One of the most infamous viruses in modern history burst onto the scene in 1981, when clinicians started observing strange cases of immunodeficiency in patients who had no obvious reasons for their ill health. By 1983, two independent groups of researchers had found the retrovirus responsible, and today, it’s known as the human immunodeficiency virus (HIV). 30 years after it was discovered, we still don’t have a vaccine that can effectively prevent HIV infection.
What’s the holdup?
There are several contributing factors to the problems with successfully developing an effective HIV vaccine. This wily little retrovirus is determined to live and to keep spreading, and like other viruses, it’s extremely adept at evolving, shifting and staying one step ahead of medicine. That means it poses a unique challenge to the researchers who want to stop it in its tracks; we may have successfully eradicated smallpox, but can we do the same to HIV?
One of the problems with HIV is that it’s not a uniform virus. It has a number of subtypes, known as clades, found in various populations around the world. Each clade is different, and vaccinating against one will not necessarily protect a patient from other strains. Thus, vaccine developers have to look for strands of DNA in infected cells that are as common to as many clades as possible (as an RNA virus, HIV penetrates cells and hijacks their functions to force them to turn out new copies of itself), with the goal of sensitizing the patient’s immune system and teaching it to go on the attack when it spots those genetic sequences.
That’s tough to do, especially since HIV regularly evolves, exchanging, changing and dropping genetic material. Some vaccines haven’t been very effective, while others have actually increased susceptibility to HIV, which is exactly the opposite of what researchers want to see. Thus, any successful vaccine has to consider the complex issue of differing clades and evolution.
One approach has relied on taking antibodies from infected patients and introducing them into the bodies of healthy patients. If the body accepts the antibodies, they’ll flag the virus and infected cells for destruction, sending in the cleanup crews of the immune system to take out the HIV. However, antibody therapy is extremely expensive and time-consuming, which makes it less practical to implement on a global scale.
Researchers have also been exploring ways to use the body’s T cells, an important part of the immune system. So far, none of the vaccines they’ve developed with T cells in mind have been effective, but they have managed to reduce the viral load in already infected patients, which is an extremely positive sign. Limiting the presence of HIV in the body means less health problems for the patient, and lowers the risk of full-blown AIDS.
Assuming researchers manage to develop a vaccine that is generally effective against most strains of HIV — and many seem to think they’ll succeed eventually — the road will be far from over. First, the virus needs to be taken out of the lab environment and tested in conditions with escalating size, complexity and states. Many medical developments barely make it out of the lab before it becomes apparent that they have many problems, and they can’t realistically be brought to market. It could take ten years or more, even with fast-tracked research, development and regulatory permissions, to turn a promising vaccine in the lab into one that would be accessible to consumers.
And when it does become available to the public, it’s likely to be sold at a high price point, reflecting the expenses involved in producing it. Even though many researchers are engaged in their work for the public good and some of the facilities researching HIV vaccines are publicly owned, private industry is interested too, and if it can win the patent race, it will charge a pretty penny for HIV vaccination. This in turn may spark a difficult conversation about medical patents and the availability of potentially life-saving medical advances.
Photo credit: Army Medicine.