Biology subjects

Itakura, Y.

Publications and source records attributed to Itakura, Y..

14 recordsLinked to original sources

bioRxiv2026

West Nile virus capsid protein promotes viral replication and pathogenesis through PKCα-dependent lamin phosphorylation and nuclear deformation

The genus Orthoflavivirus comprises several medically important pathogens such as the West Nile virus (WNV), which causes encephalitis in humans. Although viral replication occurs in the cytoplasm, the capsid (C) protein of the orthoflavivirus is localized to both the cytoplasm and nucleus. Nuclear C protein contributes to viral replication and disease progression. However, the underlying mechanisms remain unclear. Here, we investigated whether the WNV C protein induces nuclear deformation and examined the underlying mechanism. We also assessed the contribution of this deformation to viral replication and pathogenesis. WNV infection and C protein expression induced morphological alterations in the nuclear lamina, leading to nuclear deformation. C protein expression enhanced lamin phosphorylation and the disassembly of the polymerized lamin network. In addition, C protein interacted with protein kinase C alpha (PKC) and localized PKC near the nuclear lamina. Downregulation of PKC expression inhibited C protein-induced lamin phosphorylation and nuclear deformation. In addition, both the downregulation of PKC expression and pharmacological inhibition of PKC reduced WNV replication. In contrast, the expression of phosphorylation-deficient lamin mutants attenuated the inhibitory effect of downregulated PKC expression on WNV replication. Furthermore, the pharmacological inhibition of PKC increased the survival rate of WNV-infected mice and suppressed both viral replication and nuclear deformation in the brain. Collectively, these results demonstrate that C protein remodels the nuclear lamina architecture through the PKC-lamin pathway, and that virus-induced nuclear deformation contributes to WNV replication and pathogenesis. Author summaryThe West Nile virus (WNV), a neurotropic orthoflavivirus, causes severe neurological diseases in humans. In host cells, orthoflaviviruses exclusively replicate in the cytoplasm. However, their capsid (C) proteins are localized to both the nucleus and cytoplasm. Although the nuclear C protein has been implicated in viral replication and disease progression, its underlying mechanisms remain unclear. Here, we demonstrate that the WNV C protein induces nuclear deformation, accompanied by the phosphorylation of lamin and disassembly of the nuclear lamina, a structural scaffold that maintains the nuclear shape. The C protein promotes the localization of PKC, a host kinase protein, near the nuclear lamina. Suppression of PKC expression or activity reduces lamin phosphorylation, nuclear deformation, and WNV replication. Importantly, pharmacological inhibition of PKC in WNV-infected mice reduced nuclear deformation and viral replication in the brain and improved survival rates. Collectively, our findings identify the host nucleus as an important site of WNV-host interaction and provide a new perspective that WNV, despite replicating in the cytoplasm, remodels host nuclear architecture to promote viral replication and pathogenesis.

microbiology↗

bioRxiv2026

A surrogate marker of protection confirms the efficacy of an AddaS03-adjuvanted West Nile virus subunit vaccine

West Nile virus (WNV) is the causative agent of fatal West Nile encephalitis. To date, no human vaccine against WNV has been approved. Adjuvants are important for developing effective and affordable vaccines that enhance the immunogenicity and decrease the required antigen doses. In this study, we assessed the efficacy of AddaS03, a synthetic adjuvant analogous to AS03, in a WNV subunit vaccine composed of soluble recombinant envelope protein (sEnv). Using a passive immunization mouse model, we defined the neutralizing antibody titer threshold required for protection against lethal WNV infections and applied this threshold as a surrogate marker to evaluate adjuvant efficacy. AddaS03-adjuvanted formulations elicited markedly higher neutralizing antibody titers compared to Alhydrogel adjuvant 2% (Alhydrogel), even at suboptimal antigen doses, and consistently exceeded the defined protective threshold titer. Moreover, in a sequential challenge mouse model, AddaS03-adjuvanted vaccines completely protected mice from symptomatic WNV infections, whereas Alhydrogel-adjuvanted vaccines failed to confer full protection. Collectively, these findings demonstrate that AddaS03 is a promising adjuvant for WNV subunit vaccine development and highlights the utility of a passive immunization model for defining protective antibody thresholds as a surrogate marker for vaccine evaluation.

