The HIV Lifecycle

Once HIV is in the body, it targets and infects a certain type of white blood cell called a CD4 cell. HIV then takes over or "hijacks" these cells and turns them into factories that produce thousands of copies of the virus. The steps HIV goes through to complete this process are as follows: 1. Binding and Fusion: HIV begins to enter a CD4 cell by binding or attaching itself to a specific point, called a CD4 receptor, on the cell's surface. HIV must then bind to a second co-receptor, either the CCR5 co-receptor or the CXCR4 co-receptor. This allows the virus to join or merge with the CD4 cell in a process called fusion. After fusion, HIV releases its RNA (genetic material) and enzymes (proteins that cause chemical reactions) into the CD4 cell. 2. Reverse Transcription: HIV's genetic material is called RNA, which contains the "instructions" that will reprogram the CD4 cell so that it produces more viruses. In order to be effective, HIV's RNA must be changed into DNA. An HIV enzyme called reverse transcriptase changes the HIV RNA into HIV DNA. 3. Integration: Next, the newly formed HIV DNA enters the nucleus (command center) of the CD4 cell. Another HIV enzyme called integrase combines or integrates HIV's DNA with the CD4 cell's DNA. 4. Transcription: Once the virus has become part of (is integrated into) the CD4 cell, it commands the CD4 cell to start making new HIV proteins. The proteins are the building blocks for new HIV viruses. They are produced in long chains. 5. Assembly: An HIV enzyme called protease cuts the long chains of HIV proteins into smaller pieces. As the smaller protein pieces come together with copies of HIV's RNA, a new virus is put together (assembled). 6. Budding: The newly assembled virus pushes ("buds") out of the original CD4 cell. This new virus is now able to target and infect other CD4 cells.