Introduction. PCV2 is
a DNA virus that exists widely in pigs and has caused great economic losses to the pig industry worldwide. In the existing commercial PCV2
enzyme-linked
immunosorbent assay (ELISA) kits both natural
infection with PCV2 and
vaccine immunization produce results that are positive for PCV2 Cap
antibodies and therefore they cannot diagnose PCV2
infection in immunized pig farms.Aim. To establish a PCV2 non-structural
protein antibody detection method that distinguishes between
antibodies resulting from natural prior exposure (
infection) and those induced by
subunit vaccine immunization.Methodology. Based on the non-structural Rep'
protein, we established an indirect ELISA (iELISA) using sera from guinea pigs and piglets.Results. The results for iELISA for guinea pig serum showed that animals vaccinated with a whole-virus inactivated PCV2
vaccine had 100 % (10/10) Cap antibody positivity and 100 % (10/10) Rep' antibody positivity. Guinea pigs vaccinated with a recombinant subunit PCV2
vaccine had 100 % (10/10) Cap antibody positivity, while no (0/10) guinea pigs were Rep' antibody-positive. The combined detection results for the Rep' iELISA and a PCV2 Antibody Test kit (Commercial) showed that pigs vaccinated with a whole-virus inactivated PCV2
vaccine or PCV2 SD/2017 had 100 % (5/5) Cap antibody positivity and 100 % (5/5) Rep' antibody positivity. Pigs vaccinated with a recombinant subunit PCV2
vaccine had 100 % (5/5) Cap antibody positivity, while no (0/10) pigs were Rep' antibody-positive.Conclusion. This paper describes an effective iELISA method that can distinguish natural
infection with PCV2 (Cap and Rep positive) or inoculation with a whole-virus
inactivated vaccine (Cap and Rep positive) from
subunit vaccine immunization (Cap-positive, Rep-negative). These comparative assays could be very useful in the control of PCV2 in pig herds.