Biology subjects

Nagata, K.

Publications and source records attributed to Nagata, K..

At least 19 recordsLinked to original sources

bioRxiv2026

VLCFA-mediated inter-cell layer communication controls cellular pluripotency in Arabidopsis callus

Plants have remarkable capacity to reconstruct entire organ systems from tissue explants. In Arabidopsis two-step tissue culture system, pluripotency regulators are specifically expressed in the middle-cell layer of the stratified callus tissue. However, regulatory mechanisms underlying the radial patterning of callus remained unclear. Here, we found that very-long-chain fatty acids (VLCFAs) synthesized in the epidermis-like outermost layer are essential for pluripotency acquisition and successful shoot regeneration. Our genetic and transcriptomic analyses revealed that the regulatory roles of VLCFAs on pluripotency acquisition involve inter-cell layer signaling in callus tissue, while they are at least partly independent of ATML1/PDF2 functions and cuticular wax synthesis in the outermost layer. VLCFAs spatially restrict procambium cell identity by non-cell-autonomously suppressing cytokinin signaling, thereby allowing for establishment of the middle-cell layer. We propose that the inhibitory relationships between layer-specific regulators underlie the intricate balance of cellular fate determination in pluripotent callus.

plant biology↗

bioRxiv2026

Role of the IRE1α-XBP1 axis in IgE-dependent activation of mast cells

The IRE1-XBP1 axis is the most conserved of three major unfolded protein response (UPR) branches that are triggered by the endoplasmic reticulum (ER) stress. Although the transcription factor XBP1 is involved in the development and function of several hematopoietic lineages, the role of XBP1 in the activation of mast cells (MCs) that play key role in allergic response remains largely unknown. Because we have identified salicylaldehyde (SA), which inhibits IRE1 nuclease activity that is essential for production of XBP1, as an inhibitor of MC activation in our previous screening, we investigated the effects of additional IRE1 inhibitors, 3-methyl-6-bromo-salichylaldehyde (MBSA) and KIRA6, targeting nuclease domain and kinase domain, respectively, on MC activation. MBSA and KIRA6 suppressed IgE-dependent degranulation and cytokine release of bone marrow-derived MCs (BMMCs), whereas these inhibitors did not suppress the Ca2+ ionophore- or compound48/80-induced degranulation. Treatment with inhibitors against two other branches of UPR, the PERK and the ATF6 pathways, did not affect IgE-induced activation of BMMCs. Intraperitoneal administration of MBSA or KIRA6 significantly suppressed IgE-induced passive anaphylaxis in mice. Furthermore, to evaluate the effect of XBP1, siRNA-mediated knockdown was performed. It was confirmed that Xbp1 siRNA introduction reduced IgE-dependent degranulation of BMMCs in parallel with the knockdown level of Xbp1 mRNA. Taken together, the IRE1-XBP1 axis plays a significant role in IgE-dependent and MC-mediated allergic response, which is considered to be therapeutic target of allergic diseases.

immunology↗

bioRxiv2025

Short-chain fatty acids modulate the development and the cell surface molecule expression of dendritic cells by epigenetic regulation

BackgroundShort-chain fatty acids (SCFAs) are produced by the gut microbiota as secondary metabolites during fermentation process of dietary fibers. Although SCFAs are beneficial for immuno-related diseases because they regulate the gene expression and functions of myeloid cells, the effects of SCFAs on the development of DCs remain unclear. MethodsWe analyzed the effect of SCFAs on the expression levels of surface proteins and mRNAs, and histone modification in Flt3L-induced bone marrow-derived DCs. ResultsSCFAs, particularly butyrate, regulated the expression of surface molecules on mouse bone marrow-derived dendritic cells (DCs): increases in MHCII, CD86, CD11b, and LPAM-1 (4{beta}7) levels and the ratio of CD11c+/PDCA-1-/B220- conventional DCs (cDCs) to CD11c+/PDCA-1+/B220+ plasmacytoid DCs (pDCs). Experiments using inhibitors of histone deacetylase (HDAC) and Gi proteins, and GPR109A deficient mice indicated that butyrate regulated DCs by suppression of HDACs and not through a stimulatory effect on G protein-coupled receptors. Butyrate and the HDAC inhibitor, trichostatin A (TSA), increased the cDC/pDC ratio, surface LPAM-1 and Itga4 mRNA, while the mRNA level of Itgb7 was not affected by butyrate and was reduced by TSA. ChIP assays showed that butyrate and TSA increased histone acetylation in the Itga4 and Spi1 genes. Furthermore, the butyrate treatment increased the levels of Spi1 mRNA and PU.1 protein and decreased those of Spib/SpiB in DCs. In knockdown (KD) experiments using siRNAs, the gene expression of Itga4 was decreased by KD of Spi1 or Irf8, and cDC/pDC ratio decreased by Spi1 KD. ConclusionsButyrate controls the gene expression and development of DCs through epigenetic regulation and DC-related transcription factors.

