Detection of challenge virus in fetal tissues by nested PCR as a test of the potency of a porcine parvovirus vaccine.

摘要

To estimate the potency of a porcine parvovirus (PPV) vaccine, 3 vaccinated and 3 non-vaccinated pregnant gilts were infected with PPV and the distribution of the virus was studied in the tissues of their 51 fetuses. Virus detection was attempted using haemagglutination (HA) and immunofluorescence (IF) assays, as well as by standard (single) and nested polymerase chain reactions (PCR). None of the detection methods yielded positive results when used to test for virus in suspensions of organs from the fetuses from the vaccinated gilts. The virus was detected in the fetuses from non-vaccinated gilts as follows: HA was positive in 14 of 23 (60.8%), IF in 16 of 23 (69.5%), standard PCR in 12 of 20 (60%), and the nested PCR in 19 of 23 (82.6%). Although the correlation among the results of various methods of virus detection was rather close (r < 0.83), the sensitivity of the nested PCR was the highest, both when testing dilutions of PPV and when examining the fetal organs. The nested PCR therefore provides a reliable approach for studies of virus distribution in fetal organs, with special reference to potency tests on vaccines.