immunodeficiency; it is an indication for a work-up to evaluate and treat HIV disease. HL correlates with a statistical risk for more rapid progression of HIV disease. In an early study, 30% of persons with HL progressed to late-stage HIV disease characterized by CDC-defined AIDS within 36 months. In a later study, 47% of a group developed CDC-defined AIDS within 2 years and 67% within four years. Those persons with HL who progressed to CDC-defined AIDS most rapidly, however, were more often anergic to Candida antigen at diagnosis of HL, indicating significant immunosuppression at that time. Progression to CDC-defined AIDS was more rapid in those HIV-infected persons with HL than in those without HL, even after adjustment for CD4+ T-cell count.

Pathogenesis

The Epstein-Barr virus (EBV) in HL is both unusual in that deletions in the EBNA 2 gene have been described  and in that to date no viral DNA is found in the basal layers of HIV. Intraepithelial Langerhans’ cells (LCs) are reduced or absent in the HL lesion, which correlates with the presence of viral antigens. It is not known whether the lack of LCs is a cause of HL or a consequence of EBV infection.

In electron microscopic specimens, investigators have found structures consistent with a herpes group virus. One structure consisted of 100-nm intranuclear virions and 240-nm encapsulated virus particles. Other structures are 48- to 52-nm particles visible in the suprabasal layer.  Closer to specimen surfaces, where the nuclei are more condensed, arrays of these particles and herpes group particles occurred in the same cell. Several studies described the appearance of these particles in HL biopsies.

Clinical Appearance and Manifestations

HL lesions vary in size and appearance and may be unilateral or bilateral. The surface is irregular and may have prominent folds or projections, sometimes markedly resembling hairs. Occasionally, however, some areas may be smooth and flat. Lesions occur most commonly on the lateral margins of the tongue and may spread to cover the entire dorsal surface. They may also spread downward onto the ventral surface of the tongue, where they usually appear flat. HL lesions can also occur on the buccal mucosa, generally as flat lesions. Rarely, lesions occur on the soft palate. HL usually does not cause symptoms.

Differential Diagnosis

Candida albicans may be found in association with many HL lesions, and hyphae can be seen in specimens taken from lesions and examined using potassium hydroxide. Hyphae can be seen in sections stained with periodic acid-Schiff. Administration of antifungal drugs may change the appearance of the lesions but does not cause them to disappear. Clinicians must distinguish them from other white lesions, such as lichen planus, idiopathic leukoplakia, white sponge nevus, dysplasia, and squamous cell carcinoma.

Diagnosis

HL should be diagnosed by biopsy for definitive diagnosis. Experienced clinicians can make a presumptive diagnosis of HL in association with HIV disease from the clinical appearance, although HL can be confused with oral candidiasis. The typical microscopic appearance of HL includes acanthosis, marked parakeratosis with the formation of ridges and keratin projections, areas of ballooning cells, and little or no inflammation in the connective tissue. The ballooning changes resemble koilocytosis. Cells are enlarged; some contain enlarged ballooning cells with pyknotic nuclei. Some contain perinuclear haloes.

Definitive diagnosis of HL requires demonstration of EBV. EBV may be readily demonstrated in biopsy specimens by a variety of techniques. Cells taken from the HL lesion by scraping can be used for a noninvasive diagnosis using in situ hybridization.

Treatment

Hairy leukoplakia usually is asymptomatic and does not require treatment. HL is almost always a manifestation of HIV infection, and clinicians should arrange evaluation of HIV disease and appropriate treatment for patients with HL. HL has disappeared in patients receiving high-dose acyclovir for herpes zoster, presumably because of the anti-EBV activity of acyclovir. Doses of acyclovir (2.5 to 3 mg per day for 2 to 3 weeks) usually eliminate HL, but the lesion usually recurs with cessation of treatment.

Elimination or almost complete clinical resolution of the lesion has occurred in patients treated with agents such as desciclovir, an analog of acyclovir, phosphonoformate, Retin A, and podophyllin resin, although lesions tend to recur within a few months. Case reports describe HL disappearing during treatment with ganciclovir, zidovudine, and aerosolized pentamidine.  Katz and colleagues have shown that HL both appears and disappears in patients receiving zidovudine, although no case-controlled studies are available.

