Detection of oxidative damages on viral capsid protein for evaluating structural integrity and infectivity of human norovirus

Portable and Air Conditioner-Based Bio-Protection Devices to Prevent Airborne Infections in Acute and Long-Term Healthcare Facilities, Public Gathering Places, Public Transportation, and Similar Entities

The nature in which the coronavirus disease 2019 (COVID-19) pandemic started and spread all over the world has surprised and shocked experts and the general population alike. This has brought out a worldwide desire and serious efforts to prevent, or at least reduce, the severity of another airborne viral infection and protect individuals gathering for various reasons. Toward this main purpose, a novel method to disinfect the air, using graded, predictable, safe, and reliable dosage of ultraviolet C (UVC), with specially designed devices, is described here. Individuals exclusively breathing this disinfected air can prevent infection, thus destroying the airborne virus or any other pathogens outside the human body to prevent acute and chronic damage to the organs and provide a sense of security to congregate, use public transport, and be protected in acute and long-term healthcare facilities. The study involved designing and testing a unit with one UVC chamber and another unit with six UVC chambers both enclosed in UVC-opaque housings that could be used to destroy airborne pathogens. Wild-type severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was used as a representative pathogen. The virus was fed into these units and in both units, the virus was destroyed to undetectable levels. Such disinfected air can be made available for individuals to breathe at an individual and a community level. The two units that were studied were able to destroy the SARS-CoV-2 virus completely in UVC-opaque housings, making them safe for human use. By employing the air to bring the virus to the UVC, the problem of the virus getting protected behind structures was avoided. The individuals get to breathe totally disinfected air through a mask or a ventilator. To protect individuals who are unable or unwilling to use these units meant for individual use, the same principle can be expanded for use with air conditioners to provide community protection. It is envisaged that this method can prevent airborne infections from turning into pandemics and is a clear example of advocating prevention, rather than treatment. These units are expandable and the UVC dosage to the pathogen can be adjusted and predictable, thereby making it a standard technique to study the dosage needed to inactivate different pathogens.

Innovative nonthermal technologies for inactivation of emerging foodborne viruses

Various foodborne viruses have been associated with human health during the last decade, causing gastroenteritis and a huge economic burden worldwide. Furthermore, the emergence of new variants of infectious viruses is growing continuously. Inactivation of foodborne viruses in the food industry is a formidable task because although viruses cannot grow in foods, they can survive in the food matrix during food processing and storage environments. Conventional inactivation methods pose various drawbacks, necessitating more effective and environmentally friendly techniques for controlling foodborne viruses during food production and processing. Various inactivation approaches for controlling foodborne viruses have been attempted in the food industry. However, some traditionally used techniques, such as disinfectant-based or heat treatment, are not always efficient. Nonthermal techniques are considered a new platform for effective and safe treatment to inactivate foodborne viruses. This review focuses on foodborne viruses commonly associated with human gastroenteritis, including newly emerged viruses, such as sapovirus and Aichi virus. It also investigates the use of chemical and nonthermal physical treatments as effective technologies to inactivate foodborne viruses.

Investigation of cytotoxic cadmium in aquatic green algae by synchrotron radiation-based Fourier transform infrared spectroscopy: Role of dissolved organic matter

The heavy metal Cd can cause severe toxicity on aquatic algae, but there are few studies on the cytotoxicity of heavy metal on algae based on synchrotron radiation technology. In this study, synchrotron radiation-based Fourier transform infrared spectromicroscopy (SR-FTIR) was used to characterize in vivo the toxic effects of Cd on Cosmarium sp. cells, emphasizing the influence of dissolved organic matter (DOM) on Cd toxicity. Results showed that, in the absence of DOM, obvious growth inhibition, cell volume reduction, and photosynthesis disruption could be observed with increasing Cd concentrations (0-500 μg/L). Based on the SR-FTIR imaging and functional group quantification, it was shown that the biosynthesis of biomolecules such as proteins, lipids, and carbohydrates was inhibited in algal cells. However, the addition of DOM caused significant heterogeneities in biomacromolecule biosynthesis that an increased biosynthesis of carbohydrates and structural lipids but an inhibited biosynthesis of proteins and storage lipids were observed. Furthermore, the correlation analysis and principal component analysis showed a good correlation between v(C-OH)/Amide II and biochemical parameters, indicating that changes of carbohydrates could be used as the biomarker to indicate the cytotoxicity of heavy metals to algal cells. These findings provide insight into the mechanisms of heavy metal cytotoxicity to aquatic algae and systematic cytotoxicity assessment under various aquatic conditions.

Lysine and Arginine Reactivity and Transformation Products during Peptide Chlorination

Chlorine reactions with peptide-bound amino acids form disinfection byproducts and contribute to pathogen inactivation by degrading protein structure and function. Peptide-bound lysine and arginine are two of the seven chlorine-reactive amino acids, but their reactions with chlorine are poorly characterized. Using N-acetylated lysine and arginine as models for peptide-bound amino acids and authentic small peptides, this study demonstrated conversion of the lysine side chain to mono- and dichloramines and the arginine side chain to mono-, di-, and trichloramines in ≤0.5 h. The lysine chloramines formed lysine nitrile and lysine aldehyde at ∼6% yield over ∼1 week. The arginine chloramines formed ornithine nitrile at ∼3% yield over ∼1 week but not the corresponding aldehyde. While researchers hypothesized that the protein aggregation observed during chlorination arises from covalent Schiff base cross-links between lysine aldehyde and lysine on different proteins, no evidence for Schiff base formation was observed. The rapid formation of chloramines and their slow decay indicate that they are more relevant than the aldehydes and nitriles to byproduct formation and pathogen inactivation over timescales relevant to drinking water distribution. Previous research has indicated that lysine chloramines are cytotoxic and genotoxic to human cells. The conversion of lysine and arginine cationic side chains to neutral chloramines should alter protein structure and function and enhance protein aggregation by hydrophobic interactions, contributing to pathogen inactivation.

Understanding the interaction of nucleotides with UVC light: an insight from quantum chemical calculation-based findings

Short-wave ultraviolet (also called UVC) irradiation is a well-adopted method of viral inactivation due to its ability to damage genetic material. A fundamental problem with the UVC inactivation method is that its mechanism of action on viruses is still unknown at the molecular level. To address this problem, herein we investigate the response mechanism of genome materials to UVC light by means of quantum chemical calculations. The spectral properties of four nucleotides, namely, adenine, cytosine, guanine, and uracil, are mainly focused on. Meanwhile, the transition state and reaction rate constant of uracil molecules are also considered to demonstrate the difficulty level of adjacent nucleotide reaction without and with UVC irradiation. The results show that the peak wavelengths are 248.7 nm, 226.1 nm (252.7 nm), 248.3 nm, and 205.8 nm (249.2 nm) for adenine, cytosine, guanine, and uracil nucleotides, respectively. Besides, the reaction rate constants of uracil molecules are 6.419 × 10^-49 s^-1 M^-1 and 5.436 × 10¹¹ s^-1 M^-1 for the ground state and excited state, respectively. Their corresponding half-life values are 1.56 × 10⁴⁸ s and 1.84 × 10^-12 s. This directly suggests that the molecular reaction between nucleotides is a photochemical process and the reaction without UVC irradiation almost cannot occur.

