Polymorphism of OAS-1 determines liver fibrosis progression in hepatitis C by reduced ability to inhibit viral replication

Mapping Viral Susceptibility Loci in Mice

Genetic alleles that contribute to enhanced susceptibility or resistance to viral infections and virally induced diseases have often been first identified in mice before humans due to the significant advantages of the murine system for genetic studies. Herein we review multiple discoveries that have revealed significant insights into virus-host interactions, all made using genetic mapping tools in mice. Factors that have been identified include innate and adaptive immunity genes that contribute to host defense against pathogenic viruses such as herpes viruses, flaviviruses, retroviruses, and coronaviruses. Understanding the genetic mechanisms that affect infectious disease outcomes will aid the development of personalized treatment and preventive strategies for pathogenic infections.

[OAS1 gene polymorphism is associated with central nervous system involvement in children with enterovirus 71 infection]

OBJECTIVE

We investigated the association between OAS1 gene polymorphism and susceptibility to central nervous system (CNS) involvement of enterovirus (EV)71 infection.

METHODS

This case-control study was conducted among 180 children with EV71 infection, including 72 with mild infections without any complications and 108 with severe infections and CNS involvement; 201 children undergoing routine physical examination served as the healthy controls. For all the participants, the single nucleotide polymorphisms (SNPs) at OAS1 rs2660 and rs1131454 were analyzed using SNPscan multiple SNP typing methods.

RESULTS

No significant differences were found between the case and control groups in genotype or allele distributions of rs2660 and rs1131454. OAS1 rs2660 polymorphism was significantly different between the children with CNS involvement and those with mild EV71 infection, and the genotype AG frequency was higher and the genotype GG frequency was lower in children with CNS involvement. No significant difference was found in the distribution of genotypes or alleles of rs1131454 between the children with CNS involvement and those with mild EV71 infection.

CONCLUSIONS

OAS1 gene rs2660 and rs1131454 SNPs are not associated with the susceptibility to or CNS involvement of EV71 infection, but OAS1 rs2660 SNPs are significantly correlated with the susceptibility to CNS involvement in EV71 infection. Children carrying OAS1 rs2660 AG genotype are more likely to have CNS involvement after EV71 infection.

Genomic variations in the 2'-5' oligoadenylate synthetase 1 (OAS1) gene in zebu cattle and its crossbreds of Indian origin

In the antiviral host defense mechanisms, the role of mammalian OAS/RNASEL pathway is very significant. These enzymes are interferon-inducible and activated by binding to double-stranded RNA (dsRNA) which are present in virus infected cells. The OAS proteins functions through its receptor, the 2-5Adependent ribonuclease (RNaseL) and activated OAS-RNaseL system degrades viral and cellular RNA and subsequently inhibits protein synthesis. Polymorphisms in the human and equine OAS gene cluster have been previously utilized for casecontrol analysis of virus-induced disease. But no polymorphisms have yet been identified in the bovine OAS1 genes for use in similar case-control studies. The promoter and coding regions of the OAS1 gene was amplified and screened for polymorphisms by PCR-SSCP and sequencing in Sahiwal and Frieswal animals. Two SNPs have been identified in the promoter region of OAS1 gene, which have predicted to create/delete sites for transcription factors. Specific amplification of the exonic regions of the OAS1 gene have identified 26 SNPs and one dinucleotide repeats, among them 14 are mis-sense variants. These polymorphisms are the first to be reported in OAS1 gene and will facilitate future case-control studies of cattle susceptibility to infectious diseases.

