Immune preparations. Preparation for active immunization – vaccines. Their use, control. Other antigenic preparations. Their practical value.

 

Seroprophylaxias and serotherapy. Immunoglobulins.  Methods of obtaining, practical value. Hybridomas technology.

 

immune status. Immunodeficiency diseases and immune correction. Evaluation of the immune status of the mouth cavity

 

 

VACCCINES. Of the many diseases that plagued societies for centuries, smallpox was among the most serious. Numerous individuals contracted and died of this viral disease Those who survived, however, no longer seemed to be susceptible They had become resistant to infection with the smallpox virus Even without any knowledge of the immune response, some individuals reasoned that it was possible to acquire immunity (resistance to disease). In China, where many herbs and other substances were long used to treat disease, children inhaled dried scabs from smallpox victims to protect them against serious smallpox infections. Those that developed mild cases of smallpox and survived were subsequently resistant (immune) to this disease. This practice was carried out as early as the thirteenth century and, by the early eighteenth century, individuals throughout the Far East were exposing themselves to smallpox viruses to develop immunity.

Edward Jenner

 

 

In Turkey, elderly women collected material from the sores (pustules) of mild cases of smallpox and placed it into a walnut shell. A small amount of the material was then injected into a vein of an individual to protect her or him from smallpox. The injected individual would become ill within a week, developing fever, sores, and pustules. But in another week, the sores and pustules would heal. There generallywas no permanent scarring and after recovery the individual was resistant to smallpox.

This practice of ingrafting was introduced in England in 1718 by Lady Mary Montagu, whose husband had been the British ambassador to Turkey Lady Mary was a striking English beauty until the age of 26 when she contracted smallpox Although she survived, she was permanently scarred and bemoaned that “my beauty is no more ” It was perhaps because of her experience with smallpox that Lady Mary became interested in ingrafting when she was living in Constantinople In a letter to her family she wrote “The Small Pox, so fatal and general amongst us, is here entirely harmless by the invention of ingrafting. When she returned to England, Lady Mary used her considerable influence in the court of King George I to gain publicity for the increased use of ingrafting She even arranged a test of her idea on prisoners and orphans, then a common practice Today such testing of humans is viewed as unethical Despite her efforts, ingrafting was not accepted by the scientists and physicians of the time as a useful practice for preventing disease Too often, ingrafting resulted in scarring and in some cases it produced fatal cases of smallpox.

It was not until a report by Edward Jenner to the Royal Society of London, 80 years after Lady Mary tried to introduce ingrafting in England, that credence was given in Europe to the practice of immunization to protect against smallpox. Jenner was a middle-class country doctor, whose interest in science was typical of his position: scholarly but amateurish.

 

 

Although it is unclear when he began to develop his ideas about vaccination, Jenner apparently did not develop them from the reports of Lady Mary Montagu about ingrafting in Turkey. He clearly knew of the dairy country’s folk belief that cowpox, which is caused by vaccinia virus, protected its victims from subsequent infections of smallpox. In particular, milkmaids were known for their immunity to smallpox. Jenner also knew that BenjaminJesty, a Dorset farmer, had vaccinated his wife and two children with cowpox material taken from a soreon the udder of an infected cow in 1774. Although smallpox was ravaging the population in the vicinity, it did not affect the Jesty family.

Jenner performed his first inoculation in 1796 on a child with material from the cowpox lesions of a dairymaid. Six weeks later, Jenner inoculated the boy with smallpox virus. The boy did not develop small-pox, indicating that he was resistant to the disease. In this way Jenner experimentally demonstrated the validity of his hypothesis that exposure to cowpox viruses made one resistant to infections with smallpox viruses. Jenner continued his experimental studies, inoculating other children with cowpox viruses. Although friends and other physicians advised him against damaging his reputation by publishing results that were at such variance with accepted knowledge, Jenner decided to present his findings to the Royal Academy. His June 1798 report. An Inquiry into  the Causes and Effects of the Variolae Vaccine, describing the value of vaccination with cowpox as a means of protecting against smallpox established the basis for  the immunological prevention of disease. His work  met the criteria of the scientific method: his hypothesis had been experimentally tested by observations of control and experimental groups, and it was also repeatable by others. Immunization had gained scientific credibility; medical practice and the quest to eliminate smallpox had taken a giant step forward. The work begun with Jenner‘s discovery of the effectiveness of vaccination in preventing smallpox culminated in the 1970s with the eradication of smallpox  from the face of the Earth. Today, vaccines are employed for preventing many diseases, such as  tetanus, diphtheria, measles, and so forth. Research continues to develop new vaccines for preventing many other diseases.

 Immunization (vaccination). The usefulness of immunization rests with its ability to render individuals resistant to a disease without actually producing the disease. This is accomplished by exposing the individual to antigens associated with a pathogen in a form that does not cause disease. This medical process of intentional exposure to antigens is called immunization or vaccination. Implementation of immunization programs has drastically reduced the incidence of several diseases and has greatly increased life expectancies. Many once widespread deadly diseases such as whooping cough and diphtheria are rare today because of immunization programs.

Scientific Basis of Immunization. There are several scientific principles underlying the use of immunization to prevent individuals from contracting specific diseases and for preventing epidemic outbreaks of diseases:

1. Any macromolecule associated with a pathogen can be an antigen—an antigen is not the entire pathogen. Hence, one can use specific target antigens associated with pathogens to elicit the immune response without causing disease.

2. After exposure to an antigen the body may develop an anamnestic (memory) response.  Subsequent exposure to the same antigen can then bring about a rapid and enhanced immune response that can prevent replication of the infecting microorganism and/or the effects of toxins it produces so that disease does not oc– cur In this manner, intentional exposure to an antigen through vaccination can establish an anamnestic response that renders the individual resistant to disease

3. When a sufficiently high proportion of a population is immune to a disease, epidemics do not occur. This is because individuals who are immune are no longer susceptible and thus no longer participate m the chain of disease transmission. When approximately 70% of a population is immune, the entire population generally is protected, a concept known as herd immunity.

 

Herd immunity can be established by artificially stimulating the immune response system through the use of vaccines, rendering more individuals insusceptible to a particular disease and thereby protecting the entire population.

Vaccines. Vaccines are preparations of antigens whose administration artificially establishes a state of immunity without causing disease. Vaccines are designed to stimulate the normal primary immune response. This results in a proliferation of memory cells and the ability to exhibit a secondary memory or anamnestic response on subsequent exposure to the same antigens. The antigens within the vaccine need not be associated with active virulent pathogens. The antigens in the vaccine need only elicit an immune response with the production of antibodies or cytokines. Antibodies and/or cytokine-producing T cells possess the ability to react with the critical antigens associated with the pathogens against which the vaccine is designed to confer protection.

Thus, vaccines are preparations of antigens that stimulate the primary immune response, producing memory cells and the ability to exhibit an anamnestic response to a subsequent exposure to the same antigens without causing disease.

Vaccines may contain antigens prepared by killing or inactivating pathogenic microorganisms; vaccines also may use attenuated or weakened strains that are unable to cause the onset of severe disease symptoms (Table 1).

Comparison of Attenuated and Inactivated Vaccines

FACTOR	ATTENUATED/LIVE	INACTIVATED/ NONLIVING
Rout of administration	Natural route, e.g., orally	Injection
Doses	Single	Multiple
Adjuvant	Not required	Usually needed
Duration of immunity	Years to life	Months to years
Immune response	IgG, IgA, IgM, cell mediated	IgG, little or no cell mediated

 

Some of the vaccines that are useful in preventing diseases caused by various microorganisms are listed in Table 2. Most vaccines are administered to children (Table 3), some are administered to adults (Table 4), and some are used for special purposes. Travellers receive vaccines against pathogens prevalent in the regions they are visiting that do not occur in their home regions (Table 5). In each of these cases the use of the vaccine is prophylactic and aimed at preventing diseases caused by pathogens to which the individual may be exposed.

