Therapeutic options for the highly pathogenic human coronavirus (HCoV) infections are urgently needed. Anti-coronavirus therapy is however challenging, as coronaviruses are biologically diverse and rapidly mutating. In this work, the antiviral activity of seven different carbon quantum dots (CQDs) for the treatment of human coronavirus HCoV-229E infections was investigated. The first generation of antiviral CQDs was derived by hydrothermal carbonization from ethylenediamine/citric acid as carbon precursors and post-modified with boronic acid ligands. These nanostructures showed a concentration dependent virus inactivation with an estimated EC50 of 52±8 µg mL-1. CQDs derived from 4-aminophenylboronic acid without any further modification resulted in the second-generation of anti-HCoV nanomaterials with an EC50 lowered to 5.2±0.7 µg mL-1. The underlying mechanism of action of these CQDs revealed to be inhibition of HCoV-229E entry that could be due to interaction of the functional groups of the CQDs with HCoV-229E entry receptors; surprisingly, an equally large inhibition activity was observed at the viral replication step.

Here, we identify (−)-epigallocatechin- 3 -gallate (EGCG) as a new inhibitor of hepatitis C virus (HCV) entry. EGCG is a flavonoid present in green tea extract belonging to the subclass of catechins, which has many properties. Particularly, EGCG possesses antiviral activity and impairs cellular lipid metabolism. Because of close links between HCV life cycle and lipid metabolism, we postulated that EGCG may interfere with HCV infection. We demonstrate that a concentration of 50 μM of EGCG inhibits HCV infectivity by more than 90% at an early step of the viral life cycle, most likely the entry step. This inhibition was not observed with other members of the Flaviviridae family tested. The antiviral activity of EGCG on HCV entry was confirmed with pseudoparticles expressing HCV envelope glycoproteins E1 and E2 from six different genotypes. In addition, using binding assays at 4°C, we demonstrate that EGCG prevents attachment of the virus to the cell surface, probably by acting directly on the particle. We also show that EGCG has no effect on viral replication and virion secretion. By inhibiting cell-free virus transmission using agarose or neutralizing antibodies, we show that EGCG inhibits HCV cell-to-cell spread. Finally, by successive inoculation of naïve cells with supernatant of HCV-infected cells in the presence of EGCG, we observed that EGCG leads to undetectable levels of infection after four passages. Conclusion : EGCG is a new, interesting anti-HCV molecule that could be used in combination with other direct-acting antivirals. Furthermore, it is a novel tool to further dissect the mechanisms of HCV entry into the hepatocyte.

Common single nucleotide polymorphisms (SNPs) in the ACDC adiponectin encoding gene have been associated with insulin resistance and type 2 diabetes in several populations. Here, we investigate the role of SNPs −11,377C>G, −11,391G>A, +45T>G, and +276G>T in 2,579 French Caucasians (1,229 morbidly obese and 1,350 control subjects). We found an association between severe forms of obesity and −11,377C (odds ratio 1.23, P = 0.001) and +276T (1.19, P = 0.006). Surprisingly, alternative alleles −11,377G and +276G have been previously reported as risk factors for type 2 diabetes. Transmission disequilibrium tests showed a trend in overtransmission (56.7%) of a risk haplotype 1_(C)-1_(G)-1_(T)-2_(T) including −11,377C and +276T in 634 obesity trios (P = 0.097). Family-based analysis in 400 trios from the general population indicated association between obesity haplotype and higher adiponectin levels, suggesting a role of hyperadiponectinemia in weight gain. However, experiments studying the putative roles of SNPs −11,377C>G and +276G>T on ACDC functionality were not conclusive. In contrast, promoter SNP −11,391G>A was associated with higher adiponectin levels in obese children (P = 0.005) and in children from the general population (0.00007). In vitro transcriptional assays showed that −11,391A may increase ACDC activity. In summary, our study suggests that variations at the ACDC/adiponectin gene are associated with risk of severe forms of obesity. However, the mechanisms underlying these possible associations are not fully understood.

Despite the validation of direct-acting antivirals for hepatitis C treatment, the discovery of new compounds with different modes of action may still be of importance for the treatment of special patient populations. We recently identified a natural molecule, epigallocatechin-3-gallate (EGCG), as an inhibitor of hepatitis C virus (HCV) targeting the viral particle. The aim of this work was to discover new natural compounds with higher anti-HCV activity than that of EGCG and determine their mode of action. Eight natural molecules with structure similarity to EGCG were selected. HCV JFH1 in cell culture and HCV pseudoparticle systems were used to determine the antiviral activity and mechanism of action of the compounds. We identified delphinidin, a polyphenol belonging to the anthocyanidin family, as a new inhibitor of HCV entry. Delphinidin inhibits HCV entry in a pangenotypic manner by acting directly on the viral particle and impairing its attachment to the cell surface. Importantly, it is also active against HCV in primary human hepatocytes, with no apparent cytotoxicity and in combination with interferon and boceprevir in cell culture. Different approaches showed that neither aggregation nor destruction of the particle occurred. Cryo-transmission electron microscopy observations of HCV pseudoparticles treated with delphinidin or EGCG showed a bulge on particles that was not observed under control conditions. In conclusion, EGCG and delphinidin inhibit HCV entry by a new mechanism, i.e., alteration of the viral particle structure that impairs its attachment to the cell surface. IMPORTANCE In this article, we identify a new inhibitor of hepatitis C virus (HCV) infection, delphinidin, that prevents HCV entry. This natural compound, a plant pigment responsible for the blue-purple color of flowers and berries, belongs to the flavonoid family, like the catechin EGCG, the major component present in green tea extract, which is also an inhibitor of HCV entry. We studied the mode of action of these two compounds against HCV and demonstrated that they both act directly on the virus, inducing a bulging of the viral envelope. This deformation might be responsible for the observed inhibition of virus attachment to the cell surface. The discovery of such HCV inhibitors with an unusual mode of action is important to better characterize the mechanism of HCV entry into hepatocytes and to help develop a new class of HCV entry inhibitors.

Hepatitis C is a major global health burden with an estimated 160 million infected individuals worldwide. This long-term disease evolves slowly, often leading to chronicity and potentially to liver failure. There is no anti-HCV vaccine, and, until recently, the only treatment available, based on pegylated interferon and ribavirin, was partially effective, and had considerable side effects. With recent advances in the understanding of the HCV life cycle, the development of promising direct acting antivirals (DAAs) has been achieved. Their use in combination with the current treatment has led to encouraging results for HCV genotype 1 patients. However, this therapy is quite expensive and will probably not be accessible for all patients worldwide. For this reason, constant efforts are being made to identify new antiviral molecules. Recent reports about natural compounds highlight their antiviral activity against HCV. Here, we aim to review the natural molecules that interfere with the HCV life cycle and discuss their potential use in HCV therapy.