RecombinantMycobacterium bovisBCG Expressing the Sm14 Antigen ofSchistosoma mansoniProtects Mice from Cercarial Challenge

Abstract

The Sm14 antigen ofSchistosoma mansoniwas cloned and expressed inMycobacterium bovisBCG as a fusion with theMycobacterium fortuitumβ-lactamase protein under the control of its promoter, pBlaF*; the protein was localized in the bacterial cell wall. The rBCG-Sm14 strain was shown to be relatively stable in cultured murine and bovine monocytes in terms of infectivity, bacterial persistence, and plasmid stability. The immunization of mice with rBCG-Sm14 showed no induction of anti-Sm14 antibodies; however, splenocytes of immunized mice released increased levels of gamma interferon upon stimulation with recombinant Sm14 (rSm14), indicating an induction of a Th1-predominant cellular response against Sm14. Mice immunized with one or two doses of rBCG-Sm14 and challenged with liveS. mansonicercaria showed a 48% reduction in worm burden, which was comparable to that obtained by immunization with three doses of rSm14 purified fromEscherichia coli. The data presented here further enhance the status of Sm14 as a promising candidate antigen for the control of schistosomiasis and indicate that a one-dose regimen of rBCG-Sm14 could be considered a convenient means to overcome many of the practical problems associated with the successful implementation of a multiple-dose vaccine schedule in developing countries.