Since the start of the HIV epidemic, a series of drugs have been developed which significantly prolong the lives of people who are HIV positive. Called “antiretroviral drugs”, they block the virus’s ability to replicate. They can delay the onset of Aids by slowing the loss of patients’ CD4+ cells, but they are not a cure.
There are four main classes of drugs, operating at different points in the HIV cycle:
Entry inhibitors: These bind to the proteins on the outside of the HIV virus, stopping it from attaching itself to and entering a CD4+ cell. Only one drug, Fuzeon, has so far reached the market.
Nucleoside reverse transcriptase inhibitors: These stop the virus from making a copy of its own genes. Nucleosides are the building blocks of the genes. The drugs disrupt the copying process by supplying faulty versions of these building blocks.
Non-nucleoside reverse transcriptase inhibitors: These also affect the copying process. They disrupt it by attaching themselves to the enzyme which controls the process, reverse transcriptase.
Protease inhibitors: These drugs lock onto another enzyme, protease, which plays a key role in the assembly of the new virus particles.
Antiretroviral drugs should be taken in combination. Usually three different drugs, from at least two different classes, are used at once. As HIV mutates, some versions of the virus become resistant to drugs. The chances of keeping it in check are therefore much higher if several drugs are used. Some people are now becoming infected with strains of the virus which are already resistant to particular drugs.
For further information on HIV/AIDS visit the information resources page of the Terrence Higgins Trust website at: