Biology subjects

Watashi, K.

Publications and source records attributed to Watashi, K..

At least 19 recordsLinked to original sources

bioRxiv2026

Systematic analysis of intracellular replication competence of mammalian, avian, and reptilian kolmioviruses.

Kolmioviruses (KoVs) are circular, single-stranded RNA viruses whose evolution may have involved host switching between vertebrate classes. However, the host specificity of their intracellular replication remains poorly understood. Here, we examined six mammalian, one avian, and one reptilian KoVs using cell lines derived from the same three vertebrate classes. We transfected cells with plasmids encoding 1.2x genome-length KoV sequences and assessed persistent replication by monitoring delta antigen-positive cells for up to 18 days. Four mammalian KoVs replicated persistently only in mammalian cell lines, whereas avian and reptilian KoVs replicated persistently only in both avian and reptilian cell lines. By contrast, the remaining two mammalian KoVs, nested within the clade whose deepest lineages are the avian and reptilian KoVs, replicated in cell lines from all three vertebrate classes. The observed patterns of persistent replication are concordant with the phylogenetic grouping of the KoVs. Our findings support a possible evolutionary scenario in which the common ancestor of the two mammalian KoVs in the avian-reptilian clade acquired compatibility with mammalian cells while retaining the capacity to replicate in avian and reptilian cells, contributing to the transition of this lineage to mammalian hosts.

microbiology↗

bioRxiv2026

E3 ubiquitin ligase HUWE1 mediates K6-linked polyubiquitylation and stabilization of Nrf2 in an HBx-dependent manner, thereby inhibit ing hepatitis B virus replication

Hepatitis B virus (HBV) infection remains a major global health burden, and HBV X protein (HBx) plays a central role in modulating host pathways that influence viral replication. We previously reported that the oxidative stress sensor Kelch-like ECH-associated protein 1 (Keap1) recognizes HBx to activate the NF-E2-related factor 2 (Nrf2) signaling pathway to suppress HBV replication. Although canonical K48-linked ubiquitylation is known to control Nrf2 turnover, the contribution of non-canonical ubiquitin linkages to Nrf2 regulation during HBV infection remains unclear. Here, we investigated the role of HECT, UBA, and WWE domain-containing E3 ubiquitin ligase 1 (HUWE1) in the regulation of Nrf2 in the context of HBV replication. Cell-based ubiquitylation assays demonstrated that HUWE1 knockdown reduced HBx-mediated K6-linked polyubiquitylation of Nrf2, while overexpression of wild-type HUWE1, but not the catalytically inactive HUWE1(C4341A) mutant, enhanced it. Coimmunoprecipitation and proximity ligation assays demonstrated that HUWE1 interacts with HBx in the cytoplasm and binds Nrf2 only in the presence of HBx, suggesting that HBx promotes the interaction between HUWE1 and Nrf2. Cycloheximide chase assays demonstrated that HUWE1 knockdown destabilized Nrf2 in HBx-expressing cells. Furthermore, depletion or pharmacological inhibition of HUWE1 increased intracellular HBV RNA and pgRNA levels as well as extracellular HBV DNA and HBsAg levels in HBV-infected cells. Collectively, these results support a model in which HUWE1 mediates HBx-dependent K6-linked polyubiquitylation and stabilization of Nrf2 to restrict HBV replication. This study expands current understanding of non-canonical ubiquitin signaling in HBV-host interactions. DATA SUMMARYAll data are presented in the main figures. The data that support the findings of this study is available at bioRxiv (https://doi.org/10.64898/2026.04.20.719611). Raw sequencing data, microscopy images, materials, and sequence information are available upon request. Correspondence and requests for materials should be addressed to Professor Ikuo Shoji. IMPACT STATEMENTHepatitis B virus (HBV) chronically infects approximately 254 million people worldwide, yet host mechanisms that restrict viral replication remain incompletely understood. The Keap1/ Nrf2 signaling pathway is a central defense against oxidative stress. Under basal conditions, Nrf2 is targeted for degradation via Keap1/Cullin3-mediated K48-linked polyubiquitylation. Here, we provide evidence that the E3 ubiquitin ligase HUWE1 contributes to HBx-dependent K6-linked polyubiquitylation and stabilization of Nrf2. Our findings support a model in which non-canonical ubiquitin signaling helps shape the HBV-host interactions and contributes to suppression of viral replication. This study extends current understanding of the ubiquitin code in HBV infection and highlights HUWE1 as a candidate component of an anti-HBV regulatory pathway.

