Specific seroreactivity of Crohn's disease patients against p35 and p36 antigens of M. avium subsp. paratuberculosis.

Crohn's disease (CD) is a chronic inflammatory bowel disease that is similar to Johne's disease in ruminants. Recent data have strengthened the association of M. avium subsp. paratuberculosis (M. paratuberculosis) with CD. To provide more evidence of an etiological association, antibody reactivities from CD patients were tested by immunoblotting against recombinant antigens that were identified previously from our M. paratuberculosis genomic library. Two clones (designated pMptb#40 (3.2-kb insert) and #48 (1.4-kb insert) expressing a 35K (p35)- and 36K(p36)-antigens showed specific reactivities with serum samples from CD patients. Serum samples from 75% of 53 CD patients, 14% of 35 normal individuals and 10% of 10 ulcerative colitis patients reacted to p35 antigen. Reactivities were also observed with serum samples from 89% of 89 CD patients, 14% of 50 normal controls and 15% of 29 ulcerative colitis patients reacted with p36 antigen. When the reactivity results from p35 and p36 were combined, the background from the controls was eliminated, i.e. only the CD patients reacted to both p35 and p36. The positive predictive value was 98% with specificity of 98% and the negative predictive value was 76% with sensitivity of 74% (39 positive out of 53). A statistical significance (p<0.0001) was observed when the results from CD serum samples reacting with either or both antigens were compared to the controls. The reactivity of anti-M. paratuberculosis (specifically against p35 and p36 antigens) antibodies in a significant proportion of CD patients would suggest a causal role for the organism in CD.