Frequency-dependent selection drives HBeAg seroconversion in chronic hepatitis B virus infection.

HBeAg seroconversion is an important stage in the evolution of a chronic hepatitis B virus (HBV) infection that usually leads to control of viral replication and a reduced risk for liver cirrhosis and cancer. Since current therapies for the HBV-associated liver inflammation that is known as chronic hepatitis B (CHB). Rarely induce permanent HBeAg seroconversion, there is a need to understand the mechanisms responsible for the purpose of identifying new therapeutic targets. Currently, the most widely accepted hypothesis is that the patient's humoral and cellular immune responses to the HBV initiate HBeAg seroconversion. Although we accept that this hypothesis cannot be excluded, we propose an alternative that is consistent with published data on HBeAg seroconversion. We postulate, as others have, that the HBeAg suppresses the immune response to the HBV. However, production of the HBeAg incurs a metabolic cost to the hepatocyte which reduces the replicative capacity of the virus. Consequently, HBeAg-negative viruses replicate faster than HBeAg-positive viruses. HBeAg-negative variants arise de novo; and when their frequency in the population is low they have a replicative advantage. However, they also benefit from the immunosuppressive effects of the HBeAg-positive viruses in the population. As HBeAg-negative variants increase in frequency and HBeAg levels fall, the immune system recognizes the HBV, and HBeAg seroconversion occurs as a consequence of frequency-dependent selection acting on HBeAg-negative variants. This hypothesis explains the wide inter-individual variation in age of seroconversion, the increased rate of seroconversion during anti-viral treatment and the phenomena of both spontaneous and post-treatment HBeAg reversions (in which patients cycle between the HBeAg-positive and negative phases of their infection).

TCRγδ(+)CD4(-)CD8(-) T cells suppress the CD8(+) T-cell response to hepatitis B virus peptides, and are associated with viral control in chronic hepatitis B.

The immune mechanisms underlying failure to achieve hepatitis B e antigen (HBeAg) seroconversion associated with viral control in chronic hepatitis B (CHB) remain unclear. Here we investigated the role of CD4(-)CD8(-) T (double-negative T; DNT) cells including TCRαß(+) DNT (αß DNT) and TCRγδ(+) DNT (γδ DNT) cells. Frequencies of circulating DNT cell subsets were measured by flow cytometry in a retrospective cohort of 51 telbivudine-treated HBeAg-positive CHB patients, 25 immune tolerant carriers (IT), 33 inactive carriers (IC), and 37 healthy controls (HC). We found that γδ DNT cell frequencies did not significantly change during treatment, being lower at baseline (P = 0.019) in patients with HBeAg seroconversion after 52 weeks of antiviral therapy (n = 20) than in those without (n = 31), and higher in the total CHB and IT than IC and HC groups (P<0.001). αß DNT cell frequencies were similar for all groups. In vitro, γδ DNT cells suppressed HBV core peptide-stimulated interferon-γ and tumor necrosis factor-α production in TCRαß(+)CD8(+) T cells, which may require cell-cell contact, and could be partially reversed by anti-NKG2A. These findings suggest that γδ DNT cells limit CD8(+) T cell response to HBV, and may impede HBeAg seroconversion in CHB.

Circulating chemokine (C-X-C Motif) receptor 5(+) CD4(+) T cells benefit hepatitis B e antigen seroconversion through IL-21 in patients with chronic hepatitis B virus infection.