microbiology↗

bioRxiv2026

A macrocyclic peptide-based fusion inhibitor targeting SARS-CoV-2 Spike S2 subunit

Continuous emergence of SARS-CoV-2 variants carrying mutations in Spike presents a significant challenge for durable antiviral agents. Here we screen for random 13-amino acid non-mimetic macrocyclic peptides that bind to Spike and identify PA-001 that inhibits SARS-CoV-2 infection with high potency at 0.23-2.9 nM as 50% inhibitory concentration (IC50). PA-001 bound to Spike S2 subunit and inhibited the membrane fusion during virus entry. Through drug-resistant selection, we revealed that PA-001 targeted the fusion peptide proximal region (FPPR) in S2, which has not been recognized as a drug target to date. Consistent with its highly conserved amino acid sequences beyond strains, PA-001 exhibited broad antiviral activity against all tested SARS-CoV-2 variants, in contrast to clinically-approved S1-targeting antibodies that lost activity to Omicron variants. PA-001 suppressed SARS-CoV-2 propagation and disease progression in mouse- and hamster-infection models, both by administration prophylactically and therapeutically. Combination therapy with remdesivir further enhanced antiviral profiles. In clinical phase-I trial, PA-001 was well-tolerated and showed high systemic exposure, with 4,300-10,300-fold concentration of IC50 as maximum plasma concentration by single administration to healthy volunteers. These evidence propose FPPR as an unexpected antiviral drug target accessible by macrocyclic peptides and identify PA-001 as a potent anti-SARS-CoV-2 fusion inhibitor.

microbiology↗

bioRxiv2026

Disruption of the NTCP-EGFR receptor complex as a strategy for selective inhibition of hepatitis B and D virus entry

Hepatitis B and D virus (HBV, HDV) enter hepatocytes through a coordinated process mediated by a receptor complex consisting of sodium taurocholate co transporting polypeptide (NTCP) and its entry cofactors, including epidermal growth factor receptor (EGFR). Here, we established an in vitro assay to evaluate the NTCP-EGFR interaction and identified Oxy229, an oxysterol-based compound that disrupted this molecular interaction. Oxy229 selectively inhibited HBV and HDV infection to HepG2-NTCP cells and primary human hepatocytes. Mechanistic analysis revealed that Oxy229 impaired the relocalization of the HBV-NTCP complex from plasma membrane to intracellular vesicles. Notably, Oxy229 did not compromise the physiological functions of NTCP and EGFR, i.e., bile acid transport and activation of downstream EGFR signaling pathways including Ras-MAPK and PI3K-Akt pathways, indicating selective inhibition of viral entry. Compound derivative analysis identified Oxy283, which acquired dual inhibitory activity against both NTCP-EGFR interaction and NTCP multimerization, resulting in enhanced anti-HBV potency. These findings establish the functional significance of the NTCP-receptor complex formation in HBV/HDV entry and highlight this machinery as a potential target for antiviral intervention.

microbiology↗

bioRxiv2024

Systematic Discovery of Phage Genes that Inactivate Bacterial Immune Systems

Bacteria have developed numerous defense systems to counter phage infections. However, the extent to which phages possess countermeasures against these defense systems remains unclear. In this study, we combined a phage gene knockout library with a defense system library to analyze the mechanisms by which phages counteract bacterial defense systems. After attempting gene deletions of 105 open reading frames (ORFs) in the DruSM1 phage ({Phi}DruSM1), we successfully generated 73 different ORF knockout phages. By infecting this library with bacteria harboring defense system expression plasmids, we identified inactivators of Druantia type I (Druad1), Brex type I, AVAST type III, Sir2+HerA, DUF4297+HerA, and hhe, as well as an activator of Retron Ec86, in a single phage genome. Synthetic phages incorporating Druad1 effectively eradicated Escherichia coli harboring the robust Druantia type I defense system by altering DNA methylation at m6A sites of the phage. This study highlighted the prevalence of various antidefense mechanisms employed by phages to overcome bacterial defense systems.

