C Lefebvre

University of Antioquia, Antioquia, Departamento de Antioquia, Colombia

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Publications (8)35.83 Total impact

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    ABSTRACT: The molecular basis of genetic predisposition to pulmonary tuberculosis (PTB) in adults remains largely elusive. A chronic granulomatous inflammatory reaction is one of the main characteristics of the immune response to TB; however, a similar reaction is observed in other diseases, such as Crohn's disease. To assess the association of genetic polymorphisms previously associated with Crohn's disease and PTB in a Colombian population of PTB patients and controls. A case-control study was performed among 500 newly diagnosed PTB patients and 320 healthy control subjects. Thirty-one single nucleotide polymorphisms (SNPs) identified in a previous meta-analysis of genome-wide association studies of Crohn's disease were used for genotyping using MassARRAY technology. In this study, we identified an association with borderline significance (P = 0.0009433 and P = 0.029 after multiple testing by Bonferroni's correction) of SNP rs10995271 with PTB. SNP rs10995271 is in linkage disequilibrium with SNPs belonging to the zinc finger protein (ZNF365) gene. Our results suggest that human PTB shares a genetic basis with Crohn's disease, and that SNPs in the ZNF365 gene would have a role in the occurrence of chronic granulomatous inflammatory reaction in TB as well as Crohn's disease.
    The International Journal of Tuberculosis and Lung Disease 01/2014; 18(1):89-94. · 2.76 Impact Factor
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    ABSTRACT: Introduction: Interferon gamma (IFN ? ) is the most potent cytokine involved in the control of Mycobacterium tuberculosis ( Mtb ), the etiological agent of human tuberculosis (TB). Patients with active TB present reduced levels of IFN ? , which may explain the lack of effective immunity against Mtb in these patients. The diminished expression of or functional alterations in trans-acting factors that regulate IFN ? gene expression may explain the reduced levels of IFN ? in TB patients. Objective: To investigate the relationships of genetic variants in the transcription factors TBET, STAT1, STAT4, and HLX to susceptibility/resistance to pulmonary TB. Materials and methods: Eight candidate single-nucleotide polymorphisms (SNPs) were selected, and genotyped in 466 unrelated pulmonary TB patients and 300 healthy controls from Colombia, and the allelic and genetic associations with TB were analyzed. Results: The results indicate that no SNP in the transcription factors studied is associated with TB. However, polymorphism rs11650354 in the TBET gene may be associated with a decreased risk of TB; the TT genotype was significantly associated with TB protection in a recessive genetic model (OR=0.089, 95% CI: 0.01-0.73, p=0.0069), although this association was not maintained after multiple test correction (EMP2= 0.61). Conclusion: In this study, the rs11650354 variant of TBET was suggested to promote resistance to TB in a Colombian population. A future replication case-control study using additional samples will be necessary to confirm this suggestive association.
    Biomédica: revista del Instituto Nacional de Salud 06/2013; 33(2):259-67. · 0.32 Impact Factor
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    ABSTRACT: Immunological studies have supported the idea that innate immunity is critical for the control of Mycobacterium tuberculosis (Mtb) infection in humans. Despite the overwhelming evidence showing the critical role of Toll-like receptors (TLRs) in the in vitro recognition of Mtb, the in vivo significance of individual TLRs has been more difficult to demonstrate consistently. We were interested in examining the role of genes of TLRs and molecules involved in their signalling cascades, and a case-control study was designed to test the association of polymorphisms of these innate immune genes with pulmonary tuberculosis (TB) in a Colombian population. In this study, we did not find an association with TLR2, TLR4, TLR9, MyD88 or MAL/TIRAP polymorphic variants. These findings suggest that those genes are not involved as risk factors for pulmonary TB in our population.
