Human leukocyte antigen class II and III alleles and severity of hepatitis C virus-related chronic liver disease

Effect of human leukocyte antigen heterozygosity on infectious disease outcome: the need for allele-specific measures

BACKGROUND

Doherty and Zinkernagel, who discovered that antigen presentation is restricted by the major histocompatibility complex (MHC, called HLA in humans), hypothesized that individuals heterozygous at particular MHC loci might be more resistant to particular infectious diseases than the corresponding homozygotes because heterozygotes could present a wider repertoire of antigens. The superiority of heterozygotes over either corresponding homozygote, which we term allele-specific overdominance, is of direct biological interest for understanding the mechanisms of immune response; it is also a leading explanation for the observation that MHC loci are extremely polymorphic and that these polymorphisms have been maintained through extremely long evolutionary periods. Recent studies have shown that in particular viral infections, heterozygosity at HLA loci was associated with a favorable disease outcome, and such findings have been interpreted as supporting the allele-specific overdominance hypothesis in humans.

METHODS

An algebraic model is used to define the expected population-wide findings of an epidemiologic study of HLA heterozygosity and disease outcome as a function of allele-specific effects and population genetic parameters of the study population.

RESULTS

We show that overrepresentation of HLA heterozygotes among individuals with favorable disease outcomes (which we term population heterozygote advantage) need not indicate allele-specific overdominance. On the contrary, partly due to a form of confounding by allele frequencies, population heterozygote advantage can occur under a very wide range of assumptions about the relationship between homozygote risk and heterozygote risk. In certain extreme cases, population heterozygote advantage can occur even when every heterozygote is at greater risk of being a case than either corresponding homozygote.

CONCLUSION

To demonstrate allele-specific overdominance for specific infections in human populations, improved analytic tools and/or larger studies (or studies in populations with limited HLA diversity) are necessary.

Interleukin-1, interleukin-10 and tumour necrosis factor-alpha gene polymorphisms in hepatitis C virus infection: an investigation of the relationships with spontaneous viral clearance and response to alpha-interferon therapy

BACKGROUND/AIMS

Though there is a consensus that the HLA DQB1*0301 allele is important in untreated HCV clearance, this association is not universal and a number of genes outside the major histocompatibility complex may also play a role in host responses to HCV infection. Prime candidates, at present, are the genes encoding pro-inflammatory and immuno-regulatory cytokines. The aim of this study was to investigate the relationship between a number of these candidate genes and both spontaneous and treatment related clearance of hepatitis C virus infection.

METHODS

Three members of the interleukin-1 gene family: IL-1A, IL-1B and IL-1RN, three polymorphic sites in the interleukin-10 gene promoter (- 1082, - 819, - 592) and two in the tumour necrosis factor-alpha promoter (- 308, - 238) were studied in two independent DNA banks, each with appropriate controls. Standard PCR-based genotyping techniques were used.

RESULTS

No significant difference in the distribution of any of the polymorphisms was found in either study set.

CONCLUSIONS

These findings in two large groups suggest that future investigations should focus on other candidate genes and may support the view that MHC-encoded susceptibility to chronic HCV infection may be determined by MHC class II rather than MHC class III genes.

Does hepatitis C virus cause severe liver disease only in people who drink alcohol?

Hepatitis C virus (HCV) infects about 170 million people worldwide, and has been portrayed in the media as a silent killer, incorrectly implying that cirrhosis and hepatocellular carcinoma are the certain final outcomes of infection. Results of numerous population-based surveys indicate that chronic HCV infection is highly prevalent in elderly people who, in most instances, do not develop end-stage liver disease. In individuals who do progress to cirrhosis and hepatocellular carcinoma alcohol plays a fundamental part, via mechanisms that result in increased viral replication, enhanced HCV quasispecies complexity, increased liver-cell death, suppression of immune responses, and iron overload. Although overlaps are present in the histological appearance of the liver in patients with hepatitis C who do and do not drink alcohol, histology could be of some help in revealing the role of alcohol in HCV disease progression even in people who deny drinking. Interventions and high-impact, continuous public-health campaigns are needed to persuade doctors and patients infected with HCV of the importance of abstaining from alcohol if risk of progression towards cirrhosis and hepatocellular carcinoma is to be reduced.

