FIG. 4.

RT-PCR of limited numbers of BLV-infected cells. Twofold serial dilutions of cells were lysed and subjected to RT-PCR for BLV or β-actin transcripts. The actual numbers of cells in dilutions under 50 were confirmed visually and varied by no more than three cells. (A) Five samples at each dilution of ML cells were tested for tax/rex transcripts, two without and three with RT enzyme. The products of nested primers, 5′TR1 and 3′TR2, are 241 bp. (B) Samples were the same as in panel A but were amplified with nested β-actin primers 5′ACTN1 and 3′ACTN2, which yield a 165-bp product. (C) RT-PCR of lysates from serial twofold dilutions of NBC-13 cells with tax/rex-specific primers 5′TR1 and 3′TR2 (241 bp) or alt specific primers 5′ALT and 3′TR2 (89 bp). (D) Amplification of two BL3* cells as described for panel C. Southern blots were hybridized with X probe or actin probe (Table 1).