immunology↗

bioRxiv2025

The role of GATA2 in the expression of the soluble decoy receptor ST2/IL1RL1 in human and mouse mast cells

The ST2/IL1RL1 gene encodes a receptor subunit for IL-33. The ST2/IL1RL1 gene is transcribed and translated to two splice variants, full-length ST2 (ST2L) and soluble ST2 (sST2). ST2L is expressed on cell surface as membrane bound molecule and forms a heterodimer with IL-1RAcP, which plays an important role in Th2 transduces a signaling of IL-33. In contrast, sST2 blocks the IL-33-signaling via functioning as a decoy receptor of IL-33. In this study, we analyzed the regulatory mechanisms of the gene expression of sST2 in mast cell, the major source of sST2. We found that a hematopoietic cell-specific transcription factor GATA2 is essential for sST2 expression in human mast cells (a cell line and primary cells) and mouse mast cells. Various assays including ChIP assay, reporter assay, and 3C assay revealed that GATA2 binding to the distal promoter of the IL1RL1 gene transcriptionally activates proximal promoter-driven expression of sST2 through chromosomal conformation.

immunology↗

bioRxiv2025

PU.1 and TGF-β signaling transactivate CD103 expression in mast cells and dendritic cells: Opposite roles of GATA2 in the expression of mucosal mast cell-specific genes

Mucosal mast cells (MMCs) are distinguished from connective tissue MCs by the specific expression of integrin CD103 (E/{beta}7) and MC proteases Mcpt1 and Mcpt2. Although the expression of the Mcpt1 and Mcpt2 genes is cooperatively regulated by the transcription factor GATA2 and TGF-{beta} signaling in MMCs, the transcriptional mechanism of CD103 expression remains unknown. Here, we found that surface CD103 and Itgae mRNA levels were significantly increased by the knockdown (KD) of Gata2 in bone marrow-derived MCs (BMMCs), which was accelerated by a TGF-{beta} stimulation. Since the mRNA levels of Spi1 (encoding PU.1) were increased in Gata2 KD BMMCs, we examined the effects of PU.1 on CD103 expression. As expected, CD103 levels on BMMCs were significantly decreased by Spi1 KD and increased by Spi1 overexpression. Spi1 KD suppressed Itgae expression even in the presence of TGF-{beta} in BMMCs and peritoneal MCs, whereas Gata2 KD amplified the TGF-{beta}-induced increase in Itgae expression. The amount of PU.1 binding to the cis-element in the Itgae gene was significantly and moderately increased by Gata2 KD and the TGF-{beta} stimulation, respectively. Since PU.1 is an essential transcription factor for dendritic cells (DCs), we examined the role of PU.1 in CD103 expression on DCs. The KD experiment using BMDCs showed a significant decrease in CD103 levels in Spi1 siRNA-transfected BMDCs. We concluded that PU.1 affected CD103 expression on MMCs and DCs by transactivating the Itgae gene, and also that GATA2, which positively regulated the MMC-specific expression of Mcpt1 and 2, inhibited CD103 expression by repressing PU.1.

molecular biology↗

bioRxiv2025

Impact of Low-Dose Narrowband UV Radiation on Skin Tissue and Mast Cells in a Canine Model

