Interferon and Other Therapies for Hepatitis B and Hepatitis C Infections

Experimental and emerging therapies for chronic hepatitis C virus infection

Hepatitis C virus infection is prevalent throughout the world and is associated with substantial morbidity, mortality and health economic burden. No effective preventative measure, including vaccination, is currently available. Incremental and substantial progress in the rate of viral eradication using interferon-based therapies has been made over the past decade. The most recent advance has been related to the development of a pegylated form of IFN-alpha by two independent pharmaceutical companies. Pegylation of IFN-alpha appears to prolong its half-life, allowing for less frequent dosing. Reports have suggested that pegylated interferons are also associated with better efficacy for viral eradication in patients with hepatitis C virus. Slower progress also has been made in developing non-interferon-based therapeutic agents against hepatitis C virus, including protease inhibitors, helicase inhibitors, ribozymes, antisense therapies, cytokine-based therapies and T-cell-based therapeutic vaccines.

Combination therapy with interferon and ribavirin in the treatment of chronic hepatitis C infection

OBJECTIVE

To review and critique the medical literature regarding the combination of interferon and ribavirin in the initial treatment of chronic hepatitis C virus (HCV) infection.

DATA SOURCES

A MEDLINE search (January 1966-June 1999) was conducted to identify human clinical trials regarding the combination of interferon and ribavirin therapy for the initial treatment of chronic HCV. Bibliographies were reviewed for relevant literature.

STUDY SELECTION

Clinical trials of combination interferon and ribavirin for the treatment of chronic HCV in interferon-naïve adults were reviewed.

DATA SYNTHESIS

The combination of ribavirin and interferon in the treatment of chronic HCV has been beneficial in patients who are interferon-naïve. Patients with predictors of poor response, such as baseline cirrhosis, male gender, age >40 years, high baseline viral loads (>2 x 10(6) copies/mL), and genotype 1 respond better to combination treatment when compared with those who receive interferon monotherapy. Patients with genotype 1 and/or high viral loads may benefit most from 48 weeks of combination therapy; however, adverse effects are of greater concern in these patients. Monitoring can limit these complications.

CONCLUSIONS

Combination therapy is effective in the treatment of interferon-naive patients with chronic HCV infection. Patients should be evaluated for duration of treatment with combination therapy by determination of predictors of response. Further trials are needed to more closely evaluate the duration of treatment and to determine the best patient population to receive combination therapy.

A long-term hepatitis B viremia model generated by transplanting nontumorigenic immortalized human hepatocytes in Rag-2-deficient mice

Development of new therapies for human hepatitis B virus infection (HBV) would be greatly facilitated by the availability of a suitable small-animal model for HBV virus production in vivo. To develop a murine model for HBV production, we established an immortalized, cloned liver cell line by transferring the Simian Virus 40 Large T-Antigen into primary human hepatocytes. These cells were stably transfected with a full-length HBV genome to generate a clone that expresses HBV genes and replicates HBV. The HBV-producing cells were transplanted into the livers of mice with combined immunodeficiency (Rag-2 deficient) by intrasplenic injection. Survival of the engrafted human hepatocytes was shown in several ways: fluorescent in situ hybridization (FISH) with a human-chromosome-specific DNA probe (human alpha satellite), dot-blot hybridization of the genomic DNA extracted from liver biopsy specimens with a human-specific Alu repetitive DNA probe, Blur-8, as well as with an HBV DNA probe, and secretion of human proteins into plasma. Histological examination of mouse liver up to 8 months following human cell transplant shows completely normal architecture. Determination of plasma HBV DNA levels indicated that engrafted cells secreted 3x10(7) to 3x10(8) virions per mL into the blood, and HBsAg was detected in plasma. This new murine model of HBV viremia should be useful for in vivo HBV studies.