Mycobacterium aviumsubsp.paratuberculosisFibronectin Attachment Protein Facilitates M-Cell Targeting and Invasion through a Fibronectin Bridge with Host Integrins

• DOI: 10.1128/iai.72.7.3724-3732.2004
• Publication Date: 2004-06-22T22:43:13Z
• Authors: T. E. Secott; T. L. Lin; C. C. Wu
• Keywords: Mycobacterium avium subsp. paratuberculosis; 0301 basic medicine; Integrins; Mice; 03 medical and health sciences; Mutation; Paratuberculosis; Animals; Intestinal Mucosa; Adhesins, Bacterial; Fibronectins

ABSTRACTEfficient attachment and ingestion ofMycobacterium aviumsubsp.paratuberculosisby cultured epithelial cells requires the expression of a fibronectin (FN) attachment protein homologue (FAP-P) which mediates FN binding byM. aviumsubsp.paratuberculosis. Invasion of Peyer's patches byM. aviumsubsp.paratuberculosisoccurs through M cells, which, unlike other intestinal epithelial cells, express integrins on their luminal faces. We sought to determine if the interaction between FAP-P ofM. aviumsubsp.paratuberculosisand soluble FN enabled targeting and invasion of M cells byM. aviumsubsp.paratuberculosisin vivo via these surface integrins. Wild-type and antisense FAP-P mutantM. aviumsubsp.paratuberculosisstrains were injected alone or coinjected with blocking peptides or antibodies into murine gut loops, and immunofluorescence microscopy was performed to assess targeting and invasion of M cells byM. aviumsubsp.paratuberculosis. NonopsonizedM. aviumsubsp.paratuberculosispreferentially invaded M cells in murine gut loops. M-cell invasion was enhanced 2.6-fold whenM. aviumsubsp.paratuberculosiswas pretreated with FN. Invasion of M cells by the antisense FAP-P mutant ofM. aviumsubsp.paratuberculosiswas reduced by 77 to 90% relative to that observed for the control strains. Peptides corresponding to the RGD and synergy site integrin recognition regions of FN blockedM. aviumsubsp.paratuberculosisinvasion of M cells by 75 and 45%, respectively, whereas the connecting segment 1 peptide was noninhibitory. Antibodies against the α5, αV, β1, and β3 integrin subunits inhibited M-cell invasion by 52 to 73%. The results indicate that targeting and invasion of M cells byM. aviumsubsp.paratuberculosisin vivo is mediated primarily by the formation of an FN bridge formed between FAP-P ofM. aviumsubsp.paratuberculosisand integrins on M cells.