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Non‐enveloped viruses of different types have evolved distinct mechanisms for penetrating a cellular membrane during infection. Rotavirus penetration appears to occur by a process resembling enveloped‐virus fusion: membrane distortion linked to conformational changes in a viral protein. Evidence for such a mechanism comes from crystallographic analyses of fragments of VP4, the rotavirus‐penetration protein, and infectivity analyses of structure‐based VP4 mutants. We describe here the structure of an infectious rotavirus particle determined by electron cryomicroscopy (cryoEM) and single‐particle analysis at about 4.3 Å resolution. The cryoEM image reconstruction permits a nearly complete trace of the VP4 polypeptide chain, including the positions of most side chains. It shows how the two subfragments of VP4 (VP8 * and VP5 * ) retain their association after proteolytic cleavage, reveals multiple structural roles for the β‐barrel domain of VP5 * , and specifies interactions of VP4 with other capsid proteins. The virion model allows us to integrate structural and functional information into a coherent mechanism for rotavirus entry. The structure of the entire rotavirus particle is revealed by high‐resolution electron cryomicroscopy, providing insight into the structural rearrangements of the coat proteins involved in viral entry.

Background Physical distancing and facemask use are worldwide recognized as effective non‐pharmaceutical interventions (NPIs) against the coronavirus disease‐2019 (COVID‐19). Since January 2020, Taiwan has introduced both NPIs but their effectiveness on non‐COVID‐19 respiratory viruses (NCRVs) remain underexplored. Methods This retrospective observational study examined electronic records at a tertiary hospital in northern Taiwan from pre‐COVID (January–December 2019) to post‐COVID period (January–May 2020). Patients with respiratory syndromes were tested for both enveloped (eg, influenza virus and seasonal coronavirus) and non‐enveloped RVs (eg, enterovirus and rhinovirus) using multiplex reverse transcription polymerase chain reaction assays. Monthly positivity rates of NCRVs among adult and pediatric patients were analyzed with comparison between pre‐ and post‐COVID periods. Results A total of 9693 patients underwent 12 127 multiplex RT‐PCR tests. The average positivity rate of NCRVs reduced by 11.2% (25.6% to 14.4%) after nationwide PHIs. Despite the COVID‐19 pandemic, the most commonly identified enveloped and non‐enveloped viruses were influenza virus and enterovirus/rhinovirus, respectively. Observed reduction in NCRV incidence was predominantly contributed by enveloped NCRVs including influenza viruses. We did not observe epidemiological impacts of NPIs on non‐enveloped viruses but an increasing trend in enterovirus/rhinovirus test positivity rate among pediatric patients. Our data were validated using Taiwan's national notification database. Conclusions Our frontline investigation suggests that the current NPIs in Taiwan might not effectively control the transmission of non‐enveloped respiratory viruses, despite their protective effects against influenza and seasonal coronavirus. Health authorities may consider using hydrogen peroxide or chloride‐based disinfectants as additional preventative strategies against non‐enveloped respiratory viruses in the post‐COVID‐19 era.

Abstract Interactions between viruses and sub-inhibitory concentrations of surfactants in water systems are understudied. At concentrations below the minimum inhibitory concentration (MIC), surfactants may interact with virus surface proteins without virus inactivation and alter virus surface properties. This study determined the MIC of benzyldimethyldodecylammonium chloride (BAC) and sodium dodecyl sulfate (SDS) on human adenovirus (ADV, non-enveloped, dsDNA) and mouse hepatitis virus (MHV, enveloped, ssRNA), and how sub-MIC surfactants influence virus isoelectric point (IEP), hydrated diameter, and interact with virus surface proteins. Both surfactants had MICs of 1 mg/L over 60 minutes. Experimental IEPs were lower than IEPs estimated based on amino acid structures. The ADV IEP was 3.8 without surfactants and dropped to 3.3 with BAC and lower than 3 with SDS. The MHV IEP was 4.2 without surfactants and decreased to 4.1 with SDS and 3.4 with BAC. Dynamic light scattering showed SDS and BAC decreased ADV hydrated diameter from 142 ± 8 nm (no surfactant) to 109–116 nm, while MHV decreased from 150 ± 10 nm (no surfactants) to 132–140 nm upon surfactant exposure. Molecular dynamics simulations revealed that SDS, due to its multivalent sulfate headgroup, forms numerous intimate contacts with the MHV spike protein that markedly perturb its electrostatic environment. In contrast, BAC engages only sporadically and diffusely with the protein, indicating a much weaker influence on its structure and electrostatics. Overall, this study showed that ionic surfactants can influence virus properties thus altering virus interactions with surfaces in engineered and natural systems.

