Association between IFNA genotype and the risk of sarcoidosis

Variation in the type I interferon gene cluster on 9p21 influences susceptibility to asthma and atopy

A genome-wide screen for asthma and atopy susceptibility alleles conducted in the Hutterites, a founder population of European descent, reported evidence of linkage with a short tandem repeat polymorphism (STRP) within the type I interferon (IFN) gene cluster on chromosome 9p21. The goal of this study was to identify variation within the IFN gene cluster that influences susceptibility to asthma and atopic phenotypes. We screened approximately 25 kb of sequence, including the flanking sequence of all 15 functional genes and the single coding exon in 12, in Hutterites representing different IFNA-STRP genotypes. We identified 78 polymorphisms, and genotyped 40 of these (in 14 genes) in a large Hutterite pedigree. Modest associations (0.003<P<0.05) with asthma, bronchial hyper-responsiveness (BHR), and atopy were observed with individual variants or genes, spanning the entire 400 kb region. However, pairwise combinations of haplotypes between genes showed highly significant associations with different phenotypes (P<10(-5)) that were localized to specific pairs of genes or regions of this cluster. These results suggest that variation in multiple genes in the type I IFN cluster on 9p22 contribute to asthma and atopy susceptibility, and that not all genes contribute equally to all phenotypes.

Genetic polymorphisms and susceptibility to lung disease

Susceptibility to infection by bacterium such as Bacillus anthracis has a genetic basis in mice and may also have a genetic basis in humans. In the limited human cases of inhalation anthrax, studies suggest that not all individuals exposed to anthrax spores were infected, but rather, individuals with underlying lung disease, particularly asthma, sarcoidosis and tuberculosis, might be more susceptible. In this study, we determined if polymorphisms in genes important in innate immunity are associated with increased susceptibility to infectious and non-infectious lung diseases, particularly tuberculosis and sarcoidosis, respectively, and therefore might be a risk factor for inhalation anthrax. Examination of 45 non-synonymous polymorphisms in ten genes: p47phox (NCF1), p67phox (NCF2), p40phox (NCF4), p22phox (CYBA), gp91phox (CYBB), DUOX1, DUOX2, TLR2, TLR9 and alpha 1-antitrypsin (AAT) in a cohort of 95 lung disease individuals and 95 control individuals did not show an association of these polymorphisms with increased susceptibility to lung disease.

Interferon-gamma gene (T874A and G2109A) polymorphisms are associated with microscopy-positive tuberculosis

Genetic susceptibility to tuberculosis includes several unknown yet different loci each contributing to a small extent. Intronic polymorphisms within the interferon-gamma (IFN-gamma) gene IFNG T+874A and IFNG G+2109A correlate with the IFN-gamma production in vitro, and the frequency of potential high IFN-gamma producers was previously reported by others to be lower in patients than in controls from Sicily. The aim of this study was to determine whether there is an association between polymorphisms in the IFN-gamma gene and predisposition to tuberculosis. We analysed two IFNG SNPs (T+874A and G+2109A) in patients (n = 253) hospitalized in Rijeka (Croatia) and controls (n = 519) from the same area. One-fifth of the controls were healthy contacts of the diseased, and the rest were blood donors. IFNG alleles, their predicted haplotypes or genotypes were not associated with disease susceptibility. Thus, we could not reproduce results from Sicilian case-control study. However, T/T+874 (possible high IFN-gamma producer) and +874A/A (putative low producer) genotypes were associated with microscopically positive-negative forms of disease. Haplotypes (T+874A and G+2109A) based on a prediction by software phase and subsequent genotype analysis corroborated these findings. Patients had significantly higher frequency of genotypes without T at +874 (AA/AA; AA/AG and AG/AG) in microscopy- or bacterial culture-positive groups compared with their negative counterparts. These data suggest an association with disease severity rather than susceptibility to tuberculosis in Croatian Caucasian population.

Impairment of IFN-alpha production capacity in patients with hepatitis C virus and the risk of the development of hepatocellular carcinoma

AIM

To determine the utility of interferon (IFN)-alpha production capacity in patients with hepatitis C virus (HCV) infection for the measurement of immuno-surveillance potential and for the early detection of hepatocellular carcinoma (HCC) by investigating the Sendai virus (HVJ) stimulated IFN-alpha production capacity of patients with HCV infection.

METHODS

HVJ stimulated IFN-alpha production was determined in a large number of patients with HCV infection and the development of HCC was monitored for 3 years in patients with liver cirrhosis (LC).

RESULTS

IFN-alpha production capacity decreases gradually with the progression of liver disease from chronic hepatitis (CH) to HCC. A significant correlation between the duration of HCV infection and impaired IFN-alpha production capacity was observed. IFN-alpha production in patients who developed HCC within 3 years was significantly lower than that of patients who remained in LC without developing HCC.

