Biology subjects

Okabayashi, T.

Publications and source records attributed to Okabayashi, T..

8 recordsLinked to original sources

bioRxiv2026

High-titer convalescent serum from cats recovered from severe fever with thrombocytopenia syndrome protects SFTSV-infected mice

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging, tick-borne zoonosis caused by severe fever with thrombocytopenia syndrome virus (SFTSV) and is associated with high case-fatality rates in humans and cats. No vaccines or antiviral drugs are currently available for the prevention or treatment of feline SFTS. Because cats with SFTS often develop blood viral RNA loads exceeding those in severe human cases, we hypothesized that some naturally recovered cats develop strong neutralizing antibody responses and may serve as a potential source of antibody-rich serum for passive immunotherapy. We compared 80% plaque-reduction neutralization test (PRNT80) titers in convalescent sera from six human SFTS survivors and 14 cats that had recovered from naturally acquired SFTS, then evaluated the therapeutic efficacy of convalescent cat serum in SFTSV-infected, interferon receptor-deficient AG129 mice. Some SFTS-recovered cats showed high PRNT80 titers. Passive administration of high-titer convalescent cat serum early after infection protected SFTSV-infected mice. A single dose given at 2 or 3 days post-infection completely protected mice, whereas treatment at 4 days post-infection resulted in 40% survival. Administration on two consecutive days was associated with lower late-phase viremia in surviving mice. Sera from three independent SFTS-recovered cats improved survival, with greater effects observed for sera with higher neutralizing antibody titers. These findings indicate that some cats recovering from SFTS can develop high neutralizing antibody titers and their sera can exert therapeutic effects in an SFTSV-infected mouse model. These findings support further evaluation of passive immunotherapy as a treatment strategy for feline SFTS.

microbiology↗

bioRxiv2022

Virucidal activity and mechanism of action of cetylpyridinium chloride against SARS-CoV-2

ObjectiveSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the pathogen causing the coronavirus disease 2019 (COVID-19) global pandemic. Recent studies have shown the importance of the throat and salivary glands as sites of virus replication and transmission. The viral host receptor, angiotensin-converting enzyme 2 (ACE2), is broadly enriched in epithelial cells of the salivary glands and oral mucosae. Oral care products containing cetylpyridinium chloride (CPC) as a bactericidal ingredient are known to exhibit antiviral activity against SARS-CoV-2 in vitro. However, the exact mechanism of action remains unknown. MethodsThis study examined the antiviral activity of CPC against SARS-CoV-2 and its inhibitory effect on the interaction between the viral spike (S) protein and ACE2 using an enzyme-linked immunosorbent assay. ResultsCPC (0.05%, 0.1% and 0.3%) effectively inactivated SARS-CoV-2 within the contact times (20 and 60 s) in directions for use of oral care products in vitro. The binding ability of both the S protein and ACE2 were reduced by CPC. ConclusionsOur results suggest that CPC inhibits the interaction between S protein and ACE2, and thus, reduces infectivity of SARS-CoV-2 and suppresses viral adsorption.

microbiology↗

bioRxiv2022

Identification of domestic cat hepadnavirus from a cat blood sample in Japan

The hepatitis B virus (Hepadnaviridae) induces chronic hepatitis and hepatic cancer in humans. A novel domestic cat hepadnavirus (DCH) was recently identified in several countries, however, the DCH infection status of cats in Japan is unknown. Therefore, we investigated the DCH infection rate of 139 cat samples collected in Japan. We identified one positive blood sample (0.78%) from a 17-year-old female cat with chronically elevated alanine aminotransferase. Phylogenetic analysis demonstrated that the DCH strain identified in this study is genetically distinct from strains in other countries. Further investigations are required to elucidate the evolution of DCH and the impact of DCH infection on hepatic diseases in domestic cats.

microbiology↗

bioRxiv2021

Ambiguous Body Ownership Experience Caused by Feeling-judgement Conflict: Evidence from Subjective Measurement in Rubber Hand Illusion using Integrated Information Theory

AO_SCPLOWBSTRACTC_SCPLOWHuman body awareness is malleable and adaptive to changing contexts. The illusory sense of body-ownership has been studied since the publication of the rubber hand illusion, where ambiguous body ownership feeling, expressed as "the dummy hand is my hand even though that is not true", was first defined. Phenomenologically, the ambiguous body ownership is attributed to a conflict between feeling and judgement; in other words, it characterises a discrepancy between first-person (i.e. bottom-up) and third-person (i.e. top-down) processes. Although Bayesian inference can explain this malleability of body image sufficiently, the theory does not provide a good illustration of why we have different experiences to the same stimuli - the difficulty lies in the uncertainty regarding the concept of judgement in their theory. This study attempts to explain subjective experience during rubber hand illusions using integrated information theory (IIT). The integrated information {Phi} in IIT measures the difference between the entire system and its subsystems. This concept agrees with the phenomenological interpretation - that is, there is conflict between judgement and feeling. By analysing the seven nodes of a small body- brain system, we demonstrate that the integrity of the entire system during the illusion decreases with increasing integrity of its subsystems. These general tendencies agree well with many brain-image analyses and subjective reports; furthermore, we found that subjective ratings were associated with the {Phi}s. Our result suggests that IIT can explain the general tendency of the sense of ownership illusions and individual differences in subjective experience during the illusions.