TABLE 2

Descriptions of Widely Used Vaccines

 

TABLE 3

Recommended Vaccination Schedule for Normal Children

 

 

 

 

TABLE 4

Recommended Vaccination Schedule for Adults

 

Although vaccines are normally administered before exposure to antigens associated with pathogenic microorganisms, some vaccines are administered after suspected exposure to a given infectious microorganism. In these cases the purpose of vaccination is to elicit an immune response before the onset of disease symptoms. For example, tetanus vaccine is administered after puncture wounds may have introduced Clostridium tetani into deep tissues, and rabies vaccine is administered after animal bites may have introduced rabies virus. The effectiveness of vaccines administered after the introduction of the pathogenic microorganisms depends on the relatively slow development of the infecting pathogen before the onset of disease symptoms. It also depends on the ability of the vaccine to initiate antibody production before active toxins are produced and released to the site where they can cause serious disease symptoms.

TABLE 5

Recommended Vaccinations for Travellers

 

Attenuated Vaccines. Some vaccines consist of living strains of microorganisms that do not cause disease. Such strains of pathogens are said to be attenuated because they have weakened virulence (smallpox, anthrax, rabies, tuberculosis, plague, brucellosis, tularaemia, yellow fever, influenza, typhus fever, poliomyelitis, parotitis, measles, etc.). Pathogens can be attenuated, that is, changed into nondisease-causing strains, by various procedures, including moderate use of heat, chemicals, desiccation, and growth in tissues other than the normal host. Vaccines containing viable attenuated strains require relatively low amounts of the antigens because the microorganism is able to replicate after administration of the vaccine, resulting in a large increase in the amount of antigen available within the host to trigger the immune response mechanism. The principle disadvantage of living attenuated vaccines is the possible reversion to virulence through mutation or recombination. Also, even strains may cause disease in individuals who lack adequate immune responses, such as those with AIDS.

 

Figure 2.  Attenuated vaccines can be produced by multiple passage through animal cell tissue culture. Poliovirus for the oral vaccine was developed by passage through monkey kidney cells. Following clinical trials the use of the vaccine greatly reduced the incidence of polio in the United States. Elsewhere, where the vaccine is not used, the incidence of polio remains high.

 

The Sabin polio vaccine, for example, uses viable polioviruses attenuated by growth in tissue culture. Three antigenically distinguishable strains of polioviruses are used m the Sabin vaccine.

The Sabin polio vaccine, for example, uses viable polioviruses attenuated by growth in tissue culture. Three antigenically distinguishable strains of polioviruses are used m the Sabin vaccine.

 These viruses are capable of multiplication within the digestive tract and salivary glands but are unable to invade nerve tissues and thus do not produce the symptoms of the disease polio The vaccines for measles, mumps, rubella, and yellow fever similarly use viable but attenuated viral strains. Attenuated strains of rabies viruses can be prepared by desiccating the virus after growth m the central nervous system tissues of a rabbit or following growth m a chick or duck embryo.

The BCG (bacille Calmette-Guerm) vaccine is an example of an attenuated bacterial vaccine. This vaccine is administered in Britain to children 10 to 14 years old to protect against tuberculosis. It is used in the United States only for high-risk individuals This mycobactenal strain was developed from a case of bovine tuberculosis. It was cultured for over 10 years in the laboratory on a medium containing glycerol, bile, and potatoes. During that time it accumulated mutations so that it no longer was a virulent pathogen. In over 70 years of laboratory culture the BCG mycobacterial strain has not reverted to a virulent form.

Louis Pasteur furthered the development of vaccines when in 1880 he reported that attenuated microorganisms could be used to develop vaccines against chicken cholera. The production of these vaccine depended on prolonging the time between transfers of the cultures. This fact was accidentally discovered through an error by Charles Chamberland, who used an old culture during one of the experiments he was conducting with Pasteur. The old culture contained attenuated microorganisms, that is, weakened or altered microorganisms that were less virulent. Following his work on chicken cholera, Pasteur directed his attention to the study of anthrax. Because he enjoyed being the center of attention and controversy, Pasteur staged a dramatic public demonstration to test the effectiveness of his anthrax vaccine. Witnesses were amazed to see that the 24 sheep, 1 goat, and 6 cows that had received the attenuated vaccine were in good health, whereas all of the animals in this experiment feat had not been vaccinated were dead of anthrax.

In 1885, Pasteur announced to the French Academy of Sciences that he had developed a vaccine for preventing another dread disease, rabies (see Figure). Although he did not understand the nature of the causative organism, Pasteur developed a vaccine that worked. Pasteur’s motto was “Seek the microbe”, but the microorganism responsible for rabies is a virus, which could not be seen under the microscopes of the 1880s. Pasteur, none the less, was able to weaken the rabies virus by drying the spinal cords of infected rabbits and allowing oxygen to penetrate the cords. Thirteen inoculation of  successively more virulent pieces of rabbit spinal cord were injected over a period of 2 weeks during the summer of 1885 into Joseph Meister, a 9-year-old boy who had been bitten by a rabid dog.

“Since the death of the child was almost certain, I decided in spite of my deep concern to try on Joseph Meister the method which had served me so well with dogs… I  decided to give a total of 13 inoculations in 10 days. Fewer inoculations would have been sufficient, but one will understand that I was extremely cautious in, this first case. Joseph Meister escaped not only the rabies that he might have received from his bites, but also the rabies which I inoculated into him”.

 

 

 

The development of the rabies vaccine crowned Pasteur’s distinguished career.

Killed / lnactivated Vaccines. Some vaccines are prepared by killing or inactivating microorganisms so they cannot reproduce or replicate within the body and are not capable of causing disease (enteric fever, paratyphoid, cholera, whooping cough, poliomyelitis and leptospirosis vaccines, etc.).. When microorganisms are killed  or inactivated by treatment with chemicals, radiation, or heat, the antigenic properties of the pathogen are retained. Killed/inactivated vaccines generally can be used without the risk of causing the onset of the disease associated with the virulent live pathogens. The vaccines used for the prevention of whooping cough (pertussis) and influenza are representative of the preparations containing antigens that are prepared by inactivating pathogenic microorganisms.

Even when the vaccines are killed cells, problems can occur in some cases. A small percentage of children, for example, have allergic-type reactions to the pertussis component of the standard DPT (diphtheria-pertussis-tetanus) vaccine Some people are now questioning the wisdom of government-mandated administration of this vaccine. Most manufacturers of this vaccine ceased its production rather than face liability lawsuits associated with such reactions. The supply of DPT vaccine is currently dangerously short. Enhanced quality control programs by the major remaining producer and the development of a new form of the vaccine promise to reduce the incidence of adverse reactions.

There have been several problems with inadequate inactivation of vaccines, leading to disease out-breaks when the vaccines were administered In 1976 there was a scare about an impending outbreak of swine flu Some people given swine flu vaccine actually contracted flu because of the inadequate inactivation of the viruses in hastily prepared vaccines. Others developed a neurological disorder called Guillain-Barre syndrome after vaccination against swine flu In the 1950s several tragic cases of polio oc– curred in children given the Salk polio vaccine, an inactivated vaccine prepared from a very virulent strain of poliovirus. This incident occurred because of the failure to fully inactivate some batches of the vaccine prepared by treatment of polioviruses with formaldehyde Because the Slake vaccine is prepared from a particularly virulent strain of poliovirus, replication of the virus in individuals inoculated with the improperly prepared vaccines caused paralytic polio.

