The clinically licensed antifungal drug itraconazole inhibits influenza virus in vitro and in vivo

Abstract

Influenza A virus (IAV) is a common pathogen of respiratory disease. The IAV-induced seasonal epidemics and the sporadic pandemics are associated with high morbidity and mortality. Therefore, effective protection and therapy for IAV infections is an important challenge in countering this public health threat. Because vaccinations only protect against known circulating strains, and the currently available antivirals pose the risk of resistance formation, drugs targeting host cell factors needed for viral replication offer a promising therapeutic approach. In this study, we describe the use of the antifungal therapeutics posaconazole and itraconazole in the therapy of IAV. We show that both drugs efficiently inhibit the propagation of IAV in the cell culture model without being cytotoxic. The mode of action is probably based on several targets and includes both a priming of the interferon response and the induced imbalance of cellular cholesterol. The antiviral effect of itraconazole could be confirmed in the mouse model, where the administration of itraconazole led to a drastic reduction in mortality and a significant increase in the survival rate. Thus, our data indicate a promising therapeutic potential of at least itraconazole in influenza therapy.

Targeting the endolysosomal host-SARS-CoV-2 interface by clinically licensed functional inhibitors of acid sphingomyelinase (FIASMA) including the antidepressant fluoxetine

“…Because the pronounced decrease in SARS-CoV-2 titers observed upon treatment with U18666A hinted at an antiviral capacity of dysregulated endolysosomal cholesterol contents in SARS-CoV-2 infection, we next determined whether fluoxetine treatment of Vero and Calu-3 cells was associated with increased endolysosomal cholesterol pools. We acquired z-stacks from confocal microscopy using CD63 as the specific endolysosomal marker protein (20) (12,13). In line with the images, this quantitative colocalization analysis ( Fig 2B), revealed that fluoxetine at a low concentration of 5 µM caused slightly, yet not significantly elevated cholesterol levels in CD63-positive LELs, whereas treatment with 20 µM fluoxetine induced a prominent and significant endolysosomal cholesterol accumulation.…”

“…Because our previously published results had revealed that increased endolysosomal cholesterol levels act as an effective antiviral barrier for enveloped viruses, including influenza viruses (12)(13)(14)19), we also tested the impact of a post-infection treatment with U18666A, a small molecule inhibitor of the endolysosomal cholesterol transporter NPC1(17) on SARS-CoV-2 infection. As shown in Fig.…”

“…A key feature of the late endosomal compartment is the acidic pH. We, therefore, assessed whether fluoxetine treatment impacted endolysosomal pH values in Calu-3 cells, utilizing a quantitative ratiometric fluorescence microscopy assay (12,13). In control cells, the measured pH was at a value of 4.7, whereas cells exposed to 10 µg/mL U18666A displayed a significantly reduced acidification, well in agreement with our previously reported data of the impact of higher U18666A concentrations on pH values in LELs (19).…”

Targeting the endolysosomal host-SARS-CoV-2 interface by clinically licensed functional inhibitors of acid sphingomyelinase (FIASMA) including the antidepressant fluoxetine

“…Our previous studies identified the host cell cholesterol homeostasis as a crucial component of the infection process of endocytosed enveloped viruses. Importantly, we verified that the increase in late endosomal cholesterol is embedded in the interferon response against incoming influenza A virus (IAV) particles [12], that this barrier has antiviral capacities when raised pharmacologically [13,14], and that this druggable host cell target can be exploited through repurposed drugs in a preclinical murine infection model [13].…”

“…Building on our previous work on the LEL cholesterol balance as a promising therapeutic target for treatment of enveloped viruses [12][13][14]23], we first assessed the antiviral capability of fluoxetine on IAV infection. Because H1N1 and H3N2 subtypes are currently circulating in the human population, Calu-3 cells pretreated with fluoxetine for 16 h were infected with 0.01 MOI of either A/Hamburg/04/2009 (H1N1)pdm09 or A/Panama/2007/99 (H3N2), and the resulting virus titres were measured 24 h p.i.…”