animal behavior and cognition↗

bioRxiv2021

Rapid inactivation of SARS-CoV-2 variants by continuous and intermittent irradiation with a deep-ultraviolet light-emitting diode (DUV-LED) device

More than 1 year has passed since social activities have been restricted due to the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). More recently, novel SARS-CoV-2 variants have been spreading around the world, and there is growing concern of higher transmissibility of the variants and weaker protective efficacy of vaccine against the variants. Immediate measures are needed to reduce human exposure to the virus. In this study, the antiviral efficacy of deep-ultraviolet light-emitting diode (DUV-LED) irradiation (280 {+/-} 5 nm, 3.75 mW/cm2) against three SARS-CoV-2 variants was evaluated. For the B.1.1.7, B.1.351, and P.1 strains, the infectious titer reduction rates of 96.3%, 94.6%, and 91.9%, respectively, were already recognized with the irradiation of virus stocks for 1 s, and the rates increased to 99.9%, 99.9%, and 99.8%, respectively, with irradiation for 5 s. We also tested the effect of pulsed DUV-LED irradiation (7.5 mW/cm2, duty rate: 50%, frequency: 1 KHz) under the same output conditions as continuous irradiation, and found that the antiviral efficacy of pulsed and continuous irradiation was the same. These findings suggest that SARS-CoV-2 may be instantly inactivated by DUV-LED irradiation if the DUV-LED device is further developed and optimized to increase its output.

microbiology↗

bioRxiv2020

Rapid inactivation of SARS-CoV-2 with ozone water

Although ozone water is one of the promising candidates for hand hygiene to prevent fomite infection, the detailed effects of ozone water on SARS-CoV-2 have not been clarified. We evaluated the inactivating effect of ozone water against SARS-CoV-2 by its concentration and exposure time. The reduction rates of virus titer after 5 sec treatment with ozone concentrations of 1, 4, 7, and 10 mg/L were 81.4%, 93.2%, 96.6%, and 96.6%, respectively. No further decrease in virus titer was observed by the extended exposure time over 5 sec. High-concentration ozone water was considered to be effective in promptly inactivating SARS-CoV-2 virus.

microbiology↗

bioRxiv2020

An affinity-matured human monoclonal antibody targeting fusion loop epitope of dengue virus with in vivo therapeutic potency

Dengue virus (DENV), from the genus flavivirus of the family flaviviridae, causes serious health problems globally. Human monoclonal antibodies (HuMAb) can be used to elucidate the mechanisms of neutralization and antibody-dependent enhancement (ADE) of DENV infections, leading to the development of a vaccine or therapeutic antibodies. Here, we generated eight HuMAb clones from an Indonesian patient infected with DENV. These HuMAbs exhibited the typical characteristics of weak neutralizing antibodies including high cross-reactivity with other flaviviruses and targeting of the fusion loop epitope (FLE). However, one of the HuMAbs, 3G9, exhibited strong neutralization ability (NT50 < 0.1 {micro}g/ml) and possessed a high somatic hyper-mutation rate of the variable region, indicating affinity-maturation. Administration of this antibody significantly improved the survival rate of interferon-/{beta}/{gamma} receptor knockout C57BL/6 mice after a lethal DENV challenge. Additionally, Fc-modified 3G9 molecules that had lost their in vitro ADE activity showed significantly enhanced therapeutic potency in vivo and competed strongly with an ADE-prone antibody in vitro. Taken together, the affinity-matured FLE-targeting antibody 3G9 exhibits several promising features for therapeutic application including a low NT50 value, potential for pan-flavivirus infection treatment, and suppression of ADE. This study demonstrates the therapeutic potency of affinity-matured FLE-targeting antibodies.

microbiology↗

bioRxiv2020

Rapid inactivation of SARS-CoV-2 with Deep-UV LED irradiation

The spread of novel coronavirus disease 2019 (COVID-19) infections worldwide has raised concerns about the prevention and control of SARS-CoV-2. Devices that rapidly inactivate viruses can reduce the chance of infection through aerosols and contact transmission. This in vitro study demonstrated that irradiation with a deep ultraviolet light-emitting diode (DUV-LED) of 280 {+/-}5 nm wavelength rapidly inactivates SARS-CoV-2 obtained from a COVID-19 patient. Development of devices equipped with DUV-LED is expected to prevent virus invasion through the air and after touching contaminated objects.

microbiology↗