Mx1, OAS1 and OAS2 polymorphisms are associated with the severity of liver disease in HIV/HCV-coinfected patients: A cross-sectional study

The mechanisms involved in the chronic hepatitis C progression are incompletely understood. The aim was to analyze the association between 2'5'oligoadenylate synthetase 1,2 and 3 (OAS1-3) and myxovirus resistance proteins 1 (Mx1) polymorphisms and severity of liver disease in human immunodeficiency virus (HIV)/hepatitis C virus (HCV) coinfected patients. We performed a cross-sectional study in 219 patients that underwent a liver biopsy. DNA genotyping for Mx1 (rs469390), OAS1 (rs2285934), OAS2 (rs1293762) and OAS3 (rs2010604) was performed by using GoldenGate assay. The outcome variables ion liver biopsy were: (i) significant fibrosis (F ≥ 2); (ii) moderate activity grade (A ≥ 2). Additive model of inheritance for genetic association test was used. The likelihood of having significant fibrosis (F ≥ 2) was lower in patients carrying OAS2 rs1293762 A allele [adjusted odds ratio (aOR) = 0.51; p = 0.040]. Besides, the likelihood of having moderate activity grade (A ≥ 2) was higher in patients carrying Mx1 rs464397 C allele (aOR = 1.63; p = 0.028) and Mx1 rs469390 G allele (aOR = 1.97; p = 0.005), while it was lower in patients carrying OAS1 rs2285934 A allele (aOR = 0.64; p = 0.039) and OAS2 rs1293762 A allele (aOR = 0.41; p = 0.009). In conclusion, Mx1 and OAS1-2 polymorphisms were associated with the severity of liver disease in HIV/HCV-coinfected patients, suggesting a significant role in the progression of hepatic fibrosis.

Cellular responses to HSV-1 infection are linked to specific types of alterations in the host transcriptome

Pathogen invasion triggers a number of cellular responses and alters the host transcriptome. Here we report that the type of changes to cellular transcriptome is related to the type of cellular functions affected by lytic infection of Herpes Simplex Virus type I in Human primary fibroblasts. Specifically, genes involved in stress responses and nuclear transport exhibited mostly changes in alternative polyadenylation (APA), cell cycle genes showed mostly alternative splicing (AS) changes, while genes in neurogenesis, rarely underwent these changes. Transcriptome wide, the infection resulted in 1,032 cases of AS, 161 incidences of APA, 1,827 events of isoform changes, and up regulation of 596 genes and down regulations of 61 genes compared to uninfected cells. Thus, these findings provided important and specific links between cellular responses to HSV-1 infection and the type of alterations to the host transcriptome, highlighting important roles of RNA processing in virus-host interactions.

A Modified Coupled Spectrophotometric Method to Detect 2-5 Oligoadenylate Synthetase Activity in Prostate Cell Lines

BACKGROUND

2'-5' oligoadenylate synthetases (OAS) are interferon inducible enzymes that polymerizes ATP to 2'-5'-linked oligomers of adenylate (2-5As). As part of the innate immune response, these enzymes are activated by viral double stranded RNA or mRNAs with significant double stranded structure. The 2-5As in turn activate RNaseL that degrade single stranded RNAs. Three distinct forms of OAS exist in human cells (OAS1, 2 and 3) with each form having multiple spliced variants. The OAS enzymes and their spliced variants have different enzyme activities. OAS enzymes also play a significant role in regulating multiple cellular processes such as proliferation and apoptosis. Moreover, Single nucleotide polymorphisms that alter OAS activity are also associated with viral infection, diabetes and cancer. Thus detection of OAS enzyme activity with a simple spectrophotometric method in cells will be important in clinical research.

RESULTS

Here we propose a modified coupled spectrophotometric assay to detect 2-5 oligoadenylate synthetase (OAS) enzyme activity in prostate cell lines as a model system. The OAS enzyme from prostate cancer cell lysates was purified using Polyinosinic: polycytidylic acid (poly I:C) bound activated sepharose beads. The activated OAS enzyme eluted from Sepharose beads showed expression of p46 isoform of OAS1, generally considered the most abundant OAS isoform in elutes from DU14 cell line but not in other prostate cell line. In this assay the phosphates generated by the OAS enzymatic reaction is coupled with conversion of the substrate 2-amino-6-mercapto-7-methylpurine ribonucleoside (methylthioguanosine, a guanosine analogue; MESG) to a purine base product, 2-amino-6-mercapto-7-methylpurine and ribose1-phosphate via a catalyst purine nucleoside phosphorylase (phosphorylase) using a commercially available pyrophosphate kit. The absorbance of the purine base product is measured at 360 nm. The higher levels of phosphates detected in DU145 cell line indicates more activity of OAS in this prostate cancer cell line.

