Genotyping of hepatitis C virus: coinfection by multiple genotypes detected in children with chronic posttransfusion hepatitis C

Small molecule inhibitors of the hepatitis C virus-encoded NS5A protein

Hepatitis C virus (HCV) is a modern-day pandemic; 2-3% of the world's population are thought to be infected with the virus and are subsequently at risk of developing end-stage liver diseases. The traditional standard of care (SOC) for HCV-infected patients has been limited to a regimen of pegylated-interferon alpha (pegIFN) and ribavirin; displaying low cure rates in a majority of patients and severe side effects. However, in 2011 the first direct-acting antivirals (DAA) were licensed to treat HCV-infected patients in combination with SOC, which served to elevate treatment response rates. The HCV drug development pipeline is currently populated with many additional and improved DAAs; primarily molecules that target the virus-encoded protease or polymerase enzymes. These molecules are being evaluated both in combination with the traditional SOC and together with other DAAs as all-oral pegIFN-free regimens with the ultimate goal of developing multiple DAA-containing HCV therapies that do not rely on an pegIFN backbone. A recent addition to the arsenal of HCV inhibitors in development is represented by an entirely new DAA class; molecules that target the HCV-encoded non-enzymatic NS5A protein. NS5A is essential for HCV propagation and, although its actual functions are largely unknown, it is likely a key regulator of viral genome replication and virion assembly. The protein is exquisitely sensitive to small molecule-mediated inhibition; NS5A-targeting molecules are probably the most potent antiviral molecules ever discovered and exhibit a number of other attractive drug-like properties, including activity against many HCV genotypes/subtypes and once-daily dosing potential. Although their mechanism of action is unclear, NS5A-targeting molecules are already proving their utility in clinical evaluation; particularly as components of pegIFN-sparring DAA combination regimens. This review will aim to amalgamate our current understanding and knowledge of NS5A-targeting molecules; their discovery, properties, applications, and insight into their future impact as components of all-oral pegIFN-free DAA combination therapies to combat HCV infection.

Recombination in hepatitis C virus: identification of four novel naturally occurring inter-subtype recombinants

Recombination in Hepatitis C virus (HCV) is considered to be rare. In this study, we performed a phylogenetic analysis of 1278 full-length HCV genome sequences to identify potential recombination events. Nine inter-genotype recombinants were identified, all of which have been previously reported. This confirms the rarity of inter-genotype HCV recombinants. The analysis also identified five inter-subtype recombinants, four of which are documented for the first time (EU246930, EU246931, EU246932, and EU246937). Specifically, the latter represent four different novel recombination types (6a/6o, 6e/6o, 6e/6h, and 6n/6o), and this was well supported by seven independent methods embedded in RDP. The breakpoints of the four novel HCV recombinants are located within the NS5B coding region and were different from all previously reported breakpoints. While the locations of the breakpoints identified by RDP were not identical, they are very close. Our study suggests that while recombination in HCV is rare, this warrants further investigation.

Multiplex real-time reverse transcription-PCR assay for determination of hepatitis C virus genotypes

A variety of methods have been used to determine hepatitis C virus (HCV) genotypes. Because therapeutic decisions for chronic HCV-related hepatitis are made on the basis of genotype, it is important that genotype be accurately determined by clinical laboratories. Existing methods are often subjective, inaccurate, manual, time-consuming, and contamination prone. We therefore evaluated real-time reverse transcription-PCR (RT-PCR) reagents that have recently become commercially available (Abbott HCV Genotype ASR). The assay developed by our laboratory starts with purified RNA and can be performed in 4 to 5 h. An initial evaluation of 479 samples was done with a restriction fragment length polymorphism (RFLP) method and the RT-PCR assay, and discrepant samples were sequenced. An additional 1,200 samples were then tested, and data from all assays were used to evaluate the efficiency and specificity of each genotype-specific reaction. Good correlation between results by the two methods was seen. Discrepant samples included those indeterminate by the RT-PCR assay (n = 110) and a subset that were incorrectly called 2a by the RFLP method (n = 75). The real-time RT-PCR assay performed well with genotype 1, 2, and 3 samples. Inadequate numbers of samples were available to evaluate fully genotypes 4, 5, and 6. Analysis of each primer-probe set demonstrated that weak cross-reactive amplifications were common but usually did not interfere with the genotype determination. However, in about 1% of samples, two or more genotypes amplified at roughly equivalent amounts. Further studies are necessary to determine whether these mixed-genotype samples are true mixtures or a reflection of occasional cross-reactive amplifications.

