Comparison of Immune Responses to the PCV2 Replicase-Capsid and Capsid Virus-Like Particle Vaccines in Mice

Abstract

Porcine circovirus type 2 (PCV2) is the causative agent of postweaning multisystemic wasting syndrome (PMWS) in pigs. Replicase (Rep) proteins are considered essential for viral replication. Capsid (Cap) protein is the primary immunogenic protein that induces protective immunity. Little is known about comparison on the immunogenicity of PCV2 Rep and Cap fusion protein and Cap protein. In the present study, recombinant baculoviruses expressing the Rep-Cap fusion protein (Bac-Rep-Cap) and the Cap protein (Bac-Cap) of PCV2 were constructed and confirmed with western blot and indirect fluorescence assay. Immunogenicities of the two recombinant proteins were tested in mice. The titers of antibodies were determined with a PCV2-specific enzyme-linked immunosorbent assay (ELISA) and a serum neutralization assay. The IFN-γ response of immunized mice was measured by ELISA. The mice immunized with the Bac-Rep-Cap and Bac-Cap successfully produced Cap-specific immunoreaction. The mice immunized with the Bac-Cap developed higher PCV2-specific neutralizing antibody titers than mice injected with the Bac-Rep-Cap. IFN-γ in the Bac-Rep-Cap group was increased compared to those in the Bac-Cap group. Vaccination of mice with the Bac-Rep-Cap showed significantly decreased protective efficacy compared to the Bac-Cap. Our findings will indubitably not only lead to a better understanding of the immunogenicity of PCV2, but also improved vaccines.

Oral vaccination with the porcine circovirus type 2 (PCV‐2) capsid protein expressed byLactococcus lactisinduces a specific immune response against PCV‐2 in mice

“…Cap protein‐based PCV2 subunit vaccines that were produced in the baculovirus system were able to elicit both humoral and cellular immune responses (Wang et al ; Jeong et al ). It had been proved that Cap virus‐like particle vaccine could induce more effective PCV2‐specific immune responses than Replicase‐Cap fusion protein (Jung et al ). The PCV2 Cap protein was expressed in the nonconventional yeast Kluyveromyces marxianus could elicit high levels of anti‐PCV2 IgG antibody and reduce the virus titres both in liver and spleen tissues of PCV2 strain‐challenged mice (Duan et al ).…”

Production of virus-like particles of porcine circovirus type 2 in baculovirus expression system and its application for antibody detection

“…In order to achieve this, the test was adjusted at a coated antigen concentration of 2 µg/mL. This is lower than the 4 µg/mL optimized by Jung et al [39], indicating a stronger antigenicity of the recombinant protein generated in our work. Cross-reactivity testing was used to determine the analytical speci city, and the results show that I-ELISA is PCV2 speci c. The indirect ELISA cutoff value in the current investigation was 0.438, determined from the Mean + 3SD.…”

Production of virus-like particles of porcine circovirus 2 in baculovirus expression system and its application for antibody detection

“…A good ELISA detection is evaluated by its repeatability, high sensitivity and specificity. To this end, the less coating antigen PCV-2 VLPs (2 μg/mL) was used in this ELISA compared with 4 μg/mL by Jung et al [ 40 ]. Analytical specificity was assessed using cross-reactivity testing, and the findings indicate that I-ELISA is PCV-2 specific.…”