UNLABELLED: Given the clinical significance of hepatitis B e antigen (HBeAg) seroconversion in chronic hepatitis B virus (HBV) infection, it is critical to elucidate the mechanisms regulating this process. In the present study, we found that the frequency of circulating chemokine (C-X-C motif) receptor 5 (CXCR5)(+) CD4(+) T cells was higher in patients who had achieved HBeAg seroconversion in both cross-sectional (P < 0.001) and longitudinal (P = 0.009) studies. These cells were able to produce a significantly higher level of intracellular interleukin 21 (IL-21) after stimulation with HBV peptides in patients with telbivudine-induced HBeAg seroconversion (P = 0.007). Furthermore, sorted CXCR5(+) CD4(+) T cells from HBeAg seroconverters boosted a higher frequency of antibody against hepatitis B e antigen (anti-HBe)-secreting B cells in coculture assay (P = 0.011). Of note, the increase in frequency of anti-HBe-secreting B cells was abrogated by soluble recombinant IL-21 receptor-Fc chimera (P = 0.027), whereas exogenous recombinant IL-21 enhanced this effect (P = 0.043). Additionally, circulating CXCR5(+) CD4(+) T cells shared similar phenotypic markers, and were positively correlated in frequency with, splenic follicular T helper cells. CONCLUSION: Circulating CXCR5(+) CD4(+) T cells, by producing IL-21, may have a significant role in facilitating HBeAg seroconversion in patients with chronic HBV infection.

Selection pressure on the hepatitis B virus pre-S/S and P open reading frames in Tongan subjects with a chronic hepatitis B virus infection.

Identification of the full repertoire of hepatitis B virus (HBV) peptides that are presented to CD8+ T cells by common HLA class I alleles will be useful for designing immunotherapies for chronic hepatitis B. One hundred and seventy five cloned sequences containing the pre-S/S and P open reading frames (ORF) of the HBV were obtained from serum HBV-DNA of HBeAg-positive (n=4) and HBeAg-negative (inactive healthy carriers (IHC), n=16) Tongan subjects with an inactive chronic HBV infection. In addition, 34 and 32 sequences were obtained 5.2±1.4 (mean±SD) years apart from eight subjects. PAML was used to identify codons in the pre-S/S and P ORFs that were under positive selection pressure (ω>1). The number of non-synonymous substitutions in these codons was compared in IHC who were homozygous for either HLA-B∗4001 (n=9) or HLA-B*5602 (n=7), and who were either positive (n=6) or negative (n=10) for HLA-A*02. 34 codons in the pre-S/S and 11 codons in the P ORFs were under positive selection pressure. There was a higher number of non-synonymous substitutions in these codons in HBeAg-negative versus HBeAg-positive subjects in the P (p=0.02) but not the pre-S/S (p=0.64) ORF. There was no association between any HLA class I allele and non-synonymous substitutions in these codons. There was no increase in positive selection pressure on the pre-S/S and P ORFs with time. In conclusion, we could not find HLA class I-restricted selection pressure on any pre-S/S or P ORF amino acid; raising the possibility that peptide-based immunotherapies for chronic hepatitis B may not require peptides from these ORFs.

High serum IL-21 levels after 12 weeks of antiviral therapy predict HBeAg seroconversion in chronic hepatitis B.

BACKGROUND & AIMS: Interleukin-21 (IL-21) stimulates T cell and B cell responses and plays a role in control of chronic viral infections. The role of IL-21 in chronic hepatitis B virus (HBV) infection is not understood. METHODS: Serum IL-21 levels were measured by enzyme immunoassay in 75 HBeAg-positive chronic hepatitis B (CHB) patients undergoing telbivudine treatment. The findings were validated in 103 patients from a separate clinical trial of telbivudine. A complete response to telbivudine was defined as having both HBeAg seroconversion and serum HBV-DNA level <300 copies/ml by treatment week 52. The proportions of T-cells producing IL-21 and/or expressing programmed death 1 (PD-1) in peripheral blood mononuclear cells were assessed longitudinally during treatment by intracellular cytokine staining and flow cytometry. RESULTS: Median serum IL-21 levels at treatment week 12 were significantly higher in patients who did achieve vs. patients who did not achieve a complete response in both the initial (128.4 vs. 69.2 pg/ml, p=0.003) and the validation (142.2 vs. 89.9 pg/ml, p=0.004) trials. Serum levels of IL-21 (p=0.005) or HBV-DNA (p=0.003) levels at treatment week 12 independently predicted HBeAg seroconversion in the first year of treatment. The decrease in PD-1 expression on CD4(+) and CD8(+) T cells during the first 12 weeks on telbivudine treatment was not correlated with changes in IL-21 concentrations. CONCLUSIONS: Serum IL-21 levels may be a biomarker for HBeAg seroconversion, and may contribute to individualization of antiviral therapy in HBeAg-positive CHB. IL-21 may also have a role in immunotherapy for CHB.

