Publications by authors named "Ken Maeda"

Unlabelled: Feline infectious peritonitis (FIP) is a fatal disease caused by feline coronavirus (FCoV). Although multiple gene mutations in FCoV likely account for FIP pathogenesis, molecular studies for FCoV have been limited due to the lack of a suitable reverse genetics system. In the present study, we established a rapid PCR-based system to generate recombinant FCoV using the circular polymerase extension reaction (CPER) method for both serotype 1 and 2 viruses.

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In November 2020, a volunteer group reported an outbreak of an infectious disease with a high fatality rate and flu-like symptoms among stray cats in Aoshima, a remote island in Ehime, Japan. Nine adult cats with severe symptoms were hospitalized. Feline calicivirus (FCV) was isolated from pharyngeal swabs of six hospitalized cats.

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catheter-related bloodstream infections (CRBSIs) are an increasing concern in Japanese hospitals. Although their clinical characteristics have been explored, the genetic relationships and virulence profiles of isolates from CRBSIs remain understudied. Here, using advanced genomic techniques, we investigated the genetic diversity, phylogenetic relationships, and virulence profiles of isolates from patients with bloodstream infections.

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Most members of the genus Orthonairovirus, represented by Crimean-Congo hemorrhagic fever virus and Nairobi sheep disease virus, are tick-borne, and some have become a public health concern in recent years. Here, we report the isolation and genetic and biological characterization of a new orthonairovirus, designated as "Iwanai Valley virus" (IWVV), from Ixodes ovatus ticks in Hokkaido, Japan. The amino acid sequence of the viral nucleoprotein (NP) was found to be 34-45% identical to those of known orthonairoviruses.

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Taxonomy of the genus Rhinogobius was investigated for the first time in Central Vietnam. Five species occurring in this region can be distinguished by shape of their head, number of pectoral-fin rays, vertebral counts, arrangements of scales and cutaneous sensory papillae, and coloration. Two species are described as new, Rhinogobius rong sp.

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  • Getah virus (GETV) is a mosquito-borne virus that affects horses and pigs, causing symptoms like fever and rash, and has been reported in outbreaks primarily in Asia and Oceania.
  • A new strain of GETV (22IH8) was isolated from mosquitoes in Nagasaki, Japan in 2022, and genetic analysis shows it is more closely related to strains from China than those found in Japan in the past.
  • The current vaccine for horses in Japan (MI-110) is effective against the new strain, suggesting that existing vaccination efforts can still combat this emerging threat.
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  • Invasive raccoons in Hokkaido, Japan, are potential carriers of the canine distemper virus, with a study analyzing 611 serum samples revealing higher infection rates in 2007, 2021, and 2022 compared to 2008-2012, indicating outbreak occurrences during those years.
  • Logistic regression showed that raccoon population density and environmental factors, like residential area ratios, were linked to seropositivity rates, particularly highlighting changes over the years from forest to residential areas.
  • Ongoing monitoring and improved raccoon control efforts are crucial to prevent disease spread to native wildlife like raccoon dogs and foxes, as well as to protect domestic dogs from health risks.
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Migratory birds carry ticks harboring various pathogens, including the zoonotic Yezo virus. In Hokkaido, Japan, we collected ticks from migratory birds during 2020-2021. Eight of 385 pools, comprising 2,534 ticks, tested positive for Yezo virus RNA, suggesting Yezo virus might be spread through the flyways of migratory birds.

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Orientia tsutsugamushi (OT) is an obligate intracellular bacterium transmitted by larval trombiculid mites, responsible for scrub typhus in humans. In Japan, approximately 500 human cases are reported annually, with six major serotypes identified as Kato, Karp, Gilliam, Irie/Kawasaki, Shimokoshi, and Hirano/Kuroki. However, the prevalence of OT in Yamaguchi prefecture remains largely unknown.

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  • The isolation of SARS-CoV-2 from patient samples is crucial for accurate COVID-19 diagnosis and studying virus variants.
  • VeroE6 cells modified to overexpress human ACE2 and TMPRSS2 are more effective than standard VeroE6/TMPRSS2 cells, showing a 1.6-fold increase in virus isolation efficiency, especially for samples with low viral loads.
  • Experiments with VSV pseudoviruses indicate that these modified cells enhance infectivity rates, emphasizing the need for selecting optimal cell cultures when studying SARS-CoV-2.
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  • A study investigated how susceptible domestic cats are to SARS-CoV-2, including different variants like gamma, delta, and omicron.
  • Researchers found that cats inoculated with wild-type, gamma, and delta variants could shed the virus for a week and showed no severe symptoms even after being infected with a small amount of the virus.
  • While cats developed a strong immune response to the earlier variants, the study revealed that the omicron variant was less effective at replicating in cats and elicited a weaker immune response.
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  • - Reports indicate that SARS-CoV-2, the virus causing COVID-19, can be transmitted from humans to various mammals, with some animals showing severe symptoms and even dying in rare cases.
  • - In a Japanese zoo from late 2022 to 2023, an outbreak of the SARS-CoV-2 omicron variant occurred, affecting 24 lions where 13 showed respiratory issues and three older lions died.
  • - Analysis revealed that the deceased lions were infected with the omicron variant, while all lions tested had antibodies against it, highlighting the need for ongoing measures to protect unvaccinated animals from the virus.
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The green tea catechin epigallocatechin gallate (EGCg) has antimicrobial effects on many bacteria. In this study, we investigated the inhibitory effects of EGCg on spores and vegetative cells. The spores were insensitive to EGCg, but the growth of vegetative cells derived from germinated spores was inhibited by EGCg.

