Elevated antibody responses in patients with Crohn's disease against a 14-kDa secreted protein purified from Mycobacterium avium subsp. paratuberculosis

Patients with Crohn's disease (CD) (n = 10) and ulcerative colitis (UC) (n = 10) were tested for immune responses against various antigens from Mycoba cterium avium subsp. paratuberculosis; alkyl hydroperoxide reductase C (Ahp C) and alkyl hydroperoxide reductase D (AhpD), which are constitutively exp ressed in this species as opposed to other mycobacteria, a 14-kDa secreted antigen and PPD-J. The CD patients had significantly elevated antibody leve ls against the 14 kDa protein (P < 0.05) that were negatively correlated wi th the duration of the disease (r(s) = - 0.85). They also seemed to have in creased antibody levels against AhpC and AhpD, but the differences between the two groups were not significant. However, taken together, the antibody responses to three individual mycobacterial antigens in CD patients strengt hen the possibility that the observed responses are caused by mycobacterial infection. No significant differences in the interferon (IFN)-<gamma> prod uction, the interleukin (IL)-10 production and the ability to proliferate u pon stimulation with these antigens were observed. These results show that measuring antibody responses against purified specific antigens is a suitab le and simple approach when assessing the connection between CD and mycobac teria in patients with clinical CD. Another important aspect in such studie s is to have well defined patient groups tested at the onset of clinical sy mptoms.