CrAssphage as an indicator of human-fecal contamination in water environment and virus reduction in wastewater treatment

Viral indicators of human-fecal contamination in wastewaters and environmental waters have been getting much attention in the past decade. Cross-assembly phage (crAssphage) is the most abundant DNA virus in human feces. Recently, the usefulness of crAssphage as a microbial source tracking and water quality monitoring tool for human-fecal contamination has been highlighted. Here, we conducted a comprehensive review on crAssphage in water, focusing on detection methodology, concentration range in various waters and wastewaters, specificity to human-fecal contamination, and reduction in wastewater treatment systems. This review highlights that crAssphage is globally distributed in wastewaters and various fecal-contaminated water bodies at high concentrations without seasonal fluctuations. CrAssphage is highly specific to human-fecal contamination and is rarely found in animal feces. It also has a good potential as a performance indicator to ensure virus reduction in wastewater treatment systems. Accordingly, crAssphage could be an effective tool for monitoring of human-fecal contamination and potential presence of fecal pathogenic microbes in environmental waters. Bridging the research gaps highlighted in this review would make crAssphage a powerful tool to support the control of water-related health risks.

Effect of Ultraviolet-C Light-Emitting Diode Treatment on Disinfection of Norovirus in Processing Water for Reuse of Brine Water

Processes in the food industry that use large amounts of water have been an important cause of waterborne disease outbreaks, as they expose individuals to risks for waterborne disease transmission. Developing technologies to ensure the hygiene and safety of food-processing steps is an urgent concern from an economic perspective. Furthermore, economic benefits can be derived if the processed water can be reused under microbiologically safe conditions. Among the major manufacturing processes in the kimchi industry, the brining process for salted kimchi cabbages requires a considerable amount of brine (approximately 2,000–2,500 l/1,000 kg of raw cabbage). The aim of this study was to establish virucidal conditions with ultraviolet-C light-emitting diodes (UVC LEDs) that can ensure the microbiological safety of brine water samples with various turbidities for reuse after disinfection. For quantitative analysis, first of all, magnetic bead separation (MBS) technique was used to capture and recover the human norovirus (HuNoV) virus particles; propidium monoazide (PMA) combined with RT-qPCR (PMA-RT-qPCR) was subsequently used to selectively detect infectious norovirus. Overall, as the turbidity of the brine water samples increased, the reduction in the HuNoV genogroup II genotype 4 (HuNoV GII.4) levels by UVC LED disinfection decreased. The derived inactivation rate constant (k_inac) and inactivation curves (calculated using the log-linear model) were studied as a function of turbidity based on the exponential one-phase inactivation kinetics of HuNoV. Using an impeller system set at 100 rotations/min (rpm) with an eight-nephelometric turbidity unit (NTU) sample (the lowest turbidity studied), the k_inact based on the levels of viral genomic RNA concentrations was approximately 2.15-fold higher than that observed without rotation (0 rpm). Moreover, the k_inact increased 1.69-fold with a 56-NTU sample (the highest turbidity studied) when the impeller system was set at 100 rpm. UVC LED treatment decreased the HuNoV GII.4 population more effectively in conjunction with the impeller system (100 rpm) than without the impeller system. Our novel findings and model provide fundamental and scientific data that may help reuse brine water and ensure its microbiological safety through disinfection. Our study highlights the benefits of UVC LED treatment in successfully eliminating waterborne viruses in a prompt, resistance-reducing, and energy-efficient approach at the laboratory scale, which lays the foundation for future plant-scale studies of UVC LED-disinfection systems.

Evaluation of Virucidal Efficacy of Human Norovirus Using Combined Sprayed Slightly Acidic Electrolyzed Water and Ultraviolet C-Light-Emitting Diode Irradiation Treatment Based on Optimized Capture Assay for Quantitative RT-qPCR

Slightly acidic electrolyzed water (SAEW), an effective non-thermal virucidal treatment, is used widely to prevent infectious viral cross-contamination. Surface disinfection technologies using ultraviolet C-light-emitting diode (UVC-LED) irradiation have recently attracted considerable attention. The SAEW sprayer technique is an efficient approach to preventing the spread of infectious viral pathogens in the public healthcare sector. Therefore, we investigated a small-scale system comprising sprayed SAEW disinfection combined with UVC-LED irradiation to inactivate the human norovirus (HuNoV) in the environment. A stainless-steel surface was inoculated with a HuNoV genogroup II genotype 4 (GII.4) to achieve maximum reduction values of 3.21 log10 genomic copies. For optimal disinfection conditions, the response surface methodology based on the Box–Behnken design revealed that the specific treatment conditions for inactivation of HuNoV GII.4 were an SAEW droplet volume of 180 μL, 30 ppm available chlorine concentration of SAEW, and a UVC-LED exposure dose of 2 mJ/cm². The results indicate that the combined disinfection treatment could efficiently prevent the spread of HuNoVs in environment. Furthermore, the quadratic polynomial equations of the 3-D response surface can be employed to predict the effects of combined disinfection treatment on HuNoV contamination on environmental surfaces. Therefore, sprayed SAEW disinfection combined with UVC-LED irradiation proposed in this study may offer insights for designing optimal control strategies and techniques to prevent the transmission of infectious diseases, particularly HuNoV.

Virus Removal and Inactivation Mechanisms during Iron Electrocoagulation: Capsid and Genome Damages and Electro-Fenton Reactions

Virus destabilization and inactivation are critical considerations in providing safe drinking water. We demonstrate that iron electrocoagulation simultaneously removed (via sweep flocculation) and inactivated a non-enveloped virus surrogate (MS2 bacteriophage) under slightly acidic conditions, resulting in highly effective virus control (e.g., 5-logs at 20 mg Fe/L and pH 6.4 in 30 min). Electrocoagulation simultaneously generated H₂O₂ and Fe(II) that can potentially trigger electro-Fenton reactions to produce reactive oxygen species such as ^•OH and high valent oxoiron(IV) that are capable of inactivating viruses. To date, viral attenuation during water treatment has been largely probed by evaluating infective virions (as plaque forming units) or genomic damage (via the quantitative polymerase chain reaction). In addition to these existing means of assessing virus attenuation, a novel technique of correlating transmission electron micrographs of electrocoagulated MS2 with their computationally altered three-dimensional electron density maps was developed to provide direct visual evidence of capsid morphological damages during electrocoagulation. The majority of coliphages lost at least 10-60% of the capsid protein missing a minimum of one of the 5-fold and two of 3- and 2-fold regions upon electrocoagulation, revealing substantial localized capsid deformation. Attenuated total reflectance-Fourier transform infrared spectroscopy revealed potential oxidation of viral coat proteins and modification of their secondary structures that were attributed to reactive oxygen species. Iron electrocoagulation simultaneously disinfects and coagulates non-enveloped viruses (unlike conventional coagulation), adding to the robustness of multiple barriers necessary for public health protection and appears to be a promising technology for small-scale distributed water treatment.

