Membrane-anchored #influenza #neuraminidase vaccine drives #human-like broadly protective B cell responses

 

Abstract

Influenza neuraminidase (NA) is a promising target for universal flu vaccines, yet eliciting potent B-cell responses against its conserved epitopes remains challenging. Here, we developed a membrane-anchored, folding-domain-free NA (mNA) that elicited superior head-specific germinal center B cell and antibody responses compared to soluble tetrameric NA. In non-human primates, mNA immunization induced cross-reactive memory B cell (MBC) responses, expanding clones with the conserved DR motif in HCDR3, a hallmark of human broadly reactive NA antibodies. These MBCs conferred cross-inhibitory activity against diverse NA variants and in vivo cross-protection. Cryo-EM analysis revealed that the 554-C2 clone targets the conserved enzymatic pocket via the DR motif, while the 554-C1 clone recognizes previously uncharacterized epitopes at the interface between two adjacent N2 monomers, effectively reducing plaque formation by contemporary H3N2 strains. Our findings highlight the immunological advantages of membrane-anchoring, providing a robust strategy for designing next-generation vaccines against influenza and other pathogens.

Competing Interest Statement

Westlake University has filed for patent protection for mNA used as an influenza vaccine.

Funder Information Declared

State Key Laboratory of Gene Expression, SKLGE-ZX-2025007

Zhejiang Provincial Key Laboratory Construction Project, 2024ZY01026, 2024E10060, 2024E10052

Natural Science Foundation of Zhejiang province, LR26H190001

National Natural Science Foundation of China, 82471855, 825B2062, 82330054, 82502209, 32471303

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.05.13.724804v1

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G4 #Eurasian avian-like #H1N1 swine #influenza viruses exhibit enhanced #pathogenicity potential in mice and #pigs

 

Abstract

Currently circulating swine influenza viruses (SIVs) mainly include H1N1, H1N2, and H3N2 subtypes. In this study, two G4 genotype Eurasian avian-like (EA) H1N1 SIVs were isolated from 556 samples collected between 2023 and 2026. A systematic analysis was conducted on the two EA H1N1 isolates (FYD30 and YZF69) to assess their pandemic potential. The hemagglutinin (HA) proteins of both H1N1 viruses possessed residues 225E and 228S, indicating enhanced affinity for human-like alpha-2,6-linked sialic acid receptors, which was confirmed by receptor-binding assays. Polymerase activity tests demonstrated that the two SIVs exhibited significantly higher activity in mammalian cells, relative to avian cells, which is consistent with the efficient replication in mammalian cells. Challenge experiments revealed that both H1N1 caused significant pathogenicity in mice and pigs, with YZF69 exhibited higher virulence than FYD30. The higher virulence of YZF69 may be attributed to its molecular features, including the NP Q357K mutation, and an additional glycosylation site in HA. In conclusion, currently circulating EA H1N1 SIVs have acquired key molecular signatures of mammalian adaptation, exhibit enhanced virulence in mammals, and continue to undergo extensive reassortment driven by international swine trade. These findings highlight the potential pandemic risk of SIVs and underscore the urgent need for strengthened surveillance.

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.05.12.724537v1

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The Decline in #Influenza #Antibody Titers and Modifiers of #Vaccine #Immunity from over Ten Years of Serological Data

 

Abstract

Annual influenza vaccination is the cornerstone for seasonal protection, yet antibody responses are highly variable across individuals and over time. To systematically assess the determinants of this heterogeneity, we compiled 20,449 hemagglutination inhibition and neutralization titers from 4,540 participants enrolled in 14 new vaccine studies we conducted and 50 prior studies that collectively span 2010-2023. Seasonal effects dominated, with pre- and post-vaccination titers declining steadily from 2017 onwards, outweighing the influence of age, sex, or repeated vaccination. Titers to B Yamagata remained steady throughout all years examined, suggesting unique durability and offering a reason for lineage extinction. Vaccine timing emerged as a strong and previously underappreciated determinant of immunity, with individuals vaccinated later in the season exhibiting larger post-vaccination titers. Not being vaccinated or receiving the live-attenuated FluMist vaccine in one year significantly enhanced the response to inactivated vaccines in 45% or 68% of cohorts, respectively, whereas antigen dose and adjuvants had modest impact. These findings identify vaccine timing and seasonal context as underrecognized drivers of immunogenicity and provide actionable insights for optimizing influenza vaccination strategies.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

This research was supported by the the National Institute of Allergy and Infectious Diseases (NIAID) of the National Institutes of Health (NIH) under the Computational Models of Influenza Immunity (U01 AI187062), LJI & Kyowa Kirin, Inc. (KKNA - Kyowa Kirin North America), and the Bodman family (TE).

