Authors

M El-FahamK J Francklow²; J R Sayers⁵; H Price³; M J Doenhoff⁴;  ¹ Alexandria University, Egypt;  ² Bangor University, United Kingdom;  ³ Keele University, United Kingdom;  ⁴ University of Nottingham, United Kingdom;  ⁵ University of Sheffield, United Kingdom

Discussion

The Schistosoma mansoni cercarial elastase (SmCE) has previously been shown to be poorly immunogenic in mice. However, a minority of mice that were able to produce antibodies against SmCE after immunization with crude preparations containing the enzyme were partially protected against challenge infections of S. mansoni. In the present study, we show that in contrast to the poor immunogenicity of the enzymatically-active native form of SmCE, immunization of CBA/CA mice with purified native SmCE or a recombinant SmCE fused to recombinant S.japonicum glutathione S-transferase (rSmCE-SjGST) adsorbed onto aluminum hydroxide (alum) adjuvant (both are enzymatically-inactive), induced specific anti-SmCE IgG (mainly of the IgG1 subclass) in all mice within two weeks of the second immunization. Mice immunized with the rSmCE-jGST on alum showed 35% and ~50% reductions, respectively in mean worm burden and tissue eggs counts when compared to adjuvant alone-injected controls. These results suggest that SmCE may have potential as a vaccine candidate against schistosomiasis and that inactive forms of the antigen could be used to obtain the optimum immunogenic and protective effects.