1990-2010: two decades of interferon-based therapy

Identification of novel anti-hepatitis C virus agents by a quantitative high throughput screen in a cell-based infection assay

Hepatitis C virus (HCV) poses a major health threat to the world. The recent development of direct-acting antivirals (DAAs) against HCV has markedly improved the response rate of HCV and reduced the side effects in comparison to the interferon-based therapy. Despite this therapeutic advance, there is still a need to develop new inhibitors that target different stages of the HCV life cycle because of various limitations of the current regimens. In this study, we performed a quantitative high throughput screening of the Molecular Libraries Small Molecule Repository (MLSMR) of ∼350,000 chemicals for novel HCV inhibitors using our previously developed cell-based HCV infection assay. Following confirmation and structural clustering analysis, we narrowed down to 158 compounds from the initial ∼3000 molecules that showed inhibitory activity for further structural and functional analyses. We were able to assign the majority of these compounds to specific stage(s) in the HCV life cycle. Three of them are direct inhibitors of NS3/4A protease. Most of the compounds appear to act on novel targets in HCV life cycle. Four compounds with novel structure and excellent drug-like properties, three targeting HCV entry and one targeting HCV assembly/secretion, were advanced for further development as lead hits. These compounds represent diverse chemotypes that are potential lead compounds for further optimization and may offer promising candidates for the development of novel therapeutics against HCV infection. In addition, they represent novel molecular probes to explore the complex interactions between HCV and the cells.

Replication priority of hepatitis C virus genotype 2a in a Chinese cohort

HCV genotypes have been documented in clinical practice. The aim of this study was to determine the replication priority of different HCV genotypes in a Chinese HCV positive cohort. Serum samples from 491 apparently healthy Chinese blood donors testing positive for HCV antibodies and naive to antiviral drug therapy were tested. Genotyping analysis showed that genotypes 1b and 2a were predominant and accounted for 77.6% of the HCV infections. Among the genotype groups, individuals infected with genotype 2a had an HCV RNA viral load (10⁸ copies/mL) about 200-fold (lg, 2.3) greater than those infected with other genotypes (10⁴–10⁵ copies/mL) indicating a replication priority of genotype 2a. However, there was no correlation between HCV genotype and antibody response suggesting that the amplification advantage of genotype 2a results from a favorable interaction with the host cellular environment. In conclusion, HCV genotypes 1b and 2a are the predominant genotypes in China and genotype 2a possesses a significant replication priority compared with the other genotypes. This suggests the existence of host cellular factors that may act as drug-targets for entirely clearing HCV infection in the future.

Knowledge about infection is the only predictor of treatment in patients with chronic hepatitis C

HCV is the leading cause of cirrhosis and liver cancer in the U.S. The Center for Disease Control (CDC) has recently recommended 'Birth Cohort Screening' of the U.S. Adult population to reduce the future burden of undiagnosed HCV infections in the U.S. Our aim was to assess independent predictors of receiving treatment in a cohort of HCV-infected patients. The Hepatitis C follow-up questionnaires of the National Health and Nutrition Examination Surveys (NHANES) conducted from 2001 to 2010 were used. The NHANES participants who tested positive for HCV RNA were followed by CDC 6 months after initial testing with questions related to their awareness of their infection and history or intention to receive treatment. A total of 500 NHANES participants tested positive for HCV RNA and were targeted for follow-up. Of these, only 203 had completed the follow-up questionnaire (response rate of 40.6%). Of these, only 101 (50%) knew about their HCV positivity before NHANES, and from them, only 34 (17%) had received treatment. In multivariate analysis, prior knowledge about their HCV infection in HCV-positive individuals was independently associated with receiving routine care from a doctor or HMO, with higher income, female gender, being in poor or fair health and not consuming excessive amounts of alcohol. On the other hand, the knowledge about HCV infection was the only independent predictor of receiving anti-HCV treatment (odds ratio 6.14). Knowledge about having HCV infection is the only independent predictor of receiving treatment. Therefore, birth cohort screening of the U.S. General population could lead to wider identification of HCV and potentially better management of the future burden of HCV and its complications.

