The goal for all infectious diseases is to find a drug that can quickly eradicate the infecting pathogen, such as anti-biotics, or a vaccine that can prevent the infections from ever taking root in the body. For HIV, we do not yet have either of these options available as current drugs used for treatment are effective at keeping the virus down but not out. To understand why there isn’t yet a cure, it’s important to know how HIV infects the body.
HIV infection can only take hold if the virus finds its way into the blood stream. It can be transmitted through unprotected vaginal and anal sex, injections with needles with HIV present or through mixing blood.

HIV-infected H9 T cell | NIAID

The immune system is made up of white blood cells; these circulate around the body targeting foreign invaders (viruses, bacteria and parasites for example) and destroy them. HIV targets a certain type of immune cell, called a T cell, and integrates itself into the immune cell’s DNA. By hiding inside the immune cell itself, the body can no longer identify it as a hostile body.
When HIV is active and untreated, it tricks the white blood cell to create copies of HIV. The cell then dies, releasing the virus into the bloodstream where it goes on to infect the next cells. In this way the virus multiplies and the viral load builds up in the body.

HIV on Bridges Between Infected Immune Cell and Uninfected Brain Cell | NIH Image Gallery

ARVs, the drugs that suppress HIV, can ‘see’ which cells are actively creating copies of the virus and works to prevent this multiplying process. This helps keep the overall viral load low, or even undetectable. However, these drugs cannot see the HIV if it is lying dormant inside a cell. The virus waits in small amounts in the body, often in reservoirs that are difficult for drugs to reach: the brain, in nerve endings etc. As soon as the patient stops taking their medication, these small numbers of virus are all it takes to start to replicate in T cells again. This is why ARVs need to be taken daily over an entire lifetime.
Usually the virus springs back as soon as the patient stops taking ARTs, however, there are also cases of the virus staying in remission for a while. Remission is when the patient stops suppressing the virus with drugs and the immune system continues to repress the virus for a period of time. This could be months or years.
HIV is tricky because it knows where to hide. In order to cure it, scientists have to think of cunning ways to destroy these HIV reservoirs, or lock the HIV in the reservoirs so that it can’t ever come out. Research is ongoing, but until there is a cure, HIV-positve people should adhere to a daily ARV regimen.

Written by Caroline Reid