microbiology↗

bioRxiv2026

Integrated in vivo and transcriptomic analyses of lethal Oropouche virus infection reveal suppression of pathogenic host responses by antiviral therapy

Oropouche virus (OROV) is an emerging arbovirus responsible for large outbreaks of febrile illness in Central and South America, with increasing reports of severe neurological disease and fatal outcomes. Despite its growing public health impact, no approved antiviral therapies or vaccines are currently available. Here, we show that favipiravir, a broad-spectrum nucleoside analogue, robustly suppresses OROV replication and disease in vivo. In a lethal Syrian hamster model, favipiravir treatment provided complete protection against OROV infection, preventing viral dissemination to peripheral organs and the central nervous system, and remained highly effective when administration was initiated after infection. In contrast, insufficient antiviral control resulted in viral neuroinvasion and fatality. To define host responses associated with OROV pathogenesis and their modulation by antiviral therapy, we performed transcriptomic profiling of liver and brain tissues. OROV infection induced interferon-driven inflammatory programs accompanied by marked disruption of metabolic and tissue homeostatic pathways, whereas these transcriptional signatures were largely abrogated by favipiravir treatment. Together, our findings identify favipiravir as a potent antiviral candidate against OROV and provide the first in vivo, tissue-resolved transcriptomic framework of OROV infection, linking effective viral suppression with the prevention of neuroinvasion and pathogenic host responses. These results highlight antiviral intervention as a viable strategy to mitigate OROV-associated disease and mortality.

microbiology↗

bioRxiv2026

A lethal mouse model of Oz virus infection reveals hepatic involvement and enables evaluation of antiviral and vaccine efficacy

Oz virus (OZV), a member of the genus Thogotovirus in the family Orthomyxoviridae, is an emerging tick-borne virus reported in Japan. A fatal human case and seroepidemiological evidence of widespread exposure among wild animals and humans suggest its potential public health significance. However, no animal models suitable for pathogenic studies or evaluation of countermeasures are available for OZV. Here, we have established a lethal mouse model of OZV infection using cell-adapted virus and mice lacking type I interferon signaling (B6 Ifnar1 KO mice). OZV infection resulted in 100% mortality and was characterized by robust viral replication in the liver and spleen, severe hepatitis, and acute liver injury. Using this model, we also demonstrated that oral administration of T-705, an antiviral drug widely used against RNA viruses, as well as immunization with an inactivated whole virus particle vaccine, protected B6 Ifnar1 KO mice from lethal OZV infection by mitigating the acute hepatitis. The present study provides critical insights into OZV pathogenesis and establishes a practical in vivo platform for the development of countermeasures against OZV infection. Significance statementEmerging tick-borne viruses pose a growing public health concern, yet progress in understanding their pathogenesis and in developing countermeasures is often limited by the lack of relevant animal models. Oz virus (OZV), a recently identified thogotovirus associated with a fatal human case, exemplifies this challenge. Here, we establish a lethal mouse model of OZV infection that reveals pronounced hepatic involvement as a central pathological feature. Using this model, we demonstrate effective protection by both an antiviral drug and an inactivated vaccine against lethal OZV challenge. This study provides a practical in vivo platform for investigating OZV pathogenesis and for accelerating the development of medical countermeasures against this emerging tick-borne virus.

microbiology↗

bioRxiv2025

Application of the CPER reverse genetics system for genetic engineering of rabies virus

Reverse genetics (RG) systems are essential tools for basic virological studies and applied studies using engineered recombinant viruses in various research fields. While the circular polymerase extension reaction (CPER) has been widely applied to prepare a full-length infectious complementary DNA (cDNA) of positive-sense RNA viruses, its use for negative-sense RNA viruses (mononegaviruses) remains limited. Here, we report the first CPER-based RG system for rabies virus (RABV), a member of mononegaviruses. Infectious RABV was successfully rescued from cells transfected with helper plasmids and the CPER product, the assembled overlapping DNA fragments encoding the full-length viral genome cDNA and regulatory elements. Using this system, we generated wild-type, point-mutant, reporter-expressing, and chimeric RABVs, all of which retained their expected biological properties. Deep sequencing revealed that CPER-derived viruses occasionally harbor low-frequency mutations undetectable by Sanger sequencing, highlighting PCR-related artifacts as a limitation. In addition, CPER products with a pUC19 backbone could be directly applied for E. coli transformation and cloning of RABV full genome cDNA plasmids, offering a flexible, ligase-free cloning strategy for conventional RG. Our work establishes CPER as a versatile platform for engineering recombinant RABVs, facilitating rapid generation and genetic manipulation of RABV with potential applications for research on other mononegaviruses.

