HIV Animation

AIDS is caused by infection with a virus called the Human Immunodeficiency Virus type 1 or HIV 1. This virus has an outer envelope, or membrane covered in spikes made of the proteins gp120 and gp41. Just below is a layer of protein called the matrix. A protein coat or capsid covers the components needed for replication -- 3 enzymes called reverse transcriptase, integrase, and protease and 2 strands of ribonucleic acid or RNA, which carry genetic information.

HIV 1 infects cells of the immune system, such as helper T cells and macrophages, which are critical to the body's defense against viral invasion and infection. The proteins gp120 and gp41 on the surface of the virus called attach to receptors on the surface of the target cell. The HIV RNA and enzymes enter the target cell through a microtubule.

As the virus enters the target cell, it leaves its membrane behind as part of the cellular membrane. The viral enzyme reverse transcriptase creates a sequence of viral DNA (which is compatible with human genetic material) from the viral RNA.

The viral RNA is then degraded and the viral DNA is then copied into double stranded viral DNA.

The virus's genetic information, now in the form of double-stranded DNA, moves to the host cell nucleus. The host DNA is split and the viral genome is inserted into it through the action of the viral protein, integrase.

The host cell converts the HIV genes into RNA, which exits the nucleus and becomes a blueprint for new viral proteins and enzymes. These, with copies of HIV genetic material, form new viral particles. They bud from the cell surface, with an envelope formed from the host cell membrane.

As many as 10 billion HIV virus particles are produced a day in an infected person.