Detection of multiple hepatitis C virus genotypes in a cohort of injecting drug users

Multiple genotypes of the hepatitis C virus (HCV) were detected in five of 138 HCV RNA positive injecting drug users (IDUs) recruited in Melbourne, Australia. Two were detected by combined LiPA and core and NS5a region sequencing, and three more (selected for testing due to their high-risk behaviour) by heteroduplex mobility analysis. We conclude that the true prevalence of mixed infection in IDUs is undoubtedly higher than the 3.6% (five of 138) we observed, and is underestimated by LiPA, the most common method of genotyping. As responsiveness to HCV treatment varies significantly with genotype, a high prevalence of mixed HCV infections in IDUs must diminish overall treatment efficacy and lessen our ability to reduce the burden of HCV-related disease.

Geographic distribution of hepatitis C virus genotypes in Brazil

Brazil is a country of continental dimension with a population of different ethnic backgrounds. Thus, a wide variation in the frequencies of hepatitis C virus (HCV) genotypes is expected to occur. To address this point, 1,688 sequential samples from chronic HCV patients were analyzed. HCV-RNA was amplified by the RT-PCR from blood samples collected from 1995 to 2000 at different laboratories located in different cities from all Brazilian States. Samples were collected in tubes containing a gel separator, centrifuged in the site of collection and sent by express mail in a refrigerated container to Laboratório Bioquímico Jardim Paulista, São Paulo, SP, Brazil. HCV-RNA was extracted from serum and submitted to RT and nested PCR using standard procedures. Nested PCR products were submitted to cycle sequencing reactions without prior purification. Sequences were analyzed for genotype determination and the following frequencies were found: 64.9% (1,095) for genotype 1, 4.6% (78) for genotype 2, 30.2% (510) for genotype 3, 0.2% (3) for genotype 4, and 0.1% (2) for genotype 5. The frequencies of HCV genotypes were statistically different among Brazilian regions (P = 0.00017). In all regions, genotype 1 was the most frequent (51.7 to 74.1%), reaching the highest value in the North; genotype 2 was more prevalent in the Center-West region (11.4%), especially in Mato Grosso State (25.8%), while genotype 3 was more common in the South (43.2%). Genotypes 4 and 5 were rarely found and only in the Southeast, in São Paulo State. The present data indicate the need for careful epidemiological surveys throughout Brazil since knowing the frequency and distribution of the genotypes would provide key information for understanding the spread of HCV.

High viral load and mild liver injury in children with hemophilia compared with other children with chronic hepatitis C virus infection

BACKGROUND

In adults with hepatitis C virus (HCV) infection, the severity of liver disease may be influenced by the mode of transmission. The purpose of this study was to evaluate whether the mode of transmission affects liver injury and viral load in children with chronic HCV infection, independent of duration of infection and/or HCV genotype.

METHODS

Thirty-nine anti-HCV (EIA-2) positive patients, were divided into three groups: group 1, children with a history of blood transfusion (n = 9; age, 13.3+/-1.3 years), group 2, children with hemophilia (n = 19; age, 11.6+/-0.8 years); and group 3, children with maternal-fetal transmitted disease (n = 10; age, 4.7+/-1.1 years). Serum alanine aminotransferase, HCV viral load, HCV genotype, and liver histology were assessed.

RESULTS

Serum HCV viral load was higher in group 2 (4.27+/-1.0x10(6) copies/ml; p = 0.006) than in group 1 (0.73+/-0.3x10(6) copies/ml) and in group 3 (0.83+/-0.2x10(6) copies/ml). Conversely, group 2 had less severe liver injury compared with children of similar age in group 1 (p = 0.022). Despite a shorter duration of infection, group 3 had liver injury similar to that in group 1. Hepatitis C virus genotype did not influence the level of viremia or liver injury.

CONCLUSIONS

Although children with hemophilia exhibited a high HCV viral load, liver histopathology was less severe than in children who had acquired HCV by blood transfusion or maternal-fetal transmission. These observations support the need to investigate the role of host immune response rather than the virus per se in the pathogenesis of HCV infection in children.