Narrowband ultraviolet radiation (NB-UVR) therapy is widely utilized in dermatology worldwide. While the immunosuppressive effects of ultraviolet radiation are well-documented, its non-inflammatory effects remain poorly understood. This study evaluated the effects of sub-minimal erythema dose (MED) narrowband ultraviolet radiation using a canine model. The effects of narrowband-ultraviolet B (310 nm) and A2 wavelengths (320 and 330 nm) were compared. Initially, we demonstrated the therapeutic potential of NB-UVR in dogs with spontaneous atopic dermatitis (n = 6, p < 0.05). Following 300 mJ/cm{superscript 2} sub-MED ultraviolet radiation exposure, intradermal skin testing, skin mast cell counts, and RNA sequencing analysis were conducted. Additionally, cell viability (WST assay) and apoptosis (DAPI staining) were assessed in vitro using a canine mast cell line. Ultraviolet radiation exposure significantly reduced intradermal skin test scores across all wavelengths and decreased skin mast cell counts at 310 nm (n = 3, p < 0.05). In vitro, cell viability was significantly reduced at 310 and 320 nm (p < 0.05), and 310 nm irradiation specifically increased apoptotic cell numbers (p < 0.05). RNA sequencing identified 71 differentially expressed genes at 320 nm, with enrichment analysis highlighting muscle cell components and functions, potentially associated with arrector pili muscle activity. These findings suggest that 310 nm irradiation induces apoptosis, while 320 nm elicits non-inflammatory modulatory effects, highlighting distinct wavelength-specific therapeutic mechanisms of narrowband ultraviolet radiation.

immunology↗

bioRxiv2024

PATROL1-mediated H+-ATPase translocation boosts plant growth under drought by optimizing root and leaf functions

Optimizing leaf photosynthesis and root water and mineral uptake in crops during drought is crucial for enhancing agricultural productivity under climate change. Although plasma membrane H+-ATPase plays a key role in plant physiological processes, its overexpression alone does not consistently improve growth. While PROTON ATPASE TRANSLOCATION CONTROL 1 (PATROL1) regulates H+-ATPase translocation in response to various environmental stimuli in leaves, its function in roots remains largely unknown. Here we show that H+-ATPase was coimmunoprecipitated with PATROL1 in roots of Arabidopsis thaliana. Micrografting between wild type and PATROL1 knockout or overexpression lines showed that PATROL1 are indispensable in both shoots and roots, indicating that root uptake and leaf photosynthesis are simultaneous limiting factors for plant growth under drought conditions. PATROL1 overexpression in whole plants resulted in a 41% increase above wild type in shoot dry weight under drought conditions. These findings highlight the potential of H+-ATPase regulation in roots as a new strategy to improve plant productivity, particularly under drought conditions.

plant biology↗

bioRxiv2024

Roles of C/EBPα, GATA2, TGF-β-signaling, and epigenetic regulation in the expression of basophil-specific protease genes

In the present study, we analyzed the transcriptional regulation of genes encoding basophil-specific proteases Mcpt8 and Mcpt11 to clarify the molecular mechanisms by which the commitment between basophil and mast cell (MC) is determined. We used bone marrow-derived (BM) cells maintained in the presence of IL-3, in which basophil-like cells and MC-like cells exist. Knock down (KD) and overexpression of a transcription factor C/EBP showed that Cebpa mRNA levels were associated with those of Mcpt8 and Prss34 (a gene symbol of Mcpt11). Treatment with trichostatin A (TSA), a histone deacetylase inhibitor, decreased mRNA levels of Cebpa, Mcpt8, and Prss34 in BM cells, whereas these mRNA levels were increased by the treatment with an inhibitor of DNA methyltransferase. TSA treatment upregulated mRNA levels of Gata1 and Mitf in BM cells, and Mitf KD but not Gata1 KD increased mRNA levels of Cebpa and Prss34. Furthermore, Gata2 KD significantly decreased mRNA levels of Mcpt8 and Prss34 without affecting Cebpa mRNA level. In addition, mRNA levels of Gata1 and Mitf were increased in BM cells transfected with Cebpa siRNA, and decreased in Cebpa-overexpressing BM cells. We also found the TGF-{beta} treatment increased mRNA levels of Mcpt8, Prss34, along with upregulation of Gata2 and Cebpa transcription. Taken together, we conclude that the transcription of basophil-specific protease genes was positively regulated by C/EBP, GATA2, and TGF-{beta} signaling with modification of epigenetic regulation.