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  • Emerging respiratory viruses like SARS-CoV-2 pose a global risk, prompting the need for new antiviral strategies, particularly through the use of gapmer antisense oligonucleotides (ASOs).
  • Researchers synthesized about 300 ASOs targeting different regions of the SARS-CoV-2 RNA and effectively identified ASO#41, which inhibited viral replication and reduced infection-related cell damage.
  • ASO#41 demonstrated strong antiviral activity against multiple variants of SARS-CoV-2 in lab models and showed promise in mice, indicating its potential as a targeted treatment approach for respiratory viruses.
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  • - Rabies virus (RABV) is a deadly virus that causes rabies, categorized into fixed laboratory strains and street strains found in the wild, each with different traits.
  • - The Toyohashi strain is a street strain from Japan that was derived from a rabid dog bite and has been used to create a reverse genetics system for research.
  • - Researchers developed a recombinant Toyohashi strain that allows tracking of viral proteins in living cells, making it a valuable resource for studying how rabies street strains replicate at the molecular level.
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Most teleost fishes exhibit a biphasic life history with a larval oceanic phase that is transformed into morphologically and physiologically different demersal, benthic, or pelagic juveniles. This process of transformation is characterized by a myriad of hormone-induced changes, during the often abrupt transition between larval and juvenile phases called metamorphosis. Thyroid hormones (TH) are known to be instrumental in triggering and coordinating this transformation but other hormonal systems such as corticoids, might be also involved as it is the case in amphibians.

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Rabies is a fatal neurological disorder caused by rabies virus (RABV) infection. Approximately 60,000 patients die from rabies annually, and there are no effective treatments for this disease. Nucleoside analogs are employed as antiviral drugs based on their broad antiviral spectrum, and certain nucleoside analogs have been reported to exhibit anti-RABV activity.

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The persistence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among wildlife populations poses a potential risk for the emergence of novel variants. Therefore, monitoring SARS-CoV-2 infections in animals is crucial. As urban rodents live in close proximity to human habitats, there is a concern that they may be a potential source of zoonoses.

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Francisella tularensis is an intracellular gram-negative bacterium known as the causative agent of tularemia, which can be transmitted to humans by direct contact with wild animals or by tick bites. Although F. tularensis is highly pathogenic, its recent prevalence in Japan is underreported due to the small number of reported cases.

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  • Cervus nippon (sika deer) are common in eastern Asia and have antibodies against zoonotic pathogens, serving as potential reservoirs for diseases.
  • This study focused on developing and analyzing cultured cells from sika deer testicular tissue, confirming their origin from Japanese sika deer and their characteristics as a mixed cell population.
  • The cultured cells showed susceptibility to various arthropod-borne viruses in Japan, supporting their utility in understanding sika deer as a source of zoonoses and aiding research at the cellular and molecular levels.
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  • - Herpes B virus (BV) is a zoonotic virus that mainly infects macaque monkeys without symptoms, but can be deadly to humans, requiring high containment facilities for research.
  • - The study created a safer model, VSV/BVpv, using a modified virus that mimics BV's glycoproteins, identifying four key proteins needed for virus production and entry, which occurs through direct fusion with cell membranes.
  • - A new testing method was developed using VSV/BVpv to sensitively detect BV-neutralizing antibodies in macaque plasma, allowing safer studies of BV entry mechanisms without needing the high-risk BSL-4 environment.
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  • Mudskippers are amphibious fish that provide insight into the evolution of terrestrial movement in teleosts, yet detailed anatomical data on their musculoskeletal structure is scarce.
  • This research used advanced imaging techniques to study the barred mudskipper, revealing significant adaptations in muscle complexity, volume, and specialized structures for movement on land.
  • Key skeletal modifications, such as a reinforced shoulder-pelvic joint and thickened fin rays, demonstrate how these fish have evolved to effectively navigate both terrestrial and aquatic environments, highlighting important evolutionary transitions.
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Rabies virus (RABV) causes fatal neurological disease. Pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP) using inactivated-virus vaccines are the most effective measures to prevent rabies. In Japan, HEP-Flury, the viral strain, used as a human rabies vaccine, has historically been propagated in primary fibroblast cells derived from chicken embryos.

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The east coast of the Indochinese Peninsula is a well-known transition zone from subtropical to tropical systems, yet only a small number of studies have been conducted on the biogeography and phylogeography of aquatic organisms in this region. The Hau Giang medaka, , was originally described from the Mekong Delta in southern Vietnam, and later reported also from southeastern Thailand, west of the Mekong Delta region. However, the species' full geographic range and population genetic structures remain unknown.

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Rabies is a fatal encephalitic infectious disease caused by the rabies virus (RABV). RABV is highly neurotropic and replicates in neuronal cell lines . The RABV fixed strain, HEP-Flury, was produced via passaging in primary chicken embryonic fibroblast cells.

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