Serological determination of hepatitis C virus subtypes 1a, 1b, 2a, 2b, 3a, and 4a by a recombinant immunoblot assay

Serological determination of hepatitis C virus (HCV) subtypes has been hampered by the lack of suitable assays. Therefore, a recombinant immunoblot assay has been established for serological differentiation of HCV subtypes 1a, 1b, 2a, 2b, 3a, and 4a. It consists of recombinant HCV proteins from the NS-4 region propagated in Escherichia coli. To confirm the serotyping assay results, the results were compared with those obtained by nucleotide sequencing of the NS-5 region. Sera from 157 patients with chronic HCV infection were examined by this assay, and specific antibodies could be detected in 86% (n = 135) of them. The HCV genotype was determined correctly in all but one sample, and the subtypes determined by the serotyping assay corresponded to the HCV subtypes detected by nucleotide sequencing for 95% (n = 128) of the samples. These data indicate that HCV subtypes can be distinguished serologically. The assay that is described provides an easier means of identification of infection with different HCV subtypes for wider clinical and epidemiological applications.

De novo hepatitis C in children after liver transplantation

BACKGROUND

We describe the incidence, results of interferon therapy, and outcome of hepatitis C virus (HCV) hepatitis occurring de novo after pediatric orthotopic liver transplantation (OLT).

METHODS AND RESULTS

Of children undergoing OLT between 1984 and September 1996, 321 children survived for more than 1 year. Of these, 13 (4.0%) developed previously undiagnosed HCV disease, as suggested by HCV antibody testing and HCV polymerase chain reaction and confirmed by liver biopsy. Of the 117 children who received transplants before HCV screening of blood products or donors, 10.2% developed de novo HCV disease. The mean age at diagnosis of HCV hepatitis was 13.2+/-5.0 years, and the mean time to diagnosis after OLT was 8.1 years (range, 4-11 years). The mean alanine aminotransferase (ALT) level at diagnosis was 108 IU/ml, and the liver biopsy specimen showed chronic active or chronic persistent hepatitis in 11 children, cirrhosis in 1 child, and nonspecific changes in 1 child. Twelve children were treated with interferon-2alpha; children who weighed > or =20 kg received 3 x 10(6) units every other day, and those who weighed <20 kg received 1.5 x 10(6) units every other day. Four patients developed rapidly progressive liver failure while receiving interferon therapy and required urgent re-transplantation. Three of the four children again developed histologic evidence of recurrent HCV 4-6 months after the second OLT, and all three subsequently died of HCV-induced liver failure. One patient remains alive and well with no evidence of HCV recurrence and a negative HCV RNA. Of the remaining eight children treated with interferon, only two have had a sustained response (normal ALT) and one is now HCV RNA negative. HCV RNA levels did not correlate with outcome or disease severity. HCV antibody levels were unreliable, with two patients having negative HCV antibody but a positive HCV RNA at diagnosis. Six patients were able to be genotyped: four were la and two were 1b.

CONCLUSION

Overall mortality for de novo HCV hepatitis was 23%. Seventy-five percent of children who received a second transplant for HCV hepatitis had early histologic recurrence that led to liver failure and death. Interferon therapy resulted in a sustained improvement in ALT in only 15% of children. The time to onset and progression of clinical disease both in the original graft and the retransplant graft were accelerated compared with nonimmunosuppressed individuals.

Hepatitis C virus genotypes in chronic hepatitis C of children

Several hepatitis C virus (HCV) genotypes have been recently identified and genotype 1b has been correlated with severe liver disease and a poor response to interferon therapy. HCV infection in children is an interesting model for evaluation of the relationship between HCV genotypes and liver disease, because of its relatively short duration and the infrequent association with confounding cofactors. We have investigated HCV genotypes, using a dot-blot hybridization assay with genotype-specific probes, in 36 Italian children with chronic hepatitis C who were otherwise well and had no other underlying disease. Only four patients were symptomatic; liver histology, obtained in 33 patients, showed minimal hepatitis in 17 and mild chronic hepatitis in 16. Infection with HCV genotype 1b was found in 55.5% of patients, with a peak prevalence of 83% in children from southern Italy (P < 0.05 vs other regions). The remaining children were infected with HCV genotype 1a (16.6%), genotype 2 (11.1%), and mixed (10.9%) or undetermined (2.7%) genotypes. In one patient, HCV viraemia was never detected. There was no statistically significant correlation between genotype and age, sex, source of infection, alanine aminotransferase pattern and histological activity index. These results indicate that genotype 1 b is widespread among Italian children with chronic hepatitis C, although with significant geographical variations. It is not associated with a more severe liver disease, therefore suggesting that the greater severity of liver disease recently reported in adults could reflect the cumulative effects of disease duration and of interfering cofactors.