Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a worldwide pandemic. Many projections concerning the outbreak, such as the estimated number of cases and deaths in upcoming ...months, have been made available. However, what happens to the virus after the pandemic subsides has not been fully explored. In this article, we discuss the ways that past and present human viruses have emerged via zoonotic transmission, the mechanisms that they have acquired the ability for effective transmission among humans, the process to sustain a chain of transmission to coexist with humans, and the factors important for complete containment leading to eradication of viruses. These aspects of viral disease may provide clues for the future path that SARS-CoV-2 might take in relation to human infection.
The Epstein-Barr virus (EBV) is etiologically linked to approximately 10% of gastric cancers, in which viral genomes are maintained as multicopy episomes. EBV-positive gastric cancer cells are ...incompetent for progeny virus production, making viral DNA cloning extremely difficult. Here we describe a highly efficient strategy for obtaining bacterial artificial chromosome (BAC) clones of EBV episomes by utilizing a CRISPR/Cas9-mediated strand break of the viral genome and subsequent homology-directed repair. EBV strains maintained in two gastric cancer cell lines (SNU719 and YCCEL1) were cloned, and their complete viral genome sequences were determined. Infectious viruses of gastric cancer cell-derived EBVs were reconstituted, and the viruses established stable latent infections in immortalized keratinocytes. While Ras oncoprotein overexpression caused massive vacuolar degeneration and cell death in control keratinocytes, EBV-infected keratinocytes survived in the presence of Ras expression. These results implicate EBV infection in predisposing epithelial cells to malignant transformation by inducing resistance to oncogene-induced cell death.
Recent progress in DNA-sequencing technology has accelerated EBV whole-genome sequencing, and the repertoire of sequenced EBV genomes is increasing progressively. Accordingly, the presence of EBV variant strains that may be relevant to EBV-associated diseases has begun to attract interest. Clearly, the determination of additional disease-associated viral genome sequences will facilitate the identification of any disease-specific EBV variants. We found that CRISPR/Cas9-mediated cleavage of EBV episomal DNA enabled the cloning of disease-associated viral strains with unprecedented efficiency. As a proof of concept, two gastric cancer cell-derived EBV strains were cloned, and the infection of epithelial cells with reconstituted viruses provided important clues about the mechanism of EBV-mediated epithelial carcinogenesis. This experimental system should contribute to establishing the relationship between viral genome variation and EBV-associated diseases.
Green tea extracts effectively inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in vitro in a dose-dependent manner. Ten-fold serially diluted solutions of catechin mixture ...reagent from green tea were mixed with the viral culture fluid at a volume ratio of 9:1, respectively, and incubated at room temperature for 5 min. The solution of 10 mg/mL catechin reagent reduced the viral titer by 4.2 log and 1.0 mg/mL solution by one log. Pre-infection treatment of cells with the reagent alone did not affect viral growth. In addition, cells treated with only the reagent were assayed for host cell viability using the WST-8 system, and almost no host cell damage by the treatment was observed. These findings suggested that the direct treatment of virus with the reagent before inoculation decreased the viral activity and that catechins might have the potential to suppress SARSCoV-2 infection.
We analyzed 3,184 cases of coronavirus disease in Japan and identified 61 case-clusters in healthcare and other care facilities, restaurants and bars, workplaces, and music events. We also identified ...22 probable primary case-patients for the clusters; most were 20-39 years of age and presymptomatic or asymptomatic at virus transmission.
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