Evaluation of novel inactivation method of PRRSV for vaccine production

Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically important animal virus that causes reproductive failure and respiratory track illness in pigs. Current inactivated vaccines have low efficacy and/or complicated time-consuming production procedure requiring application of hazardous reactants such as formaldehyde or binary ethylenimine. Here, we studied the possibility of hydrogen peroxide (H₂O₂) as a suitable alternative for inactivated vaccine preparation.

Inactivation procedure was performed by incubation of North American PRRSV strain NADC-20 solution with different concentrations of H₂O₂ in various environmental conditions and evaluated its virucidal efficacy at two time points. In-vitro studies with MARC-145 cells, inoculated with inactivated viral solutions, demonstrate successful inactivation of virus with the absence of cytopathic effect even at very low H₂O₂ concentration of 0.5% after 1 hour of inactivation procedure.

Cell proliferation assay was performed to confirm the results from microscopic observations. It was also found that catalase from bovine liver is more suitable reagent for removal of residual H₂O₂ from viral solution than iron (lll) chloride, because it maintains neutral pH and it is biocompatible with living cells.We also observed that H₂O₂-inactivated PRRSV have similar immunogenicity pattern as live virus in a western blot analysis using serum from pigs infected with wildtype PRRS virus.

Our studies suggest that H₂O₂-inactivated virus can be a promising candidate for further in-vivo investigation to confirm its efficacy in creating adequate immune protection. Efficacy study of PRRS vaccine prepared with this new inactivation method is ongoing and will be reported at this meeting.

Disclosure of Interest: None Declared.