3 New HCV Treatment Abstracts

April 18, 2011

22.

Hepatology. 2011 Apr;53(4):1090-9. doi: 10.1002/hep.24172.

Genotype differences in susceptibility and resistance development of hepatitis C

virus to protease inhibitors telaprevir (VX-950) and danoprevir (ITMN-191).

Imhof I, Simmonds P.

Centre for Infectious Diseases, University of Edinburgh, Summerhall, Edinburgh,

UK.

Abstract

Protease inhibitors (PIs) have proven to be effective adjuncts to

interferon/ribavirin treatment of hepatitis C virus (HCV) infections. Little

clinical or in vitro data exists, however, on their effectiveness for nontype 1

genotypes that predominate in Europe, the Middle East, Africa, and most of Asia.

NS3 protease and NS4A genes from genotypes 1-6 were inserted into the JFH clone

to generate replication-competent intergenotype chimeras. Susceptibility to PIs

was determined by replication and infectivity assays. To study resistance

development, chimeras were cultured in subinhibitory concentrations of PIs and

mutations phenotypically characterized. Marked differences in susceptibility of

different genotypes to danoprevir (ITMN-191) and telaprevir (VX-950) were

observed. Genotypes 1, 4, and 6 showed median inhibitory concentration (IC(50) )

values of 2-3 nM, >100-fold lower than genotypes 2/3/5 (250-750 nM). Telaprevir

susceptibilities varied over a 4-fold range, with genotypes 1 and 2 being most

susceptible and genotypes 4 and 5 most resistant. Culture of genotypes 1-6 in

PIs induced numerous mutations in the NS3 protease domain, highly variable

between genotypes. Introduction of danoprevir and BILN 2061-induced mutations

into the original clones by site-directed mutagenesis (n = 29) all conferred

resistant phenotypes, with particularly large increases (1-2 log greater IC(50)

values) in the initially susceptible genotypes 1/4/6. Most introduced mutations

and showed little or no effect on replicative fitness. Conclusion: Major

differences were found between genotypes in their susceptibility and resistance

development to PIs. However, equal sensitivities of genotypes 1, 4, and 6 to

danoprevir and a broader efficacy range of telaprevir between genotypes than

initially conceptualized provide strong evidence that PIs might be effectively

used beyond their genotype 1 target group.

(HEPATOLOGY 2011;).

PMID: 21480315 [PubMed - in process]

Hepatology. 2011 Apr;53(4):1080-9. doi: 10.1002/hep.24160.

Host apolipoprotein b messenger RNA-editing enzyme catalytic polypeptide-like 3G

is an innate defensive factor and drug target against hepatitis C virus.

Peng ZG, Zhao ZY, Li YP, Wang YP, Hao LH, Fan B, Li YH, Wang YM, Shan YQ, Han

YX, Zhu YP, Li JR, You XF, Li ZR, Jiang JD.

Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and

Peking Union Medical College, Beijing, China.

Abstract

Host cellular factor apolipoprotein B messenger RNA (mRNA)-editing enzyme

catalytic polypeptide-like 3G (hA3G) is a cytidine deaminase that inhibits a

group of viruses including human immunodeficiency virus-1 (HIV-1). In the

continuation of our research on hA3G, we found that hA3G stabilizing compounds

significantly inhibited hepatitis C virus (HCV) replication. Therefore, this

study investigated the role of hA3G in HCV replication. Introduction of external

hA3G into HCV-infected Huh7.5 human hepatocytes inhibited HCV replication;

knockdown of endogenous hA3G enhanced HCV replication. Exogenous HIV-1 virion

infectivity factor (Vif) decreased intracellular hA3G and therefore enhanced HCV

proliferation, suggesting that the presence of Vif might be an explanation for

the HIV-1/HCV coinfection often observed in HIV-1(+) individuals. Treatment of

the HCV-infected Huh7.5 cells with RN-5 or IMB-26, two known hA3G stabilizing

compounds, increased intracellular hA3G and accordingly inhibited HCV

replication. The compounds inhibit HCV through increasing the level of hA3G

incorporated into HCV particles, but not through inhibiting HCV enzymes.

However, G/A hypermutation in the HCV genome were not detected, suggesting a new

antiviral mechanism of hA3G in HCV, different from that in HIV-1. Stabilization

of hA3G by RN-5 was safe in vivo. Conclusion: hA3G appears to be a cellular

restrict factor against HCV and could be a potential target for drug discovery.

(HEPATOLOGY 2011;).

PMID: 21480314 [PubMed - in process]

J Virol. 2011 Apr 13. [Epub ahead of print]

Analysis of interferon signaling by infectious hepatitis C virus clones with

substitutions of core amino acids 70 and 91.

Funaoka Y, Sakamoto N, Suda G, Itsui Y, Nakagawa M, Kakinuma S, Watanabe T,

Mishima K, Ueyama M, Onozuka I, Nitta S, Kitazume A, Kiyohashi K, Murakawa M,

Azuma S, Tsuchiya K, Watanabe M.

Department of Gastroenterology and Hepatology and Department for Hepatitis

Control, Tokyo Medical and Dental University, Tokyo, Japan.

Abstract

Substitution of amino acids 70 and 91 in HCV core region is a significant

predictor of poor responses to peginterferon plus ribavirin therapy, while their

molecular mechanisms remain unclear. Here, we investigated these differences in

the response to interferon-alpha (IFN) by using HCV cell culture with R70Q,

R70H, and L91M substitutions. IFN treatment of cells transfected or infected

with wild type or the mutant HCV clones showed that the core mutants, R70Q,

R70H, and L91M, were significantly more resistant than the wild type. Among

HCV-transfected cells, intracellular HCV-RNA levels were significantly higher in

the core mutants as compared with the wild type, while HCV-RNA in culture

supernatant was significantly lower in these mutants than the wild type.

IFN-induced phosphorylation of STAT1 and STAT2, and expression of the

interferon-inducible genes were significantly lower in the core mutants than the

wild type, suggesting of cellular unresponsiveness to IFN. Expression level of

an interferon-signal attenuator, SOCS3, was significantly higher in R70Q, R70H

and L91M than the wild type. IL-6, which upregulates SOCS3, was significantly

higher in R70Q, R70H and L91M than the wild type, suggesting of interferon

resistance possibly through IL-6 induced, SOCS3-mediated suppression of

interferon-signaling. Expression level of ER stress proteins were significantly

higher in cells transfected with core mutant than the wild type. In conclusion,

HCV core mutants of R70 and L91 were resistant to interferon in vitro and that

the resistance may be induced by IL-6-induced upregulation of SOCS3. Those

mechanisms may explain clinical interferon resistance of HCV core mutants.

PMID: 21490101 [PubMed - as supplied by publisher]

April 18, 2011