Source: 

Link: https://www.medrxiv.org/content/10.64898/2026.01.07.25342310v2

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#USA, One #human #infection with influenza #H1N2 #variant virus was reported by #Nebraska (US CDC, May 8 '26)

 

{Excerpt}

(...)

The patient, who is <18 years of age, initially developed respiratory illness during the week ending April 4, 2026 (Week 13). 

The patient sought healthcare during the week ending April 18, 2026 (Week 15) with worsening symptoms, was not hospitalized, and has recovered from their illness. 

An investigation by local and state public health officials did not identify direct or indirect swine contact by the patient. 

Additional investigation identified that a close contact developed mild respiratory illness on the same day as the case, but no cases of human infection with A(H1N2)v virus associated with this case have been identified.

This is the second human infection with a variant influenza virus reported in the 2025-2026 season, and the first reported in 2026; both have been influenza A(H1N2)v viruses.

When an influenza virus that normally circulates in swine (but not people) is detected in a person, it is called a "variant" influenza virus. 

Most human infections with variant influenza viruses occur following exposure to swine, but limited, non-sustained, human-to-human transmission has occurred. 

It is important to note that in most cases, variant influenza viruses have not shown the ability to spread easily and sustainably from person to person.

Notification to WHO of this case was completed according to International Health Regulations (IHR). More information regarding IHR can be found at http://www.who.int/topics/international_health_regulations/en/.

(...)

Source: 

Link: https://www.cdc.gov/fluview/surveillance/2026-week-17.html

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Opposing #cell type preferences for binding and #replication shape #influenza A virus infection in #human #airways

 

Abstract

Influenza A viruses (IAVs) pose a persistent threat to human health through seasonal epidemics and zoonotic spillover from avian reservoirs. As respiratory pathogens, they primarily target the airway epithelium. However, it remains unclear how host cell-specific barriers jointly shape viral tropism and replication in primary human airway cultures. Here, we show that avian IAVs can infect ciliated and secretory cells but preferentially bind to ciliated cells, consistent with higher abundance of their receptor alpha2,3-linked sialic acids, specifically sialyl Lewis X glycans, present on the apical surface of ciliated cells. Replication levels were comparable between secretory and ciliated cells for the avian strains, resulting in an overall preference for ciliated cells. In contrast, human IAVs also preferentially bind to ciliated cells but independently of alpha2,6-linked sialic acid abundance. Human IAVs replicate more efficiently than avian IAVs due to their ability to utilize human ANP32 proteins, but they also exhibit cell type-specific differences due to ANP32, allowing for higher viral RNA levels in secretory cells. Thus, preferential binding to ciliated cells coupled with enhanced replication in secretory cells equalizes overall infection levels across cell types for human IAVs. Together, our findings highlight the spatiotemporal complexity and interplay of IAV infection dynamics in the airway epithelium and redefine current models of influenza A virus tropism.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Swiss National Science Foundation, 310030_204166

UZH Candoc, FK-25-039

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.05.04.722582v1

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Characterizing #viral #clearance kinetics in acute #influenza

 

Abstract

Pharmacometric assessment of antiviral efficacy in acute influenza informs treatment decisions and pandemic preparedness. We characterized natural viral clearance in acute influenza to guide phase II trial design using simulations based upon observed data. Standardized duplicate oropharyngeal swabs were collected daily over 14 days from 80 untreated low-risk Thai adults, with viral densities measured using quantitative polymerase chain reaction. We evaluated three models to describe viral clearance: exponential, bi-exponential and growth-and-decay. The growth-and-decay model provided the best fit, but the exponential decay model was the most parsimonious. The median viral clearance half-life was 10.3 h (interquartile range (IQR): 6.8–15.4h), varying by influenza type: 9.6 h (IQR: 6.2–13.0 h) for influenza A and 14.0 h (IQR: 10.3–19.3 h) for influenza B. Simulated trials using parameters from the exponential decay model showed that 148 patients per arm provide over 90% power to detect treatments accelerating viral clearance by 40%. Variation in clearance rates strongly impacted the power; doubling this variation would require 232 patients per arm for an antiviral with a 60% effect size. A sampling strategy with four swabs per day reduces the required sample size to 81 per arm while maintaining over 80% power. We recommend this approach to assess and compare current anti-influenza drugs.

