CD4 and HIV-1 infection: Consistent with the immunostaining data, active HIV-1 infection was also confirmed by quantifying de novo HIV-1 DNA in infected primary CER (Fig. 2D) and VAG (Fig. 2E) epithelial cells exposed to HIV-1 IIIB–HTLV-1- or HIV-1 Bal–HTLV-1-coinfected primary CD4+ T cells and by quantifying HIV-1 release into culture supernatants from epithelial cells exposed to HIV-1 Bal–HTLV-1-coinfected PM1 cells (Fig. S3D).