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. para) with Crohn's disease. To provide more evidence of an etiological association, antibody reactivities of CD patients were tested by immunoblotting against recombinant antigens that were identified previously from our M. para 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 from CD patients. The summary of results is as follows:
| Antigens | Positive samples/Total tested (% +ve) | PPV | NPV |
|---|
| | CD | Controls | Ulcerative colitis | % | % |
| p36 alone | 79/89 (89) | 7/50 (14) | 10/29 (34) | 93 | 89 |
| p35 alone | 40/53 (75) | 5/35 (14) | 1/10 (10) | 93 | 78 |
| p35 & p36 | 39/53 (74) | 0/35 (0.0) | 1/10 (10) | 98 | 76 |
| PPV= Positive predictive value (specificity); NPV = Negative predictive value (sensitivity) |
A statistical significance (p<0.001) is observed when the results from CD serum samples reacting with either or both antigens are compared to the controls. The reactivity of anti-M. para (specifically against p35 and p36 antigens) antibodies in a significant proportion of CD patients would suggest a causal role for the organism in both diseases.
