Sharma, R. K.Gogoi, Anamika2022-07-012022-07-012020-01https://krishikosh.egranth.ac.in/handle/1/5810185037The Fowl Cholera, an infectious disease of poultry, waterfowl and many other birds is caused by Pasteurella multocida. To overcome those hurdles in poultry industry, focus has been given to identify immunogenic subcomponent of the causative agent and their use in development of modern vaccines. The present study was undertaken with a view to evaluate immunogenic potential of Outer Membrane Vesicles (OMVs) of Pasteurella multocida as well as their release under the influence of various environmental and physico-chemical factors. The extraction of OMV fraction was made from a highly pathogenic strain of P. multocida capsular type A associated with Fowl Cholera. The release of OMVs by the selected isolates was found to be significantly (p˂0.001) highest under the influence of iron deficient condition (2, 2 bipyridyl), exhibiting a protein concentration of 18.3 mg/ml. Similarly, the influence of pH in iron restricted environment was also have an impact on OMV release, which was found to be significant (p˂0.05) in reverse direction. A positive correlation could also be made in respect to the oxidative and antibiotic stress with release of OMVs. The comparative protein profiling of OMVs, OMPs and whole cell lysate of the selected pathogenic P. multocida type A isolate could exhibit more distinct and prominent protein bands in OMV fraction. The OMV fraction could also reveal the ompA (37.7-38.1 kDa), which was not prominently observed in other two fractions. The immunogenic potential of the extracted OMV fraction revealed an increasing trend of the mean antibody titre in both the immunized groups, with (Group I) or without (Group II) booster. The immunized birds of group I exhibited a significantly rising trend (p<0.05) of the mean serum antibody titre from the day of the vaccination, until it reached its peak (5947.41±62.6). The peak titre was observed on 28th day of post primary immunization, following booster on 21st day post immunization. Similarly, the immunized birds of group II the mean serum antibody titre of 7th dpi was continued to increase significantly at every weeks of observation till it reached peak on 21st (4576.27±42.9). The declining trend of the mean serum antibody titre was observed in the birds of group II from the day 28th of post immunization (4219.12±64.5) and continued till end of the study, i.e. the 60th dpi (3813.83±148.5). No significant difference could be observed between the two preparations, with and without booster in respect to the mean serum antibody titre till 21st dpi. Challenge trial could establish 100 per cent protection of vaccinated birds against homologous challenge, while development of clinical signs in the immunized birds was observed, following heterologous challenge. There was no significant difference between OMVs administered group and control group was observed in terms of blood SOD and GPx activity.EnglishThesis