Efficacy and Mechanisms of Copper Ion-Catalyzed Inactivation of Human Norovirus

Abstract

The antinoroviral effect of copper ions is well known, yet most of this work has previously been conducted in copper and copper alloy surfaces, not copper ions in solution. In this work, we characterized the effects that Cu ions have on human norovirus capsids’ and surrogates’ integrity to explain empirical data, indicating virus inactivation by copper alloy surfaces, and as means of developing novel metal ion-based virucides. Comparatively high concentrations of Cu(II) ions (>10 mM) had little effect on the infectivity of human norovirus surrogates, so we used sodium ascorbate as a reducing agent to generate unstable Cu(I) ions from solutions of copper bromide. We found that significantly lower concentrations of monovalent copper ions (∼0.1 mM) compared to divalent copper ions cause capsid protein damage that prevents human norovirus capsids from binding to cell receptors in vitro and induce a greater than 4-log reduction in infectivity of Tulane virus, a human norovirus surrogate. Further, these Cu(I) solutions caused reduction of GII.4 norovirus from stool in suspension, producing about a 2-log reduction of virus as measured by a reverse transcriptase-quantitative polymerase chain reaction. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) data indicate substantial major capsid protein cleavage of both GI.7 and GII.4 norovirus capsids, and TEM images show the complete loss of capsid integrity of GI.7 norovirus. GII.4 virus-like particles (VLPs) were less susceptible to inactivation by copper ion treatments than GI.7 VLPs based upon receptor binding and SDS-PAGE analysis of viral capsids. The combined data demonstrate that stabilized Cu(I) ion solutions show promise as highly effective noroviral disinfectants in solution that can potentially be utilized at low concentrations for inactivation of human noroviruses.

In vitro assessment of antibacterial and antiviral activity of three copper products after 200 rounds of simulated use

“…Norovirus has long been a pathogen notorious for its resistance to routine disinfectants, and its ability to survive on surfaces for many days (Mertens et al 2022 ). It is a frequent cause of gastrointestinal outbreaks in public venues and healthcare facilities, and for these reasons was felt to be a most relevant entity to evaluate.…”

“…In addition, research has primarily focused on bacterial pathogens using Cu samples exposed to disinfectants and cleaning cloths not representative of those used in public venues and/or subjected samples to simulated use for relatively short periods (Bryce et al 2020 ; ISO 2022 ; EPA 2008 ). There has been some promising research demonstrating that Cu has excellent antiviral activity but studies are scarce and limited in terms of duration of simulated use with the appropriate disinfectants (Warnes and Keevil 2013 ; van Doremalen et al 2020 ; Warnes et al 2015 ; Glover et al 2022 ; Glass et al 2022 ; Mertens et al 2022 ).…”

Nanoscale Technologies in the Fight against COVID-19: From Innovative Nanomaterials to Computer-Aided Discovery of Potential Antiviral Plant-Derived Drugs

“…Cu was the first metal to be declared an effective metallic antimicrobial agent in 2008 by the U.S. Environmental Protection Agency (EPA). Unlike bacteria, viruses do not develop mechanisms of resistance to copper ions, leading to their high susceptibility towards this metal and its derivatives [ 99 ]. Antiviral activity of copper compounds seems to depend on the release of Cu ions in solution, which generates ROS, leading to the loss of genome integrity, lipid peroxidation, and deactivation of viral enzymes.…”

Galvanic Corrosion of Copper Induced by Metal Nanoparticles for Creating Antiviral Nanocomposites

“…While Ag can affect the capsid of viruses, Cu can inactivate viruses by inhibiting proteases, interacting with metalloproteins, or disordering RNA and its fragmentation . Due to their multimodal virucidal action, copper-based surfaces are considered to be a promising material for the effective inactivation of viruses, including norovirus, , adenovirus, or SARS-CoV-2 . This assumption naturally triggered research focused on the fabrication of copper-based virucidal surfaces.…”