Development and evaluation of inactivated Porcine circovirus 2 vaccine using predominantly circulating genotypes in India

The present study aimed to develop and evaluate an inactivated porcine circovirus 2 (PCV2) vaccine using predominantly circulating genotypes under field conditions in India. The two most commonly circulating genotypes, PCV2d (INDTN07- BC3) and PCV2b (INDTNCHN56-4T), isolated and genotyped in southern India, were further propagated in PK-15 cells and titrated at the eleventh passage, with the titer of 106.3TCID50/ml and 105.4TCID50/ml for PCV2b and PCV2d, respectively. They were then inactivated using binary ethylenimine (BEI) and developed into individual genotype-specific inactivated PCV2 vaccines. The safety and immunogenicity of the developed inactivated PCV2b and PCV2d vaccines were evaluated individually through experimental trials in piglets. The post-vaccinal serum antibody response against PCV2 was measured using a commercial ELISA, and its neutralizing titer was measured through a fluorescent antibody virus neutralization assay (FAVN) at 21 days post-vaccination (dpv). The animals used in the immunogenicity study were further sub-grouped and kept as non-booster and booster groups within each vaccine group. In the booster group, the second dose of their respective inactivated PCV2 vaccine was given on the 28th day post-primary vaccination, and the duration of serum antibody response and neutralizing antibody response were evaluated for the period of 120 dpv. Both the genotype-specific inactivated PCV2b and PCV2d vaccines developed in this study were found to be safe and showed a significant rise in serum antibody response with the required neutralizing PCV2 antibody titer at 21 dpv. This response was maintained up to 120 dpv in both the booster and non-booster groups of both PCV2 vaccines when compared with the unvaccinated control group. Heterologous cross-protection of PCV2b vaccinated serum to the wild PCV2d genotype and vice versa was evidenced at 21 dpv for both vaccines.