Distribution of genetic polymorphisms associated with hepatitis C virus (HCV) antiviral response in a multiethnic and admixed population

IL28B gene polymorphism rs12979860, but not rs8099917, contributes to the occurrence of chronic HCV infection in Uruguayan patients

BACKGROUND

Host single-nucleotide polymorphisms (SNPs) near the interleukin 28B (IL28B) locus are associated with sustained virological response to antiviral therapy and with spontaneous Hepatitis C Virus (HCV) clearance. Prevalence of these SNPs varies depending on ethnicity. The impact of IL28B SNPs in HCV-infected patients is currently unknown in Uruguay. Therefore, the aim of this study was to evaluate and compare the distribution of polymorphisms in the IL28B gene (rs12979860 and rs8099917) among HCV-infected patients and healthy individuals in Uruguay and thus assess their possible association with the establishment of HCV infection.

METHODS

DNA was recovered from 92 non-infected individuals and 78 HCV-infected patients and SNPs were determined by RFLP and allelic discrimination by real-time PCR.

RESULTS

The distribution of rs12979860 genotypes for the infected population was 29.5%-CC, 47.4%-CT and 23.1%-TT and for the control group 45.7%, 42.4% and 11.9%, respectively. Prevalence in both infected and uninfected individuals is similar to that reported in other countries with admixed populations. The distribution of rs8099917 genotypes for the infected population was 57.7%-TT, 27.2%-TG and 14.1%-GG and for the control group 60.9%, 33.7% and 5.4%, respectively. The comparison of rs12979860 genotype distribution between the two populations evidenced a higher prevalence of the favourable genotype (CC) in the uninfected control group (p < 0.05). Additionally, results generated using logistic regression analysis show that individuals carrying rs12979860-TT or CT genotypes have a higher likelihood of developing chronic hepatitis upon infection with HCV, when compared to CC carriers, considering rs8099917 genotype as constant.

CONCLUSION

Patients with HCV infection have a statistically significant lower prevalence of the favourable rs12979860 genotype when compared to uninfected individuals; therefore we can establish that only IL28B rs12979860-CT and TT genotypes seem to contribute to the occurrence of chronic HCV infection in the cohort of Uruguayan population studied. Considering that a trend towards a higher frequency of "good" response genotypes was observed in responder patients, we believe that IL28B rs12979860 genotyping could be a useful tool for predicting different therapies outcome, including in the DAA era.

High Prevalence of ITPA Alleles Associated with Ribavirin-Induced Hemolytic Anemia Among Mexican Population

BACKGROUND

The prevalence of two functional polymorphisms (rs1127354 and rs7270101) of the inosine triphosphatase (ITPA) gene associated with ribavirin-induced hemolytic anemia (RIHA) during antiviral therapy for hepatitis C virus (HCV) infection varies by ethnicity. In Mexico, the distribution of these polymorphisms among Native Amerindians (NA) and admixed population (Mestizos) is unknown. This study aimed to determine the prevalence of the ITPA polymorphisms among healthy NA and Mestizos, as well as in HCV patients from West Mexico.

MATERIAL AND METHODS

In a cross-sectional study, 600 unrelated subjects (322 Mestizos, 100 NA, and 178 treatment-naïve, HCV-infected Mestizos patients) were enrolled. A medical history was registered. ITPA genotype was determined by Real-Time PCR. Fst-values and genetic relatedness between study and reference populations were assessed.

RESULTS

The frequency of the risk genotypes rs1127354CC and rs7270101AA was higher among NA (98-100%) than in Mestizos (87-92.9%), (p &amp;lt; 0.05). The NA presented the highest prevalence of the rs1127354CC genotype reported worldwide. The Fst-values revealed a genetic relatedness among Mexican NA, South Americans and African populations (p &amp;gt; 0.05). The frequency of the predicted risk for RIHA was higher among NA (98%) than in Mestizos (80.5%) and HCV-infected patients (81.5%) (p &amp;lt; 0 .01). The CC/AA alleles were associated with lower values of total bilirubin, aspartate/alanine aminotransferases, and aspartate-to-platelet-ratio-index score among HCV-patients.

