Abstract
BackgroundTrypanosomosis 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.MethodsThe 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.ResultImmunization 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.ConclusionsA 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.
Highlights
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
Serum cytokine and antibody responses following immunization To determine cytokine responses following vaccination and subsequent specific humoral immune response mounted against rTe-β-tubulin, sera from mice inoculated with rTe-β-tubulin (50 μg) in Freund’s complete adjuvant (FCA) or FCA alone were compared
At 24 h post inoculation, mice inoculated with rTe-β-tubulin in FCA showed significantly lower Interleukin 4 (IL-4) and significantly higher Tumor necrosis factor alpha (TNF-α) levels in the serum compared to pre-immunization levels (Fig. 2a)
Summary
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. 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. Trypanosoma evansi, a unicellular hemoflagellate, is the causative agent of ‘surra’, a debilitating disease of a wide range of livestock species in the tropics. This parasite is transmitted mechanically among its wide range of susceptible hosts by several species of hematophagous flies in Asia, Africa, Latin America and parts of Europe [1,2,3,4]. Immunization strategies in surra have focused on various alternate, invariant, and often immunologically subdominant epitopes [11,12,13,14]
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