Occasionally, Candida albicans may be found in HL lesions. Treatment consists of antifungal medications.

3.    BACTERIAL LESIONS

Periodontal Disease

Periodontal disease is a fairly common problem in both asymptomatic and symptomatic HIV-infected patients. It can take two forms: the rapid and severe condition called necrotizing ulcerative periodontitis (NUP) and its associated and possibly precursor condition called linear gingival erythema (LGE). The presenting clinical features of these diseases often differ from those in non-HIV-infected persons.

Clinical Features

LGE and NUP often occur in clean mouths where there is very little plaque or calculus to account for the gingivitis. The onset is often sudden, with rapid loss of bone and soft tissue. In LGE, the gingiva may be reddened and edematous. Patients sometimes complain of spontaneous bleeding. In acute-onset ulcerative gingivitis, ulcers occur at the tips of the interdental papilla and along the gingival margins, and often elicit complaints of severe pain. The ulcers heal, leaving the gingival papillae with a characteristic cratered appearance.

Fig. 17. Linear  gingival erythema

NUP may present as rapid loss of supporting bone and soft tissue. Typically, these losses occur simultaneously with no formation of gingival pockets, sometimes involving only isolated areas of the mouth. Teeth may loosen and eventually fall out, but uninvolved sites can appear healthy. Necrotizing stomatitis may develop, and areas of necrotic bone may appear along the gingival margin. The bone may eventually sequestrate. Patients with NUP and necrotizing stomatitis frequently complain of extreme pain and spontaneous bleeding.

Fig. 18. Necrotizing ulcerative periodontitis

Differential Diagnosis

The patient’s history and clinical appearance make the diagnosis. It is sometimes difficult to distinguish this type of periodontal disease from non-HIV-related periodontal disease. However, the complaints of severe pain, rapid onset, and rapid destruction in an often extremely clean mouth are unusual for non-HIV-related periodontal disease.

Treatment

Clinicians should refer patients to a periodontist or dentist for management. The following protocol has achieved reasonable success: plaque removal, local debridement, irrigation with povidone-iodine, scaling and root planing, and maintenance with a chlorhexidine mouth rinse (Peridex-R) once or twice daily. Studies show that the addition of chlorhexidine to this regimen produces significant improvement in periodontal condition. In cases of NUP, metronidazole (one 250-mg tablet four times daily), amoxicillin/clavulanate (Augmentin)(one 250-mg tablet three times daily), or clindamycin (one 300-mg tablet three times daily) should be added to the treatment regimen.

Different Course in HIV Infection

The microbiology  of periodontal disease in HIV-infected patients has not been fully described. Oral flora associated with LGE and NUP appear to be similar to those associated with periodontal disease seen ion-HIV-infected persons. Recurrences of acute episodes are common and response to conventional treatment may be poor. However, therapeutic strategies and frequent recall appointments can produce effective local treatment of LGE and NUP. There is as yet no known relationship between these conditions and the progression of HIV disease.

4.    NEOPLASTIC LESIONS

Kaposi’s sarcoma

Kaposi’s sarcoma (KS) may occur intraorally, either alone or in association with skin and disseminated lesions. Intraoral lesions have been reported at other sites and may be the first manifestation of late-stage HIV disease (AIDS). KS occurs most commonly in men but also has been observed in women.

Clinical Features

KS can appear as a red, blue, or purplish lesion. It may be flat or raised, solitary or multiple. The most common oral site is the hard palate, but lesions may occur on any part of the oral mucosa, including the gingiva, soft palate, and buccal mucosa, and in the oropharynx. Occasionally, yellowish mucosa surrounds the KS lesion. Oral KS lesions may enlarge, ulcerate, and become infected. Good oral hygiene is essential to minimize these complications.

