Tumor Necrosis Factor alpha antagonists (anti-TNFα) have been extensively used for Crohn's disease (CD) treatment. Even though they may control CD symptoms initially, treatment response varies among patients, which seems to depend on single nucleotide polymorphisms (SNPs) in TNFα receptors superfamily 1A and 1B (TNFRSF1A/B). Most importantly, M. tuberculosis infection has been strongly associated with these medications, but no studies have elucidated the effects of anti-TNFα on CD associated with MAP (Mycobacterium avium subspecies paratuberculosis; a possible causative agent of CD, and closely related to M. tuberculosis). Here, we investigated the effects of recombinant inflammatory cytokines and anti-TNFα therapeutics on macrophages infected with MAP isolated from CD patient. We also tested the prevalence of MAP and the significance of nine SNPs in TNFα, TNFRSF1A and TNFRSF1B from the blood of 54 CD and 50 healthy subjects by IS900 nPCR. Both PEGylated and non-PEGylated forms of anti-TNFα increased MAP viability by nearly 1.5 Log CFU/mL, while rIL-6 and rIL-12 induced MAP viability at 5.42 ± 0.25 and 4.79 ± 0.14 Log CFU/mL, respectively. In contrast, rTNFα reduced MAP survival in infected macrophages by 2.63 Log CFU/mL. Expression of TNFα, IL-6, and IL-12 was upregulated by three folds following MAP or M. tuberculosis infection compared to other bacterial strains (P < 0.05). Four SNPs (TNFα:rs1800629, TNFRSF1A:rs767455, TNFRSF1B:rs1061624 and TNFRSF1B:rs3397) were overrepresented significantly (P < 0.05) among CD patients compared to healthy controls. The TNFRSF1A:rs767455 GG genotype was found in 15/54 CD patients (28%), while it was only found in 2/50 healthy controls (4%) [OR = 9.2, 95% CI: 1.98-42.83]. The TNFRSF1B:rs3397 TT genotype was found in 15/54 CD patients (28%) compared to (4/50) healthy controls (8%) [OR = 4.4, 95% CI: 1.36-14.14]. Furthermore, the SNPs TNFRSF1A:rs767455 and TNFRSF1B:rs3397 were associated with downregulating their corresponding genes significantly (P < 0.05). MAP infection was predominantly found among CD patients in comparison to healthy controls (57% vs 8%, respectively), which was also dependent on the SNPs TNFRSF1A:rs767455 and TNFRSF1B:rs3397. Our SNP haplotype analysis of TNFRSF1A:rs767455 and TNFRSF1B:rs3397 indicates that the G – T haplotype is significantly distributed among CD patients (46%) and MAP infection susceptibility is also associated with this specific haplotype (31%). The data indicate MAP positive CD patients receiving anti-TNFα could result in favorable conditions for MAP infection, which explains the poor response of many CD patients to this treatment, leading to adverse outcomes ultimately.
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Doctor of Philosophy (Ph.D.)
College of Medicine
Length of Campus-only Access
Doctoral Dissertation (Campus-only Access)
Qasem, Ahmad, "Role of TNFα Antagonists and Genetic Polymorphisms in Modulating Susceptibility to Mycobacterial Infection among Patients with Crohn's Disease" (2019). Electronic Theses and Dissertations, 2004-2019. 6836.