CONCLUSION

The modified simple method detected OAS enzyme activity with sensitivity and specificity, which could help in detection of OAS enzymes avoiding the laborious and radioactive methods.

Impact of OAS1 Exon 7 rs10774671 Genetic Variation on Liver Fibrosis Progression in Egyptian HCV Genotype 4 Patients

The aim of this study was to assess the impact of genetic variants of oligoadenylate synthetase 1 (OAS1) single-nucleotide polymorphism (SNP) rs10774671 at the exon 7 splice acceptor site on liver fibrosis progression and hepatitis C virus (HCV) outcome in Egyptian HCV genotype 4 patients. In this study, 195 subjects were enrolled; 60 controls and 135 chronic HCV genotype 4 patients with different fibrosis grades. All subjects were genotyped for OAS1 SNP rs10774671 polymorphism by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. There was an increasing trend of liver fibrosis progression as 52.9% GG, 73.6% GA, and 83.3% AA genotypes were detected in late fibrosis patients (p = 0.025). The AA genotype was higher in the late fibrosis group than in the early fibrosis group (83.3% vs. 16.7%) (p = 0.001). The A allele was significantly affecting the liver fibrosis progression rate, more than the G allele (p = 0.001). The multivariate analysis showed that the OAS1 GA and AA genotypes were independent factors associated with liver progression (p = 0.009, odds ratio [OR] 3.467, 95% confidence interval [CI] 1.273-7.584). In addition, the A allele was associated with liver fibrosis progression (p = 0.014, OR 2.525, 95% CI 1.157-4.545). The polymorphism at OAS1 exon 7 rs3741981 might be a potential genetic marker and can be useful in the assessment of liver fibrosis progression and disease outcome in HCV-infected patients.

Identification of differential gene expression profile of HSCs subjected to pressurization by next-generation sequencing

AIM: To identify the gene expression profile of hepatic stellate cells (HSCs) subjected to pressurization by next-generation sequencing.

METHODS: Primary HSCs were isolated and cultured. After cultivation for 14 d, cells were subjected to a pressure of 10 MMHG (millimeters of mercury) for 1 h. Total RNA was then extracted and reverse transcribed into cDNA to screen differential genes between HSCs subjected to pressurization and non-treated HSCs using DEG-Seq.

RESULTS: A total of 979 differentially expressed genes were expressed in HSCs, of which 14 showed the most significant difference, including 10 up-regulated and 4 down-regulated genes. These genes were found to be related to anabolism, immune response, cell apoptosis, etc.

CONCLUSION: Differentially expressed genes could be identified in HSCs subjected to pressurization, indicating that HSCs respond to external pressure stimulation by regulating the expression of these genes.

IL28B minor allele is associated with a younger age of onset of hepatocellular carcinoma in patients with chronic hepatitis C virus infection

BACKGROUND

IL28B polymorphisms were shown to be associated with a response to peg-interferon-based treatment in chronic hepatitis C (CHC) and spontaneous clearance. However, little is known about how this polymorphism affects the course of CHC, including the development of hepatocellular carcinoma (HCC). We evaluated the influence of IL28B polymorphisms on hepatocarcinogenesis in CHC patients.

METHODS

We genotyped the rs8099917 single-nucleotide polymorphism in 351 hepatitis C-associated HCC patients without history of IFN-based treatment, and correlated the age at onset of HCC in patients with each genotype.

RESULTS

Frequencies of TT, TG, and GG genotypes were 74.3 % (261/351), 24.8 % (87/351), and 0.9 % (3/351), respectively. The mean ages at onset of HCC for TT, TG, and GG genotypes were 69.9, 67.5 and 66.8, respectively. In multivariate analysis, IL28B minor allele (TG and GG genotypes) was an independent risk factor for younger age at onset of HCC (P = 0.02) in males (P < 0.001) with higher body mass index (BMI; P = 0.009). The IL28B minor allele was also associated with a lower probability of having aspartate aminotransferase-to-platelet ratio index (APRI) >1.5 (minor vs. major, 46.7 vs. 58.6 %; P = 0.01), lower AST (69.1 vs. 77.7 IU/L, P = 0.02), lower ALT (67.8 vs. 80.9 IU/L, P = 0.002), higher platelet count (12.8 vs. 11.2 × 10(4)/μL, P = 0.002), and higher prothrombin time (79.3 vs. 75.4 %, P = 0.002).

