HIV Lifecycle

What HIV does in your body

When you are infected with HIV, there are multiple things happening in your immune system at the cellular level.

Transmission
When HIV enters your body through sexual contact, transfusions with infected blood, or by injection with a needle that has infected blood in or on it, researchers believe that the virus attaches to a specific type of immune system cell called a dendritic cell. These cells are found in mucocutaneous (mucosal membranes) areas that line the mouth, the vagina, rectum, penis, and the upper gastrointestinal tract. Scientists think that these dendritic cells transport the virus from the site of the infection to your lymph nodes where HIV can infect other immune system cells.

The life-cycle of HIV in your cells

HIV can infect multiple cells in your body, including brain cells, but its main target is the CD4 lymphocyte, also called a T-cell or CD4 cell. When a CD4 cell is infected with HIV, the virus goes through multiple steps to reproduce itself and create many more virus particles.

The process is broken up into the following steps:

1. Binding and Fusion: This is the process by which HIV binds to a specific type of CD4 receptor and a co-receptor on the surface of the CD4 cell. This is similar to a key entering a lock. Once unlocked, HIV can fuse with the host cell (CD4 cell) and release its genetic material into the cell.
2. Reverse Transcription: A special enzyme called reverse transcriptase changes the genetic material of the virus, so it can be integrated into the host DNA.
3. Integration: The virus’ new genetic material enters the nucleus of the CD4 cell and uses an enzyme called integrase to integrate itself into your own genetic material, where it may “hide” and stay inactive for several years.
4. Transcription: When the host cell becomes activated, and the virus uses your own enzymes to create more of its genetic material—along with a more specialized genetic material which allows it make longer proteins.
5. Assembly: A special enzyme called protease cuts the longer HIV proteins into individual proteins. When these come together with the virus’ genetic material, a new virus has been assembled.
6. Budding: This is the final stage of the virus’ life cycle. In this stage, the virus pushes itself out of the host cell, taking with it part of the membrane of the cell. This outer part covers the virus and contains all of the structures necessary to bind to a new CD4 cell and receptors and begin the process again.

These steps of the life-cycle of HIV are important to know because the medications used to control HIV infection act to interrupt this replication cycle.

For more information, see NIH’s HIV Life Cycle.