HIV & AIDS Flashcards
What are the main target receptors for HIV infection?
CD4+ receptors
What cells are the main target for HIV infection?
T helper cells
What are the seven stages of the HIV life cycle?
- Binding (HIV binds to receptors on the surface of a CD4 cell)
- Fusion (HIV envelope and the CD4 cell membrane fuse, allowing HIV to enter the CD4 cell)
- Reverse transcription (Inside the CD4 cell HIV releases and uses reverse transcriptase to convert its genetic material -HIV RNA- into HIV DNA) This allows HIV to enter the CD4 cell nucleus and combine with the host cellular DNA)
- Integration (Inside the CD4 cell nucleus HIV releases the enzyme integrase which allows insertion of the viral DNA into the cellular DNA)
- Replication (Once integrated into the CD4 cell DNA HIV uses the machinery of the CD4 cell to make long chains of HIV proteins)
- Assembly (New HIV proteins and HIV RNA move to the surface of the cell and assemble into immature(noninfectious) HIV)
- Budding (Newly formed HIV pushes itself out of the host CD4 cell. The new HIV releases protease which breaks up the long protein chains that form the immature virus. The smaller HIV proteins combine to form mature (infectious) HIV.
What is the recommended first line screening test for HIV?
4th generation assay that tests for the HIV antibody and p24 antigen
What test is a marker of infectiousness in HIV?
HIV RNA load
How many days after infection with HIV would antibodies be detected?
~21 - 25 days after infection
How many days after infection with HIV is the p24 antigen detected?
~15 - 19 days. (6 days earlier than the antibodies)
How many days after infection with HIV will a plasma HIV RNA load be detected?
~ 9 - 11 days
What is meant by the “window period” in HIV?
The time between HIV transmission and the ability to detect the infection using serology tests.
What antigen is the test looking for in HIV testing?
p24
What is seroconversion?
The period of time during which HIV antibodies develop and become detectable.
Generally takes place within a few weeks of initial infection.
It is often, but not always, accompanied by flu-like symptoms including fever, rash, muscle aches and swollen lymph nodes.
What is the function of T helper cells (CD4 cells)
- Release T cell cytokines
- Essential in B cell antibody class switching
- Activate cytotoxic T cells
- Maximise bactericidal activity of phagocytes such as macrophages.
What is normal CD4+ count?
500 - 1600 cells/mm3
Below what CD4+ count is there a risk of oppertunistic infection?
If you get a needlestick injury, or have unprotected sex with someone who is HIV+ how many days do you have to take PEP before the infection taken hold?
3 days