microbiology↗

bioRxiv2024

Stratification of viral shedding patterns in saliva of COVID-19 patients

Living with COVID-19 requires continued vigilance against the spread and emergence of variants of concern (VOCs). Rapid and accurate saliva diagnostic testing, alongside basic public health responses, is a viable option contributing to effective transmission control. Nevertheless, our knowledge regarding the dynamics of SARS-CoV-2 infection in saliva is not as advanced as our understanding of the respiratory tract. Here we analyzed longitudinal viral load data of SARS-CoV-2 in saliva samples from 144 patients with mild COVID-19 (a combination of our collected data and published data). Using a mathematical model, we quantified individual-level viral dynamics and stratified them into three groups using a clustering approach. Notably, the three groups exhibited distinct differences viral RNA detection durations: 11.5 days (95% CI: 10.6 to 12.4), 17.4 days (16.6 to 18.2), and 30.0 days (28.1 to 31.8), respectively. Surprisingly, this stratified grouping remained unexplained despite our analysis of 47 types of clinical data, including basic demographic information, clinical symptoms, results of blood tests, and vital signs. Additionally, we quantified the expression levels of 92 micro-RNAs in a subset of saliva samples, but these also failed to explain the observed stratification, although the mir-1846 level may have been weakly correlated with peak viral load. Our study provides insights into SARS-CoV-2 infection dynamics in saliva, highlighting the challenges in predicting the duration of viral RNA detection without indicators that directly reflect an individuals immune response, such as antibody induction. Given the significant individual heterogeneity in the kinetics of saliva viral shedding, identifying biomarker(s) for viral shedding patterns will be crucial for improving public health interventions in the era of living with COVID-19.

microbiology↗

bioRxiv2023

Multiscale modeling of HBV infection integrating intra- and intercellular viral propagation for analyzing extracellular viral markers

Chronic infection of hepatitis B virus (HBV) is caused by the persistence of closed circular DNA (cccDNA) in the nucleus of infected hepatocytes. Despite available therapeutic anti-HBV agents, eliminating the cccDNA remains challenging. The quantifying and understanding dynamics of cccDNA are essential for developing effective treatment strategies and new drugs. However, it requires a liver biopsy to measure the intrahepatic cccDNA, which is basically not accepted because of the ethical aspect. We here aimed to develop a non-invasive method for quantifying cccDNA in the liver using surrogate markers present in peripheral blood. We constructed a multiscale mathematical model that explicitly incorporates both intracellular and intercellular HBV infection processes. The model, based on age-structured partial differential equations (PDEs), integrates experimental data from in vitro and in vivo investigations. By applying this model, we successfully predicted the amount and dynamics of intrahepatic cccDNA using specific viral markers in serum samples, including HBV DNA, HBsAg, HBeAg, and HBcrAg. Our study represents a significant step towards advancing the understanding of chronic HBV infection. The non-invasive quantification of cccDNA using our proposed methodology holds promise for improving clinical analyses and treatment strategies. By comprehensively describing the interactions of all components involved in HBV infection, our multiscale mathematical model provides a valuable framework for further research and the development of targeted interventions.

microbiology↗

bioRxiv2023

Viruses encode tRNA and anti-retron to evade bacterial immunity

Retrons are bacterial genetic retroelements that encode reverse transcriptase capable of producing multicopy single-stranded DNA (msDNA) and function as antiphage defense systems. Phages employ several strategies to counter the host defense systems, but no mechanisms for evading retrons are known. Here, we show that tRNATyr and Rad (retron anti-defense) of T5 phage family inhibit the defense activity of retron 78 and a broad range of retrons, respectively. The effector protein of retron 78, ptuAB, specifically degraded tRNATyr leading abortive infection, but phage countervailed this defense by supplying tRNATyr. Rad inhibited retron function by degrading noncoding RNA, the precursor of msDNA. In summary, we demonstrated that viruses encode at least two independent strategies for overcoming bacterial defense systems: anti-defense, such as Rad, and defense canceler, like tRNA.

microbiology↗

bioRxiv2022

Identification of inosine monophosphate dehydrogenase as a potential target for anti-monkeypox virus agents

