Selma A. Palácios

Genetic heterogeneity in susceptibility to autoimmune hepatitis types 1 and 2

OBJECTIVES:Susceptibility to autoimmune hepatitis (AIH) type 1 has been associated with DRB1*03, DRB1*04, and DRB3 alleles in European and North-American whites, with DRB1*04 in Japan, and with DRB1*04 and DRB1*13 in Latin America. Very few studies have been performed on AIH type 2. The aim of the present study was to evaluate the association of AIH types 1 and 2 with HLA-DR and DQ loci.METHODS:We performed HLA-DRB and -DQB1 typing by polymerase chain reaction amplification with sequence-specific primers (PCR-SSP) in 139 AIH patients. Most had AIH type 1 associated with circulating anti-smooth muscle antibody with F-actin specificity or antinuclear antibody. Twenty-eight patients presented AIH type 2 with anti-liver/kidney microsome type 1 or anti-liver cytosol type 1 antibodies.RESULTS:We observed a significant increase of DRB1*13 (70%vs 26% of controls, p < 0.00001) and DRB3 (93%vs 69% of controls, p < 0.00001) in AIH type 1 patients. Analysis of patients without DRB1*13 disclosed a secondary association with DRB1*03 (70%vs 30% of controls, p= 0.0001) and either the DRB1*13 or the DRB1*03 alleles were present in the majority of these patients (91%vs 48% of controls, p= 0.001). Comparison of DRB1*13- and DRB1*03-positive subjects revealed that the former alleles conferred susceptibility to younger patients with AIH type 1. DQB1 typing showed a significant increase in DQB1*06 (68%vs 41% of controls, p= 0.00007) in strong linkage disequilibrium with DRB1*13, and a decrease in DQB1*0301 (8%vs 47% of controls, pc= 0.0003). On the other hand, HLA typing of patients with AIH type 2 disclosed a significant increase in the DRB1*07 (68%vs 20% of controls, pc < 0.00014), DRB4 (79%vs 43% of controls, pc= 0.004), and DQB1*02 (86%vs 42%, p= 0.00002) alleles. After exclusion of DRB1*07, a secondary association with HLA-DRB1*03 was further observed in these patients (78%vs 30%, p= 0.007) and most of them had either DRB1*07 or DRB1*03 (93%vs 44% of controls, pc < 0.0001).CONCLUSIONS:Our data indicate that predisposition to AIH types 1 and 2 is associated, respectively, with the DRB1*13 or DRB1*03 and DRB1*07 or DRB1*03 alleles, and suggest that protection against type 1 disease may be conferred by DQB1*0301. In addition, the cluster of DRB1*13 in children with AIH type 1 also supports the concept that different HLA alleles might influence the onset of the disease.

Cytotoxic T lymphocyte antigen–4 gene polymorphisms do not confer susceptibility to autoimmune hepatitis types 1 and 2 in Brazil

OBJECTIVES:Susceptibility to autoimmune hepatitis (AIH) has been linked to different HLA-DR antigens in distinct populations. Recently, an A–G polymorphism in exon 1 of the cytotoxic T lymphocyte antigen-4 (CTLA-4) gene was associated with predisposition to AIH type 1 (AIH-1) in white individuals in North America. This polymorphism has been associated with several other autoimmune diseases, presumably because of its effect in the expression of CTLA-4, an adhesion molecule that downregulates peripheral T cell responses. The aims of this study were to assess the frequency of CTLA-4 genotypes in Brazilian patients with AIH-1 and AIH type 2 (AIH-1), as well as to investigate the influence of these genotypes in disease expression.METHODS:Determination of CTLA-4 genotypes was carried out in 106 patients with AIH-1, 26 subjects with AIH-2, and 67 healthy control subjects by polymerase chain reaction (PCR)–based techniques.RESULTS:No difference in the distribution of CTLA-4 genotypes was observed in subjects with AIH-1 and AIH-2 as compared to healthy controls. Patients with AIH-1 and AIH-2 with the GG genotype exhibited lower γ-globulin and ALT levels, respectively.CONCLUSIONS:Susceptibility to AIH-1 and AIH-2 in Brazilian patients is not influenced by exon 1 CTLA-4 gene polymorphisms at position 49.

Analysis of major histocompatibility complex and CTLA-4 alleles in Brazilian patients with primary biliary cirrhosis

Background and Aims:  Predisposition to primary biliary cirrhosis (PBC) has been classically linked to HLA‐DRB1 locus. However, the presence of the HLA‐DRB1*08 antigen has been reported in less than one‐third of PBC patients from Northern Europe and Japan. Recently, polymorphisms in the tumor necrosis factor alpha (TNFA) gene promoter at position −308 and in exon 1 of the cytotoxic T lymphocyte antigen‐4 (CTLA‐4) gene at position 49 have been associated with susceptibility to PBC in Caucasians. In addition, the presence of HLA‐DRB1*08 and the TNFA*1 allele was also linked to progression to end‐stage liver disease. The aims of the present study were to investigate the frequencies of HLA‐DR and DQ antigens and TNFA and CTLA‐4 alleles in PBC patients from a different genetic background, as well as to assess the role of TNFA alleles and HLA‐DR antigens in disease progression.

