Efficacy of an antimicrobial surface coating against human coronavirus 229E and SARS-CoV-2.

The COVID-19 pandemic has accelerated the demand for alternatives to standard cleaning and disinfection practices. Antiviral coatingsmay provide an alternative to common surface treatments. A newly developed quaternary ammonium polymer coating was applied to stainless steel coupons and evaluated for efficacy against human coronavirus 229E and SARS-CoV-2. The polymer coating reduced levels of both test viruses by greater than 99.9% relative to non-coated stainless steel coupons during a 2-hour contact time.

Relationship Between Inactivation and Genome Damage of Human Enteroviruses Upon Treatment by UV254, Free Chlorine, and Ozone.

Quantitative PCR (qPCR) is a convenient tool for monitoring virus concentrations in water and wastewater treatment trains, though it only informs about virus presence, but not infectivity. This limitation can be overcome if the relationship between infectivity loss and genome decay induced by a given disinfectant is known. Here, we performed inactivation experiments using two human enteroviruses, Coxsackievirus B5 and Echovirus 11, with three disinfection methods: low-pressure ultraviolet light (UV254), free chlorine (FC), and ozone. We compared the inactivation rates as measured by culturing to the decay rates of the whole genome, to evaluate the extent of qPCR-measurable genome damage as a function of inactivation. To determine genome damage, we used an approach that estimates damage across the full viral genome from the measured decay of multiple amplicons distributed across the viral genome. Correlations between inactivation and genome decay were observed for all viruses and all disinfection treatments, but results showed that even among closely related viruses, disinfection methods can damage the viral genome to different extents and that genome damage does not necessarily translate to inactivation. For both viruses, UV254 treatment had the closest relationship between inactivation and genome decay and with ozone, the rate of genome decay exceeded the inactivation rate. Finally, for FC, the ratios between methods were vastly different between viruses. This work provides the basis to relate qPCR measurements to infectivity loss and enables the establishment of molecular monitoring tools for assessing enterovirus inactivation during disinfection treatments of water and wastewater.

Differences in Viral Disinfection Mechanisms as Revealed by Quantitative Transfection of Echovirus 11 Genomes.

Virus inactivation mechanisms can be elucidated by methods that measure the loss of specific virus functionality (e.g., host attachment, genome internalization, and genome replication). Genome functionality is frequently assessed by PCR-based methods, which are indirect and potentially inaccurate; genome damage that affects detection by high-fidelity PCR enzymes may not adversely affect the ability of actual cellular enzymes to produce functional virus. Therefore, we developed here a transfection-based assay to quantitatively determine viral genome functionality by inserting viral RNA into host cells directly to measure their ability to produce new functional viruses from damaged viral genomes. Echovirus 11 was treated with ozone, free chlorine (FC), UV light at 254 nm (UV254), or heat, and then the reductions in genome functionality and infectivity were compared. Ozone reduced genome functionality proportionally to infectivity, indicating that genome damage is the main mechanism of virus inactivation. In contrast, FC caused little or no loss of genome functionality compared to infectivity, indicating a larger role for protein damage. For UV254, genome functionality loss accounted for approximately 60% of virus inactivation, with the remainder presumably due to protein damage. Heat treatment resulted in no reduction in genome functionality, in agreement with the understanding that heat inactivation results from capsid damage. Our results indicate that there is a fundamental difference between genome integrity reductions measured by PCR enzymes in previous studies and actual genome functionality (whether the genome can produce virus) after disinfection. Compared to PCR, quantitative transfection assays provide a more realistic picture of actual viral genome functionality and overall inactivation mechanisms during disinfection.IMPORTANCE This study provides a new tool for assessing virus inactivation mechanisms by directly measuring a viral genome's ability to produce new viruses after disinfection. In addition, we identify a potential pitfall of PCR for determining virus genome damage, which does not reflect whether a genome is truly functional. The results presented here using quantitative transfection corroborate previously suggested virus inactivation mechanisms for some virus inactivation methods (heat) while bringing additional insights for others (ozone, FC, and UV254). The developed transfection method provides a more mechanistic approach for the assessment of actual virus inactivation by common water disinfectants.

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.

Highly Efficient Virus Rejection with Self-Organized Membranes Based on a Crosslinked Bicontinuous Cubic Liquid Crystal.

To remove viruses from water, the use of self-assembling liquid crystals is presented as a novel method for the synthesis of membranes with a regular pore size (below 1 nm) and controlled pore structures. Nanostructured bicontinuous cubic liquid-crystalline (LC) thin films are photopolymerized onto a polysulfone support layer. It is found that these membranes reject the virus, Qß bacteriophage (≈20 nm diameter) by >99.9999%. Prepressurization of the membrane appears to enhance their virus rejection properties. This is the first example of nanostructured LC membranes that are used for virus rejection, for which they show great potential.

Human polyomavirus: Advantages and limitations as a human-specific viral marker in aquatic environments.

