Analysis of an IFN-gamma gene (IFNG) polymorphism in multiple sclerosis in Europe: effect of population structure on association with disease

Cell Intrinsic Factors Modulate the Effects of IFNγ on the Development of Chlamydia trachomatis

Chlamydia trachomatis is an obligate intracellular bacterial pathogen that cannot synthesize several amino acids, including tryptophan. Rather, C. trachomatis acquires these essential metabolites from its human host cell. Chlamydial dependence on host-provided tryptophan underlies a major host defense mechanism against the bacterium; namely, the induction of the host tryptophan-catabolizing enzyme, indoleamine 2,3- dioxygenase (IDO1) by interferon gamma (IFNγ), which leads to eradication of C. trachomatis by tryptophan starvation. For this reason, IFNγ is proposed to be the major host protective cytokine against genital C. trachomatis infections. The protective effect of IFNγ against C. trachomatis can be recapitulated in vitro using epithelial cell-lines such as the cervical carcinoma derived cell-line Hela, the Hela subclone HEp-2, and the cervical carcinoma derived cell-line ME180. Addition of IFNγ to these cells infected with C. trachomatis results in a strong bactericidal or bacteriostatic effect dependent on the concentration of IFNγ administered. Unlike Hela, HEp-2, and ME180, there are other human epithelial, or epithelial-like cell-lines where administration of IFNγ does not affect chlamydial replication, although they express the IFNγ receptor (IFNGR). In this report, we have characterized the mechanisms that underlie this dichotomy using the cell-lines C33A and 293. Akin to Hela, C33A is derived from a human cervical carcinoma, while 293 cells were produced by transfection of adenovirus type 5 DNA into embryonic kidney cells. We demonstrate that although IFNGR is expressed at high levels in C33A cells, its ligation by IFNγ does not result in STAT1 phosphorylation, an essential step for activation of the IDO1 promoter. Our results indicate that although the IFNγ-dependent signaling cascade is intact in 293 cells; the IDO1 promoter is not activated in these cells because it is epigenetically silenced, most likely by DNA methylation. Because polymorphisms in IFNγ, IFNGR, and the IDO1 promoter are known to affect other human infections or diseased states, our results indicate that the effect of allelic differences in these genes and the pathways they activate should be evaluated for their effect on C. trachomatis pathology.

No evidence for genetic linkage between development of multiple sclerosis and components of the IFN system and the JA K-STAT pathway

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system (CNS). Several observations suggest that the interferon system may be of interest in the study of MS development. To investigate whether polymorphism in components of the IFN system and the JA K-STAT pathway influence susceptibility to MS, we performed a linkage analysis between polymorphic loci in or close to the IFN gamma, IFN gamma recepto r, IFN alpha/beta recepto r, JA K 1, STAT 1 and STAT 3 genes in 27 Swedish families with at least two members having MS. Tests for transmission disequilibrium and nonparametric linkage analysis gave negative results. We found no evidence for linkage between MS and any of these loci.

Multiple sclerosis: the role of cytokines in pathogenesis and in therapies

Multiple sclerosis, the clinical features and pathological correlate for which were first described by Charcot, is a chronic neuroinflammatory disease with unknown etiology and variable clinical evolution. Although neuroinflammation is a descriptive denominator in multiple sclerosis based on histopathological observations, namely the penetration of leukocytes into the central nervous system, the clinical symptoms of relapses, remissions and progressive paralysis are the result of losses of myelin and neurons. In the absence of etiological factors as targets for prevention and therapy, the definition of molecular mechanisms that form the basis of inflammation, demyelination and toxicity for neurons have led to a number of treatments that slow down disease progression in specific patient cohorts, but that do not cure the disease. Current therapies are directed to block the immune processes, both innate and adaptive, that are associated with multiple sclerosis. In this review, we analyze the role of cytokines in the multiple sclerosis pathogenesis and current/future use of them in treatments of multiple sclerosis.

Polymorphisms of innate pattern recognition receptors, response to interferon-beta and development of neutralizing antibodies in multiple sclerosis patients

BACKGROUND

Interferon-beta therapy of patients with relapsing-remitting multiple sclerosis involves repeated 'immunizations' with exogenous protein solutions. Innate pattern recognition receptors play an important role in immune responses towards foreign substances and may thus be related to treatment outcome.

