The Different Stages of HIV Infection

HIV infects cells in the immune system and the central nervous system. The main cell HIV infects is called a T helper lymphocyte. The T helper cell is a crucial cell in the immune system. It co-ordinates all other immune cells so any damage or loss of the T helper cell seriously affects the immune system.

HIV infects the T Helper cell because it has the protein CD4 on its surface. HIV needs to use CD4 to enter cells it infects. This is why the T helper cell is referred to as a CD4 lymphocyte. Once inside a T helper cell, HIV takes over the cell and the virus then replicates. In this process (which takes around a couple of days) the infected cell dies. New virus then seeks out new T helper cells to infect.
However, battling against this the immune system is rapidly killing HIV and HIV-infected cells, and replacing the T helper cells that have been lost.

HIV progression can generally be broken down into four distinct stages: primary infection, clinically asymptomatic stage, symptomatic HIV infection, and progression from HIV to AIDS.