The discovery of novel antiviral materials is important because many infectious diseases are caused by viruses. Silver nanoparticles have demonstrated strong antiviral activity, and graphene is a potential antimicrobial material due to its large surface area, high carrier mobility, and biocompatibility. No studies on the antiviral activity of nanomaterials on non-enveloped viruses have been reported. To investigate the antiviral activity of graphene oxide (GO) sheets and GO sheets with silver particles (GO-Ag) against enveloped and non-enveloped viruses, feline coronavirus (FCoV) with an envelope and infectious bursal disease virus (IBDV) without an envelope were chosen. The morphology and sizes of GO and GO-Ag were characterized by transmission, scanning electron microscopy, and X-ray diffraction. A virus inhibition assay was used to identify the antiviral activity of GO and GO-Ag. Go-Ag inhibited 25% of infection by FCoV and 23% by IBDV, whereas GO only inhibited 16% of infection by FCoV but showed no antiviral activity against the infection by IBDV. Further application of GO and GO-Ag can be considered for personal protection equipment to decrease the transmission of viruses.

Wastewater-based epidemiology (WBE) is a valuable tool for monitoring pathogen spread in communities; however, current protocols mainly target non-enveloped viruses. This study addresses the need for standardized methods to detect both enveloped and non-enveloped viruses by testing four aluminum hydroxide adsorption–precipitation techniques. Wastewater samples were spiked with an enveloped virus surrogate (Φ6 bacteriophage) and a non-enveloped virus surrogate (MS2 coliphage), and viral recovery was assessed using reverse-transcription quantitative PCR (RT-qPCR). The highest recovery for the enveloped virus was achieved with AlCl3 at pH 3.5, a 15 min flocculation time, and a 3% elution solution concentration. For the non-enveloped virus, optimal recovery was found with AlCl3 at pH 6.0, no flocculation time, and a 10% elution solution. The best method for recovering both virus types used AlCl3 at pH 6.0, 15 min flocculation, and a 3% elution solution concentration. This study shows that while optimal conditions vary between virus types, a standardized AlCl3 flocculation protocol can efficiently recover both, providing a cost-effective approach for outbreak monitoring in Grenada.

Background Non-enveloped viruses, which lack a lipid envelope, display higher resistance to disinfectants, soaps and sanitizers compared to enveloped viruses. The capsids of these viruses are highly stable and symmetric protein shells that resist inactivation by commonly employed virucidal agents. This group of viruses include highly transmissible human pathogens such as Rotavirus, Poliovirus, Foot and Mouth Disease Virus, Norovirus and Adenovirus; thus, devising appropriate strategies for chemical disinfection is essential. Results In this study, we tested a mild, hypoallergenic combination of a denaturant, alcohol, and organic acid (3.2% citric acid, 1% urea and 70% ethanol, pH4) on two representative non-enveloped viruses – Human Adenovirus 5 (HAdV5) and Feline Calicivirus (FCV)– and evaluated the pathways of capsid neutralization using biophysical methods. The conformational shifts in the capsid upon chemical treatment were studied using Differential Scanning Calorimetry (DSC), while the morphological alterations were visualized concurrently using Transmission Electron Microscopy (TEM). We found that while treatment of purified HAdV5 particles with a formulation resulted in thermal instability and, large scale aggregation; similar treatment of FCV particles resulted in complete collapse of the capsids. Further, while individual components of the formulation caused significant damage to the capsids, a synergistic action of the whole formulation was evident against both non-enveloped viruses tested. Conclusions The distinct effects of the chemical treatment on the morphology of HAdV5 and FCV suggests that non-enveloped viruses with icosahedral geometry can follow different morphological pathways to inactivation. Synergistic effect of whole formulation is more effective compared to individual components. Molecular level understanding of inactivation pathways may result in the design and development of effective mass-market formulations for rapid neutralization of non-enveloped viruses.