CONCLUSION

A high prevalence of the ITPA polymorphisms associated with RIHA was found in Mexican NA. These polymorphisms could be a useful tool for evaluating potential adverse effects and the risk or benefit of antiviral therapy in Mexicans and other admixed populations.

Hepatitis C virus pharmacogenomics in Latin American populations: implications in the era of direct-acting antivirals

In recent years, great progress has been made in the field of new therapeutic options for hepatitis C virus (HCV) infection. The new direct-acting antiviral agents (DAAs) represent a great hope for millions of chronically infected individuals because their use may lead to excellent cure rates with fewer side effects. In Latin America, the high prevalence of HCV genotype 1 infection and the significant association of Native American ancestry with risk predictive single-nucleotide polymorphisms (SNPs) in IFNL4 and ITPA genes highlight the need to implement new treatment regimens in these populations. However, the universal accessibility to DAAs is still not a reality in the region as their high cost is one of the major, although not the only, limiting factors for their broad implementation. Therefore, under these circumstances, could the assessment of host genetic markers be a useful tool to prioritize DAA treatment until global access to these new drugs can be achieved? This review will summarize the scientific evidences and the potential implications of HCV pharmacogenomics in this rapidly evolving era of anti-HCV drug development.

SVR Rates of HCV-infected population under PEG-IFN-α/R treatment in Northwest China

BACKGROUND

Chronic HCV Patients taking PEG-IFN-α/R from different ethnic groups have different probabilities of reaching a sustained viral response (SVR). There are many influence factors, such as HCV genotype, IL-28B single-nucleotide polymorphisms (SNP), Fibrosis 4 index (FIB-4), and aspartate aminotransferase-to-platelet ratio index (APRI) score. But the baseline factors in relation to treatment outcome was still not much clear.

METHODS

We evaluated data from 231 chronic HCV patients with or without liver fibrosis and their antiviral efficacy after treatment with pegylated interferon plus ribavirin (PEG-IFN-α/R) for 24-48 weeks. IL-28B SNP and HCV genotypes were analyzed with genome sequencing using pyrosequencing.

RESULTS

Sustained viral response (SVR) rates of patients with HCV 1b and 2a genotypes were 52.25% (58/111) and 75.28% (67/89) (P < 0.01). SVR rates of patients with IL-28B rs8099917 TT, rs12979860 CC and rs12980275 AA were 92.41% (25/27), 92.86% (26/28) and 88.89% (24/27) separately. We found that SVR rates in HCV 1b and 2a patients were only 31.0 and 39.4% if their FIB-4 > 3.25. In addition, when their APRI > 2, only 30.3% of HCV 1b patients and 50.2% of HCV 2a patients could obtain SVR.

CONCLUSIONS

There were high proportion of HCV genotype 1b and 2a in Northwest China. In both HCV 1b and 2a genotypes, patients with protective-genotype of IL-28B were more likely to obtain SVR. However, those with significant fibrosis or cirrhosis were less likely, no matter their genotype. Combined factors of HCV genotype, IL-28B genotype, FIB-4 and ARPI may indicate high prediction and clinical value regarding treatment with PEG-IFN-α/R and prognostic evaluation of chronic hepatitis C patients.

Association with Spontaneous Hepatitis C Viral Clearance and Genetic Differentiation of IL28B/IFNL4 Haplotypes in Populations from Mexico

AIM

To analyze the genetic heterogeneity of the Amerindian and admixed population (Mestizos) based on the IL28B (rs12979860, rs8099917) and IFNL4 (rs368234815) haplotypes, and their association with spontaneous clearance (SC) and liver damage in patients with hepatitis C infection from West Mexico.

METHODS

A total of 711 subjects from West Mexico (181 Amerindians and 530 Mestizos) were studied for the prevalence of IL28B (rs12979860C/T, rs8099917G/T) and IFNL4 (rs368234815∆G/TT) genotypes. A case-control study was performed in 234 treatment-naïve HCV Mestizos (149 chronic hepatitis C and 85 with SC) for the association of haplotypes with SC and liver damage. A real-time PCR assay was used for genotyping, and transitional elastography staged liver damage.

