Targeting HCV Entry For Development of Therapeutics

Recent progress in defining the molecular mechanisms of Hepatitis C Virus (HCV) entry affords the opportunity to exploit new viral and host targets for therapeutic intervention. Entry inhibitors would limit the expansion of the infected cell reservoir, and would complement the many replication inhibitors now under development. The current model for the pathway of entry involves the initial docking of the virus onto the cell surface through interactions of virion envelope and associated low density lipoproteins (LDL) with cell surface glycosaminoglycans and lipoprotein receptors, followed by more specific utilization with other hepatocyte membrane proteins: Scavenger Receptor Class B type 1 (SR-BI), CD81, Claudin 1 (CLDN1) and Occludin (OCLN). The use of blockers of these interactions, e.g. specific antibodies, suggests that inhibition of any one step in the entry pathway can inhibit infection. Despite this knowledge base, the tools for compound screening, HCV pseudoparticles (HCVpp) and cell culture virus (HCVcc), and the ability to adapt them to industrial use are only recently available and as a result drug discovery initiatives are in their infancy. Several therapies aiming at modulating the virus envelope to prevent host cell binding are in early clinical testing. The first test case for blocking a cellular co-receptor is an SR-BI modulator. ITX 5061, an orally active small molecule, targets SR-BI and has shown potent antiviral activity against HCVpp and HCVcc. ITX 5061 has exhibited good safety in previous clinical studies, and is being evaluated in the clinic in chronic HCV patients and patients undergoing liver transplantation. Entry inhibitors promise to be valuable players in the future development of curative therapy against HCV

Neutralizing Antibody-Resistant Hepatitis C Virus Cell-to-Cell Transmission

Hepatitis C virus (HCV) can initiate infection by cell-free particle and cell-cell contact-dependent transmission. In this study we use a novel infectious coculture system to examine these alternative modes of infection. Cell-to-cell transmission is relatively resistant to anti-HCV glycoprotein monoclonal anti- bodies and polyclonal immunoglobulin isolated from infected individuals, providing an effective strategy for escaping host humoral immune responses. Chimeric viruses expressing the structural proteins rep- resenting the seven major HCV genotypes demonstrate neutralizing antibody-resistant cell-to-cell trans- mission. HCV entry is a multistep process involving numerous receptors. In this study we demonstrate that, in contrast to earlier reports, CD81 and the tight-junction components claudin-1 and occludin are all essential for both cell-free and cell-to-cell viral transmission. However, scavenger receptor BI (SR-BI) has a more prominent role in cell-to-cell transmission of the virus, with SR-BI-specific antibodies and small-molecule inhibitors showing preferential inhibition of this infection route. These observations highlight the importance of targeting host cell receptors, in particular SR-BI, to control viral infection and spread in the liver

A Minimally Replicative HIV-2 Live-Virus Vaccine ProtectsM. nemestrinafrom Disease after HIV-2287Challenge

AbstractM. nemestrinaimmunized with an apathogenic HIV-2 molecular clone (HIV-2KR) were protected from CD4 decline and disease upon challenge with HIV-2287, after any immunizing virus could be detected. Higher but not lower inocula of HIV-2KRwere protective against intravenous inoculation of either 105or 101TCID50of HIV-2287. Protected animals displayed substantial reductions in PBMC proviral burden (1–3 logs), viral titers (1–2 logs), and plasma viral RNA (2–4 logs) compared to unprotected or naive animals as early as 1 week postinfection. Plasma viral RNA became undetectable after 24 weeks in protected animals, but remained high in unprotected animals. No viral RNA was present in the spleen of the protected animal necropsied more than a year after challenge (though viral DNA was still present). No neutralizing responses could be demonstrated, but CTL activity was detected sooner and at higher levels after challenge in protected than in unprotected macaques. In this novel HIV-2 vaccine model, protection was clearly dose-dependent, and clearance of challenge virus RNA from the plasma did not require detectable ongoing replication of the immunizing virus at the time of challenge

Effect of scavenger receptor BI antagonist ITX5061 in patients with hepatitis C virus infection undergoing liver transplantation

Hepatitis C virus (HCV) entry inhibitors have been hypothesized to prevent infection of the liver after transplantation. ITX5061 is a Scavenger Receptor B-I (SR-BI) antagonist that blocks HCV entry and infection in vitro. We assessed the safety and efficacy of ITX5061 to limit HCV infection of the graft. The study included 23 HCV infected patients undergoing liver transplantation. The first 13 "control" patients did not receive drug. The subsequent 10 patients received ITX5061 150 mg immediately pre- and post-transplant, and daily for 1 week thereafter. ITX5061 pharmacokinetics and plasma HCV RNA were quantified. Viral genetic diversity was measured by ultradeep pyrosequencing. ITX5061 was well tolerated with measurable plasma concentrations during therapy. Whilst the median HCV RNA reduction was greater in ITX treated patients at all time points in the first week after transplantation there was no difference in the overall change in the area over the HCV RNA curve in the 7-day treatment period. However, in genotype 1 infected patients treatment was associated with a sustained reduction in HCV RNA levels compared to the control group (area over the HCV RNA curve analysis, p=0.004). Ultradeep pyrosequencing revealed a complex and evolving pattern of HCV variants infecting the graft during the first week. ITX5061 significantly limited viral evolution where the median divergence between day 0 and day 7 was 3.5% in the control group compared to 0.1% in the treated group.CONCLUSIONS: ITX5061 reduces plasma HCV RNA post transplant notably in genotype 1 infected patients and slows viral evolution. Following liver transplantation the likely contribution of extrahepatic reservoirs of HCV necessitates combining entry inhibitors such as ITX5061 with inhibitors of replication in future studies. Clinicaltrials.gov NCT01292824. This article is protected by copyright. All rights reserved.</p

Pyrvinium Targets the Unfolded Protein Response to Hypoglycemia and Its Anti-Tumor Activity Is Enhanced by Combination Therapy

We identified pyrvinium pamoate, an old anthelminthic medicine, which preferentially inhibits anchorage-independent growth of cancer cells over anchorage-dependent growth (∼10 fold). It was also reported by others to have anti-tumor activity in vivo and selective toxicity against cancer cells under glucose starvation in vitro, but with unknown mechanism. Here, we provide evidence that pyrvinium suppresses the transcriptional activation of GRP78 and GRP94 induced by glucose deprivation or 2-deoxyglucose (2DG, a glycolysis inhibitor), but not by tunicamycin or A23187. Other UPR pathways induced by glucose starvation, e.g. XBP-1, ATF4, were also found suppressed by pyrvinium. Constitutive expression of GRP78 via transgene partially protected cells from pyrvinium induced cell death under glucose starvation, suggesting that suppression of the UPR is involved in pyrvinium mediated cytotoxicity under glucose starvation. Xenograft experiments showed rather marginal overall anti-tumor activity for pyrvinium as a monotherapy. However, the combination of pyrvinium and Doxorubicin demonstrated significantly enhanced efficacy in vivo, supporting a mechanistic treatment concept based on tumor hypoglycemia and UPR

Regulatory genes and viral genomic diversity : symposium transcript

Meeting: International Conference on AIDS, 5th, 4-9 June, 1989, Montreal, QC, CAPresenters: Flossie Wong-Staal, Paul Luciw, William Haseltine, S. Wain-Hobso

Regulatory genes and viral genomic diversity : symposium

Meeting: International Conference on AIDS, 5th, 4-9 June, 1989, Montreal, QC, CAPresenters: Flossie Wong-Staal, Paul Luciw, William Haseltine, S. Wain-Hobso