immunology↗

bioRxiv2024

Kaempferol exerts anti-inflammatory effects by accelerating Treg development via AhR-mediated and PU.1/IRF4-dependent transactivation of the Aldh1a2/RALDH2 gene in dendritic cells

Retinaldehyde dehydrogenase 2 encoded in the Aldh1a2 gene (RALDH2) is expressed in intestinal dendritic cells (DCs) in mesenteric lymph nodes (MLNs) and plays a crucial role in Treg development by producing retinoic acid. In the present study, we screened food ingredients and identified kaempferol, a flavonoid, as the compound that most effectively up-regulated RALDH2 expression in DCs. The development of Foxp3+ cells from OT-II-derived naive CD4+ T cells was enhanced by a co-culture with OVA peptide-pulsed bone marrow-derived DCs (BMDCs) in the presence of kaempferol or by a pre-treatment of BMDCs with kaempferol. The involvement of the aryl hydrocarbon receptor (Ahr) in the effects of kaempferol on Aldh1a2 expression was demonstrated by in vitro experiments using siRNA and various agonistic or antagonistic compounds of AhR. AhR suppressed Aldh1a2 gene expression and kaempferol inhibited the AhR activity by functioning as an antagonist of AhR. The kaempferol treatment also increased the protein levels of PU.1 and IRF4, which are essential for transcription of the Aldh1a2 gene in DCs, and accelerated the subsequent recruitment of PU.1 to the Aldh1a2 gene. The kaempferol-induced increase in PU.1 protein levels occurred in an AhR-dependent and transcription-independent manner, whereas the kaempferol treatment transactivated the Irf4 gene in DCs. The frequency of DCs exhibiting RALDH2 activity in the MLNs of mice was increased by the intraperitoneally (i.p.) administration of an AhR antagonist or by the oral administration of astragalin, a 3-O-glucoside of kaempferol. We also observed an increase in Tregs in the Peyers patches of C57BL/6 mice i.p. administered kaempferol-treated BMDCs. We utilized an OVA-induced food allergy model of Balb/c mice to examine the effects of kaempferol in vivo and confirmed that the rapid decrease in body temperature and allergic diarrhea observed just after the OVA challenge were significantly suppressed in mice administered kaempferol.

immunology↗

bioRxiv2024

NR4A3 deficiency ameliorates contact hypersensitivity and exacerbates psoriasis by regulating gene expression in dendritic cells

NR4A3 is a transcription factor that belongs to the nuclear receptor superfamily. To reveal the roles of NR4A3 in skin diseases, we constructed contact hypersensitivity (CHS)- and imiquimod-induced psoriasis models in Nr4a3-/- mice. In the CHS induced Nr4a3-/- mice, ear swelling was significantly reduced, accompanied by suppressed migration of dendritic cells (DCs), in which CCR7 expression was reduced. In contrast, ear swelling in psoriasis model Nr4a3-/- mice was enhanced. The expression levels of inflammatory cytokines in psoriasis skin lesions and in TLR7-ligand-stimulated DCs were increased by NR4A3 deficiency. Subcutaneous (s.c.) injection of hapten-treated Nr4a3+/+ DCs induced ear swelling in Nr4a3-/- mice, and s.c. injection of TLR7-ligand-stimulated Nr4a3-/- DCs caused significant ear swelling. Compared with Nr4a3+/+ DCs, Nr4a3-/- DCs expressed lower levels of CCR7 and IRF4, and higher levels of TLR7, IRF7, IFN-{beta}, and PU.1. Taken together, NR4A3 deficiency ameliorates CHS and exacerbates psoriasis by regulating the expression of CCR7, TLR7, and related transcription factors in DCs.

immunology↗

bioRxiv2024

Establishment of a novel amyotrophic lateral sclerosis patient-derived blood-brain barrier model: Investigating barrier dysfunction and immune cell interaction

