Human Immunodeficiency Virus, more commonly known as HIV, is an RNA virus that converts RNA to DNA, making it a retrovirus. Retroviruses use single-stranded RNA as a template to make double-stranded DNA using a viral enzyme. HIV contains a protein that is called "reverse transcriptase" which is crucial for viral replication inside of T-cells. This eventually causes the immune system to shut down causing an extremely low tolerance to infectious diseases and eventual death.
Mechanisms of infection.
HIV is transmitted in several fashions. These routes of transmission include sexual contact with an infected individual; this is the most common route of transmission. HIV is also transmitted, in rare cases, through being stuck with a needle that has been used by an infected person. Additionally, a baby can contract the disease by being born to an infected mother or by breastfeeding from an infected woman.
HIV is an enveloped human retrovirus. The virion contains two copies of the RNA genome and three key enzymes: protease, integrase, and reverse transcriptase. The inner core of HIV consists of the p24 and p17 Capsid proteins. Clinical diagnosis of HIV infection involves detection of serum antibodies directed against the p24 Capsid protein. The Capsid is surrounded by the viral envelope, which is acquired when a nascent virion buds from an infected cell. As the virus leaves the cell, it is enveloped by the cellular membrane. Protruding from the envelope is the viral glycoprotein, gp160. Gp160 is made up of two component parts, gp120 and gp41, both of which play important roles in attachment and penetration of HIV into target cells (Andrian et al. 2000).
The infection process begins when gp120 binds to the principle receptor on the target cell, CD4. This induces conformational changes within the gp120 protein, which exposes a binding site for a co receptor. Many strains of HIV-1 exist, but most fit into one of two categories.