Interferon therapy for acute hepatitis C viral infection--a review by meta-analysis

Challenges and Controversies in the Management of Hepatitis C Virus Infection (Part 1)

Hepatitis C virus (HCV) is emerging as a public health issue in most counties worldwide. The prevalence of HCV infection varies among different geographical areas from 0.5% to 40% with an overall global prevalence of 3%. The WHO estimates that around 170 million people are chronically infected with HCV world wide. Hepatitis CV infection causes a slowly progressive liver disease in over 60% of infected individuals culminating into cirrhosis and ultimately leading to liver failure and hepatocellular carcinoma (HCC). Chronic liver disease due to HCV infection is now the leading indication for livertransplantation both in Europe and the USA. Although the incidence of acute hepatitis C has decreased over the last decade, the number of individuals with HCV-related liver disease continues to rise and is projected to peak around year 2015. As such HCV infection imposes a significant burden on the already exhausted health resources, particularly in the developing counties where the infection is endemic and its incidence is increasing.

Needle stick and other safety issues

Percutaneous injuries such as accidental needle sticks are associated with the greatest risk for occupational transmission of blood-borne pathogens such as hepatitis B and C viruses and HIV. This article presents data on the risk of transmission of these viruses after needle sticks, offers strategies for prevention of injuries from sharp objects, and discusses postexposure prophylaxis recommendations.

Pegylated interferon alpha therapy in acute hepatitis C: relation to hepatitis C virus-specific T cell response kinetics

Pegylated interferon alpha (PEG IFN-alpha) improves sustained virological response rates in chronic hepatitis C, but neither its role in acute hepatitis C nor the biologic basis for its action has been defined. This prospective study assessed the efficacy of PEG IFN-alpha treatment in acute hepatitis C in relation to the kinetics of hepatitis C virus (HCV)-specific CD4(+) T cell responses during therapy and follow-up. Forty subjects with proven acute hepatitis C who received either PEG IFN-alpha plus ribavirin (n = 20) or PEG IFN-alpha monotherapy (n = 20) for 24 weeks in addition to 14 untreated subjects with acute hepatitis C were prospectively followed. Serum HCV RNA, HCV-specific CD4(+) T cell responses, and cytokine production were measured before and during therapy and at follow-up and correlated to the outcome. The sustained virological response rate was 85% with PEG IFN-alpha/ribavirin combination and 80% with PEG IFN-alpha monotherapy. Five untreated subjects had spontaneous recovery. The frequency, magnitude, and breadth of HCV-specific CD4(+) T helper 1 responses were significantly higher in treated subjects compared with untreated subjects with self-limited disease or subjects with chronic evolution. The CD4(+) T cell responses were maintained in subjects with sustained virological responses and self-limited disease but fluctuated in those who developed chronic infection. In conclusion, PEG IFN-alpha therapy in acute hepatitis induces high rates of sustained virological response and prevents choronicity, probably through efficient early stimulation of multispecific HCV-specific CD4(+) T helper 1 responses.

Natural interferon alpha treatment and interferon alpha receptor 2 levels in acute hepatitis C

Efficacy of interferon (IFN) therapy during the acute phase of hepatitis C infection is promising, although the optimal regimen has yet to be determined. It is not known whether the known prognostic factors for chronic hepatitis C (CHC) influence the effect of IFN in acute hepatitis C (AHC). Seventeen patients with AHC were analyzed for hepatic IFN alpha receptor 2 (IFNAR2) prior to IFN treatment. All patients were subsequently treated with either 168 million units (MU) or 336 MU of natural IFN alpha. Seventeen age-matched samples of CHC were provided as controls. The overall sustained response rate was 64.7% (11/17). In patients who received a total dose of 168 MU IFN, the sustained response rate was 28.6% (2/7), and in those who received 336 MU of IFN, the sustained response rate was 90.0% (9/10). The peaks of ALT and HCV-RNA quantity were not associated with the response to IFN. The hepatic IFNAR2 levels were 1.52 +/- 0.34 densitometry units and 0.92 +/- 0.16 in AHC and CHC, respectively (P = 0.042). There was no difference in hepatic IFNAR2 levels between sustained virological responders (SVR) and nonsustained virological responders (NR). The hepatic receptor levels were higher in AHC than in CHC patients. The levels of hepatic IFNAR2 did not differ in SVR and NR, indicating that high-dose natural IFN alpha treatment is effective for AHC, irrespective of the levels of hepatic IFNAR2.

