• Glycoproteins are important as they enable the virus to bind to human cells – leading to immunodeficiency. Drugs can target these gp proteins
• P24 protein is important as it can be tested for in an antigen detection test, so we can test for this without having to wait for the body to make antibodies. Combining this test with the test for antibodies is good diagnostically
• The reverse transcriptase enzyme converts the RNA into DNA and then this is embedded into a human chromosome

The DNA then forms new viral RNA, proteins required to make the virus and also viral protease which cleaves the chain of proteins to make the new virus

The new viruses can then spread off to infect other cells

Due to the effect on the T helper cells, HIV causes secondary immunodeficiency. As T helper cells are required in initiating an immune response

Initially CD4 levels are above 1000 – normal level

First few weeks – non specific symptoms, CD4 cells dropping

Later the immune system fights it off to a degree and CD4 levels pick back up to a point that is enough for most people to mentain immunity

Then over years, gradually, the number of CD4 decrease and HIV increase. Below 400 CD4 is when we see symptoms

CD4:

This is a count of the number of CD4 cells in the blood. These are the cells destroyed by the HIV virus. The lower the count the higher the risk of opportunistic infection.

• 500-1200 cells/mm is the normal range
• Under 200 cells/mm is considered end stage HIV / AIDS and puts the patient at high risk of opportunistic infections