Restored circulating invariant NKT cells are associated with viral control in patients with chronic hepatitis B.

Invariant NKT (iNKT) cells are involved in the pathogenesis of various infectious diseases. However, their role in hepatitis B virus (HBV) infection is not fully understood, especially in human species. In this study, 35 chronic hepatitis B (CHB) patients, 25 inactive carriers (IC) and 36 healthy controls (HC) were enrolled and the proportions of circulating iNKT cells in fresh isolated peripheral blood mononuclear cells (PBMC) were detected by flow cytometry. A longitudinal analysis was also conducted in 19 CHB patients who received antiviral therapy with telbivudine. Thereafter, the immune functions of iNKT cells were evaluated by cytokine secretion and a two-chamber technique. The median frequency of circulating iNKT cells in CHB patients (0.13%) was lower than that in HC (0.24%, P = 0.01) and IC (0.19%, P = 0.02), and increased significantly during antiviral therapy with telbivudine (P = 0.0176). The expressions of CC chemokine receptor 5 (CCR5) and CCR6 were dramatically higher on iNKT cells (82.83%±9.87%, 67.67%±16.83% respectively) than on conventional T cells (30.5%±5.65%, 14.02%±5.92%, both P<0.001) in CHB patients. Furthermore, iNKT cells could migrate toward the CC chemokine ligand 5. Patients with a high ratio (≥1.0) of CD4-/CD4+ iNKT cells at baseline had a higher rate (58.33%) of HBeAg seroconversion than those with a low ratio (<1.0, 0%, P = 0.0174). In conclusion, there is a low frequency of peripheral iNKT cells in CHB patients, which increases to normal levels with viral control. The ratio of CD4-/CD4+ iNKT cells at baseline may be a useful predictor for HBeAg seroconversion in CHB patients on telbivudine therapy.

Hepatitis B virus genotype B with G1896A and A1762T/G1764A mutations is associated with hepatitis B related acute-on-chronic liver failure.

The existence of statistical associations between hepatitis B-related acute-on-chronic liver failure and both hepatitis B virus (HBV) genotype and mutations in the basal core promoter (BCP) and precore (PC) regions needs to be confirmed. A total of 322 patients with a chronic HBV infection, including 77 with hepatitis B-related acute-on-chronic liver failure, 109 with hepatocellular carcinoma (HCC) and 136 with chronic hepatitis B (CHB) were enrolled. The HBV genotype and the presence of mutations in the BCP/PC regions were determined by direct sequencing, and the frequencies were compared in the three patient groups. Overall, 198/322 (61.5%) were infected with genotype B and 124/322 (38.5%) with genotype C. Genotype B was significantly more frequent in patients with acute-on-chronic liver failure than CHB (92.2% vs. 60.3%, P < 0.001). As a contrast, genotype C was more common in patients with HCC than CHB (58.7% vs. 39.7%, P = 0.003). In genotype B patients, the A1762T/G1764A, A1846T, and G1896A mutations were significantly more prevalent in patients with acute-on-chronic liver failure than CHB (50.7% vs. 28.0%, P = 0.004; 59.2% vs. 34.1%, P = 0.002; 69.0% vs. 41.5%, P = 0.001, respectively). In multivariate analysis, the risk factors for acute-on-chronic liver failure were genotype B, A1762T/G1764A, and G1896A. In conclusion, CHB patients with genotype B, G1896A, and A1762T/G1764A had a higher tendency to develop liver failure than patients with genotype C. Therefore, HBV genotyping and detecting G1896A and A1762T/G1764A mutations might have important clinical implications as predictive risk factors for hepatitis B-related acute-on-chronic liver failure.