Aerobic Conditions and Endogenous Reactive Oxygen Species Reduce the Production of Infectious MS2 Phage by Escherichia coli

Most of the defective/non-infectious enteric phages and viruses that end up in wastewater originate in human feces. Some of the causes of this high level of inactivity at the host stage are unknown. There is a significant gap between how enteric phages are environmentally transmitted and how we might design molecular tools that would only detect infectious ones. Thus, there is a need to explain the low proportion of infectious viral particles once replicated. By analyzing lysis plaque content, we were able to confirm that, under aerobic conditions, Escherichia coli produce low numbers of infectious MS2 phages (I) than the total number of phages indicated by the genome copies (G) with an I/G ratio of around 2%. Anaerobic conditions of replication and ROS inhibition increase the I/G ratio to 8 and 25%, respectively. These data cannot only be explained by variations in the total numbers of MS2 phages produced or in the metabolism of E. coli. We therefore suggest that oxidative damage impacts the molecular replication and assembly of MS2 phages.

UVC disinfects SARS-CoV-2 by induction of viral genome damage without apparent effects on viral morphology and proteins

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been a pandemic threat worldwide and causes severe health and economic burdens. Contaminated environments, such as personal items and room surfaces, are considered to have virus transmission potential. Ultraviolet C (UVC) light has demonstrated germicidal ability and removes environmental contamination. UVC has inactivated SARS-CoV-2; however, the underlying mechanisms are not clear. It was confirmed here that UVC 253.7 nm, with a dose of 500 μW/cm2, completely inactivated SARS-CoV-2 in a time-dependent manner and reduced virus infectivity by 10-4.9-fold within 30 s. Immunoblotting analysis for viral spike and nucleocapsid proteins showed that UVC treatment did not damage viral proteins. The viral particle morphology remained intact even when the virus completely lost infectivity after UVC irradiation, as observed by transmission electronic microscopy. In contrast, UVC irradiation-induced genome damage was identified using the newly developed long reverse-transcription quantitative-polymerase chain reaction (RT-qPCR) assay, but not conventional RT-qPCR. The six developed long RT-PCR assays that covered the full-length viral genome clearly indicated a negative correlation between virus infectivity and UVC irradiation-induced genome damage (R2 ranging from 0.75 to 0.96). Altogether, these results provide evidence that UVC inactivates SARS-CoV-2 through the induction of viral genome damage.

Free Chlorine and Peroxynitrite Alter the Capsid Structure of Human Norovirus GII.4 and Its Capacity to Bind Histo-Blood Group Antigens

Human noroviruses (HuNoVs) are one of the leading causes of acute gastroenteritis worldwide. HuNoVs are frequently detected in water and foodstuffs. Free chlorine and peroxynitrite (ONOO⁻) are two oxidants commonly encountered by HuNoVs in humans or in the environment during their natural life cycle. In this study, we defined the effects of these two oxidants on GII.4 HuNoVs and GII.4 virus-like particles (VLPs). The impact on the capsid structure, the major capsid protein VP1 and the ability of the viral capsid to bind to histo-blood group antigens (HBGAs) following oxidative treatments were analyzed. HBGAs are attachment factors that promote HuNoV infection in human hosts. Overall, our results indicate that free chlorine acts on regions involved in the stabilization of VP1 dimers in VLPs and affects their ability to bind to HBGAs. These effects were confirmed in purified HuNoVs. Some VP1 cross-links also take place after free chlorine treatment, albeit to a lesser extent. Not only ONOO⁻ mainly produced VP1 cross-links but can also dissociate VLPs depending on the concentration applied. Nevertheless, ONOO⁻ has less effect on HuNoV particles.

Exploring the use of cellulose nanocrystal as surface-washing agent for oiled shoreline cleanup

Surface-washing agents are an option to enhance the removal of oil spilled or stranded on shorelines. The use of nanocellulose-based nanofluid as a surface-washing agent was studied by investigating its reactivity and effectiveness. Salinity was found to be the most influencial factor to facilitate oil removal with the nanofluids. Cations from salt can promote the adsorption of nanocellulose on the oil/water interface by reducing the surface charges. The experimental results revealed the nanocellulose could be effective at low concentrations but an excess of nanocellulose hindered oil removal due to an increase in fluid viscosity. A miscibility model was applied to verify this finding in a thermodynamics context. The biotoxicity tests showed that nanocellulose-based nanofluid did not have negative effects on algae growth and introducing nanocellulose into an oiled culture medium can actually mitigate the toxicity of the oil on algae. A comparison in removal efficiency with other surfactants demonstrated the potential value for shoreline cleanup due to the superior effectiveness of nanocellulose-based nanofluids. Overall, a nanocellulose has a high potential for application as a surface-washing agent for shoreline cleanup due to the low cost, low toxicity, and high efficiency.

Interaction between norovirus and Histo-Blood Group Antigens: A key to understanding virus transmission and inactivation through treatments?

Human noroviruses (HuNoVs) are a main cause of acute gastroenteritis worldwide. They are frequently involved in foodborne and waterborne outbreaks. Environmental transmission of the virus depends on two main factors: the ability of viral particles to remain infectious and their adhesion capacity onto different surfaces. Until recently, adhesion of viral particles to food matrices was mainly investigated by considering non-specific interactions (e.g. electrostatic, hydrophobic) and there was only limited information about infectious HuNoVs because of the absence of a reliable in vitro HuNoV cultivation system. Many HuNoV strains have now been described as having specific binding interactions with human Histo-Blood Group Antigens (HBGAs) and non-HBGA ligands found in food and the environment. Relevant approaches to the in vitro replication of HuNoVs were also proposed recently. On the basis of the available literature data, this review discusses the opportunities to use this new knowledge to obtain a better understanding of HuNoV transmission to human populations and better evaluate the hazard posed by HuNoVs in foodstuffs and the environment.

Fecal Components Modulate Human Astrovirus Infectivity in Cells and Reconstituted Intestinal Tissues

To ensure transmission, enteric viruses must maintain their infectivity during the various environmental challenges that they face in transit within and between hosts. Increased knowledge of the factors affecting enteric virus survival may help to control their transmission. This study reveals that specific fecal bacterial components preserve classic human astrovirus infectivity by stabilizing viral particles. However, the outcomes of stool-virus interactions are very variable, ranging from protection to a reduction of viral infectivity, depending on the viral genotype and the individual from whom the stool has been collected. We show that the transmissibility of enteric viruses is dependent on the intestinal contents of the infected individual and highlight the complex multiple interactions that could explain the stochastic nature of enteric virus transmission in humans.

Human astroviruses (HAstV) are among the most common causative agents of viral gastroenteritis, especially in children, and extraintestinal manifestations have also been described. These viruses are transmitted by the fecal-oral route, implying that stool composition and the gut microbiota may impact their ability to remain infectious. For some enteric viruses, individual bacterial envelope components and other polysaccharide-containing molecules, which are abundant in stools, have been shown to enhance capsid stability. However, the role of the complex stool environment and, most importantly, the role of interindividual differences have been poorly studied. We used HAstV as a model to investigate how the stool environment in itself, its interindividual variability, and some specific stool components could affect HAstV stability and infectivity. Using two different HAstV genotypes, we found that stools as a whole modulate astrovirus infectivity not only in an individual-dependent manner but also in a manner that depends on the viral genotype. A virus-protective effect was observed after incubation with various Gram-positive and Gram-negative bacteria as well as with bacterial components, such as lipopolysaccharide and peptidoglycan. These results were further confirmed in human intestinal tissues, a more physiologically relevant system. Astrovirus infectivity was also preserved by mucin, a major component of intestinal mucus. We further confirmed that these components stabilize the viral capsid. These results show that although HAstV benefits from the stabilizing effect of fecal components, the complexity and variability of the stool composition and the multiple potential interactions may explain the interindividual differences in viral transmission observed in real life.