    International Journal of Immunogenetics 01/2012; 39(3):216-23. · 1.36 Impact Factor
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    ABSTRACT: Immunological studies have supported the idea that innate immunity is critical for the control of Mycobac-terium tuberculosis (Mtb) infection in humans. Despite the overwhelming evidence showing the critical role of Toll-like receptors (TLRs) in the in vitro recognition of Mtb, the in vivo significance of individual TLRs has been more difficult to demonstrate consistently. We were interested in examining the role of genes of TLRs and molecules involved in their signalling cascades, and a case–control study was designed to test the association of polymorphisms of these innate immune genes with pulmonary tuberculosis (TB) in a Colombian popula-tion. In this study, we did not find an association with TLR2, TLR4, TLR9, MyD88 or MAL ⁄ TIRAP poly-morphic variants. These findings suggest that those genes are not involved as risk factors for pulmonary TB in our population.
    International Journal of Immunogenetics 01/2012; · 1.36 Impact Factor
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    ABSTRACT: Genetic susceptibility is known to play a large part in the predisposition to the inflammatory bowel diseases (IBDs) known as Crohn's disease (CD) and ulcerative colitis (UC). The IL2/IL21 locus on 4q27 is known to be a common risk locus for inflammatory disease (shown in coeliac disease, type 1 diabetes, rheumatoid arthritis, systemic lupus erythematosus and psoriasis), while the roles that interleukin 2 (IL2) and IL21 play in the immune response also make them attractive candidates for IBD. The objective of this study was to test for association between the IL2/IL21 locus and the IBDs. The four single nucleotide polymorphisms (SNPs) in the IL2/IL21 locus most associated with coeliac disease were genotyped in 1590 subjects with IBD and 929 controls from The Netherlands, and then replicated in a North American cohort (2387 cases and 1266 controls) and an Italian cohort (805 cases and 421 controls), yielding a total of 4782 cases (3194 UC, 1588 CD) and 2616 controls. Allelic association testing and a pooled analysis using a Cochran-Mantel-Haenszel test were performed. All four SNPs were strongly associated with UC in all three cohorts and reached genome-wide significance in the pooled analysis (rs13151961 p = 1.35 x 10(-10), rs13119723 p = 8.60 x 10(-8), rs6840978 p = 3.0 7x 10(-8), rs6822844 p = 2.77 x 10(-9)). A moderate association with CD was also found in the pooled analysis (p value range 0.0016-9.86 x 10(-5)). A strong association for the IL2/IL21 locus with UC was found, which also confirms it as a general susceptibility locus for inflammatory disease.
    Gut 03/2009; 58(6):799-804. · 10.73 Impact Factor
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    ABSTRACT: Inflammatory bowel disease (IBD) is a chronic disorder caused by multiple factors in a genetically susceptible host. Significant advances in the study of genetic susceptibility have highlighted the importance of the innate immune system in this disease. We previously completed a genome-wide linkage study and found a significant locus (IBD6) on chromosome 19p. We were interested in identifying the causal variant in IBD6. We performed a two-stage association mapping study. In stage 1, 1530 single-nucleotide polymorphisms (SNPs) were selected from the HapMap database and genotyped in 761 patients with IBD. Among the SNPs that passed the threshold for replication, 26 were successfully genotyped in 754 additional patients (stage 2). One intronic variant, rs273506, located in the microtubule-associated serine/threonine-protein kinase gene-3 (MAST3), was found to be associated in both stages (pooled P=1.8 x 10(-4)). We identified four MAST3 coding variants, including a non-synonymous SNP rs8108738, correlated to rs273506 and associated with IBD. To test whether MAST3 was expressed in cells of interest, we performed expression assays, which showed abundant expression of MAST3 in antigen-presenting cells and in lymphocytes. The knockdown of MAST3 specifically decreased Toll-like receptor-4-dependent NF-kappaB activity. Our findings are additional proofs of the pivotal role played by modulators of NF-kappaB activity in IBD pathogenesis.
