Intestinal immune response of weaned pigs experimentally vaccinated with F4ac+ non-enterotoxigenic strains of escherichia coli

Abstract

The potential effects of two adjuvants - the copolymer of polyoxyethylene-polyoxypropylene (POE-POP) and N-acetylglucosaminyl-(β, 1-4)-N-acetyl-muraminyl-L-alanyl-D-isoglutamine (GMDP) on mucosal humoral and cell-mediated immune responses were tested in weaned pigs immunized with the F4ac+ non-enterotoxigenio Escherichia coll (non-ETEC) strain 2407 and challenged with the F4+ ETEC strain 11-800/1/94. The presence of an anti-F4ac secretory IgA (sIgA) antibody in small intestinal washes was detected by the use of an indirect ELISA test, and the tissue-specific distribution patterns of CD3a+ and CD21+ T and B cells, respectively, within the gut mucosa were evaluated by an immunohistochemical in situ staining. The results showed that approximately 75% of 2407+POE-POP-treated pigs, and 50% to 60% of pigs that were immunized with either the 2407+GMDP or the 2407 strain alone respectively, were positive for anti-F4ac sIgA antibodies. The T cell antigen CD3a was expressed predominantly in lymphocytes in the ileal epithelium, the dome region of ileal Peyer's patches (IPP) and the extrafollicular areas of the mesenteric lymph node (MLN) in 2407+GMDP or 2407-treated pigs. The B cells expressing a CD21 surface molecule were present in the interfollicular areas of MLN and the germinal centers of IPP in 2407-treated pigs. A strong reaction to sIgA was determined in plasma cells in the lumen of the crypts and in the cells residing the lamina propria (LP) of the jejunum and ileum of pigs immunized with the 2407 strain. The obtained results imply that oral immunization of weaned pigs with the F4ac+ non-ETEC strain may induce the priming of intestinal immune cells, which can be additionally enhanced by the tested adjuvants.