IMPORTANCE To ensure transmission, enteric viruses must maintain their infectivity during the various environmental challenges that they face in transit within and between hosts. Increased knowledge of the factors affecting enteric virus survival may help to control their transmission. This study reveals that specific fecal bacterial components preserve classic human astrovirus infectivity by stabilizing viral particles. However, the outcomes of stool-virus interactions are very variable, ranging from protection to a reduction of viral infectivity, depending on the viral genotype and the individual from whom the stool has been collected. We show that the transmissibility of enteric viruses is dependent on the intestinal contents of the infected individual and highlight the complex multiple interactions that could explain the stochastic nature of enteric virus transmission in humans.

Effect of natural ageing and heat treatments on GII.4 norovirus binding to Histo-Blood Group Antigens

Human noroviruses (HuNoVs) are the leading cause of viral foodborne outbreaks worldwide. To date, no available methods can be routinely used to detect infectious HuNoVs in foodstuffs. HuNoVs recognize Histo-Blood Group Antigens (HBGAs) through the binding pocket (BP) of capsid protein VP1, which promotes infection in the host cell. In this context, the suitability of human HBGA-binding assays to evaluate the BP integrity of HuNoVs was studied on GII.4 virus-like particles (VLPs) and GII.4 HuNoVs during natural ageing at 20 °C and heat treatments. Our results demonstrate that this approach may reduce the over-estimation of potential infectious HuNoVs resulting from solely using the genome detection, even though some limitations have been identified. The specificity of HBGA-binding to the BP is clearly dependent on the HGBA type (as previously evidenced) and the ionic strength of the media without disturbing such interactions. This study also provides new arguments regarding the ability of VLPs to mimic HuNoV behavior during inactivation treatments. The BP stability of VLPs was at least 4.3 fold lower than that of HuNoVs at 20 °C, whereas capsids of both particles were disrupted at 72 °C. Thus, VLPs are relevant surrogates of HuNoVs for inactivation treatments inducing significant changes in the capsid structure.

The impact of chlorine and heat on the infectivity and physicochemical properties of bacteriophage MS2

Enteric viruses and bacteriophages are exposed to various inactivating factors outside their host, and among them chlorine and heat are the most commonly used sanitizer in water industry and treatment in the food industry, respectively. Using MS2 phages as models for enteric viruses, we investigated the impact of free chlorine and heat on their physicochemical properties. Free chlorine was first evaluated alone. No increase in either capsid permeability or hydrophobicity was observed. The negative surface charge slightly increased suggesting molecular changes in the capsid. However, a weakening of the capsid by chlorine was suggested by differential scanning fluorimetry. This phenomenon was confirmed when chlorination was followed by a heat treatment. Indeed, an increase in the inactivation of MS2 phages and the permeability of their capsids to RNases was observed. More interestingly, an increase in the expression of hydrophobic domains at the phage surface was observed, but only for phages remaining infectious. The chlorine-caused weakening of the capsid suggested that, for an optimal use, the oxidant should be followed by heat. The increased permeability to RNases and the expression of hydrophobic domains may contribute to the development or improvement of molecular methods specific for infectious enteric viruses.

Detection of Human Enteric Viruses in French Polynesian Wastewaters, Environmental Waters and Giant Clams

Lack of wastewater treatment efficiency causes receiving seawaters and bivalve molluscan shellfish to become contaminated, which can lead to public health issues. Six wastewater samples, five seawater samples and three batches of giant clams from Tahiti (French Polynesia) were investigated for the presence of enteric viruses, but also if present, for the diversity, infectivity and integrity of human adenoviruses (HAdV). Enteroviruses (EV), sapoviruses (SaV) and human polyomaviruses (HPyV) were detected in all wastewater samples. In decreasing frequency, noroviruses (NoV) GII and HAdV, rotaviruses (RoV), astroviruses (AsV), NoV GI and finally hepatitis E viruses (HEV) were also observed. Nine types of infectious HAdV were identified. HPyV and EV were found in 80% of seawater samples, NoV GII in 60%, HAdV and SaV in 40% and AsV and RoV in 20%. NoV GI and HEV were not detected in seawater. Intact and infectious HAdV-41 were detected in one of the two seawater samples that gave a positive qPCR result. Hepatitis A viruses were never detected in any water types. Analysis of transcriptomic data from giant clams revealed homologues of fucosyltransferases (FUT genes) involved in ligand biosynthesis that strongly bind to certain NoV strains, supporting the giant clams ability to bioaccumulate NoV. This was confirmed by the presence of NoV GII in one of the three batches of giant clams placed in a contaminated marine area. Overall, all sample types were positive for at least one type of virus, some of which were infectious and therefore likely to cause public health concerns.

Insights into Long-Term Toxicity of Triclosan to Freshwater Green Algae in Lake Erie

This study explored the long-term impacts of a pulse disturbance of triclosan on five nontarget green algae in Lake Erie. Comprehensive analyses were performed using multiple physiological end points at community and subcellular scales. The toxic mechanism of triclosan in a wide range of concentrations was analyzed. The diverse sensitivity of algae species and complex interrelationships among multiple end points were revealed. The results showed the taxonomic groups of algae were the key issue for sensitivity difference. High doses of triclosan caused irreversible damage on algae, and environmentally relevant doses initiated either inhibition or stimulation. Smaller cells had higher sensitivity to triclosan, while larger cells had a wider size variation after exposure. Colonial cells were less sensitive than unicells. For chlorophyll, there were better dose-response relationships in Chlorococcum sp., Chlamydomonas reinhardtii CPCC 12 and 243 than Asterococcus superbus and Eremosphaera viridis. For chlorophyll fluorescence, F_v/ F_m was the most sensitive parameter, and q_N was more sensitive than q_P. Triclosan showed long-term effects on biochemical components, such as lipids, proteins, and nucleic acids. The findings will be helpful for a systematic and complete assessment of triclosan toxicity in natural waters and the development of appropriate strategies for its risk management.

Irrigating Lettuce with Wastewater Effluent: Does Disinfection with Chlorine Dioxide Inactivate Viruses?