Evidence for reduced selection pressure on the hepatitis B virus core gene in hepatitis B e antigen-negative chronic hepatitis B.

The mechanisms underlying the high levels of hepatitis B virus (HBV) replication that cause hepatitis B e antigen (HBeAg)-negative chronic hepatitis B (e-CHB) are unknown. Impaired anti-HBV immunity, which may be measurable as a relaxation of selection pressure on the virus, is possible. A group of Tongans (n = 345) with a chronic HBV infection, including seven with e-CHB, were genotyped at HLA class I. The repertoire of HBV core-gene codons under positive selection pressure was defined by phylogenetic analysis (by using the paml program) of 708 cloned sequences extracted from the 67 of these 345 subjects with the same repertoire of HLA class I alleles as the seven e-CHB individuals and matched controls (see below). The frequency of non-synonymous mutations at these codons was measured in longitudinal data from 15 subjects. Finally, the number of non-synonymous mutations at these codons was compared in seven groups comprised of one subject with e-CHB and 1-3 HLA class I-matched controls with an inactive, HBeAg-negative chronic HBV infection (e-InD). Nineteen codons in the core gene were under positive selection pressure. There was a high frequency of new non-synonymous mutations at these codons (P<0.0001) in longitudinal data. The mean number of these 19 codons with non-synonymous mutations was lower (P = 0.02) in HBV from subjects with e-CHB (4.4±0.5 codons per subject) versus those with e-InD (6.4±0.4 codons per subject). There is a subtle relaxation in selection pressure on the HBV core gene in e-CHB. This may be due to impaired antiviral immunity, and could contribute to the high levels of viral replication that cause liver inflammation in this disease.

Complementarity-determining region 3 size spectratypes of T cell receptor beta chains in CD8+ T cells following antiviral treatment of chronic hepatitis B.

An increased CD8(+) T cell response to hepatitis B virus (HBV) peptides occurs between 12 and 24 weeks after starting antiviral therapy for chronic hepatitis B. It is not known whether these cells have antiviral function. The aim of this study was to determine whether clonal expansions of CD8(+) T cells at these time points predict the virological response to therapy. Peripheral blood CD8(+) T cells were obtained from 20 patients treated with lamivudine or telbivudine for chronic hepatitis B at baseline, 12 weeks, and 24 weeks. The CDR3 spectratype of each T cell receptor (TCR) ß chain variable region (Vß) gene family was analyzed, and the changes in the numbers of Vß families with clonal expansions were compared in subjects with (n = 12) and without (n = 8) a virological response (52 week HBV DNA < 300 copies/ml). The number of CD8(+) TCR Vß families with clonal expansions at 12 weeks relative to baseline (median [10th to 90th percentile], +2.5 [0 to +7] versus +1 [0 to +2], P = 0.03) and at 24 weeks relative to 12 weeks (+1 [0 to +2] versus -1 [-3 to +4], P = 0.006) was higher in subjects with a virological response versus subjects without a virological response, as were interleukin-2 (IL-2) but not IL-21 mRNA levels in peripheral blood mononuclear cells. The duration of new expansions at 12 weeks was higher (P < 0.0001) in responders. Increased numbers of CD8(+) T cell expansions after antiviral therapy are associated with a virological response to treatment. These CD8(+) T cells are a potential target for a therapeutic vaccine for chronic hepatitis B.

Presence of valine at position 27 of the hepatitis B virus core gene is associated with severe liver inflammation in Chinese patients.

