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Comparison of the Efficacy of Autogenous Inactivated PRRSV Vaccines with Commercial Vaccines

18 October 2012, at 12:00am

Experimental homologous inactivated vaccines and commercial attenuated vaccines shortened the viraemic phase following challenge with two field isolates of the porcine reproductive and respiratory syndrome virus (PRRSV), according to researchers based in Belgium. Experimental heterologous inactivated vaccines and the commercial inactivated vaccine, however, had little impact on the period of virus shedding.

The porcine reproductive and respiratory syndrome virus (PRRSV) is a rapidly evolving pathogen of swine. At present, there is a high demand for safe and more effective vaccines that can be adapted regularly to emerging virus variants, according to Marc F. Geldhof of Ghent University in Belgium and co-authors at KATHO Catholic University College of South-West Flanders in Roeselare.

In their paper published recently in BMC Veterinary Research, they report that a recent study showed that, by the use of a controlled inactivation procedure, an experimental BEI-inactivated PRRSV vaccine can be developed that offers partial protection against homologous challenge with the prototype strain LV. At present, they said, it is unknown if this vaccine can be adapted to currently circulating virus variants.

In their study, two recent PRRSV field isolates (07 V063 and 08 V194) were used for BEI-inactivated vaccine production. The main objective of the experiments was to assess the efficacy of these experimental BEI-inactivated vaccines against homologous and heterologous challenge and to compare it with an experimental LV-based BEI-inactivated vaccine and commercial inactivated and attenuated vaccines. In addition, the induction of challenge virus-specific (neutralizing) antibodies by the different vaccines was assessed.

In a first experiment (challenge with 07 V063), vaccination with the experimental homologous (07 V063) inactivated vaccine shortened the viraemic phase upon challenge with approximately two weeks compared to the mock-vaccinated control group. Vaccination with the commercial attenuated vaccines reduced the duration of viraemia with approximately one week compared to the mock-vaccinated control group. In contrast, the experimental heterologous (LV) inactivated vaccine and the commercial inactivated vaccine did not influence viraemia. Interestingly, both the homologous and the heterologous experimental inactivated vaccine induced 07 V063-specific neutralizing antibodies upon vaccination, while the commercial inactivated and attenuated vaccines failed to do so.

In the second experiment (challenge with 08 V194), use of the experimental homologous (08 V194) inactivated vaccine shortened viraemia upon challenge with approximately three weeks compared to the mock-vaccinated control group. Similar results were obtained with the commercial attenuated vaccine. The experimental heterologous (07 V063 and LV) inactivated vaccines did not significantly alter viraemia. In this experiment, 08 V194-specific neutralising antibodies were induced by the experimental homologous and heterologous inactivated vaccines and a faster appearance post challenge was observed with the commercial attenuated vaccine.

In conclusion, Geldhof and co-authors report that the experimental homologous inactivated vaccines significantly shortened viraemia upon challenge. Despite the concerns regarding the efficacy of the commercial attenuated vaccines used on the farms where the field isolates were obtained, use of commercial attenuated vaccines clearly shortened the viraemic phase following challenge. However, the experimental heterologous inactivated vaccines and the commercial inactivated vaccine had no or only a limited influence on viraemia.

The observation that homologous BEI-inactivated vaccines can provide a more or less standardised, predictable degree of protection against a specific virus variant suggests that such vaccines may prove useful in case virus variants emerge that escape the immunity induced by the attenuated vaccines, added the researchers.

Reference

Geldhof M.F., M. Vanhee, W. Van Breedam, J. Van Doorsselaere, U.U. Karniychuk and H.J. Nauwynck. 2012. Comparison of the efficacy of autogenous inactivated Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) vaccines with that of commercial vaccines against homologous and heterologous challenges. BMC Veterinary Research, 8:182. doi:10.1186/1746-6148-8-182

Further Reading

You can view the full report (as a provisional PDF) by clicking here.

Find out more information on porcine reproductive and respiratory syndrome (PRRS) by clicking here.



October 2012