Evaluation of an array of Mycobacterial proteins based ELISA assays for serodiagnosis of Crohn’s Disease


BACKGROUND: Mycobacterium avium subspecies paratuberculosis (MAP) has been suggested as a causative agent of Crohn's disease (CD). Despite a long-term debate to prove this possibility, the role of this bacterium in the pathogenesis of CD is still a subject of controversy. The objective of the study was to develop a serodiagnostic assay for the diagnosis of CD in humans. METHODS: In the present study, five different ELISA assays were accessed: 1) IDEXX, a commercially available kit for the diagnosis of Johne's disease in ruminants; 2) an in-house developed assay based on total MAP cytoplasmic proteins, and three other assays based on recombinant MAP recombinant antigens a) a 23 kDa antigen, pB11/B7, b) a 35 kDa antigen, P35 and c) a 36 kDa antigen, P36. The last three proteins were identified from an expression genomic library of MAP that was constructed in our laboratory. A total of 43 sera samples were analyzed in this study, which included 14 CD patients, 14 Ulcerative Colitis (UC) patients, and 13 non-inflammatory bowl disease (IBD) patients. lmmunoblot and silver stain analyses were performed to confirm protein identity and purity. ELISA was developed and used to analyze the level of anti-MAP lgG antibodies in sera from patients. RES UL TS: The rate of positive ELISA results is based on previously published interpretation criteria. ELISA results using the IDEXX kit showed 12/14 (85.7%) positive for CD as compared to 7/13 (53.8%) for non-lBD and 6/14 (42.9%) for uc.· 8/14 (57.1%) of the CD sera were positive with the ELISA results based on MAP cytoplasmic proteins compared with 6/13 (46.2%) of non-lBD and 10/14 (71.4%) of UC. Further analyzing the recombinant proteins, when two out of three assays were used 12/14 (85.7%) CD (P<0.05), 0/13 (0.0%) non-lBD, and 1/14 (7.7 %) UC were positive. Moreover, when all three recombinant proteins are utilized for analysis, the specificity of the test greatly increased, giving 13/14 (92.9%) positive for CD, 3/14 (21.4%) for UC and 2/14 (14.3%) for non-lBD. CONCLUSION: MAP recombinant proteins, pB11/B7, p35, and p36 showed a strong reactivity with diagnosed CD patients while excluding healthy individuals and other IBD patients. In addition, they served as a great tool to distinguish between CD and UC patients. A larger sample size needs to be tested, none the less this data strengthens the role of MAP in CD etiology and suggests a great potential for using the recombinant-based assays for diagnosis and treatment monitoring of patients with inflammatory bowel disease.


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Thesis Completion





Naser, Saleh A.


Bachelor of Science (B.S.)


Burnett College of Biomedical Sciences

Degree Program

Molecular Biology and Microbiology


Biomedical Sciences -- Dissertations, Academic; Dissertations, Academic -- Biomedical Sciences







Access Status

Open Access

Length of Campus-only Access


Document Type

Honors in the Major Thesis

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