Key result
A novel Rep' protein indirect ELISA successfully distinguished whole-virus PCV2 exposure (100% Rep' positive) from subunit vaccine immunization (0% Rep' positive) in guinea pigs and piglets.
Why the study?
Existing commercial PCV2 ELISA kits detect Cap antibodies induced by both natural infection and vaccine immunization, preventing the diagnosis of PCV2 infection in immunized pig farms.
Absolute Event Rate: 100% vs 0%
An iELISA method based on the Rep' protein can effectively distinguish between natural PCV2 infection or whole-virus vaccination and subunit vaccine immunization in pigs.
Rep′ iELISA distinguishes PCV2 infection from subunit vaccination in pigs; leaves open routine adoption pending larger field validation.
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.
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Chen et al. (2020) studied Porcine circovirus type 2 (PCV2) infection. Rep' protein indirect ELISA (iELISA) vs. Commercial PCV2 Antibody Test kit was evaluated on Rep' antibody positivity in whole-virus vs subunit vaccinated animals. A novel Rep' protein indirect ELISA successfully distinguished whole-virus PCV2 exposure (100% Rep' positive) from subunit vaccine immunization (0% Rep' positive) in guinea pigs and piglets.
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