The failure of the quality control program for the Slake vaccine, in part, led to the general switch to the “live” attenuated Sanin polio vaccine. The Sanin vaccine is prepared with attenuated viral strains. These strains are not particularly virulent and do not invade the nervous system, causing paralysis. The Sanin vaccine is administered orally and the virus multiplies within the gastrointestinal tract. Although the virus is attenuated, mutations and recombinations are still possible during replication. Some recent cases of polio have been reported with the Sanin vaccine, causing the reevaluation of the relative merits of the Salk versus the Sabin vaccine.

In some cases the toxins responsible for a disease are inactivated and used for vaccination. Some vaccines, for example, are prepared by denaturing microbial exotoxins. The denatured proteins produced are called toxoids. Protein exotoxins, such as those involved in the diseases tetanus and diphtheria, are suitable for toxoid preparation. The vaccines for preventing these diseases employ toxins inactivated by treatment with formaldehyde. These toxoids retain  the antigenicity of the protein molecules. This means that the toxoids elicit the formation of antibody and are reactive with antibody molecules but, because the proteins are denatured, they are unable to initiate the reactions associated with the active toxins that cause disease.

Individual Microbiological Components (chemical vacccines). Individual components of microorganisms can be used as antigens for immunization. For example, the polysaccharide capsule from Streptococcus pneumoniae is used to make a vaccine against pneumococcus pneumonia. This vaccine is used in high-risk patients, particularly individuals over 50 years old who have chronic diseases, such as emphysema. Another vaccine has been produced from the capsular polysaccharide of Haemophilus influenzae type b, a bacterium that frequently causes meningitis in children 2 to 5 years old. The Hib vaccine, as it is called, is being widely administered to children in the United States. This vaccine is not always effective in establishing protection in children under 2 years old. It is administered to children between 18 and 24 months old who attend day care centres because they have a greater risk of contracting H. influenzae infections.

A polyvaccine against typhoid fever and tetanus is now manufactured and used. It consists of O- and Vi-antigens of the typhoid fever bacteria and purified concentrated tetanus anatoxin. The bacterial antigens and the tetanus anatoxin are adsorbed on aluminium hydroxide.

The first vaccine to provide active immunization against hepatitis B (Heptavax-B) was prepared from hepatitis B surface antigen (HBsAg). This antigen was purified from the serum of patients with chrome hepatitis B. Immunization with Heptavax-B is about 85% to 95% effective in preventing hepatitis B infection. It was administered predominantly to individuals in high-risk categories such as health care workers. It has been replaced by a newer recombinant vaccine, Recombivax HB. To produce Recombivax HB, a part of the hepatitis B virus gene that codes for HBsAg was cloned into yeast. The vaccine is derived from HBsAg that has been produced in yeast cells by recombinant DNA technology,                 

Attempts were made to make a vaccine against gonorrhea using pili from Neissena gonorrhoeae, the bacterium that causes this disease. The vaccine produced, however, was not successful because longlasting immunity against N. gonorrhoeae does not develop. The military, though, has used this vaccine to achieve short-term immunity. Synthetic proteins are also being considered as potential antigens for protection against various diseases.

Thus Individual components of a microorganism can be used in a vaccine to elicit an immune response.

Besides the above mentioned preparations associated vaccines are used for specific prophylaxis of infectious diseases: whooping cough-diphtheria-tetanus vaccine, diphtheria-tetanus associated  anatoxin, whooping cough-diphtheria.

Methods of preparing other associated vaccines are being devised which will provide for the production of antibacterial, antitoxic and antivirus immunity.

Idiotypes. Because of the high degree of variability in the aminoterminal regions of heavy and light chains of an Ab, the Ab combining site and adjacent variable regions often are unique to that Ab (or at least found infrequently in other Abs). Such V region associated structures are called idiotypes. It may help to think of idiotypes as being analogous to fingerprint patterns—few of either are the same.

The idiotype on Ab from one individual can be seen as foreign by another individual of the same species who has not, or cannot, form the same structure on his or her own Abs. If it is seen as foreign, this second individual can make an Ab that binds to the idiotype structure on the Ab from the first individual. The Ab made in the second individual is called an anti idiotype Ab.

Many different ammo acid sequence and structural combinations can form an Ab to a single site on an Ag. Each of these combinations results in a unique Ab binding site, and each unique Ab binding site can give rise to a unique idiotype. Thus, an Ab response to a single site on an Ag can give rise to many different Abs with many different binding sites and, thus, many different idiotypes. Although Abs can see the same site on an Ag in a variety of ways, there are limits to the variability that will allow the binding to occur. Therefore, among those Abs that do bind, some similarity in binding sites and, as a result, some similarity in idiotypes might be expected. These similar, or shared, idiotypes are called public idiotypes.

There also are idiotypes that are unique to a single Ab. These are called private idiotypes. For example, an Ab response to site 1 on an Ag molecule contains Abs with 10 different combining sites. Seven of the 10 binding sites, although different, are similar enough that antiidiotype Ab made to one reacts with all 7. These 7 Abs share a public idiotype. The other 3 Abs also are similar to each other, but are different from the first 7 Abs. These 3 Abs share an idiotype (public idiotype number 2) that is different from the idiotype (public idiotype number 1) shared by the other 7 Abs.

In addition, 1 or more (and perhaps each) of the 10 Abs can have a second V-region-associated structure that is not shared with any of the other 9 Abs. This would be a private idiotype

This lengthy explanation of allotypes and idiotypes is given because both are used as genetic markers in human genetic studies and as markers of variable and constant region genes in studies of regulation of immune responses. In addition, an understanding of the nature of idiotypes is required to appreciate how they can complicate efforts to use monoclonal Abs to suppress transplant rejection and to kill malignant lymphoid cells.

The antiidiotipic antibodies are “mirror reflection” of antigens and thus can induce antibodies formation an cytotoxic cells which interact with antigens. There are many experimental vaccines against different bacteria, viral, protozoan diseases. But interest to antiidiotipic vaccines are decreased, because it is difficult to receive necessary titre of  specific antibodies which caeutralize causing agents and durable immunity against them. Besides that  antiidiotipic vaccine cause allergic reactions.

 

Monoclonal Antibodies. Most proteins possess many different antigenic determinants. As a result, serum from an animal or human producing Abs to a protein or cellular constituent contains a complex mixture of Abs. This mixture contains Abs to all determinants as well as Abs that are heterogeneous with respect to heavy chain isotype, light chain type, allotype, variable region sequence, and idiotype. A long held dream of biomedical scientists was to isolate a single Ab producing cell and grow it in vitro to provide a source of homogenous Abs that  would bind to only a single antigenic determinant.

 

 

 

FIGURE . Production or hybridoma cell lines secreting monoclonal antibodies .The procedure for producing monoclonal antibodies is shown. Activated B cells from an immunized individual (eg, spleen cells from an immunized mouse) are fused with malignant plasma cells isolated from plasmacytomas and adapted to tissue culture. The myeloma cell has a mutant gene that renders it sensitive to the drug aminopterin. The activated B cells, although resistant to aminopterin, have a limited lifetime in culture  and die naturally. The B cell—myeloma cell hybrid is resistant to aminopterin because the B cell provides the missing genes. Therefore, the B cell-myeloma cell hybrid (the hybridoma) is the only fusion product that can survive in the hypoxanthine, aminopterin, thymidine (HAT) selective culture medium used. The hybrids are distributed into many culture wells in the multiwell culture plates and are allowed to grow for a short period. The culture supernatant or these wells then is tested for the desired antibody. Those cultures that are positive are cloned, and the hybridoma cell producing the desired antibody is propagated and used as a source of the monoclonal antibody.

