“…The major coreceptor for the macrophage-tropic, nonsyncytium-inducing (NSI) viruses, now designated R5 isolates, was found to be CCR5 (2,20,22,27,28). A plethora of other coreceptors has also been described to function for HIV-1 entry, especially for SI viruses, at least in the context of coreceptor-transfected cells in vitro (5,19,20,22,27,31,32,38,40,50,60,62,84,85,92,93,96,102,104,105,116).…”