Single-dose mucosal immunization with biodegradable microparticles containing a Schistosoma mansoni antigen

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 pol ymer and the route of administration used, the equivalent of 100 mu g of en trapped rSm28GST induced a long-lasting and stable antigen specific serum a ntibody response, with a peak at 9 to 10 weeks following immunization. Isot ype profiles were comparable, with immunoglobulin G1 being the predominant isotype produced. The abilities of specific antisera to neutralize the rSm2 8GST enzymatic activity have been used as criteria of immune response quali ty. 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 micropar ticles inefficiently neutralized this enzymatic activity. Finally, this stu dy shows that a single administration of these microparticles could provide distinct and timely release pulses of microencapsulated antigen, which mig ht greatly facilitate future vaccine development.