Glycine-valine dimorphism at the 86th amino acid of HLA-DRB1 influenced the prognosis of postschistosomal hepatic fibrosis

Cellular Mechanisms of Liver Fibrosis

The liver is a central organ in the human body, coordinating several key metabolic roles. The structure of the liver which consists of the distinctive arrangement of hepatocytes, hepatic sinusoids, the hepatic artery, portal vein and the central vein, is critical for its function. Due to its unique position in the human body, the liver interacts with components of circulation targeted for the rest of the body and in the process, it is exposed to a vast array of external agents such as dietary metabolites and compounds absorbed through the intestine, including alcohol and drugs, as well as pathogens. Some of these agents may result in injury to the cellular components of liver leading to the activation of the natural wound healing response of the body or fibrogenesis. Long-term injury to liver cells and consistent activation of the fibrogenic response can lead to liver fibrosis such as that seen in chronic alcoholics or clinically obese individuals. Unidentified fibrosis can evolve into more severe consequences over a period of time such as cirrhosis and hepatocellular carcinoma. It is well recognized now that in addition to external agents, genetic predisposition also plays a role in the development of liver fibrosis. An improved understanding of the cellular pathways of fibrosis can illuminate our understanding of this process, and uncover potential therapeutic targets. Here we summarized recent aspects in the understanding of relevant pathways, cellular and molecular drivers of hepatic fibrosis and discuss how this knowledge impact the therapy of respective disease.

Genetic algorithms identify individuals with high risk of severe liver disease caused by schistosomes

Schistosomes induce severe hepatic disease, which is fatal in 2-10% of cases, mortality being higher in cases of co-infection with HBV or HCV. Hepatic disease occurs as a consequence of the chronic inflammation caused by schistosome eggs trapped in liver sinusoids. In certain individuals, the repair process leads to a massive accumulation of fibrosis in the periportal spaces. We and others have shown that genetic variants play a crucial role in disease progression from mild to severe fibrosis and explain why hepatic fibrosis progresses rapidly in certain subjects only. We will review here published findings concerning the strategies that have been used in the analysis of hepatic fibrosis in schistosome-infected individuals, the genetic variants that have associated with fibrosis, and variants in new pathways crucial for fibrosis progression. Together, these studies show that the development of fibrosis is under the tight genetic control of various common variants with moderate effects. This polygenic control has made it possible to develop models that identify schistosome-infected individual at risk of severe hepatic disease. We discuss the performances and limitations of these models.

Host Regulators of Liver Fibrosis During Human Schistosomiasis

Liver fibrosis is a wound-healing process purposely aimed at restoring organ integrity after severe injury caused by autoimmune reactions, mechanical stress or infections. The uncontrolled solicitation of this process is pathogenic and a pathognomonic feature of diseases like hepatosplenic schistosomiasis where exacerbated liver fibrosis is centrally positioned among the drivers of the disease morbidity and mortality. Intriguingly, however, liver fibrosis occurs and progresses dissimilarly in schistosomiasis-diseased individuals with the same egg burden and biosocial features including age, duration of residence in the endemic site and gender. This suggests that parasite-independent and currently poorly defined host intrinsic factors might play a defining role in the regulation of liver fibrosis, the hallmark of morbidity, during schistosomiasis. In this review, we therefore provide a comprehensive overview of all known host candidate regulators of liver fibrosis reported in the context of human schistosomiasis.

Immunoproteomics Identification of Major IgE and IgG4 Reactive Schistosoma japonicum Adult Worm Antigens Using Chronically Infected Human Plasma

Immunoepidemiological studies from endemic areas have revealed age-dependent resistance correlation with increased level of IgE and decreased level of IgG4 antibodies in responses to schistosomes' soluble worm antigen. However, there have been limited studies on analyses of major antigens that provoke IgE and IgG4 immune response during chronic stage of schistosomiasis. In this study, for the first time, immunoproteomics approach has been applied to identify S. japonicum worm antigens in liquid fractions that are recognized by IgE and IgG4 antibody using plasma from chronically infected population. ProteomeLabPF 2D fractionated 1-D and 2-D fractions of SWA antigens were screened using pooled high IgE/IgG4 reactive plasma samples by dot-blot technique. In 1-D fractions, IgE isotype was detected by fewer antigenic fractions (43.2%). The most recognized isotype was IgG3 (79.5%) followed by IgG1 (75.0%) and IgG4 (61.4%). Liquid chromatography MS/MS protein sequencing of reactive 2-D fractions revealed 18 proteins that were identified, characterized and gene ontology categories determined. 2-D fractions containing proteins such as zinc finger, RanBP2-type, domain-containing protein were strongly recognized by IgE and moderately by IgG4 whereas fractions containing proteins such as ubiquitin-conjugating enzyme and cytosolic II 5'-nucleotidase strongly recognizing by IgG subclasses (IgG1, IgG3 and IgG4) but not IgE. By this study, a simple and reproducible proteomic method has been established to identify major immunoreactive S. japonicum antigens. It is anticipated that this will stimulate further research on the immunogenicity and protective potential of proteins identified as well as discovery of novel compounds that have therapeutic importance.

