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Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has emerged as a serious threat to human health worldwide. Efficient disinfection of surfaces contaminated with SARS-CoV-2 may help prevent its spread. This study aimed to investigate the in vitro efficacy of 222-nm far-ultraviolet light (UVC) on the disinfection of SARS-CoV-2 surface contamination. Methods: We investigated the titer of SARS-CoV-2 after UV irradiation (0.1 mW/cm 2) at 222 nm for 10-300 seconds using the 50% tissue culture infectious dose (TCID 50). In addition, we used quantitative reverse transcription polymerase chain reaction to quantify SARS-CoV-2 RNA under the same conditions. Results: One and 3 mJ/cm 2 of 222-nm UVC irradiation (0.1 mW/cm 2 for 10 and 30 seconds) resulted in 88.5 and 99.7% reduction of viable SARS-CoV-2 based on the TCID 50 assay, respectively. In contrast, the copy number of SARS-CoV-2 RNA did not change after UVC irradiation even after a 5-minute irradiation. Conclusions: This study shows the efficacy of 222-nm UVC irradiation against SARS-CoV-2 contamination in an in vitro experiment. Further evaluation of the safety and efficacy of 222-nm UVC irradiation in reducing the contamination of real-world surfaces and the potential transmission of SARS-CoV-2 is needed.

High level expression of the M2 ion channel protein of influenza virus inhibits the rate of intracellular transport of the influenza virus hemagglutinin (HA) and that of other integral membrane glycoproteins. HA coexpressed with M2 is properly folded, is not associated with GRP78- BiP, and trimerizes with the same kinetics as when HA is expressed alone. Analysis of the rate of transport of HA from the ER to the cis and medial golgi compartments and the TGN indicated that transport through the Golgi apparatus is delayed. Uncleaved HA0 was not expressed at the cell surface, and accumulation HA at the plasma membrane was reduced to 75-80% of control cells. The delay in intracellular transport of HA on coexpression of M2 was not observed in the presence of the M2-specific ion channel blocker, amantadine, indicating that the Golgi transport delay is due to the M2 protein ion channel activity equilibrating pH between the Golgi lumen and the cytoplasm, and not due to saturation of the intracellular transport machinery. The Na+/H+ ionophore, monensin, which also equilibrates pH between the Golgi lumen and the cytoplasm, caused a similar inhibition of intracellular transport as M2 protein expression did for HA and other integral membrane glycoproteins. EM data showed a dilation of Golgi cisternae in cells expressing the M2 ion channel protein. Taken together, the data suggest a similarity of effects of M2 ion channel activity and monensin on intracellular transport through the Golgi apparatus.

The paramyxoviruses define a diverse group of enveloped RNA viruses that includes a number of important human and animal pathogens. Examples include human respiratory syncytial virus and the human parainfluenza viruses, which cause respiratory illnesses in young children and the elderly; measles and mumps viruses, which have caused recent resurgences of disease in developed countries; the zoonotic Hendra and Nipah viruses, which have caused several outbreaks of fatal disease in Australia and Asia; and Newcastle disease virus, which infects chickens and other avian species. Like other enveloped viruses, paramyxoviruses form particles that assemble and bud from cellular membranes, allowing the transmission of infections to new cells and hosts. Here, we review recent advances that have improved our understanding of events involved in paramyxovirus particle formation. Contributions of viral matrix proteins, glycoproteins, nucleocapsid proteins, and accessory proteins to particle formation are discussed, as well as the importance of host factor recruitment for efficient virus budding. Trafficking of viral structural components within infected cells is described, together with mechanisms that allow for the selection of specific sites on cellular membranes for the coalescence of viral proteins in preparation of bud formation and virion release.

The inf luenza A virus M 2 integral membrane protein is an ion channel that permits protons to enter virus particles during uncoating of virions in endosomes and also modulates the pH of the trans-Golgi network in virus-infected cells. The M 2 protein is a homo-oligomer of 97 residues, and analysis by chemical cross-linking and SDS͞PAGE indicates M 2 forms a tetramer. However, a higher order molecular form is sometimes observed and, thus, it is necessary to determine the active form of the molecule. This was done by studying the currents of oocytes that expressed mixtures of the wild-type M 2 protein (epitope tagged) and the mutant protein M 2 -V 27 S, which is resistant to the inhibitor amantadine. The composition of mixed oligomers of the two proteins expressed at the plasma membrane of individual oocytes was quantified after antibody capture of the cell surface expressed molecules and it was found that the subunits mixed freely. When the ratio of wild-type to mutant protein subunits was 0.85:0.15, the amantadine sensitivity was reduced to 50% and for a ratio of 0.71:0.29 to 20%. These results are consistent with the amantadine-resistant mutant being dominant and the oligomeric state being a tetramer.The influenza A virus M 2 integral membrane protein is thought to function as an ion channel that permits protons to enter virus particles during uncoating of virions in endosomes and also to modulate the pH of the trans-Golgi network (for reviews see refs. 1 and 2). Direct electrophysiological evidence that the M 2 protein has ion channel activity has been obtained by expressing the M 2 protein in oocytes of Xenopus laevis (3-6) or in mammalian cells (7,8). The M 2 protein ion channel activity is specifically blocked by the anti-influenza virus drug amantadine and is activated at the lowered pH found intralumenally in endosomes and the trans-Golgi network (3,4,6,8). In addition, reconstitution of purified M 2 protein or introduction of the transmembrane domain peptide into planar lipid bilayers resulted in amantadine-sensitive ion channel activity that was activated by low pH (9-11).The M 2 protein is a homo-oligomer of 97 residues that is expressed at the plasma membrane of virus-infected cells and it is oriented in membranes such that it has 24 N-terminal extracellular (or lumenal) residues, a 19 residue transmembrane domain, and a 54 residue cytoplasmic tail (12). The native form of the M 2 protein is minimally a homotetramer consisting of a pair of either disulfide-linked dimers or disulfide-linked tetramers (13-15). In studies with chemical crosslinking reagents (13), and when large amounts of M 2 were purified on sucrose gradients (10), a small amount of a larger complex (150-180 kDa) has been identified that appears to contain only M 2 molecules and could represent a higher-order structure of M 2 oligomers.The biologically active oligomer of the vast majority of cellular ion channel proteins spans the membrane many times (e.g., Ca 2ϩ and Na ϩ channels have 24 transmembrane domains, K ϩ channels hav...