Comparison of Two Inactivated Vaccines Against Infectious Bronchitis Virus Evidences the Interference of Vaccine Formulations on Vaccine Performance
Comparison of Two Inactivated Vaccines Against Infectious Bronchitis Virus Evidences the Interference of Vaccine Formulations on Vaccine Performance
Lucas Pedroso Colvero1, Paulo Eduardo Brandão2*, Cesar Alejandro Rodriguez Rosales2, Hanny Swam3 and Laura Yaneth Buitrago Villarreal1
ABSTRACT
Inactivated water-in-oil vaccines are widely used to control viral diseases in poultry, however, the interference of physico-chemical properties of the emulsions are overlooked when compared to antigenic properties. This study was designed to assess the effect of two different commercial inactivated water-in-oil multivalent vaccines; vaccine A contains IBV (Massachusetts M41 and D274 strains), NDV (Clone 30), aMPV (BUT 8544) and IBDV (classic strain) whereas vaccine B contains IBV (Massachusetts M41 and a Brazil type strain), NDV (LaSota strain), aMPV (TRT strain) and IBDV (GP82 strain). Viscosity values for vaccines A and B where determined to be 40.2cP and 83.3cP, respectively, and a microscopic examination showed that vaccine A has a homogeneous emulsion, whereas vaccine B has a highly heterogeneous appearance. Birds vaccinated with vaccine A showed mean ELISA antibody S/P ratios from 0.099 to 0.995 between weeks 2 and 6 post-vaccination against IBV antigen, while for vaccine B group mean S/P ratio dropped to 0.550 at week 6. Virus neutralization test showed that birds vaccinated with vaccine A showed neutralizing antibodies against IBV Massachusetts, 4/91, D274 and Qx types, while titers for vaccine B were not detected, suggesting a role of the poor emulsion quality on the performance of vaccine B. These results demonstrate that effective quality control and emulsion preparation are essential benchmarks of immunization and vaccine potency.
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