Role of Schistosoma mansoni Tegumental Cathepsin-B Antigen in Modulation of Murine Shistosomiasis

6 Abstract: Cysteine proteases are important virulence factors for parasites. Cathepsin B (SmCB) proteases are abundant in different stages of Schistosoma and they have been identified to induce a level of host-protective immune responses with amelioration of morbidity. In this study, the parasitological parameters, level of immunoglobulins, cytokines profile and hepatic granuloma were assessed to study the effect of immunization of mice with cathepsin B antigen with or without treatment using anti-helminthic drug praziquantel (PZQ). Multiple small doses of cathepsin B were intraperitoneally injected into naive mice; the first dose of a 100µg of purified (SmCB) was followed by two booster doses of 50µg each, at weekly intervals. The experimental design included six groups of 20 mice each;. Group 1 (normal control), Group 2 (infected control), Group 3, 4&5 were immunized intra-peritoneally with 100µg/ml of (SmCB) antigen emulsified with complete Freunds' adjuvant. Groups 4 and 5 were additionally infected subcutaneously with 100 S. mansoni cecariae, one week after last immunization and only group 5 was further treated by PZQ at the 5th week post-infection (p.i.). Group 6, mice were treated only with PZQ at the week 5th post-infection. Ten mice of each group were sacrificed at the end of week 8 and the other 10 were sacrificed at 12 weeks p.i. Parasitological, pathological and immunological parameters were evaluated. The histopathological and parasitological examinations revealed the highest remarkable increase in the percentage of degenerated ova (12%) within the diminished hepatic granulomas and the most significant decline percentage of the worm burden (46%), tissue egg loads (42.8% and 50% for hepatic and intestinal ova, respectively) were experienced by the infected pre-immunized and post-treated mice. The data collected from this research study might be useful in developing potential vaccine against S. mansoni.