Protective antibody and cytokine responses in mice following immunization with recombinant beta-tubulin and subsequent Trypanosoma evansi challenge

Abstract

Background: Trypanosomosis or Surra, caused by the flagellated hemoprotozoan parasite Trypanosoma evansi, is a disease of economic importance through its wide prevalence in domestic livestock in tropical countries. In the absence of a protective vaccine, management of the disease relies on a few available chemotherapeutic agents. Although humoral immunity is the mainstay of resistance to T. evansi, the ability of the parasite to vary its immunodominant surface proteins to subvert the immune system has forced vaccine efforts to target a variety of invariant epitopes. Beta tubulin, an integral component of the trypanosome cytoskeleton, was therefore targeted using the recombinant form of the protein for immunization. Methods: The 1329 bp coding sequence of beta tubulin gene was PCR amplified and cloned in pQE-TriSystem expression vector. Recombinant beta tubulin was heterologously expressed in Escherichia coli as a 46 KDa fusion protein and used for immunization of mice. The Ig response was studied by ELISA, whereas the cytokine response was measured using a cytometric bead-based assay quantified by flow cytometry. Result: Immunization with recombinant beta (β)-tubulin protein induced a beta-tubulin specific humoral immune response of predominantly IgG2a isotype. Lethal challenge with T. evansi blood-form trypomastigotes post-immunization elicited a robust anamnestic response. An abundance of IFN-γ further confirmed the Th-1 bias of the protective response. We also observed extended survival and better control of the challenge infection in the immunized mice. Conclusions: A robust anamnestic response following challenge including a Th-1 serum cytokine profile coupled with increased survival is indicative of protective immunity in the immunized mice. These observations suggest that β-tubulin of T. evansi is a viable antigenic target for development of a vaccine against this important livestock pathogen.