Representative gel of subtype-specific PCR for HIV-1. Symbols indicate the primers used: Bg; β-globin. H; subtype-independent PCR for HIV-1; A, B, C; respectively, HIV-1 subypes A, B and C. The first and last lanes represent 50 bp molecular weight ladder. Two panels are shown, i.e., PCR amplification from known HIV positive and HIV negative subjects. In the HIV negative subject, only the β-globin gene was amplified. In the HIV positive sample, products were observed for subtype-independent (H), and HIV-1 subtype A specific PCR. A faint band is observed in lane B, but, as explained in Material and Methods, this band was disregarded due to its significantly low intensity as compared to the band in H (and A).