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Kerala Veterinary and Animal Sciences University, Wayanad

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20191
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Subject: Veterinary Microbiology × Author: RINSHA BALAN × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    ASSESSMENT OF CELL MEDIATED AND HUMORAL IMMUNE RESPONSE TO SUBUNIT VACCINE AGAINST RIEMERELLOSIS
    (COLLEGE OF VETERINARY AND ANIMAL SCIENCES MANNUTHY, THRISSUR, 2019-12-30) RINSHA BALAN; Priya P. M.
    Riemerellosis is a bacterial disease among ducks, caused by Riemerella anatipestifer, which has been well documented as a cause of considerable economic loss to the duck production in Kerala. At least 21 serotypes of the organism have been identified globally. Since vaccination is the mainstay for the control of the disease, a research work was undertaken to prepare subunit vaccine employing recombinant OmpA of R. anatipestifer and assessment of cell mediated and humoral immune responses of the vaccine and also to evaluate the comparative efficacy with that of the developed inactivated vaccine. Broth culture of R. anatipestifer at a concentration of 2.5 OD values at 525 nm with a dose of 1 mL per bird subcutaneously was selected as LD50. L per bird subcutaneously was selected as LD50. A total of 52, day-old ducklings were divided into three treatment groups with ten birds each. They were injected with 0.5 mL of different types of vaccine subcutaneously. Group I (T1) served as control with 22 birds including six birds each for challenge control of inactivated and subunit vaccine. Group II (T2) was injected with an inactivated vaccine (7x109 cfu/mL), which was prepared as per the protocol standardised in the Department of Veterinary Microbiology and group III (T3) and group IV (T4) were administrated with different antigen concentration of subunit vaccine (equal quantity of the rompA protein (250µg and 500µg) and montanide, respectively). A booster dose was given at third week post-primary vaccination to T2, T3 and T4. It was observed that, by using both crude Omp and rOmpA based ELISA, inactivated vaccine birds (T2) produced higher antibody titre during early age while in the subunit vaccine group, the titre was higher during later stage. An early antibody response is required to lower the mortality rate in riemerellosis as the organism targets young ducklings. Thus, it could be inferred from this study that inactivated vaccine was more effective than subunit vaccine A significant CMI response was also shown by inactivated vaccine groups on 14th and 28th day post-vaccination by lymphocyte proliferation assay (LPA). Challenge studies to assess the protective response revealed 100 per cent protection for inactivated vaccine group (T2), 80 per cent protection for T4 group and 70 percent protection for T3 group. All the vaccinated birds were having significantly less gross lesion when compared to the challenge control groups. On analysing the cytokine mRNA expression levels using real-time PCR, the inactivated vaccine group showed significantly higher (p< 0.05) mRNA levels of IL-6, IL-12B and IFN-γ gene on day 28 than the two subunit vaccine groups. It was found that the inactivated vaccine was superior in terms of results obtained from the challenge study, antibody titre, CMI response and gene expression analysis than the subunit one. Hence, it is desirable to advocate the use of inactivated vaccine in field condition owing to its easiness to prepare and low cost.