microbiology↗

bioRxiv2024

Endoplasmic reticulum patterns insect cuticle nanostructure

Insect cuticles with nano-level structures exhibit functional surface properties such as structural color and superhydrophobicity. Despite the enormous influence the cuticle has had on biomimetic industrial applications, molecular and cellular mechanisms of cuticular extracellular matrix (ECM) assembly into nanoscale structures remain poorly understood in insects and other taxa. Ghiradella (1989) described how a crystallin-like lattice of endoplasmic reticulum (ER) prefigures the patterning of the porous cuticle of the butterfly wing scale with structural color1. Building on that insight, we show that the nanopore structure of the olfactory (olf) organs, which serve as molecular filters in Drosophila, is built through a novel process in which ER material is trafficked to the plasma membrane mediated by the autophagy pathway. The process is controlled by the insect-specific protein Gore-tex/Osiris23 (Gox)2, which is localized to the tubular ER of olf hair cells. Gox recruits Ref(2)P, the fly counterpart of mammalian p62/SQSTM13, to initiate ER scission. The excised ER fragments are processed by autophagy to gain access to the plasma membrane and trigger membrane invagination, which plays a role in remodeling the cuticular envelope layer to the nanopore formation. This repurposing of the ER phagy for machinery to support the fabrication of nanoscale ECM by the Gox protein sheds light on the nanopatterning of insect cuticles and their genetic control.

developmental biology↗

bioRxiv2024

Mechanical control of the insect extracellular matrix nanostructure

Nanoscale modifications of apical extracellular matrix (ECM) have created a variety of functional surfaces with distinct physical properties, as exemplified by structural coloration and superhydrophobicity in animals and plants1. While the surface nanostructures of various organisms have inspired numerous biomimetic applications, the biological mechanisms underlying ECM patterning at the nanoscale remain largely unknown. Here, we investigated the morphogenesis of cuticular pores in Drosophila olfactory organs2,3. Hundreds of uniform-sized nanopores of [~]50 nm permit selective access of odorant molecules to olfactory neurons. We showed that matrices composed of the zona pellucida domain (ZPD) protein4-6 cover sensory organs in cell type-specific patterns and combinations. The ZPD proteins Dyl, Tyn, Mey, and Nyo form matrices with specific mixing and sorting properties, restricting cell growth and movement. The disruption of ZPD matrices leads to detachment of the envelope layer of the cuticle from the plasma membrane, and reduced numbers and irregularly sized nanopores. Our results suggest that compressive force from the ECM is essential for robust nanopore morphogenesis. This work reveals a previously unrecognized role for ZPD proteins as modular units that establish the mechanical environment required to modulate the nanoscale assembly of cuticle materials, opening a new biological context to these biomimetically important structures.

developmental biology↗

bioRxiv2023

Combination therapy with oral antiviral and anti-inflammatory drugs improves the efficacy of delayed treatment in severe COVID-19

Pulmonary infection with SARS-CoV-2 stimulates host immune responses and can also result in the progression of dysregulated and critical inflammation. Throughout the pandemic, the management and treatment of COVID-19 has been continuously updated with a range of antiviral drugs and immunomodulators. Monotherapy with oral antivirals has proven to be effective in the treatment of COVID-19. However, the treatment should be initiated in the early stages of infection to ensure beneficial therapeutic outcomes, and there is still room for further consideration on therapeutic strategies using antivirals. Here, we show that the oral antiviral ensitrelvir combined with the anti-inflammatory corticosteroid methylprednisolone has higher therapeutic effects and better outcomes in a delayed dosing model of SARS-CoV-2 infected hamsters compared to the monotherapy with ensitrelvir or methylprednisolone alone. Combination therapy with these drugs improved respiratory conditions and the development of pneumonia in hamsters even when the treatment was started after 2 days post infection. The combination therapy led to a differential histological and transcriptomic pattern in comparison to either of the monotherapies, with reduced lung damage and down-regulated expressions of genes involved in inflammatory response. Furthermore, we found that the combination treatment is effective in infection with both highly pathogenic delta and circulating omicron variants. Our results demonstrate the advantage of combination therapy with antiviral and corticosteroid drugs in COVID-19 treatment. Since both drugs are available as oral medications, this combination therapy could provide a clinical and potent therapeutic option for COVID-19.

