Dynamics of hepatitis C virus monitored by real-time quantitative polymerase chain reaction during first 2 weeks of IFN-beta treatment are predictive of long-term therapeutic response

Current progress in antiviral strategies

•

Antiviral agents function as either viral targets or host factors.

•

Virus-targeting antivirals (VTAs) function through a direct (DVTAs) or an indirect (InDVTAs) method in the viral life cycle.

•

Host-targeting antivirals (HTAs) include reagents that target the host proteins that are involved in the viral life cycle.

The prevalence of chronic viral infectious diseases, such as human immunodeficiency virus (HIV), hepatitis C virus (HCV), and influenza virus; the emergence and re-emergence of new viral infections, such as picornaviruses and coronaviruses; and, particularly, resistance to currently used antiviral drugs have led to increased demand for new antiviral strategies and reagents. Increased understanding of the molecular mechanisms of viral infection has provided great potential for the discovery of new antiviral agents that target viral proteins or host factors. Virus-targeting antivirals can function directly or indirectly to inhibit the biological functions of viral proteins, mostly enzymatic activities, or to block viral replication machinery. Host-targeting antivirals target the host proteins that are involved in the viral life cycle, regulating the function of the immune system or other cellular processes in host cells. Here we review key targets and considerations for the development of both antiviral strategies.

Is {beta}-interferon a promising therapeutic option for the management of hepatitis C?

Using interferon-alpha (IFN-alpha) as the conventional therapeutic antiviral drug, physicians generally achieve a treatment success of <50% in cases with chronic hepatitis C. Owing to the structural similarities between IFN-alpha and interferon-beta (IFN-beta), the latter is a candidate for obtaining sustained viral response. In this review, we have compiled the published information on the use of IFN-beta for the management of acute and chronic hepatitis C up to 2007. We have looked at the rates of success and side effects. IFN-beta might be helpful if IFN-alpha fails to achieve a favourable outcome. This antiviral drug may be helpful for the management of chronic hepatitis C in both age extremes, in case of a relapse after receiving IFN-alpha and for preventing the development of the carrier state after acute hepatitis C. Further studies are required on the efficacy of IFN-beta for the management of acute and chronic hepatitis C.

Lamivudine and IFN-beta sequential therapy in HBe antigen-positive patients with chronic hepatitis B virus genotype C infection

Sequential treatment with lamivudine and interferon (IFN) has induced sustained biochemical and virologic responses in the majority of patients with chronic hepatitis B in France. However, the efficacy of sequential treatment in patients with chronic hepatitis B virus (HBV) genotype C infection has not been evaluated. Twenty-four HBe antigen-positive patients were treated with 100 mg lamivudine alone for 16-32 weeks, then with both 6 MU IFN-beta and lamivudine for 4 weeks, and lastly with IFN-beta alone for 20 weeks. Sustained response was achieved in 7 (29%) patients 24 weeks after the end of therapy. No lamivudine-resistant variants emerged in any patient. Hepatitis flare occurred in 3 patients after the withdrawal of lamivudine, but none had decompensation. The patients with sustained response were significantly younger at baseline (p = 0.033) and had a significantly lower HBV DNA level at the start of IFN (p = 0.020) than those without sustained response. In conclusion, the rate of response to sequential therapy with lamivudine and IFN in HBe antigen-positive patients with HBV genotype C infection was lower than the rate reported previously. Patients who were young or who had a favorable virologic response to lamivudine were more likely to have a sustained response.

Is interferon-beta an alternative treatment for chronic hepatitis C

The treatment of chronic hepatitis C (CHC) is still far from optimal, particularly for those subpopulations that do not respond to the standard combination therapy with Interferon-α (IFNα) plus ribavirin. Although in some cases the use of higher doses or longer treatment periods may be effective, these approaches are generally associated with a higher incidence of adverse events, which may either lead to a reduction in patient compliance or require drug withdrawal. IFNβ could represent an interesting alternative for treating CHC patients. Controversial data about IFNβ efficacy in CHC exist, the main reason being that many results stem from pilot studies with small cohorts of patients. However, promising results have been obtained in some subgroups of patients that fail to respond to IFNα. Additionally, the good tolerability of IFNβ represents an important advantage of the drug. The rates of dropouts in controlled clinical trials, as well as the need for dose reductions or treatment discontinuation are very low. It might be worth assessing the value of IFNβ plus ribavirin in randomized studies with a larger cohort of patients, not eligible or not tolerating standard therapy, and for non-responders.

Chemiluminescence enzyme immunoassay for monitoring hepatitis C virus core protein during interferon-α2b and ribavirin therapy in patients with genotype 1 and high viral loads

This study evaluated an updated chemiluminescence enzyme immunoassay (CLEIA) for hepatitis C virus (HCV) core protein for monitoring viral kinetics during treatment with interferon (IFN)-alpha and ribavirin. Using the CLEIA, serum levels of HCV core protein were measured in 17 patients with genotype 1 and high baseline viral loads during the first 4 weeks of combination therapy. HCV RNA was measured by the Amplicor Monitor test for comparison. At the start of therapy, the median HCV level (interquartile range) was 700 (540-940) kIU/ml of viral RNA and 11,310 (5,528-14,238) fmol/L of core protein. HCV RNA was above the upper limit of the linear range of the Amplicor Monitor test in 13 of the 17 patients, while the core protein level was within the linear range of the CLEIA in all patients. During therapy, the proportion of patients with HCV levels below the cutoff values at each time point was less with the Amplicor Monitor test than with CLEIA. Serum HCV core protein level decreased rapidly during the first 24 hr of therapy and more slowly thereafter, with median exponential decays of 1.08 and 0.046 log10/day, respectively. In the second phase, between day 1 and 28, the median decrease in HCV core protein level was higher in four patients with sustained virologic response (0.13 log10/day) than in 13 patients with no response (0.028 log10/day, P = 0.042). The wide linear range of the HCV core protein assay is appropriate for measuring viral loads during therapy with IFN-alpha and ribavirin.

Hepatitis C therapeutics: current status and emerging strategies

Chronic infection with hepatitis C virus (HCV) is an emerging global epidemic. The development of effective HCV antiviral therapeutics continues to be a daunting challenge owing to the absence of adequate animal models and tissue-culture systems for analysis and propagation of the virus. Despite these obstacles, inhibitors of the replicative elements of HCV, immune modulators and non-specific hepatoprotective agents are being pursued and exciting progress has been made. Successful therapeutic intervention of HCV will probably require combination approaches and new approaches, including host drug discovery targets.