Murine intestinal humoral responses in chronic Schistosoma mansoni infections

Whole-genome microarray analysis and functional characterization reveal distinct gene expression profiles and patterns in two mouse models of ileal inflammation

Background

Although a number of intestinal inflammatory conditions pertain to the ileum, whole-genome gene expression analyses in animal models of ileal inflammation are lacking to date. Therefore, we aimed to identify and characterize alterations in gene expression in the acutely inflamed ileum of two murine models of intestinal inflammation, namely intestinal schistosomiasis and TNBS-induced ileitis, compared to healthy controls. To this end, we used whole-genome microarrays, followed by bioinformatics analyses to detect over-represented Kyoto Encyclopedia of Genes and Genomes pathways and Gene Ontology categories.

Results

Following screening of almost all known mouse genes and transcripts represented on the array, intestinal schistosomiasis and TNBS-induced ileitis yielded 207 and 1417 differentially expressed genes, respectively, with only 30 overlapping concordantly changed genes. Functional category groups consisting of complement and coagulation cascades, extracellular matrix (ECM)-receptor interaction, Fc epsilon receptor I signaling pathways and protein activation cascade, cell adhesion categories were over-represented in the differential gene list of intestinal schistosomiasis. Antigen processing and presentation, cell adhesion molecules, ABC transporters, Toll-like receptor signaling pathways and response to chemical stimulus categories were over-represented in the differential gene list of TNBS-induced ileitis. Although cytokine-cytokine receptor interaction, intestinal immune network for IgA production, focal adhesion pathways and immune, inflammatory and defense response categories were over-represented in the differential gene lists of both inflammation models, the vast majority of the associated genes and changes were unique to each model.

Conclusions

This study characterized two models of ileal inflammation at a whole-genome level and outlined distinct gene expression profiles and patterns in the two models. The results indicate that intestinal schistosomiasis involves Th2 responses, complement activation, protein activation and enhanced ECM turnover, while TNBS-induced ileitis involves Th17 responses, defective antigen processing and presentation and altered Toll-like receptor-mediated responses. Signs of an impaired epithelial barrier are apparent in both inflammation models. Furthermore, the comprehensive differential gene list and functional groups provided by this study constitute an interesting starting point to explore new targets and extended functional networks dealing with small bowel inflammation.

Immunoglobulin A response in murine schistosomiasis: stimulatory role of egg antigens

The immunoglobulin G (IgG) and IgA antibody responses to different Schistosoma mansoni antigens have been determined in chronically infected mice as well as in unisexually infected animals. With a panel of enzyme-linked immunosorbent assays (ELISAs), soluble antigens from furcocercariae, adult worms, and eggs were probed with sera collected at 3-week intervals. Bisexually infected animals developed significant IgG and IgA antibody responses to the antigens tested, which increased after egg deposition. In unisexual infections no significant differences were recorded in the IgG antibody profile for furocercaria and adult worm antigens, whereas the IgA antibody response was impaired. Both the IgA and IgG antibody responses toward egg antigens were reduced compared with those in a bisexual infection. Furthermore, a specific mucosal IgA antibody response was observed only in the bisexually infected animals. Histological analysis performed on bisexually infected mice led to the observation of eggs and granulomatous lesions within the Peyer's patch follicles, which are essential sites for the induction of mucosal immunity in the intestine. These data suggest a relationship between egg deposition and the induction of the IgA antibody response toward schistosomes.

Somatic antigens of adult Dicrocoelium dendriticum recognised by bile antibodies of naturally infected cattle

Bile samples, from slaughtered cattle harbouring between 120 and 280 adult lancet flukes, were used to investigate the range of somatic proteins inducing local antibody responses in naturally infected animals. Lancet fluke infections induced local (bile) antibody responses against Tris-buffered saline (TBS) soluble, sodium dodecyl sulphate (SDS) soluble and 2-mercaptoethanol (2-Me) soluble somatic proteins of adult Dicrocoelium dendriticum. IgA antibody isotypes predominated in the response against buffer-soluble somatic antigens, whereas SDS-soluble and 2-Me-soluble proteins induced similar level of both IgA and IgG1 antibodies. Analysis of the antigens recognised by particular isotype-specific bile antibodies suggests that different antigens preferentially induce isotype restricted antibody responses. The bile antibody response was highly species specific, only one antigen from somatic protein extracts of Fasciola hepatica being precipitated by bile samples showing the highest reactivity against D. dendriticum.