Duration of HCV infection as a predictor of nonresponse to interferon

Sequence variability at the internal ribosome entry site of the HCV genome in relation to therapy outcome

Different types of interferon are widely used to treat hepatitis C virus (HCV) infection. Results obtained in vitro suggest that interferon inhibits internal ribosome entry site (IRES)-mediated translation of the HCV genome. To elucidate the possible effect of the nucleotide sequence of IRES on therapy outcome, we compared HCV isolates from patients with sustained response and non-response to interferon/ribavirin combination therapy. In 56 analyzed HCV isolates, nucleotide changes appeared strictly in the stem-loop IIIb region, the stem part from 243 nt to 248 nt, and the polypyrimidine-II region. The natural sequence variability of IRES in isolates of genotype 3a was significantly higher than in isolates of genotype 1b (p < 0.05). The average number of nucleotide changes in genotype 3a correlated with response to therapy (p < 0.05).

Replicative homeostasis III: implications for antiviral therapy and mechanisms of response and non-response

While improved drug regimens have greatly enhanced outcomes for patients with chronic viral infection, antiviral therapy is still not ideal due to drug toxicities, treatment costs, primary drug failure and emergent resistance. New antiviral agents, alternative treatment strategies and a better understanding of viral pathobiology, host responses and drug action are desperately needed. Interferon (IFN) and ribavirin, are effective drugs used to treat hepatitis C (HCV), but the mechanism(s) of their action are uncertain. Error catastrophe (EC), or precipitous loss of replicative fitness caused by genomic mutation, is postulated to mediate ribavirin action, but is a deeply flawed hypothesis lacking empirical confirmation. Paradoxically ribavirin, a proven RNA mutagen, has no impact on HCV viraemia long term, suggesting real viruses, replicating in-vitro, as opposed to mathematical models, replicating in-silico, are likely to resist EC by highly selective replication of fit (~consensus sequence) genomes mediated, in part, by replicative homeostasis (RH), an epicyclic mechanism that dynamically links RNApol fidelity and processivity and other viral protein functions. Replicative homeostasis provides a rational explanation for the various responses seen during treatment of HCV, including genotype-specific and viral load-dependent differential response rates, as well as otherwise unexplained phenomena like the transient inhibition and rebound of HCV viraemia seen during ribavirin monotherapy. Replicative homeostasis also suggests a primarily non-immunological mechanism that mediates increased immune responsiveness during treatment with ribavirin (and other nucleos(t)ide analogues), explicating the enhanced second-phase clearance of HCV ribavirin promotes and, thus, the apparent immunomodulatory action of ribavirin. More importantly, RH suggests specific new antiviral therapeutic strategies.

Prevention could be less cost-effective than cure: the case of hepatitis C screening policies in France

OBJECTIVES

To access the cost-effectiveness of French recommendations for hepatitis C virus (HCV) screening and the extent to which earlier identification of carriers may or not improve the cost-effectiveness of therapeutic strategies.

METHODS

Cost-effectiveness analysis were performed using decision-tree analysis and a Markov model. Four alternative strategies were compared: no screening and no treatment; initiation of HCV treatment after the diagnosis of cirrhosis; and two alternative strategies refer to the current French policies of HCV testing, i.e., two enzyme immunoblot assay (EIA) tests in series, or a polymerase chain reaction (PCR) analysis after the first positive EIA test. Costs were computed from the viewpoint of the health care system. The analysis has been applied to populations particularly at risk of infection, as well as the general population.

RESULTS

The "wait and treat cirrhosis" strategy was more cost-effective in the general population and in transfusion recipients. The incremental cost-effectiveness ratio of this strategy compared with baseline strategy was 3,476 of euros and Euro15,300 in respective cohorts. Considering the HCV screening strategy, the additional cost would be of Euro4,933 and Euro240,250 per additional year of life saved, respectively. In the intravenous drug user (IDU) population, the "two ElA" screening strategy was the more cost-effective alternative, with an additional cost of Euro3,825 per additional year of life saved.

CONCLUSIONS

HCV screening would be discarded for transfusion recipients but should be encouraged for IDUs and also for the general population, in which the additional cost of screening is an order of magnitude more acceptable.

