The role of the fibronectin -attachment protein of Mycobacterium avium subsp. paratuberculosis in the pathogenesis of Johne's disease
Abstract
Fibronectin (FN)-attachment proteins (FAPs) are a family of mycobacterial proteins that have been shown to facilitate FN-mediated attachment and internalization of mycobacteria in vitro. The purpose of the present study was to investigate the role that FAP plays in the attachment and invasion of M cells in the dome epithelium covering Peyer's patches by Mycobacterium avium subsp. paratuberculosis (Mpt). Fibronectin binding by Mpt was activated by acid treatment, demonstrating the physiologic relevance of FN binding as a potential virulence factor of Mpt. Mycobacterium avium subsp. paratuberculosis expresses a FAP, designated FAP-P, that is necessary for FN binding by this organism. However, this protein is not present on the surface of the organism, suggesting that one or more proteins cooperate with FAP-P to enable FN binding by Mpt in addition to FAP-P. Fibronectin enhanced attachment and ingestion of Mpt by Caco-2 and T-24 cells. Blocking with the FN binding peptide from M. avium subsp. avium FAP did not impede Mpt attachment to these cells, but virtually eliminated bacterial ingestion. Attachment and invasion of epithelial cells in vitro were significantly reduced in Mpt strains carrying antisense FAP-P mutations, indicating that these phenomena were FN-dependent processes that were mediated by FAP-P. Mycobacterium avium subsp. paratuberculosis selectively invaded M cells in vivo, and this process was enhanced in the presence of FN. Preferential invasion of M cells in vivo was eliminated in Mpt carrying antisense FAP-P mutations. Co-injection of the RGD cell-binding or synergy site peptides from FN or α5, αV, β1 or β3 integrin subunit blocking antibodies with Mpt into murine gut loops significantly impaired the preferential invasion of M cells by Mpt. This demonstrated that FN-opsonized Mpt specifically bound to integrins displayed on the lumenal surface of M cells. The results indicate that FAP-P dictates M cell targeting and invasion by Mpt by using FN to form a bridge with M cell surface integrins.
Degree
Ph.D.
Advisors
Wu, Purdue University.
Subject Area
Microbiology|Veterinary services|Pathology|Cellular biology
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