Although it is widely believed that cytotoxic T lymphocytes (CTL) are responsible for severe flares of chronic hepatitis B that lead to liver failure, the published evidence to support this hypothesis is weak. The frequency of the I27V mutation in the HBV core gene, which produces a core 18-27 peptide capable of binding HLA-A*02, was compared in Chinese patients with severe liver inflammation (n = 77, including 39 with acute-on-chronic liver failure), moderate liver inflammation (n = 44) and inactive disease (n = 45). The frequency with which V27 reverted to the wild-type I27 was compared in severe liver inflammation patients who were either HLA-A*02 positive (n = 5) or negative (n = 5). The frequency of patients with a V27 positive HBV was higher in severe than in moderate liver inflammation (23.4% vs. 6.8%, P = 0.02) or inactive disease (23.4% vs. 4.7%, P = 0.006). After a minimum of 3 months follow-up, the frequency of reversion of V27 to the wild-type I27 was higher in HLA-A*02 positive than negative patients (5/5 vs. 1/5, P = 0.05). In summary, this is the first data showing an association between a specific amino acid mutation (I27V) and severe liver inflammation in patients with chronic hepatitis B. This mutation would produce a peptide that is known to bind HLA-A*02 and stimulate CTL. The high frequency of reversion to wild-type I27 in HLA-A*02 positive subjects suggests that CTL recognizing this peptide exist, and is consistent with the possibility that they contribute to the pathophysiology of severe liver inflammation in chronic hepatitis B.

Associations between HLA class I alleles and escape mutations in the hepatitis B virus core gene in New Zealand-resident Tongans.

The full repertoire of hepatitis B virus (HBV) peptides that bind to the common HLA class I molecules found in areas with a high prevalence of chronic HBV infection has not been determined. This information may be useful for designing immunotherapies for chronic hepatitis B. We identified amino acid residues under positive selection pressure in the HBV core gene by phylogenetic analysis of cloned DNA sequences obtained from HBV DNA extracted from the sera of Tongan subjects with inactive, HBeAg-negative chronic HBV infections. The repertoires of positively selected sites in groups of subjects who were homozygous for either HLA-B*4001 (n = 10) or HLA-B*5602 (n = 7) were compared. We identified 13 amino acid sites under positive selection pressure. A significant association between an HLA class I allele and the presence of nonsynonymous mutations was found at five of these sites. HLA-B*4001 was associated with mutations at E77 (P = 0.05) and E113 (P = 0.002), and HLA-B*5602 was associated with mutations at S21 (P = 0.02). In addition, amino acid mutations at V13 (P = 0.03) and E14 (P = 0.01) were more common in the seven subjects with an HLA-A*02 allele. In summary, we have developed an assay that can identify associations between HLA class I alleles and HBV core gene amino acids that mutate in response to selection pressure. This is consistent with published evidence that CD8(+) T cells have a role in suppressing viral replication in inactive, HBeAg-negative chronic HBV infection. This assay may be useful for identifying the clinically significant HBV peptides that bind to common HLA class I molecules.

Direct evidence for immunomodulatory properties of ribavirin on T-cell reactivity to hepatitis C virus.

BACKGROUND/AIM: An understanding of ribavirin's beneficial effects on treatment outcome in chronic hepatitis C (CH-C) may help to develop new treatment approaches. Here we investigated whether ribavirin directly affects HCV-specific reactivity of CD4+T-lymphocytes from patients with CH-C. METHODS: Peripheral blood mononuclear cells from forty HCV RNA positive patients were cultured ex vivo with HCV core, NS3, NS4 alone, and with different concentrations of ribavirin. Virus-specific CD4+ T-cell reactivity was analysed by a proliferation assay; quantitation of cytokine (interferon-gamma, IL-10, IL-5, IL-12p35, IL-12p40) mRNA levels; measurement of interferon-gamma and IL-10 production (by ELISA) and enumeration of interferon-gamma and IL-10 producing T-cells by Elispot assays. RESULTS: At 2-5 microM ribavirin induced de novo or enhanced T-cell proliferation to HCV antigens in a proportion of patients. Increased T-cell proliferation was associated with decreased IL-10 production in response to HCV core and reduced frequency of IL-10 producing CD4+ T-cells, while interferon-gamma levels remained unchanged. At 20 microM ribavirin markedly suppressed T-cell proliferation, and interferon-gamma mRNA expression to HCV antigens. CONCLUSIONS: Ribavirin, at clinically achievable plasma levels, modulates directly the T-cell responses to HCV antigens in some CH-C patients. Suppression of IL-10 production may represent a useful strategy to induce/augment T-cell reactivity to HCV.