Amyotrophic lateral sclerosis (ALS) is a major neurodegenerative disease for which there is currently no effective treatment. The main feature of the disease is the loss of motor neurons in the central nervous system (CNS), but other CNS components and the immune system also appear to be involved in the pathogenesis of the disease. The blood-brain barrier (BBB) is formed by specialized brain microvascular endothelial cells (BMECs) and plays a crucial role in maintaining homeostasis within the central nervous system (CNS). Autopsy studies have reported BBB abnormalities in ALS patients, and studies in animal models suggest that BBB breakdown may precede neurodegeneration. However, the difficulty of obtaining patient samples has hampered further studies. We used the method of differentiating BMEC-like cells from human induced pluripotent stem cells (hiPSCs), which have robust barrier functions and express adhesion molecules necessary for immune cell adhesion, to investigate BBB functions in ALS patients. We also established a method using automated analysis techniques to analyze immune cell adhesion to the BBB in multiple samples simultaneously and with minimal bias. BMEC-like cells derived from ALS patients carrying TARDBP N345K/WT mutations exhibited increased permeability to small molecules due to loss of tight junction, as well as increased expression of cell surface adhesion molecules, leading to enhanced immune cell adhesion. BMEC-like cells derived from hiPSCs with other types of TARDBP gene mutations (TARDBP K263E/K263E and TARDBP G295S/G295S) introduced by genome editing technology did not show such BBB dysfunction compared to the isogenic control. These results indicate that our model can recapitulate BBB abnormalities reported in ALS patients using patient (TARDBP N345K/WT) -derived hiPSCs and that two types of missense mutation, TARDBP K263E/K263E and TARDBP G295S/G295S, do not contribute to the BBB dysfunction. This novel ALS patient-derived BBB model is useful for the challenging analysis of the involvement of BBB dysfunction in the pathogenesis and to promote therapeutic drug discovery.

cell biology↗

bioRxiv2024

Impact of perinatal maternal docosahexaenoic acid-containing phospholipid synthesis on offspring growth and neurological symptoms

Mothers provide essential nutrients, including docosahexaenoic acid (DHA), an omega-3 fatty acid, during the perinatal period. DHA deficiency in perinatal mothers is linked to developmental abnormalities, especially in the central nervous system of the offspring; however, its specific impact on distinct events in fetal and neonatal brain development and prospective brain functions remains incompletely understood. We demonstrated using mice lacking Agpat3, a gene encoding the enzyme that synthesizes DHA-containing phospholipids (DHA-PLs), that maternal DHA-PL synthesis significantly contributes to the maternal- offspring DHA supply during the fetal period but not in infancy. Selective modulation of DHA-PL levels during fetal and postnatal periods in Agpat3-knockout mice showed that fetal stage-specific insufficiency in maternal DHA-PL supply potentially influences the neuropsychiatric phenotype in adult mice without affecting postnatal tissue DHA-PL levels, weight gain, and brain expansion. Collectively, enhancing maternal DHA-PL synthesis during pregnancy may help prevent prospective neuropsychiatric abnormalities in the offspring.

biochemistry↗

bioRxiv2023

The gut lactic acid bacteria metabolite, 10-oxo-cis-6,trans-11-octadecadienoic acid, suppresses inflammatory bowel disease in mice by modulating the NRF2 pathway and GPCR-signaling

Various gut bacteria, including Lactobacillus plantarum, possess several enzymes that produce hydroxy fatty acids (FAs), oxo FAs, conjugated FAs, and partially saturated FAs from polyunsaturated FAs as secondary metabolites. Among these derivatives, we identified 10-oxo-cis-6,trans-11-octadecadienoic acid ({gamma}KetoC), a {gamma}-linolenic acid (GLA)-derived enon FA, as the most effective immunomodulator, which inhibited the antigen-induced immunoactivation and LPS-induced production of inflammatory cytokines. The treatment with {gamma}KetoC significantly suppressed proliferation of CD4+ T cells, LPS-induced activation of bone marrow-derived dendritic cells (BMDCs), and LPS-induced IL-6 release from peritoneal cells, splenocytes, and CD11c+ cells isolated from the spleen. {gamma}KetoC also inhibited the release of inflammatory cytokines from BMDCs stimulated with poly-I:C, R-848, or CpG. Further in vitro experiments using an agonist of GPR40/120 suggested the involvement of these GPCRs in the effects of {gamma}KetoC on DCs. We also found that {gamma}KetoC stimulated the NRF2 pathway in DCs, and the suppressive effects of {gamma}KetoC and agonist of GPR40/120 on the release of IL-6 and IL-12 were reduced in Nrf2-/- BMDCs. We evaluated the role of NRF2 in the anti-inflammatory effects of {gamma}KetoC in a dextran sodium sulfate-induced colitis model. The oral administration of {gamma}KetoC significantly reduced body weight loss, improved stool scores, and attenuated atrophy of the colon, in wild-type C57BL/6 and Nrf2+/- mice with colitis. In contrast, the pathology of colitis was deteriorated in Nrf2-/- mice even with the administration of {gamma}KetoC. Collectively, the present results demonstrated the involvement of the NRF2 pathway and GPCRs in {gamma}KetoC-mediated anti-inflammatory responses.