Association of HLA and post-schistosomal hepatic disorder: a systematic review and meta-analysis

Several human genetic variants, HLA antigens and alleles are reportedly linked to post-schistosomal hepatic disorder (PSHD), but the results from these reports are highly inconclusive. In order to estimate overall associations between human genetic variants, HLA antigens, HLA alleles and PSHD, we systematically reviewed and performed a meta-analysis of relevant studies in both post-schistosomal hepatic disorder and post-schistosomal non-hepatic disorder patients. PubMed, Scopus, Google Scholar, The HuGE Published Literature database, Cochrane Library, and manual search of reference lists of articles published before July 2009 were used to retrieve relevant studies. Two reviewers independently selected articles and extracted data on study characteristics and data regarding the association between genetic variants, HLA antigens, HLA alleles and PSHD in the form of 2×2 tables. A meta-analysis using fixed-effects or random-effects models to pooled odds ratios (OR) with corresponding 95% confidence intervals were calculated only if more than one study had investigated particular variation. We found 17 articles that met our eligibility criteria. Schistosoma mansoni and Schistosoma japonicum were reported as the species causing PSHD. Since human genetic variants were only investigated in one study, these markers were not assessed by meta-analysis. Thus, only HLA-genes (a total of 66 HLA markers) were conducted in the meta-analysis. Our meta-analysis showed that human leucocyte antigens HLA-DQB1*0201 (OR=2.64, P=0.018), DQB1*0303 (OR=1.93, P=0.008), and DRB1*0901 (OR=2.14, P=0.002) alleles and HLA-A1 (OR=5.10, P=0.001), A2 (OR=2.17, P=0.005), B5 (OR=4.63, P=0.001), B8 (OR=2.99, P=0.02), and B12 (OR=5.49, P=0.005) serotypes enhanced susceptibility to PSHD, whereas HLA-DQA1*0501 (OR=0.29, P≤0.001) and DQB1*0301 (OR=0.58, P=0.007) were protective factors against the disease. We further suggested that the DRB1*0901-DQB1*0201, DRB1*0901-DQB1*0303 and A1-B8 haplotypes enhanced susceptibility to PSHD, whereas DQA1*0501-DQB1*0301 linkage decreased the risk of PSHD. The result improved our understanding of the association between the HLA loci and PSHD with regard to pathogenic or protective T-cells and provided novel evidence that HLA alleles may influence disease severity.

Tissue inhibitor of matrix-metalloprotease-1 predicts risk of hepatic fibrosis in human Schistosoma japonicum infection

BACKGROUND

Schistosomes infect 200 million individuals annually and cause significant hepatic fibrosis in up to 20%. Little is known regarding the mechanisms of schistosome-associated hepatic fibrosis in humans, and few biomarkers for risk of fibrosis have been identified.

METHODS

We treated 611 Schistosoma japonicum-infected Filipinos with praziquantel (PZQ) and performed ultrasound to quantify hepatic fibrosis at baseline and 12 months after PZQ treatment. We developed a multiplexed assay (FibroPlex) that quantifies predictors and effect modifiers of fibrosis. We measured FibroPlex analytes produced by peripheral blood mononuclear cells stimulated with schistosome egg antigen 4 weeks after PZQ treatment and related these levels to risk of fibrosis 1 year after PZQ treatment.

RESULTS

After adjusting for potential confounders, including baseline grade of fibrosis, individuals with detectable tissue inhibitor of matrix-metalloprotease-1 (TIMP-1) had a 3.5-fold greater risk of fibrosis 1 year after PZQ treatment, compared with individuals with undetectable levels (odds ratio, 3.48; 95% confidence interval, 1.41-8.43; P = .007).

DISCUSSION

Because TIMP-1 inhibits most matrix metalloproteases, which are responsible for collagen degradation, these data suggest that schistosome-associated hepatic fibrosis results, in part, from excessive inhibition of collagen remodeling. These data further suggest that TIMP-1 is a promising biomarker for assessing risk of hepatic fibrosis in schistosomiasis and, potentially, other infectious and noninfectious causes of liver disease.

