|MadSci Network: Immunology|
HIV-1 and HIV-2 are lentiviruses (a subset of retroviruses). All retroviruses integrate their viral genome into the host chromosomes as a part of their life cycle. This makes it impossible to remove all viruses and truly "cure" an infection with a retrovirus. For this reason and others, prevention is far more desirable than treatment. HIV infection can be prevented both through the actions of individuals to practice safer sex, not share needles, etc, and through the actions of governments to screen for infections and do contact tracing and other methods to slow infection transmission chains.
Vaccines for HIV are being developed, but it is a very difficult problem. For one thing, most currently available vaccines, such as the vaccine against polio virus, do not entirely prevent infection, they only prevent disease or lessen the severity of the infection. For retroviruses, we want what is known as "sterilizing immunity", meaning that the vaccinated person is completely immune from infection. Currently we have many vaccines that prevent AIDS from developing in Rhesus macaques, which are used as the animal model for AIDS. However, some infection still occurs, and for a human vaccine we want sterilizing immunity. A second problem is that there is a great diversity of HIV-1 viruses circulating in the world. It is difficult to make one vaccine that protects against many different strains of a virus.
For treatments, the currently available drug regimens are very close to being good enough. Affordability and deliverability to the third world is currently the biggest problem. In the developed world, among people with health insurance, the drugs work very well extending lifespans to nearly normal for the majority of treated people. However, some of the drugs are expensive and/or require refrigeration, which prevents most of the developing world from having access. These same problems would apply to a vaccine if we had one today.
Current drug regimens include at least 2 reverse transcriptase inhibitors, but the best regimens include 3 drugs with one of them often being a protease inhibitor. Some drug combinations can be put together in a single pill to be taken just once a day, which has greatly eased the complications of treatment. Other combinations are more complicated, for example with one drug needing to be taken on an empty stomach and another taken with a meal. A small percentage of people have side effects from taking one or more drugs, so they need to switch to other drugs. Also, some people are infected with viruses that are resistant to one or more drugs. So finding a combination that works for each individual patient can be difficult. In much of the developing world, there are not enough trained physicians to help with delivery of the currently available and affordable drugs.
So, currenlty the major bottlenecks in slowing the pandemic are in the areas of counseling and testing to prevent new infections, quickly diagnosing new infections, and preventing the newly infected people from continuing to spread the virus. Also, there is a huge shortage of people trained to provide the best treatments. Drugs could be made more affordable by changes in patents, and more local production of drugs.
For the developed world, new drugs that target the HIV integrase, and drugs which affect human proteins that the virus needs for reproduction (such as the CCR5 protein needed for viral entry into the cell) are being developed.
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