ORAL IMMUNIZATION OF RAINBOW-TROUT WITH ANTIGEN MICROENCAPSULATED IN POLY(DL-LACTIDE-CO-GLYCOLIDE) MICROPARTICLES

The model protein antigen, human gamma globulin (HGG) was microencapsu lated in poly(DL-lactide-co-glycolide) microparticles and administered ed orally to rainbow trout, Oncorhynchus mykiss (Walbaum, 1792). Usin g a Western blotting technique it was demonstrated that the dynamics o f passage through the gut were different for the microencapsulated and soluble antigen. The association of HGG with microparticles increased the retention time of the antigen in the stomach and delayed its entr y into the intestinal region. After the delivery of microencapsulated HGG, antigen was detected in gut contents in fragmented form which sug gested that some of the antigen was present at the particle surface an d therefore susceptible to proteolysis. However; a greater amount of i ntact antigen was detected in the posterior intestine and in the blood stream of fish, which were administered with microparticle-associated than soluble antigen, indicating that the antigen was partially protec ted. Immunization with microencapsulated HGG resulted in the detection of specific antibody in the serum but levels were not significantly g reater than after the delivery of soluble antigen. However specific an tibody was detected in the intestinal mucus of fish which were adminis ter-ed with the microencapsulated antigen after boosting with soluble HGG but not in fish which were primed with the soluble antigen. (C) 19 97 Elsevier Science Ltd.