Genetic susceptibility to increased bacterial translocation influences the response to biological therapy in patients with Crohn's disease.

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http://gut.bmj.com/content/63/2/272.long

2014 Feb, Gut

Gutiérrez A, Scharl M, Sempere L, Holler E, Zapater P, Almenta I, González-Navajas JM, Such J, Wiest R, Rogler G, Francés R.

Genetic susceptibility to increased bacterial translocation influences the response to biological therapy in patients with Crohn's disease.

OBJECTIVE:

The aetiology of Crohn's disease (CD) has been related to nucleotide-binding oligomerisation domain containing 2 (NOD2) and ATG16L1 gene variants. The observation of bacterial DNA translocation in patients with CD led us to hypothesise that this process may be facilitated in patients with NOD2/ATG16L1-variant genotypes, affecting the efficacy of anti-tumour necrosis factor (TNF) therapies.

DESIGN:

179 patients with Crohn's disease were included. CD-related NOD2 and ATG16L1 variants were genotyped. Phagocytic and bactericidal activities were evaluated in blood neutrophils. Bacterial DNA, TNFα, IFNγ, IL-12p40, free serum infliximab/adalimumab levels and antidrug antibodies were measured.

RESULTS:

Bacterial DNA was found in 44% of patients with active disease versus 23% of patients with remitting disease (p=0.01). A NOD2-variant or ATG16L1-variant genotype was associated with bacterial DNA presence (OR 4.8; 95% CI 1.1 to 13.2; p=0.001; and OR 2.4; 95% CI 1.4 to 4.7; p=0.01, respectively). This OR was 12.6 (95% CI 4.2 to 37.8; p=0.001) for patients with a double-variant genotype. Bacterial DNA was associated with disease activity (OR 2.6; 95% CI 1.3 to 5.4; p=0.005). Single and double-gene variants were not associated with disease activity (p=0.19). Patients with a NOD2-variant genotype showed decreased phagocytic and bactericidal activities in blood neutrophils, increased TNFα levels in response to bacterial DNA and decreased trough levels of free anti-TNFα. The proportion of patients on an intensified biological therapy was significantly higher in the NOD2-variant groups.

CONCLUSIONS:

Our results characterise a subgroup of patients with CD who may require a more aggressive therapy to reduce the extent of inflammation and the risk of relapse.
 
NOD2 is needed for bacterial peptidoglycan detection, ATG16L1 is needed for cell autophagy of intracellular bacteria.

People with variants of those gene regions have more bacterial DNA, increased TNF-alpha in response to bacterial DNA, and they are on intesified anti TNF-alpha medication.

People with a more active disease also have more bacterial DNA.
 

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