This article is part of the Theo Murphy meeting issue ‘Evaluating anti-infective drugs’.

Source: 

Link: https://royalsocietypublishing.org/rstb/article/381/1949/20240351/481559/Characterizing-viral-clearance-kinetics-in-acute

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#Antiviral treatment for #influenza

 

Abstract

Seasonal influenza is a widespread acute respiratory infection that causes significant illness and death worldwide. Two major antiviral classes are neuraminidase inhibitors (NAIs) and polymerase inhibitors. NAIs, including oseltamivir, zanamivir, peramivir and laninamivir, block viral release, while polymerase inhibitors such as baloxavir disrupt viral RNA replication. Early administration within 48 h of symptom onset reduces illness duration, severity and complications, particularly in high-risk groups. Oseltamivir is the most widely studied NAI, demonstrating reduced viral shedding, faster symptom resolution and lower complication rates, though gastrointestinal side effects are common. Higher doses generally do not improve outcomes compared to standard dosing. Zanamivir is more effective against influenza B and is inhibitory for most influenza A viruses resistant to oseltamivir, but the inhaled formulation is less suitable for patients with severe illness or airway disease. Intravenous (IV) zanamivir is approved for hospitalized influenza patients in some countries. Peramivir offers IV treatment options, while laninamivir is mainly used in Japan. Baloxavir shows superior viral load reduction and comparable symptom relief to oseltamivir in outpatients, though resistance variants can emerge. Favipiravir and newer polymerase inhibitors are under investigation. Combination therapies may enhance recovery, with limited evidence. Overall, timely antiviral use is critical to reducing influenza’s burden.

This article is part of the Theo Murphy meeting issue ‘Evaluating anti-infective drugs’.

Source: 

Link: https://royalsocietypublishing.org/rstb/article/381/1949/20240344/481548/Antiviral-treatment-for-influenza

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Historical #Pandemic and Contemporary #Influenza A Viruses Reveal #PB2 M631L as a Convergent #Adaptation to #Human ANP32

 

Abstract

Understanding the genetic changes that allow avian influenza A viruses (IAVs) to switch their natural hosts and establish productive infection in humans is important for pandemic risk assessment. Adaptations in the IAV polymerase are required to overcome species-specific restrictions imposed by host ANP32 proteins. Notably, avian virus polymerase is generally only poorly supported by human ANP32 proteins due to species-specific differences. Consequently, efficient polymerase adaptation to the binding interface of human ANP32 requires distinct amino acid changes, such as PB2 E627K. A separate adaptation, PB2 M631L, has recently been reported in mammalian-adapted IAV; however, its functional role across divergent viral lineages and its relationship to host ANP32-dependent adaptation remain incompletely defined. Here, we examine PB2 M631L in the polymerases of a 1918 pandemic strain, a recombinant contemporary H1N1pdm09, and a recent clade 2.3.4.4b H5N1 virus. Using polymerase activity and protein-interaction assays, we show that PB2 M631L enhances polymerase activity and ANP32 binding in human—but not avian—contexts, and that this effect is conserved across multiple viral backgrounds. In H1N1pdm09, PB2 M631L also increased virus replication in mammalian cells. These findings indicate that PB2 M631L contributes to enhanced polymerase compatibility with human ANP32 proteins and are consistent with a role in adaptation across multiple influenza virus lineages. Our results highlight how analysis of historical pandemic strains can inform risk assessment for future emerging viruses.

Source: 

Link: https://www.mdpi.com/2076-2607/14/4/859

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The temporal #sequence of #influenza #H1N1 and #Mycoplasma pneumoniae co-infection causes disease severity in Syrian hamster models

 

Abstract

Introduction: 

Influenza H1N1 virus is one of the most prevalent subtypes among influenza viruses, and co-infection with Mycoplasma pneumoniae (Mp) is frequently documented in clinical respiratory infections. However, the pathological mechanisms underlying the temporal sequence of H1N1-Mp co-infection remain poorly characterized, and relevant animal models are lacking.