B and C hepatitis viruses, HLA-DQ1 and -DR3 alleles and autoimmunity in patients with hepatocellular carcinoma

BACKGROUND/AIMS

Hepatitis B and C involvement in hepatocellular carcinoma has been well established, but as yet not that of the human lymphocyte antigen (HLA) complex. To study viral, HLA and tumour interrelationships, 105 patients were evaluated for prevalence of viral markers and 161 patients, including 99 of the previous ones, for HLA allele frequency; the other 52 patients served as controls.

METHODS

Immunoassays, molecular assays, microlymphocytotoxicity.

RESULTS

Positivity for hepatitis B surface antigen and/or hepatitis C antibodies in 89% cirrhotic, 44% non-cirrhotic vs. 92% control patients (cirrhotic; all hepatitis C antibody positives were viraemic). Recurrent HLA alleles: HLA-Cw7 and -DQ1 in cirrhotic and control patients, HLA-Cw7, -B8 and -DR3 in non-cirrhotic patients compared with healthy controls (Pc=0.0000074, 0.000025, 0.0025, 0.00027 and 0.043, respectively).

CONCLUSIONS

Viral data suggest a high chronic infection rate for cirrhotic patients. Recurrent HLA-Cw7 is compatible with natural killer cell activity inhibition to virus-infected and tumour cells by HLA C molecules. Recurrent HLA-DQ1 and -DR3 suggest the existence of an autoimmune condition with cell destruction in cirrhotic and without cell destruction in non-cirrhotic patients as a consequence of autoreactive DQ-restricted T-helper (Th)1 and DR-restricted Th2 cells response, respectively. HLA-B8-DR3 linkage disequilibrium was possible. Thus, autoimmunity may have contributed to hepatocellular carcinoma development in these patients.

Tumor necrosis factor genetic polymorphisms and response to antiviral therapy in patients with chronic hepatitis C

OBJECTIVE

Hepatitis C virus (HCV) is the major causal agent of non-A, non-B hepatitis and the leading indication for liver transplantation worldwide. The emerging field of immunogenetics has confirmed the significant role of heritability in host immune responses to infectious pathogens. Both the major and non-major histocompatibility complex genes are increasingly identified as candidate genes hypothesized to influence the susceptibility to, or the course of, a particular disease. We hypothesized that polymorphisms within the major histocompatibility complex class III region that encode for tumor necrosis factors (TNF)-alpha and TNF-beta might be predictive of response to antiviral therapy in patients with chronic hepatitis C.

METHODS

A total of 155 subjects, including 110 HCV-seropositive individuals undergoing antiviral therapy and 45 ethnically similar HCV-negative controls, were studied. The HCV-positive patients had undergone antiviral treatment with either interferon monotherapy (n = 73) or in combination with ribavirin (n = 37) and were categorized as either nonresponders, sustained responders, or relapsers. Sixty (55%) patients had genotype 1 (1a or 1b). Genomic DNA was extracted, followed by polymerase chain reaction amplification and sequencing for two promoter TNF-alpha variants (at positions -238 and -308), as well as restriction fragment length analysis for four polymorphic loci within the TNF-beta gene (NcoI, TNFc, aa13, aa26).

RESULTS

Although there was a trend toward higher frequency of the A allele in the TNF 238 promoter among HCV-infected patients (12% vs 4%), there were no significant differences in the distribution of the genotypic polymorphisms between patients and controls. Patients with the TNF 238 A allele had higher pretreatment viral loads as compared with patients homozygous for the wild type allele (7.2 x 10(6) +/- 4.2 x 10(6) copies/ml vs 3.8 x 10(6) +/- 0.34 x 10(6) copies/ml, p = 0.03). However, there was no association between TNF genetic markers, including multiple haplotypic combinations, and response to therapy. In addition, there was no correlation with these polymorphic loci and histological severity of liver disease.

CONCLUSIONS

Although previous work has suggested potential roles for TNF in the pathogenesis of HCV infection, we were unable to identify any link between TNF genetic polymorphisms and histological severity or response to antiviral therapy.

