Fusion of HIV with a target cell

The gp120 molecule of HIV first interacts with the CD4 antigen of the target cell.

Heparan sulfate proteoglycan stabilizes the interaction of the gp120 with CD4 antigen

This interaction induces a conformational change in the gp120 exposing sites that interact with the chemokine receptor (CCR5 or CXCR4)

This further stablizes the interaction and the virus fusion protein (gp41) is uncovered and also undergoes a conformational change

Gp41 inserts into the membrane of the host cell to initiate the fusion of the two bilayers  

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