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When will there be an HIV vaccine?

12 June, 00:00

The Human immunodeficiency virus (HIV) was discovered in 1981. How does the pathogenic agent of “the plague of the 20th century” differ from other viruses, say, the tick-borne encephalitis virus (TBE)? Both contain special external proteins for which antibodies are produced. However, these proteins remain the same in TBE, whereas they are constantly changing in HIV. Its RNA is replicating with many mistakes, which influences the structures of the virus’s external proteins.

As a result, each new generation of the virus is comprised of sheer mutants; geneticists call this phenomenon gene drift, and in the case of HIV - antigene drift. The virus mutates so quickly that no immunity or science can keep up with it. It is impossible to create such a variety of antibodies. It never occurred to Pasteur to create a vaccination on the basis of a ghost- virus, therefore Pasteur’s traditional methods fall away automatically, www.medportal.ru reports.

The situation becomes much more complicated because of the lack of a suitable model for studying HIV’s effect on animals. As research has shown, besides humans, HIV affects only chimpanzees, but interestingly enough AIDS does not develop in primates. HIV is a pathogen, whereas AIDS is an acquired immune deficiency syndrome producing a number of symptoms that develop in a body infected with HIV. This is a disease.

The worst thing is that HIV affects those cells that should kill it. These are CD4 cells, or T-helpers, and macrophages. The virus lives in some of them, but you cannot destroy all the useful cells because this leads to inevitable death. You have to learn either to “hook” the HIV or kill only the cells that contain the virus, with no harm to the immune system.

Taking into account all of the above, only a final clinical trial group of volunteers can define the quality, side effects, and effectiveness of vaccines. Here, many different ethical and material problems arise in addition to the reliability of the results. In order to maintain the integrity of clinical trials, all the participants have to have had some sort of contact with the same HIV-infected person in order to be able to be infected with the same virus subtype. Clearly, this is impossible.

Fortunately, the achievements of genetic engineering have come to the aid of medical researchers. There are now recombinant vaccines that introduce a genome segment responsible for producing a necessary antigen of a pathogenic virus into a carrier microorganism that is harmless to humans, e.g., a yeast cell or a harmless virus. The carrier organism reproduces, producing a needed antibody among other products of its vital activity. The AidsVax vaccine produced by the US-based VaxGen Inc., which contains the gp120 external protein of the virus, was designed in this way. It was the first vaccine to be tested on people.

The vaccine went through all the clinical stages with such success that the self-confident company started to build a plant to produce AidsVax. But a stunning failure, not success, awaited the Americans. The final clinical stage of the research proved that the vaccine does not guarantee 100-percent protection from AIDS. At the most, AidsVax provides 78-percent protection, and only among Afro-Americans. Volunteers from other ethnic groups became sick with the same or even higher frequency than people in the control group, who received a placebo instead of the drug.

But scientists are not discouraged. Dr. Peter D. Kwong from the Vaccine Research Center at the National Institute of Allergy and Infectious Diseases in the US recently discovered the most conservative segment of the virus and will deliver a shattering blow to this Achilles heel of AIDS. Moreover, many other recombinant vaccines and vaccine preparations, produced in another way, have been created. True, the absolute majority of volunteers for the panacea against “the plague of the 20th century” are still stuck in pre-clinical trials, but there is no need for haste.

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