CONCLUSIONS

The IL28B minor allele was associated with lower inflammatory activity and less progressed fibrosis of the liver; however, it constituted a risk factor for younger-age onset of HCC in CHC patients.

Impact of IL28B genetic variation on HCV-induced liver fibrosis, inflammation, and steatosis: a meta-analysis

BACKGROUND & AIMS

IL28B polymorphisms were shown to be strongly associated with the response to interferon therapy in chronic hepatitis C (CHC) and spontaneous viral clearance. However, little is known about how these polymorphisms affect the natural course of the disease. Thus, we conducted the present meta-analysis to assess the impact of IL28B polymorphisms on disease progression.

METHODS

A literature search was conducted using MEDLINE, EMBASE, and the Cochrane Library. Integrated odds ratios (OR) were calculated with a fixed-effects or random-effects model based on heterogeneity analyses.

RESULTS

We identified 28 studies that included 10,024 patients. The pooled results indicated that the rs12979860 genotype CC was significantly associated (vs. genotype CT/TT; OR, 1.122; 95%CI, 1.003-1.254; P = 0.044), and that the rs8099917 genotype TT tended to be (vs. genotype TG/GG; OR, 1.126; 95%CI, 0.988-1.284; P = 0.076) associated, with an increased possibility of severe fibrosis. Both rs12979860 CC (vs. CT/TT; OR, 1.288; 95%CI, 1.050-1.581; P = 0.015) and rs8099917 TT (vs. TG/GG; OR, 1.324; 95%CI, 1.110-1.579; P = 0.002) were significantly associated with a higher possibility of severe inflammation activity. Rs8099917 TT was also significantly associated with a lower possibility of severe steatosis (vs. TG/GG; OR, 0.580; 95%CI, 0.351-0.959; P = 0.034), whereas rs12979860 CC was not associated with hepatic steatosis (vs. CT/TT; OR, 1.062; 95%CI, 0.415-2.717; P = 0.901).

CONCLUSIONS

IL28B polymorphisms appeared to modify the natural course of disease in patients with CHC. Disease progression seems to be promoted in patients with the rs12979860 CC and rs8099917 TT genotypes.

Association between polymorphisms in OAS2 and CD209 genes and predisposition to chronic hepatitis C in Russian population

Chronic hepatitis C is a severe liver disease caused by positive-strand RNA virus. Previously, we reported an association between seven single nucleotide polymorphisms (SNPs) in four innate immunity genes (OAS2, OAS3, CD209, and TLR3) and human predisposition to tick-borne encephalitis, caused by a virus from the same Flaviviridae family, in a Russian population. Currently, genotype and allele frequencies for these SNPs were analyzed in 75 chronic hepatitis C patients and compared with the population control (269 Novosibirsk citizens). Data obtained suggest that the OAS2 rs1293762 and CD209 rs2287886 SNPs are associated with predisposition to chronic hepatitis C in Russian population.

microRNA control of interferons and interferon induced anti-viral activity

Interferons (IFNs) are cytokines that are spontaneously produced in response to virus infection. They act by binding to IFN-receptors (IFN-R), which trigger JAK/STAT cell signalling and the subsequent induction of hundreds of IFN-inducible genes, including both protein-coding and microRNA genes. IFN-induced genes then act synergistically to prevent virus replication and create an anti-viral state. miRNA are therefore integral to the innate response to virus infection and are important components of IFN-mediated biology. On the other hand viruses also encode miRNAs that in some cases interfere directly with the IFN response to infection. This review summarizes the important roles of miRNAs in virus infection acting both as IFN-stimulated anti-viral molecules and as critical regulators of IFNs and IFN-stimulated genes. It also highlights how recent knowledge in RNA editing influence miRNA control of virus infection.