When and how to treat acute hepatitis C?

BACKGROUND

Appropriate treatment of acute hepatitis C is still a matter of controversy due to the lack of large controlled trials.

AIM

To assess the effectiveness of interferon as treatment for acute hepatitis C by meta-analysis.

METHODS

MEDLINE search (1985-2002) was supplemented with manual searches of reference lists. Studies were included if they were controlled trials comparing interferon to no treatment and if they included patients with either post-transfusion or sporadic acute hepatitis C. Twelve trials were analyzed (414 patients). The outcome assessed was the sustained virological response (SVR) rate (undetectable hepatitis C virus RNA in serum at least 6 months after cessation of therapy).

RESULTS

Interferon significantly increased the SVR (risk difference 49%; 95% confidence interval 32.9-65%) in comparison to no treatment. The risk difference of SVR increased from 5 to 90% when trials were ordered by increasing interferon weekly dose. Delaying therapy by 8-12 weeks after the onset of disease does not compromise the SVR rate.

CONCLUSIONS

Current evidence is sufficient to recommend interferon treatment of patients with acute hepatitis C. A later initiation of therapy yields the same likelihood of response as early treatment. A daily induction dose during the 1st month is the best option of treatment.

Management of healthcare workers after occupational exposure to hepatitis C virus

The increasing rate of hepatitis C virus (HCV) infection in the community means that there is increased risk of occupational exposure for healthcare workers. In metropolitan hospitals in Victoria, we found that 80-150 healthcare workers have occupational exposures from HCV-infected patients annually. As there is a 1.8%-3% risk of transmission of HCV from a needlestick injury, two to five healthcare workers are likely to acquire HCV each year in Victoria. These needlestick injuries pose a personal, legal and professional risk to healthcare workers and their patients. Recent information shows that early antiviral treatment of acute HCV infection has high cure rates. Current local and international protocols for management of healthcare workers exposed to HCV do not address these issues. We propose a management protocol after needlestick injury that is stratified according to the likelihood of HCV acquisition and potential risk of staff-to-patient transmission, and that is consistent with the current legal and clinical context of HCV infection in Australia.

Nucleotide triphosphatase/helicase of hepatitis C virus as a target for antiviral therapy

The RNA nucleoside triphosphatase (NTPase)/helicases represent a large family of proteins that are detected in almost all biological systems where RNA plays a central role. The enzymes are capable of enzymatically unwinding duplex RNA structures by disrupting the hydrogen bonds that keep the two strands together. The strand separating activity is associated with hydrolysis of nucleoside triphosphate (NTP). Because of this, potential specific inhibitors of NTPase/helicases could act by one or more of the following mechanisms: (i) inhibition of NTPase activity by interference with NTP binding, (ii) inhibition of NTPase activity by an allosteric mechanism and (iii) inhibition of the coupling of NTP hydrolysis at the unwinding reaction. There are also other inhibitory mechanisms conceivable, which may involve a modulation of the interaction of the enzyme with its RNA substrate, for example, (iv) the competitive inhibition of RNA binding and (v) the inhibition of the unwinding by sterical blockade of the translocation of the NTPase/helicase along the polynucleotide chain. NTPase/helicase has also been identified in the viral genome of hepatitis C virus (HCV) which is a member of the Flaviviridae family. It is conceivable that the inhibition of the unwinding activity of the enzyme leads to the inhibition of virus replication and this may represent a novel antiviral strategy. This review updates the current spectrum of inhibitors targeting different mechanisms by which the NTPase and/or helicase activities of the HCV NTPase/helicase are inhibited. Consequently, some of the compounds might be important as antiviral agents against HCV.

