Phenotypic and Functional Changes in Peripheral Blood Natural Killer Cells in Crohn Disease Patients.

We investigated activation status, cytotoxic potential, and gut homing ability of the peripheral blood Natural Killer (NK) cells in Crohn disease (CD) patients. For this purpose, we compared the expression of different activating and inhibitory receptors (KIR and non-KIR) and integrins on NK cells as well as their recent degranulation history between the patients and age-matched healthy controls. The study was conducted using freshly obtained peripheral blood samples from the study participants. Multiple color flow cytometry was used for these determinations. Our results show that NK cells from treatment-naïve CD patients expressed higher levels of activating KIR as well as other non-KIR activating receptors vis-à-vis healthy controls. They also showed increased frequencies of the cells expressing these receptors. The expression of several KIR and non-KIR inhibitory receptors tended to decrease compared with the cells from healthy donors. NK cells from the patients also expressed increased levels of different gut-homing integrin molecules and showed a history of increased recent degranulation events both constitutively and in response to their in vitro stimulation. Furthermore, treatment of the patients tended to reverse these NK cell changes. Our results demonstrate unequivocally, for the first time, that peripheral blood NK cells in treatment-naïve CD patients are more activated and are more poised to migrate to the gut compared to their counterpart cells from healthy individuals. Moreover, they show that treatment of the patients tends to normalize their NK cells. The results suggest that NK cells are very likely to play a role in the immunopathogenesis of Crohn disease.

Activating Killer-cell Immunoglobulin-like Receptor genes confer risk for Crohn's disease in children and adults of the Western European descent: Findings based on case-control studies.

BACKGROUND: Killer-cell Immunoglobulin-like Receptor (KIR) genes encode receptors, which are mainly expressed on, and control functional activities of, Natural Killer (NK) cells. There exist six distinct activating KIR genes in humans, who differ from one another with respect to the repertoire of these genes. Because activated NK cells can potentially cause tissue destruction, we hypothesized that variation in the inherited activating KIR genes in humans is associated with their innate susceptibility/resistance to developing Crohn disease (CD). METHODS: We performed case control studies on three independent Canadian CD patient cohorts (all of the Western European descent): two comprising children (Montreal having 193 cases and 245 controls, and Ottawa having 93 cases and 120 controls) and the third one comprising predominantly adults (Winnipeg having 164 cases and 200 controls). We genotyped cases and controls for activating KIR genes by PCR with gene-specific primers and investigated associations between the genes and cases using unconditional logistic regression. RESULTS: We observed strong associations between all the six KIR genes and CD in Ottawa children, with the strongest risk observed for the KIR2DS1 (p = 1.7 x10-10). Associations between all but the KIR2DS2 were replicated in the Montreal cohort with the strongest association evident for the KIR2DS5 (8.0 x 10-10). Similarly associations between five genes were observed in the adult Winnipeg cohort. In this cohort, strongest associations were evident with the KIR2DS5 (8.75 x 10-8). An overall analysis for all cohorts showed strong associations with four of the genes, with the strongest association evident for the KIR2DS5 (p = 1.35 x 10-17). In the combined analysis for four KIR genes, individuals carrying one or more of the KIR genes were at significantly higher risks for acquiring CD (p = 3.5 x 10-34). CONCLUSIONS: Activating KIR genes are associated with risk for developing CD in both children and adults.

Parental occupations and risk for Crohn's disease in children.