A genome-wide association study of HCV-induced liver cirrhosis in the Japanese population identifies novel susceptibility loci at the MHC region

BACKGROUND & AIMS

We performed a genome-wide association study (GWAS) of hepatitis C virus (HCV)-induced liver cirrhosis (LC) to identify predictive biomarkers for the risk of LC in patients with chronic hepatitis C (CHC).

METHODS

A total of 682 HCV-induced LC cases and 1045 CHC patients of Japanese origin were genotyped by Illumina Human Hap 610-Quad bead Chip.

RESULTS

Eight SNPs which showed possible associations (p<1.0 × 10(-5)) at the GWAS stage were further genotyped using 936 LC cases and 3809 CHC patients. We found that two SNPs within the major histocompatibility complex (MHC) region on chromosome 6p21, rs910049 and rs3135363, were significantly associated with the progression from CHC to LC (pcombined=9.15 × 10(-11) and 1.45 × 10(-10), odds ratio (OR)=1.46 and 1.37, respectively). We also found that HLA-DQA1(*)0601 and HLA-DRB1(*)0405 were associated with the progression from CHC to LC (p=4.53 × 10(-4) and 1.54 × 10(-4) with OR=2.80 and 1.45, respectively). Multiple logistic regression analysis revealed that rs3135363, rs910049, and HLA-DQA1(*)0601 were independently associated with the risk of HCV-induced LC. In addition, individuals with four or more risk alleles for these three loci have a 2.83-fold higher risk for LC than those with no risk allele, indicating the cumulative effects of these variations.

CONCLUSIONS

Our findings elucidated the crucial roles of multiple genetic variations within the MHC region as prognostic/predictive biomarkers for CHC patients.

Genetic polymorphism in cyclooxygenase-2 promoter affects hepatic inflammation and fibrosis in patients with chronic hepatitis C

Cyclooxygenase (COX)-2 is involved in inflammation, anti-apoptosis and carcinogenesis. The -1195GG genotype of single nucleotide polymorphism (SNP) in COX-2 promoter was associated with low platelet counts in patients with chronic hepatitis C. Polymorphism of patatin-like phospholipase domain-containing protein 3 (PNPLA3) gene (rs738409 C>G) have been reported to be associated with cirrhosis, and the major genotype of SNPs near interleukin (IL)28B are related to viral clearance. The present study was designed to assess the contribution of these SNPs to disease progression in patients with chronic hepatitis C. The study enrolled 220 Japanese patients with chronic hepatitis C. Three SNPs, -1195 COX-2, PNPLA3 and IL28B (rs8099917), were genotyped in order to analyze their association with hepatic fibrosis and inflammation. The -1195GG genotype in COX-2 was associated with advanced fibrosis and higher levels of inflammation in the liver tissues. The major genotype of IL28B was also associated with advanced fibrosis, but the polymorphism of PNPLA3 was neither associated with fibrosis nor inflammation. Multivariate analysis showed that -1195GG in COX-2 is an independent factor associated with advanced fibrosis, while the major genotype of IL28B and HCV genotype 2 were other independent factors. In conclusion, the -1195GG genotype in COX-2 is a genetic marker for liver disease progression, while the PNPLA3 genotypes are not associated with disease progression in Japanese patients with chronic hepatitis C.

The interferon signaling pathway genes as biomarkers of hepatitis C virus disease progression and response to treatment

Hepatitis C virus is an ever-increasing worldwide health problem with over 350,000 individuals succumbing to hepatitis C virus-related liver diseases each year. The ability to determine the outcome of an acute-phase illness may be useful in terms of implementing treatment strategies; however, to date, the predictive associations in the literature have centered around candidate gene analysis. Much greater advancements have been made in describing biomarkers from the activation of the host innate immune response, such as the interferon system, for prediction of treatment outcome in chronic hepatitis C with the advent of genome-wide association studies. Recent times has seen a major breakthrough in the field with the description of the IL28B genotype as an independent association factor for pegylated IFN-α2b/ribavirin treatment response. The ability to couple this with other easily measured biomarkers such as the interferon-stimulated gene CXCL10, serum concentration may make this predictive marker set very useful in the clinical setting.