Monkeypox virus (MPXV) is a neglected zoonotic pathogen that caused a worldwide outbreak in May 2022. Given the lack of an established therapy, the development of an anti-MPXV strategy is of vital importance. To identify drug targets for the development of anti-MPXV agents, we screened a chemical library using an MPXV infection cell assay and found that gemcitabine, trifluridine, and mycophenolic acid (MPA) inhibited MPXV propagation. These compounds showed broad-spectrum anti-orthopoxvirus activities and presented lower 90% inhibitory concentrations (0.032-1.40 M) than brincidofovir, an approved anti-smallpox agent. These three compounds have been suggested to target the post-entry step to reduce the intracellular production of virions. Knockdown of inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme of guanosine biosynthesis and a target of MPA, dramatically reduced MPXV DNA production. Moreover, supplementation with guanosine recovered the anti-MPXV effect of MPA, suggesting that IMPDH and its guanosine biosynthetic pathway regulate MPXV replication. By targeting IMPDH, we identified a series of compounds with stronger anti-MPXV activity than MPA. These evidences propose that IMPDH is a potential target for the development of anti-MPXV agents. ImportanceMonkeypox is a zoonotic disease caused by infection with the monkeypox virus, and a worldwide outbreak occurred in May 2022. The smallpox vaccine has recently been approved for clinical use against monkeypox in the United States. Although brincidofovir and tecovirimat are drugs approved for the treatment of smallpox by the U.S. Food and Drug Administration, their efficacy against monkeypox has not been established. Moreover, these drugs may present negative side effects. Therefore, new anti-monkeypox virus agents are needed. This study revealed that gemcitabine, trifluridine, and mycophenolic acid inhibited monkeypox virus propagation, exhibited broad-spectrum anti-orthopoxvirus activities. We also suggested inosine monophosphate dehydrogenase as a potential target for the development of anti-monkeypox virus agents. By targeting this molecule, we identified a series of compounds with stronger anti-monkeypox virus activity than mycophenolic acid.

microbiology↗

bioRxiv2022

Prediction of elimination of intrahepatic cccDNA in hepatitis B virus-infected patients by a combination of noninvasive viral markers

Evaluation of intrahepatic covalently closed circular DNA (cccDNA) is a key for searching an elimination of hepatitis B virus (HBV) infection. HBV RNA and HBV core-related antigen have been proposed as surrogate markers for evaluating cccDNA activity, although they do not necessarily estimate the amount of cccDNA. Here, we developed a novel multiscale mathematical model describing intra- and inter-cellular viral propagation, based on the experimental quantification data in both HBV-infected cell culture and humanized mouse models. We applied it to HBV-infected patients under treatment and developed a model which can predict intracellular HBV dynamics only by use of noninvasive extracellular surrogate biomarkers. Importantly, the model prediction of the amount of cccDNA in patients over time was confirmed to be well-correlated with the liver biopsy data. Thus, our noninvasive method enables to predict the amount of cccDNA in patients and contributes to determining the treatment endpoint required for elimination of intrahepatic cccDNA.

microbiology↗

bioRxiv2022

Potential anti-monkeypox virus activity of atovaquone, mefloquine, and molnupiravir, and their potential use as treatments

Monkeypox virus (MPXV) is a zoonotic orthopoxvirus that causes smallpox-like symptoms in humans and caused an outbreak in May 2022 that led the WHO to declare global health emergency. In this study, from a screening of approved-drug libraries using an MPXV infection cell system, atovaquone, mefloquine, and molnupiravir exhibited anti-MPXV activity, with 50% inhibitory concentrations of 0.51-5.2 M, which is more potent than cidofovir. Whereas mefloquine was suggested to inhibit viral entry, atovaquone and molnupiravir targeted post-entry process to impair intracellular virion accumulation. Inhibitors of dihydroorotate dehydrogenase, an atovaquones target enzyme, showed conserved anti-MPXV activities. Combining atovaquone with tecovirimat enhanced the anti-MPXV effect of tecovirimat. Quantitative mathematical simulations predicted that atovaquone can promote viral clearance in patients by seven days at clinically relevant drug concentrations. Moreover, atovaquone and molnupiravir exhibited pan-Orthopoxvirus activity against vaccinia and cowpox viruses. These data suggest that atovaquone would be potential candidates for treating monkeypox.

