Fukuma, A. | Search bioRxiv

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↗

bioRxiv2018

Therapeutic effects of favipiravir against severe fever with thrombocytopenia syndrome virus infection in a lethal mouse model: dose-efficacy studies upon oral administration

BackgroundSevere fever with thrombocytopenia syndrome (SFTS), caused by SFTS virus (SFTSV), is a viral hemorrhagic fever with a high case fatality rate. Favipiravir was reported to be effective in the treatment of SFTSV infection in vivo in type I interferon receptor knockout (IFNAR-/-) mice at treatment dosages of both 60 mg/kg/day and 300 mg/kg/day for a duration of 5 days.\n\nMethodsIn this study, the efficacy of favipiravir at dosages of 120 mg/kg/day and 200 mg/kg/day against SFTSV infection in an IFNAR-/- mouse infection model was investigated. IFNAR-/- mice were subcutaneously infected with SFTSV at a 1.0 x 106 50% tissue culture infectious dose followed by twice daily administration of favipiravir, comprising a total dose of either 120 mg/kg/day or 200 mg/kg/day. The treatment was initiated either immediately post infection or at predesignated time points post infection.\n\nResultsAll mice treated with favipiravir at dosages of 120 mg/kg/day or 200 mg/kg/day survived when the treatment was initiated at no later than 4 days post infection. A decrease in body weight of mice was observed when the treatment was initiated at 3-4 days post infection. Furthermore, all control mice died. The body weight of mice did not decrease when treatment with favipiravir was initiated immediately post infection at dosages of 120 mg/kg/day and 200 mg/kg/day.\n\nConclusionsSimilar to the literature-reported peritoneal administration of favipiravir at 300 mg/kg/day, the oral administration of favipiravir at dosages of 120 mg/kg/day and 200 mg/kg/day to IFNAR-/- mice infected with SFTSV was effective.\n\nAuthor summarySevere fever with thrombocytopenia syndrome (SFTS), which is caused by SFTS virus (SFTSV), is a generalized infectious disease with a high case fatality rate. Currently, no effective therapeutics for SFTS is available; therefore, the development of effective antiviral drugs is needed. Favipiravir exhibits antiviral activity against various RNA viruses, including SFTSV. The present study demonstrated the efficacy of favipiravir in the treatment of SFTSV infection in a lethal mouse model, when the dose was set similar to that approved for anti-influenza drug in humans by the Ministry of Health, Labour and Welfare, Japan. The present study suggests that favipiravir is a promising drug for the treatment of SFTSV infection.

microbiology↗