The Molecules of HIV

Note: this site last updated in 2006

HIV life cycle

An article from "The Molecules of HIV" (c) Dan Stowell

The HIV life-cycle is the story of how a single HIV virus particle infiltrates a cell and uses it to produce new HIV particles.

This isn't the whole story about HIV, of course. In order for a person to become infected with HIV, one or more virus particles must enter the body. These particles will be borne in fluid such as blood or semen, since the HIV virus cannot survive on its own outside the body.

Once inside the body they need to find their way to susceptible cells, where the HIV life-cycle proper begins.

Which sort of cells does HIV go for? Any cell carrying the CD4 protein on its surface (which we call a CD4+ cell) is susceptible, since CD4 is the main receptor for HIV. Different strains of HIV target different cells - but T cells and macrophages, both of which are CD4+, are two important targets for HIV.

Infiltrating a cell

The first step of the HIV life cycle is binding to the cell membrane, followed by membrane fusion, to get the virus particle's contents into the host cell.

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Then follows reverse%20transcription">reverse transcription of the HIV's genome from RNA into DNA, and its integration into the host genome.

Producing new virus

Once integrated the virus can lie low in human cells, or can begin the RNA%20and%20proteins">production of new viral RNA and proteins, turning the cell into a HIV factory. This production is followed by assembly, budding, and maturation, in which the new HIV particles are packaged up and sent out to infect new cells.

An excellent animation of the HIV life-cycle is available at

Written by
Dan Stowell

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