Fig. 19. Kaposi’s sarcoma

Fig. 20. Kaposi’s sarcoma

Differential Diagnosis

KS must be distinguished from vascular lesions such as hematomas, hemangiomas, other vascular tumors, pyogenic granulomas, bacillary angiomatosis, and pigmented lesions such as oral melanotic macules. Diagnosis is made from histologic examination. There are usually no bleeding problems associated with a biopsy of oral KS. However, aspiration of a lesion prior to biopsy may be useful to rule out a hemangioma. Small, flat lesions are probably in early stages, and the histologic appearance is different from the larger, nodular lesions that are probably more advanced. Early lesions may be difficult to diagnose histologically because they resemble endothelial proliferation. KS may appear suddenly, within days of a normal oral examination, in previously uninvolved areas of the mouth.

Providers should ensure that a patient with KS receives evaluation and follow-up care for the underlying HIV disease.

Treatment

Treatment is determined on the basis of the number, size, and location of the oral KS lesions. The choice of therapy depends on the effect of treatment on the adjacent mucosa, pain associated with treatment, interference with eating and speaking, and the patient’s preference. It is important to perform thorough dental prophylaxis before initiating therapy for KS lesions involving the gingiva. Response to therapy is improved if all local plaque and calculus are removed. Local application of sclerosing agents may reduce the size of oral lesions.

Local treatment is appropriate for large oral KS lesions that interfere with eating and talking. Oral KS can be treated surgically or with localized intralesional chemotherapy. Surgical removal is suitable for small, well-circumscribed lesions such as gingival or tongue lesions. Surgical removal can be performed under local anesthesia with a blade or with the carbon dioxide laser. Intralesional vinblastine is useful for treating small lesions, particularly on the palate or gingiva. Several studies have documented the effectiveness of one or two injections of 0.1 to 0.2 mg per ml solution of vinblastine. Posttreatment pain is fairly common, but systemic effects are rare. The pain usually disappears several days after therapy.

Radiation therapy may be indicated for large, multiple lesions. A single dose of 800 cGy or an equivalent fractionated dose is frequently used and produces a good response. Side effects include xerostomia and mucositis, although both conditions usually improve with cessation of radiation therapy.

5.    LYMPHOMA

Clinical Features

Diffuse, undifferentiated non-Hodgkin’s lymphoma (NHL) is a frequent HIV-associated malignancy. Most are of B cell origin, and Epstein-Barr virus occurs in cells from several cases. Lymphoma can occur anywhere in the oral cavity, and there may be soft tissue involvement with or without involvement of underlying bone. The lesion may present as firm, painless swelling that may be ulcerated. Some oral lesions may appear as shallow ulcerations.  Oral NHL may appear as solitary lesions with no evidence of disseminated disease.

Differential Diagnosis

Oral NHL may be confused with major aphthous ulcers and rarely as a pericoronitis associated with an erupting third molar. Diagnosis of NHL must be made by histologic examination of biopsy specimens.

Treatment

After diagnosis of the oral lesions, the patient must be referred for further evaluation for disseminated disease and its subsequent treatment.

6.    OTHER ORAL LESIONS ASSOCIATED WITH HIV DISEASE

Oral Ulceration

Oral ulcers resembling recurrent aphthous ulcers (RAUs) in HIV-infected persons are reported with increasing frequency.  The cause of these ulcers is unknown. Proposed causes include stress and unidentified infectious agents. In HIV-infected patients, the ulcers are well circumscribed with erythematous margins. The ulcers of the minor RAU type may appear as solitary lesions of about 0.5 to 1.0 cm. The herpetiform type appear as clusters of small ulcers (1 to 2 mm), usually on the soft palate and oropharynx. The major RAU type appears as extremely large (2 to 4 cm) necrotic ulcers. The major RAUs are very painful and may persist for several weeks.

Diagnosis

The ulcers may present a diagnostic problem. Herpetiform RAUs may resemble the lesions of coxsackievirus infection, and major RAUs may require biopsy to exclude malignancy, such as lymphoma, or opportunistic infection, such as histoplasmosis. The ulcers usually occur on nonkeratinized mucosa; this characteristic differentiates them from those caused by herpes simplex.