Increased frequency of HLA-DR2 in patients with paroxysmal nocturnal hemoglobinuria and the PNH/aplastic anemia syndrome

Many autoimmune diseases are associated with HLA alleles, and such a relationship also has been reported for aplastic anemia (AA). AA and paroxysmal nocturnal hemoglobinuria (PNH) are related clinically, and glycophosphoinositol (GPI)-anchored protein (AP)-deficient cells can be found in many patients with AA. The hypothesis was considered that expansion of a PNH clone may be a marker of immune-mediated disease and its association with HLA alleles was examined. The study involved patients with a primary diagnosis of AA, patients with myelodysplastic syndrome (MDS), and patients with primary PNH. Tests of proportions were used to compare allelic frequencies. For patients with a PNH clone (defined by the presence of GPI-AP-deficient granulocytes), regardless of clinical manifestations, there was a higher than normal incidence of HLA-DR2 (58% versus 28%; z = 4.05). The increased presence of HLA-DR2 was found in all frankly hemolytic PNH and in PNH associated with bone marrow failure (AA/PNH and MDS/PNH). HLA-DR2 was more frequent in AA/PNH (56%) than in AA without a PNH clone (37%; z = 3.36). Analysis of a second cohort of patients with bone marrow failure treated with immunosuppression showed that HLA-DR2 was associated with a hematologic response (50% of responders versus 34% of nonresponders; z = 2.69). Both the presence of HLA-DR2 and the PNH clone were independent predictors of response but the size of PNH clone did not correlate with improvement in blood count. The results suggest that clonal expansion of GPI-AP-deficient cells is linked to HLA and likely related to an immune mechanism.

The natural history of hepatitis C virus infection

The natural history of HCV infection remains ill-defined. The knowledge accumulated on the progression of HCV to date is important, however. It is now abundantly clear that the progression of disease is generally slow, and the development of cirrhosis and its complications is a possibility, not a probability as hitherto thought. Predicting the outcome remains a quandary for clinicians. Ultimately it will be possible to define the natural history of hepatitis C infection through a combination of research in the fields of virology, immunology, and molecular biology and by monitoring the biochemical and histologic progress of the disease. Only then will it be possible to intervene appropriately and develop new therapies to prevent the progression to cirrhosis and hepatocellular carcinoma.

Influence of HLA-DR phenotype on the risk of hepatitis C virus-associated mixed cryoglobulinemia

OBJECTIVE

Circumstances predisposing hepatitis C virus (HCV)-infected patients to develop mixed cryoglobulinemia (MC), which may manifest as a small-vessel systemic vasculitis (MC vasculitis), remain unclear. Previous studies have failed to demonstrate a clear role of either viral factors (genotype, viral load) or host factors (lymphocytes or immunoglobulin subsets). This study was undertaken to examine a possible role of HLA class II alleles in HCV-associated MC.

METHODS

One hundred fifty-eight HCV-infected patients, of whom 76 had MC (56 with type II MC and 20 with type III MC) and 82 did not have MC, were studied prospectively. MC vasculitis was noted in 35 HCV-infected patients with type II IgMkappa-containing cryoglobulins. HLA-DRB1 and HLA-DQB1 polymorphism was analyzed by hybridization using allele-specific oligonucleotides, after gene amplification. The odds ratio (OR) was calculated with Woolf's method. Then, using multivariate analysis, demographic, biologic, immunologic, virologic, and liver histologic factors associated with the presence of MC and MC vasculitis were investigated.

RESULTS

HLA-DR11 was significantly more frequent in patients with type II MC than in those without MC (41.1% versus 17.1%; OR 3.4, corrected P [Pcorr] = 0.017), regardless of the presence of vasculitis accompanying the MC (37.1% of those with MC vasculitis, 34.1% of those with MC but no vasculitis). HLA-DR7 was less frequent in HCV-infected patients with MC than in those without MC (13.2% versus 30.5%; OR 0.34, P = 0.012, Pcorr not significant), with a particularly lower frequency in those with type II MC and those with MC vasculitis (12.5% and 8.6%, respectively). There was no significant difference in HLA-DQB1 distribution between the different patient groups. By univariate and multivariate analysis, HLA-DR11 was the only positive predictive factor, besides female sex and advanced age, for the presence of MC and HCV-associated MC vasculitis (OR 2.58).

CONCLUSION

Our results indicate that the presence of the DR11 phenotype is associated with a significantly increased risk for the development of type II MC in patients with chronic HCV infection. In contrast, HLA-DR7 appears to protect against the production of type II MC. These results suggest that the host's immune response genes may play a role in the pathogenesis of HCV-associated MC.

