INVESTIGATION OF EFFECTS OF PORCINE CIRCOVIRUS TYPE 2 (PCV2) VACCINATION ON CELLULAR IMMUNITY IN PIGS IN A TAIWAN PIG FARM

Porcine circovirus type 2 (PCV2) is the major cause of serious porcine circovirus-associated diseases (PCVADs) causing significant economic losses in the pig industry. The PCV2 vaccines have proved effective by lowering serum and tissue viral loads. However, little is known about its effects on the cellular functions of viral target cells in pigs. For this, blood samples from 38 vaccinated and 34 non-vaccinated, 12–14 week-old, clinically healthy and PCV2-infected pigs in a commercial farm were sampled and anticoagulated. The viral load in plasma and the cellular proliferation and mRNA expression levels of IL-1 [Formula: see text], IL-2, IL-4, IL-8, IL-10 and IFN-[Formula: see text] of peripheral blood mononuclear cells (PBMCs) with or without concanavalin A (Con A) and PCV2 stimulation in vitro were then investigated by real-time polymerase chain reaction and flow cytometry. Compared with the non-vaccinated pigs, the average viral loads in the plasma and cultivated PBMCs were reduced in the PCV2-vaccinated pigs. Significant differences in the aspects of increased cell proliferation, decreased average viral loads in PBMCs three days after Con A stimulation, increased mRNA expression levels of IL-2 and IFN-[Formula: see text] after re-exposure to PCV2, and decreased levels of IL-1 [Formula: see text], IL-4 and IL-8 after Con A or PCV2 stimulation were also noted in the PCV2-vaccinated pigs. The results suggested that the PCV2-vaccinated pigs were likely to develop better cell-mediated immunity than the non-vaccinated pigs.