CHARACTERIZATION OF OUTER MEMBRANE VESICLES (OMVs) OF Pasteurella multocida OF AVIAN ORIGIN
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Date
2020-01
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College of Veterinary Science, Assam Agricultural University, Khanapara, Guwahati
Abstract
The 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.