microbiology↗

bioRxiv2022

Virological characteristics of the SARS-CoV-2 XBB variant derived from recombination of two Omicron subvariants

In late 2022, the SARS-CoV-2 Omicron subvariants have highly diversified, and XBB is spreading rapidly around the world. Our phylogenetic analyses suggested that XBB emerged by recombination of two co-circulating BA.2 lineages, BJ.1 and BM.1.1.1 (a progeny of BA.2.75), during the summer of 2022 around India. In vitro experiments revealed that XBB is the most profoundly resistant variant to BA.2/5 breakthrough infection sera ever and is more fusogenic than BA.2.75. Notably, the recombination breakpoint is located in the receptor-binding domain of spike, and each region of recombined spike conferred immune evasion and augmented fusogenicity to the XBB spike. Finally, the intrinsic pathogenicity of XBB in hamsters is comparable to or even lower than that of BA.2.75. Our multiscale investigation provided evidence suggesting that XBB is the first documented SARS-CoV-2 variant increasing its fitness through recombination rather than single mutations.

microbiology↗

bioRxiv2022

Morphogenesis of bullet-shaped rabies virus particles requires a functional interplay between the viral matrix protein and ESCRT-I component TSG101

Viral protein assembly and virion budding are tightly regulated to enable the proper formation of progeny virions. At this late stage in the virus life cycle, some enveloped viruses take advantage of the host ESCRT (endosomal sorting complex required for transport) machinery, which contributes to the physiological functions of membrane modulation and abscission. Bullet-shaped viral particles are unique morphological characteristics of rhabdoviruses; however, the involvement of host factors in rhabdovirus infection, and specifically the molecular mechanisms underlying virion formation are not fully understood. In the present study, we used a siRNA screening approach and found that the ESCRT-I component TSG101 contributes to the propagation of rabies virus (RABV). We demonstrated that the matrix protein (M) of RABV interacts with TSG101 via the late-domain containing the PY and YL motifs, which are conserved in various viral proteins. Loss of the YL motif in the RABV M or the downregulation of host TSG101 expression resulted in the intracellular aggregation of viral proteins and abnormal virus particle formation, indicating a defect in the RABV assembly and budding processes. These results indicate that the interaction of the RABV M and TSG101 is pivotal for not only the efficient budding of progeny RABV from infected cells but also for the bullet-shaped virion morphology. ImportanceEnveloped-viruses bud from cells with the host lipid bilayer. Generally, the membrane modulation and abscission are mediated by host ESCRT (endosomal sorting complex required for transport) complexes. Some enveloped-viruses utilize their late (L)-domain to interact with ESCRTs, which promotes viral budding. Rhabdoviruses form characteristic bullet-shaped enveloped-virions, but the underlying molecular mechanisms involved remain elusive. Herein, we showed that TSG101, one of ESCRT components, supports rabies virus (RABV) budding and proliferation. TSG101 interacted with RABV matrix protein via L-domain, and the absence of this interaction resulted in intracellular virion accumulation and distortion of the morphology of progeny virions. Our study reveals that virion formation of RABV is highly regulated by TSG101 and the virus matrix protein.

microbiology↗

bioRxiv2022

Convergent evolution of the SARS-CoV-2 Omicron subvariants leading to the emergence of BQ.1.1 variant

In late 2022, although the SARS-CoV-2 Omicron subvariants have highly diversified, some lineages have convergently acquired amino acid substitutions at five critical residues in the spike protein. Here, we illuminated the evolutionary rules underlying the convergent evolution of Omicron subvariants and the properties of one of the latest lineages of concern, BQ.1.1. Our phylogenetic and epidemic dynamics analyses suggest that Omicron subvariants independently increased their viral fitness by acquiring the convergent substitutions. Particularly, BQ.1.1, which harbors all five convergent substitutions, shows the highest fitness among the viruses investigated. Neutralization assays show that BQ.1.1 is more resistant to breakthrough BA.2/5 infection sera than BA.5. The BQ.1.1 spike exhibits enhanced binding affinity to human ACE2 receptor and greater fusogenicity than the BA.5 spike. However, the pathogenicity of BQ.1.1 in hamsters is comparable to or even lower than that of BA.5. Our multiscale investigations provide insights into the evolutionary trajectory of Omicron subvariants.

