Effect of different baculovirus inactivation procedures on the integrity and immunogenicity of porcine parvovirus-like particles

We have demonstrated earlier the usefulness of recombinant porcine parvovir us (PPV) virus-like particles (VLPs) as an efficient recombinant vaccine fo r PPV. Here, we have demonstrated that preparations of PPV VLPs could be co ntaminated by recombinant baculoviruses. Since these baculoviruses can be a problem for the registration and safety requirements of the recombinant va ccine, we have tested different baculovirus inactivation strategies, studyi ng simultaneously the integrity and immunogenicity of the VLPs. These metho ds were pasteurization, treatment with detergents and alkylation with binar y ethylenimine (BEI). The structural and functional integrity of the PPV VL Ps after the inactivation treatments were analyzed by electron microscopy, hemagglutination, double antibody sandwich (DAS)-ELISA and immunogenicity s tudies. Binary ethylenimine:and Triton X-100 inactivated particles maintain ed all the original structural and antigenic properties. In addition, PPV V LPs were subjected to size-exclusion chromatography to analyze the presence of VP2 monomers or any other contaminant. The resulting highly purified ma terial was used as the standard of reference to quantify PPV VLPs in order to determine the dose of vaccine by DAS-ELISA. After immunization experimen ts in guinea pigs, the antibody titers obtained with all the inactivation p rocedures were very similar. Triton X-100 treatment was selected for furthe r testing in animals because of the speed, simplicity and safety of the ove rall procedure. (C) 2000 Elsevier Science Ltd. All rights reserved.