Cell 137, 433–444 (2009)

HIV enters human cells through a more complex pathway than previously predicted.

Researchers had long thought that HIV binds to cell-surface receptors, and then fuses directly with the cell membrane, dumping its dangerous payload into the cell within about 10 minutes.

Gregory Melikyan and his colleagues at the University of Maryland School of Medicine in Baltimore show that successful infection includes an additional step, in which the virus becomes enveloped by membrane and internalized by the cell through a process called endocytosis. Thirty minutes to an hour can pass before the virus fuses with the internalized membrane and delivers its genetic material.

The findings may necessitate re-evaluation of drug candidates meant to block HIV's entry into cells.