The CARD8 p.C10X mutation associates with a low anti-glycans antibody response in patients with Crohn's disease

Abstract

Background: Crohn's disease (CD) is associated with elevated anti-glycans antibody response in 60% of CD patients, and 25% of healthy first-degree relatives (HFDRs), suggesting a genetic influence for this humoral response. In mice, anti-glucan antibody response depends on the NLRP3 inflammasome. Here, we explored the effect of mutated CARD8, a component of the inflammasome, on anti-glycans antibody response in human.

Methods: The association between p.C10X mutation (rs2043211) of the CARD8 gene and the levels of anti-glycans antibody response was examined in 39 CD families. The family-based QTDT association test was used to test for the genetic association between CARD8 p.C10X mutation and anti-glycan antibodies in the pedigrees. The difference in antibody responses determined by ELISA was tested in a subgroup of CD probands (one per family) and in a subgroup of HFDRs using the Wilcoxon Kruskal Wallis non-parametric test.

Results: The QTDT familial transmission tests showed that the p.C10X mutation of CARD8 was significantly associated with lower levels of antibody to mannans and glucans but not chitin (p=0.024, p=0.0028 and p=0.577, for ASCA, ALCA and ACCA, respectively). These associations were independent of NOD2 and NOD1 genetic backgrounds. The p.C10X mutation significantly associated or displayed a trend toward lower ASCA and ALCA levels (p=0.038 and p=0.08, respectively) only in the subgroup of CD probands. Such associations were not significant for ACCA levels in both subgroups of CD probands and of HFDRs.

Conclusion: Our results show that ASCA and ALCA but not ACCA levels are under the influence of CARD8 genotype. Alteration of CARD8, a component of inflammasome, is associated with lower levels of antibodies directed to mannans and glucans at least in CD patients.

Figure 1

Measurement of anti-mannan antibody levels in human sera according to p.C10X genotype. Anti-mannan antibody (ASCA) levels were determined in sera from CD probands (A) and healthy first-degree relatives (B) by ELISA. Antibody titers (expressed in AU according to the reactivity of the manufacturer’s calibrator) in samples from subjects who were wild-type (C/C), heterozygous (C/X), or homozygous (X/X) for the p.C10X mutation. Positive or negative ASCA status was determined according to the cutoff value of 50 AU determined according to the manufacturer's instruction.

Figure 2

Measurement of anti-glucan antibody levels in human sera according to p.C10X genotype. Anti-glucan antibody (ALCA) levels were determined in sera from CD probands (A) and healthy first-degree relatives (B) by ELISA. Antibody titers (expressed in AU according to the reactivity of the manufacturer’s calibrator) in samples from subjects who were wild-type (C/C), heterozygous (C/X), or homozygous (X/X) for the p.C10X mutation. Positive or negative ALCA status was determined according to the cutoff value of 60 AU determined according to the manufacturer's instruction.