Development of novel iron-regulated Pasteurella multocida B: 2 bacterin and refinement of vaccine quality in terms of minimum variation in particle size and distribution vis-a-vis critical level of iron in media.

To enhance the qualitative bacterial biomass per unit of media and to overcome the limitations of the existing haemorrhagic septicaemia (HS) vaccines, a comprehensive study was undertaken encompassing the role of iron on the bacterial biomass of Pasteurella multocida B: 2 to vaccine development. Trypsin digested hydrochloric acid-treated sheep blood (THSB) as a novel iron rich supplement had been devised for the first time for augmenting the qualitative bacterial biomass per unit of media which was evident with growth kinetic study. The higher recovery of iron from THSB became evident via atomic absorbance spectrophotometry. The critical level of iron in the media as well as mode of iron supplementation showed a major impact on the outer membrane protein profile of P. multocida B:2 and variation in droplet size and particle-size distribution of formulated vaccine. Immune response study against iron-regulated bacterin adjuvanted with aluminum hydroxide gel in mouse model showed that 3% THSB supplementation of casein sucrose yeast (CSY) not only augmented the growth of P. multocida B:2 significantly but conferred highest pre-challenged ELISA IgG titer and protection against pasteurellosis. Thus, THSB supplementation of CSY can resolve existing up-scaling and immunogenic potential problems of HS vaccine production.