HLA class II alleles, genotypes, haplotypes, and amino acids in primary biliary cirrhosis: a large-scale study

Twin and family studies suggest there is a significant genetic component to primary biliary cirrhosis (PBC). However, the inability to replicate reported associations has been a recurring problem, with the only consistently reported genetic association that between PBC and HLA-DRB1*0801. However, recently even this has been questioned, and a number of novel associations have also been reported. We reinvestigated HLA class II DRB1, DQA1, and DQB1 alleles and haplotypes in a total of 492 well-characterized PBC patients, 412 from the United Kingdom and an additional 80 patients from northern Italy. There was a clear and significant association with HLA-DRB1*0801 in both groups of patients compared to population-specific healthy controls (12% versus 4% in the UK patients, P=.00087, OR=3.05; and 18% versus 6% in the Italian patients, P=.021, OR=3.15). There were also significant protective associations with DRB1*11 in the Italian patients (28% versus 47%, P=.0071, OR=0.42), but not in the UK patients (8% versus 8%) and a protective association with DRB1*13 in both series (14% versus 20%, P=.042, OR=0.65 in the UK patients; and 10% versus 31%, P=.00092, OR=0.25 in the Italian patients). In conclusion, a complex relationship exists between HLA and PBC, and some genetic associations may be population specific.

Immunogenetic analysis of post-schistosomal liver fibrosis

Schistosomiasis is a major endemic parasitic disease in the world. In China, we have identified two major genes related to the severity of liver fibrosis, one an HLA class II gene, and the other the IL-13 gene. The frequency of the HLA-DRB5*0101 allele and that of the IL-13 promoter A/A (IL-13P- A/A) genotype were elevated in fibrotic patients, although the two genes are located on different chromosomes, chromosomes 6p and 5q, respectively. Subjects with both genotypes had odds ratios (OR=24.5) much higher than the sum of the ratios for each individual genotype (OR=5.1, 95% confidence interval 1.3-24.7 for HLA-DRB5*0101, OR=3.1 95% CI 1.5-6.5 for IL-13P- A/A). Although we have not yet characterized the functional difference between HLA-DRB5*0101 and other alleles, peripheral blood mononuclear cells from IL-13PA/A donors produced much higher amount of mRNA than IL-13PA/B 24 h after the stimulation with PHA. Those findings strongly suggest that the pathogenic Th2 response directly influences the prognosis of post-schistosomal liver fibrosis.

Genetic factors associated with development of cerebral malaria and fibrotic schistosomiasis

Collaborative studies have identified some genetic factors contributing to the development of severe forms of malaria and schistosomiasis. In Thailand, the TNF-alpha 5'-flanking region shows biallelic polymorphic sites at nucleotides -238, -308, -857, -863, and -1031, and seven alleles have been identified in patients from Myanmar. We found that the TNF promoter (TNFP)-D allele was significantly associated with cerebral malaria in populations from Karen (P < 0.0001, OR = 124.86) and ethnic Burma (P < 0.0001, OR = 34.50). In China, we have identified two major genes related to the severity of liver fibrosis, one an HLA class II gene, and the other the IL-13 gene. The frequency of the HLA-DRB5*0101 allele and that of the IL-13 promoter A/A (IL-13P- A/A) genotype were elevated in fibrotic patients, although the two genes are located on different chromosomes, chromosomes 6p and 5q, respectively. Subjects with both genotypes had odds ratios (OR = 24.5) much higher than the sum of the ratios for each individual genotype (OR = 5.1, 95% Confidence Interval 1.3-24.7 for HLA-DRB5*0101, OR = 3.1 95% CI 1.5 - 6.5 for IL-13P- A/A). That the effects of the two susceptibility markers are synergistic rather than additive, strongly suggests that the pathogenic Th2 response directly influences the prognosis of post-schistosomal liver fibrosis.

HLA class II antigens positively and negatively associated with hepatosplenic schistosomiasis in a Chinese population

To identify possible associations between host genetic factors and the onset of liver fibrosis following Schistosoma japonicum infection, the major histocompatibility class II alleles of 84 individuals living on an island (Jishan) endemic for schistosomiasis japonica in the Poyang Lake Region of Southern China were determined. Forty patients exhibiting advanced schistosomiasis, characterised by extensive liver fibrosis, and 44 age and sex-matched control subjects were assessed for the class II haplotypes HLA-DRB1 and HLA-DQB1. Two HLA-DRB1 alleles, HLA-DRB1*0901 (P=0.012) and *1302 (P=0.039), and two HLA-DQB1 alleles, HLA-DQB1*0303 (P=0.012) and *0609 (P=0.037), were found to be significantly associated with susceptibility to fibrosis. These associated DRB1 and DQB1 alleles are in very strong linkage disequilibrium, with DRB1*0901-DQB1*0303 and DRB1*1302-DQB1*0609 found as common haplotypes in this population. In contrast, the alleles HLA-DRB1*1501 (P=0.025) and HLA-DQB1*0601 (P=0.022) were found to be associated with resistance to hepatosplenic disease. Moreover, the alleles DQB1*0303 and DRB1*0901 did not increase susceptibility in the presence of DQB1*0601, indicating that DQB1*0601 is dominant over DQB1*0303 and DRB1*0901. The study has thus identified both positive and negative associations between HLA class II alleles and the risk of individuals developing moderate to severe liver fibrosis following schistosome infection.

