Assessment of HTLV-II proviral DNA in TF-1 cell line by PCR amplification of a tax gene sequence. TF-1 cells treated with HTLV-II Mo strain derived from C344 T cells (lanes 3 and 5) or BJAB cells (lanes 2 and 4) were cultured for 3 days (lanes 4 and 5) or 7 days (lanes 2 and 3). DNA was extracted, amplified, and electrophoresed. Detection of the amplified product was performed by using a tax specific probe. Lane 1, negative control (untreated TF-1 cells); lane 6, positive control represented by PCR-amplified DNA from C344 T cells; lane 7, molecular weight markers.