Treatment

The RAU type ulcers usually respond well to topical steroids such as fluocinonide (0.05%) ointment mixed with equal parts Orabase applied six times daily or clobetasol (0.05%) ointment mixed with equal parts Orabase applied three times per day. Dexamethasone elixir (0.5 mg/5 ml) used as a mouth rinse and then expectorated two to three times daily is helpful for multiple ulcers and for those where topical ointments are hard to apply. For HIV-infected persons with oral and gastrointestinal aphthous-like ulcers, systemic steroid therapy (prednisone 40 to 60 mg/day for 7 to 10 days) has been reported as helpful. The risks of steroid therapy, however, must be considered before administration to individuals in this population. Thalidomide (50 to 200 mg) has been used in Europe and is the subject of clinical trials in the United States (ACTG 251).

Idiopathic Thrombocytopenic Purpura

Reports have described idiopathic thrombocytopenic purpura (ITP) in HIV-infected patients. Oral lesions may be the first manifestation of this condition.

Clinical Features

Petechiae, ecchymoses, and hematoma can occur anywhere on the oral mucosa. Spontaneous bleeding from the gingiva can occur, and patients may report finding blood in their mouths on waking.

Differential Diagnosis

The clinician must distinguish ITP from other vascular lesions and KS. Because of potential bleeding risk, the clinician should obtain blood and platelet counts before performing other diagnostic procedures.

Salivary Gland Disease and Xerostomia

Salivary gland disease associated with HIV infection (HIV-SGD) can present as xerostomia with or without salivary gland enlargement. Reports describe salivary gland enlargement in children and adults with HIV infection usually involving the parotid gland. The enlarged salivary glands are soft but not fluctuant. In some cases, enlarged salivary glands may be due to lymphoepithelial cysts. Schiodt et al. found that 9 of 12 patients (11 adults and 1 child) with HIV-SGD had salivary gland enlargement. Three had xerostomia. Labial salivary gland biopsy revealed histologic features similar to those in Sjogren’s syndrome. In HIV-SGD, however, the lymphocytic infiltrate is predominantly CD8 cells, unlike that in Sjogren’s syndrome, which is predominantly CD4 cells.

No evidence of Epstein-Barr virus or cytomegalovirus has been found in biopsies of salivary glands. One report describes an association between HIV-SGD and HLA-DR5 and HLA-B35 cell-surface antigen.

The etiology of HIV-SGD is as yet unknown but the enlarged parotid glands can be a source of annoyance and discomfort.

Xerostomia is sometimes seen in individuals with HIV-SGD. HIV-infected patients may also experience dry mouth in association with taking certain medications that can hinder salivary secretion, such as ddI, antidepressants, antihistamines, and antianxiety drugs.

Management

Removal of the enlarged parotid glands is rarely recommended. For individuals with xerostomia, the use of salivary stimulants such as sugarless gum or sugarless candies may provide relief. Candies that are acidic should be avoided as frequent use may lead to loss of tooth enamel. The use of salivary substitutes may also be helpful. An increase in caries can occur, so fluoride rinses (that can be bought over the counter) should be used daily, and visits to the dentist should occur two to three times per year.

Diagnosis of HIV infection

HIV tests are used to detect the presence of the human immunodeficiency virus (HIV), the virus that causes acquired immunodeficiency syndrome (AIDS), in serum, saliva, or urine. Such tests may detect antibodies, antigens, or RNA.

Tests used for the diagnosis of HIV infection in a particular person require a high degree of both sensitivity and specificity. In the United States, this is achieved using an algorithm combining two tests for HIV antibodies. If antibodies are detected by an initial test based on the ELISA method, then a second test using the Western blot procedure determines the size of the antigens in the test kit binding to the antibodies. The combination of these two methods is highly accurate (see below).