    Genes and immunity 10/2008; 9(7):602-12. · 4.22 Impact Factor
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    ABSTRACT: Inflammatory bowel disease (IBD)--Crohn's disease (CD) and ulcerative colitis (UC)--and celiac disease are intestinal inflammatory disorders with a complex genetic background. Recently, two novel genes were found to be associated with IBD susceptibility. One, an uncommon coding variant (rs11209026) in the gene encoding for the interleukin-23 receptor (IL23R), conferred strong protection against CD. The other, rs2241880 in the autophagy-related 16-like 1 gene (ATG16L1), was associated with CD. We performed a case-control study for the association of IBD with IL23R and ATG16L1 in a Dutch cohort. We also looked at the association of IL23R and ATG16L1 with celiac disease. Five hundred eighteen Dutch white IBD patients (311 CD and 207 UC, including 176 trios of patients with both parents), 508 celiac disease patients, and 893 healthy controls were studied for association with the rs11209026 (IL23R) and rs2241880 (ATG16L1) single nucleotide polymorphisms (SNP). The rs11209026 SNP in IL23R had a protective effect for IBD in the case-control analysis (odds ratio [OR] 0.19, 95% confidence interval [CI] 0.10-0.37, P= 6.6E-09). Both CD (OR 0.14, CI 0.06-0.37, P= 3.9E-07) and UC (OR 0.33, CI 0.15-0.73, P= 1.4E-03) were associated with IL23R. For ATG16L1, the rs2241880 SNP was associated with CD susceptibility (OR 1.36, CI 1.12-1.66, P= 0.0017). The population-attributable risk of carrying allele G is 0.24 and is 0.19 for homozygosity for allele G in CD. No association was found between IL23R or ATG16L1 and celiac disease. We confirmed the association of IL23R and ATG16L1 with CD susceptibility and also the association of IL23R with UC. We found IL23R and ATG16L1 were not associated with celiac disease susceptibility.
    The American Journal of Gastroenterology 04/2008; 103(3):621-7. · 7.55 Impact Factor
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    ABSTRACT: Association mapping and candidate gene studies within inflammatory bowel diseases (IBD) linkage regions, as well as genome-wide association studies in Crohn's disease (CD) have led to the discovery of multiple risk genes, but these explain only a fraction of the genetic susceptibility observed in IBD. We have thus been pursuing a region on chromosome 3p21-22 showing linkage to CD and ulcerative colitis (UC) using a gene-centric association mapping approach. We identified 12 functional candidate genes by searching for literature cocitations with relevant keywords and for gene expression patterns consistent with immune/intestinal function. We then performed an association study composed of a screening phase, where tagging single nucleotide polymorphisms (SNPs) were evaluated in 1,020 IBD patients, and an independent replication phase in 745 IBD patients. These analyses identified and replicated significant association with IBD for four SNPs within a 1.2 Mb linkage disequilibrium region. We then identified a non-synonymous coding variant (rs3197999, R689C) in the macrophage-stimulating 1 (MST1) gene (P-value 3.62 x 10(-6)) that accounts for the association signal, and shows association with both CD and UC. MST1 encodes macrophage-stimulating protein (MSP), a protein regulating the innate immune responses to bacterial ligands. R689C is predicted to interfere with MSP binding to its receptor, suggesting a role for this gene in the pathogenesis of IBD.
    Mucosal Immunology 04/2008; 1(2):131-8. · 7.54 Impact Factor

Publication Stats

188 Citations
35.83 Total Impact Points

Institutions

  • 2012
    • University of Antioquia
      • Facultad de Medicina
      Antioquia, Departamento de Antioquia, Colombia
  • 2008–2012
    • Montreal Heart Institute
      • Research Centre
      Montréal, Quebec, Canada
    • Université de Montréal
      Montréal, Quebec, Canada
    • Université du Québec à Montréal
      Montréal, Quebec, Canada
  • 2009
    • University of Groningen
      • Department of Gastroenterology and Hepatology
      Groningen, Province of Groningen, Netherlands