Many articles will write about the horrors of AIDS, the tragic deaths, the many orphans. Other writings, namely textbooks, will describe the best methods of avoiding infection. Scientific publications will tell of researchers all around the world who are trying to cure the many AIDS victims. Not this one. No, this article will bypass all those and ask, how can people stop the virus medically before people even become infected? Many common viruses these days can be prevented through vaccines. Scientists have had a lot of practice making vaccines, and usually know about how to generate them. So why doesn’t HIV have one?
HIV poses many difficulties not normally confronted when creating vaccines for other common viruses, mainly due to its great variety. When HIV replicates its DNA, the virus uses an error-prone reverse transcriptase with no polymerase proof-reader. This results in not only a variety of proteins, but also a variety in the length and size of glycosylation sites (areas on the cell membrane where glucose is attached to the proteins of the membrane). Traditional vaccines’ antibodies use glycosylation sites to identify the viruses they’re supposed to destroy, but since every cell of this virus is different a standard method becomes impossible.
There are also other problems, of course. The virus establishes a chronic infection when it enters an unprepared immune system, meaning that some of its cells can hide from the initial attack of white blood cells. They can remain there harmoniously for years, undetected, until the immune system falls under the threat of another serious medical condition. Then, the HIV cells take advantage of a preoccupied immune system to do their worst. Though AIDS is usually blamed, many people do not die of HIV itself. They die of other, often harmless diseases. Another difficulty is that being a virus, HIV can also evolve quickly. Scientists would have to find a vaccine every few years to successfully combat the spread of AIDS.
So what can scientists do? Live attenuated viruses have been tried, but cannot be used due to significant safety concerns. Whole killed viruses and protein subunits, two other common strategies, are safe but have incredibly limited capabilities. Researchers are now also trying novel strategies, the most developed of which include plasmid DNA and live recombinant vectors. However, due to their small nature (as well as other factors), multiple injections, each containing a high dose of DNA vaccine, are necessary to induce a response. Therefore, adjuvants for these vaccines will need to be developed as well if they are to be effective. Adjuvants simulate the immune system and increase its response to the vaccine, though they have no antigenic effect at all.
Through all the challenges, there have been a couple hopefuls. Recently released was the report of a study conducted in Thailand, called RV 144. RV 144 is the first evidence of a possible working vaccine scientists have had. Over 16,000 volunteers between the ages of 18 and 30 were given the ALVAC® HIV (vCP1521) vaccine every 6 months for three years. The last two doses were supplemented with the AIDSVAX®B/E (gp120) vaccine. The ALVAC® HIV (vCP1521) vaccine consisted of three genetically engineered versions of HIV genes (env, gag and pro) carried by a vector, an inert form of canary pox (a bird virus that cannot infect humans). These vaccines did make a difference; however, recipients only had a 30% less chance of acquiring the disease and there is some debate going on about whether this is sufficient evidence to put the vaccine into circulation.
Though there has been a long struggle to eradicate HIV; many more years, if not decades, will be necessary to develop an efficient, wide-spread vaccine. Still, scientists all over the world are searching frantically for the cure, quoting Martin Luther King Jr.’s “I have a dream.”
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Barouch, Dan H. “Challenges in the development of an HIV-1 Vaccine.”Nature 2 Oct. 2008: Vol. 455(7213):613-619. Web. 10 Jan. 2010.
“VAX; The Bulletin on AIDS Vaccine Research” IAVI December 2009: Vol. 7: Number 12. Web 10 Jan. 2010.