CpG-ODN class C-mediated immunostimulation and its potential against Trypanosoma evansi in equines

Trypanosoma evansi is the causative agent of surra, which is the most common and widespread trypansomal disease. The infection is mainly restricted to animals, but it has also been documented in human. Trypanosomes possess the thick immunogenic surface coat known as variant surface glycoprotein (VSG). The parasite modifies the VSG constantly resulting in continuous antigenic variations and thus evades the host immune response. Due to antigenic variations, vaccination against trypanosomosis is not useful. Therefore, alternate strategies to augment the immune response are required. CpG-ODN class-C has combined immune effects of both A and B classes of CpG-ODN. In this study, we observed that CpG-ODN class-C stimulated horse peripheral blood mononuclear cells (PBMC) induce the expression of interferon-α (IFN-α), tumor necrosis factor-α (TNF-α), IL-12 and nitric oxide (NO) indicating enhanced innate immune response. We have for the first time demonstrated that co-culture of CpG-ODN with T. evansi antigen induces lymphocyte proliferative responses and result in a synergistic effect in eliciting the immune response.