Genetic diversity and linkage disequilibrium in the Polynesian population of Niue Island.

Isolated populations that recently have been derived from small homogeneous groups of founders should have low genetic diversity and high levels of linkage disequilibrium and should be ideal for mapping ancestral polymorphisms that influence complex genetic disease susceptibility. Populations that fulfill these criteria have been difficult to identify. We have been looking for Polynesian populations with these characteristics, because Polynesians have high rates of complex genetic diseases. In Niue Islanders all ancestral female (mitochondrial HSVI sequence) and 90.4% of ancestral male (Y-chromosome haplogroup) lineages are of Southeast Asian origin. The frequency of European Y-chromosome haplogroups is 7.2%. The diversities of mitochondrial HSV1 sequences (h = 0.18 +/- 0.05) and Y-chromosome haplo-groups (h = 0.18 +/- 0.05) are lower than values published for any other population. Ten autosomal microsatellites spaced over 5.8 cM show low allele numbers in Niue Islanders relative to Europeans (55 vs. 88 total alleles, respectively) and a modest reduction in heterozygous loci (0.71 +/- 0.02 vs. 0.78 +/- 0.02, p = 0.04). The higher linkage disequilibrium (d2) between these loci in Niue Islanders relative to Europeans (p = 0.001) is negatively correlated (r = -0.47, p = 0.01) with genetic distance. In summary, Niue Islanders are genetically isolated and have a homogeneous Southeast Asian ancestry. They have reduced autosomal genetic diversity and high levels of linkage disequilibrium that are consistent with the influence of genetic drift mechanisms, such as a founder effect or bottlenecks. High-powered linkage disequilibrium studies designed to map ancestral polymorphisms that influence complex genetic disease susceptibility may be feasible in this population.

Polymorphisms of CARD15/NOD2 and CD14 genes in New Zealand Crohn's disease patients.

Polymorphisms in the CARD15/NOD2 gene, which encodes a cytosolic protein involved in bacterial recognition, are associated with development of Crohn's disease (CD). Other potential susceptibility genes such as CD14 may compound the risk of developing CD. We examined the frequency of the three major CARD15 risk alleles (3020insC/L1007fsinsC, G908R and R702W), and a functional polymorphism (-159C/T) in the promoter of the CD14 gene in 185 CD patients in New Zealand and 187 ethnically matched controls. The frequencies of the 3020insC (8.1 vs 0.8%, P < 0.0001), G908R (3.5 vs 2.4%, P = 0.37) and R702W (7.3 vs 5.1%, P = 0.21) alleles in CD patients and controls, respectively, were similar to those described in Australia, and the ancestral countries of Scotland, Ireland and the UK. Only the 3020insC polymorphism was found to be a significant risk factor for CD in our New Zealand cohort (odds ratio = 10.91 [95% confidence intervals 3.30-36.08]; P < 0.0001 for heterozygotes), but not a single patient was homozygous for the 3020insC polymorphism. The T allele (51 vs 50%, P = 0.77) and TT genotype (26 vs 24%, P = 0.84) frequencies of the -159C/T CD14 gene promoter polymorphism did not significantly differ between CD patients and controls. In summary, our findings provide evidence that the CARD15 3020insC risk allele influences disease susceptibility in a small proportion (<17%) of New Zealand CD patients, whereas there was no evidence that the CD14 -159C/T polymorphism is associated with CD.

Blocking of interleukin-10 receptor--a novel approach to stimulate T-helper cell type 1 responses to hepatitis C virus.

