Abstract
BackgroundPorcine circovirus type 2 (PCV2) is associated with post-weaning multisystemic wasting syndrome (PMWS), an emerging swine disease that causes progressive weight loss, dyspnea, tachypnea, anemia, jaundice, and diarrhea in piglets. Although baculovirus is an enveloped virus that infects insects in nature, it has emerged as a vaccine vector, and we used it to develop a novel candidate vaccine for a preventive or therapeutic strategy to control PCV2 infections.MethodsImmunoblotting analysis of recombinant baculovirus and immunofluorescent staining of baculovirus-infected cells were followed using anti-ORF2 monoclonal antibodies. The BALB/c mice were immunized intramuscularly with this baculovirus. The titers of antibodies were mensurated with a Cap-protein-specific enzyme-linked immunosorbent assay (ELISA) and a serum neutralization assay. The IFN-γ response in splenocytes harvested from immunized mice was measured by ELISA. Student's t-test was used to compare immune responses of different groups.ResultsIn this study, we successfully constructed a dual-expression-system-based recombinant baculovirus BV-GD-ORF2, which can display the PCV2 capsid (Cap) protein and VSV-G protein on the viral envelope and also expressing Cap protein on transduced mammalian cells, thereby functioning as both a subunit and a DNA vaccine. After infection, the Cap protein was expressed and displayed on the viral surface, as demonstrated with an indirect fluorescence assay and immunoblotting. The vaccination of mice with recombinant baculovirus BV-GD-ORF2 successfully induced robust Cap-protein-specific humoral and cellular immune responses.ConclusionsOur findings collectively demonstrate that the recombinant baculovirus BV-GD-ORF2 is a potential vaccine against PCV2 infections.
Highlights
Porcine circovirus type 2 (PCV2) is associated with post-weaning multisystemic wasting syndrome (PMWS), an emerging swine disease that causes progressive weight loss, dyspnea, tachypnea, anemia, jaundice, and diarrhea in piglets
Robust humoral and cellular immune responses were successfully induced in mice immunized with the recombinant baculovirus BV-GDORF2. These results suggest that a PCV2 vaccine based on the baculovirus dual expression system can be used as an alternative strategy to protect against PCV2 infection
To investigate whether the Cap protein was displayed on the membrane of BV-GD-ORF2, the purified viral particles were analyzed with immunoblotting with an anti-ORF2 monoclonal antibody
Summary
Porcine circovirus type 2 (PCV2) is associated with post-weaning multisystemic wasting syndrome (PMWS), an emerging swine disease that causes progressive weight loss, dyspnea, tachypnea, anemia, jaundice, and diarrhea in piglets. AcMNPV has been further engineered for use as a new eukaryotic display system to express exogenous peptides on the surface of the viral envelope. This display strategy relies on thegp protein, which is the major envelope protein of the baculoviruses, which has an amino-terminal signal peptide (SP), a mature transmembrane domain (TM) and a cytoplasmic tail domain (CTD). After its expression with the native gp, the fusion protein is translocated to the plasma membrane and incorporated into the baculoviral envelope This method has been extended to develop pseudotyped baculoviruses as a potential vaccine delivery platform. Several research groups have demonstrated that direct vaccination with pseudotyped baculoviruses can induce high titers of antigen-specific antibodies [14,15,16]
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