Reclaimed water obtained from urban wastewater is currently being used as irrigation water in water-scarce regions in Spain. However, wastewater can contain enteric viruses that water reclamation treatment cannot remove or inactivate completely. In the present study, greenhouse-grown baby lettuce ( L.) was irrigated with secondary treatment effluent from a wastewater treatment plant untreated and treated using chlorine dioxide (ClO). The effect of ClO treatment on the physicochemical characteristics and the presence of enteric viruses in irrigation water and lettuce was assessed. The presence of human noroviruses genogroups I and II (NoV GI and NoV GII), and human astroviruses (HAstV), was analyzed by real-time polymerase chain reaction (RT-qPCR). Additionally, to check for the loss of infectivity induced by the disinfection treatment, positive samples were re-analyzed after pretreatment with the intercalating dye PMAxx before RNA extraction and RT-qPCR. There were no significant differences in the proportion of positive samples and the concentration of enteric viruses between treated and untreated reclaimed water without PMAxx pretreatment ( > 0.05). A significantly lower concentration of NoV GI was detected in ClO-treated water when samples were pretreated with PMAxx ( < 0.05), indicating that inactivation was due to the disinfection treatment. Laboratory-scale validation tests indicated the suitability of PMAxx-RT-qPCR for discrimination between potentially infectious and ClO-damaged viruses. Although the applied ClO treatment was not able to significantly reduce the enteric virus load of the secondary effluent from the wastewater treatment plant, none of the lettuce samples analyzed ( = 36) was positive for the presence of NoV or HAstV.

Effect of the Shellfish Proteinase K Digestion Method on Norovirus Capsid Integrity

Norovirus outbreaks are associated with the consumption of contaminated shellfish, and so efficient methods to recover and detect infectious norovirus in shellfish are important. The Proteinase K digestion method used to recover norovirus from shellfish, as described in the ISO 15216, would be a good candidate but its impact on the virus capsid integrity and thus infectivity was never examined. The aim of this study was to assess the impact of the Proteinase K digestion method, and of the heat treatment component of the method alone, on norovirus (genogroups I and II) and MS2 bacteriophage capsid integrity. A slightly modified version of the ISO method was used. RT-qPCR was used for virus detection following digestion of accessible viral RNA using RNases. MS2 phage infectivity was measured using a plaque assay. The effect of shellfish digestive glands (DG) on recovery was evaluated. In the presence of shellfish DG, a reduction in MS2 phage infectivity of about 1 log₁₀ was observed after the Proteinase K digestion method and after heat treatment component alone. For norovirus GII and MS2 phage, there was no significant loss of genome following the Proteinase K digestion method but there was a significant 0.24 log₁₀ loss of norovirus GI. In the absence of shellfish DG, the reduction in MS2 phage infectivity was about 2 log₁₀, with the addition of RNases resulting in a significant loss of genome for all tested viruses following complete Proteinase K digestion method and the heat treatment alone. While some protective effect from the shellfish DG on viruses was observed, the impact on capsid integrity and infectivity suggests that this method, while suitable for norovirus genome detection, may not completely preserve virus infectivity.

A review on recent progress in the detection methods and prevalence of human enteric viruses in water

Waterborne human enteric viruses, such as noroviruses and adenoviruses, are excreted in the feces of infected individuals and transmitted via the fecal-oral route including contaminated food and water. Since viruses are normally present at low concentrations in aquatic environments, they should be concentrated into smaller volumes prior to downstream molecular biological applications, such as quantitative polymerase chain reaction (qPCR). This review describes recent progress made in the development of concentration and detection methods of human enteric viruses in water, and discusses their applications for providing a better understanding of the prevalence of the viruses in various types of water worldwide. Maximum concentrations of human enteric viruses in water that have been reported in previous studies are summarized to assess viral abundances in aquatic environments. Some descriptions are also available on recent applications of sequencing analyses used to determine the genetic diversity of viral genomes in water samples, including those of novel viruses. Furthermore, the importance and significance of utilizing appropriate process controls during viral analyses are discussed, and three types of process controls are considered: whole process controls, molecular process controls, and (reverse transcription (RT)-)qPCR controls. Although no standards have been established for acceptable values of virus recovery and/or extraction-(RT-)qPCR efficiency, use of at least one of these appropriate control types is highly recommended for more accurate interpretation of observed data.

Efficacy of Neutral Electrolyzed Water for Inactivation of Human Norovirus

Human norovirus (NoV) is the leading cause of acute gastroenteritis worldwide. Persistence on surfaces and resistance to many conventional disinfectants contribute to widespread transmission of norovirus. We examined the efficacy of neutral electrolyzed water (NEW; pH 7) for inactivation of human NoV GII.4 Sydney in suspension (ASTM method 1052-11) and on stainless steel surfaces (ASTM method 1053-11) with and without an additional soil load. The impact of the disinfectant on viral capsid was assessed using reverse transcriptase quantitative PCR (RT-qPCR; with an RNase pretreatment), SDS-PAGE, transmission electron microscopy, and a histo-blood group antigen (HBGA) receptor-binding assay. These studies were done in parallel with those using Tulane virus (TuV), a cultivable human NoV surrogate. Neutral electrolyzed water at 250 ppm free available chlorine produced a 4.8- and 0.4-log10 reduction in NoV genome copy number after 1 min in suspension and on stainless steel, respectively. Increasing the contact time on surfaces to 5, 10, 15, and 30 min reduced human NoV genomic copies by 0.5, 1.6, 2.4, and 5.0 log10 and TuV infectious titers by 2.4, 3.0, 3.8, and 4.1 log10 PFU, respectively. Increased soil load effectively eliminated antiviral efficacy regardless of testing method and virus. Exposure to NEW induced a near complete loss of receptor binding (5 ppm, 30 s), degradation of VP1 major capsid protein (250 ppm, 5 min), and increased virus particle aggregation (150 ppm, 30 min). Neutral electrolyzed water at 250 ppm shows promise as an antinoroviral disinfectant when used on precleaned stainless steel surfaces.IMPORTANCE Norovirus is the leading cause of acute viral gastroenteritis worldwide. Transmission occurs by fecal-oral or vomitus-oral routes. The persistence of norovirus on contaminated environmental surfaces exacerbates its spread, as does its resistance to many conventional disinfectants. The purpose of this research was to evaluate the antinoroviral efficacy of neutral electrolyzed water (NEW), a novel chlorine-based disinfectant that can be used at reduced concentrations, making it more environmentally friendly and less corrosive than bleach. An industrial-scale electrochemical activation device capable of producing relatively stable electrolyzed water at a wide pH range was used in this study. Experiments showed that 250 ppm NEW effectively eliminated (defined as a 5-log10 reduction) human norovirus GII.4 Sydney (epidemic strain) on clean stainless steel surfaces after a 30-min exposure. Supporting studies showed that, like bleach, NEW causes inactivation by disrupting the virus capsid. This product shows promise as a bleach alternative with antinoroviral efficacy.