Evaluate the relationship between polymorphisms of OAS1 gene and susceptibility to chronic hepatitis C with high resolution melting analysis

The aim of this was to investigate the relationship between single-nucleotide polymorphisms (SNPs) in the OAS1 gene and the susceptibility to chronic hepatitis C virus (HCV) infection in a population from the Liaoning Province of China. High resolution melt (HRM)-PCR analysis was conducted to examine three OAS1 SNPs: rs2660 G/A, rs10774671 G/A, and rs3741981 G/A in 298 chronic HCV-infected patients and in 305 healthy controls and to identify a relationship between SNP genotype and susceptibility to chronic HCV infection using a case–control study design. These three OAS1 SNPs were in strong linkage disequilibrium (rs2660 vs. rs10774671: |D’|=1.000, r² =1.000; rs2660/rs10774671 vs. rs3741981: |D’|=0.938, r² =0.569). The frequency of AG + GG genotypes in both rs2660 and rs10774671 and the AA + AG genotype in rs3741981 was significantly higher among chronic HCV-infected patients than among control (P < 0.001); the A allele in all three SNPs was found more frequently in the chronic HCV-infected group than in the control group (rs2660 and rs10774671: P = 0.02; rs3741981: P < 0.001). Moreover, individuals carrying the A allele in these SNPs exhibited an increased risk for chronic HCV infection (rs2660 and rs10774671: OR = 1.356 [1.051–1.749]; rs3741981: 1.363 [1.085–1.712]). The haplotype created by the G allele at both rs2660 and rs10774671 and the A allele at rs3741981 increased the risk of chronic HCV infection by 3.394-fold (95 % CI 1.406–8.201). Our results identify OAS1 SNP rs2660, rs10774671, and rs3741981 as genetic risk factors for chronic HCV infection. Polymorphisms of the OAS1 gene might affect the susceptibility to chronic infection with HCV.

Hepatocellular carcinoma: towards personalized medicine

Over the past several years, the success of genome-wide association studies (GWAS) and pharmacogenomics has gradually begun to enable personalized medicine in some fields. In the field of liver diseases, host genetic factors are now very useful in clinical practice for predicting treatment outcome and adverse reactions for pegylated interferon plus ribavirin combination therapy against chronic hepatitis C virus (HCV) infection. Recently, three virus-related hepatocellular carcinoma (HCC) GWAS were reported from Asia. One study examined hepatitis B virus-related HCC in China, where hepatitis B is very prevalent, and the other two examined HCV-related HCC in Japan. We identified a common variant in the DEPDC5 locus associated with HCV-related HCC, and another group identified an association involving the MICA locus. In this review, we compare the results of these GWAS and earlier candidate gene studies. Further research is needed to determine the role of these single nucleotide polymorphisms on HCC risk, but identification of these markers could make it possible to assess the magnitude of the risk of cancer based on each patient's genetic background. Consideration of the genetic background of the patients will likely play a role in personalized medicine for HCC, and understanding the mechanism underlying the association could suggest novel promising therapeutic targets in the future.

Identification of a new susceptibility variant for multiple sclerosis in OAS1 by population genetics analysis

Contrasting results have been reported concerning the association of a splice-site polymorphism (rs10774671) in OAS1 with multiple sclerosis (MS). We analysed two OAS1 regions encompassing alternatively spliced exons. While the region carrying the splice-site variant is neutrally evolving, a signature of long-standing balancing selection was observed across an alternative exon 7. Analysis of variants in this exon identified an insertion/deletion polymorphism (rs11352835, A/−) that originates predicted products with distinct C termini. This variant is located along the major branch of the haplotype genealogy, suggesting that it may represent the selection target. A case/control study for MS indicated that rs11352835 is associated with disease susceptibility (for an allelic model with the deleted allele predisposing to MS, OR 1.27, 95% CI 1.072–1.513, p = 0.010). No association was found between rs10774671 and MS. As the two SNPs are in linkage disequilibrium in Europeans, the previously reported association between rs10774671 and MS susceptibility might be driven by rs11352835, possibly explaining the contrasting results previously observed for the splice-site polymorphism. Thus, we describe a novel susceptibility variant for MS in OAS1 and show that population genetic analyses can be instrumental to the identification of selection targets and, consequently, of functional polymorphisms with an effect on phenotypic traits.

