HIV-1 DNA detection in TH1 and TH2 clones. Lysates were prepared at 10 and 24 h p.i. A primer pair was used to detect the earliest region of DNA formed by reverse transcription (141 bp of the minus strong-stop strand). Another primer pair was used to detect full-length HIV-1 DNA (200 bp of LTR-gag) and human β-globin. The sense primers of each pair were radiolabeled. Two different TH1 (H1.20 and H1.25) and TH2 (H2.10 and H2.25) clones are shown. Lanes: A, control; B, SF162 infection; C, US657; D, US714; E, US727. Tenfold serial dilutions of the ACH-2 cell line, containing one integrated copy of HIV-1 DNA per cell, were made in a background of uninfected T cells and shown for estimation of copy number.