engleski

Expression of differentiation molecules on porcine gut leukocytes primed with F4ac^+ nonenterotoxigenic Escherichia coli strain

Colibacillosis is a major cause of illness and mortality in recently weaned pigs. Usually it is a consequence of enterotoxigenic E. coli (ETEC) strains producing enterotoxins which disrupt the intestinal mucosal barrier, causing diarrheal disease. The intestine is capable of rapid immune responses, following recognition of enteric pathogens such as ETEC by lymphocytes in the gut-associated lymphoid tissues (GALT). Effective analyses of porcine gut immune cell subsets requires monoclonal antibodies (mAbs) reacting with their cell surface cluster of differentiation (CD) or swine workshop cluster (SWC) molecules. In order to evaluate the immunogenicity of F4ac^+ non-ETEC vaccine candidate strain in 4-week-old pigs we used two approaches: (1) to determine the immunophenotypic expression of CD/SWC molecules by flow cytometry and to quantify/characterize isolated cell populations, and (2) to examine the organization of the GALT compartments by immunohistology using anti-CD/SWC mAbs. Orogastric immunization of pigs with 10^10 CFU/ml of Abbotstown A strain induced substantial changes in the proportion of lymphoid and myeloid cells from the GALT of immunized pigs as compared to those in unimmunized pigs. The presence of antigen-specific T and B cells and antigen presenting cells (APCs) demonstrates that the GALT compartments of weaned pigs are functionally organized for expression of immune responses to the immunogens, such as F4 fimbrial adhesins of non-ETEC tested as a vaccine candidate strain. However, such responses frequently are associated with either hypersensitivity reactions/tissue damage or loss of function/tolerance for harmless molecules derived from diet/commensal intestinal microbiota. There is thus an additional requirement for our model of mucosal immunization to maintain the immune response following recognition of bacterial immunogens by APCs and activation of the effector cells within the GALT.

collibacilosis; pig; gut-associated lymphoid tissue; E. coli; orogastric immunization

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