Risk factors of hepatitis C virus-related liver cirrhosis in young adults: positive family history of liver disease and transporter associated with antigen processing 2(TAP2)*0201 Allele

The aim of this study was to clinically characterize young patients with hepatitis-C-related cirrhosis. We compared 27 patients with liver cirrhosis (Group LC) who were anti-HCV positive, aged 40 years or less at the time of diagnosis, with 323 consecutive patients with HCV-related chronic hepatitis (Group CH) matched for age and gender. Furthermore, Group LC was divided into two arbitrary groups (29-35 years, n = 8 /36-40 years, n = 19), based on the age of patients at the time of diagnosis of liver cirrhosis. Patients' characteristics and family history were investigated, and the frequency of transporter associated with antigen processing 2 (TAP2) was determined. A family history of liver disease was present in 40.7% of Group LC but in 18.0% of Group CH (P < 0.05). The younger the age of diagnosis of cirrhosis in Group LC, the higher the frequency of a positive family history (29-35 years, 87.5%; 36-40 years, 21.1%, P < 0.05). The frequency of TAP2*0201 was significantly higher in young adult patients with HCV-related liver cirrhosis than in HCV carriers with normal ALT (P < 0.05), and tended to be higher than in uninfected normal subjects (P = 0.05). The cumulative survival rate of cirrhosis patients with family history of liver diseases was significantly lower than that of cirrhosis patients without such history (P < 0.05). Our findings suggest that a positive family history of liver disease and TAP2*0201 polymorphism may be risk factors for HCV-related liver cirrhosis in young adults.

Low frequency of HLA-DRB1*11 in hepatitis C virus induced end stage liver disease

Hepatitis C virus (HCV) infection becomes chronic in more than 70% of patients, leading to end stage liver disease in about 20-30% of these patients. Apart from the virus itself, host factors that modulate the immune response are likely to be involved in determining the outcome of HCV infection. Studies on the association of human leucocyte antigens (HLAs) and HCV infection have shown inconsistent results. Selection of patient subgroups may be crucial. However, any association relevant to HCV disease progression will become evident, especially in those patients with end stage liver disease. Therefore, we analysed the phenotype frequencies of HLA antigens in two groups of 69 and 39 patients with HCV induced liver cirrhosis who had received a transplant or were awaiting liver transplantation. The first group was typed serologically and compared with 331 blood and liver donors. The second group, prospectively HLA typed by a polymerase chain reaction-sequence specific oligonucleotide (PCR-SSO) procedure for HLA-DRB and DQB alleles, was compared with another 170 PCR-SSO typed and randomly selected blood donors. Decreased frequencies for HLA-DR5 and HLA-DQ3 were found in one group of patients with HCV induced liver cirrhosis compared with the control groups. In the second analysis comparing 39 patients with end stage liver cirrhosis with blood donors, we confirmed the significant decrease in HLA-DRB1*11 and HLA-DQB1*03, which corresponded to serological HLA-DR5 and HLA-DQ3 antigens, respectively. Our results show that the presence of HLA-DRB1*11 and HLA-DQB1*03 alleles is associated with a reduced risk for the development of HCV induced end stage liver disease.

Viral, host and interferon-related factors modulating the effect of interferon therapy for hepatitis C virus infection

The estimated prevalence of hepatitis C virus infection in the US is approximately 1.8%. Although interferon monotherapy and combination therapy of interferon with ribavirin represent mainstay for treating HCV infection, the rate of sustained virologic response remains suboptimal. The growing evidence suggested that the clinical sequence and treatment response of chronic hepatitis C are determined by a dynamic, complex tripartite relationship among HCV infection, the host immune response, and the effect of different interferon regimens. The treatment response is associated with various viral factors including the pretreatment viral level, dynamic change of viral level during treatment, viral genotype quasispecies and nucleotide mutation in nonstructural protein 5A of hepatitis C virus. Host factors that may affect treatment response include age, gender, race, HLA alleles and the host immune responses. Interferon regimens, including type, dose, frequency and duration of treatment and combination of interferon with other anti-HCV agents also alter the therapeutic response. Understanding these complicated interaction may provide better insights into the mechanism(s) of interferon response, leading to more effective clinical application of interferon therapy.

The MHC is a major determinant of viral status, but not fibrotic stage, in individuals infected with hepatitis C

BACKGROUND & AIMS

In hepatitis C infection, several studies have examined the role of the major histocompatibility complex (MHC) in determining outcome, with variable results. To clarify the importance of MHC, we examined class II DR and DQ antigens in a homogenous cohort of women exposed to hepatitis C genotype 1b from a single inoculum.