Antibody tests

Window period

Antibody tests may give false negative (no antibodies were detected despite the presence of HIV) results during the window period, an interval of three weeks to six months between the time of HIV infection and the production of measurable antibodies to HIV seroconversion. Most people develop detectable antibodies approximately 30 days after infection, although some seroconvert later. The vast majority of people (97%) have detectable antibodies by three months after HIV infection; a six-month window is extremely rare with modern antibody testing. During the window period, an infected person can transmit HIV to others although their HIV infection may not be detectable with an antibody test. Antiretroviral therapy during the window period can delay the formation of antibodies and extend the window period beyond 12 months. This was not the case with patients that underwent treatment with post-exposure prophylaxis (PEP). Those patients must take ELISA tests at various intervals after the usual 28 day course of treatment, sometimes extending outside of the conservative window period of 6 months. Antibody tests may also yield false negative results in patients with X-linked agammaglobulinemia; other diagnostic tests should be used in such patients.

Three instances of delayed HIV seroconversion occurring in health-care workers have been reported; in these instances, the health-care workers  tested negative for HIV antibodies greater than 6 months postexposure but were seropositive within 12 months after the exposure. DNA sequencing confirmed the source of infection in one instance. Two of the delayed seroconversions were associated with simultaneous exposure to hepatitis C virus (HCV). In one case, co-infection was associated with a rapidly fatal HCV disease course; however, it is not known whether HCV directly influences the risk for or course of HIV infection or is a marker for other exposure-related factors.

ELISA

The enzyme-linked immunosorbent assay (ELISA), or enzyme immunoassay (EIA), was the first screening test commonly employed for HIV. It has a high sensitivity.

In an ELISA test, a person’s serum is diluted 400-fold and applied to a plate to which HIV antigens have been attached. If antibodies to HIV are present in the serum, they may bind to these HIV antigens. The plate is then washed to remove all other components of the serum. A specially prepared “secondary antibody” — an antibody that binds to human antibodies — is then applied to the plate, followed by another wash. This secondary antibody is chemically linked in advance to an enzyme. Thus the plate will contain enzyme in proportion to the amount of secondary antibody bound to the plate. A substrate for the enzyme is applied, and catalysis by the enzyme leads to a change in color or fluorescence. ELISA results are reported as a number; the most controversial aspect of this test is determining the “cut-off” point between a positive and negative result.

Western blot

Like the ELISA procedure, the western blot is an antibody detection test. However, unlike the ELISA method, the viral proteins are separated first and immobilized. In subsequent steps, the binding of serum antibodies to specific HIV proteins is visualized.

Specifically, cells that may be HIV-infected are opened and the proteins within are placed into a slab of gel, to which an electrical current is applied. Different proteins will move with different velocities in this field, depending on their size, while their electrical charge is leveled by a surfactant called sodium lauryl sulfate. Some commercially prepared Western blot test kits contain the HIV proteins already on a cellulose acetate strip. Once the proteins are well-separated, they are transferred to a membrane and the procedure continues similar to an ELISA: the person’s diluted serum is applied to the membrane and antibodies in the serum may attach to some of the HIV proteins. Antibodies that do not attach are washed away, and enzyme-linked antibodies with the capability to attach to the person’s antibodies determine to which HIV proteins the person has antibodies.

There are no universal criteria for interpreting the western blot test: The number of viral bands that must be present may vary. If no viral bands are detected, the result is negative. If at least one viral band for each of the GAG, POL, and ENV gene-product groups are present, the result is positive. The three-gene-product approach to western blot interpretation has not been adopted for public health or clinical practice. Tests in which less than the required number of viral bands are detected are reported as indeterminate: a person who has an indeterminate result should be retested, as later tests may be more conclusive. Almost all HIV-infected persons with indeterminate western blot results will develop a positive result when tested in one month; persistently indeterminate results over a period of six months suggests the results are not due to HIV infection. In a generally healthy low-risk population, indeterminate results on western blot occur on the order of 1 in 5,000 patients.:However for those individuals that have had high-risk exposures to individuals where HIV-2 is most prevalent, Western Africa, an inconclusive western blot test may prove infection with HIV-2.

The HIV proteins used in western blotting can be produced by recombinant DNA in a technique called recombinant immunoblot assay (RIBA).

Rapid or point-of-care tests

Rapid antibody tests are qualitative immunoassays intended for use as a point-of-care test to aid in the diagnosis of HIV infection. These tests should be used in conjunction with the clinical status, history, and risk factors of the person being tested. The positive predictive value of Rapid Antibody Tests in low-risk populations has not been evaluated. These tests should be used in appropriate multi-test algorithms designed for statistical validation of rapid HIV test results.