Autoimmune hepatitis in Brazilian patients is not linked to tumor necrosis factor α polymorphisms at position −308

BACKGROUND/AIMS Susceptibility to autoimmune hepatitis (AIH) has been linked to different HLA-DR antigens. Recently, AIH type 1 was associated with polymorphisms in the tumor necrosis factor alpha gene promoter (TNFA) at position -308. In this respect, the frequency of the TNFA*2 allele, in linkage disequilibrium with HLA-DRB1*0301, was shown to be significantly increased in whites with AIH type 1. The aim of this study was to assess the role of TNFA alleles in conferring susceptibility to AIH, studying a population where the disease is not primarily associated with HLA-DRB1*03. METHODS The determination of HLA-DRB1 and TNFA alleles was performed in 92 patients with AIH type 1, 29 subjects with AIH type 2 and 83 healthy controls by polymerase chain reaction-based techniques. RESULTS The distribution of TNFA alleles was similar in patients with AIH types 1 and 2, when compared with controls. In addition, the TNFA*2 allele was identified in patients carrying HLA-DR antigens other than HLA-DRB1*03. Interestingly, higher gammaglobulin levels were observed in TNFA*2 positive patients. CONCLUSIONS Our data indicate that susceptibility to AIH remains primarily linked to the HLA-DRB1 locus, and suggest that the association of AIH with TNFA*2 previously observed in whites might be secondary to a linkage disequilibrium with HLA-DRB1*0301.

Lack of evidence for the pathogenic role of iron and HFE gene mutations in Brazilian patients with nonalcoholic steatohepatitis

The hypothesis of the role of iron overload associated with HFE gene mutations in the pathogenesis of nonalcoholic steatohepatitis (NASH) has been raised in recent years. In the present study, biochemical and histopathological evidence of iron overload and HFE mutations was investigated in NASH patients. Thirty-two NASH patients, 19 females (59%), average 49.2 years, 72% Caucasians, 12% Mulattoes and 12% Asians, were submitted to serum aminotransferase and iron profile determinations. Liver biopsies were analyzed for necroinflammatory activity, architectural damage and iron deposition. In 31 of the patients, C282Y and H63D mutations were tested by PCR-RFLP. Alanine aminotransferase levels were increased in 30 patients, 2.42 1.12 times the upper normal limit on average. Serum iron concentration, transferrin saturation and ferritin averages were 99.4 31.3 g/dl, 33.1 12.7% and 219.8 163.8 g/dl, respectively, corresponding to normal values in 93.5, 68.7 and 78.1% of the patients. Hepatic siderosis was observed in three patients and was not associated with architectural damage (P = 0.53) or with necroinflammatory activity (P = 0.27). The allelic frequencies (N = 31) found were 1.6 and 14.1% for C282Y and H63D, respectively, which were compatible with those described for the local population. In conclusion, no evidence of an association of hepatic iron overload and HFE mutations with NASH was found. Brazilian NASH patients comprise a heterogeneous group with many associated conditions such as hyperinsulinism, environmental hepatotoxin exposure and drugs, but not hepatic iron overload, and their disease susceptibility could be related to genetic and environmental features other than HFE mutations.

TNF-alpha polymorphisms are associated with obsessive-compulsive disorder

INTRODUCTION Several lines of evidence support an immunologic involvement in obsessive-compulsive disorder (OCD): the increased prevalence of OCD in patients with rheumatic fever (RF), and the aggregation of obsessive-compulsive spectrum disorders among relatives of RF probands. Tumor necrosis factor alpha is a proinflammatory cytokine involved in RF and other autoimmune diseases. Polymorphisms in the promoter region of the TNFA gene have been associated with RF. Given the association between OCD and RF, the goal of the present study was to investigate a possible association between polymorphisms within the promoter region of TNFA and OCD. MATERIALS AND METHODS Two polymorphisms were investigated: -308 G/A and -238 G/A. The allelic and genotypic frequencies of these polymorphisms were examined in 111 patients who fulfilled DSM-IV criteria for OCD and compared with the frequencies in 250 controls. RESULTS Significant associations were observed between both polymorphisms and OCD. For -238 G/A, an association between the A allele and OCD was observed (chi(2)=12.05, p=0.0005). A significant association was also observed between the A allele of the -308 G/A polymorphism and OCD (chi(2)=7.09, p=0.007). Finally, a haplotype consisting of genotypes of these two markers was also examined. Significant association was observed for the A-A haplotype (p=0.0099 after correcting for multiple testing). DISCUSSION There is association between the -308 G/A and -238 G/A TNFA polymorphisms and OCD in our Brazilian sample. However, these results need to be replicated in larger samples collected from different populations.

