virology presentation.pptx life cycle of the hiv
- 1. LIFE CYCLE OF HIV Presented By: M. KASHIF NAZIR
- 2. LIFE CYCLE OF HIV VIRUS • The seven stages of the HIV life cycle are: 1. Binding 2. Fusion 3. Reverse transcription 4. Integration 5. Replication 6. Assembly 7. Budding
- 3. 1. Binding When HIV attacks a CD4 cell, the virus binds (attaches itself) to molecules on the surface of the CD4 cell. First a CD4 receptor and then either a CCR5 or CXCR4 coreceptor. Cysteine- Chemokine Receptor 5 (CCR5): A protein on the surface of certain immune system cells, including CD4 T lymphocytes (CD4 cells). CCR5 can act as a coreceptor (a second receptor binding site) for HIV when the virus enters a host cell. C-X-C Chemokine Receptor 4: CXCR4 can act as a coreceptor (a second receptor binding site) for HIV when the virus enters a host cell.
- 4. 2. Fusion The second steps in the HIV life cycle is after HIV attaches itself to a host CD4 cell, the HIV viral envelope fuses with the CD4 cell membrane. Fusion allows HIV to enter the CD4 cell. Once inside the CD4 cell, the virus releases HIV RNA and HIV enzymes, such as reverse transcriptase and integrase.
- 5. 3. Reverse Transcription Once inside a CD4 cell, HIV releases and uses reverse transcriptase (an HIV enzyme) to convert its genetic material HIV RNA into HIV DNA. The conversion of HIV RNA to HIV DNA allows HIV to enter the CD4 cell nucleus and combine with the cell’s genetic material cell DNA.
- 6. 4. Integration The fourth of seven steps in the HIV life cycle. Once inside the host CD4 cell nucleus, HIV releases integrase, an HIV enzyme. HIV uses integrase to insert (integrate) its viral DNA into the DNA of the host cell. Integrase strand transfer inhibitors (INSTIs) block integrase (an HIV enzyme). HIV uses integrase to insert (integrate) its viral DNA into the DNA of the host CD4 cell. Blocking integrase prevents HIV from replicating.
- 7. 5. Replication Once HIV is integrated into the host CD4 cell DNA, the virus begins to use the machinery of the CD4 cell to create long chains of HIV proteins. The protein chains are the building blocks for more HIV.
- 8. 6. Assembly During assembly, new HIV RNA and HIV proteins made by the host CD4 cell move to the surface of the cell and assemble into immature (noninfectious) HIV.
- 9. 7. Budding During budding, immature (noninfectious) HIV pushes itself out of the host CD4 cell. (Noninfectious HIV can't infect another CD4 cell.) Once outside the CD4 cell, the new HIV releases protease, an HIV enzyme. Protease breaks up the long protein chains in the immature virus, creating the mature (infectious) virus.