If no antibodies to HIV are detected, this does not mean the person has not been infected with HIV. It may take several months after HIV infection for the antibody response to reach detectable levels, during which time rapid testing for antibodies to HIV will not be indicative of true infection status. For most people, HIV antibodies reach a detectable level after two to six weeks.

Although these tests have high specificity, false positives do occur. Any positive test result should be confirmed by a lab using the western blot.

Fig. 21. A woman demonstrates the use of the OraQuick rapid HIV test.

Interpreting antibody tests

ELISA testing alone cannot be used to diagnose HIV, even if the test suggests a high probability that antibody to HIV-1 is present. In the United States, such ELISA results are not reported as “positive” unless confirmed by a Western Blot.

The ELISA antibody tests were developed to provide a high level of confidence that donated blood was NOT infected with HIV. It is therefore not possible to conclude that blood rejected for transfusion because of a positive ELISA antibody test is in fact infected with HIV. Sometimes, retesting the donor in several months will produce a negative ELISA antibody test. This is why a confirmatory Western Blot is always used before reporting a “positive” HIV test result.

Rare false positive results due to factors unrelated to HIV exposure are found more often with the ELISA test than with the Western Blot. False positives may be associated with medical conditions such as recent acute illnesses and allergies. A rash of false positive tests in the fall of 1991 was initially blamed on the influenza vaccines used during that flu season, but further investigation traced the cross-reactivity to several relatively non-specific test kits. A false positive result does not indicate a condition of significant risk to health. When the ELISA test is combined with Western Blot, the rate of false positives is extremely low, and diagnostic accuracy is very high.

HIV antibody tests are highly sensitive, meaning they react preferentially with HIV antibodies, but not all positive or inconclusive HIV ELISA tests mean the person is infected by HIV. Risk history, and clinical judgement should be included in the assessment, and a confirmation test (Western blot) should be administered. An individual with an inconclusive test should be re-tested at a later date.

 

Other tests used in HIV treatment

The CD4 T-cell count is not an HIV test, but rather a procedure where the number of CD4 T-cells in the blood is determined.

A CD4 count does not check for the presence of HIV. It is used to monitor immune system function in HIV-positive people. Declining CD4 T-cell counts are considered to be a marker of progression of HIV infection. A normal CD4 count can range from 500 cells/mm3 to 1000 cells/mm3. In HIV-positive people, AIDS is officially diagnosed when the count drops below 200 cells/μL or when certain opportunistic infections occur. This use of a CD4 count as an AIDS criterion was introduced in 1992; the value of 200 was chosen because it corresponded with a greatly increased likelihood of opportunistic infection. Lower CD4 counts in people with AIDS are indicators that prophylaxis against certain types of opportunistic infections should be instituted.

Low CD4 T-cell counts are associated with a variety of conditions, including many viral infections, bacterial infections, parasitic infections, sepsis, tuberculosis, coccidioidomycosis, burns, trauma, intravenous injections of foreign proteins, malnutrition, over-exercising, pregnancy, normal daily variation, psychological stress, and social isolation.

This test is also used occasionally to estimate immune system function for people whose CD4 T cells are impaired for reasons other than HIV infection, which include several blood diseases, several genetic disorders, and the side effects of many chemotherapy drugs.

In general, the lower the number of T cells the lower the immune system’s function will be. Normal CD4 counts are between 500 and 1500 CD4+ T cells/microliter, and the counts may fluctuate in healthy people, depending on recent infection status, nutrition, exercise, and other factors. Women tend to have somewhat lower counts than men.

Management

There is currently no cure or effective HIV vaccine. Treatment consists of high active antiretroviral therapy (HAART) which slows progression of the disease  and as of 2010 more than 6.6 million people were taking them in low and middle income countries. Treatment also includes preventive and active treatment of opportunistic infections.

