Kyuwa, S. | bioRxiv Science

bioRxiv2021

Basic reproduction numbers of three strains of mouse hepatitis viruses in mice

Mouse hepatitis virus (MHV) is a murine coronavirus and one of the most important pathogens in laboratory mice. Although various strains of MHV have been isolated, they are generally excreted in the feces and transmitted oronasally via aerosols and contaminated bedding. In this study, we attempted to determine the basic reproduction numbers of three strains of MHV to improve our understanding of MHV infections in mice. Five-week-old female C57BL/6J mice were inoculated intranasally with either the Y, NuU, or JHM variant strain of MHV and housed with two naive mice. After 4 weeks, the presence or absence of anti-MHV antibody in the mice was determined by the enzyme-linked immunosorbent assay. We also examined the distribution of MHV in the organs of Y, NuU, or JHM variant-infected mice. Our data suggest that the transmissibility of MHV is correlated with viral growth in the gastrointestinal tract of infected mice. To the best of our knowledge, this is the first report to address the basic reproduction numbers among pathogens in laboratory animals.

microbiology↗

bioRxiv2020

Plasma irradiation efficiently inactivates the coronaviruses mouse hepatitis virus and SARS-CoV-2

Many inactivation methods have been shown to inactivate SARS-CoV-2 for safe and efficient diagnostic methods. COVID-19 is caused by airborne infection of SARS-CoV-2, and therefore, methods of inactivating the virus efficiently and safely are crucial for reducing the risk of airborne infection. In this regard, the effect of plasma discharge on the infectivity of the coronaviruses mouse hepatitis virus (MHV) and SARS-CoV-2 was tested. Plasma discharge efficiently reduced the infectivity of both coronaviruses. Treatment of SARS-CoV-2 in culture medium with a plasma discharge resulted in 95.17% viral inactivation after plasma irradiation after 1 hour (hr), 99.54% inactivation after 2 hrs and 99.93% inactivation after 3 hrs. Similar results were obtained for MHV. The results indicated that plasma discharge effectively and safely inactivated the airborne coronaviruses and may be useful in minimizing the risk of airborne infection of SARS-CoV-2.

microbiology↗

bioRxiv2019

Characterization of the untranslated region of lymphocytic choriomeningitis virus S segment

Lymphocytic choriomeningitis virus (LCMV) is a prototypic arenavirus. The viral genome consists of two RNA segments, L and S. The 5- and 3-termini of both L and S segments are highly conserved among arenaviruses. These regions consist of 19 complementary base pairs and are essential for viral genome replication and transcription. In addition to these 19 nucleotides in the 5- and 3-termini, there are untranslated regions (UTRs) composed of 58 and 41 nucleotide residues in the 5 and 3 UTRs, respectively, in the LCMV S segment. Their functional roles, however, have yet to be elucidated. In this study, a reverse genetics and a minigenome system for the LCMV strain WE were established and used to analyze the function of these regions. The results obtained from these analyses, plus RNA secondary structure prediction, revealed that not only these 19 nucleotides but also the 20th-40th and 20th-38th nucleotides located downstream of the 19 nucleotides in the 5- and 3-termini, respectively, are heavily involved in viral genome replication and transcription. Furthermore, the introduction of mutations in these regions depressed viral propagation in vitro and enhanced attenuation in vivo. Conversely, recombinant LCMVs (rLCMVs), which had various deletions in the other UTRs, propagated as well as wild-type LCMV in vitro but were attenuated in vivo. Most mice previously infected with rLCMVs with mutated UTRs, when further infected with a lethal dose of wild-type LCMV, survived. These results suggest that rLCMVs with mutated UTRs could be candidates for an LCMV vaccine.\n\nIMPORTANCEThe function of untranslated regions (UTRs) of the arenavirus genome has not well been studied except for the 19 nucleotides of the 5- and 3-termini. In this study the function of the UTRs of the LCMV S segment was analyzed. It was found that not only the 19 nucleotides of the 5- and 3-termini but also the 20th-40th and 20th-38th nucleotides located downstream of the 19 nucleotides in the 5- and 3-termini, respectively, were involved in viral genome replication and transcription. Furthermore, other UTRs in the S segment were involved in virulence in vivo. The introduction of mutations to these regions makes it possible to establish attenuated LCMV and potentially develop LCMV vaccine candidates.

microbiology↗