Fasciola gigantica fatty acid binding protein (FABP) as a prophylactic agent against Schistosoma mansoni infection in CD1 mice

Abstract

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 fatty acid binding protein (FABP) from Fasciola 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 FABP 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, evidenced by the significant reduction in mean worm burden (72.3%), liver and intestinal egg counts (81.3% and 80.8%, respectively), and hepatic granuloma counts (42%). Also, it elicited mixed IgG(1)/IgG(2b) immune responses with predominant IgG1 isotype, suggesting that native F. gigantica FABP is mediated by a mixed Th1/Th2 response. However, it failed to induce any significant differences in the oogram pattern or in the mean granuloma diameter. This indicated that native F. gigantica FABP could be a promising vaccine candidate against S. mansoni infection.

Keywords: FABP; Fasciola gigantica; Schistosoma mansoni; Th1/Th2 immunity; heterologous protection.

Fig. 1

Analysis of different F. gigantica antigen extracts by 12% SDS-PAGE.

Fig. 2

Hepatic granuloma diameter. (A) Hepatic sections of S. mansoni infected control animals at week 8 PI showed that granulomas were large, scattered of both cellular and fibrocellular types. Mild degree of hydropic degeneration was observed in many of the hepatocytes. (B) Hepatic sections of immunized infected group showed milder fibrosis, and chronic perivascular inflammation was still observed.