CCR5 and infection: ,4,53 However, inactivation of the CCR5 does not prevent infection with CXCR4-tropic and dual-tropic viruses and is likely to select for variants that can utilize the CXCR4 coreceptor,8,54 suggesting a need for strategies to suppress infection with CCR5-, CXCR4-, and dual-tropic viruses.