CD4 and infection: The neurotropic, neurovirulent SIVmac17E-Fr strain initially characterized extensively in macaque models of HIV (Clements et al., 2002; Edinger et al., 1997; Flaherty et al., 1997; Mankowski et al., 1997) has been demonstrated to lead to infiltration in the brain, where infection of microglial/macrophage-related cells represents a reservoir for the virus in a CD4-independent manner.