Paratuberculosis: a mucosal immunology perspective.

Johne's disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP), is a chronic enteric infection of ruminants characterized by persistence in intestinal macrophages following invasion through Peyer's patches. Early studies established a predominantly cell-mediated immune response during early stages of infection, yet this fails to clear mucosal infection. Recent vaccine studies demonstrate partial, region-specific protection and induction of mucosal immune responses but also reveal marked differences in responses across intestinal regions. Correlates of protection are poorly defined and key knowledge gaps remain in defining the mechanisms underlying mucosal immunity to MAP in ruminants. In this mini review, we synthesize current knowledge of host immune responses to MAP and highlight research gaps from a mucosal immunology perspective that continue to impede vaccine development. Addressing these gaps is essential to advance vaccine research for Johne's disease.