engleski

Development of live attenuated vaccine against infectious bronchitis virus according to current European regulative.

Infectious brochitis of fowls is higly contagious disease of respiratory and urogenital tract of birds. Causative agent of the disease is infectious bronchitis virus (IBV). Due to significant losses the disease causes in poultry production worldwide, strict biosecurity and prophylactic measures are undertaken. There are many different live attenuated and inactivated vaccines against IBV present on the market nowadays, based on several different vaccine strains. The most widely used live attenuated vaccine against IBV contains strain H120 which belongs to Massachusetts serotype and is present on the market more than 50 years. European pharmacopoeia (Ph.Eur.) together with other relevant EU regulative strictly prescribe safety and efficacy tests and criteria which a vaccine needs to comply to be granted a marketing authorisation across EU. We have developed a live attenuated vaccine against IBV based on H120 vaccine strain. Safety tests were performed in SPF chickens where it was shown that even after 6 passages in chicks, our vaccine strain does not revert to virulence. Furthermore, in the dissemination and spreading test IB H120 was able to spread at least 3 times between groups of IB naïve SPF-chickens, without inducing morbidity and mortality. H120 was detected in trachea, spleen, kidney, lung, caecal tonsil and jejunum without causing pathological changes in these organs. H120 vaccine is most frequently administered to chicks during their first week of life. At this age, level of maternally derived antibodies is still very high which may hamper the development of active immunity. In our research, the efficacy of IB H120 vaccine was assessed in broiler chickens with and without MDA to IB virus. Chicks were vaccinated by spray, eye-nose-drop, or orally or were left unvaccinated. At three different time points after vaccination, protection against M41 challenge was determined. The results have shown that onset of immunity starts already 10 days after vaccination. Judged by protection level achieved, there was no influence of MDAs on the vaccination by any of the administration methods tested. Safety and efficacy of the vaccine was confirmed also in field conditions, on broiler farm in France and layer farm in Slovenia. Production results were comparable to those achieved by already marketed IBV vaccine with same indication, showing that our IB H120 vaccine was safe and efficacious also in field conditions.

infectious bronchitis virus, vaccination, maternally derived antibodies

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