Resistance of CD1 Mice to Schistosoma mansoni Infection Using Fasciola gigantica Fatty Acid Binding Protein

Abstract

Schistosomes are blood-dwelling flukes that infect 200 million people worldwide and are responsible for hundreds of thousands of deaths annually. Although schistosomicidal drugs and other control measures exist, the advent of an efficacious vaccine remains the most potentially powerful means for controlling this disease. In this study, native FABP from F. gigantica was purified from the adult worm's crude extract by saturation with ammonium sulphate followed by separation on DEAE- sephadex A-50 anion exchange chromatography and gel filtration using sephacryl HR-100, respectively. CD1 mice were immunized with the purified, native F. gigantica fatty acid binding protein in Freund's adjuvant and challenged subcutaneously with 120 Schistosoma mansoni cercariae. Immunization of CD1 mice with F. gigantica FABP has induced heterologous protection against S. mansoni. This protection evident as significant reduction in mean worm burden (72.3%), liver and intestinal egg count (81.3%% and 80.8%, respectively) and hepatic granuloma counts (42%). Also, it elicited mixed IgG1/IgG2b immune responses with IgG1 isotype predominating. This suggests that native F. gigantica FABP is mediated by a mixed Th1ffh2 response. In contrast, it failed to induce any significant differences in the mean total number of S. mansoni egg stages or in the mean granuloma diameter. This indicated that native F. gigantica FABP considered as a promising vaccine candidate against S. mansoni.