immunology↗

bioRxiv2023

Butyrate, valerate, and niacin ameliorate anaphylaxis by suppressing IgE-dependent mast cell activation: Roles of GPR109A, PGE2, and epigenetic regulation

Short chain fatty acids (SCFAs) were recently shown to modulate the development and functions of immune-related cells. However, the molecular mechanisms by which SCFAs regulate mast cells (MCs) are not fully understood. We found that the oral administration of valerate or butyrate ameliorated passive systemic anaphylaxis in mice. Butyrate and valerate suppressed the IgE-mediated degranulation of bone marrow-derived MCs, which were eliminated by pertussis toxin and by the knockdown of Gpr109a. A treatment with trichostatin A suppressed IgE-mediated MC activation and reduced the surface expression level of Fc{varepsilon}RI on MCs. Acetylsalicylic acid and indomethacin attenuated the suppressive effects of SCFAs on degranulation. The degranulation degree was significantly decreased by the treatment with PGE2 whose release from MCs was markedly enhanced by SCFAs. The SCFA-mediated amelioration of anaphylaxis was exacerbated by COX inhibitors and an EP3 antagonist. The administration of niacin, a ligand of GPR109A, alleviated the symptoms of passive cutaneous anaphylaxis, which was inhibited by COX inhibitors and the EP3 antagonist. Key MessagesShort chain fatty acids (SCFAs), particularly butyrate and valerate, suppress the IgE-mediated activation of mast cells (MCs) in vivo and in vitro. SCFAs enhance the release of PGE2 from MCs, which inhibits the IgE-mediated activation of MCs. Niacin, a ligand of GPR109A, ameliorates IgE-dependent anaphylaxis. The administration of COX inhibitors or an antagonist of PGE2 receptor 3 (EP3) inhibited the suppressive effects of butyrate and niacin on IgE-dependent anaphylaxis.

immunology↗

bioRxiv2023

Kaempferol suppresses the activation of mast cells by modulating the expression of FcϵRI and SHIP1

In the present study, we evaluated the effects of kaempferol on bone marrow-derived mast cells (BMMCs). Kaempferol treatment significantly and dose-dependently inhibited IgE-induced degranulation, and cytokine production of BMMCs under the condition that cell viability was maintained. Kaempferol downregulated the surface expression levels of Fc{varepsilon}RI on BMMCs, but the mRNA levels of Fc{varepsilon}RI, {beta}, and {gamma}-chains were not changed by kaempferol treatment. Furthermore, the kaempferol-mediated downregulation of surface Fc{varepsilon}RI on BMMCs was still observed in the presence of a protein-synthesis inhibitor. These results suggest that kaempferol reduced the surface Fc{varepsilon}RI on BMMCs, independently of transcription and translation. We also found that kaempferol inhibited both LPS- and IL-33-induced IL-6 production from BMMCs, without affecting the expression levels of their receptors, TLR4 and ST2. Although kaempferol treatment increased the protein amount of NRF2, a master transcription factor of antioxidant stress, in BMMCs, inhibition of NRF2 did not alter the suppressive effect of kaempferol on degranulation. Finally, we observed that kaempferol treatment increased the levels of mRNA and protein of a phosphatase SHIP1 in BMMCs. These results indicate that kaempferol inhibited the IgE-induced activation of BMMCs by downregulating Fc{varepsilon}RI and upregulating SHIP1, and the SHIP1 increase is involved in the suppression of various signaling-mediated stimulations of BMMCs, such as those associated with TLR4 and ST2.

