Evidence of interaction of CARD8 rs2043211 with NALP3 rs35829419 in Crohn's disease.

The location of CARD8 within an inflammatory bowel disease (IBD) locus and its role in the NALP3 inflammasome and as a nuclear factor (NF)kappaB inhibitor make it an attractive candidate risk gene for IBD. However, studies testing for the association of the CARD8 loss-of-function single-nucleotide polymorphism (SNP) rs2043211 with IBD have yielded mixed results. A recent study provided evidence that this discordance may result from an interaction of rs2043211 with loss-of-function variants in nucleotide-binding oligomerization domain protein 2 (NOD2) and a gain-of-function SNP (rs35829419) in NALP3. To confirm this interaction, we conducted a replication in an independent IBD sample set (n=1009 patients, n=517 controls). We found that the presence of the minor allele of rs2043211 with the major allele of rs35829419 conferred a protective effect against Crohn's disease (and vice versa), which intensified in the absence of NOD2 mutations (P(1,2/1,1)=0.009, odds ratio (OR)=0.66, 95% confidence interval (CI) (0.48-0.90); P(1,1/1,2)=0.015, OR=0.35, 95% CI (0.15-0.82)). We propose that these genotype combinations protect against gut inflammation by preventing the NALP3 inflammasome from producing excessive interleukin-1beta.