CCR5 and HIV infectious disease: These positive effects of coreceptor signaling were also reflected in facilitating HIV infection of non-natural targets; the replication of some HIV-1 isolates in macaque cells was blocked at a step after entry and reverse transcription but prior to the nuclear import of the preintegration complex, and this block could be relieved by the expression of human coreceptor CCR5 or CXCR4 in macaque cells [59].