METHODS

Of 243 participants, 95 had spontaneous viral clearance and 148 are chronically infected. The frequencies of HLA class II DR and DQ antigens were compared between the 2 groups and between liver biopsy findings of 145 chronically infected subjects.

RESULTS

DRB1*0101 and DQB1*0501 alleles were more frequent in subjects who sustained viral clearance than in chronically infected subjects (32.3% and 36.8% vs. 8.8% and 14.2%, respectively; P = 0.002). DRB1*03011 and DQB1*0201 occurred more frequently in chronically infected subjects than in those who cleared the virus (41.5% and 42.6% vs. 16.7% and 15.8%, respectively; P = 0.001). Both DRB1*03011 and DQB1*0201 were significantly less frequent in those with higher inflammatory scores on liver biopsy.

CONCLUSIONS

We show that in a homogenous cohort of women infected with the same hepatitis C virus, several HLA antigens are associated with either viral clearance or persistence. This suggests a strong role for host immunogenetic factors in determining outcome in hepatitis C infection.

Influence of immunogenetic background on the outcome of recurrent hepatitis C after liver transplantation

In immunocompetent patients, specific human leukocyte antigen (HLA) class II alleles have been associated with the severity of hepatitis C virus (HCV)-related disease, in particular, HLA-DRB1*11 has been found to exert a protective effect. The authors have analyzed the role of HLA class I and II alleles in determining the frequency, timing, and progression of histologically proven recurrent hepatitis C in 89 patients who underwent a liver transplant for HCV-related cirrhosis. In addition, the influence of HLA mismatch between donor and recipient, HCV genotype, and use of steroid pulses was also evaluated. Median patient follow up was 35 months (range 4-119). HLA-DRB1 typing was performed by genomic analysis in all cases. Liver biopsies were obtained routinely and at least at yearly intervals. Histologically proven recurrent hepatitis was observed in 46 patients (52%), 10 patients progressing to stage 5-6 fibrosis in most cases within 2 years after transplant. By univariate analysis, 3 variables, HLA-B14, HLA-DRB1*04, and HLA-DRB1 donor/recipient mismatch, showed a significant effect on time to recurrent hepatitis C disease. These parameters were included in a multivariate regression model along with HCV genotype, treatment with steroid pulses and DRB1*11. HLA-B14, HLA-DRB1*04, and HLA-DRB1 donor/recipient mismatch were confirmed to provide a significant and independent contribution to the risk of hepatitic disease recurrence. As for the severity of the disease, none of the 10 patients with stage 5-6 hepatitis carried the HLA-DRB1*11 allele, in line with what was observed in nontransplant subjects. Our results suggest that in posttransplant recurrent hepatitis C, immunogenetic factors are relevant in determining HCV infection outcome.

Viral clearance in hepatitis C (1b) infection: relationship with human leukocyte antigen class II in a homogeneous population

The aim of this study was to investigate the possibility of a significant relationship between human leukocyte antigen (HLA) class II and the clearance of hepatitis C virus (HCV). The study group consisted of 156 Irish women who iatrogenically received HCV 1b-contaminated Anti-D immunoglobulin between May 1977 and November 1978. Thus, the study population was homogeneous in terms of gender, source of infection, and ethnicity. On Screening in 1994, all individuals were anti-HCV antibody positive by recombinant immunoblot assay, while 46% (n = 72) of the group were HCV-positive by reverse transcriptase-polymerase chain reaction (RT-PCR). HLA DRB1 and DQB1 status was molecularly defined by high resolution reverse line probe hybridization methodology. Clearance of HCV 1b was found to be associated with DRB1*01. However, this association was lost after Bonferroni correction for multiple comparisons. Extended haplotype analysis between specific DRB1 and DQB1 allelic combinations identified a significant reduction in the frequency of DQB1*0501 in the presence of DRB1*0701 in the persistently infected individuals in the study group (P <.05). No associations with either viral clearance or persistence were found at the DQB1 locus. Our results suggest that HLA DRB1*01 appears to contribute to the spontaneous resolution of a primary HCV infection in the Irish population. The presence of DRB1*0701 in the absence of DQB1*0501 possibly reflects an influence of this allele in persistence of HCV infection. Defined and homogeneous patient populations offer the best opportunity to illuminate previously disguised immunogenetic factors important in the clearance of HCV 1b.