Unistat : hiv infection
reference: http://www.cellsalive.com/hiv0.htm
Human Immunodeficiency Virus (HIV)
Overview
Human Immunodeficiency Virus (HIV) presents a complex knot for scientists to unravel. After initial contact and attachment to a cell of the immune system (e.g. lymphocytes, monocytes), there is a cascade of intracellular events. The endproduct of these events is the production of massive numbers of new viral particles, death of the infected cells, and ultimate devastation of the immune system. However, the knot IS becoming unraveled. These pages attempt to simplify HIV infection at the cellular level. The following diagram shows a number of steps from initial attachment of a viral particle to a lymphocyte through budding of new viruses from that cell.
Human Immunodeficiency Virus (HIV)
Attachment to the Lymphocyte Membrane
On the surface membrane of all living cells are complex protein structures called "receptors". A receptor is often compared to a lock into which a specific key or "ligand" will fit. There are at least two receptors on T-lymphocytes to which the human immunodeficiency virus (HIV) sticks. The primary receptor, called "CD4", is shown on the right in the diagram. But a second receptor that loops through the cell membrane 7 times is critical for infection to occur.
HIV infection of a lymphocyte requires attachment of the virus to the cell membrane through both of these "ligand-receptor" links. In cells whose "7-transmembrane receptor" is different, the HIV "key" no longer matches the lymphocyte "lock" and attachment is incomplete. Those cells may avoid infection by HIV.
Entry of the Viral RNA
Tight attachment of the viral particle to receptors on the lymphocyte membrane enables fusion with the cell membrane. The viral contents, including viral RNA (shown in yellow) then empty into the cell's cytoplasm.Like other viruses that infect human cells, HIV commandeers the host's machinery to make multiple copies of itself.