OBJECTIVE

To determine the genotypes at 42 single nucleotide polymorphism loci in selected pattern recognition receptors for 567 prospectively followed relapsing-remitting multiple sclerosis patients treated with recombinant interferon-beta, and test for relationships to several outcome parameters, including formation of interferon-beta neutralizing antibodies.

RESULTS

The results suggest an association between the rs5743810 polymorphism (Ser249Pro) of TLR6 and development of neutralizing antibodies after 24 months of therapy in males (p = 0.00002), but not in females (p = 0.2). This association survived crude Bonferroni correction (p (corrected) = 0.02). Additional associations were observed in carriers of the TLR2-rs5743708 and NOD2-rs3135499 SNPs (time to relapse), the TLR7-rs179008 and NOD1-rs2075820 SNPs (time to disease progression) and the TLR4-rs7873784, TLR9-rs5743836, and NOD2-rs2066842 SNPs (frequency of neutralizing antibodies development). All of these, however, failed to survive correction for multiple testing. There were no significant differences between interferon-beta responders and non-responders for any of the investigated single nucleotide polymorphisms.

CONCLUSIONS

The rs5743810 polymorphism of TLR6 may be involved in development of anti-interferon-beta antibodies in males, although further studies are required to firmly establish this.

Polymorphism in intron 1 of the interferon-gamma gene influences both serum immunoglobulin E levels and the risk for chronic hepatitis B virus infection in Polynesians

Intron 1 of the interferon-gamma (IFNG) gene contains two polymorphisms. The 12 CA-repeat allele of the +875 IFNGCA microsatellite and the T allele of the +A874T single nucleotide polymorphism (SNP) have been associated with increased in vitro IFNG production and a variety of clinical phenotypes. The purpose of this study was to determine whether these polymorphisms influence total serum IgE levels [tsIgE] and the outcome of a hepatitis B virus (HBV) infection. IFNGCA and +A874T were typed in 186 asthmatics of Niuean ancestry and in Polynesian women with a chronic HBV infection (n = 60) and with natural immunity to the HBV (n = 66). The IFNGCA genotype was associated with [tsIgE] in asthmatic children (n = 51, p = 0.004) but not adults (n = 135, p = 0.87). The data were consistent with a co-dominant influence of the 12 CA-repeat allele on high [tsIgE]. The IFNGCA genotype was also associated with the risk for chronic HBV infection (chi (2) = 11.6, p = 0.003) because of a dominant effect of the 12 CA-repeat allele on developing natural immunity in homozygotes (OR = 5.8, p = 0.003) and heterozygotes (OR = 2.7, p = 0.01). Similar associations were found for the T allele of the +A874T SNP. The possibility that these associations were due to linked alleles in the adjacent 783 bp of the promoter and 3'-untranslated region of the IFNG gene was excluded by direct sequencing. In summary, high-IFNG-producing alleles in intron 1 of the IFNG locus are associated with high [tsIgE] in asthmatic children from Niue and with natural immunity to the HBV in Polynesian women. These findings are consistent with a previous report of an association between +875 IFNGCA and [tsIgE] and provide preliminary evidence of a new association with the outcome of an HBV infection.

Epidemiology and natural history of multiple sclerosis: new insights

PURPOSE OF REVIEW

The cause of multiple sclerosis remains elusive. We review recent epidemiological studies of genetic and environmental factors that influence susceptibility to the disease and its clinical course.

RECENT FINDINGS

Genetic advances strengthen the association of multiple sclerosis with the human leukocyte antigen (HLA)-DRB1 allele and interferon-gamma polymorphisms and suggest that apolipoprotein E alleles play an important role. In the environmental realm, nested case-control studies show that prior Epstein-Barr virus exposure is overrepresented in multiple sclerosis. Smoking has been associated with both risk of multiple sclerosis and progressive disease. Vitamin D deficiency might tie together environmental clues with higher multiple sclerosis prevalence rates; dietary vitamin supplementation is also associated with reduced multiple sclerosis risk. Natural history studies demonstrated dissociation between relapses and disease progression, facilitated the ability to distinguish neuromyelitis optica and related syndromes from typical multiple sclerosis, and spawned the exploration of large datasets to model long-term disease activity.

