CCR5 and infection: We then included the HIV-entry blocker T-20 (Enfuvirtide), a small peptide that binds to the HIV gp41 heptad repeat and inhibits the structural changes necessary for the virus to fuse with CD4+ T cell - and Maraviroc (Selzentry), an entry inhibitor that specifically blocks chemokine receptor CCR5 that HIV uses as a co-receptor to bind and enter human helper T cells - in the culture to exclude HIV entry and infection of cells.