 

Unfortunately, normal Ab-producing cells do not grow indefinitely in tissue culture. In 1975, Georges Kohler and Cesar Milstein overcame this difficulty by fusing normal cells producing the desired Ab from an immunized animal  with myeloma cells (malignant lymphocytes that can be propagated easily in vitro) in the presence of a chemical that promotes cell fusion (polyethylene glycol or Sendai virus). This caused the cell membranes of some Ab producing spleen cells to fuse with the myeloma cells. Such fused cells, called hybridomas, have the Ab producing capability of the normal cell parent and the in vitro growth properties of the malignant myeloma parent. The normal, nonfused spleen cells cannot survive in culture, whereas the unfused myeloma cells, which can grow in vitro, carry a mutant gene in a critical biosynthetic pathway (ie, a drug marker). The presence of this mutant gene allows the unfused myeloma cell to be killed by adding the appropriate drug in culture. The fused cell is protected from this drug, because the normal spleen cell provides the normal biosynthetic gene. The procedure used to produce hybndoma cell lines secreting monoclonal Abs is shown in Figure.

Monoclonal Abs are available for thousands of different determinants and are being used widely as research tools to study protein structure and virus and toxieutralization, and to isolate specific proteins from complex mixtures. Moreover, many commercially available monoclonal Abs are being used in extremely sensitive and specific techniques for the diagnosis of various diseases and, as mentioned earlier, for the experimental treatment of several human diseases.

SYNTHETIC VACCINES. Another approach to the study of Ag structure has been to synthesize peptides with exactly the same sequence as portions of the Ag of interest and to determine whether Ab made to the intact protein will react with these peptides. Similarly, such peptides have been conjugated to a carrier protein (as described earlier for haptens) and used to induce Abs to the peptide Frequently, these latter Abs have been found to react with the native protein molecule as well.

This has led to attempts to predict which ammo acids are involved in the formation of an antigenic determinant. For example, it is known that epitopes recognized by Ab are located on the surface of the Ag molecule. Therefore, it one could predict which segments of the linear sequence exist sequentially on the surface, one could possibly synthesize a peptide with that sequence and use it to induce Ab that would react with the native molecule. Such studies have been conducted, and the results generally bear out the predictions of the ammo acids that contribute to the structure of an antigenic determinant. Other algorithms for predicting antigenic structure have been suggested, but no single one is universally applicable. Much of the problem lies in determining which peptides will invoke an immune response that will neutralize a virus or promote removal and destruction of the bacterium causing the disease Nevertheless, such studies have led to multiple attempts to produce synthetic Ags that could be used to immunize individuals against disease caused by bacteria or viruses. For example, synthetic vaccines have been used experimentally to immunize against diseases such as hepatitis and hoof and mouth disease.

Vector Vaccines. The antigenic structure of most antigens of clinical interest has not been determined, either because we do not have the monoclonal antibodies necessary or because our knowledge of the three dimensional structure is limited or lacking. However, recombinant DNA technology has allowed us to infer the amino acid sequence of several viral proteins from their DNA coding sequences.

This knowledge of the primary structure of viral proteins, combined with the algorithms for predicting antigenicity, may enable us to produce synthetic vaccines in situations in which the production of safe, effective vaccines by current methods is not yet possible.

Recombinant DNA technology is being used to create vaccines containing the genes for the surface antigens for various pathogens. Such vector vaccines act as carriers for antigens associated with pathogens other than the one from which the vaccine was derived. The attenuated virus used to eliminate smallpox is a likely vector for simultaneously introducing multiple antigens associated with different pathogens, such as the chicken pox virus. Several prototype vaccines using the smallpox vaccine as a vector have been made (FIG.).

 

Figure 4. New vaccines can be formed by using recombinant DNA technology to form vector vaccines, for example, using vaccinia virus as a carrier.

 

Other methods for producing novel vaccines also have been developed. For example, a recombinant vaccnia virus that contains a gene for the immunogenic glycoprotein of rabies virus has been made. This recombinant virus expresses the rabies glycoprotein on its viral envelope in addition to its own  glycoprotein. Immunization of experimental animals with this recombinant virus has led to complete protection against disease following intracerebral injection of rabies virus.

About 1 millioew cases of polio are reported annually, most in undeveloped countries. With the use of Ab resistant mutants of the poliovirus, several ammo acids that constitute epitopes on this virus have been identified Karen Burke and her colleagues in England have used recombinant DNA techniques to construct a hybrid virus containing the epitopes of the three serotypes of poliovirus. Experimental animals immunized with this hybrid vaccine have been shown to produce Ab reactive with all three serotypes. Similar methods can be used to produce improved vaccines against many picornaviruses, including hepatitis A.

More recently, the gene encoding pl20, the surface glycoprotein of the human immunodeficiency virus, has been cloned, and the protein has been expressed in insect cells. The use of this recombinant protein as a vaccine for acquired immunodeficiency syndrome is undergoing clinical trials.

 

Booster Vaccines. Multiple exposures to antigens are sometimes needed to ensure the establishment and continuance of a memory response. Several administrations of the Sabin vaccine are needed during childhood to establish immunity against poliomyelitis. A second vaccination is necessary to ensure immunity against measles. Only a single vaccination, though, is needed to establish permanent immunity against mumps and rubella.

In some cases, vaccines must be administered every few years to maintain the anamnestic response capability. Periodic booster vaccinations are necessary, for example, to maintain immunity against tetanus. A booster vaccine for tetanus is recommended every 10 years.

 

 

Adjuvant. Some chemicals, known as adjuvants, greatly enhance the antigenicity of other chemicals (FIG. ). The inclusion of adjuvants in vaccines therefore can greatly increase the effectiveness of the vaccine. When protein antigens are mixed with aluminum compounds, for example, a precipitate is  formed that is more useful for establishing immunity than the proteins alone. Alum-precipitated antigens are released slowly in the human body, enhancing stimulation of the immune response. The use of adjuvants can eliminate the need for repeated booster doses of the antigen, which increases the intracellular exposure to antigens to establish immunity. It also permits the use of smaller doses of the antigen in the vaccine.

 

Figure 5. Adjuvants enhance antigenicity and can greatly improve the effectiveness of a vaccine.

 

Some bacterial cells are effective adjuvants. The killed cells of Bordetella pertussis, used in the DPT vaccine, are adjuvants for the tetanus and diphtheria toxoids used in this vaccine. Similarly, mycobacteria are effective adjuvants. Freund’s adjuvant, which consists of mycobacteria emulsified in oil and water, is especially effective in enhancing cell-mediated immune responses. This adjuvant, however, can induce issue damage and is not used for that reason.

Chemical adjuvants are used in vaccines to increase the antigenicity of other chemical components and hence the effectiveness of the vaccine. They can eliminate the need for booster doses of the antigen.