SUMMARY

Our understanding of the contributions of specific genetic and environmental factors that contribute to multiple sclerosis has improved. Further refinements will eventually allow powerful longitudinal studies to assess genetic and environmental interactions with implications for prediction of individual disease susceptibility, clinical course, and response to therapy.

Interleukin-22 and its crystal structure

Interleukin-22 (IL-22) is a cytokine that regulates the production of acute phase proteins of the immunological response. On binding to its cognate receptor (IL-22R1), which is associated to the interleukin-10 receptor 2 (IL-10R2), IL-22 promotes activation of signal transducer and activator of transcription (STAT) pathway and several other cellular responses. A soluble receptor termed interleukin-22 binding protein (IL-22BP) is also able to bind to IL-22 as a natural protein antagonist, and probably provides systemic regulation of IL-22 activity. This inflammatory response system is analyzed here in terms of its molecular physiology and structural assembly. Three-dimensional (3D) model of IL-22 and structural basis of its interactions with the cognate receptors are discussed.

Genetic polymorphism of the interferon-gamma gene in cervical carcinogenesis

Beyond human papillomavirus (HPV) infection, host genetic factors may contribute to cervical carcinogenesis. This study aims to test the hypothesis that CA-dinucleotide repeat polymorphism in the first intron of the interferon-gamma (IFN-gamma) gene is associated with HPV-initiated cervical carcinogenesis. A hospital-based case-control study including patients with low-grade squamous intraepithelial lesions (LSILs; n = 93), high-grade squamous intraepithelial lesions (HSILs; n = 123) and invasive carcinomas (n = 153) of the uterine cervix, as well as 1:1 age-matched controls, was conducted. The IFN-gamma genotype was determined by PCR and capillary electrophoresis with internal standards. HPV genotype was determined by consensus PCR and reverse line blot hybridization. Genotypes containing the 12 or 14 allele (12 or 14 CA repeats) were significantly more common in patients with HSILs than in controls (46% vs. 22%; OR = 3.0; 95% CI = 1.7-5.2; p < 0.0001). In contrast, genotypes containing 13 and 18 were significantly more common in controls than in patients with HSILs (76% vs. 53%; OR = 0.3; 95% CI = 0.2-0.6; p = 0.0001) or squamous cell carcinomas (74% vs. 63%; OR = 0.6; 95% CI = 0.4-1.0; p = 0.037). The frequency of the 12 and 14 genotypes increased significantly in accordance with the severity of cervical carcinogenesis (p(test for trend) = 0.0002), whereas the 13 and 18 genotypes showed the opposite trend (p(test for trend) = 0.007). Comparing IFN-gamma genotype and HPV status, 18-containing genotypes were more frequently found in HPV(+) LSILs, and 12-containing genotypes were less frequently found in HPV(+) HSILs. Compared with non-13 genotypes, 13 genotype HSILs were more frequently infected with HPV58 (70% vs. 45%) and less frequently infected with HPV18 (0% vs. 16%; p= 0.007). Genetic polymorphism of the IFN-gamma gene is associated with individual susceptibility to cervical carcinogenesis. This polymorphism correlates with HPV infection in a disease- and type-specific manner.

IFNG polymorphisms are associated with gender differences in susceptibility to multiple sclerosis

Interferon-gamma (IFNgamma) treatment is deleterious in multiple sclerosis (MS). MS occurs twice as frequently in women as in men. IFNgamma expression varies by gender. We studied a population-based sample of US MS patients and ethnicity-matched controls and independent Northern Irish and Belgian hospital-based patients and controls for association with MS, stratified by gender, of an intron 1 microsatellite [I1(761)*CAn], a single nucleotide polymorphism 3' of IFNG [3'(325)*G --> A] and three flanking microsatellite markers spanning a 118 kb region around IFNG. Men carriers of the 3'(325)*A allele have increased susceptibility to MS compared to noncarriers in the USA (P=0.044; OR: 2.58, 95% CI: 0.97-8.08) and Northern Ireland (P=0.019; OR: 2.37, 95% CI: 1.10-5.13). There is a nonsignificant trend in the same direction in Belgian men (P=0.299; OR: 1.50, 95% CI: 0.71-3.26). Men carriers of I1(761)*CA13, which is in strong linkage disequilibrium with the 3'(325)*A, have increased susceptibility (P=0.050; OR: 2.22, 95% CI: 0.98-5.40), while men carriers of I1(761)*CA12 have decreased susceptibility (P=0.022; OR: 0.46, 95% CI: 0.23-0.90) to MS in the USA. Similar associations were reported in Sardinia between the I1(761)*CA12 allele and reduced risk of MS in men. Flanking markers were not associated with MS susceptibility. Polymorphisms of IFNG may contribute to differences in susceptibility to MS between men and women.

