DETECTION OF ANTIBODIES AGAINST PORCINE PARVOVIRUS NONSTRUCTURAL PROTEIN NS1 MAY DISTINGUISH BETWEEN VACCINATED AND INFECTED-PIGS

The humoral antibody response against the nonstructural protein NS1 an d the structural protein VP2 of porcine parvovirus (PPV) was evaluated by immuno-peroxidase test (IPT) and enzyme linked immune sorbent assa y (ELISA) using recombinant PPV antigens. The coding sequence for NS1 and VP2 was inserted into the baculovirus Autographa californica nucle ar polyhedrosis virus (AcNPV) genome resulting in two recombinant bacu loviruses AcNPV-NS1 and AcNPV-VP2, respectively. Sf9 cells (Spodoptora frugidiperda) inoculated with AcNPV-NS1 producing recombinant nonstru ctural protein (rNS1) and AcNPV-VP2 producing recombinant virion prote in (rVP2) were used in IPT and ELISA to analyse serum antibodies. Pigs vaccinated with an inactivated whole virus vaccine and experimentally infected pigs were studied. Significant titers against rVP2 were obta ined in both vaccinated and infected pigs. Specific antibodies against rNS1 could only be detected in infected pigs and NS1 may in this way allow the specific detection of infected animals. Analysis of serum sa mples collected up to 18 days post infection (p.i.) from four pigs exp erimentally infected with PPV showed that antibodies against rNS1 and rVP2 could in all cases be detected on day 9 p.i. Two individual pigs were inoculated twice with PPV and the antibody response was followed 89 days after second inoculation. Serum antibodies against both rVP2 a nd rNS1 could be detected for this period of time.