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Table 3 Detection of virus in sera by isolation in porcine alveolar macrophages and by nested RT-PCR after first challenge with PRRSV

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

   Days post 1st inoculation (pi)
Experiment Assay 7 14 21 28 35 42 49 56 63 70 77 84
1 Viral isolation (titre) 14/14 11/14 4/11 1/11 0/11 0/8 0/8 0/8 0/8 0/8 0/8 0/8
  3.1 ± 0.6 2.9 ± 0.5 2.3 ± 0.2 2.3 ± 0.0 - - - - - - - -
  nRT-PCR 14/14 11/14 4/11 1/11 0/11 0/8 0/8 0/8 0/8 0/8 0/8 0/8
2 Viral isolation (titre) 8/8 8/8 7/7††* 7/7* 7/7* 3/7* 3/7* 1/7* 0/7 0/7 0/7 0/7
  3.7 ± 0.3 3.4 ± 0.5 3.2 ± 0.8 2.6 ± 0.5 2.2 ± 0.2 2.0 ± 0.3 2.0 ± 0.3 1.8 ± 0.0 - - - -
  nRT-PCR N.D. N.D. N.D. N.D. N.D. 4/7 4/7 3/7 0/7 0/7 0/7 0/7
  1. Results of viral titration of sera in porcine alveolar macrophages (PAM) using the immunoperoxidase monolayer assay are expressed as number of positive pigs over the number of pigs in the group and as the mean ± standard deviation (log10) of titres (TCID50/mL) of positive pigs. *p < 0.05 for the comparison of infected groups between experiment 1 (strain 3262) and 2 (strain 3267). For the nRT-PCR results only show the number of positive pigs in the second round of the PCR. Results of control (uninoculated) pigs are not shown because they were always negative from day 0 to 84 post-inoculation.
  2. Three pigs were euthanized at day 15 pi and three pigs more were killed at day 35 pi.
  3. †† One pig died at day 17 pi.
  4. N.D. Not done