Interleukin-10 and interleukin-6 gene polymorphisms as risk factors for Alzheimer’s disease

In the pathogenesis of Alzheimer disease (AD), it has been proposed that the anti-inflammatory interleukins such as IL-10 regulate beta-amyloid-induced microglial inflammatory responses inhibiting the proinflammatory cytokine IL-6. Since the promoters of the IL-10 and IL-6 genes show single nucleotide polymorphisms (SNPs) (IL-10: -1082 G --> A; IL-6: -174 G --> C), we investigated these SNPs and cytokine production by peripheral blood mononuclear cells in 65 AD patients and 65 controls (HC). In AD there was a significant increase of the -1082A IL-10 allele (P=0.009) and a decrease of -1082GG genotype (P=0.019). The frequency of the GG IL-6 genotype in AD was lower and the C allele significantly higher (P <0.005). The co-occurrence of IL-10 A and IL-6 C alleles significantly raised the odds ratio (OR 11.2, confidence interval: CI 1.3-97.3; P <0.05) independently of apolipoprotein E4 (adjusted OR 10.3, CI 1-108; P <0.05). Only amyloid-stimulated IL-10 production differed between the groups (P=0.023). These results raise questions regarding the inflammatory theory in AD, pointing to a pivotal role of IL-10 and IL-6 and a selective alteration in this network.

The interferon gamma gene in celiac disease: augmented expression correlates with tissue damage but no evidence for genetic susceptibility

Celiac disease (CD) is a complex genetic disorder characterized by gluten intolerance. The Th1 immune response, with a key position for interferon gamma (IFN-gamma), is an important determinant of intestinal remodeling in CD. We aimed at further ascertaining the role of IFN-gamma, either as a genetic factor in the etiology, or as a facilitator of disease initiation/progression. Duodenal biopsies were sampled across distinct histopathological stages of the disease, including refractory CD (RCD), and used to determine IFN-gamma gene (IFNG) expression by real-time RT-PCR. INFG expression correlated with the extent of tissue restructuring, reaching a 240-fold higher expression in total villous atrophy compared to healthy tissue. CD and RCD patients with similar lesions had comparable expression levels. Interestingly, patients in complete remission still had 7.6-fold residual over-expression. An INFG marker was tested in three cohorts of Dutch patients for both genetic linkage and association. Linkage analysis yielded no significant scores for IFNG or its flanking markers. In addition, IFNG allele frequencies were not differently distributed between cases and controls. Likewise, all alleles were randomly transmitted to affected children in parents-case trios. There is no evidence for IFNG as a predisposing gene in CD, despite its enhanced expression in patients in complete remission.

Polymorphisms in the genes encoding interferon-gamma and interferon-gamma receptors in multiple sclerosis

Genome screens suggest that several genes, each contributing to a small extent, are involved in multiple sclerosis (MS) susceptibility. Simultaneous analysis of related genes may improve the power to detect such small effects. Interferon-gamma (IFN-gamma), mediating its effects through the IFN-gamma receptor, is a pleiotropic, pro-inflammatory cytokine for which a detrimental effect on the course of MS has been reported. The role of IFN-gamma receptor 1 (IFNGR1) and IFN-gamma receptor 2 (IFNGR2) gene polymorphisms has not been studied in MS, and, for the IFNG gene polymorphism there is only one previous study, which incorporates clinical, but not imaging, data. The aim of this study was to investigate whether polymorphisms in the IFNG and IFNGR1 and IFNGR2 genes are associated with susceptibility to MS, or disease characteristics, as defined by clinical and imaging criteria. Genotypes for IFNG, IFNGR1 and IFNGR2 were determined in 509 patients with MS and in 193 healthy controls. Patient files were reviewed for disease course, age at onset of disease, and rate of progression. Serial magnetic resonance imaging (MRI) data were available for 107 patients. No significant differences in the distribution of IFNG, IFNGR1 and IFNGR2 genotype and allele frequencies were found between patients and controls. A progressive, as opposed to a relapsing, onset was significantly more frequent in carriers of the IFNGR2 allele Arg64 (P = 0.028). Moreover, IFNGR2 allele Arg64 carriers had a lower black hole ratio than non-carriers (P = 0.016). No other associations with clinical parameters, such as age at onset or rate of progression, or with imaging parameters, were observed. The IFNG intron 1 gene polymorphism studied is unlikely to play a major role in MS susceptibility or disease course. The IFNGR1 and IFNGR2 gene polymorphisms studied do not exert an important influence on MS susceptibility, but allele IFNGR2*Arg64 may be associated with a progressive disease onset.