Molecular toxicity of triclosan and carbamazepine to green algae Chlorococcum sp.: A single cell view using synchrotron-based Fourier transform infrared spectromicroscopy

Although pharmaceuticals and personal care products have been used and introduced into the environment in large quantities, little information on potential ecological risks is currently available considering their effects on living organisms. We verified the feasibility of using synchrotron-based Fourier Transform Infrared (SR-FTIR) spectromicroscopy to explore in vivo toxic effects on single living Chlorococcum sp. cells. The study provided important information to achieve a better understanding of the toxic mechanism of triclosan and carbamazepine on living algae Chlorococcum sp.. Triclosan and carbamazepine had distinctive toxic effects on unicellular living algae. Most strikingly, triclosan had more dramatic toxic effects on biochemical components than carbamazepine. Triclosan can affect algae primarily by inhibiting fatty acid synthesis and causing protein aggregation. The toxicity response was irreversible at higher concentration (100.000 μM), but attenuated at lower concentration (0.391 μM) as time extended. Carbamazepine can produce hydrophobic interactions to affect the phospholipid bilayer and work on specific proteins to disfunction the cell membrane. Carbamazepine-exposed cells developed a resistance while extending exposure time. This is the first demonstration from an ecological standpoint that SR-FTIR can provide an innovative approach to reveal the toxicity of emerging pollutants in aquatic environments.

The Effect of Heat and Free Chlorine Treatments on the Surface Properties of Murine Norovirus

Heat and free chlorine are among the most efficient and commonly used treatments to inactivate enteric viruses, but their global inactivation mechanisms have not been elucidated yet. These treatments have been shown to affect at least the capsid proteins of viruses and thus may affect the surface properties (i.e. electrostatic charge and hydrophobicity) of such particles. Our aim was to study the effects of heat and free chlorine on surface properties for a murine norovirus chosen as surrogate for human norovirus. No changes in the surface properties were observed with our methods for murine norovirus exposed to free chlorine. Only the heat treatment led to major changes in the surface properties of the virus with the expression of hydrophobic domains at the surface of the particles after exposure to a temperature of 55 °C. No modification of the expression of hydrophobic domains occurred after exposure to 60 °C, and the low hydrophobic state exhibited by infectious and inactivated particles after exposure to 60 °C appeared to be irreversible for inactivated particles only, which may provide a means to discriminate infectious from inactivated murine noroviruses. When exposed to a temperature of 72 °C or to free chlorine at a concentration of 50 mg/L, the genome became available for RNases.

Comparative Inactivation of Murine Norovirus and MS2 Bacteriophage by Peracetic Acid and Monochloramine in Municipal Secondary Wastewater Effluent

Chlorination has long been used for disinfection of municipal wastewater (MWW) effluent while the use peracetic acid (PAA) has been proposed more recently in the United States. Previous work has demonstrated the bactericidal effectiveness of PAA and monochloramine in wastewater, but limited information is available for viruses, especially ones of mammalian origin (e.g., norovirus). Therefore, a comparative assessment was performed of the virucidal efficacy of PAA and monochloramine against murine norovirus (MNV) and MS2 bacteriophage in secondary effluent MWW and phosphate buffer (PB). A suite of inactivation kinetic models was fit to the viral inactivation data. Predicted concentration-time (CT) values for 1-log₁₀ MS2 reduction by PAA and monochloramine in MWW were 1254 and 1228 mg-min/L, respectively. The 1-, 2-, and 3-log₁₀ model predicted CT values for MNV viral reduction in MWW were 32, 47, and 69 mg-min/L for PAA and 6, 13, and 28 mg-min/L for monochloramine, respectively. Wastewater treatment plant disinfection practices informed by MS2 inactivation data will likely be protective for public health but may overestimate CT values for reduction of MNV. Additionally, equivalent CT values in PB resulted in greater viral reduction which indicate that viral inactivation data in laboratory grade water may not be generalizable to MWW applications.

Curcumin-Mediated Photodynamic Inactivation of Norovirus Surrogates

Photodynamic inactivation (PDI) is extensively used to inactivate different type of pathogens through the use of photosensitizers (PS). Curcumin has been identified as an excellent natural photosensitizer with some potential applications in the food industry. The aim of this study was to assess the antiviral activity of photoactivated curcumin on norovirus surrogates, feline calicivirus (FCV), and murine norovirus (MNV). Initially, different concentrations of curcumin (13.5-1358 µM) were individually mixed with each virus at titers of ca. 6-7 log TCID₅₀/ml and photoactivated by LED blue light with light dose of 3 J/cm². Results showed that photoactivated curcumin at 50 µg/mL reduced FCV titers by almost 5 log after incubation at 37 °C for 30 min. Lower antiviral activity (0.73 log TCID₅₀/mL reduction) was reported for MNV. At room temperature, curcumin at 5 µg/mL reduced FCV titers by 1.75 log TCID₅₀/mL. These results represent a step forward in improving food safety using photoactivated curcumin as an alternative natural additive to reduce viral contamination.

Arc discharge-mediated disassembly of viral particles in water

In this study, we investigated the inactivation effects on murine norovirus (MNV-1) with/without purification in water using a submerged plasma reactor of arc discharge (underwater arc), which produced a shockwave, UV light, reactive oxygen species and reactive nitrogen species. Underwater arc treatments of 3 and 6 Hz at 12 kV resulted in 2.6- and 4.2-log reductions in the virus titer of non-purified MNV-1 after 1 min of treatment, respectively. The reduction of purified MNV-1 was higher than that of non-purified MNV-1 after underwater arc treatment for all applied conditions (12 or 15 kV and 3 or 6 Hz). One of the viral capsid proteins (VP1) was not detectable after underwater arc treatment, when its integrity was assessed by western blot analysis. Transmission electron microscopy analysis also revealed that MNV-1 particles were completely dissembled by the treatment. This study demonstrates that underwater arc treatment, which was capable of disintegrating the MNV-1 virion structure and the viral capsid protein, can be an effective disinfection process for the inactivation of water-borne noroviruses.

Impact of reducing and oxidizing agents on the infectivity of Qβ phage and the overall structure of its capsid

Qβ phages infect Escherichia coli in the human gut by recognizing F-pili as receptors. Infection therefore occurs under reducing conditions induced by physiological agents (e.g. glutathione) or the intestinal bacterial flora. After excretion in the environment, phage particles are exposed to oxidizing conditions and sometimes disinfection. If inactivation does not occur, the phage may infect new hosts in the human gut through the oral route. During such a life cycle, we demonstrated that, outside the human gut, cysteines of the major protein capsid of Qβ phage form disulfide bonds. Disinfection with NaClO does not allow overoxidation to occur. Such oxidation induces inactivation rather by irreversible damage to the minor proteins. In the presence of glutathione, most disulfide bonds are reduced, which slightly increases the capacity of the phage to infect E. coli in vitro Such reduction is reversible and barely alters infectivity of the phage. Reduction of all disulfide bonds by dithiothreitol leads to complete capsid destabilization. These data provide new insights into how the phages are impacted by oxidizing-reducing conditions outside their host cell and raises the possibility of the intervention of the redox during life cycle of the phage.