BACKGROUND AND OBJECTIVES: Lacunae exist on the identity of specific environmental risk factors that associate with Crohn's disease (CD). We hypothesized that indirect exposures acquired via the parents' occupation may confer susceptibility. METHODS: A case-control study based on children diagnosed with CD (prior to age 20) at a tertiary care gastroenterology clinic in Montreal, Canada was carried out. Population- and hospital-based controls without IBD were selected. Information on occupations held by the parents was acquired from interview. Jobs were coded using the Canadian National Occupational Classification for Statistics. Associations were examined using logistic regression accounting for potential confounders. Odds ratios (OR) and corresponding 95% confidence intervals (CI) were estimated. RESULTS: A total of 466 cases and 335 controls were studied. The mean (±SD) age of the cases (12.4 ± 3.2) was slightly higher than controls (10.5 ± 4.9). Gender and ethnicity were equally distributed between the groups. Logistic regression analysis suggested that children whose fathers worked as retail salespersons/sales clerks [odds ratio (OR) 3.6, 95% confidence interval (CI) 1.2-11.1], and whose mothers worked as administrative secretaries (OR 3.2, 95% CI 1.6-6.4), were more likely to be at risk for CD. Mothers who worked as either early childhood educators (OR 2.3, 95% CI 0.85-6.2) or as clerks (OR 2.8, 95% CI 0.8-9.9) also appeared to confer risks, but these associations were statistically not significant. CONCLUSION: Parental occupations related to 'social mixing' that can potentially enhance exposure to infectious agents, appear to confer higher risk for CD in children.

Steroid Administration and Growth Impairment in Children with Crohn's Disease.

BACKGROUND: Growth impairment remains a major concern in children with Crohn's disease, but evidence remains unclear, in particular, whether steroid use is implicated. We aimed to (1) determine the frequency of temporary (TGI) and permanent (PGI) growth impairment in children administered steroids and (2) examine whether cumulative steroid administration was associated with TGI and/or PGI. METHODS: A retrospective cohort study was performed in patients with Crohn's disease (<18 yr) administered steroids at the gastroenterology clinics of Sainte-Justine Hospital, Montreal. Steroid dosage, height during follow-up, adult height (after age 20), and parental heights were ascertained. Patients with height z score <-1.64 on more than 1 occasion before age 18 were considered as patients with TGI. Patients with adult heights <8.5 cm below the expected target heights were considered as patients with PGI. Association between steroid dosage and TGI/PGI was studied using logistic regression analyses. Data from the Swiss IBD Cohort Study were analyzed for comparison. RESULTS: A total of 221 children were studied. Approximately 19% (42/221) children were deemed as TGI, and 8/137 patients (5.8%) had PGI. TGI was associated with diagnosis at younger age (P value 0.002) and steroid administration at younger age (P value 0.001), but not with steroid dosage. Final adult height was associated with target height, but not with cumulative steroid dosage. Rates of PGI in the Swiss cohort were ∼ 9.1% in steroid users and 2.7% in nonusers. CONCLUSIONS: Most children with TGI attain normal adult heights. Cumulative steroid use does not seem to be associated with either TGI or PGI in children with Crohn's disease.

Interactions between the dietary polyunsaturated fatty acid ratio and genetic factors determine susceptibility to pediatric Crohn's disease.

Increased dietary ratios of ω6/ω3 polyunsaturated fatty acids have been implicated in the pathogenesis of Crohn's disease (CD), but epidemiologic data are limited. We investigated whether variants of genes that control polyunsaturated fatty acid metabolism (CYP4F3, FADS1, and FADS2), along with the dietary ratio of ω6/ω3, confers susceptibility to CD. Based on data from 182 children newly diagnosed with CD and 250 controls, we found that children who consumed a higher dietary ratio of ω6/ω3 were susceptible for CD if they were also carriers of specific variants of CYP4F3 and FADS2 genes. Our findings implicate diet-gene interactions in the pathogenesis of CD.

A non-synonymous coding variant (L616F) in the TLR5 gene is potentially associated with Crohn's disease and influences responses to bacterial flagellin.