A polymorphism of interferon-gamma gene associated with changes of anti-thyrotropin receptor antibodies induced by antithyroid drug treatment for Graves' disease in Japanese patients

Graves' disease (GD) is an autoimmune disorder with genetic predisposition. Interferon-gamma (IFN-gamma) is an important mediator of inflammatory and immune responses. The aim of the present study was to investigate whether the polymorphism of IFN-gamma gene is associated with the development of GD or with clinical course during the antithyroid drug therapy. We have studied the CA repeat polymorphisms in the first intron of IFN gamma gene in Japanese patients with GD (n = 162) and healthy control subjects without antithyroid autoantibodies or family history of autoimmune disorders (n = 133). There was no difference in allele frequency of IFN-gamma gene polymorphism between patients with GD and control subjects. However, the allele 4 (15 CA repeats) frequency was significantly greater in patients whose antithyrotropin receptor antibody (TRAb) became negative within 3 years by antithyroid drug treatment than those with consistently positive TRAb for more than 3 years (34.1% vs. 15.7%, chi2 = 8.545, p = 0.0035, pc = 0.049). The in vitro production of IFN-gamma by concanavalin A-stimulated peripheral blood mononuclear cells was significantly smaller in control subjects with the allele 4 compared to those with the other alleles. In conclusions, the CA repeat polymorphism of the IFN-gamma gene might be associated with the outcome of anti-thyroid drug treatment.

Polymorphisms in the interferon-γ/interleukin-26 gene region contribute to sex bias in susceptibility to rheumatoid arthritis

OBJECTIVE

To determine whether polymorphisms in the interferon-gamma (IFNgamma)/interleukin-26 (IL-26; formerly, AK155) gene cluster contribute to sex-based differential susceptibility to rheumatoid arthritis (RA).

METHODS

Four microsatellite markers, located in a 118-kb interval that contains both the IFNgamma and IL-26 genes on chromosome 12q15, were typed in 251 patients with RA and 198 unrelated healthy controls (all of whom lived in Northern Ireland) by means of polymerase chain reaction-based fragment analysis.

RESULTS

Marker D12S2510, which is located 3 kb 3' from the IL-26 gene, was significantly associated with RA in women (corrected P [P(corr)] = 0.008, 2 degrees of freedom [2 df]) but not in men (P = 0.99, 2 df). A 3-marker haplotype, IFNGCA*13;D12S2510*8;D12S2511*9, was inferred that showed significant underrepresentation in women with RA (odds ratio 0.50, 95% confidence interval 0.32-0.78; P = 0.002, P(corr) = 0.03) but not in men with RA.

CONCLUSION

Our results demonstrate that common polymorphisms in the IFNgamma/IL-26 gene region may contribute to sex bias in susceptibility to RA, by distorting the propensity of female carriers versus male carriers to contract this disease. These results conform to our recent observations of a role for this gene cluster in sex-based differential susceptibility to another Th1-type inflammatory disease, multiple sclerosis.

