Immunogenicity and protective potential of a bacterially expressed recombinant dihydrolipoamide succinyltransferase (rE2o) of Brucella abortus in BALB/c mice.

Brucellosis is one of the world's major zoonoses. No vaccine is available for the prevention of brucellosis in human. Efforts are needed to develop an effective, safe, stable, vaccine with long lasting immunity against human brucellosis. Here, we cloned and expressed recombinant dihydrolipoamide succinyltransferase (rE2o) of Brucella abortus in Escherichia coli and purified up to homogeneity by metal affinity chromatography. The purified rE2o is immunoreactive with brucellosis positive cattle sera. The immunogenicity and the protective potential of recombinant dihydrolipoamide succinyltransferase (rE2o) were evaluated in BALB/c mice with two different adjuvants i.e., Freund's and aluminium hydroxide gel. Mice were tested for humoral immune response by ELISA. Cell mediated immune response was tested by lymphocyte proliferation assay and cytokine profiling. The recombinant E2o (rE2o) generated high IgG antibody and its isotypes IgG1, and induced significant production of INF-γ, IL-10 and IL-4 cytokines. The rE2o protein induced significant lymphoproliferation of splenocytes. Altogether, these results suggest that rE2o induces a mixed but a predominant Th2 type of immune response in BALB/c mice and provides partial protection against challenge with pathogenic Brucella abortus.