Human polyomaviruses (HPyVs) cause persistent infections in organs such as kidney, brain, skin, liver, respiratory tract, etc., and some types of HPyV are constantly excreted in the urine and/or feces of infected and healthy individuals. The use of an enteric virus as an indicator for human sewage/waste contamination in aquatic environments has been proposed; HPyVs are a good candidate since they are routinely found in environmental water samples from different geographical areas with relatively high abundance. HPyVs are highly human specific, having been detected in human waste from all age ranges and undetected in animal waste samples. In addition, HPyVs show a certain degree of resistance to high temperature, chlorine, UV, and low pH, with molecular signals (i.e., DNA) persisting in water for several months. Recently, various concentration methods (electronegative/positive filtration, ultrafiltration, skim-milk flocculation) and detection methods (immunofluorescence assay, cell culture, polymerase chain reaction (PCR), integrated cell culture PCR (ICC-PCR), and quantitative PCR) have been developed and demonstrated for HPyV, which has enabled the identification and quantification of HPyV in various environmental samples, such as sewage, surface water, seawater, drinking water, and shellfish. In this paper, we summarize these recent advancements in detection methods and the accumulation of environmental surveillance and laboratory-scale experiment data, and discuss the potential advantages as well as limitations of HPyV as a human-specific viral marker in aquatic environments.

Evaluation of virus removal efficiency of coagulation-sedimentation and rapid sand filtration processes in a drinking water treatment plant in Bangkok, Thailand.

In order to properly assess and manage the risk of infection by enteric viruses in tap water, virus removal efficiency should be evaluated quantitatively for individual processes in actual drinking water treatment plants (DWTPs); however, there have been only a few studies due to technical difficulties in quantifying low virus concentration in water samples. In this study, the removal efficiency of indigenous viruses was evaluated for coagulation-sedimentation (CS) and rapid sand filtration (RSF) processes in a DWTP in Bangkok, Thailand by measuring the concentration of viruses before and after treatment processes using real-time polymerase chain reaction (qPCR). Water samples were collected and concentrated from raw source water, after CS, and after RSF, and inhibitory substances in water samples were reduced by use of a hydrophobic resin (DAX-8). Pepper mild mottle virus (PMMoV) and JC polyomavirus (JC PyV) were found to be highly prevalent in raw waters, with concentrations of 10(2.88 ± 0.35) and 10(3.06 ± 0.42) copies/L (geometric mean ± S.D.), respectively. Step-wise removal efficiencies were calculated for individual processes, with some variation observed between wet and dry seasons. During the wet season, PMMoV was removed less by CS and more by RSF on average (0.40 log10 vs 1.26 log10, respectively), while the reverse was true for JC PyV (1.91 log10 vs 0.49 log10, respectively). Both viruses were removed similarly during the dry season, with CS removing the most virus (PMMoV, 1.61 log10 and 0.78 log10; JC PyV, 1.70 log10, and 0.59 log10; CS and RSF, respectively). These differences between seasons were potentially due to variations in raw water quality and the characteristics of the viruses themselves. These results suggest that PMMoV and JC PyV, which are more prevalent in environmental waters than the other enteric viruses evaluated in this study, could be useful in determining viral fate for the risk management of viruses in water treatment processes in actual full-scale DWTPs.

Mechanisms of antiviral action of plant antimicrobials against murine norovirus.

Numerous plant compounds have antibacterial or antiviral properties; however, limited research has been conducted with nonenveloped viruses. The efficacies of allspice oil, lemongrass oil, and citral were evaluated against the nonenveloped murine norovirus (MNV), a human norovirus surrogate. The antiviral mechanisms of action were also examined using an RNase I protection assay, a host cell binding assay, and transmission electron microscopy. All three antimicrobials produced significant reductions (P ≤ 0.05) in viral infectivity within 6 h of exposure (0.90 log10 to 1.88 log10). After 24 h, the reductions were 2.74, 3.00, and 3.41 log10 for lemongrass oil, citral, and allspice oil, respectively. The antiviral effect of allspice oil was both time and concentration dependent; the effects of lemongrass oil and citral were time dependent. Based on the RNase I assay, allspice oil appeared to act directly upon the viral capsid and RNA. The capsids enlarged from ≤ 35 nm to up to 75 nm following treatment. MNV adsorption to host cells was not significantly affected. Alternatively, the capsid remained intact following exposure to lemongrass oil and citral, which appeared to coat the capsid, causing nonspecific and nonproductive binding to host cells that did not lead to successful infection. Such contrasting effects between allspice oil and both lemongrass oil and citral suggest that though different plant compounds may yield similar reductions in virus infectivity, the mechanisms of inactivation may be highly varied and specific to the antimicrobial. This study demonstrates the antiviral properties of allspice oil, lemongrass oil, and citral against MNV and thus indicates their potential as natural food and surface sanitizers to control noroviruses.