Human immunodeficiency virus (HIV) is a retrovirus that causes acquired immunodeficiency syndrome (AIDS) by attacking CD4+ T cells. It enters the host cell, converts its RNA into DNA using the reverse transcriptase enzyme, and incorporates this proviral DNA into the host's genome. This allows the virus to use the host cell's machinery to produce new virus particles and spread infection. There is currently no cure for HIV/AIDS.

1. Human immunodeficiency virus HIV

2. Human immunodeficiency virus HIV is the cause of acquired immune deficiency syndrome (AIDS) It is a single stranded RNA virus

3. Human immunodeficiency virus It has a spherical shape with a diameter of about 0.1  m It is outer lipid membrane is taken from material surrounding the host cell

4. Human immunodeficiency virus The genetic material is enclosed in a protein caspid Within the caspid is also some molecules of reverse transcriptase

5. Human immunodeficiency virus It is a member of a group of viruses called retroviruses. These viruses reverse the normal flow of genetic information

6. Human immunodeficiency virus The reverse transcriptase makes copies of DNA from the viral RNA. The viral DNA made is known as a provirus

7. Human immunodeficiency virus The provirus is then spliced into the host cell’s own DNA in an act of piracy. The host cell is now ready to make copies of the virus

8. Human immunodeficiency virus Visit http://www.cellsalive.com/hiv1.htm http://www.hopkins-aids.edu/hiv_lifecycle/hivcycle_txt.html For a good overview of the “life-cycle “ of HIV

10. HIV and AIDS HIV is passed from human to human by: Sexual contact with an infected person Shared use of a hypodermic needle with an infected person Injection of contaminated blood or blood products From an infected mother to her fetus or suckling baby

11. HIV and AIDS HIV attacks the body helper T cells These are WBC – lymphocytes The T cells have proteins on their surface which bind to the HIV

12. HIV and AIDS The virus latches onto the T cells and uses them like ‘door handles’ to gain entry to the cell Once inside the virus RNA is released into the cytoplasm

13. HIV and AIDS The reverse transcriptase transcribes the viral RNA into DNA

14. HIV and AIDS The enzyme integrase splices the viral DNA into the host cell DNA

15. HIV and AIDS The infective virus now exists as a segment of DNA in the host cell. The cell may pass through a period of latency as the viral DNA awaits a chemical signal to prompt the host cell to start to produce new virus

16. HIV and AIDS The host cell then transcribes the viral DNA and starts to make many copies of the viral RNA and viral protein

17. HIV and AIDS These molecules spontaneously assemble into new viral particles

18. HIV and AIDS The virus escapes the T cell to infect other T cells The infected T cell eventually is destroyed by the virus.

19. Treatment of AIDS There is no cure or vaccine for AIDS or HIV infection A number of anti-HIV drugs are available The most well known of these zidovudine (AZT) works by blocking the viral reverse transcriptase.