CD4 and HIV-1 infection: Therefore the high susceptibility of humanized DRAG mice to HIV-1 infection after intravaginal inoculation is likely related to (i) the high reconstitution of human cells in the female reproductive tract; (ii) the dominance of CD4+ T cell memory phenotype in gut tissues and FRT, (iii) the high levels of expression of HIV-1 coreceptors, and (iv) the accumulation of TFH cells in the gut and FRT.