CONSTRUCTION OF Brucella melitensis GHOST AS A VACCINE CANDIDATE AGAINST BRUCELLOSIS
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Date
2018-07
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KARNATAKA VETERINARY, ANIMAL AND FISHERIES SCIENCES UNIVERSITY, BIDA
Abstract
he present study reports the usefulness B. melitensis ghost as a vaccine candidate
against sheep and goat brucellosis. An overall seroprevalence of 36.36 per cent (200) by
RBPT, 47.27 per cent (260) by c-ELISA and 36.36 per cent (200) by both the tests with
highest seroprevalence of 56 per cent in Bengaluru rural for sheep and of 43 per cent in Kolar
for goats was observed. On an isolation from aborted foetuses five Brucella spp. were
recovered which were confirmed to be B. melitensis biotype 1 by biochemical tests, dye
sensitivity tests, agglutination with monospecific serum and by genus specific, species
specific and Bruce ladder PCR. The B. melitensis Rev 1 and B. melitensis field isolate ghosts
were constructed at a cell concentration of 3.0 x 10
9 CFU/mL of culture with 80 μg/mL GI24
for complete ghost formation was confirmed by absence of growth on BSA, non amplification of specific bands in AMOS multiple PCR and morphological changes observed
in scanning and transmission electron microscopy. All three vaccines, were evaluated in mice
by IP and oral routes, for humoral immune response by quantifying IgG levels in post
vaccinal sera and for cell mediated immune response by lymphocyte proliferation assay and
cytokine profiles of IL-10, IL-4, TNF-α and IFN-γ. There was a significant difference in IgG
levels between control and vaccinated groups. Further, within the vaccinated groups there
was a significant (P<0.05) difference between Rev 1 vaccinated group from Rev 1 ghost and
field ghost vaccinated groups in both IP and oral routes. The serum IgG levels were
significantly higher in Rev 1 IP route vaccinated group than other groups. There was an
interplay of both Th2 (IL-4 and IL-10) and Th1 cytokines (TNF–α and IFN-γ) in eliciting
effective immune response, wherein initial response was dominated by Th2 through IL-4 and
IL-10 which antagonize the TNF–α and IFN-γ cytokines whose role is very essential to
initiate cell mediated immune responses. In later stages decreased levels of IL-4 and IL-10
resulted in surge of TNF–α and IFN-γ cytokines resulting in effective Th1 mediated cellular
immune response which is required for effective clearance of Brucella organisms. The ghosts
made from B. melitensis Rev 1 and field isolate performed equally well as B. melitensis Rev
1 by eliciting an effective immune response and protecting mice against B. melitensis 16M
challenge.