HIV, or human immunodeficiency virus, is the virus responsible for the disease AIDS. Scientists have studied HIV extensively in an attempt to find weaknesses in the virus or its mode of action that they can take advantage of to help treat the disease or stop its spread.
Classification
HIV is a retrovirus, a type of virus made of RNA that moves into a cell and uses the cell's materials to create a DNA copy of itself. This DNA inserts itself into the DNA of the cell. The viral DNA then creates new RNA copies to send out to infect other cells. HIV is also known as a lentivirus, a specific type of retrovirus characterize by having a long dormant period between initial infection and the full blown disease, according to the National Institute of Allergy and Infectious Disease.
Types
There are two strains of HIV, according to Avert: HIV-1 and HIV-2. HIV-1 has spread worldwide and causes most cases of AIDS. HIV-2 exists mainly in West Africa. It is less easily transmitted and has a longer course of infection before AIDS develops. HIV-1 is further divided into subgroups M, O, N and P. Subgroup M makes up a majority of cases of AIDS in the world and there are nine identified subtypes of HIV-1 M. These nine subtypes have different geographical distributions and likely developed in different areas of the world from a single HIV-1 M strain.
Structure
The genetic material of HIV sits in the center of the virus in a bullet-shaped viral core surrounded by a protective protein coat. This viral core contains all of the genetic information the virus needs to infect cells, build new viral particles, make proteins to carry out viral activity and evade the host's immune system. HIV contains not only this viral core, but also an outer membrane called the viral envelope. The viral envelope sports proteins derived from the virus itself and commandeered from the host cell.
Progression
After initial infection with HIV, the immune system of the host attacks the virus and tries to destroy it. HIV evades the immune system by integrating itself into CD4 immune cells. The immune system can hold off the virus for 10 to 15 years until the number of cells producing new virus overwhelms it and the number of CD4 cells drops to below 200 per cubic milliliter. At this point, the person is said to have developed AIDS.
Treatment
Treatment for AIDS is aimed at interrupting the life cycle of the virus, according to Merck. Some medications used against the disease stop the conversion of RNA into DNA. Others prevent the DNA from integrating into the host DNA, stop the action of proteins that help the virus function or alter receptors on the host's own cells to keep the virus from entering those cells. Researchers are attempting to develop a vaccine that would allow the immune system to recognize HIV and destroy it before infection takes hold.