 

 

 

Routes of Vaccination. The effectiveness of vaccines depends on how they are introduced into the body. Antigens in a vaccine may be given via a number of routes: intradermally (into the skin), subcutaneously (under the skin), intramuscularly (into a muscle), intravenously (into the bloodstream), and into the mucosal cells lining the respiratory tract through inhalation, or orally into the gastrointestinal tracts. Killed / inactivated vaccines normally must be injected into the body, whereas attenuated vaccines often can be administered orally or via inhalation. The effectiveness of a given vaccine depends in part on the normal route of entry for the particular pathogen. For example, polioviruses normally enter via the mucosal cells of the upper respiratory or gastrointestinal tracts.

The Sabin polio vaccine, therefore, is administered orally, enabling the attenuated viruses to enter the mucosal cells of the gastrointestinal tract directly. It is likely that vaccines administered in this way stimulate secretory antibodies of the IgA class in addition to other immunoglobulins. Intramuscular administration of vaccines, like the Salk polio vaccine, is more  likely to stimulate IgM and IgG production. IgG is particularly effective in halting the spread of pathogenic microorganisms and toxins produced by such organisms through the circulatory system.

Vaccination is carried out with due account for the epidemic situation and medical  contraindications. The contraindications include acute fevers, recent recovery from an infectious disease, chronic infections (tuberculosis, malaria), valvular diseases of the heart, severe lesions of the internal organs, the second half of pregnancy, the first period of nursing a baby at the breast, allergic conditions (bronchial asthma, hypersensitivity to any foodstuffs), etc.

Vaccines are stored in a dark and dry place at a constant temperature (+2 to +10 °C). The terms of their fitness are indicated on labels and the method of their administration in special instructions enclosed in the boxes with the flasks or ampoules.

Frustrating efforts to find a vaccine for AIDS. It is not always easy to find antigens associated with pathogens that confer long-term active immunity. Desperate efforts are now underway to formulate a vaccine that will prevent AIDS. Years of research, however, have failed to produce vaccines against other sexually transmitted diseases such as syphilis, as well as other prevalent diseases, including malaria and tooth decay.

Producing an AIDS vaccine will be very difficult because of several properties of HIV. Being a virus, it replicates intracellularly and is released by budding. Hence a method will have to be found for preventing the initial adsorption of the virus to host cells or for detecting and eliminating host cells within which the virus is replicated. Also, the DNA made during replication of this retrovirus is incorporated into me host cell  chromosomes. Use of an attenuated HIV that still permits in corporation of DNA into the chromosomes of the host cell could lead to malignancy. To complicate matters, HIV exhibits variable surface antigens so that multiple antigens may have to be employed to ensure that the  body’s immune system recognizes infecting HIV. So far, the most promising approaches are aimed at blocking the sites on the virus that bind to host cell receptors and are involved m entry of HIV into the host cells. Some research groups are targeting tine CD4 binding protein of HIV, others are exploring CD26 as a site for blocking the  ability of me virus to enter and to infect human host cells.

Vaccinotherapy. For treating patients with protracted infectious diseases (furunculosis, chronic gonorrhoea, brucellosis) vaccines prepared from dead microbes and anatoxins are used. The staphylococcal anatoxin, the polyvalent staphylococcal and streptococcal, the gonococcal and antibrucellosis vaccines and the vaccine against disseminated encephalitis and multiple sclerosis produce a good therapeutic effect.

Combined immuno-antibiotic therapy yields favourable results in typhoid fever, dysentery, brucellosis, ornithosis, and actinomycosis. In some cases autovaccines are used which are prepared from microbes isolated from patients.

Pyrogenal, a preparation from Gram-negative bacteria, is recommended as non-specific therapy in inflammatory processes of the eyes and female genitalia, in syphilis of the nervous system, progressive paralysis, eczema, chronic streptoderma, mycoses, different forms of tuberculosis and in many other diseases for increasing the reactivity of the patient and for activation of the functions of organs and systems of the macro-organism.

The mechanism of its action comprises an increase in the permeability of the capillary walls and the main substance of the connective tissue, a stimulation of the function of the hypophyso-adrenal system, an increase in the protein synthesis in the body, an inhibition of the processes of formation of fibroblasts from young cells of the connective tissue, and a decrease in the development of scar tissue.

Artificial passive immunity. Passive immunity can be used to prevent diseases when there is not sufficient time to develop an acquired immune response through vaccination. The administration of sera, pooled gamma globulin that contains various antibodies, specific immunoglobulins, or specific antitoxins provides immediate protection (Table 6).

Table 6

Substances Used for Passive Immunization

 

Sera are injected in definite doses intramuscularly, subcutaneously, sometimes intravenously, with strict observation of all the rules of asepsis. A preliminary desensitization according to Bezredka’s method is necessary. Sera are employed for treatment and for prophylaxis of tetanus, gas gangrene and  botulism. The earlier the serum is injected, the more marked is its therapeutic and prophylactic action. The length of protective action of sera (passive immunity) is from 8 to 14 days.

At present many institutes of vaccines and sera in the Soviet Union produce therapeutic and prophylactic sera in a purified state. They are treated by precipitating globulins with ammonium sulphate, by fractionation, by the method of ultracentrifugation, electrophoresis and enzymatic hydrolysis which allow the removal of up to 80 per cent of unrequired proteins. These sera have the best therapeutic and prophylactic properties, contain the least amount of unrequired proteins, and have a less distinct toxic and allergic action.

Sera thus produced are subdivided into antitoxic and antimicrobial sera. Antitoxic sera include antidiphtheritic, antitetanic sera and sera effective against botulism, anaerobic infections, and snake bites.

Antimicrobial sera are used against anthrax, encephalitis and influenza in the form of globulins and gamma globulins.

Before the development of antibiotics, passive immunization – often using horse sera – was widely practiced. Unfortunately, precipitation from extensive antigen-antibody complex formation caused kidney damage when horse sera was routinely administered. Today the use of passive  immunity to treat disease is limited to cases of immunodeficiencies and to specific reactions to block the adverse effects of pathogens and toxins.

Various antitoxins (antibodies that neutralize toxins) can be used to prevent toxins of microbial or other origin from causing disease symptoms. The administration of antitoxins establishes passive atificial immunity. Antitoxins are used to neutralize the toxins in snake venom, saving the victims of snake bites. The toxins in poisonous mushrooms can also be neutralized by administration of appropriate anti-toxins. The administration of antitoxins and immunoglobulins to prevent disease occurs after exposure to a toxin and/or an infectious microorganism.

Antitoxins are antibodies that neutralize toxins and can be used to prevent toxins from causing disease symptoms.

It is also possible to establish passive immunity by the administration of gamma globulin, which contains mainly IgG and some IgM and IgA This is a widely used treatment in Africa for many diseases. It is important that the gamma globulin used for establishing passive immunity is pooled in order to combine the immune functions from many people. Passive immunity lasts for a limited period of time because IgG molecules have a finite lifetime in the body. The administration of IgG does not establish an anamnestic response capability. The administration of IgG is also particularly useful therapeutically in preventing disease in persons with immunodeficiencies and other high-risk individuals.

 

AUTOIMMUNITY. In some individuals the immune response fails to recognize self-antigens. In such cases the immune system attacks one’s own body, a condition known as autoimmunity. The inability to recognize self-antigens results in reactions that kill some of one’s own cells. There are a number of autoimmune diseases that result from the failure of the immune response to recognize self antigens. Such autoimmune diseases often result in the progressive degeneration of tissues.

