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As a result of the multiple gathering and travels restrictions during the SARS-CoV-2 pandemic, the annual meeting of the International Society for Antiviral Research (ISAR), the International Conference on Antiviral Research (ICAR), could not be held in person in 2021. Nonetheless, ISAR successfully organized a remote conference, retaining the most critical aspects of all ICARs, a collegiate gathering of researchers in academia, industry, government and non-governmental institutions working to develop, identify, and evaluate effective antiviral therapy for the benefit of all human beings. This article highlights the 2021 remote meeting, which presented the advances and objectives of antiviral and vaccine discovery, research, and development. The meeting resulted in a dynamic and effective exchange of ideas and information, positively impacting the prompt progress towards new and effective prophylaxis and therapeutics.

Gene therapy has become an accepted concept for the treatment of a variety of different diseases. In contrast to preclinical models, subjects enrolled in clinical trials, including gene therapy, possess a history of infection with microbes that may influence its safety and efficacy. Especially, viruses that establish chronic infections in the liver, one of the main targets for in vivo gene therapy, raise important concerns. Among them is the hepatitis B virus (HBV), which has chronically infected more than 350 million people worldwide. Here, we investigated the effect of HBV on adeno-associated viral (AAV) vectors, the most frequently applied gene transfer vehicles for in vivo gene therapy. Unexpectedly, we found that HBV greatly improved AAV transduction in cells replicating HBV and identified HBV protein x (HBx) as a key factor. Whereas HBV-positive and -negative cells were indistinguishable with respect to cell-entry efficiency, significantly higher numbers of AAV vector genomes were successfully delivered to the nucleus in the presence of HBV. The HBV-promoting effect was abolished by inhibitors of phosphatidylinositol 3-kinase (PI3K). PI3K was required for efficient trafficking of AAV to the nucleus and was enhanced in HBV-replicating cells and upon HBx expression. Enhancement of AAV transduction was confirmed in vivo using HBV transgenic mice and could successfully be applied to inhibit HBV progeny release. Conclusion: Our results demonstrate that acute, as well as chronic, infections with unrelated viruses change the intracellular milieu, thereby likely influencing gene therapy outcomes. In the case of HBV, HBx-mediated enhancement of AAV transduction is an advantage that could be exploited for development of novel treatments of HBV infection.

Gene therapy has become an accepted concept for the treatment of a variety of different diseases. In contrast to preclinical models, subjects enrolled in clinical trials, including gene therapy, possess a history of infection with microbes that may influence its safety and efficacy. Especially, viruses that establish chronic infections in the liver, one of the main targets for in vivo gene therapy, raise important concerns. Among them is the hepatitis B virus (HBV), which has chronically infected more than 350 million people worldwide. Here, we investigated the effect of HBV on adeno-associated viral (AAV) vectors, the most frequently applied gene transfer vehicles for in vivo gene therapy. Unexpectedly, we found that HBV greatly improved AAV transduction in cells replicating HBV and identified HBV protein x (HBx) as a key factor. Whereas HBV-positive and -negative cells were indistinguishable with respect to cell-entry efficiency, significantly higher numbers of AAV vector genomes were successfully delivered to the nucleus in the presence of HBV. The HBV-promoting effect was abolished by inhibitors of phosphatidylinositol 3-kinase (PI3K). PI3K was required for efficient trafficking of AAV to the nucleus and was enhanced in HBV-replicating cells and upon HBx expression. Enhancement of AAV transduction was confirmed in vivo using HBV transgenic mice and could successfully be applied to inhibit HBV progeny release. Conclusion: Our results demonstrate that acute, as well as chronic, infections with unrelated viruses change the intracellular milieu, thereby likely influencing gene therapy outcomes. In the case of HBV, HBx-mediated enhancement of AAV transduction is an advantage that could be exploited for development of novel treatments of HBV infection.