BACKGROUND AND OBJECTIVES: Although numerous studies have implicated TLR5, or its ligands, bacterial flagellins, in the pathogenesis of Crohn's disease (CD), genome-wide association studies (GWAS) have not reported associations with the TLR5 gene. We aimed to examine potential CD-associated TLR5 variants and assess whether they modified inflammatory responses to bacterial flagellins. METHODS AND PRINCIPAL RESULTS: A two-stage study was carried out. In stage 1, we genotyped tagging single-nucleotide polymorphisms (tag-SNPs) in the TLR5 gene in a sample of CD cases (<20 years of age, N = 566) and controls (N = 536). Single SNP and haplotype analysis was carried out. In Stage 2, we assessed the functional significance of potential CD-associated variant(s) vis-à-vis effects on the inflammatory response to bacterial flagellin using HEK293T cells. We observed marginal association between a non-synonymous coding SNP rs5744174 (p = 0.05) and CD. Associations between SNP rs851139 that is in high linkage disequilibrium (LD) with SNP rs5744174 were also suggested (p = 0.07). Haplotype analysis revealed that a 3 marker haplotype was significantly associated with CD (p = 0.01). Functional studies showed that the risk allele (616F) (corresponding to the C allele of SNP rs5744174) conferred significantly greater production of CCL20 in response to a range of flagellin doses than the comparator allele (616L). CONCLUSIONS: Our findings suggest that a non-synonymous coding variation in the TLR5 gene may confer modest susceptibility for CD.

Genome-wide association study signal at the 12q12 locus for Crohn's disease may represent associations with the MUC19 gene.

BACKGROUND: Genome-wide association studies (GWAS) in Crohn's disease (CD) have identified associations with single-nucleotide polymorphism (SNP) rs11175593 at chromosome 12q12. The MUC19 and LRRK2 genes reside close to the GWAS signal, but it is as yet unclear which of the 2 genes represent the CD susceptibility genes. METHODS: We studied associations between nonsynonymous coding variants in the MUC19 (5) and LRRK2 (3) genes in a case-control sample comprising CD cases aged <18 years at diagnosis. The GWAS lead SNP rs11175593 was also investigated. Allelic, genotype, and haplotype associations were examined assuming different models of inheritance. RESULTS: A total of 530 cases and 600 controls were studied. The mean (±SD) age at diagnosis was 12.4 (±3.3). Most cases were male (57.4%). Most patients had ileocolonic disease location (48.8%) and inflammatory behavior at diagnosis (87.0%). Three MUC19 SNPs were nominally significantly associated with CD (rs11564245, Asp→His: P = 0.02; rs4768261, Ser→Phe: P = 0.0008; and rs2933353, Glu→Ala: P = 0.01). Associations with rs4768261 were maintained after corrections for multiple comparisons (permuted, P = 0.007). None of the LRRK2 SNPs were associated with CD. Haplotype analysis supported the single SNP associations noted with the MUC19 gene. CONCLUSIONS: GWAS signal at chromosome 12q12 for CD may represent associations with the MUC19 gene.

Association between the PTPN2 gene and Crohn's disease: dissection of potential causal variants.

BACKGROUND: Although genome-wide association studies (GWAS) and subsequent meta-analyses have confirmed associations between the PTPN2 (protein tyrosine phosphatase, nonreceptor type 2) gene and Crohn's disease (CD), the potential causal variants remain unidentified. We aimed to dissect potential causal CD-associated PTPN2 variants, assess their functional significance, and relate PTPN2 protein expression with inflammation in CD. METHODS: A 3-stage study was carried out. In stage 1, we genotyped tagging single nucleotide polymorphisms (tag-SNPs) in the PTPN2 gene in a sample of patients with CD (<20 years, n = 556) and controls (n = 602). In stage 2, we resequenced the putative promoter, target exons and introns in the PTPN2 gene, and examined associations with high-frequency variants with CD in the stage 1 cohort. In stage 3 we studied the relationship between PTPN2 protein expression and mucosal inflammation and carried out in silico analyses to study the functional characteristics of the PTPN2 CD-associated SNPs. RESULTS: In stage 1, we observed associations between 5 intronic SNPs and CD including rs1893217 (P = 2 × 10⁻4), the SNP that is in perfect linkage disequilibrium with the lead genome-wide association studies SNP rs2542151. Resequencing revealed 2 known promoter polymorphisms. No associations between these promoter SNPs and CD were evident. In silico analyses revealed that the 5 associated intronic SNPs influenced PTPN2 expression and binding to important transcription factors. PTPN2 protein was overexpressed in inflamed intestinal tissues of patients with CD. CONCLUSIONS: Our findings suggest that noncoding variation in the PTPN2 gene may represent the causal variations influencing susceptibility for CD.

