Fig. 1.

Amplification using seminested reverse transcriptase PCR of poliovirus in primary and secondary concentrates. Lanes: 1 and 14, 1-kb ladder; 2 and 3, poliovirus-positive control in nuclease-free water (seeded with 10⁸ PFU/ml); 4 and 5, negative control (no virus); 6 and 7, poliovirus in NaPP eluting buffer (seeded with 10⁶ PFU/liter); 8 and 9, poliovirus recovered from the Centricon filter; 10 and 11, poliovirus recovered from the Centricon filter after the water rinse (end product); 12 and 13, poliovirus recovered from the Centricon filter after a desalting step (necessary for use with some cell culture lines).