The extracellular region of Trypanosoma congolense Membrane Bound Acid Phosphatase induces partial protection in immunized BALB/c mice

African trypanosomiasis is a parasitic disease caused by African trypanosomes and there is no vaccine because the trypanosomes possess an intricate machinery for antigenic variation. Owing to the nonsusceptibility of trypanosomes' Membrane-Bound Acid Phosphatase (MBAP; EC 3.1.3.2) to antigenic variation and its central role in molecular trafficking, we hypothesized that MBAP is a promising target for vaccine development. Herein, a DNA vaccine was constructed using recombinant DNA technology to insert the gene of the extracellular portion (EP) of Trypanosoma congolense MBAP without its signal peptide (SP), into a Strep-tag/transin modified mammalian expression vector pVAX1. The construct (EP-SP/pVAX1) was transfected into HepG2 cells. Expression of the antigen (EP-SP) and the subcellular localization were confirmed by Immunofluorescence Assay. Thereafter, two independent vaccination trials with 100 μg EP-SP/pVAX1 were carried out in BALB/c mice. ELISA was used to check immunoglobulin G (IgG) and cytokines (IL-10 and IFN-ɣ) levels. The infection group were experimental infected with 10⁴ T. congolense cells, and the potency of the vaccine was assessed by monitoring parasitemia and survival. There was a significant increase in circulating IgG (P = 0.048), IL-10 (P = 0.031) but no effect on IFN- ɣ (P = 1.001) in the animals. Low parasitaemia characterized by multiple waves with the intermittent clearing of parasites to no detectable levels, and extension of the lifespan by up to 45.45 % was observed with a complete survival of 20 % of vaccinated and infected mice. Together, the results showed that the vaccine construct was partially protective and has tremendous immunogenic potential, suggesting the needs for further studies.