Familial amyloidotic polyneuropathy type 1 in Brazil is associated with the transthyretin Val30Met variant

UNLABELLED Familial amyloidotic polyneuropathy type 1 (FAP1) is an inherited systemic amyloidosis that is secondary to the deposition of transthyretin (TTR) variants in peripheral nerves and in certain visceral organs. More than 50 distinct mutations have already been described in the TTR gene. Yet, the most common mutation found worldwide is a substitution of valine for methionine in position 30 (Val30Met). Currently, the variants of TTR in Brazilian FAP1 patients remain largely unknown and the aim of this study was to analyze the frequency of the TTR Val30Met mutation in such Brazilian subjects. METHODS Thirty-two FAP1 patients belonging to 24 different families were studied for the presence of Val30Met variant by PCR-RFLP. RESULTS All Brazilian FAP1 subjects studied were positive for the TTR Val30Met variant. As expected, all of them were heterozygous for the mutation. CONCLUSION TTR Val30Met mutation was the sole TTR variant found in Brazilian FAP1 patients in this cohort, and it was present even in those subjects without a clear history of Portuguese ancestry.

Analysis of HLA-A antigens and C282Y and H63D mutations of the HFE gene in Brazilian patients with hemochromatosis

The hemochromatosis gene, HFE, is located on chromosome 6 in close proximity to the HLA-A locus. Most Caucasian patients with hereditary hemochromatosis (HH) are homozygous for HLA-A3 and for the C282Y mutation of the HFE gene, while a minority are compound heterozygotes for C282Y and H63D. The prevalence of these mutations in non-Caucasian patients with HH is lower than expected. The objective of the present study was to evaluate the frequencies of HLA-A antigens and the C282Y and H63D mutations of the HFE gene in Brazilian patients with HH and to compare clinical and laboratory profiles of C282Y-positive and -negative patients with HH. The frequencies of HLA-A and C282Y and H63D mutations were determined by PCR-based methods in 15 male patients (median age 44 (20-72) years) with HH. Eight patients (53%) were homozygous and one (7%) was heterozygous for the C282Y mutation. None had compound heterozygosity for C282Y and H63D mutations. All but three C282Y homozygotes were positive for HLA-A3 and three other patients without C282Y were shown to be either heterozygous (N = 2) or homozygous (N = 1) for HLA-A3. Patients homozygous for the C282Y mutation had higher ferritin levels and lower age at onset, but the difference was not significant. The presence of C282Y homozygosity in roughly half of the Brazilian patients with HH, together with the findings of HLA-A homozygosity in C282Y-negative subjects, suggest that other mutations in the HFE gene or in other genes involved in iron homeostasis might also be linked to HH in Brazil.

Autoimmune Hepatitis in Brazil: An Overview

Autoimmune hepatitis is an immune cell‐mediated chronic liver disease of unknown cause that leads, when untreated, to cirrhosis and liver failure. Importantly, this disease affects not only adults but children as well. Genetic susceptibility is clearly important and the major susceptibility factor identified up to now is the HLA‐DRB1 locus, but other genes may play a role as well. HLA‐DRB1 alleles present in South American patients differ from those found in patients in other parts of the world. In addition, we have recently identified two chromosomal regions where additional susceptibility factors may be found in Brazilian patients, namely, the class III MHC region and the 5q31 region where the IL‐4 and IL‐13 genes are located. This review discusses the current knowledge of the pathogenesis of this autoimmune disease occurring in the setting of an immune‐privileged organ, the liver, and compares the data on gene polymorphisms studied in Brazil and in other parts of the world.

Association study between functional polymorphisms in the TNF-alpha gene and obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a prevalent psychiatric disorder of unknown etiology. However, there is some evidence that the immune system may play an important role in its pathogenesis. In the present study, two polymorphisms (rs1800795 and rs361525) in the promoter region of the cytokine tumor necrosis factor-alpha (TNFA) gene were genotyped in 183 OCD patients and in 249 healthy controls. The statistical tests were performed using the PLINK(®) software. We found that the A allele of the TNFA rs361525 polymorphism was significantly associated with OCD subjects, according to the allelic χ(2) association test (p=0.007). The presence of genetic markers, such as inflammatory cytokines genes linked to OCD, may represent additional evidence supporting the role of the immune system in its pathogenesis.