FIG. 7.

Quantification of PRRSV RNA in serum samples. Prior to RT-PCR, dilutions of the competitor RNA were added to RNA extracted from serum from PRRSV-infected pigs. Equal amounts of RNA purified from serum were mixed with increasing amounts of competitor RNA. The results of RT-PCR following agarose gel electrophoresis are shown. Lanes 1 to 7, 0, 10, 50, 100, 500, 1,000, and 5,000 molecules of competitor RNA, respectively; lanes 8 and 9, results for negative (no template) and positive (PRRSV RNA) control reactions, respectively; lane M, DNA molecular size markers.