Abstract
Mycobacterium avium subsp. paratuberculosis, the agent of Johne's disease, infects ruminant hosts by translocation through the intestinal mucosa. A number of studies have suggested that M. avium subsp. paratuberculosis interacts with M cells in the Peyer's patches of the small intestine. The invasion of the intestinal mucosa by M. avium subsp. paratuberculosis and Mycobacterium avium subsp. hominissuis, a pathogen known to interact with intestinal cells, was compared. M. avium subsp. paratuberculosis was capable of invading the mucosa, but it was significantly less efficient at dissemination than M. avium subsp. hominissuis. B-cell knockout (KO) mice, which lack Peyer's patches, were used to demonstrate that M. avium subsp. paratuberculosis enters the intestinal mucosa through enterocytes in the absence of M cells. In addition, the results indicated that M. avium subsp. paratuberculosis had equal abilities to cross the mucosa in both Peyer's patch and non-Peyer's patch segments of normal mice. M. avium subsp. paratuberculosis was also shown to interact with epithelial cells by an alpha(5)beta(1) integrin-independent pathway. Upon translocation, dendritic cells ingest M. avium subsp. paratuberculosis, but this process does not lead to efficient dissemination of the infection. In summary, M. avium subsp. paratuberculosis interacts with the intestinal mucosa by crossing both Peyer's patches and non-Peyer's patch areas but does not translocate or disseminate efficiently.