 

 

 

 

 

 

 

Some autoimmune diseases affect single sites within the body. Graves disease, for example, is an autoimmune disease that affects the thyroid. In Graves disease the body produces an antibody that reacts with the receptor for thyroid stimulating hormone. In contrast, some autoimmune diseases affect sites throughout the body. In systemic lupus erythematosus, numerous autoantibodies are produced that react with self-antigens They attack blood cells and cells at multiple body sites Antigen-antibody complexes circulate and settle in the glomeruli of the kidney In cases of myasthenia gravis, antibodies react with nerve-muscle junctions In autoimmune haemolytic anaemia, antibodies react with red blood cells, causing anaemia. Immunosuppressive substances are available to prevent the self-destruction of body tissues by the body’s own immune response.

Various other disease conditions reflect the failure of the immune system to recognize self-antigens. These self-antigens are similar to antigens associated with pathogenic microorganisms. For example, rheumatic fever is an autoimmune disease that results following an infection with group A streptococci (Streptococcus pyogenes) (FIG.). Some antibodies made in response to group A streptococcal antigens can also react with myosin of the heart muscle tissue. After a strep throat, therefore, antibodies made against the group A streptococci cross react with myosin in some individuals, causing tissue damage to the heart. These individuals develop rheumatic fever. Damaged heart valves may cause heart failure years later. The immune complexes between antibody and myosin or related antigens may also cause arthritis and kidney failure.

 

FIG. An autoimmune response can occur following an infection with Streptococcus pyogenes The normal immune response produces antibodies against streptococcal antigens. However, these anti-streptococcal antibodies can cross-react with heart tissue and cause damage that may result in later heart failure

Rheumatoid arthritis is a commonly occuring disease. Although rheumatoid arthritis is usually associated with older people, it often develops early in life. It is a chronic inflammation of the joints, especially the hands and feet It can lead to crippling disabilities. This form of arthritis often begins with a joint inflammation from an infection that causes phagocytic cells to release lysozymes. These degradative enzymes attack and alter certain antigens. B cells make IgM antibodies in response to the antigens and cause more inflammation in the joints.

Treatment of rheumatoid arthritis is designed to relieve the symptoms. There is no cure. Hydrocortisone lessens inflammation and reduces joint damage. Aspirin is also used because hydrocortisone produces side effects. Aspirin also reduces inflammation and pain.

Myasthenia gravis (MG) is an autoimmune disease that affects the neuromuscular system. It is characterized by weakness and rapid fatigue of the skeletal muscles. It affects muscles in the limbs and the muscles used in eye movement, speech, and swallowing. Patients with MG have a high incidence of thyroid abnormality, reduced levels of complement, and antiskeletal muscle antibody. This disease is rare. It affects 3 persons in every 100/000. Twice as many women as men are affected. The disease usually appears in late childhood to middle age.

Normal muscle contraction requires that pores in the membranes of neurons that stimulate muscles be open. It appears that antibodies that react with self-antigens may be blocking these pores in people with miasthenia gravis. When the pores are blocked, the neurons do not release acetylcholine. Acetylcholine initiates muscle cell contraction. Myasthenia gravis is treated with drugs that inhibit the enzyme that freaks down acetylcholine. The slowing of acetylcholine breakdown allows each muscle longer time to act. This compensates for the decreased amount of acetylcholine.

 

 

 

 

 

Systemic lupus erythematosus is a widely disseminated, systemic autoimmune disease. Erythematose means red and lupus means wolf. The name of the disease comes from a butterfly-shaped rash that appears on the nose and cheeks. It was thought that the rash looked like a wolf bite. This disease occurs four times as often in women as in men, usually during the reproductive years. Patients have reduced complement levels and high levels of immune complexes in their serum and glomeruli.

In this disease autoantibodies are made primarily against components of chromatin (DNA, RNA, and proteins). Immune complexes are deposited between the dermis and epidermis and in blood vessels, joints, glomeruli of the kidneys, and central nervous system. They cause inflammation and interfere with normal functions wherever they are. The symptoms depend on where the antigen-antibody complexes most interfere with function. Usually there is inflammation of the blood vessels, heart valves, and joints. A skin rash appears. Many victims die from kidney failure as glomeruli fail to remove wastes from the blood.

 

Patients with Graves disease, which include former President and Mrs. George Bush, suffer from overproduction of hormones produced by the thyroid. Normally the pituitary secretes thyroid-stimulating hormone, which controls the amount of thyroid hormone released. Antibodies to thyroid-stimulating hormone receptors are produced in Graves disease patients. These antibodies trigger thyroid cells to produce the hormones. The antibodies are not subject to hormonal feedback control and so the thyroid continues to produce, and overproduce, hormones. Treatment of this disease involves destruction of part of the thyroid. This is often accomplished using the radioisotope ⁿ¹!, which is concentrated in the thyroid gland and subsequently kills thyroid cells.

 

 

 

Multiple sclerosis (MS) occurs in people 20 to 50 years of age. Common signs are sensory and visual motor dysfunction. The etiology of this disease is unknown. It is generally believed, however, that MS is a T-cell-mediated autoimmune disease. Macroscopic lesions called plaques are found in the central nervous systems of MS patients. The lesions contain macrophages and lymphocytes. The term multiple sclerosis was originally used to describe the wide distribution of these lesions. There is also breakdown in the myelin sheath that surrounds nervous tissue.

 

 

 

 

 

Indication for an assessment of immune status.

Detailed examination of the human health.

Genetic defects of the immune system (primary immunodeficiency).

Acute and chronic bacterial, viral and protozoan disease (hepatitis, sepsis, chronic pneumonia, leishmaniasis, AIDS etc.).

Autoimmune diseases (rheumatism, rheumatoid arthritis, systemic lupus erythematous, etc).

Dermatoveneral diseases (contact dermatitis, pemphigus, mycosis fungoides, syphilis, etc.).

Tuberculosis and leprosy.

Allergic diseases (bronchial asthma, atopy, etc.).

Primary diseases (multiple sclerosis, etc.).

Malignant tumours (leukosis, lymphogranulomatosis, lymphosarcoma etc.).

Normal graviditas,  pathological pregnancy (toxicosis,  Rh-incompatibility, repeated abortions, etc.).

Psychical diseases (narcomania, schizophrenia, etc.).

Starvation.

Examination of the patients in gerontological and endocrinological hospitals.

The control of cytostatic , immunosuppressive and immunostimulation  therapy.

Examination of the recipients before and after transplantations.

Evaluation of immune system state in patients before difficult planed operations.

Scientific and  practical examinations (studying of new types of action, physiotherapy, influences of new types of narcosis and new types of drugs, etc.).

During prophylactic medical examination (the tests of the first level).

 

 

 

The first level tests for assessment of immune status (approximate):

1. Determination of total quantity of lymphocytes in periferal blood (absolute and relative);

2. Determination of Т– and B–lymphocytes in peripheral blood;

3. Determination of the concentration of the main classes of immunoglobulins;

4. Determination of phagocitic activity of leukocytes.

 

The second level tests for assessment of immune status (analytical):

1. Determination of subpopulations of T lymphocytes (CD4⁺ and CD8⁺);

2. Leukocyte migration inhibition test;

3. Examination of proliferative ability of T– and B–lymphocytes (lymphocyte blast transformation test);

4. Determination of specific IgE;

5. Cutaneous tests of hypersensitivity;

6. Determination of circulating immune complexes;

7. Determination of B-lymphocytes which carry superficial immunoglobulins of different classes;

8. Assessment of immunoglobulins synthesis in B-lymphocytes  culture;

9. Assessment of activity of K–cells and NK–cells;

10. Examination of the components of the complement system;

11. Assessment of different stages of phagocytosis;

12. Assessment of different mediators and interleukin-producing activity of the cells.

Table

Some indexes of human immune state

 

 

IMMUNODEFICIENCIES. Failures of the immune response can compromise the ability of the human body to resist infection. Such failures may be due to an inadequate or an inappropriate immune response. If an individual has an inadequate immune response (immunodeficiency), he or she will not be protected against many infectious diseases. Individuals with immunodeficiencies are subject to numerous infections with opportunistic pathogens (Table). Immunodeficiencies may be congenital, that is, the result of an inherited genetic abnormality or acquired from external causes at some time during the life of the individual.

