Human immunodeficiency virus (HIV) falls in a class of viruses called retroviruses. HIV is a virus infects by invading certain cells of immune system, specifically the white blood cells called T- helper lymphocytes or CD4 cells ,which normally activates other cells in the immune system to fight infection,. HIV. . Over the course of HIV infection, the immune system deteriorated since HIV kills T-helper lymphocytes and the body cannot fight the virus or subsequent infections. Thus, infected person becomes vulnerable to other secondary infections and cancer that are much rarer in healthy inviduals. Person with HIV infection are categorized as those living with HIV and those with acquired immunodeficiency syndrome (AIDS) diagnosis. An AIDS diagnosis is made when the presence of HIV is confirmed and the CD4 count drops below 200 cells/mL or after an AIDS indicator condition is diagnosed. Regimens of antiviral drugs can slow the immune system deterioriation in infected patients and extend the life expectancy of those who have developed AIDS. The most common serotype is HIV-1 which is distributed worldwide
The RNA viruses which are retroviruses enters CD4 cells by binding to a specialized site which is receptor on a body cell. Then, the virus loses its protective coat and releases RNA, its genetic material , and an enzyme known as reverse transcriptase . The enzyme reverse transcriptase contained inside the viral core to convert their RNA into a form that can enter the host cell’s nucleus and incorporated with the cell’s genetic material. Hence , it build DNA strands based on the RNA strand and it is shown in figure 1.1 in 3-D structure in cartoons display which is taken from RasMol. This reaction happens at in the polymerase active site, which is formed by two sets of arms that surround the RNA and DNA. The polymerase site is shown in figure 1.2 which is