CCR5 and HIV infectious disease: BLT mice were infected intravenously with HIV-1JRC-SF (n = 3), an early passage CCR5-tropic primary isolate that has been extensively characterized in this model (64) or with HIV-1CH040 (n = 3), a CCR5-tropic transmitted/founder virus (3 × 104 tissue culture infectious units (TCIU)) that initiated a natural HIV infection (54).