Methods: 

In this study, we established a model of influenza H1N1 and Mycoplasma pneumoniae co-infection in Syrian hamsters and infected two pathogens in interval of 72 hours. Clinical manifestations, body temperature, body weight, pathogen loads in nasal, pharyngeal, and anal swabs, as well as blood cytokine profiles were dynamically monitored over 14 days post-infection (dpi). Additionally, tissue pathogen loads, histopathological changes, routine blood parameters, and blood biochemistry indicators were evaluated at 7 and 14 dpi.

Results: 

The results demonstrated that hamsters first infected with H1N1 followed by Mp (F-M group) exhibited significantly more severe histopathological lesions (assessed by HE staining), higher pathogen loads, and dysregulated cytokine responses compared to other infection groups.

Conclusion: 

Our findings highlight the critical role of infection order in determining the severity of H1N1-Mp co-infection, providing novel insights into the temporal dynamics and pathogenic mechanisms of respiratory co-infections.

Source: 

Link: https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2026.1787294/full

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Porcine #influenza #mAbs to #H3, #H5, and #H7 hemagglutinins recognize H3 egg adapted site and target the HA stem

 

Abstract

Introduction

Monoclonal antibodies (mAbs) are critical tools for elucidating viral evolution, informing vaccine design, and developing antiviral therapeutics. Large-animal models, such as the pig, that closely mirror human immune responses are essential for understanding influenza immunity.

Methods

Pigs were either infected or sequentially immunized with influenza viruses and monoclonal antibodies directed against H3, H5, and H7 influenza virus haemagglutinins were isolated. Antibody specificity, breadth, epitope targeting (head versus stem), neutralizing capacity, and Fc-mediated activity were assessed across influenza subtypes.

Results

Pigs generated both strain-specific and broadly reactive mAbs targeting haemagglutinin head and stem epitopes. An H3-specific mAb (H3–57) selectively recognized the egg-adapted L194P mutation associated with reduced human vaccine effectiveness. H5 and H7 immunization induced neutralizing antibodies, including cross-group stem mAbs reactive with H1, H3, and H5 haemagglutinins. Fc-mediated activity correlated with antibody binding strength rather than epitope location.

Conclusions

These findings demonstrate that pigs mount antibody responses closely resembling those observed in humans, including recognition of conserved stem epitopes and adaptive head mutations. Porcine mAbs represent powerful new tools for dissecting influenza immunity, guiding vaccine design, and enhancing pandemic preparedness using a physiologically relevant large-animal model.

Source: 

Link: https://academic.oup.com/discovimmunology/article/5/1/kyag006/8503709

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#Oseltamivir aziridines are potent #influenza #neuraminidase #inhibitors and imaging agents

 

Significance

Influenza remains a major global health threat. We introduce oseltamivir-based aziridines that unite transition-state mimicry for tight binding with aziridine-enabled covalent capture of the catalytic tyrosine. This dual function yields potent, mechanism-based neuraminidase inhibition and enables activity-based quantification of active enzyme directly in complex samples. Across N1, N2, and influenza B enzymes, selected compounds show high potency against diverse viral neuraminidases and in live virus replication assays. By combining a clinically grounded scaffold with a reactivity handle, these molecules bridge therapeutic and diagnostic needs and offer a practical platform for neuraminidase imaging and antiviral development.

Abstract

Influenza neuraminidase (NA) is a critical target for seasonal and pandemic antivirals, including the strains of current concern. Current treatments, such as Zanamivir and Oseltamivir, are limited by noncovalent binding and emerging resistance. We hypothesized that Oseltamivir aziridines would unite transition-state mimicry for tight binding, with aziridine-enabled covalent capture of the catalytic tyrosine, thereby supporting both therapy and activity-based quantification. Here, we present oseltamivir-based aziridines, inspired by cyclophellitol chemistry, that act as covalent inhibitors and activity-based probes via an N-acylaziridine warhead. Free-energy calculations, and NMR observations, indicate a 4H5 half-chair preference consistent with the NA transition state, and selected analogues inhibit multiple NA subtypes with low nanomolar binding constants. Diverse evidence establishes covalency: time-dependent inactivation, inhibitor washout, intact-mass shifts, MS/MS identification of a tyrosine adduct, and QM/MM reaction profiles, while cryoEM of N1 aligns with the proposed binding mode, revealing an elimination product. The inhibitors demonstrate formidable activity against diverse viral neuraminidases, including H5N1, and further enable imaging and quantification of active NA. With their dual therapeutic and diagnostic potential, these first-in-class inhibitors indeed benefit from transition state mimicry and covalency, and thus offer a powerful platform for antiviral development and neuraminidase imaging, addressing urgent global health needs in influenza treatment and prevention.

