Hsp70 vaccination-induced antibodies recognize B cell epitopes in the cell wall of Mycobacterium avium subspecies paratuberculosis

Mycobacterium avium subspecies paratuberculosis (MAP) causes a chronic intestinal infection of ruminants and has been associated with the etiology of human Crohn's disease. A MAP Hsp70/DDA subunit vaccine previously showed a significant reduction in fecal shedding of MAP in cattle, concomitant with pronounced antibody production against MAP Hsp70, rather than T cell reactivity. Our hypothesis is that if Hsp70-specific antibodies are able to confer protection, the first requisite would be that the Hsp70 molecule is accessible for antibodies in intact MAP bacteria. In the current study monoclonal antibodies identified MAP Hsp70 B cell epitopes. Two linear epitopes were also recognized by antibodies of vaccinated calves and goats. These epitopes showed to be accessible by antibodies in the bacterial cell wall and in intestinal lesional tissue during natural infection. These results indicate that vaccination-induced antibodies can bind intact bacteria and have the potential to contribute to the protective effect of Hsp70/DDA subunit vaccination against bovine paratuberculosis.