Table 2

Common Infections in Immunocompromised Individuals

 

 

severe combined immunodeficiency. The most devastating type of congenital immunodeficiency is severe combined immunodeficiency (SCID). Individuals with severe combined deficiency have neither functional B nor T lymphocytes.  Such individuals are incapable of any immunological response. Any exposure of such individuals to microorganisms can result in the unchecked growth of the microorganisms within the body. This results in certain death. Individuals suffering from severe combined deficiency can be kept alive m sterile environments. They must be protected from any exposure to microorganisms. In a well-publicized case, a boy named David was kept alive in a sterile bubble chamber for 14 years. Everything entering the chamber—air, water, food—was sterilized. As long as he was not exposed to microorganisms, he was able to survive. Tragically, he died as a result of an attempt to cure his immunodeficiency. He was given a  marrow graft from a sibling with compatible bone marrow in an attempt to establish functional lymphocytes in his body. He developed an adverse reaction that proved fatal. In other cases, such bone marrow transplants have been effective, including some performed within weeks of the unsuccessful treatment of David.

A new treatment for some cases of SCID is the administration of the enzyme adenosine deaminase (ADA) Accumulation of adenosine compounds is toxic to lymphocytes and ADA is needed to prevent toxicity. In the absence of ADA, B and T lymphocytes die. Approximately 35% of the cases of SCID are due to ADA deficiency. Administering ADA can be therapeutic as long as it is not detected as a foreign antigen. To block its recognition as an antigen that would trigger an adverse immune reaction, the ADA is chemically linked to polyethylene glycol (PEG). PEG coats the ADA and blocks its recognition as an antigen. PEG-ADA treatment is being used effectively to treat some cases of SCID.

The inability to produce ADA in an individual with SCID is due to a defective gene. Gene therapy is also being tried in an attempt to cure this condition (FIG. 1). Cells can be obtained from a patient and a functional gene for ADA production inserted into the cells by genetic engineering. The recombinant cells can then be introduced into the patient. Early clinical trials have shown significant improvements in the immune responses of children treated with this gene therapy.                                 

DiGEORGE syndrome. DiGeorge syndrome results from a failure of the thymus to develop correctly. It is probably caused by as abnormal fetal development that interferes with the proper formation of the thymus.

 

 

 

T lymphocytes in individuals with this disease do not become properly differentiated. Signs and symptoms of this disease often are apparent at birth. They include deformities such as low-set ears, fish-shaped mouth, undersized jaw, and wide-set eyes Elevated serum phosphate and low serum calcium also are characteristic of DiGeorge syndrome.

 

 

A low phosphate diet and calcium supplements are used to achieve acceptable levels of phosphate and calcium in the blood. Individuals suffering from this condition do not exhibit cell-mediated immunity. Therefore they are prone to viral and other intracellular infections. Avoidance of infecting agents is important in the management of patients with DiGeorge syndrome.

 

 

 

PEG-ADA gene therapy can be used in the treatment of SCID

 

Bruton congenital agammaglobulinemia. Bruton congenital agam-maglobulmemia results in the failure of B cells to differentiate and produce antibodies Individuals with Bruton disease have a normal cell-mediated res-ponse. This immunodefi-ciency disease affects only males Boys with Bruton agammaglobulmemia are particularly subject to bacterial infections, inclu-ding those by pyrogenic (fever-inducing) bacteria such as Staphylococcus aureus, Streptococcus pyogenes, S pneumoniae, Neisseria meningitidis, and Haemophilus influenzae.

The treatment of this disease involves the repeated administration of pooled gamma globulin to maintain adequate levels of antibody in the circulatory system.

 

Late-onset hypogammaglobulinemia. The most common form of immunodeficiency is known as late-onset hypogammaglobulinemia. In this condition, there is a deficiency of circulating B cells and or B cells with IgG surface receptors. Such individuals are unable to respond adequately to antigen through the normal differentiation of B cell into antibody-secreting plasma cells. Other immunodefficiencies may affect the synthesis of specific class of antibodies For example, some individuals exhibit IgA deficiencies, producing depressed levels of IgA antibodies. Such individuals are prone to infections of the respiratory tract and body surfaces normally protected by mucosal cells that secrete IgA.

complement AND cellular deficiencies. Immunodeficiencies may also affect the complement system. People who fail to produce sufficient amounts of a specific type of complement, called C3 complement, are unable to respond properly to bacterial infections. The lack of an active complement system limits the inflammatory response and the killing of pathogenic bacteria.

 

 

Immunodeficiencies may also result from inadequate functioning of monocytes, neutrophils, and macrophages. Phagocytic cells lacking enzymes that produce hydrogen peroxide and other antimicrobial forms of oxygen do not have proper lysosomal functions that kill bacteria. Pathogenic bacteria are able to multiply within such metabolically deficient phagocytes. Antibiotics can be used to protect individuals who are deficient in both complement and active phagocytic cells against invading pathogenic bacteria.

malignant cell development.  The development of malignant (cancer) cells can also  be viewed as a failure of the immune response. In this case the failure to recognize and to respond properly to inappropriate cells within the body allows malignant cells to proliferate in an uncontrolled manner. Kaposi sarcoma develops in many individuals with AIDS because the failing immune response is unable to prevent malignancies.

acquired immunodeficiency syndrome (AIDS).   Acquired immunodeficiency syndrome or AIDS is caused by an infection with the human immunodeficiency virus (HIV). This virus is able to adsorb specifically to lymphocytes through the CD4 surface receptor. Most of the lymphocytes with the CD4 molecule are th cells. HIV enters the th cell via CD26. Replication of HIV within th cells leads to death of some of the infected cells, lowering numbers of T helper cells. Nearly all the th cells in blood, lymph nodes, and spleen are destroyed. In addition, macrophages and microglial cells in the brain may become infected with HIV, causing dementia. Individuals with AIDS are subject to infection by a wide variety of disease-causing microorganisms and to the development of a form of cancer known as Kaposi sarcoma.

As the th cells are killed, the ratio of th to Ts cells decreases, from about 2.0 to less than 0.5. This is because the th cells decline from over 100,000/mL in healthy individuals to less than 50,000 /ml as a consequence of HIV infection. Because individuals with  AIDS have more T suppressor than Th cells, the immune response does not work efficiently. This preponderance of T suppressor cells depresses other immune functions. Wheumbers of Th cells are decreased, B cells are not stimulated to produce sufficient numbers of antibodies to combat infections. Amounts of lymphokines produced are insufficient to activate macrophages and cytotoxic T cells. Infected th cells release soluble suppressor factor, which inhibits certain immune responses. The T helper cells that survive do not have surface receptors for antigens. They are incapable of recognizing antigens. Thus the first step in the immune response is blocked.

Because HIV reduces the effectiveness of the immune system, the body is unable to rid itself of HIV once the infection is established. The key to controlling this disease rests with prevention. HIV is transmitted by direct sexual contact, by exchange of blood, and from mother to fetus. Casual contact does not result in transmission of the virus. Sexually promiscuous individuals and intravenous drug abusers who share contaminated needles are at high risk of contracting this disease. Steps have been taken to protect the blood supply used for transfusions. Blood is routinely tested for the presence of HIV. Tissues for transplantation are also tested. Health care workers must take special precautions to avoid infection due to exposure to HIV-containing blood. Health care workers with AIDS have a special obligation to ensure that they do not transmit HIV to their patients.

