Integration of HIV-1 into the genome occurs efficiently in infected rat cells. (A) Parental Rat2 cells and HeLa cells were exposed to VSV-G pseudotyped HIV-1 GFP vectors and cultivated for 7 days. The relative levels of total HIV-1 cDNA, 2-LTR circles, and integrants were quantified by specific real time PCR in extracts from cell aliquots taken at the indicated time points. All copy numbers per ng DNA are depicted relative to the levels of total HIV-1 cDNA on day 1 after infection, levels of which were arbitrarily set to 100%. (B) Three hCD4/hCCR5-transgenic rats and one hCCR5-single-transgenic rat were challenged intravenously with HIV-1YU-2. On day 4, all animals were sacrificed and spleens removed. The levels of all three HIV-1 cDNA species were quantified in splenocytes extracts relative to a rat GAPDH standard by real-time PCR. Results are presented as the arithmetic mean ± S.E.M. of data obtained for the three double-transgenic rats.