microbiology↗

bioRxiv2022

Oral administration of S-217622, a SARS-CoV-2 main protease inhibitor, decreases viral load and accelerates recovery from clinical aspects of COVID-19

In parallel with vaccination, oral antiviral agents are highly anticipated to act as countermeasures for the treatment of the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Oral antiviral medication demands not only high antiviral activity but also target specificity, favorable oral bioavailability, and high metabolic stability. Although a large number of compounds have been identified as potential inhibitors of SARS-CoV-2 infection in vitro, few have proven to be effective in vivo. Here, we show that oral administration of S-217622, a novel inhibitor of SARS-CoV-2 main protease (Mpro, also known as 3C-like protease), decreases viral load and ameliorates the disease severity in SARS-CoV-2-infected hamsters. S-217622 inhibited viral proliferation at low nanomolar to sub-micromolar concentrations in cells. Oral administration of S-217622 demonstrated eminent pharmacokinetic properties and accelerated recovery from acute SARS-CoV-2 infection in hamster recipients. Moreover, S-217622 exerted antiviral activity against SARS-CoV-2 variants of concern (VOCs), including the highly pathogenic Delta variant and the recently emerged Omicron variant. Overall, our study provides evidence that S-217622, an antiviral agent that is under evaluation in a phase II/III clinical trial, possesses remarkable antiviral potency and efficacy against SARS-CoV-2 and is a prospective oral therapeutic option for COVID-19.

microbiology↗

bioRxiv2021

SARS-CoV-2 bearing a mutation at the S1/S2 cleavage site exhibits attenuated virulence and confers protective immunity

Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) possesses a discriminative polybasic cleavage motif in its spike protein that is recognized by host furin protease. Proteolytic cleavage activates the spike protein and influences both the cellular entry pathway and cell tropism of SARS-CoV-2. Here, we investigated the impact of the furin cleavage site on viral growth and pathogensis using a hamster animal model infected with SARS-CoV-2 variants bearing mutations at the furin cleavage site (S gene mutants). In the airway tissues of hamsters, the S gene mutants exhibited a low growth property. In contrast to parental pathogenic SARS-CoV-2, hamsters infected with the S gene mutants showed no body weight loss and only a mild inflammatory response, indicating the attenuated variant nature of S gene mutants. We reproduced the attenuated growth of S gene mutants in primary differenciated human airway epithelial cells. This transient infection was enough to induce protective neutralizing antibodies crossreacting with different SARS-CoV-2 lineages. Consequently, hamsters inoculated with S gene mutants showed resistance to subsequent infection with both the parental strain and the currently emerging SARS-CoV-2 variants belonging to lineages B.1.1.7 and P.1. Together, our findings revealed that the loss of the furin cleavage site causes attenuation in the airway tissues of SARS-CoV-2 and highlights the potential benefits of S gene mutants as potential immunogens.

microbiology↗

bioRxiv2018

Trynity controls epidermal barrier function and respiratory tube maturation in Drosophila by modulating apical extracellular matrix nano-patterning

The outer surface of insects is covered by the cuticle, which is derived from the apical extracellular matrix (aECM). The aECM is secreted by epidermal cells during embryogenesis. The aECM exhibits large variations in structure, function, and constituent molecules, reflecting the enormous diversity in insect appearances. To investigate the molecular principles of aECM organization and function, here we studied the role of a conserved aECM protein, the ZP domain protein Trynity, in Drosophila melanogaster. We first identified trynity as an essential gene for epidermal barrier function. trynity mutation caused disintegration of the outermost envelope layer of the cuticle, resulting in small- molecule leakage and in growth and molting defects. In addition, the tracheal tubules of trynity mutants showed defects in pore-like structures of the cuticle, and the mutant tracheal cells failed to absorb luminal proteins and liquid. Our findings indicated that trynity plays essential roles in organizing nano-level structures in the envelope layer of the cuticle that both restrict molecular trafficking through the epidermis and promote the massive absorption pulse in the trachea.\n\nSummary StatementThe zona pellucida domain protein Trynity controls the structural organization and function of the apical extracellular matrix in the epidermis and trachea of Drosophila.

developmental biology↗