immunology↗

bioRxiv2023

Immunostimulatory effects of Bacillus coagulans SANK70258

Specific intestinal bacteria modulate immunoresponses through various pathways, and several probiotic bacteria have been identified as immunostimulants by screening. In the present study, we evaluated the immunomodulating effects of Bacillus coagulans SANK70258 (B. coagulans SANK70258), a spore-forming and lactic acid-producing bacterium usable as food supplement for human and animals. We found that treatment of mouse splenocytes with {gamma}-ray irradiated B. coagulans SANK70258 induced high amount of IFN-{gamma} in comparison with 7 kinds of typical lactic acid bacteria. Further analyses using splenocytes revealed that NK cell is a major source of IFN-{gamma}, and B. coagulans SANK70258-induced IFN-{gamma} production was inhibited by neutralization of IL-12 or IL-23, depletion of CD11c+ cells, and inhibition of NF{kappa}B. B. coagulans SANK70258 also induced release of IFN-{gamma} from activated CD8+ T cells, and increased expression of chemokine receptors in CD8+ T cells. B. coagulans SANK70258-treatment induced production of cytokines from bone marrow-derived dendritic cells, which is reduced by knockdown of Tlr2 and Nod2. B. coagulans SANK70258-treatment also induced IgA production from Peyers patch cells with high level among tested lactic bacteria. The oral intake of {gamma}-ray irradiated B. coagulans SANK70258 significantly increased intestinal IgA levels and IgA-expressing B cells in the Peyers patch of mice. Taken together, we conclude that B. coagulans SANK70258 possesses high activity as immunostimulant inducing production of IFN-{gamma} and IgA.

immunology↗

bioRxiv2022

Virological characteristics of the SARS-CoV-2 Omicron BA.2.75

SARS-CoV-2 Omicron BA.2.75 emerged in May 2022. BA.2.75 is a BA.2 descendant but is phylogenetically different from BA.5, the currently predominant BA.2 descendant. Here, we showed that the effective reproduction number of BA.2.75 is greater than that of BA.5. While the sensitivity of BA.2.75 to vaccination- and BA.1/2 breakthrough infection-induced humoral immunity was comparable to that of BA.2, the immunogenicity of BA.2.75 was different from that of BA.2 and BA.5. Three clinically-available antiviral drugs were effective against BA.2.75. BA.2.75 spike exhibited a profound higher affinity to human ACE2 than BA.2 and BA.5 spikes. The fusogenicity, growth efficiency in human alveolar epithelial cells, and intrinsic pathogenicity in hamsters of BA.2.75 were comparable to those of BA.5 but were greater than those of BA.2. Our multiscale investigations suggest that BA.2.75 acquired virological properties independently of BA.5, and the potential risk of BA.2.75 to global health is greater than that of BA.5.

microbiology↗

bioRxiv2022

SARS-CoV-2 spike S375F mutation characterizes the Omicron BA.1 variant

Recent studies have revealed the unique virological characteristics of Omicron, the newest SARS-CoV-2 variant of concern, such as pronounced resistance to vaccine-induced neutralizing antibodies, less efficient cleavage of the spike protein, and poor fusogenicity. However, it remains unclear which mutation(s) in the spike protein determine the virological characteristics of Omicron. Here, we show that the representative characteristics of the Omicron spike are determined by its receptor-binding domain. Interestingly, the molecular phylogenetic analysis revealed that the acquisition of the spike S375F mutation was closely associated with the explosive spread of Omicron in the human population. We further elucidate that the F375 residue forms an interprotomer pi-pi interaction with the H505 residue in another protomer in the spike trimer, which confers the attenuated spike cleavage efficiency and fusogenicity of Omicron. Our data shed light on the evolutionary events underlying Omicron emergence at the molecular level. HighlightsO_LIOmicron spike receptor binding domain determines virological characteristics C_LIO_LISpike S375F mutation results in the poor spike cleavage and fusogenicity in Omicron C_LIO_LIAcquisition of the spike S375F mutation triggered the explosive spread of Omicron C_LIO_LIF375-H505-mediated {pi}-{pi} interaction in the spike determines the phenotype of Omicron C_LI

microbiology↗