Dysfunction of Immune Systems and Host Genetic Factors in Hepatitis C Virus Infection with Persistent Normal ALT

Patients with chronic hepatitis C (CHC) virus infection who have persistently normal alanine aminotransferase levels (PNALT) have mild inflammation and fibrosis in comparison to those with elevated ALT levels. The cellular immune responses to HCV are mainly responsible for viral clearance and the disease pathogenesis during infection. However, since the innate and adaptive immune systems are suppressed by various kinds of mechanisms in CHC patients, the immunopathogenesis of CHC patients with PNALT is still unclear. In this review, we summarize the representative reports about the immune suppression in CHC to better understand the immunopathogenesis of PNALT. Then, we summarize and speculate on the immunological aspects of PNALT including innate and adaptive immune systems and genetic polymorphisms of HLA and cytokines.

2'-5' oligoadenylate synthetase 1 polymorphism is associated with prostate cancer

BACKGROUND

The antiviral, proapoptotic, antiproliferative gene 2'-5' oligoadenylate synthetase (2-5OAS1) converts adenosine triphosphate into a series of 2'-5' oligoadenylates (2-5A). In turn, 2-5A activates latent ribonuclease (RNaseL), a candidate hereditary prostate cancer gene. OAS1 polymorphism (reference single nucleotide polymorphism [SNP] 2660 [rs2660]) has been associated with increased susceptibility to infections and various diseases. In general, the low-enzyme-activity adenine-adenine (AA) genotype promotes susceptibility, whereas the high-enzyme-activity guanosine-guanosine (GG) genotype confers protection. In this study, the authors investigated the association of this functional OAS1 polymorphism (rs2660) with prostate cancer.

METHODS

Sample size and power were calculated using a power calculation software program for case-control genetic association analyses. Genomic DNA samples from a control group (n = 140) and from a case group of patients with prostate cancer (n = 164) were used for genotyping SNPs rs2660, rs1131454, and rs34137742 in all samples. Statistical analyses were performed using a logistic regression model.

RESULTS

A significant association was observed between the rs2660 genotype (A/G) and prostate cancer. Genotype AA increased the risk, whereas genotype GG decreased the risk of prostate cancer. The GG genotype was not observed in the African American samples. The AA genotype also increased the risk of prostate cancer with age.

CONCLUSIONS

The OAS1 SNP rs2660 AA genotype was associated significantly with prostate cancer, whereas the GG genotype protected against prostate cancer. OAS1 rs2660 may be a prostate cancer susceptibility polymorphism, which is a significant observation, especially in a context of the OAS1-RNaseL pathway. Thus, a functional defect in OAS1 because of the rs2660 SNP not only can attenuate RNaseL function but also can alter cell growth and apoptosis independent of RNaseL.

Single nucleotide polymorphism at exon 7 splice acceptor site of OAS1 gene determines response of hepatitis C virus patients to interferon therapy

BACKGROUND AND AIM

Response to interferon therapy and disease progression in hepatitis C virus (HCV) infected patients differs among individuals, suggesting a possibility of a contribution of host genetic factors. 2'-5'-oligoadenylate synthetase 1 (OAS1), an important component of the innate immune system with a proven antiviral function, may therefore have a relationship with the response to interferon therapy and clinical course of HCV disease. Our aim was to determine the frequency of single nucleotide polymorphism (SNP) at exon 7 splice acceptor site (SAS) of the OAS1 gene in relation to the interferon response and status of HCV infection.

