What is AIDS?
Human Immunodeficiency Virus (HIV) is an RNA virus (known as a retrovirus) that specifically attacks the immune system, which affects your ability to fight other infections. HIV infects CD4 cells, which are white blood cells that play an essential role in the immune response to infection. Without treatment, the virus multiplies and spreads, and the amount of virus in your body increases, while at the same time, the number of CD4 cells decreases. Eventually, the immune system becomes severely damaged and is unable to fight infection, leading to an increased risk of opportunistic infection, which is an infection that the body usually can fight when not immunocompromised. This stage of HIV infection is called Acquired Immune Deficiency Syndrome (AIDS) and is potentially life-threatening.
How do antiretrovirals work?
Antiretrovirals are used to treat HIV infection, and are designed to prevent the replication of the virus. The aim of antiretroviral treatment is to reduce the amount of virus in the body (viral load) down to a low level and prevent the spread of HIV. Antiretrovirals do not kill the virus. Once HIV replication is reduced, the numbers of CD4 cells can increase, so that the immune system can recover, and further damage is prevented. Antiretroviral therapy uses a combination of different drugs that work by attacking a different stage of the viral replication process. Using a combination of drugs reduces the risk of the virus becoming resistant. Some of these combination medications are supplied as a single tablet containing a fixed dose of two or three drugs.
Types of antiretroviral drugs include:
- Reverse transcriptase (RT) inhibitors. RT is a virus-specific enzyme needed for HIV replication. There are two types of RT inhibitor that work by different mechanisms:
- nucleoside analogue reverse transcriptase inhibitor (NRTI), such as tenofovir and zidovudine
- non-nucleoside reverse transcriptase inhibitor (NNRTI), such as efavirenz and nevirapine.
- The viral protease enzyme is another drug target. This enzyme is needed to allow the mature active virus to be released and infect new cells. These drugs include ritonavir and indinavir.