A genome-wide screen for linkage disequilibrium in Australian HLA-DRB1*1501 positive multiple sclerosis patients

The association of multiple sclerosis with alleles/haplotypes from the HLA region on chromosome 6p21 is well established although the remainder of the genome remains relatively unexplored. We have completed a genome-wide screen for linkage disequilibrium in a cohort of Australian multiple sclerosis patients positive for HLA-DRB1*1501. A total of 4346 microsatellite markers provided through the "Genetic Analysis of Multiple sclerosis in EuropeanS" (GAMES) collaborative were analysed in DNA separately pooled from cases (n=217) and controls (n=187). Associations were found in four genomic regions (12q15, 16p13, 18p11 and 19q13) previously identified in linkage genome screens. Three additional regions of novel association were also identified (11q12, 11q23 and 14q21). Further analysis of these regions is required to establish whether the associations observed are due to epistatic interaction with the HLA locus.

Genetic analysis of multiple sclerosis

Multiple sclerosis (MS) is a complex disease with a significant genetic contribution. Similar to other complex diseases, the genetic risk for MS results from a combination of many genetic variants which individually confer only modest effects. Here we review the results of the complementary genetic approaches of linkage and association in MS, highlighting the challenges of identifying loci of modest effect. We describe meta-analytical approaches that provide additional statistical power necessary for detecting such loci and further apply this approach to evaluate the association of a CTLA-4 variant with MS. Lastly, we review recent important advances in our understanding of the patterns of genetic variation in the human genome and speculate about how these advances will aid in future studies of the genetic causes of MS.

Cytokine gene polymorphisms in multifactorial diseases: gateways to novel targets for immunotherapy?

Recent advances in cytokine biology have led to novel approaches to the treatment of inflammatory diseases. In this article, we review recent data regarding the role of functional polymorphisms in the genes encoding the prototypic Th1 cytokine interferon gamma and Th2 cytokine interleukin 4 in multifactorial disorders. We have compared genetic data across a heterogeneous assortment of such conditions using a 'haplotype tagging' approach, and demonstrate that cytokine gene association studies are instrumental in the identification of specific disease states or clinical manifestations that are probably caused by genetically determined aberrant cytokine expression. Some of these new findings suggest cytokine effects that go beyond a classical Th1-Th2 dichotomy. Thus, we propose that this information could provide novel targets for immunotherapy and, in particular, might facilitate the identification of clinical subgroups of patients who, by virtue of their genetic constitution at these cytokine gene loci, are more likely to benefit from cytokine agonist or antagonist therapy.

Linkage disequilibrium analysis of chromosome 12q14-15 in multiple sclerosis: delineation of a 118-kb interval around interferon-gamma (IFNG) that is involved in male versus female differential susceptibility

We have recently reported the association of a polymorphic intronic CA-repeat in the interferon-gamma gene (IFNG) with gender bias in susceptibility to multiple sclerosis (MS) in a Sardinian population. This association could refer to a functional polymorphism within IFNG or could be due to linkage disequilibrium between the IFNG marker and a neighbouring susceptibility locus. Within the average reach of linkage disequilibrium, various other candidate genes are located. Among these the most striking ones are the genes coding for the cytokines interleukin-22 (IL-22) and interleukin-26 (IL-26) that constitute together with IFNG a cytokine cluster on chromosome 12q14. To determine more precisely the location of this gender-associated susceptibility locus, we have now performed a more extensive linkage disequilibrium screen of this region using nine additional microsatellite markers. This locus appeared to be confined to a 118-kb interval that is bordered by the markers D12S313 and D12S2511, in which IFNG itself remains the main candidate gene. Haplotype analysis confirmed that this MS-associated locus protects males from developing MS according to a recessive or allele-dosage model. Our results indicate that the well-documented gender differences in susceptibility to MS are at least partially caused by genetic factors in the region surrounding IFNG.

The -174 G/C polymorphism of the interleukin-6 gene promoter is associated with Alzheimer's disease in an Italian population [corrected]

Interleukin-6 (IL-6) is a multifunctional cytokine playing a crucial role in inflammation and tissue injury. A role for this molecule in neurodegeneration and Alzheimer's disease (AD) has been proposed. The aim of this study was to evaluate the association between a common polymorphism of the IL-6 gene promoter and AD in the Italian population. We found that the frequency of the GG genotype was significantly higher in AD patients than controls on both univariate ( rho< 0.0001) and multivariate analysis ( rho< 0.0001). In contrast, the CC genotype seems to be associated with a reduced risk of disease ( rho< 0.0001). Our data indicate that the IL-6 gene polymorphism is associated with AD in Italians and confirm that IL-6 is crucial in the pathophysiology of neurodegenerative disorders.