CONCLUSION

Measurement of IFN-alpha production in LC patients may be useful for the early detection of HCC.

Interferon-gamma receptor-1 gene promoter polymorphisms (G-611A; T-56C) and susceptibility to tuberculosis

We analysed frequencies of two single-nucleotide polymorphisms (SNP) in the interferon-gamma (IFN-gamma) receptor-1 (IFNGR1) gene promoter (G-611A, T-56C) in tuberculosis patients (n = 244) and compared them with controls (n = 521). These frequencies were not significantly different, whether analysed independently or as haplotypes. Because these SNP affect transcription, the results suggest that the expression of the IFNGR1 gene does not confer susceptibility to disease in patients from Croatia. Further analysis revealed a significant association between the protective (CA)(n) polymorphism (22 repeats, 192 FA(1)), located in the fifth intron of the IFNGR1 gene (+16682), and GT promoter haplotype (-611; -56) that showed the strongest expression capacity. In addition to this cis relationship, the (CA)(22) allele was correlated in trans with an IFN-gamma SNP (IFNG G + 2109A), which might affect the transcription of the IFNG gene. These results suggest that a particular combination of IFNG and IFNGR1 SNP might offer a better protection against tuberculosis in this population.

Association between SLC11A1 (formerly NRAMP1) and the risk of sarcoidosis in Poland

Sarcoidosis (SA) is a systemic granulomatous disorder of unknown etiology characterized by T helper 1-type inflammatory responses at sites of disease with signs of B cell hyperactivity. Like rheumatoid arthritis and diabetes, an infectious etiology has frequently been postulated but no single infectious trigger definitively identified. Polymorphic alleles at SLC11A1 have previously been associated with susceptibility to both the putative infectious agents and to these autoimmune disorders. We therefore investigated its candidacy as a genetic determinant of SA in Poland in an association-based study comparing 86 SA patients with 85 tuberculosis (TB) patients and 93 control subjects. The functional promoter (GT)(n) polymorphism and four of 10 other single nucleotide or insertion/deletion polymorphisms genotyped across SLC11A1 were informative in our sample. Consistent with previous autoimmune disease studies, allele 3 at the functional (GT)(n) promoter region repeat polymorphism was significantly associated with SA when compared with healthy controls (odds ratio 1.68; 95% CI: 1.01-2.81; P=0.04) or with TB patients (odds ratio 1.69; 95% CI: 1.042-0.78; P=0.03).

Polymorphism of the 5' flanking region of the IL-12 receptor beta2 gene partially determines the clinical types of leprosy through impaired transcriptional activity

BACKGROUND

Individual differences in T cell responsiveness to interleukin 12 (IL-12), resulting from inherited factors, may be responsible for differences in the intensity of cell mediated immune (CMI) responses in patients with leprosy, a disease with a wide clinical spectrum.

AIM

Polymorphisms in the 5' flanking region of the IL12RB2 gene were analysed to determine potential immunogenetic factors affecting CMI responses, using leprosy as a model.

METHODS

Polymorphisms in the 5' flanking region of IL12RB2 were examined using direct sequencing techniques, and allele frequencies between patients with lepromatous leprosy and patients with tuberculoid leprosy were compared. The effect of these single nucleotide polymorphisms (SNPs) on IL12RB2 expression was estimated using the dual luciferase reporter gene assay in Jurkat T cells.

RESULTS

Several SNPs, including -1035A>G, -1023A>G, -650delG, and -465A>G, were detected within the 5' flanking region of IL12RB2. The frequency of haplotype 1 (-1035A, -1023A, -650G, -464A) was high in the general Japanese population, but was significantly lower in lepromatous patients compared with tuberculoid patients and healthy controls. Reporter gene assays using Jurkat T cells revealed that all haplotypes carrying one or more SNP exhibited a lower transcriptional activity compared with haplotype 1.

CONCLUSION

SNPs within the 5' flanking region of IL12RB2 affect the degree of expression of this gene and may be implicated in individual differences in CMI responsiveness to mycobacterial antigens, leading to lepromatous or tuberculoid leprosy.

Association between IFNA genotype and the risk of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by multisystem inflammation and production of autoantibodies, which can generate immune complexes and may cause tissue damage through the recognition of an autoantigen. Although many factors have been proposed, such as genetic factors, environmental factors, hormonal action, viruses, and dysregulation of cytokine production, the cause of this disease is not well understood. It has been reported that the levels of interferon (IFN)-alpha in the sera of some SLE patients are elevated and that IFN-alpha induces maturation of monocytes into highly active antigen-presenting dendritic cells (DCs). We analyzed the association between IFN-alpha genotype and the risk of SLE to clarify whether IFN-alpha plays a central role in susceptibility to SLE. The results showed that no IFN-alpha genotype was significantly associated with the risk of SLE.