Inhibitory and combinatorial effect of diphyllin, a v-ATPase blocker, on influenza viruses

Abstract

An influenza pandemic poses a serious threat to humans and animals. Conventional treatments against influenza include two classes of pathogen-targeting antivirals: M2 ion channel blockers (such as amantadine) and neuraminidase inhibitors (such as oseltamivir). Examination of the mechanism of influenza viral infection has shown that endosomal acidification plays a major role in facilitating the fusion between viral and endosomal membranes. This pathway has led to investigations on vacuolar ATPase (v-ATPase) activity, whose role as a regulating factor on influenza virus replication has been verified in extensive genome-wide screenings. Blocking v-ATPase activity thus presents the opportunity to interfere with influenza viral infection by preventing the pH-dependent membrane fusion between endosomes and virions. This study aims to apply diphyllin, a natural compound shown to be as a novel v-ATPase inhibitor, as a potential antiviral for various influenza virus strains using cell-based assays. The results show that diphyllin alters cellular susceptibility to influenza viruses through the inhibition of endosomal acidification, thus interfering with downstream virus replication, including that of known drug-resistant strains. In addition, combinatorial treatment of the host-targeting diphyllin with pathogen-targeting therapeutics (oseltamivir and amantadine) demonstrates enhanced antiviral effects and cell protection in vitro.

Strategies for the Development of Influenza Drugs: Basis for New Efficient Combination Therapies

“…11) [54]. It was demonstrated in a recent study that a combination of the V-ATPase inhibitor diphyllin (40) with oseltamivir effectively inhibits virus propagation in MDCK cells [55].…”

“…Various mechanisms have been described, which contribute to its antiviral efficacy, including inosine monophosphate dehydrogenase inhibition by the monophosphorylated form of ribavirin resulting in reduced GTP levels, immunomodulatory effects by enhancing host T-cell response, interference with RNA capping, induction of lethal point mutations, and polymerase inhibition [98]. A further development is the prodrug viramidine, also named as taribavirin (55), which is converted to ribavirin in the liver. Compared with ribavirin, it possesses similar activity as anti-influenza drug, but has less toxic side effects due to reduced penetration into red blood cells and a shorter half-life in the body [99].…”

Interplay between influenza A virus and host factors: targets for antiviral intervention

“…Cellular vacuolar-type ATPase can also be targeted for the treatment of influenza virus infection [174]. A combinatorial treatment of V-type ATPase with virus targeting has shown a promising antiviral effect and cell protection in vitro [175]. Influenza viruses depend on host CRM1 protein for nuclear export of their nucleoprotein, which can be effectively inhibited by leptomycin B [176].…”

“…Virus- [178,190,191] Vacuolar-type ATPases Endosomal acidification Diphyllin blocks v-ATPase [175] PI3 kinase pathway Regulates endocytic pathway for viral entry LY294002 inhibits PI3K [104] Serine proteases Mediates influenza HA cleavage during fusion of viral and host membranes Aprotinin inhibits cellular proteases; sulfonylated 3-amindinophenylalanylamide derivative inhibits TMPRSS2 [172,173] HSP90AA1…”

Repurposing host-based therapeutics to control coronavirus and influenza virus

“…Diphyllin inhibits endosomal acidification in human osteoclasts and reduces v-ATPase expression in gastric adenocarcinoma cells [43]. Diphyllin has been shown to effectively inhibit IFV infection in MDCK cells with IC 50 values ranging from 0.04 to 0.63 mM [44]. Diphyllin also effectively inhibits the clinically isolated oseltamivir-resistant IFV-A/San Diego/21/2008 (H1N1) strain, which carries a drug-resistant mutation (H275Y) in the NA gene, and the amantadine-resistant A/PR/8/34 strain [44].…”