Potent inhibition of Hendra virus infection via RNA interference and poly I:C immune activation

Hendra virus (HeV) is a highly pathogenic zoonotic paramyxovirus that causes fatal disease in a wide range of species, including humans. HeV was first described in Australia in 1994, and has continued to re-emerge with increasing frequency. HeV is of significant concern to human health due to its high mortality rate, increasing emergence, absence of vaccines and limited post exposure therapies. Here we investigate the use of RNA interference (RNAi) based therapeutics targeting HeV in conjunction with the TLR3 agonist Poly I:C and show that they are potent inhibitors of HeV infection in vitro. We found that short interfering RNAs (siRNAs) targeting the abundantly expressed N, P and M genes of HeV caused over 95% reduction of HeV virus titre, protein and mRNA. Furthermore, we found that the combination of HeV targeting siRNA and Poly I:C had an additive effect in suppressing HeV infection. Our results demonstrate for the first time that RNAi and type I interferon stimulation are effective inhibitors of HeV replication in vitro and may provide an effective therapy for this highly lethal, zoonotic pathogen.

Type I interferon in neurological disease-the devil from within

The members of the type I interferon (IFN-I) family of cytokines are pleiotropic factors that have seminal roles in host defence, acting as antimicrobial and antitumor mediators as well as potent immunomodulatory factors that bridge the innate and adaptive immune responses. Despite these beneficial actions there is mounting evidence that link inappropriate or chronic production of IFN-I in the CNS to the development of a number of severe neuroinflammatory disorders. The most persuasive example is the genetically determined inflammatory encephalopathy, Aicardi-Goutières syndrome (AGS) in which patients have chronically elevated IFN-α production in the CNS. The presentation of AGS can often mimic congenital viral infection, however, molecular genetic studies have identified mutations in six genes that can cause AGS, most likely via dysregulated nucleic acid metabolism and activation of the innate immune response leading to increased intrathecal production of IFN-α. The role of IFN-α as a pathogenic factor in AGS and other neurological disorders has gained considerable support from experimental studies. In particular, a transgenic mouse model with CNS-restricted production of IFN-α replicates many of the cardinal neuropathologic features of AGS and reveal IFN-I to be the "devil from within", mediating molecular and cellular damage within the CNS. Thus, targeting IFN-I may be an effective strategy for the treatment of AGS as well as some other autoimmune and infectious neurological "interferonopathies".

Closing in on the target: sustained virologic response in hepatitis C virus genotype 1 infection response-guided therapy

Retrospective analyses of the boceprevir and telaprevir phase 3 trial data demonstrate the clinical relevance of detected but not quantifiable hepatitis C virus (HCV) genotype 1 RNA during treatment. These analyses illustrate the importance of using precise and standard terminology in reporting low-level HCV RNA results for consistent data collection across clinical trials, and to ensure optimal virologic response-guided treatment decision making in clinical practice. In the context of currently available quantitative HCV RNA assays, we clarify that unquantifiable HCV RNA should be classified as target detected or target not detected, as both have been shown to reflect clinically different qualitative HCV RNA levels during treatment. Additionally, use of terms such as "undetectable" or "below limit of detection" should be avoided as such terms are imprecise, not consistently defined, and often misinterpreted.

Ion channel drug discovery: challenges and future directions

Ion channels are targets of many therapeutically useful agents, and worldwide sales of ion channel-targeted drugs are estimated to be approximately US$12 billion. Nevertheless, considering that over 400 genes encoding ion channel subunits have been identified, ion channels remain significantly under-exploited as therapeutic targets. This is at least partly due to limitations in high-throughput assay technologies that support screening and lead optimization. Will the recent developments in automated electrophysiology rectify this situation? What are the other major limitations and can they be overcome? In this article, we review the status of ion channel drug discovery, discuss current challenges and propose alternative approaches that may facilitate the discovery of new drugs in the future.