Persistence and Elimination of Human Norovirus in Food and on Food Contact Surfaces: A Critical Review

This critical review addresses the persistence of human norovirus (NoV) in water, shellfish, and processed meats; on berries, herbs, vegetables, fruits, and salads; and on food contact surfaces. The review focuses on studies using NoV; information from studies involving only surrogates is not included. It also addresses NoV elimination or inactivation by various chemical, physical, or processing treatments. In most studies, persistence or elimination was determined by detection and quantification of the viral genome, although improved methods for determining infectivity have been proposed. NoV persisted for 60 to 728 days in water, depending on water source. It also persisted on berries, vegetables, and fruit, often showing <1-log reduction within 1 to 2 weeks. NoV was resilient on carpets, Formica, stainless steel, polyvinyl chloride, and ceramic surfaces; during shellfish depuration; and to repeated freeze-thaw cycles. Copper alloy surfaces may inactivate NoV by damaging viral capsids. Disinfection was achieved for some foods or food contact surfaces using chlorine, calcium or sodium hypochlorite, chlorine dioxide, high hydrostatic pressure, high temperatures, pH values >8.0, freeze-drying, and UV radiation. Ineffective disinfectants included hydrogen peroxide, quaternary ammonium compounds, most ethanol-based disinfectants, and antiseptics at normally used concentrations. Thorough washing of herbs and produce was effective in reducing, but not eliminating, NoV in most products. Washing hands with soap generally reduced NoV by <2 log. Recommendations for future research needs are provided.

Human norovirus as a foodborne pathogen: challenges and developments

Human noroviruses (NoVs) are the leading cause of foodborne illness in the United States, and they exact a considerable human and economic burden worldwide. In fact, the many challenging aspects of human NoV have caused some to call it the nearly perfect foodborne pathogen. In this review, a brief overview of NoVs and their genetic structure is provided. Additionally, the challenges and recent developments related to human NoVs regarding viral evolution, transmission, epidemiology, outbreak identification, cultivation, animal and human models, and detection are presented.

Type I interferon response is delayed in human astrovirus infections

Type I interferon (IFN) activation and its subsequent effects are important in the response to viral infections. Here we show that human astroviruses (HAstVs), which are important agents of acute gastroenteritis in children, induce a mild and delayed IFN response upon infecting CaCo-2 cells. Although IFN-β mRNA is detected within infected cells and supernatant from infected cells show antiviral activity against the replication of other well-known IFN-sensitive viruses, these responses occur at late stages of infection once genome replication has taken place. On the other hand, HAstV replication can be partially reduced by the addition of exogenous IFN, and inhibition of IFN activation by BX795 enhances viral replication, indicating that HAstVs are IFN-sensitive viruses. Finally, different levels of IFN response were observed in cells infected with different HAstV mutants with changes in the hypervariable region of nsP1a/4, suggesting that nsP1a/4 genotype may potentially have clinical implications due to its correlation with the viral replication phenotype and the antiviral responses induced within infected cells.

Culture-independent evaluation of nonenveloped-virus infectivity reduced by free-chlorine disinfection

The inability of molecular detection methods to distinguish disinfected virions from infectious ones has hampered the assessment of infectivity for enteric viruses caused by disinfection practices. In the present study, the reduction of infectivity of murine norovirus S7-PP3 and mengovirus vMC0, surrogates of human noroviruses and enteroviruses, respectively, caused by free-chlorine treatment was characterized culture independently by detecting carbonyl groups on viral capsid protein. The amount of carbonyls on viral capsid protein was evaluated by the proportion of biotinylated virions trapped by avidin-immobilized gel (percent adsorbed). This culture-independent approach demonstrated that the percent adsorbed was significantly correlated with the logarithm of the infectious titer of tested viruses. Taken together with the results of previous reports, the result obtained in this study indicates that the amount of carbonyls on viral capsid protein of four important families of waterborne pathogenic viruses, Astroviridae, Reoviridae, Caliciviridae, and Picornaviridae, is increased in proportion to the received oxidative stress of free chlorine. There was also a significant correlation between the percent adsorbed and the logarithm of the ratio of genome copy number to PFU, which enables estimation of the infectious titer of a subject virus by measuring values of the total genome copy number and the percent adsorbed. The proposed method is applicable when the validation of a 4-log reduction of viruses, a requirement in U.S. EPA guidelines for virus removal from water, is needed along with clear evidence of the oxidation of virus particles with chlorine-based disinfectants.

Relative insignificance of virus inactivation during aluminum electrocoagulation of saline waters

Combined removal and inactivation of the MS2 bacteriophage from model saline (0-100 mM NaCl) waters by electrochemical treatment using a sacrificial aluminum anode was evaluated. Both chemical and electrodissolution contributed to coagulant dosing since measured aluminum concentrations were statistically higher than purely electrochemical predictions using Faraday's law. Electrocoagulation generated only small amounts of free chlorine in situ but effectively destabilized viruses and incorporated them into Al(OH)3(s) flocs during electrolysis. Low chlorine concentrations combined with virus shielding and aggregation within flocs resulted in very slow disinfection rates necessitating extended flocculation/contact times to achieve significant log-inactivation. Therefore, the dominant virus control mechanism during aluminum electrocoagulation of saline waters is "physical" removal by uptake onto flocs rather than "chemical" inactivation by chlorine. Attenuated total reflectance-Fourier transform infrared spectroscopy provided evidence for oxidative transformations of capsid proteins including formation of oxyacids, aldehydes, and ketones. Electrocoagulation significantly altered protein secondary structures decreasing peak areas associated with turns, bends, α-helices, β-structures, and random coils for inactivated viruses compared with the MS2 stock. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) measurements showed rapid initial RNA damage following a similar trend as plaque assay measurements of infectious viruses. However, ssRNA cleavage measured by qRT-PCR underestimated inactivation over longer durations. Although aluminum electrocoagulation of saline waters disorders virus capsids and damages RNA, inactivation occurs at a sufficiently low rate so as to only play a secondary role to floc-encapsulation during residence times typical of electrochemical treatment.

UVC Inactivation of dsDNA and ssRNA Viruses in Water: UV Fluences and a qPCR-Based Approach to Evaluate Decay on Viral Infectivity

Disinfection by low-pressure monochromatic ultraviolet (UVC) radiation (253.7 nm) became an important technique to sanitize drinking water and also wastewater in tertiary treatments. In order to prevent the transmission of waterborne viral diseases, the analysis of the disinfection kinetics and the quantification of infectious viral pathogens and indicators are highly relevant and need to be addressed. The families Adenoviridae and Polyomaviridae comprise human and animal pathogenic viruses that have been also proposed as indicators of fecal contamination in water and as Microbial Source Tracking tools. While it has been previously suggested that dsDNA viruses may be highly resistant to UVC radiation compared to other viruses or bacteria, no information is available on the stability of polyomavirus toward UV irradiation. Here, the inactivation of dsDNA (HAdV2 and JCPyV) and ssRNA (MS2 bacteriophage) viruses was analyzed at increasing UVC fluences. A minor decay of 2-logs was achieved for both infectious JC polyomaviruses (JCPyV) and human adenoviruses 2 (HAdV2) exposed to a UVC fluence of 1,400 J/m(2), while a decay of 4-log was observed for MS2 bacteriophages (ssRNA). The present study reveals the high UVC resistance of dsDNA viruses, and the UV fluences needed to efficiently inactivate JCPyV and HAdV2 are predicted. Furthermore, we show that in conjunction with appropriate mathematical models, qPCR data may be used to accurately estimate virus infectivity.