Interferon for acute hepatitis C

BACKGROUND

Acute hepatitis C virus (HCV) infection progresses to chronicity in the majority of patients. In order to prevent the progression to chronic disease, several studies have assessed interferon in patients with acute hepatitis C.

OBJECTIVES

The aim of this review was to assess the efficacy of interferon in acute HCV infection.

SEARCH STRATEGY

We searched MEDLINE, the Cochrane Controlled Trials Register, and the abstracts of the American Association for the Study of Liver Diseases (June 2001). We also contacted pharmaceutical companies to obtain unpublished trials.

SELECTION CRITERIA

Randomised clinical trials comparing interferon with placebo or no treatment, and published as an article, abstract, or letter were selected. No language limitations were used.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data. The following endpoints were analysed: normalization of alanine aminotransferase (ALT) activity at the end of treatment (biochemical ETR); sustained ALT normalization at the end follow-up (biochemical SR); disappearance of serum HCV RNA by polymerase chain reaction assay at the end of treatment (virologic ETR) and at the end of follow-up (virologic SR). Histologic data and adverse events were also recorded. Assessment of drug efficacy used the methods of Peto and Der Simonian and Laird.

MAIN RESULTS

Six randomised trials involving 206 patients with acute hepatitis C met the inclusion criteria. Four trials assessing interferon alfa-2b in 141 patients, all with transfusion-acquired acute hepatitis C, were included. They demonstrated no significant heterogeneity in the outcomes assessed. When compared with no treatment, interferon alfa-2b was associated with an increase in the rates of virologic ETR and SR by 45% (95% CI 31-59%, P < 0.00001) and 29% (95% CI 14-44%, P = 0.0002), respectively. The virologic ETR was 42% (95% CI: 30-56%) in the interferon alfa-2b group versus 4% (95% CI 0-13%, P < 0.00001) in the control group. At the end of follow-up, a virologic SR was seen in 32% (95% CI 21-46%) of interferon-treated patients versus only 4% (95% CI 0-13%, P = 0.00007) of controls. The tolerability of therapy, or the impact of interferon alfa-2b on hepatic histology, was not reported. Two trials assessed interferon beta in a total 65 patients. The efficacy of interferon beta could not be assessed, however, due to heterogeneity of these trials.

REVIEWER'S CONCLUSIONS

Interferon alfa is effective in improving biochemical outcomes and achieving sustained virologic clearance in patients with transfusion-acquired acute hepatitis C. The effect on long-term clinical outcomes could not be assessed due to limitations in the current data.

Combination therapy with interferon-alpha and ribavirin for hepatitis C: practical treatment issues

Combination therapy with ribavirin and interferon (IFN)-alpha for 6 to 12 months is currently the treatment of choice for chronic hepatitis C infection. The overall sustained response rate to treatment, defined as loss of hepatitis C virus (HCV) from serum 6 months after completion of treatment, is 40%. The indications for treatment are serum HCV RNA positivity, abnormal serum transaminases and the presence of portal fibrosis and/or moderate/severe inflammation. Response rates are lower in genotype 1 than in genotype 2 or 3 and in the presence of a high viral load. Anaemia is the most common adverse event and is due to ribavirin; neuropsychiatric adverse effects due to IFNalpha lead to premature cessation of therapy in 10 to 20% of patients. The current recommended dose of interferon is 3MU given subcutaneously 3 times a week. However, it is likely that longer-acting pegylated interferons, which may be more effective and can be administered once weekly, will in the future replace currently used IFNalpha.

Meta-analysis of interferon randomized trials in the treatment of viral hepatitis C in naive patients: 1999 update