RESULTS

Significant Fst-values indicated differentiation between the studied populations. The frequencies of the protective C, T, TT alleles were significantly lower in the Amerindians than in Mestizos (p<0.05). The r2 measure of linkage disequilibrium was significant for all variants and the T/G/ΔG risk haplotype predominated in Amerindians and secondly in Mestizos. The protective C/T/TT haplotype was associated with SC (OR = 0.46, 95% IC 0.22-0.95, p = 0.03) and less liver damage (OR = 0.32, 95% IC 0.10-0.97, p = 0.04) in chronic patients. The Structure software analysis demonstrated no significant differences in ancestry among SC and chronic patients.

CONCLUSIONS

West Mexico's population is genetically heterogeneous at the IL28B/IFNL4 polymorphisms. The T/G/ΔG high-risk haplotype predominated in Amerindians and the beneficial alternative haplotype in Mestizos. The C/T/TT haplotype was associated with SC and less liver damage in chronically infected Mestizo patients.

Influence of ethnicity on the distribution of genetic polymorphisms associated with risk of chronic liver disease in South American populations

BACKGROUND

The global burden of chronic liver disease is rising. Besides environmental, behavioral, viral and metabolic factors, genetic polymorphisms in patatin-like phospholipase-3 (PNPLA3) and vitamin D receptor (VDR) genes have been related to the development of chronic liver disease and progression towards liver cancer. Although their prevalence differs remarkably among ethnic groups, the frequency of these polymorphisms in South American populations -whose genetic background is highly admixed- has been poorly studied. Hence, the aim of this study was to characterize polymorphisms related to chronic liver disease and their association with the genetic ancestry of South American populations.

RESULTS

DNA samples from 258 healthy unrelated male volunteers were analyzed. The frequencies of G and C alleles of rs738409 polymorphism (PNPLA3 gene) were 74 % and 26 %, respectively; whereas the bAt (CCA) haplotype (VDR gene) was observed in 32.5 % of the samples. The GG genotype of PNPLA3 rs738409 and the bAt (CCA) haplotype -associated with an increased risk of chronic liver disease and progression towards liver cancer- were significantly more frequent among samples exhibiting maternal and paternal Native American haplogroups (63.7 % and 64.6 %), intermediate among admixed samples (45.1 % and 44.9 %; p = 0.03) and the lowest for Non-native American ancestry (30.1 % and 29.6 %; p = 0.001 and p = 0.0008).

CONCLUSIONS

These results suggest that individuals with Native American ancestry might have a high risk of chronic liver disorders and cancer. Furthermore, these data not only support the molecular evaluation of ancestry in multi-ethnic population studies, but also suggest that the characterization of these variants in South American populations may be useful for establishing public health policies aimed at high risk ethnic communities.

Clinical utility of pharmacogenomics in the management of hepatitis C

Hepatitis C virus (HCV) was identified for the first time more than 20 years ago. Since then, several studies have highlighted the complicated aspects of this viral infection in relation to its worldwide prevalence, its clinical presentation, and its therapeutic response. Recently, two landmark scientific breakthroughs have moved us closer to the successful eradication of chronic HCV infection. First, response rates in treatment-naïve patients and in prior non-responders to pegylated-interferon-α and ribavirin therapy are increasing as a direct consequence of the development of direct-acting antiviral drugs. Secondly, the discovery of single-nucleotide polymorphisms near the interleukin 28B gene significantly related to spontaneous and treatment-induced HCV clearance represents a milestone in the HCV therapeutic landscape. The implementation of this pharmacogenomics finding as a routine test for HCV-infected patients has enhanced our understanding of viral pathogenesis, has encouraged the design of ground-breaking antiviral treatment regimens, and has become useful for pretreatment decision making. Nowadays, interleukin 28B genotyping is considered to be a key diagnostic tool for the management of HCV-infected patients and will maintain its significance for new combination treatment schemes using direct-acting antiviral agents and even in interferon-free regimens. Such pharmacogenomics insights represent a challenge to clinicians, researchers, and health administrators to transform this information into knowledge with the aim of elaborating safer and more effective therapeutic strategies specifically designed for each patient. In conclusion, the individualization of treatment regimens for patients with hepatitis C, that may lead to a universal cure in future years, is becoming a reality due to recent developments in biomarker and genomic medicine. In light of these advances, we review the scientific evidence and clinical implications of recent findings related to host genetic factors in the management of HCV infection.