A decade of trials of interferon-alpha for chronic hepatitis C. A meta-regression analysis

Response rates to pegylated interferon and ribavirin in HCV/HIV coinfection: a research synthesis

Several recent trials have determined varying rates of response to pegylated interferon plus ribavirin (peg-IFN + RIB) in hepatitis C virus (HCV)/human immunodeficiency virus-coinfected patients. We sought to identify a pooled response rate and sources of interstudy variability. A literature search was conducted to identify randomized or prospective studies evaluating response rates to peg-IFN + RIB in coinfected patients. A Bayesian hierarchical model was used to estimate overall response rate. Between-study variance was calculated and sensitivity analyses were conducted. Meta-regression was employed to identify sources of between-study variability. The literature search yielded seven studies of 146, which matched keywords and inclusion criteria. The combined patient total was 784. Individual intention-to-treat response rates ranged from 27.3% to 44.2%. The pooled Bayesian estimate of percent response was 33.3%. Significant interstudy heterogeneity was detected. Meta-regression yielded no significant effects of covariates on response rate. Subanalyses by CD4+, HCV viral load and genotype yielded sustained virological response (SVR) odds ratios of 0.73 for low CD4+, 0.41 for high viral load and 0.30 for genotype 1/4. The pooled response rate is not attributable to any one study. Response is poor compared with HCV-monoinfected patients. Interstudy variability is not satisfactorily explained by factors influencing individual response, but may be due to differences between studies unavailable for inclusion in this analysis. However, both genotype 1/4 and high HCV viral load at baseline were significantly associated with a reduction in odds of SVR in pooled subanalysis. Improved treatments are needed in coinfected patients, especially with genotype 1/4 and high viral load.

Action of inhibitors on accumulation of processed hepatitis delta virus RNAs

Hepatitis delta virus (HDV) replication involves processing and accumulation of three RNA species: the genome, its exact complement (the antigenome), and a polyadenylated mRNA that acts as a template for the small delta antigen (deltaAg), the only protein of HDV and essential for genome replication. In a recently reported experimental system, addition of tetracycline induced synthesis of a DNA-directed source of deltaAg, producing within 24 h a significant increase in accumulation of newly transcribed and processed HDV RNAs. This induction was used here to study the action of various inhibitors on accumulation. For example, potent and HDV-specific inhibition, in the absence of detected host toxicity, could be obtained with ribavirin, mycophenolic acid, and viramidine. An interpretation is that these inhibitors reduced the available GTP pool, leading to a specific inhibition of the synthesis and accumulation of HDV RNA-directed RNA species. In contrast, no inhibition was observed with L-FMAU (2'-fluoro-5-methyl-beta-L-arabinofuranosyl-uridine), alpha interferon, or pegylated alpha interferon. After modifications to the experimental system, it was also possible to examine the effects of three known host RNA polymerase inhibitors on HDV genome replication: amanitin, 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), and actinomycin. Of most interest, amanitin at low doses blocked accumulation of HDV RNA-directed mRNA but had less effect on HDV genomic and antigenomic RNAs. Additional experiments indicated that this apparent resistance to amanitin inhibition of genomic and antigenomic RNA relative to mRNA may not reflect a difference in the transcribing polymerase but rather relative differences in the processing and stabilization of nascent RNA transcripts.