Potentiation of Porcine Circovirus 2-induced Postweaning Multisystemic Wasting Syndrome by Porcine Parvovirus Is Associated with Excessive Production of Tumor Necrosis Factor-α

This study investigated the potentiation of porcine circovirus 2 (PCV2)-induced postweaning multisystemic wasting syndrome by porcine parvovirus (PPV) and found it was associated with excessive production of tumor necrosis factor-a (TNF-a). Colostrum-deprived conventional pigs were inoculated intranasally with PCV2 or PPV alone or in combination (PCV2 and PPV). In vitro assay of TNF-a, obtained from alveolar macrophages coinfected with PCV2 and PPV, showed a significant increase in TNF-a compared to single infection of macrophages with either PCV2 or PPV alone (P , 0.05). All pigs inoculated with PCV2 and PPV developed severe postweaning wasting syndrome, whereas clinical signs (e.g., weight loss) were present but perhaps less severe in either PCV2- or PPV-inoculated pigs. Compared to the pigs inoculated with PCV2 or PPV alone, pigs inoculated dually with PCV2 and PPV showed significantly (P , 0.05) increased levels of TNF-a. Levels of TNF-a in the sera were reversely correlated with the body weight in pigs experimentally infected with dual inoculation of PCV2 and PPV (rs 52 0.92, P , 0.001). These data suggest that a potentiation of PPV in PCV2-induced PMWS is associated with the excessive production of TNF-a.