Complexity in human immunodeficiency virus type 1 (HIV-1) co-receptor usage: roles of CCR3 and CCR5 in HIV-1 infection of monocyte-derived macrophages and brain microglia

CCR3 has been implicated as a co-receptor for human immunodeficiency virus type 1 (HIV-1), particularly in brain microglia cells. We sought to clarify the comparative roles of CCR3 and CCR5 in the central nervous system (CNS) HIV-1 infection and the potential utility of CCR3 as a target for manipulation via gene transfer. To target CCR3, we developed a single-chain antibody (SFv) and an interfering RNA (RNAi), R3-526. Coding sequences for both were cloned into Tag-deleted SV40-dervied vectors, as these vectors transduce brain microglia and monocyte-derived macrophages (MDM) highly efficiently. These anti-CCR3 transgenes were compared to SFv-CCR5, an SFv against CCR5, and RNAi-R5, an RNAi that targets CCR5, for the ability to protect primary human brain microglia and MDM from infection with peripheral and neurotropic strains of HIV-1. Downregulation of CCR3 and CCR5 by these transgenes was independent from one another. Confocal microscopy showed that CCR3 and CCR5 co-localized at the plasma membrane with each other and with CD4. Targeting either CCR5 or CCR3 largely protected both microglia and MDM from infection by many strains of HIV-1. That is, some HIV-1 strains, isolated from either the CNS or periphery, required both CCR3 and CCR5 for optimal productive infection of microglia and MDM. Some HIV-1 strains were relatively purely CCR5-tropic. None was purely CCR3-tropic. Thus, some CNS-tropic strains of HIV-1 utilize CCR5 as a co-receptor but do not need CCR3, while for other isolates both CCR3 and CCR5 may be required.