Data shows that chronic morphine treatment in the presence of HIV-1 Tat resulted in significant CNS trafficking of Ly6C+CCR5+ and Ly6C+CXCR4+ following co-infection with systemic S. pneumoniae infection, an effect that was significantly attenuated in both TLR2KO and TLR4KO mice. This evidence concerns the gene CCR5 and coinfection.