microbiology↗

bioRxiv2022

An ACAT inhibitor regulates SARS-CoV-2 replication and antiviral T cell activity

The severity of disease following infection with SARS-CoV-2 is determined by viral replication kinetics and host immunity, with early T cell responses and/or suppression of viraemia driving a favourable outcome. Recent studies have uncovered a role for cholesterol metabolism in the SARS-CoV-2 life cycle and in T cell function. Here we show that blockade of the enzyme Acyl-CoA:cholesterol acyltransferase (ACAT) with Avasimibe inhibits SARS-CoV-2 entry and fusion independent of transmembrane protease serine 2 expression in multiple cell types. We also demonstrate a role for ACAT in regulating SARS-CoV-2 RNA replication in primary bronchial epithelial cells. Furthermore, Avasimibe boosts the expansion of functional SARS-CoV-2-specific T cells from the blood of patients sampled in the acute phase of infection. Thus, re-purposing of available ACAT inhibitors provides a compelling therapeutic strategy for the treatment of COVID-19 to achieve both antiviral and immunomodulatory effects.

immunology↗

bioRxiv2022

Different efficacies of neutralizing antibodies and antiviral drugs on SARS-CoV-2 Omicron subvariants, BA.1 and BA.2

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron subvariant BA.2 has spread in many countries, replacing the earlier Omicron subvariant BA.1 and other variants. Here, using a cell culture infection assay, we quantified the intrinsic sensitivity of BA.2 and BA.1 compared with other variants of concern, Alpha, Gamma, and Delta, to five approved-neutralizing antibodies and antiviral drugs. Our assay revealed the diverse sensitivities of these variants to antibodies, including the loss of response of both BA.1 and BA.2 to casirivimab and of BA.1 to imdevimab. In contrast, EIDD-1931 and nirmatrelvir showed a more conserved activities to these variants. The viral response profile combined with mathematical analysis estimated differences in antiviral effects among variants in the clinical concentrations. These analyses provide essential evidence that gives insight into variant emergences impact on choosing optimal drug treatment.

microbiology↗

bioRxiv2021

Dasabuvir inhibits human norovirus infection in human intestinal enteroids

Human noroviruses (HuNoVs) are acute viral gastroenteritis pathogens that affect all age groups, yet no approved vaccines and drugs to treat HuNoV infection are available. In this study, with a human intestinal enteroid (HIE) culture system where HuNoVs are able to replicate reproducibly, we screened an antiviral compound library to identify compound(s) showing anti-HuNoV activity. Dasabuvir, which has been developed as an anti-hepatitis C virus agent, was found to inhibit HuNoV infection in HIEs at micromolar concentrations. Dasabuvir also inhibited severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and human A rotavirus (RVA) infection in HIEs. To our knowledge, this is the first study to screen an antiviral compound library for HuNoV using HIEs and we successfully identified dasabuvir as a novel anti-HuNoV inhibitor that warrants further investigation.

microbiology↗

bioRxiv2021

Circadian regulation of SARS-CoV-2 infection in lung epithelial cells

The COVID-19 pandemic, caused by SARS-CoV-2 coronavirus, is a global health issue with unprecedented challenges for public health. SARS-CoV-2 primarily infects cells of the respiratory tract, via Spike glycoprotein binding angiotensin-converting enzyme (ACE2). Circadian rhythms coordinate an organisms response to its environment and can regulate host susceptibility to virus infection. We demonstrate a circadian regulation of ACE2 in lung epithelial cells and show that silencing BMAL1 or treatment with a synthetic REV-ERB agonist SR9009 reduces ACE2 expression and inhibits SARS-CoV-2 entry. Treating infected cells with SR9009 limits viral replication and secretion of infectious particles, showing that post-entry steps in the viral life cycle are influenced by the circadian system. Transcriptome analysis revealed that Bmal1 silencing induced a wide spectrum of interferon stimulated genes in Calu-3 lung epithelial cells, providing a mechanism for the circadian pathway to dampen SARS-CoV-2 infection. Our study suggests new approaches to understand and improve therapeutic targeting of SARS-CoV-2.

microbiology↗

bioRxiv2021

Identification of anti-severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) oxysterol derivatives in vitro