Herpes simplex virus-1 infection of colonic explants as a model of viral-induced activation of Crohn's disease.

The exogenous triggers responsible for Crohn's disease (CD) relapses are not often identified. Cytomegalovirus and other members of the herpesvirus family have been implicated in precipitating relapses. However, the role of viral infections in the immunopathogenesis of CD remains poorly understood. We describe an ex-vivo model of primary viral infection of CD tissue with Herpes Simplex Virus type I (HSV-1). IL-6 and CD68 served as markers for CD inflammation, type I IFNs for viral infection. Colonic explants obtained from CD resections were infected via the luminal or the submucosal compartments with HSV-1 or mock virus solution, at varying concentrations for up to 20 h. Serial tissue sections were assayed for expression of HSV-1 specific antigens, CD-68, IL-6 and DC-SIGN. Culture supernatants were tested for IL-6 and type I IFN production. Positive immunostaining for HSV-1 specific antigens was consistently detectable using 11×10(6)PFU from 13 h onwards, mainly on cells located in the submucosa, and in the perivascular area. CD68 was up-regulated in lamina propria macrophages from mildly and non-inflamed CD tissue after HSV-1 infection. IL-6+ cells in the infected tissues were mainly submucosal DC-SIGN+ dendritic cells. IL-6 and IFN-ß levels were higher in the supernatants from HSV-1-infected explants compared to controls after 20 h of culture (p<0.01). These data show increased expression of inflammatory markers during the initial stages of HSV-1 primary infection using CD colonic explants. This in vitro model appears promising to study the immunoregulatory changes induced by microbial infection in reactivation of CD.

NELL1, NCF4, and FAM92B genes are not major susceptibility genes for Crohn's disease in Canadian children and young adults.

BACKGROUND: Genome-wide association studies (GWAS) and replication studies have shown conflicting associations between the NELL1, NCF4, and FAM92B genes and susceptibility for Crohn's disease (CD). We sought to examine whether these genes were associated with CD in Canadian children and young adults. METHODS: A case-control study was carried out at three pediatric gastroenterology clinics across Canada. Patients, ≤20 years at diagnosis, along with controls representative of the general population were selected. Study subjects were genotyped for 22 single nucleotide polymorphisms (SNPs) across the target genes. Allelic and haplotype associations were examined. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were estimated. RESULTS: In all, 566 CD cases and 602 controls were investigated. The mean (±SD) age of the patients was 12.3 (±3.3) years. Most patients were male (57.8%), of Caucasian ancestry (98.2%), and had ileocolonic disease location (48.8%). Barring nominal associations with one FAM92B SNP, none of the other 21 SNPs analyzed were associated with CD either at the allelic or haplotype level. Separate analysis for ileal CD (L1 plus L3) also did not reveal significant associations with any of the SNPs. Similarly, a pooled analysis using data from two recent studies did not demonstrate associations between the NCF4 (OR = 1.10, 95% CI = 0.91-1.32, P = 0.32) and FAM92B (OR = 1.05, 95% CI = 0.95-1.17, P = 0.36) GWAS lead SNPs and ileal CD. CONCLUSIONS: GWAS-reported associations in the NELL1, NCF4, and FAM92B genes could not be replicated in Canadian children and young adults. Further investigation in other populations will be required to confirm the presence/absence of associations, if any.

Variation in the glucocorticoid receptor gene (NR3C1) may be associated with corticosteroid dependency and resistance in children with Crohn's disease.