Virus genotype 1b and long-term response to interferon alpha monotherapy in children with chronic hepatitis C

Interferon alpha (IFN-alpha) remains the basic modality in the treatment of chronic hepatitis C in children, but the effects of therapy are still unsatisfactory. The aim of this study was to evaluate parameters linked to IFN-alpha response within a 2-year period. Human C virus (HCV) infected children (n=34) were subdivided into IFN-treated (n=20) and IFN-untreated (n=14 control) groups. The IFN-treated group received a dosage 3 MU of IFN-alpha three times a week for 24 weeks. Liver biopsy was performed in all IFN-treated children and the HCV genotype was determined before the start of the study. Patients were sequentially screened for alanine transaminase (ALT) activity and tested for the presence of HCV-RNA in serum. All patients had either mild persistent or moderate active hepatitis, which was diagnosed from the liver biopsy. In the IFN-treated group ALT normalisation was observed by the end of treatment in 9/20 patients, but after 6 months 10 patients (50%) had sustained ALT normalisation and in 4 of them the virus was eliminated. They continued to show these features up to the end of the observation period (2 years). Eighteen out of 24 children tested had 1b genotype of virus. Out of 10 responders, all patients who were clear of HCV had the 1b genotype. The median age of responders (6.0, range 3.8-16) was significantly lower than non-responders (14.0, range 4-15) In the control group none of the children were clear of HCV-RNA.

CONCLUSION

The negative predictive effect of HCV genotype 1b in the course of IFN-alpha treatment may be not valid in children and other features have to be taken into account in the assessment of the efficacy of therapy.

To interfere and to anti-interfere: the interplay between hepatitis C virus and interferon

As popular strategies used by numerous viruses, interception of interferon (IFN) signaling and inhibition of IFN-induced antiviral functions allow viruses to evade the host immune response and set up successful infections. Hepatitis C virus (HCV), the leading cause of chronic liver disease worldwide and a major public health hazard, causes persistent infection in the majority of infected individuals. IFN-based therapies, currently the only ones available for HCV infection, have been unable to eliminate viral infection in the majority of patients, and many studies suggest that HCV possesses mechanisms to antagonize the IFN-induced antiviral response. Multiple viral, host, and IFN-associated factors have been implicated in the interplay between HCV and IFN. Two viral proteins, NS5A and E2, became the focus of much attention and extensive study because of their abilities to inhibit IFN-induced, double-stranded RNA-activated protein kinase (PKR), a major mediator of the IFN-induced biologic response, and to perturb the IFN signaling pathway. In this review, we discuss the significance of the interferon sensitivity determining region (ISDR) within NS5A, which has been the subject of intense debates. In addition, we discuss the potential mechanisms by which NS5A interferes with IFN signaling and the current working models. Further understanding of the molecular mechanisms underlying the interaction between HCV and IFN will likely facilitate improvement of current IFN-based therapies and development of novel treatments for the HCV pandemic. Future HCV research will benefit from both the development of efficient, convenient model systems for viral propagation, and the utilization of high throughput, genomic-scale approaches.

HCV: epidemiology, modes of transmission and prevention of spread

Approximately 3% of the world's population has been infected with the hepatitis C virus (HCV), which represents about 170 million chronic carriers at risk of developing serious complications. Following the introduction of screening of blood donors for infection the risk of transmitting HCV by blood products is presently at 1/200,000 units distributed. Intravenous (i.v.) drug users are currently the main risk group with a prevalence rate of about 80% and a yearly incidence varying between 4 and 6%. Vertical and sexual transmissions have also been implicated but data are limited and sometimes controversial. The source of infection for the 30% of cases without an identifiable risk factor remains to be clarified. Prevention of spread includes detailed information of persons at risk of being infected, screening of high-risk populations, strengthening of syringe exchanges among i.v. drug users and strict application of disinfection procedures for all invasive medical equipment.

Hepatitis C virus infection in Western Europe

Hepatitis C virus (HCV) infection is now recognised as the most common infection causing chronic liver disease in Europe. Approximately 3% of the world population has been infected with HCV, which represents about 170 million chronic carriers at risk of developing serious complications with more than 5 million in Europe alone. In the general population, the prevalence varies geographically from about 0.5% in northern countries to 2% in Mediterranean countries. Among newly detected HCV cases, 40-60% have normal ALT levels, 80% are viraemic, while about 70% of newly detected HCV carriers present histologic liver disease. More than 75% of the cases remain to be identified. The residual risk for transmitting HCV by blood products is at present 1/200 000 units distributed. Intravenous drug users are currently the main risk group. The prevalence rate is about 80% and the yearly incidence varies between 4 and 6%. In haemodialysis patients, the prevalence ranges from 10% to 30% and the incidence from 3% to 7%. The source of infection for the 30% of cases without identifiable risk factor remains to be clarified and appropriate well-controlled case-control studies on large samples are necessary. Further training and information campaigns remain desirable to improve knowledge and awareness among health care professionals.

Mast cells: a possible link between psychological stress, enteric infection, food allergy and gut hypersensitivity in the irritable bowel syndrome

Intestinal mast cell activation (degranulation), which results from previous enteric infection and/or intestinal allergy, may play a central role in the gut hypersensitivity in both motor response and visceral perception in the Irritable Bowel syndrome. This occurs through various mediators acting on enteric neurons and smooth muscle cells. Psychological stress may trigger this sensitive alarm system via the brain-gut axis.