Development of effective antiviral drugs targeting the severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) are urgently needed to combat the coronavirus disease 2019 (COVID-19). Oxysterols, defined as oxidized derivatives of cholesterol, include endogenous (naturally occurring) cholesterol metabolites as well as semi-synthetic oxysterol derivatives. We have previously studied the use of semi-synthetic oxysterol derivatives as drug candidates for inhibition of cancer, fibrosis, and bone regeneration. In this study, we have screened a panel of naturally occurring and semi-synthetic oxysterol derivatives for anti-SARS-CoV-2 activity, using a cell culture infection assay. We show that the natural oxysterols, 7-ketocholesterol, 22(R)-hydroxycholesterol, 24(S)-hydroxycholesterol, and 27-hydroxycholesterol, substantially inhibited SARS-CoV-2 propagation in cultured cells. Among semi-synthetic oxysterols, Oxy186 displayed antiviral activity comparable to natural oxysterols. In addition, related oxysterol analogues Oxy210 and Oxy232 displayed more robust anti-SARS-CoV-2 activities, reducing viral replication more than 90% at 10 M and 99% at 15 M, respectively. When orally administered in mice, peak plasma concentrations of Oxy210 fall into a therapeutically relevant range (19 M), based on the dose-dependent curve for antiviral activity in our cell culture infection assay. Mechanistic studies suggest that Oxy210 reduced replication of SARS-CoV-2 with disrupting the formation of double membrane vesicles (DMVs), intracellular membrane compartments associated with viral replication. Oxy210 also inhibited the replication of hepatitis C virus, another RNA virus whose replication is associated with DMVs, but not the replication of the DMV-independent hepatitis D virus. Our study warrants further evaluation of Oxy210 and Oxy232 as a safe and reliable oral medication, which could help protect vulnerable populations with increased risk developing COVID-19.

microbiology↗

bioRxiv2020

Anti-severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) potency of Mefloquine as an entry inhibitor in vitro

Coronavirus disease 2019 (COVID-19) has caused serious public health, social, and economic damage worldwide and effective drugs that prevent or cure COVID-19 are urgently needed. Approved drugs including Hydroxychloroquine, Remdesivir or Interferon were reported to inhibit the infection or propagation of severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2), however, their clinical efficacies have not yet been well demonstrated. To identify drugs with higher antiviral potency, we screened approved anti-parasitic/anti-protozoal drugs and identified an anti-malarial drug, Mefloquine, which showed the highest anti-SARS-CoV-2 activity among the tested compounds. Mefloquine showed higher anti-SARS-CoV-2 activity than Hydroxychloroquine in VeroE6/TMPRSS2 and Calu-3 cells, with IC50 = 1.28 M, IC90 = 2.31 M, and IC99 = 4.39 M in VeroE6/TMPRSS2 cells. Mefloquine inhibited viral entry after viral attachment to the target cell. Combined treatment with Mefloquine and Nelfinavir, a replication inhibitor, showed synergistic antiviral activity. Our mathematical modeling based on the drug concentration in the lung predicted that Mefloquine administration at a standard treatment dosage could decline viral dynamics in patients, reduce cumulative viral load to 7% and shorten the time until virus elimination by 6.1 days. These data cumulatively underscore Mefloquine as an anti-SARS-CoV-2 entry inhibitor.

microbiology↗

bioRxiv2020

Identifications of novel avian and mammalian deltaviruses filled the large evolutionally gaps and revealed inter-family transmission of deltaviruses

Hepatitis delta virus (HDV) is a satellite virus that requires hepadnavirus envelope proteins for its transmission. Although recent studies identified HDV-related deltaviruses in certain animals, the evolution of deltaviruses, such as the origin of HDV and the mechanism of its coevolution with its helper viruses, is unknown, mainly because of the phylogenetic gaps among deltaviruses. Here we identified novel deltaviruses of passerine birds, woodchucks, and white-tailed deer by extensive database searches and molecular surveillance. Phylogenetic and molecular epidemiological analyses suggest that HDV originated from mammalian deltaviruses and the past interspecies transmission of mammalian and passerine deltaviruses. Further, metaviromic and experimental analyses suggest that the satellite-helper relationship between HDV and hepadnavirus was established after the divergence of the HDV lineage from non-HDV mammalian deltaviruses. Our findings enhance our understanding of deltavirus evolution, diversity, and transmission, indicating the importance of further surveillance for deltaviruses.

microbiology↗