OBJECTIVES: In pediatric onset of Crohn's disease (CD), corticosteroid dependency (approximately 40%) and resistance (approximately 10%) are significant clinical problems. Given the known effects of the glucocorticoid receptor (GR/NR3C1) gene in corticosteroid metabolism, we investigated whether variation in the gene was associated with corticosteroid response. METHODS: A retrospective cohort study was carried out including patients with CD diagnosed before 18 years and treated with a first course of corticosteroids in two Canadian tertiary pediatric gastroenterology clinics. DNA was obtained from blood or saliva. Tagging single nucleotide polymorphisms (SNPs) and functionally important SNPs were genotyped. Allelic, genotype, and haplotype associations between the glucocorticoid receptor SNPs and response to corticosteroids were examined. RESULTS: A total of 296 corticosteroid-resistant, corticosteroids-dependent, and corticosteroid-responsive patients with CD were studied. Of the 12 SNPs examined, four markers, rs6196 [odds ratio (OR)=2.03; 95% confidence interval (CI): 1.03-4.0; P=0.042], rs7701443 (OR=3.43; 95% CI: 1.79-6.57; P=0.042), rs6190 (OR=4.84; 95% CI: 1.70-13.80; P=0.003), and rs860457 (OR=3.43; 95% CI: 1.79-6.57; P<0.001) were associated at the allelic level with corticosteroid resistance. Haplotype analysis of four associated markers revealed associations between two haplotypes and corticosteroid resistance (P values of 0.046 and 0.001). Three SNPs, rs10482682 (OR=1.43; 95% CI: 0.99-2.08; P=0.047), rs6196 (OR=0.55; 95% CI: 0.31-0.95; P=0.024), and rs2963155 (OR=0.64; 95% CI: 0.42-0.98; P=0.039), showed associations under an additive model, whereas rs4912911 (OR=0.37; 95% CI: 0.13-1.00; P=0.03) and rs2963156 (OR=0.32; 95% CI: 0.07-1.12; P=0.047) showed associations under a recessive model with corticosteroid dependence. Two five-marker haplotypes were associated with corticosteroid dependence (P values 0.002 and 0.004). CONCLUSION: Our results suggest that variations in the GR/NR3C1 gene are associated with corticosteroid resistance and dependency in pediatric-onset CD. Studies are required to replicate these findings and to identify the potentially relevant variants.

Novel associations between activating killer-cell immunoglobulin-like receptor genes and childhood leukemia.

Acute lymphoblastic leukemia of pre-B cells (pre-B ALL) is the most frequent form of leukemia affecting children in Western countries. Evidence is accumulating that genetic factors play an important role in conferring susceptibility/resistance to leukemia in children. In this regard, activating killer-cell immunoglobulin-like receptor (KIR) genes are of particular interest. Humans may inherit different numbers of the 6 distinct activating KIR genes. Little is known about the impact of this genetic variation on the innate susceptibility or resistance of humans to the development of B-ALL. We addressed this issue by performing a case-control study in Canadian children of white origin. Our results show that harboring activating KIR genes is associated with reduced risk for developing B-ALL in these children. Of the 6 activating KIR genes, KIR2DS2 was maximally associated with decreased risk for the disease (P = 1.14 × 10(-7)). Furthermore, our results showed that inheritance of a higher number of activating KIR genes was associated with significant reductions in risk for ALL in children. These results were also consistent across different ALL phenotypes, which included children with pre-T cell ALL. Our study provides novel insights concerning the pathogenesis of childhood leukemia in white children and has implications for the development of new immunotherapies for this cancer.

Immediate and long-term outcomes of corticosteroid therapy in pediatric Crohn's disease patients.

BACKGROUND: Although a mainstay of treatment of moderate to severe Crohn's disease (CD), corticosteroids use presents significant challenges because of large interindividual variability in response. Corticosteroid-dependence is of particular concern in children, where high rates have been reported. We examined the burden of corticosteroid-resistance and dependence in a well-characterized cohort of pediatric CD patients and investigated potential predictors of response. METHODS: Children diagnosed with CD (<18 years), were recruited from two Canadian pediatric gastroenterology clinics. Immediate and long-term responses to corticosteroid therapy were retrospectively ascertained. Response rates (resistance and dependence) were estimated and potential predictors assessed using logistic regression analysis. RESULTS: Of the 645 CD patients, 364 (56.2%) received corticosteroids. The frequency of corticosteroid-resistance was (8.0%) (95% confidence interval [CI]: 5.0%-11%) and 40.9% (95% CI: 39.0%-46.0%) became dependent. In univariate analysis female gender (odds ratio [OR] = 2.49, 95% CI: 1.1-5.5, P = 0.025), disease severity (OR = 2.43, 95% CI: 1.10-5.38, P = 0.029), and complicated disease (OR = 2.75, 95% CI: 1.18-6.41, P = 0.019) were associated with resistance. In multivariate analysis lower age at diagnosis (OR = 1.34,95% CI: 1.03-3.01, P = 0.040), coexisting upper digestive tract involvement (OR = 1.35, 95% CI: 1.06-3.07, P = 0.031), and concomitant immunomodulator use (OR = 0.35, 95% CI: 0.16-0.75, P = 0.007) were significantly associated with steroid dependency. CONCLUSIONS: Our results demonstrate that steroid dependency is a frequent complication in children with CD. Children with an earlier age at diagnosis and coexisting upper digestive tract involvement could be potentially targeted for steroid-sparing therapy.