METHODS

A 203 bp fragment containing exon 7 SAS was amplified in 70 HCV chronic patients and 50 healthy controls. SNP was examined using restriction fragment length polymorphism (RFLP) genotyping method. Correlations of SNP genotypes with response to interferon and clinical status of patients were statistically analyzed.

RESULTS

There was an increasing trend of response from AA to AG to GG genotypes (P = 0.007). Genotype AA was associated with non-response to interferon and higher degree of liver fibrosis (P = 0.05). Multivariate analysis showed this SNP as independent and a significant determinant of the outcome of interferon therapy (odds ratio 4.913 [95% confidence interval 1.365-8.2], P = 0.006).

CONCLUSIONS

This is the first study to show a significant association between the functional SNP at exon 7 SAS of OAS1 gene and the viral response to interferon in chronic HCV patients. Patients with AA genotype were associated with progressive HCV disease and viral resistance to interferon therapy. This OAS SNP is a potential bio-marker to predict IFN response in chronic hepatitis C patients.

Danoprevir monotherapy decreases inflammatory markers in patients with chronic hepatitis C virus infection

Danoprevir is a potent and selective direct-acting antiviral agent that targets the protease activity of hepatitis C virus (HCV) NS3/4A. This agent results in a significant rapid decline in HCV RNA levels when it is used in monotherapy. The present study evaluated whether plasma concentrations of the inflammatory markers gamma interferon-inducible protein 10 (IP-10) and neopterin or the interferon-stimulated gene product 2'-5'-oligoadenylate synthetase (OAS-1) were correlated with the plasma HCV RNA concentration before or during 14-day danoprevir monotherapy. In contrast to pegylated interferon and ribavirin treatment, a higher baseline IP-10 concentration was positively correlated with a greater first-phase HCV RNA decline upon danoprevir administration. Changes in the IP-10 plasma concentration during danoprevir administration were also associated with categorical changes in HCV RNA concentration at days 7 and 14. The neopterin concentration appeared to be moderately decreased during danoprevir administration, although these changes were not statistically significant. However, changes in neopterin concentration showed a statistically significant correlation with changes in IP-10 concentration. Considerable variation in the OAS-1 concentration was observed before and during treatment, including in patients treated with placebo and/or patients with minimal virologic response. Overall, these results suggest that effective treatment with a direct-acting antiviral agent may reduce hepatic inflammation and that first-phase HCV RNA decline during treatment with an NS3/4A protease inhibitor is more robust in patients with high baseline IP-10 concentrations.

Genes and hepatitis C: susceptibility, fibrosis progression and response to treatment

Hepatitis C virus contact and infection show three different phenotypes: spontaneous viral clearance (SVC), chronic hepatitis C (CHC) and sustained virological response (SVR) following antiviral treatment. Many factors, including genetics, influence the evolution of these three phenotypes. We performed a literature search (PubMed) up to 31 January 2010 without language restriction to identify relevant studies on genes and hepatitis C. Additional studies were sought by reviewing the reference lists of the identified articles. Meta-analysis (using Meta-disk 1.4) was conducted to evaluate the association of single nucleotide polymorphism (SNP) in the IL28B region and SVR. The candidate gene approach showed strong relationships between human leucocyte antigen class II (DQB1(*) 0301 and DRB1(*) 1101) and SVC. A cirrhosis risk score involving 7 SNPs has been validated recently. The set of odds ratios of studies demonstrated an association between SNP (rs12987960/rs8099917) in the IL28B and SVR in CHC treated with peginterferon plus ribavirin (OR: 4.6; 95% CI: 2.9-7.3). The overall distribution of protective allele correlated with ethnic differences in SVR (Asians, Europeans, Hispanic and Afro-Americans) together with SVC, but not with fibrosis stage or viral load. These polymorphisms did not influence SVR in very-easy-to-treat patients such as genotype 2/3, rapid virological responders or patients with acute hepatitis C. While the genetic fingerprint for fibrosis progression remains elusive, IL28b polymorphism predicts SVC and SVR. However, nearly half of patients achieving SVR did not show favourable genotype. Further genetic signals are warranted to complete the puzzle of factors influencing hepatitis C.