The aim of this study was to update our previous meta-analysis of interferon (IFN) in the treatment of hepatitis C and to analyse new factors, namely, HCV RNA end-point, patients with cirrhosis and patients with normal ALT. We use the Der Simonian and Laird method, with heterogeneity and sensitivity analyses. Seventy-six randomized control trials (RCTs) in naive patients were found but we focused our analysis on 59 RCTs with chronic hepatitis C (26 vs. controls and 33 comparing different regimens) and on seven RCTs in acute hepatitis. Interferon-alpha (IFN-alpha) at 3 MU thrice weekly (TIW) for 12 months exhibited 39% of virological end-of-treatment response (ETR) and 17% of virological sustained response (SR), respectively, vs. 1% and 3% in untreated controls (all P < 0.001). There was a significant dose effect (in favour of 6 vs. 3 MU TIW): the virological SR at 6 months were 35% in the 6 MU group (95% CI: 24-47) and 16% in the 3 MU group (95% CI: 8-27) and were at 12 months 43% in the 6 MU group (95%CI: 31-56) and 25% in the 3 MU group (95% CI: 16-37). There was a significant duration effect (12 vs. 6 months) upon the virological SR rate both at 3 and 6 MU: 3 MU provided 14% of virological SR (95% CI: 11-19) in the 12 months group vs. 7% (95% CI: 5-11) in the 6 months group and 6 MU provided 22% (95% CI: 17-29) and 16% (95% CI: 11-22) virological SR in the 12 and 6 months groups, respectively. Cirrhotic treated patients had 17% of virological SR (95 CI: 9-24%; P < 0.001) vs. 0% in controls and provided a 20% reduction rate (95 CI: -2% to -37%, P=0.03) in hepatocellular carcinoma incidence. In acute hepatitis C, a 3-month treatment with IFN-alpha showed significant efficacy vs. controls upon the virological SR rate (32% vs. 4%, P < 0.001). In conclusion, we confirm the dose and duration effect of IFN in chronic hepatitis C, and the efficacy of IFN-alpha in the treatment of acute hepatitis and in cirrhotic patients.

Interferon therapy in haemodialysis patients with acute hepatitis C virus infection and factors that predict response to treatment

In view of the high rate of chronicity of acute hepatitis C and the low efficacy of interferon (IFN) treatment in advanced liver disease, it may be beneficial to treat patients during the acute phase of the infection. Here we assessed the effects of variable-dose IFNalpha-2b treatment in haemodialysis patients with acute hepatitis C virus (HCV) infection, and identified factors that may predict response to this therapy. The study population included 67 patients, but 14 were excluded due to side-effects or because they were lost to follow-up. Seventeen patients who received no specific treatment were used as controls (Group 1). Sixteen and 20 patients received low-(3 MU) and high-dose (6-10 MU) IFNalpha-2b three times weekly for 3 months (Groups 2 and 3, respectively). Virological end-of-treatment response (ETR) was observed in 1 (5.6%), 13 (56.5%), and 17 (65.4%) patients in Groups 1, 2, and 3, respectively, and virological sustained response (SR) was observed in 1 (5.6%), 6 (26.1%), and 13 (50%) patients in the three groups. The rates of virological ETR and SR in the treated groups were significantly higher than those of the control group (P < 0.01 for all comparisons). In multivariate logistic regression analysis, single stranded confirmational polymorphysm (SSCP) band number (P=0.02) was the only factor that was significantly associated with virological SR. In conclusion, IFN-alpha treatment initiated during the acute phase of HCV infection is associated with a higher rate of virological ETR and SR. This study suggested that quasispecies heterogeneity has predictive value with regard to virological SR.

Eradication of hepatitis C virus 1b by interferon in a health care worker with acute hepatitis following needlestick transmission from a patient with chronic hepatitis C unresponsive to interferon

Hepatitis C virus (HCV) was successfully eradicated by a short course of interferon (IFN) therapy in a nurse with acute HCV infection from a needlestick accident. The source patient had chronic hepatitis C and was a nonresponder to IFN therapy. The HCV genotype was 1b in patients, and a single point mutation (H-->R in amino acid 2218) was observed in the IFN sensitivity-determining region of the nonstructural 5A gene, in comparison with sequences of HCV-J, in HCV RNA from both the source patient (before and after IFN therapy) and the recipient (before IFN therapy). Though the strain transmitted was believed to be IFN-resistant in the patient with chronic hepatitis, the patient with acute hepatitis had a sustained response.