Multiple sclerosis in the tropics: genetic association to STR's loci spanning the HLA and TNF

Clear evidence has been presented correlating gene polymorphisms at 6p21.3-21.4 (containing HLA and TNF) and the predisposition to acquire multiple sclerosis (MS). In a previous study, we found that polymorphisms at HLA DQAI were associated with being or not being predisposed to MS in individuals inhabiting the tropics, where the prevalence of MS is significantly lower than in subtropical areas. Here, we tested the hypothesis that polymorphisms at D6S276, D6S265, D6S273 and D6S291 microsatellite loci are in strong linkage disequilibrium with a major genetic factor predisposing to MS. These microsatellites span the 6p21.3 region with intervals of 5 cM establishing particular landmarks for the HLA and TNF loci. Thirty-five MS patients and 35 controls, age, sex, social, ethnically and geographically matched healthy individuals, were studied. After testing the fit of gene frequencies to the normal distribution and performing the correlation for multiple comparisons, we found significant differences among the case and the control frequencies for the allele 202 belonging to the marker D6S276 (Pc=0.00455) and for the allele 114 belonging to the marker D6S265 (Pc=0.0084). For these two alleles at different loci, we found higher frequencies in the cases than in the controls. A nonsignificant p value was found in testing the existence of linkage disequilibrium among the studied loci in the cases and in the controls. In conclusion, the current study adds evidence to the established association among polymorphisms of genes located at 6p21.3-21.4 and MS. Furthermore, because of the distribution of the tested microsatellite loci, the more probable critical region could be correlated with the TNF neighborhood.

Polymorphisms of interferon-gamma gene CA-repeat and interleukin-10 promoter region (-592A/C) in Japanese type I diabetes

We investigated the association of the polymorphisms of interferon-gamma gene (IFNG) CA-repeat and IL-10-592A/C with clinical heterogeneity of type I diabetes as well as susceptibility to type I diabetes. Two hundred seven Japanese type I diabetic patients and 160 healthy control subjects were studied in this case-control study. No significant differences of global IFNG allele frequencies were found between controls and type I diabetic patients, and between each subgroup of the patients and controls. When compared with controls, the a12 allele was increased in the patients with age at onset <25 years (p 0.0241, p(c) = 0.1205), and a significant increased frequency of the a12 positive genotype was observed in the patients with age at onset <25 years (p(c) = 0.0121). There were no differences of IL-10-592 genotype and allele frequencies between controls and type I diabetes. However, the frequency of the -592*C allele was significantly increased in the patients with highly positive-GADab compared with controls (p(c) = 0.0060) or compared with the GADab-negative type I patients (p(c) = 0.0276). These results suggest that the IFNG CA-repeat and the IL-10-592A/C polymorphisms are not strong determinants of susceptibility to the development of type I diabetes in Japanese individuals. However, both the IFNG CA-repeat and the IL-10-592A/C polymorphisms are associated with clinical heterogeneity in type I diabetes.

Identifying disease modifying genes in multiple sclerosis

Evidence is mounting that genetic variation influences not only susceptibility to multiple sclerosis (MS), but also its course and severity. Identification of disease modifying genes, however, poses unique challenges, especially on how to classify the course and outcome of the disease in ways that may be relevant to analysis of biological factors that might be influenced by genes. The power of the statistical approaches to detect small effects of individual genes in complex disorders such as MS is problematic, and approaches to estimate power must be appropriate for the data. Nonetheless, using contemporary schemes of classification, genetic variants that influence disease course have been found; in fact, a small number have been confirmed to influence disease course in two or more independent studies. This review addresses strategies relevant to identification of disease modifying genes in MS, and summarizes and critically evaluates the current state of knowledge in this area.

