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Recently, the World Health Organization recognized that efforts to interrupt schistosomiasis transmission through mass drug administration have been ineffective in some regions; one of their new recommended strategies for global schistosomiasis control emphasizes targeting the freshwater snails that transmit schistosome parasites. We sought to identify robust indicators that would enable precision targeting of these snails. At the site of the world’s largest recorded schistosomiasis epidemic—the Lower Senegal River Basin in Senegal—intensive sampling revealed positive relationships between intermediate host snails (abundance, density, and prevalence) and human urogenital schistosomiasis reinfection (prevalence and intensity in schoolchildren after drug administration). However, we also found that snail distributions were so patchy in space and time that obtaining useful data required effort that exceeds what is feasible in standard monitoring and control campaigns. Instead, we identified several environmental proxies that were more effective than snail variables for predicting human infection: the area covered by suitable snail habitat (i.e., floating, nonemergent vegetation), the percent cover by suitable snail habitat, and size of the water contact area. Unlike snail surveys, which require hundreds of person-hours per site to conduct, habitat coverage and site area can be quickly estimated with drone or satellite imagery. This, in turn, makes possible large-scale, high-resolution estimation of human urogenital schistosomiasis risk to support targeting of both mass drug administration and snail control efforts.

The present study investigated the suitability of various microparticles produced by spray-drying technique to entrap and preserve the physiochemical and biological properties of an antigen. These microparticles were constituted either by poly(lactide) polymers characterized by various molecular weight or poly(lactide-co-glycolide) polymers. The recombinant 28 kDa glutathione S-transferase of Schistosoma mansoni (rSm28GST) characterized by major epitopes involved in the active site of this enzyme was selected as model antigen, The microparticles were characterized by a mean size less than or equal to 5 mu m and an antigen loading of approximately 2% (w/w), The analysis by SDS-PAGE electrophoresis of the rSm28GST released from microparticles confirmed the conservation of its physicochemical characteristics. The conservation of the native structure of the entrapped antigen was confirmed by detecting its enzymatic activity after release from microparticles, A single intraperitoneal immunization of mice with rSm28GST entrapped in microparticles resulted in a specific antibody response, which remained high for at least 7 months, The analysis of the isotype profile indicated that immunized mice primarily produced anti-rSm28GST immunoglobulin (Ig) G1 with the coexistence of lower IgG2a and IgG2b levels. Finally, the recognition of the major epitopic regions and the neutralization of the enzymatic activity of the rSm28GST by the antisera confirmed the specificity of the response against the native structure of the antigen,These results confirmed the integrity of the entrapped antigen. Moreover, our results supported the hypothesis that the duration of antigen release is the limiting factor for the duration of antibody production. Indeed, the use of polymers characterized by different molecular weights allowed us to modify the duration of the immune response. Together, these results demonstrated that microencapsulation of an antigen by spray-drying preserved its crucial char

The purpose of this work was to assess the immunogenicity of a single nasal or oral administration of recombinant 28-kDa glutathione S-transferase of Schistosoma mansoni (rSm28GST) entrapped by poly(lactide-co-glycolide) (PLG)- or polycaprolactone (PCL)-biodegradable microparticles. Whatever the polymer and the route of administration used, the equivalent of 100 microg of entrapped rSm28GST induced a long-lasting and stable antigen-specific serum antibody response, with a peak at 9 to 10 weeks following immunization. Isotype profiles were comparable, with immunoglobulin G1 being the predominant isotype produced. The abilities of specific antisera to neutralize the rSm28GST enzymatic activity have been used as criteria of immune response quality. Pooled 10-week sera from mice receiving PLG microparticles by the nasal or oral route neutralized the rSm28GST enzymatic activity, whereas sera of mice receiving either PCL microparticles, free rSm28GST, or empty microparticles inefficiently neutralized this enzymatic activity. Finally, this study shows that a single administration of these microparticles could provide distinct and timely release pulses of microencapsulated antigen, which might greatly facilitate future vaccine development.

This work investigated the means for the efficient encapsulation of muramyl dipeptide (MDP) in poly(epsilon-caprolactone) (PCL) microparticles (MP) by a solvent evaporation method in order to optimize the effect of the adjuvant for oral immunization. Therefore, the influence of MDP concentration in the inner aqueous phase was evaluated on MP characteristics such as size, morphology, drug entrapment, entrapment efficiency and the eventual interactions of MDP with co-entrapped model antigen, bovine serum albumin (BSA). The process of manufacturing produced a high entrapment efficiency of MDP (63.58 +/- 0.40%) without altering its integrity, as shown by chromatogram peaks analysis of a and beta anomers. The crystallinity of the polymer was dramatically increased (+24.6%) either with or without MDP loading but the entrapment of BSA reduced this crystallinity suggesting BSA-PCL interaction. These MP were resistant to simulated gastric fluid and exhibited a continuous BSA release. Moreover, their average diameter (<10 microm) combined with their high hydrophobicity make of this delivery system an exciting alternative for enhanced oral immunization.