Genes involved in the metabolism of poly-unsaturated fatty-acids (PUFA) and risk for Crohn's disease in children & young adults.

BACKGROUND AND OBJECTIVES: Epidemiological evidence for the role of polyunsaturated fatty-acids (PUFA) in Crohn's disease (CD) is unclear, although the key metabolite leucotriene B4 (LTB(4)) is closely linked to the inflammatory process. We hypothesized that inherited variation in key PUFA metabolic enzymes may modify susceptibility for CD. METHODS AND PRINCIPAL RESULTS: A case-control design was implemented at three pediatric gastroenterology clinics in Canada. Children ≤20 yrs diagnosed with CD and controls were recruited. 19 single nucleotide polymorphisms (SNPs) across the ALOX5 (4) CYP4F3 (5) and CYP4F2 (10) genes, were genotyped. Associations between SNPs/haplotypes and CD were examined. A total of 431 cases and 507 controls were studied. The mean (±SD) age of the cases was 12.4 (±3.3) years. Most cases were male (56.4%), had ileo-colonic disease (L3±L4, 52.7%) and inflammatory behavior (B1±p, 87%) at diagnosis. One genotyped CYP4F3 SNP (rs2683037) not in Hardy-Weinberg Equilibrium was excluded. No associations with the remaining 4 CYP4F3 SNPs with CD were evident. However haplotype analysis revealed associations with a two-marker haplotype (TG) (rs3794987 & rs1290617) (p = 0.02; permuted p = 0.08). CYP4F2 SNPs, rs3093158 (OR (recessive) = 0.56, 95% CI = 0.35-0.89; p = 0.01), rs2074902 (OR (trend) = 1.26, 95% CI = 1.00-1.60; p = 0.05), and rs2108622 (OR (recessive) = 1.6, 95% CI = 1.00-2.57; p = 0.05) were significantly associated whereas rs1272 (OR (recessive) = 0.58, 95% CI = 0.30-1.13; p = 0.10) showed suggestions for associations with CD. A haplotype comprising these 4 SNPs was significantly associated (p = 0.007, permuted p = 0.02) with CD. Associations with SNP rs3780901 in the ALOX5 gene were borderline non-significant (OR (dominant) = 1.29, 95% CI = 0.99-1.67; p = 0.056). A haplotype comprising the 4 ALOX5 SNPs (TCAA, p = 0.036) was associated with CD, but did not withstand corrections for multiple comparisons (permuted p = 0.14). CONCLUSIONS: Inherited variation in enzymes involved in the synthesis/metabolism of LTB(4) may be associated with CD. These findings implicate PUFA metabolism as a important pathway in the CD pathogenesis.

Association between genome-wide association studies reported SNPs and pediatric-onset Crohn's disease in Canadian children.