The role of cell differentiation state on HBV replication has been well demonstrated, whereas how it determines cell susceptibility to HBV entry is far less understood. We previously showed that umbilical cord matrix stem cells (UCMSC) can be differentiated towards hepatocyte-like cells in vitro. In this study, we infected undifferentiated (UD-) and differentiated (D-) UCMSCs with HBV and studied infection kinetics comparing them to primary human hepatocytes (PHHs). UD-UCMSCs, although being permissive to viral binding, had a very limited uptake capacity, whereas D-UCMSCs showed binding and uptake capabilities similar to PHHs. Likewise, asialoglycoprotein receptor (ASGPR) was upregulated in UCMSCs upon differentiation. In D-UCMSCs, a dose-dependent inhibition of HBV binding and uptake was observed when ASGPR was saturated with known specific ligands. Subsequent viral replication was shown in D-UCMSCs but not in UD-UCMSCs. Susceptibility of UCMSCs to viral replication correlated with the degree of differentiation. Replication efficiency was low compared to PHHs, but was confirmed by (i) a dose-dependent inhibition by specific antiviral treatment using tenofovir, (ii) the increase of viral RNAs along time, (iii) de novo synthesis of viral proteins and (iv) secretion of infectious viral progeny. Conclusions: UCMSCs are turned permissive to support the entire HBV life cycle upon in vitro hepatic differentiation. Despite low replication efficiency, D-UCMSCs proved to be fully capable of HBV uptake. Overall, UCMSCs are a unique human, easily available, non-transformed, in vitro model of HBV infection that could prove useful to study early infection events and the role of cell differentiation state on such events., (MED 3) -- UCL, 2012

Statins are 3-hydroxyl-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors used for the treatment of hypercholesterolemia. It was recently reported that statins inhibit in vitro hepatitis C virus (HCV) RNA replication. We here report that, of five statins studied, mevastatin and simvastatin exhibit the strongest in vitro anti-HCV activity, lovastatin and fluvastatin have moderate inhibitory effects, and pravastatin is devoid of an antiviral effect. A combination of statins with interferon-alpha (IFN-alpha) or HCV nonstructural (NS)5B polymerase or NS3 protease inhibitors results in an additive antiviral activity in short-term (3 days) antiviral assays. Neither statins, at a concentration of five-fold their median effective concentration (EC(50)) value, nor polymerase, protease inhibitors, or IFN-alpha, at concentrations 10- or 20-fold their EC(50) value, were able to clear cells from their replicon following four or six consecutive passages of antiviral pressure. However, the combination of HCV polymerase or protease inhibitors with mevastatin or simvastatin resulted in an efficient clearance of the cultures from their replicon. In colony formation experiments, mevastatin reduced the frequency or prevented the selection of HCV replicons resistant to the nonnucleoside inhibitor HCV-796. Conclusion: A combination of specific HCV inhibitors with statins may result in a more profound antiviral effect and may delay or prevent the development of resistance to such inhibitors., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, FLWIN, info:eu-repo/semantics/published

Statins are 3-hydroxyl-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors used for the treatment of hypercholesterolemia. It was recently reported that statins inhibit in vitro hepatitis C virus (HCV) RNA replication. We here report that, of five statins studied, mevastatin and simvastatin exhibit the strongest in vitro anti-HCV activity, lovastatin and fluvastatin have moderate inhibitory effects, and pravastatin is devoid of an antiviral effect. A combination of statins with interferon-alpha (IFN-alpha) or HCV nonstructural (NS)5B polymerase or NS3 protease inhibitors results in an additive antiviral activity in short-term (3 days) antiviral assays. Neither statins, at a concentration of five-fold their median effective concentration (EC(50)) value, nor polymerase, protease inhibitors, or IFN-alpha, at concentrations 10- or 20-fold their EC(50) value, were able to clear cells from their replicon following four or six consecutive passages of antiviral pressure. However, the combination of HCV polymerase or protease inhibitors with mevastatin or simvastatin resulted in an efficient clearance of the cultures from their replicon. In colony formation experiments, mevastatin reduced the frequency or prevented the selection of HCV replicons resistant to the nonnucleoside inhibitor HCV-796. Conclusion: A combination of specific HCV inhibitors with statins may result in a more profound antiviral effect and may delay or prevent the development of resistance to such inhibitors., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, FLWIN, info:eu-repo/semantics/published