Chronic hepatitis C virus (HCV) infection is associated with weak CD4+ T-helper type 1 reactivity and enhanced interleukin-10 production to HCV antigens. Here we demonstrate in vitro that monoclonal antibody-induced blockade of IL-10 receptor (IL-10R) generates a favorable balance of CD4+ T-cell responses to HCV. The addition of anti-IL-10R to mononuclear cells leads to a dose-dependent increase of T-cell proliferative response to HCV core, non-structural proteins 3 and 4. In competition experiments, anti-IL-10R reversed the inhibitory effect of IL-10 on HCV-specific T-cell proliferation. Furthermore, the blockade of IL-10R altered the balance towards type 1 antiviral T-cell reactivity with an increased frequency of HCV-specific IFN-gamma producing T-cells and IFN-gamma secretion. The impact of IL-10R blockade on T-cell reactivity to HCV demonstrates the major role of IL-10 in suppressing antiviral T-cell responses. Blocking IL-10 activity may be a useful immunotherapy approach to enhance the efficacy of antiviral treatment in chronic hepatitis C.

Asthma phenotypes in Niue Islanders.

OBJECTIVE: The aim of this study was to identify asthma phenotypes in patients of Niue Island ancestry that might be suitable for susceptibility gene mapping studies. METHODOLOGY: Two hundred and sixteen Niue Islanders with physician-diagnosed asthma that was not secondary to other medical conditions were recruited through community organisations. Fifty-one of the subjects with asthma were resident on Niue Island and 165 in New Zealand. Each subject was interviewed and tested for atopy, serum [IgE] (5% quantile, median, 95% quantile) and lung function. RESULTS: There were two groups of subjects defined by an age of onset of asthma less than 12 years of age (childhood-onset, boys:girls 64:65) and greater than 12 years of age (adult-onset, men:women 11:76). A positive response (wheal > 3 mm) to at least one aeroallergen was seen in 181 patients, with 168/181 (92.8%) responding to house dust mite. Twenty-eight subjects with asthma were non-atopic (no detectable wheal) and the atopy status of seven subjects with asthma could not be determined (wheal < 3 mm). In childhood-onset asthma, serum IgE levels were higher (P < 0.0001) in subjects with atopic than in subjects with non-atopic asthma. In adult-onset asthma, serum IgE levels were higher (P < 0.0001) in subjects with atopic asthma than in either subjects with non-atopic asthma or matched non-atopic subjects without asthma. The asthma phenotypes in Niue Island and New Zealand residents were similar. CONCLUSIONS: Both atopic and non-atopic asthma phenotypes exist in Niue Islanders resident in Niue and New Zealand. The potential for mapping asthma susceptibility genes in this isolated population is discussed.

Single nucleotide polymorphisms in the interferon-gamma and interleukin-10 genes do not influence chronic hepatitis C severity or T-cell reactivity to hepatitis C virus.

BACKGROUND: The mechanisms by which interferon-gamma (IFN-gamma) contributes to inter-individual heterogeneity in the severity of chronic hepatitis C (CH-C) are unknown. In 116 consecutive patients with CH-C, we tested the hypothesis that host genetic factors regulating IFN-gamma production and activity influence the severity of liver damage and hepatitis C virus (HCV)-specific T-cell reactivity. METHODS: We determined the genotypes of functionally significant polymorphisms in the IFN-gamma gene and in the promoter of interleukin-10 (IL-10), a cytokine that counteracts IFN-gamma. We also measured concanavalin A (Con A)-stimulated IL-10 and IFN-gamma production, and the frequency of virus-specific T-cells, producing IFN-gamma or IL-10. RESULTS: The grade of inflammation and the stage of fibrosis of CH-C showed no associations with either the IFN-gamma or IL-10 promoter polymorphisms or with Con A-stimulated IL-10 or IFN-gamma production. Similarly, there were no associations between HCV-specific T-cell frequencies and these host genetic factors. On multivariate analysis, the grade of inflammation and the duration of HCV infection accounted for only 37% of the variance in the stage of CH-C (P<0.0001). This percentage did not increase by including any genetic variables in the analyses. CONCLUSION: Future studies investigating the entire cytokine gene sequences will provide better information regarding genetic variations responsible for inter-individual differences in the severity of CH-C.