A recent pediatric-focused genome-wide association study has implicated three novel susceptibility loci for Crohn' disease (CD).We aimed to investigate whether the three recently reported and other previously reported genes/loci were also associated with CD in Canadian children. A case-control design was implemented at three pediatric gastroenterology clinics in Canada. Children <19 years of age with a confirmed diagnosis of CD were recruited along with controls. Single nucleotide polymorphisms (SNPs) in 19 reported genes/loci were genotyped. Associations between individual SNPs and CD were examined. A total of 563 cases and 553 controls were studied. The mean (+/-SD) age of the cases was 12.3 (+/-3.2) years. Most cases were male (56.0%), had ileo-colonic disease (L3 +/- L4, 48.8%) and inflammatory behavior (B1 +/- p, 87.9%) at diagnosis. Allelic association analysis (two-tailed) showed that 8 of the 19 targeted SNPs were significantly associated with overall susceptibility for CD. Associations with one additional SNP was borderline non-significant. Significantly associated SNPs included SNPs rs1250550 (p = 0.026) and rs8049439 (p = 0.04), recently reported to be specifically associated with pediatric-onset CD.Based on the results, we confirmed associations between two of the three novel pediatric-CD loci and other regions reported for associations with either pediatric and/or adult-onset CD.

Investigation of reported associations between the 20q13 and 21q22 loci and pediatric-onset Crohn's disease in Canadian children.

OBJECTIVES: A recent pediatric-focused genome-wide association study has reported novel associations of the 20q13 and 21q22 loci with inflammatory bowel disease (IBD). We aimed to investigate these associations with Crohn's disease (CD) in Canadian children. METHODS: A combined case-control and case-parent design was implemented at three pediatric gastroenterology clinics in Canada. Children less than 20 years of age with a confirmed diagnosis of CD were recruited along with controls. For a subset of the patients, biological parents were also recruited. Three single-nucleotide polymorphisms (SNPs) at the 20q13 locus and 1 SNP at the 21q22 locus were genotyped. Associations between individual SNPs and haplotypes were examined. RESULTS: A total of 410 cases, 415 controls, and 302 parents were studied. The mean (+/-s.d.) age for the cases was 12.3 (+/-3.2) years. Most cases were men (56.1%) who had ileocolonic disease (L3+/-L4, 52.2%) and inflammatory behavior (B1+/-B4, 87.0%) at diagnosis. Single SNP analysis showed that all 3 SNPs at the 20q13 locus were significantly associated with CD (rs2297441, P=2.24x10(-4); rs2315008, P=4.77x10(-4); rs4809330, P=6.08x10(-3)). Haplotype analysis suggested that the association signal at 20q13 resided on a common haplotype comprising the minor allele of rs2297441 (P=2.8x10(-5)). SNP rs2836878 at the 21q22 locus showed a trend for association with CD that was statistically not significant (P=0.06). CONCLUSIONS: Our results support an association between the 20q13 locus and CD in Canadian children. Positional cloning studies are required to further dissect the potential causative genes in the region.

Associations between ABCB1/MDR1 gene polymorphisms and Crohn's disease: a gene-wide study in a pediatric population.

BACKGROUND: Functional studies support the involvement of the MDR1 gene in the pathways leading to Crohn's disease (CD). Two common single nucleotide polymorphisms (SNPs), C3435T and G2677T/A, thought to alter the function of the corresponding P-glycoprotein, have shown inconsistent associations with CD. We investigated whether DNA variants in the MDR1 gene were associated with susceptibility for CD and specific phenotypes in children. METHODS: A case-control study was conducted at 3 gastroenterology clinics across Canada. Children with CD and population- or hospital-based controls were included. CD cases were classified using the Montreal Classification. Thirteen tag-SNPs and the C3435T variant in the MDR1 gene were genotyped. Single-SNP allelic, genotype as well as gene-wide haplotype associations with CD and its phenotypes at diagnosis were assessed. RESULTS: A total of 270 CD cases and 336 controls were studied. Most cases were male (56.3%), had disease location L3+/-L4 (58.1%), and an inflammatory phenotype B1+/-p (88.5%). Allelic association analysis revealed that SNP rs17327442 was significantly associated with overall susceptibility to CD (odds ratio [OR] = 0.72, 95% confidence interval [CI] = 0.50-0.99, P = 0.04) but this association did not withstand corrections for multiple testing (q-value = 0.56). Genotype-phenotype analysis indicated that 2 SNPs (rs10248420, P = 0.007, q-value = 0.07; rs2032583, P = 0.01, q-value = 0.07) were significantly associated with colonic disease. Five SNPs, rs1128503 (P = 0.02), rs1202184 (P = 0.008), rs1202186 (P = 0.02), rs2091766 (P = 0.03), and rs2235046 (P = 0.03) were nominally associated with noninflammatory CD. Specific haplotypes comprising of the tag-SNPs were significantly associated with either colonic or noninflammatory CD. CONCLUSIONS: Our comprehensive gene-wide analysis suggests that the MDR1 gene may be associated with clinical phenotypes of CD in children.