Allele frequencies of +874T-->A single nucleotide polymorphism at the first intron of interferon-gamma gene in a group of Italian centenarians

Ageing is characterized by a pro-inflammatory status which could contribute to the onset of major age-related diseases such as cardiovascular diseases, neurodegeneration, osteoarthritis and osteoporosis, and diabetes. Thus, it can be hypothesized that genetic variations in pro- or anti-inflammatory cytokines might influence successful ageing and longevity. We have studied the distribution of +874T-->A interferon-gamma (IFN-gamma) polymorphisms in a large number of Italian centenarians to evaluate if the two alleles might be differently represented in people selected for longevity. DNA samples were obtained from 174 Italian centenarians (>99 years old, 142 women and 32 men) and from 248 <60-year-old control subjects (90 women and 158 men) matched for geographical distribution. Polymorphisms at +874 were identified by using amplification refractory mutational system methodology. The +874T allele was found less frequently in centenarian women than in centenarian men or in control women whereas no significant differences were observed in the distribution of the two alleles between male or female controls. Allele frequencies in centenarian men were not found significantly different from male controls. Possession of the +874A allele, known to be associated with low IFN-gamma production, significantly increases the possibility to achieve extended longevity, suggesting that the pro-inflammatory status characteristic of ageing may be detrimental for successful ageing. The datum that the allele was significantly increased in female but not male centenarians seems to strengthen the idea that gender may be a major variable in the biology of the ageing process. However, the present data add another piece of evidence to the complex puzzle of genetic and environmental factors involved in controlling life span expectancy in humans. Thus, studies on cytokine gene polymorphisms may promise to individuate a complex network of trans-interactive genes able to influence the type and strength of responses to environmental stressors and as a final result, thereby conditioning individual life expectancy.

Novel polymorphisms in the IL-10 related AK155 gene (chromosome 12q15)

AK155 is a recently discovered cytokine distantly related to IL-10. Its gene is located on chromosome 12q15, a region that is likely to harbour susceptibility genes for autoimmune and allergic diseases. We provide here identification and characterization of two microsatellite polymorphisms at the AK155 locus, i.e. D12S2511 and D12S2510. The first is located in the third intron and the second in the 3' region of the gene. Both might be useful as markers in association or linkage studies of polygenic inflammatory or allergic diseases. No association with multiple sclerosis was found for each of these markers by means of the transmission disequilibrium test in an extended number of Sardinian simplex families.

Analysis of an interferon-gamma gene dinucleotide-repeat polymorphism in Nordic multiple sclerosis patients

The proinflammatory cytokine interferon (IFN)-gamma has been shown to influence the course of multiple sclerosis (MS). The IFN-gamma (IFNG) contains a multiallelic dinucleotide repeat in intron 1. To investigate whether alleles at this locus influence susceptibility to MS, we performed linkage and familial association analyses on 100 sibling pairs from four Nordic countries, and case-control association analysis on 220 intermediately disabled sporadic MS patients and 266 controls. To determine the effect of the polymorphism on disease outcome, we compared genotype frequencies in the most and least disabled octiles of a total cohort of 913 cases. We also measured IFN-gamma mRNA levels in unstimulated peripheral blood mononuclear cells from 46 MS patients and 27 controls grouped according to IFNG intron 1 genotype. Both nonparametric linkage analysis and transmission disequilibrium testing of the 100 sibling pairs produced negative results. Genotype frequencies for intermediate-MS patients did not differ significantly from those for controls; nor did genotype frequencies in the benign-MS octile differ significantly from those in the severe-MS octle. Comparison of IFN-gamma mRNA levels in genotype-conditioned subgroups revealed no significant differences. Thus, alleles at the IFNG intron 1 dinucleotide repeat appear to affect neither MS susceptibility and severity nor IFN-gamma mRNA expression in vivo.

Induction of a non-encephalitogenic type 2 T helper-cell autoimmune response in multiple sclerosis after administration of an altered peptide ligand in a placebo-controlled, randomized phase II trial. The Altered Peptide Ligand in Relapsing MS Study Group

In this 'double-blind', randomized, placebo-controlled phase II trial, we compared an altered peptide ligand of myelin basic protein with placebo, evaluating their safety and influence on magnetic resonance imaging in relapsing-remitting multiple sclerosis. A safety board suspended the trial because of hypersensitivity reactions in 9% of the patients. There were no increases in either clinical relapses or in new enhancing lesions in any patient, even those with hypersensitivity reactions. Secondary analysis of those patients completing the study showed that the volume and number of enhancing lesions were reduced at a dose of 5 mg. There was also a regulatory type 2 T helper-cell response to altered peptide ligand that cross-reacted with the native peptide.