Source: 

Link: https://www.pnas.org/doi/10.1073/pnas.2504045123

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Defining #influenza-specific B cells in #vaccine #responders, non-responders and influenza breakthrough #infections

 

Abstract

Although seasonal influenza vaccination programs are effective at a population level, our data from inactivated influenza vaccine (IIV) cohorts in years 2015-2022 reveal that 50-60% of individuals do not seroconvert following immunization. The underlying mechanisms of vaccine non-responsiveness are far from understood. In this study, we sought to define key determinants of optimal B cell immune responses elicited by seasonal influenza vaccination, and to explore why some individuals fail to elicit humoral immunity following immunization. Immune responses associated with seroconversion and vaccine failure from individuals immunized with IIVs were compared at cellular and molecular levels using single-cell transcriptomics. We analyzed HA-specific B cell immunity across vaccine-responders, breakthrough infections and patients hospitalized with acute influenza. Droplet-based single-cell RNA sequencing and VDJ-sequencing of influenza-specific B cells from stored PBMCs was performed using 10x Genomics. Our results show that atypical B cells are the major subset of B cell responses in vaccine non-responders on day 28 post-vaccination. Conversely, individuals who seroconvert had diverse B cell phenotypes. The use of recombinant influenza-specific HA probes allowed us to dissect expression patterns on influenza HA-specific B cells. We found that HA-specific B cells of vaccine non-responders for A/H1N1 and A/H3N2 components displayed elevated atypical-like markers (CD11c, FcRL-5) at baseline, compared to responders. Analysis of differentially expressed genes (DEGs) between responders and non-responders identified differential expression of HLA-DR, CD74, CD83, and CXCR3 genes. We subsequently demonstrated reduced frequencies of HLA-DR-, CD74- and CD83-expressing B cells in patients hospitalized with influenza, compared to healthy participants. Hospitalized influenza patients also had significantly higher proportions of atypical CD21-CD27- B cells. Overall, our data demonstrate an association between elevated frequencies of atypical-like B cells with both lack of seroconversion following immunization and severe influenza infection. These findings broaden our understanding of humoral immunity in influenza vaccination and infection, providing novel insights for vaccination strategies and design.

Competing Interest Statement

Katherine Kedzierska has received paid honoraria from Pfizer. Hayley McQuilten has a consultancy role for Ena Therapeutics

Funder Information Declared

NHMRC

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.03.19.710321v1

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Developing and #Benchmarking #OneHealth Genomic #Surveillance #Tools for #Influenza A Virus in #Wastewater

 

Abstract

Influenza A viruses (IAV) remain a persistent One Health threat, and whole-genome sequencing from wastewater offers a promising surveillance tool. However, IAV is at low abundance in wastewater, making it difficult to sequence. We benchmarked four targeted enrichment methods suited for whole-genome sequencing including custom and off-the-shelf amplicon and probe-based methods. Our custom HA tiled-amplicon panel was sensitive, fast, and cost-effective, making it suitable for monitoring low-abundance seasonal variants of known subtypes. However, its reliance on conserved and intact primer-binding sites limited primer design to fewer subtypes. A previously published universal amplicon method targeted all IAV subtypes, but it performed poorly in wastewater due to its reliance on intact genome segments. Probe-capture methods were resilient to RNA degradation and mismatches, potentially enabling broader surveillance and detection of emerging strains. However, probes were costly, labor-intensive, and less sensitive than tiled-amplicon. When testing compatibility of sequencing methods with upstream virus concentration and extraction methods, ultrafiltration-based virus concentration outperformed large-volume direct extraction with all four sequencing methods. This set of benchmarking comparisons and custom panels provides needed information for the translation of IAV genomic sequencing into a routine component of wastewater surveillance.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

University of California, Berkeley, L22CR4507

NIH Common Fund, 4R00GM144747-03

Source: 

Link: https://www.biorxiv.org/content/10.1101/2025.09.19.676942v2

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A Tale of Two Lenses: #Emergency department indoor - #air hybrid-capture #metagenomics complements #wastewater by adding a human-focused respiratory #virus perspective

 

Abstract

Background: 

Continuous, non-invasive viral surveillance is essential to monitor emerging pathogens and guide public health responses. Most environmental surveillance studies use targeted qPCR approaches, and comparisons between wastewater and indoor air surveillance remain limited. We aimed to compare the utility of emergency department indoor air and urban wastewater for tracking circulating viruses and resolving genomic information. 