Schistosomiasis in the People's Republic of China: prospects and challenges for the 21st century

Schistosomiasis japonica is a serious communicable disease and a major disease risk for more than 30 million people living in the tropical and subtropical zones of China. Infection remains a major public health concern despite 45 years of intensive control efforts. It is estimated that 865,000 people and 100,250 bovines are today infected in the provinces where the disease is endemic, and its transmission continues. Unlike the other schistosome species known to infect humans, the oriental schistosome, Schistosoma japonicum, is a true zoonotic organism, with a range of mammalian reservoirs, making control efforts extremely difficult. Clinical features of schistosomiasis range from fever, headache, and lethargy to severe fibro-obstructive pathology leading to portal hypertension, ascites, and hepatosplenomegaly, which can cause premature death. Infected children are stunted and have cognitive defects impairing memory and learning ability. Current control programs are heavily based on community chemotherapy with a single dose of the drug praziquantel, but vaccines (for use in bovines and humans) in combination with other control strategies are needed to make elimination of the disease possible. In this article, we provide an overview of the biology, epidemiology, clinical features, and prospects for control of oriental schistosomiasis in the People's Republic of China.

Is there immunity to Schistosoma japonicum?

The Oriental schistosome, Schistosoma japonicum, unlike the other two major schistosomes that infect humans (S. mansoni and S. haematobium), is a zoonotic species. The transmission dynamics and the potential effects of host-related regulatory factors, including immunity, are likely to be distinct for this parasite. Here, Allen Ross and collaborators from Australia, China and the Philippines discuss recently published and established epidemiological and laboratory data bearing on anti-infection immunity to Asian schistosomiasis, and contrast these findings with the emerging picture of development of anti-infection immunity against the African schistosomes. Implications for vaccines and other control strategies for schistosomiasis japonica are also discussed.

Association of hypersensitivity to the nematode Anisakis simplex with HLA class II DRB1*1502-DQB1*0601 haplotype

Anisakiasis as well as allergic and anaphylactoid reactions to Anisakis simplex antigens are recently identified clinical entities. They are relatively frequent in countries with habitual raw food consumption, often in the form of large amounts of fish and sea food products. In this communication the relationship between HLA class II alleles and the IgE-specific immune response to A. simplex allergen was studied in a defined population in Northern Spain. Individuals with immediate-type Anisakis hypersensitivity and healthy controls were examined for HLA-DRB1, DQB1 and DQA1 alleles by sequence-specific oligonucleotide probe typing. Analysis of the HLA data among patients revealed increased phenotypic frequencies for DRB1*1502 and DRB1*0404 compared to healthy controls (p < 1 x 10(-7) and < 0.01, respectively). Analysis of haplotypic frequencies showed that the DRB1*1502-DQB1*0601 haplotype is significantly higher in patients with Anisakis hypersensitivity in comparison with the control population from the same region (p < 4 x 10(-8)). The data suggest that this haplotype can be considered to be a susceptibility factor for hypersensitivity to A. simplex antigens.

HLA-DR-DQ alleles and HLA-DP alleles are independently associated with susceptibility to different stages of post-schistosomal hepatic fibrosis in the Chinese population

Abstract: Evaluation of human leukocyte antigen (HLA) class I and class II genes was performed on patients from China with Schistosomiasis japonica. Patients were categorized as grade 0 (n=44), grade I (n=81), grade II (n=99), or grade III (n=6) based on increasing severity of hepatic fibrosis due to repeated Schistosoma japonicum infections. These results show that the HLA-DRB1*1101-DQA1*0501-DQB1*0301 (Pc<0.02) and HLA-DRB1*1501-DRB5*0101 (Pc<0.02) haplotypes are associated with protection and susceptibility to grade I fibrosis, respectively, and that the HLA-DPA1*0103 -DPB1*0201 haplotype (Pc<0.02) is associated with protection from both grade II and III severe fibrosis. There was no association between HLA-B DNA haplotypes and the disease. These findings indicate that the HLA-class II molecules play a role in preventing or promoting fibrotic liver change after deposition with Schistosome eggs. Moreover, a tendency was observed within the HLA class II genes for the HLA-DR-DQ alleles to be associated with protection against early changes in liver fibrosis, whereas HLA-DP alleles were associated with protection from the late phase of fibrosis or severe hepatosplenic schistosomiasis.