title: IFN-γ promoter polymorphisms do not affect QuantiFERON® TB Gold In-Tube test results in a Canadian population.
abstract: Several studies have shown polymorphisms within the interferon-gamma (IFN-γ) promoter influence cytokine expression. The interferon-gamma release assay (IGRA) relies on the ability to produce IFN-γ in response to tuberculosis (TB) specific antigens. This study determined the relationship between the IFN-γ +874 A/T promoter polymorphism and the performance of the QuantiFERON®-TB Gold In-Tube (QFT-GIT) test in an ethnically diverse Canadian population.
  
  
  
  A total of 190 participants were categorised into three groups based on history of and exposure to TB: active TB (n = 55), TB exposed (n = 55) and presumably TB unexposed controls (n = 80). All participants underwent QFT-GIT testing, and DNA was extracted from whole blood and probed for polymorphism at position +874 (T/A) of intron 1 of IFN-γ. Statistical relationships between the QFT-GIT results, polymorphisms and demographic data were evaluated.
  
  
  
  IFN-γ +874 genotype frequencies among the entire study population (n = 190) were A/A (45.8%), T/A (39.5%), and T/T (14.7%). Among the three study groups, there was no correlation between QFT-GIT results and the IFN-γ +874 A/T genotype, and no correlation of genotype with IFN-γ production in response to either Mycobacterium tuberculosis antigens or mitogenic stimulation.
  
  
  
  Our results indicate that the IFN-γ +874 promoter polymorphism does not influence QFT-GIT performance in this study population.
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg , Departments of Medical Microbiology.
authors.forename: S
authors.initials: S
authors.lastname: Kiazyk
authors.affiliation: Departments of Medical Microbiology, Internal Medicine, Community Health Sciences.
authors.forename: L
authors.initials: L
authors.lastname: Larcombe
authors.affiliation: Departments of Medical Microbiology.
authors.forename: C
authors.initials: C
authors.lastname: Lopez
authors.affiliation: Departments of Medical Microbiology.
authors.forename: S
authors.initials: S
authors.lastname: Matyas
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg.
authors.forename: C
authors.initials: C
authors.lastname: Mesa
authors.affiliation: Departments of Medical Microbiology, Internal Medicine, Community Health Sciences.
authors.forename: P
authors.initials: P
authors.lastname: Orr
authors.affiliation: Departments of Medical Microbiology.
authors.forename: J
authors.initials: J
authors.lastname: Juno
authors.affiliation: Departments of Medical Microbiology.
authors.forename: J
authors.initials: J
authors.lastname: Waruk
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg , Departments of Medical Microbiology.
authors.forename: M
authors.initials: M
authors.lastname: Sharma
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg , Departments of Medical Microbiology, Immunology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: T B
authors.initials: TB
authors.lastname: Ball
mesh_terms: D000328:Adult; D000942:Antigens, Bacterial / Q000097:blood; D002170:Canada; D015331:Cohort Studies; D005260:Female; D005787:Gene Frequency; D006801:Humans; D007371:Interferon-gamma / Q000235:genetics*; D059425:Interferon-gamma Release Tests; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic; D014376:Tuberculosis / Q000097:blood / Q000175:diagnosis*
chemical_list: D000942:Antigens, Bacterial; C573415:IFNG protein, human; C072681:Mycobacterium tuberculosis antigens; D007371:Interferon-gamma