FIG. 7.

Levels of viral RNA in wild-type virus and in mutated viruses harboring substitutions at position 12 in p2. Levels of full-length viral RNA were assessed by RT-PCR through the use of primer pair pGAG1-pST (23). RNA samples were treated with DNase to remove any contaminating DNA. RNA samples were also digested with RNase A and then subjected to RT-PCR as a negative control to exclude the possibility of DNA contamination. A negative control of wild-type BH10 is shown in lane 1. RNA obtained from wild-type virus was diluted 1:2 and 1:4 before RT-PCR to ensure a linear range of these reactions (lanes 23 and 24). Additional controls were performed with wild-type DNA of 10¹, 10², 10³, and 10⁴ copies to determine the linear range of the reaction (lanes 25 to 28). The results represent three independent experiments. Band intensities were quantified with the NIH Image Program and plotted. The amount of BH10 RNA was arbitrarily set at 1.0.