CXCL12 and coinfection: Moreover, in vitro GBV-C/HIV-1 co-infection of PBMCs results in increased expression and release of SDF-1, RANTES, MIP-1α, and MIP-1β chemokines, able to bind CXCR4 (SDF-1) and CCR5 (RANTES, MIP-1α, and MIP-1β) HIV-1 co-receptors, thus causing both co-receptors’ downmodulation at the cell surface [121].