Analysis of viral circle junctions in cells isolated from chronically infected cats. Genomic DNA purified from freshly isolated PBMC samples prepared from FIV-infected cats up to 14 weeks PI were tested for viral episomal circular LTR DNA by standard PCR assays (CJ primer set A) designed to detect circular forms of vDNA (a). Circle junction PCR amplicons representative of either single LTR (arrow) or double LTR circles (arrowhead) were generated from in vitro FIV-infected feline PBMCs (lane 1; positive control) and were absent in the negative control using a water template (lane 2). Circle junction PCR reactions with expected PCR amplicons of 1423 bp (single LTR, arrow) and faint 1820 bp (double LTR, arrowhead) are shown for PBMCs from cats 184, 186 and 187 sampled at 4 wks PI (lanes 3, 4 and 5); 6 wks PI (lanes 6, 7 and 8); 9 wks PI (lanes 9, 10, 11); and 14 wks PI (lanes 12, 13 and 14), respectively. PCR products from standard PCR reactions for 18s rRNA (b) from samples in the same corresponding lanes in (a), reveal positive, appropriately sized bands (~140 bp) except for lane 2 (water template negative control).