CD4 and infection: Indeed, previous studies have demonstrated incorporation of host proteins, including integrins α4, αL, β7, β1, ICAM-1, and others into the viral envelope of virions propagated in human PBMCs.37,54–58 HIV virions bearing ICAM-157,59 and α4β754 have been shown to directly bind their cognate ligands on target cells to promote viral entry.39,60 As such, it is possible that virion-embedded host ICAM-1 could engage LFA-1 on target resting memory CD4+ T cells to facilitate infection.