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Table 4 Detection of virus in sera by isolation in porcine alveolar macrophages and by nested RT-PCR after the second challenge with PRRSV

From: Characterization of homologous and heterologous adaptive immune responses in porcine reproductive and respiratory syndrome virus infection

    Days post-2nd challenge Positive/total Viral titre ± standard deviation
Experiment Group Assay +7 (91 pi) +14 (98 pi)
1 C1 + B Viral isolation 2/2 2/2
3.2 ± 0.6 2.0 ± 0.0
nRT-PCR 2/2 2/2
A + A Viral isolation 0/4 0/4
nRT-PCR 4/4 1/4
A + B Viral isolation 0/4 0/4
   nRT-PCR 4/4 0/4
2 C2 + A Viral isolation 3/3 2/3
3.4 ± 0.9 2.2 ± 0.1
nRT-PCR 3/3 3/3
B + B Viral isolation 0/4 0/4
nRT-PCR 0/4* 0/4
B + A Viral isolation 0/4 0/4
   nRT-PCR 0/4* 0/4
  1. *Asterisks indicate statistical differences in the proportion of pigs found to be positive by RT-PCR in comparable groups of experiments 1 and 2 (i.e. homologous A + A versus homologous B + B).