Perspectives for the treatment of infections with Flaviviridae

The family Flaviviridae contains three genera: Hepacivirus, Flavivirus, and Pestivirus. Worldwide, more than 170 million people are chronically infected with Hepatitis C virus and are at risk of developing cirrhosis and/or liver cancer. In addition, infections with arthropod-borne flaviviruses (such as dengue fever, Japanese encephalitis, tick-borne encephalitis, St. Louis encephalitis, Murray Valley encephalitis, West Nile, and yellow fever viruses) are emerging throughout the world. The pestiviruses have a serious impact on livestock. Unfortunately, no specific antiviral therapy is available for the treatment or the prevention of infections with members of the Flaviviridae. Ongoing research has identified possible targets for inhibition, including binding of the virus to the cell, uptake of the virus into the cell, the internal ribosome entry site of hepaciviruses and pestiviruses, the capping mechanism of flaviviruses, the viral proteases, the viral RNA-dependent RNA polymerase, and the viral helicase. In light of recent developments, the prevalence of infections caused by these viruses, the disease spectrum, and the impact of infections, different strategies that could be pursued to specifically inhibit viral targets and animal models that are available to study the pathogenesis and antiviral strategies are reviewed.

Treatment of acute hepatitis C virus infection

Chronic hepatitis C is the leading cause of liver-related morbidity and mortality in the Western world. Treatment response in the chronic phase of the disease is still unsatisfactory. Acute hepatitis C takes a chronic course in more than 50% of cases. Interferon therapy treatment in the acute presentation phase is, according to some studies, more efficient than in the chronic phase of disease. The aim of this study was to analyse the response to interferon in acute hepatitis C. This review is based on three published meta-analyses performed using the methods of DerSimonian and Laird. Outcome was assessed by normalisation of serum aminotransferases and clearance of HCV-RNA. Data were presented by calculating the risk difference, which estimated efficacy by calculating the proportion of patients in treatment groups who responded better (0 to 1.0) or worse (0 to -1.0) than untreated control groups. Three mega units of interferon-a2b (IFN) three times a week for 6-24 weeks produced a significant response as measured by long-term normalisation of aminotransferases and clearance of HCV-RNA. Overall rate differences were +0.31 (p<0.01; 95% confidence interval +0.19-0.43) and +0.33 (p<0.001; 95% confidence interval +0.08-0.58). Six MU of IFN three times a week for 16-24 weeks produced better results with a risk difference of +0.53 (95% confidence interval +0.17-0.89) for normalisation of aminotransferases and +0.44 (95% confidence interval +0.06-0.82) for clearance of HCV-RNA. In an uncontrolled trial, 10 MU IFN daily for 4-6 weeks produced clearance of HCV-RNA and normalisation of transaminases in 90% of patients. Twelve weeks' treatment of symptomatic acute hepatitis C with interferon produced a response similar to that of long-term treatment for chronic hepatitis C. More studies are needed to define the role of a higher dose and the start of treatment.

Perspectives for the treatment of infections with Flaviviridae

The family Flaviviridae contains three genera: Hepacivirus, Flavivirus, and Pestivirus. Worldwide, more than 170 million people are chronically infected with Hepatitis C virus and are at risk of developing cirrhosis and/or liver cancer. In addition, infections with arthropod-borne flaviviruses (such as dengue fever, Japanese encephalitis, tick-borne encephalitis, St. Louis encephalitis, Murray Valley encephalitis, West Nile, and yellow fever viruses) are emerging throughout the world. The pestiviruses have a serious impact on livestock. Unfortunately, no specific antiviral therapy is available for the treatment or the prevention of infections with members of the Flaviviridae. Ongoing research has identified possible targets for inhibition, including binding of the virus to the cell, uptake of the virus into the cell, the internal ribosome entry site of hepaciviruses and pestiviruses, the capping mechanism of flaviviruses, the viral proteases, the viral RNA-dependent RNA polymerase, and the viral helicase. In light of recent developments, the prevalence of infections caused by these viruses, the disease spectrum, and the impact of infections, different strategies that could be pursued to specifically inhibit viral targets and animal models that are available to study the pathogenesis and antiviral strategies are reviewed.