Endosomal NOX2 oxidase exacerbates virus pathogenicity and is a target for antiviral therapy

Abstract

The imminent threat of viral epidemics and pandemics dictates a need for therapeutic approaches that target viral pathology irrespective of the infecting strain. Reactive oxygen species are ancient processes that protect plants, fungi and animals against invading pathogens including bacteria. However, in mammals reactive oxygen species production paradoxically promotes virus pathogenicity by mechanisms not yet defined. Here we identify that the primary enzymatic source of reactive oxygen species, NOX2 oxidase, is activated by single stranded RNA and DNA viruses in endocytic compartments resulting in endosomal hydrogen peroxide generation, which suppresses antiviral and humoral signaling networks via modification of a unique, highly conserved cysteine residue (Cys98) on Toll-like receptor-7. Accordingly, targeted inhibition of endosomal reactive oxygen species production abrogates influenza A virus pathogenicity. We conclude that endosomal reactive oxygen species promote fundamental molecular mechanisms of viral pathogenicity, and the specific targeting of this pathogenic process with endosomal-targeted reactive oxygen species inhibitors has implications for the treatment of viral disease.

Hijacking a host scaffold protein, RACK1, for replication of a plant RNA virus

“…In rice, OsRACK1A interacts with a component of immune complexes and contributes to induction of ROS burst and resistance against the rice blast fungus (Nakashima et al ., ). Although the ROS burst is known to contribute to immunity against biotrophic phytopathogens (Kadota et al ., ), ROS or an oxidative environment could be beneficial or essential for the infection of viruses, including RCNMV (Hyodo et al ., ; To et al ., ; Nishikiori & Ahlquist, ). We showed here that NbRACK1 is essential for the p27‐mediated induction of ROS bursts (Fig.…”

Novel endosomal NOX2 oxidase inhibitor ameliorates pandemic influenza A virus‐induced lung inflammation in mice

“…To support this notion, the specific deletion of the NOX2 gene was associated with improved lung function and a reduced amount of lung tissue damage . Our recent findings revealed that the primary subcellular site of ROS generation to influenza virus infection is the endosome . We previously showed that influenza A virus (IAV) triggers ROS production within the endosome by: (i) internalizing into early endosome antigen‐1 (EEA1)‐positive endosomes by a clathrin‐coated pit‐dependent endocytic process; (ii) activation of endosomally located toll‐like receptor 7 (TLR7) by its single‐stranded RNA content; (iii) activation of protein kinase C that is downstream of TLR7 activation resulting in phosphorylation of the NOX2 oxidase, organizer protein p47phox; and finally (iv) the assembly of the NOX2 oxidase complex at the endosomal membrane releasing superoxide within the endosome lumen .…”

Targeting reactive oxygen species for respiratory infection: Fact or fancy?

“…Our recent study demonstrates how knowledge of organelle‐specific ROS production can be exploited for the treatment of respiratory viral infections . It demonstrates that viruses including low to highly pathogenic influenza, respiratory syncytial virus and rhinovirus are internalized by endocytosis and activate an endosomally located NOX2 oxidase that generates ROS within the endosome.…”

“…As already mentioned, bacteria and fungi are phagocytosed by neutrophils and macrophages resulting in a NOX2‐containing NADPH oxidase‐dependent ROS production in the phagosomal compartment. We have recently shown that viruses that enter cells by endocytosis trigger ROS production within the confines of endosomes via a NOX2‐containing NADPH oxidase . We also know that invading pathogens are likely to drive alterations in metabolism and mitochondrial function .…”

“…As proof of concept of endosome targeting, we developed an innovative molecular targeting system to deliver one of the most specific NOX2 oxidase inhibitors available, gp91ds‐TAT, which comprised of gp91ds‐TAT conjugated via a polyethylene glycol (PEG) linker to cholestanol. Excitingly, cholestanol‐conjugated gp91ds‐TAT caused a substantial reduction in airway inflammation, oxidative stress, viral replication and overall disease severity caused by influenza A virus infection in a mouse model …”