Antiviral therapy

Current HAART options are combinations (or “cocktails”) consisting of at least three medications belonging to at least two types, or “classes,” of antiretroviral agents. Initially treatment is typically a non-nucleoside reverse transcriptase inhibitor (NNRTI) plus two nucleoside analogue reverse transcriptase inhibitors (NRTIs). Typical NRTIs include: zidovudine (AZT) or tenofovir (TDF) and lamivudine (3TC) or emtricitabine (FTC). Combinations of agents which include a protease inhibitors (PI) are used if the above regime loses effectiveness.

When to start antiretroviral therapy is subject to debate. The World Health Organization, European guidelines and the United States recommends antiretrovirals in all adolescents, adults and pregnant women with a CD4 count less than 350/µl or those with symptoms regardless of CD4 count. This is supported by the fact that beginning treatment at this level reduces the risk of death. The United States in addition recommends them for all HIV-infected people regardless of CD4 count or symptoms; however it makes this recommendation with less confidence for those with higher counts.  While the WHO also recommends treatment in those who are co-infected with tuberculosis and those with chronic active hepatitis B. Once treatment is begun it is recommended that it is continued without breaks or “holidays”. Many people are diagnosed only after treatment ideally should have begun. The desired outcome of treatment is a long term plasma HIV-RNA count below 50 copies/mL.  Levels to determine if treatment is effective are initially recommended after four weeks and once levels fall below 50 copies/mL checks every three to six months are typically adequate.  Inadequate control is deemed to be greater than 400 copies/mL.  Based on these criteria treatment is effective in more than 95% of people during the first year.

Benefits of treatment include a decreased risk of progression to AIDS and a decreased risk of death. In the developing world treatment also improves physical and mental health. With treatment there is a 70% reduced risk of acquiring tuberculosis. Additional benefits include a decreased risk of transmission of the disease to sexual partners and a decrease in mother-to-child transmission. The effectiveness of treatment depends to a large part on compliance. Reasons for non-adherence include poor access to medical care, inadequate social supports, mental illness and drug abuse. The complexity of treatment regimens (due to pill numbers and dosing frequency) and adverse effects may reduce adherence. Even though cost is an important issue with some medications, 47% of those who needed them were taking them in low and middle income countries as of 2010  and the rate of adherence is similar in low-income and high-income countries.

Specific adverse events are related to the agent taken. Some relatively common ones include: lipodystrophy syndrome, dyslipidemia, and diabetes mellitus especially with protease inhibitors. Other common symptoms include diarrhea,  and an increased risk of cardiovascular disease. Newer recommended treatments are associated with fewer adverse effects. Certain medications may be associated with birth defects and therefore may be unsuitable for women hoping to have children.

Treatment recommendations for children are slightly different from those for adults. In the developing world, as of 2010, 23% of children who were ieed of treatment had access. Both the World Health Organization and the United States recommend treatment for all children less than twelve months of age. The United States recommends in those between one year and five years of age treatment in those with HIV RNA counts of greater than 100,000 copies/mL, and in those more than five years treatments when CD4 counts are less than 500/µl.

 

References:

1.      Danilevskiy M.F. et al. “ Diseases of the mucous membrane of the mouth.” – K.: “Medytsyna”, 2010.

2.      Bruch J.M. Clinical oral medicine and pathology/ J.M. Bruch, N.S. Treister// London.:Humana Press, 2010

3.      Cawson R. E. Cawson’s essentials of oral pathology and oral medicine. Seventh edition/ Cawson R. E. et. al. //Elsevier science limited, 2002.

4.      Slootweg P. Dental pathology – a practical introduction/ P.J. Slootweg// Berlin.: Springer, 2007.

5.      Da Silva J.D. Oxford American Handbook of Clinical Dentistry (Oxford American Handbooks in Medicine) / J.D. Da Silva et al.// Oxford University Press, 2007.
6. http://hivinsite.ucsf.edu/InSite?page=kb-04-01-14
7. http://en.wikipedia.org/wiki/Structure_and_genome_of_HIV
8. http://en.wikipedia.org/wiki/HIV_test
9. http://en.wikipedia.org/wiki/HIV/AIDS
10. http://en.wikipedia.org/wiki/History_of_HIV/AIDS

 

 

Information was prepared by Sukhovolets I.O.