Human astroviruses

Human astroviruses (HAtVs) are positive-sense single-stranded RNA viruses that were discovered in 1975. Astroviruses infecting other species, particularly mammalian and avian, were identified and classified into the genera Mamastrovirus and Avastrovirus. Through next-generation sequencing, many new astroviruses infecting different species, including humans, have been described, and the Astroviridae family shows a high diversity and zoonotic potential. Three divergent groups of HAstVs are recognized: the classic (MAstV 1), HAstV-MLB (MAstV 6), and HAstV-VA/HMO (MAstV 8 and MAstV 9) groups. Classic HAstVs contain 8 serotypes and account for 2 to 9% of all acute nonbacterial gastroenteritis in children worldwide. Infections are usually self-limiting but can also spread systemically and cause severe infections in immunocompromised patients. The other groups have also been identified in children with gastroenteritis, but extraintestinal pathologies have been suggested for them as well. Classic HAstVs may be grown in cells, allowing the study of their cell cycle, which is similar to that of caliciviruses. The continuous emergence of new astroviruses with a potential zoonotic transmission highlights the need to gain insights on their biology in order to prevent future health threats. This review focuses on the basic virology, pathogenesis, host response, epidemiology, diagnostic assays, and prevention strategies for HAstVs.

Application of long-range and binding reverse transcription-quantitative PCR to indicate the viral integrities of noroviruses

This study intends to establish and apply methods evaluating both viral capsid and genome integrities of human noroviruses (NoVs), which thus far remain nonculturable. Murine norovirus 1 (MNV-1) and human NoV GII.4 in phosphate-buffered saline suspensions were treated with heat, UV light, or ethanol and detected by reverse transcription-quantitative PCR (RT-qPCR), long-range RT-qPCR, binding RT-qPCR, and binding long-range RT-qPCR. For MNV-1 heated at 60°C for 2 and 30 min, limited reductions of genomic copies (<0.3-log) were obtained by RT-qPCR and long-range RT-qPCR, while the cell-binding pretreatments obtained higher reductions (>1.89-log reduction after 60°C for 30 min by binding long-range RT-qPCR). The human NoV GII.4 was found to be more heat resistant than MNV-1. For both MNV-1 and human NoV GII.4 after UV treatments of 20 and 200 mJ/cm(2), no significant difference (P > 0.05) was observed between the dose-dependent reductions obtained by the four detection methodologies. Treatment of 70% ethanol for 1 min was shown to be more effective for inactivation of both MNV-1 and human NoV GII.4 than the heat and UV treatments used in this study. Subsequently, eight raspberry and four shellfish samples previously shown to be naturally contaminated with human NoVs by RT-qPCR (GI and GII; thus, 24 RT-qPCR signals) were subjected to comparison by this method. RT-qPCR, long-range RT-qPCR, binding RT-qPCR, and binding long-range RT-qPCR detected 20/24, 14/24, 24/24, and 23/24 positive signals, respectively, indicating the abundant presence of intact NoV particles.

Fluorinated TiO₂ as an ambient light-activated virucidal surface coating material for the control of human norovirus

We evaluated the virucidal efficacy of light-activated fluorinated TiO₂ surface coatings on human norovirus and several surrogates (bacteriophage MS2, feline calcivirus (FCV), and murine norovirus (MNV)). Inactivation of viruses on surfaces exposed to a common fluorescent lamp was monitored and the effects of UVA intensity, temperature, and fluoride content were assessed. Destruction of RNA and capsid oxidation were evaluated for human norovirus inocula on the F-TiO₂ surfaces, while contact with the F-TiO₂ surface and exposure to residual UVA radiation of 10 μW cm(-2) for 60 min resulted in infectivity reductions for the norovirus surrogates of 2-3 log₁₀. Infectivity reductions on pristine TiO₂ surfaces in identical conditions were over 2 orders of magnitude lower. Under realistic room lighting conditions, MS2 infectivity declined below the lower detection limit after 12h. Reductions in RNA were generally low, with the exception of GII.4, while capsid protein oxidation likely played a larger role in infectivity loss. Inactivation of norovirus surrogates occurred significantly faster on F-TiO₂ compared to pristine TiO₂ surfaces. The material demonstrated antiviral action against human norovirus surrogates and was shown to effectively inhibit MS2 when exposed to residual UVA present in fluorescent room lighting conditions in a laboratory setting.

Effect of metal catalyzed oxidation in recombinant viral protein assemblies

Background

Protein assemblies, such as virus-like particles, have increasing importance as vaccines, delivery vehicles and nanomaterials. However, their use requires stable assemblies. An important cause of loss of stability in proteins is oxidation, which can occur during their production, purification and storage. Despite its importance, very few studies have investigated the effect of oxidation in protein assemblies and their structural units. In this work, we investigated the role of in vitro oxidation in the assembly and stability of rotavirus VP6, a polymorphic protein.

Results

The susceptibility to oxidation of VP6 assembled into nanotubes (VP6_NT) and unassembled VP6 (VP6_U) was determined and compared to bovine serum albumin (BSA) as control. VP6 was more resistant to oxidation than BSA, as determined by measuring protein degradation and carbonyl content. It was found that assembly protected VP6 from in vitro metal-catalyzed oxidation. Oxidation provoked protein aggregation and VP6_NT fragmentation, as evidenced by dynamic light scattering and transmission electron microscopy. Oxidative damage of VP6 correlated with a decrease of its center of fluorescence spectral mass. The in vitro assembly efficiency of VP6_U into VP6_NT decreased as the oxidant concentration increased.

Conclusions

Oxidation caused carbonylation, quenching, and destruction of aromatic amino acids and aggregation of VP6 in its assembled and unassembled forms. Such modifications affected protein functionality, including its ability to assemble. That assembly protected VP6 from oxidation shows that exposure of susceptible amino acids to the solvent increases their damage, and therefore the protein surface area that is exposed to the solvent is determinant of its susceptibility to oxidation. The inability of oxidized VP6 to assemble into nanotubes highlights the importance of avoiding this modification during the production of proteins that self-assemble. This is the first time that the role of oxidation in protein assembly is studied, evidencing that oxidation should be minimized during the production process if VP6 nanotubes are required.

Virus inactivation mechanisms: impact of disinfectants on virus function and structural integrity

Oxidative processes are often harnessed as tools for pathogen disinfection. Although the pathways responsible for bacterial inactivation with various biocides are fairly well understood, virus inactivation mechanisms are often contradictory or equivocal. In this study, we provide a quantitative analysis of the total damage incurred by a model virus (bacteriophage MS2) upon inactivation induced by five common virucidal agents (heat, UV, hypochlorous acid, singlet oxygen, and chlorine dioxide). Each treatment targets one or more virus functions to achieve inactivation: UV, singlet oxygen, and hypochlorous acid treatments generally render the genome nonreplicable, whereas chlorine dioxide and heat inhibit host-cell recognition/binding. Using a combination of quantitative analytical tools, we identified unique patterns of molecular level modifications in the virus proteins or genome that lead to the inhibition of these functions and eventually inactivation. UV and chlorine treatments, for example, cause site-specific capsid protein backbone cleavage that inhibits viral genome injection into the host cell. Combined, these results will aid in developing better methods for combating waterborne and foodborne viral pathogens and further our understanding of the adaptive changes viruses undergo in response to natural and anthropogenic stressors.