Some drugs have proven effective in prolonging the life expectancies of AIDS patients by retarding the replication of HIV. These drugs interfere with the replication of HIV. HIV is a retrovirus. Retroviruses carry out reverse transcription during replication; they copy their RNA into DNA using a viral enzyme called reverse transcriptase. Azidothymidine (AZT) has been approved for treatment of AIDS. At least 40 % of individuals treated with AZT develop intolerance and must cease taking the drug. Another drug dideoxyinosine (ddl), may be used as an alternate to AZT. Both AZT and ddl block the formation of functional DNA during reverse transcription. AZT and ddl do not eliminate HIV. They only slow down the rate of HIV replication and resultant destruction of T cells.                                        

There currently is no cure for AIDS. There is no vaccine for its prevention. Reducing the likelihood of exposure, such as by using condoms, is necessary to limit the spread of this disease. As the disease progresses the immune system becomes less and less capable of defending the body against infection. Eventually the disease is fatal.

gene therapy with tumor infiltrating lymphocytes. The cellular immune defense system recognizes abnormal cells when they arise in the body. It attempts to eliminate such cells. In this manner the immune system is able to hold in check most malignant (cancer-forming) cells when they occur. T cells detect abnormal antigens on the surfaces of malignant cells and attack those cells. Sometimes the cellular immune response is adequate and malignant tumours do not develop. In other cases the proliferation of malignant cells leads to the growth of cancerous tumours.

Recognizing that T cells have the capacity to attack malignant cells in the body, Stephen Rosenberg and colleagues at the National Institutes of Health postulated that they could develop a method for cancer treatment based on the body’s own immune response. They sought to isolate T cells that could recognize specific types of malignancies. They then developed methods for culturing this specialized class of T  ells, which they called tumour infiltrating lymphocytes (TIL-cells). They hypothesized that if they could culture large numbers of TIL cells from a patient and could reinject the cultured TIL cells into that same patient, those TIL cells would then attack the developing malignant tumours The patient would be receiving ha or her own genetically modified cells.

In a number of cases where they earned out this procedure, there was remarkable regression of the tumours. Some patients responded dramatically and the cancer went into total remission In other cases, however, the procedure failed to check tile growth of the tumours and the patients died of cancer.

It was not clear why the treatment worked in some cases and failed in others. Did the injected TIL cells survive in the body? Did they reach the sites of tumours? Would the injection of lymphokins, such as interleukin, enhance the abilities of TIL cells to destroy malignant tumours? To answer these questions Rosenberg needed a method for tracking fee fate of the TIL cells that he had cultured and introduced back into the patient’s body Rosenberg, with Michael Blaise and French Anderson, proposed to genetically label the TIL cells. They obtained the gene for tagging the TIL cells from a bacterium. It is a gene that codes far neomycin resistance. This gene does not occur naturally humans. Anywhere the neomycin resistance gene would be found in the patient could be directly tied to the introduced TIL cell.                      

The proposal to introduce genetically altered TIL  cells into human subjects was reviewed by the  Recombinant Advisory Committee of the National Institutes of Health. The persons serving on that committee recognized the profound significance of  the proposed experiments. Not only could these experiments lead to improved cancer treatment, they also would pioneer the field of gene therapy. It was clear  that the next step in development would be to use genetic engineering to alter human cells to perform different functions. Cells could be modified genetically and introduced into tile body to cure disease. After many long debates about the safety and scientific validity of the experiments, the Recombinant Advisory Committee approved tile experimental plan of Rosenberg, Blaise and Anderson.

Shortly thereafter, TIL cells obtained from several patients were marked with tile neomycin resistance gene and introduced back into those patients. The  researchers were able to follow the specific movement of the TIL cells that they had introduced. They were  able to improve the treatment regime so as to enhance  survival of the introduced TTL cells.

Rosenberg, Blaise, and Andersoext proposed to genetically alter TIL cells by introducing the gene for  tumour necrosis factor. Lymphocytes that produce tumour  necrosis factor are able to cause the shrinkage of malignant tumours. Again after extensive debates, the  Recombinant Advisory Committee of the National Institutes of Health recommended that clinical trails of  such recombinant cells be permitted. These trials of  represented the first true attempts at gene therapy. A new era m modem medicine based on recombinant DNA technology had begun. A new treatment was  added in the continuing battle against cancer.

 

Summary

Immunodeficiencies

• An immunodeficiency is the result of an inadequate immune response.

• It can be inherited or acquired.

Severe Combined Immunodeficiency

• People with severe combined immunodeficiency disease (SCID) have neither functional B or T lymphocytes. They have no immunological response. Any infection can be fatal.

• Adenosine deaminase linked to polyethylene glycol (PEG-ADA) is used to treat SCID. Bone marrow transplants are also done.

DiGeorge Syndrome

• If the thymus does not develop properly, T cells are not differentiated and DiGeorge syndrome results.

Bruton Congenital Agammaglobulinemia

• If B cells do not differentiate and produce antibodies, Bruton congenital agammaglobulinemia results. This condition affects only males.

• It is treated with IgG to maintain antibody levels in the circulatory system.

Late-onset Hypogammaglobulinemia

• Late-onset hypogammaglobulinemia is the most common  immunodeficiency. Individuals with this condition are deficient in circulating B cells and/or B cells with IgG surface receptors.

Complement and Cellular Deficiencies

• If C3 complement is not produced, the body cannot defend against bacterial infections.

• Defective monocytes, neutrophils, and macrophages may cause immunodeficiencies.

Malignant Cell Development

• If the immune response system does not recognize and respond to the presence of abnormal cells, malignant cells can continue to grow.

Acquired Immunodeficiency Syndrome (AIDS)

• AIDS is caused by the human immunodeficiency virus (HIV). HIV destroys T helper cells. The proportion of T suppressor cells increases, which depresses immune functions. B cells do not produce sufficient antibodies. Amounts of lymphokines are lowered.

• There is no cure for AIDS. Prevention is the only way to control it.

• Azidothymidine (AZT) and dideoxyinosine (ddl) slow the rate of HIV replication.

Autoimmunity

• Autoimmunity is the result of the inability of the body to properly recognize self-antigens. The immune system kills the body’s own cells.

Rheumatoid Arthritis

• Rheumatoid arthritis is chronic joint inflammation. Lysozymes attack antigens and B cells make IgM in response, causing inflammation. There is no cure.

Myasthenia Gravis

• Myasthenia gravis affects the neuromuscular system. The pores ieuron membranes are blocked. These neurons stimulate muscles. Blocked neurons do not release acetylcholine, which initiates muscle cell contraction. Treatment is with drugs that inhibit the enzyme that breaks down acetylcholine.

Systemic Lupus Erythematosus

• Systemic lupus erythematosus is a systemic autoimmune disease. Autoantibodies are made against DNA components. The deposition of immune complexes causes inflammation.

Graves Disease

• Graves disease is an autoimmune disease of the thyroid in which antibodies to thyroid-stimulating hormone receptors are produced, allowing the overproduction of hormones.

Multiple Sclerosis

• Multiple sclerosis is believed to be a T-cell-mediated autoimmune disease. Lesions containing macrophages and lymphocytes are found in the central nervous system of people with MS.