Autophagy gene ATG16L1 but not IRGM is associated with Crohn's disease in Canadian children.

BACKGROUND: Recent genome-wide studies have implicated the autophagy genes ATG16L1 and IRGM in the pathogenesis of Crohn's disease (CD). We investigated whether these genes were associated with CD in Canadian children. METHODS: A case-control study was carried out at 2 pediatric gastroenterology clinics in Canada. Confirmed cases of CD <20 years diagnosed using standard criteria were classified according to the Montreal Classification scheme. Single nucleotide polymorphisms (SNPs) rs2241880 (ATG16L1) and rs10065172 (IRGM) along with CARD15 SNPs, SNP8, SNP12, and SNP13 were genotyped. RESULTS: A total of 289 CD cases and 290 controls were studied. The mean age (+/-SD) of the cases was 12.1 (+/-3.5) years of age. Most cases were male (55.4%), had disease location L3 +/- L4 (56.7%), and an inflammatory phenotype B1 +/- p (87.2%) at diagnosis. rs2241880 (ATG16L1) was strongly associated with CD (allelic P = 1.24 x 10(-6)). Children with GG genotype had a more than 3-fold elevated risk for disease as compared to the wildtype AA homozygotes (odds ratio [OR], 3.1; 95% confidence interval [CI], 1.93-4.94; P = 1.8 x 10(-6)). Association with SNP rs2241880 was specific for ileal disease (with or without colonic involvement) (case-based allelic P = 0.02; P-value versus controls = 9.5 x 10(-8)). The frequency of IRGM SNP rs10065172 was higher in cases but differences with controls were not statistically significant. No interactions between CARD15 and either ATG16L1 or IRGM were evident. CONCLUSIONS: We have confirmed associations between CD and ATG16L1 in a pediatric cohort of Canadian children. Associations with IRGM need to be further evaluated in larger studies.

Procalcitonin and C-reactive protein as markers of bacterial infection in critically ill children at onset of systemic inflammatory response syndrome.

OBJECTIVE: To compare the accuracy of procalcitonin and C-reactive protein as diagnostic markers of bacterial infection in critically ill children at the onset of systemic inflammatory response syndrome (SIRS). DESIGN: Prospective cohort study. SETTING: Tertiary care, university-affiliated pediatric intensive care unit (PICU). PATIENTS: Consecutive patients with SIRS. INTERVENTIONS: From June to December 2002, all PICU patients were screened daily to include cases of SIRS. At inclusion (onset of SIRS), procalcitonin and C-reactive protein levels as well as an array of cultures were obtained. Diagnosis of bacterial infection was made a posteriori by an adjudicating process (consensus of experts unaware of the results of procalcitonin and C-reactive protein). Baseline and daily data on severity of illness, organ dysfunction, and outcome were collected. MEASUREMENTS AND MAIN RESULTS: Sixty-four patients were included in the study and were a posteriori divided into the following groups: bacterial SIRS (n = 25) and nonbacterial SIRS (n = 39). Procalcitonin levels were significantly higher in patients with bacterial infection compared with patients without bacterial infection (p = .01). The area under the receiver operating characteristic curve for procalcitonin was greater than that for C-reactive protein (0.71 vs. 0.65, respectively). A positive procalcitonin level (>or=2.5 ng/mL), when added to bedside clinical judgment, increased the likelihood of bacterial infection from 39% to 92%, while a negative C-reactive protein level (<40 mg/L) decreased the probability of bacterial infection from 39% to 2%. CONCLUSIONS: Procalcitonin is better than C-reactive protein for differentiating bacterial from nonbacterial SIRS in critically ill children, although the accuracy of both tests is moderate. Diagnostic accuracy could be enhanced by combining these tests with bedside clinical judgment.