Reduction of Postweaning Multisystemic Wasting Syndrome-Associated Clinical Symptoms by Virus-Like Particle Vaccine Against Porcine Parvovirus and Porcine Circovirus Type 2.

The porcine circovirus type 2 (PCV2) capsid (Cap) protein and porcine parvovirus (PPV) VP2 protein have been studied in vaccines to control postweaning multisystemic wasting syndrome (PMWS). Virus-like particle (VLP) vaccines are nonreplicative vectors that deliver epitopes and induce immune responses. However, most VLP vaccines are recombinant proteins expressed in eukaryotic systems and are expensive and complex. In this study, the full-length PCV2-Cap and PPV-VP2 proteins were expressed in Escherichia coli, which self-assembled into VLPs. The highly soluble proteins were purified using Ni-chelating affinity chromatography. The proteins self-assembled into VLPs of ∼20 nm (Cap VLP) and 25 nm (VP2 VLP) in diameter. The immunogenicities of Cap VLP and VP2 VLP were determined in piglets coinfected with PPV and PCV2 postimmunization. The results suggested that Cap VLP and VP2 VLP did not antagonize each other. The combined vaccine induced stronger humoral and cellular immune responses and provided the best protection against PPV and PCV2 coinfection. On a farm containing PMWS-infected pigs, the combined Cap VLP and VP2 VLP vaccine significantly improved piglet growth indices; the average daily weight gains were significantly higher than those of the Cap VLP vaccine and nonimmunized groups. Thus, Cap and VP2 protein expression in E. coli is feasible for large-scale VLP vaccine production. The combined vaccine may be a promising candidate vaccine for better preventing PMWS-associated diseases coinfected with PCV2 and PPV.