engleski

Detection of wCD1, SWC1a, SWC2 and CD45 molecules by immunofluorescence or immunoperoxidase techniques in porcine gut-associated lymphoid tissues following experimentally induced colibacillosis

The pathogenesis of enterotoxigenic Escherichia coli (ETEC) infections relies on the expression of fimbrial antigens (F4 is the most commonly recognized) and the production of an exotoxin (usually STb). Protection from the disease in neonatal pigs is related to the development of lactogenic immunity and the passive transfer of antibodies. Protection of weaned pigs from ETEC will require the induction of mucosal immunity. The vaccine potential of non-enterotoxigenic (non-ETEC) strains containing either wild-type (1466) or recombinant plasmid (2407) encoding F4ac antigen were investigated by determining their role in (1) causing mucosal damage of the gut, (2) inducing an immune reaction of the gut-associated lymphoid tissues (GALT), i.e., in the small intestinal lamina propria (LP), ileal Peyer"s patches (PP) and mesenteric lymph node (MLN) (3) eliciting changes in T cell population in LP, PP and MLN of experimentally infected weaned pigs. Five principal 4-week-old pigs per group were intragastrically inoculated with either 1x10^10 cells in 60ml of Trypticase soy broth (TSB) of F4ac^+ ETEC (M1823) or non-ETEC (1466 or 2407). Control pigs received either F4- non-ETEC strain 1467 or TSB only. Lymphocytes were isolated from jejunal LP, ileal PP and MLN. Anti-swine CD-specific mAb against wCD1 or SWC2 and SWC1a or CD45 cells were used in a single-color FCM and immunohistology, respectively, to determine phenotypes/distribution of these lymphocyte subsets in lymphatic tissues tested. Unlike F4ac^+ ETEC strain M1823, both non-ETEC strains (1466 and 2407) induced only a mild swelling of the small intestinal mucosa and a moderate leukocyte infiltration in jejunal/ileal LP. An increase of wCD1^+ and SWC2^+ cells was detected by single-color fluorocytometry (FCM) among B and T lymphocytes from LP and MLN of 2407-infected pigs. Large numbers of CD45^+ cells were observed in LP/MLN of pigs infected with either 2407 or M1823 strain of E. coli. The use of non-ETEC strain 2407 was associated with a marked leukocytosis and proliferation of wCD1^+ and SWC2^+ cells in both tested compartments of porcine GALT. This strain neither caused lesions of jejunal/ileal villous epithelium nor produced diarrheal disease in orally infected pigs.

T and B lymphocytes ; Gut-associated lymphoid tissues ; Flow cytometry ; Immunohistology ; Swine colibacillosis

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