Chitosan films were prepared by solvent casting using an acetic acid-based solution. The films that were developed contained 15.49% of acetic acid solution (10% v/v) and showed biocompatibility in vitro in human keratinocyte HaCaT cells and potent antiviral activity against both enveloped and non-enveloped viruses. The results showed up to 99.98% and 99.92% viral inactivation against the phi 6 enveloped bacteriophage and MS2 non-enveloped bacteriophage, respectively, suggesting that this chitosan/acetic acid film is a promising material for biomedical applications that require biodegradable broad-spectrum antiviral materials.

Plant molecular pharming has emerged as a reliable platform for recombinant protein expression providing a safe and low-cost alternative to bacterial and mammalian cells-based systems. Simultaneously, plant viruses have evolved from pathogens to molecular tools for recombinant protein expression, chimaeric viral vaccine production, and lately, as nanoagents for drug delivery. This review summarizes the genesis of viral vectors and agroinfection, the development of non-enveloped viruses for various biotechnological applications, and the on-going research on enveloped plant viruses.

Several studies on viral inactivation agents frequently overlook the influence of virus suspension conditions, which often leads to inconsistent conclusions. We investigated the impact of cell culture-derived media and environmental contaminants on the efficacy of viral inactivation agents against feline calicivirus (FCV). The FCV in Eagle’s minimum essential medium (EMEM) with cell-derived metabolites, was replaced with distilled water (DW) with using a column-based simple dispersant replacement method. Sodium dodecyl sulfate (SDS) or sodium hypochlorite (NaClO) were less effective against FCV in EMEM than DW, while didecyl dimethylammonium chloride (DDAC) was more effective. The inactivation effect of 50% v/v ethanol was stronger against FCV in EMEM than DW, whereas that of 70% v/v ethanol was more effective in DW. Analysis of the effect of EMEM components revealed that inorganic salts and basic amino acids (BAA) reduced SDS inactivation efficacy but enhanced DDAC’s. Similarly, inorganic salts reduced the effect of 70% v/v ethanol, while amino acids, especially BAA reduced that of NaClO’s. Since each inactivating agent affects FCV differently, the influence of each EMEM component is assumed to differ. Moreover, environmental contaminants, such as bovine serum and saliva, reduced the overall effectiveness of the agents owing to their inorganic substances and proteins.

Viral diseases are a severe public health issue worldwide. During the coronavirus pandemic, the use of alcohol-based sanitizers was recommended by WHO. Enveloped viruses are sensitive to ethanol, whereas non-enveloped viruses are considerably less sensitive. However, no quantitative analysis has been conducted to determine virus ethanol sensitivity and the important variables influencing the inactivation of viruses to ethanol. This study aimed to determine viruses’ sensitivity to ethanol and the most important variables influencing the inactivation of viruses exposed to ethanol based on machine learning. We examined 37 peer-reviewed articles through a systematic search. Quantitative analysis was employed using a decision tree and random forest algorithms. Based on the decision tree, enveloped viruses required around ≥ 35% ethanol with an average contact time of at least 1 min, which reduced the average viral load by 4 log 10 . In non-enveloped viruses with and without organic matter, ≥ 77.50% and ≥ 65% ethanol with an extended contact time of ≥ 2 min were required for a 4 log 10 viral reduction, respectively. Important variables were assessed using a random forest based on the percentage increases in mean square error (%IncMSE) and node purity (%IncNodePurity). Ethanol concentration was a more important variable with a higher %IncMSE and %IncNodePurity than contact time for the inactivation of enveloped and non-enveloped viruses with the available organic matter. Because specific guidelines for virus inactivation by ethanol are lacking, data analysis using machine learning is essential to gain insight from certain datasets. We provide new knowledge for determining guideline values related to the selection of ethanol concentration and contact time that effectively inactivate viruses.