Methods: 

We conducted a matched-pair study comparing 19 weekly indoor air samples from the central ventilation exhaust shaft of an emergency department and 19 24-hour composite municipal wastewater samples in Leuven, Belgium, from December 2024 to April 2025. Both sample sets were processed using probe-based hybrid-capture viral metagenomics targeting over 3000 viral species, using influenza A as a clinically relevant test case. 

Findings: 

Wastewater captured higher overall viral diversity (233 versus 106 species) and more complete genomes compared to indoor air, showing a relatively stable composition, mainly of enteric and animal-associated viruses. Indoor air demonstrated lower overall diversity but was enriched for respiratory viruses, including influenza A, coronaviruses, metapneumovirus, and respiratory syncytial virus, and more frequently achieved high genome coverage for these pathogens. Although both sample types permitted influenza A subtype characterization, influenza A genomes from wastewater were often less well covered. When coverage thresholds were met, indoor air supported targeted antiviral resistance-site screening for influenza A and RSV-A. 

Interpretation: 

Wastewater and indoor air generate distinct but complementary viromes. Wastewater acts as a diverse, population-level monitor for One-Health applications, whereas indoor air serves as a targeted, human-centric sentinel system facilitating further genomic characterization for respiratory viruses.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

Mustafa Karatas is supported by a Research Foundation Flanders (FWO) fundamental research scholarship (number: 11P7I24N). C.G., L.C., E.H., S.G. and E.A. acknowledge support from the DURABLE project. The DURABLE project has been funded by the European Union, under the EU4Health Programme (EU4H), project no. 101102733. Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or the European Health and Digital Executive Agency. Neither the European Union nor the granting authority can be held responsible for them. The computing power in this work was provided by the VSC (Flemish Supercomputer Centre), financed by the FWO and the Flemish government department EWI.

Source: MedRxIV, https://www.medrxiv.org/

Link: https://www.medrxiv.org/content/10.64898/2026.03.13.26348311v1

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#Immunity to #hemagglutinin and #neuraminidase results in additive reductions in #airborne #transmission of #influenza #H1N1 virus in #ferrets

 

Abstract

Currently, there is limited knowledge on the impact of immunity to hemagglutinin (HA) and/or neuraminidase (NA) on the transmission of influenza viruses. Therefore, using intramuscular vaccination, intranasal vaccination, or infection with reassortant viruses, we induced immunity to each antigen alone or both antigens combined in ferrets. We then assessed transmission of the 2009 pandemic H1N1 virus from these ferrets to naïve respiratory contacts. For all strategies used to induce immunity, combined immunity to HA and NA resulted in the largest reductions in transmission. Moreover, immunity to HA and NA conferred additive rather than synergistic reductions in transmission. No escape variants emerged in our transmission studies, and logistical regression showed that the probability of transmission was less than 50% when viral titers in donors were reduced to 101.5 and 102 median tissue culture infectious dose per ml on days 1 and 3 postinfection, respectively. These studies define the relationship between immunity to HA and NA on transmission and identify a threshold titer indicative of decreased transmission in ferrets.

Source: 

Link: https://www.science.org/doi/10.1126/sciadv.aea8719

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Systematic Identification of the Functional lncRNAs During #H7N9 Avian #Influenza Virus #Infection in Mice

 

Abstract

Accumulating studies have identified the pivotal role of long non-coding RNAs (lncRNAs) in participating in host–virus interactions during virus infections. However, the regulatory roles of lncRNAs in influenza A virus (IAV) infection are still not fully elucidated. In this study, using high-throughput sequencing, we comprehensively compared the expression profiles of lncRNAs and mRNAs in mouse lungs infected either with the nonpathogenic parental (SDL124) H7N9 virus or its moderately pathogenic mouse-adapted (S8) variant. A total of 7636 significantly differentially expressed (SDE) lncRNAs were obtained in the S8-infected group compared to the mock group. As for the SDL124 group, 1042 SDE lncRNAs were identified. Subsequently, the mRNAs co-expressed with SDE lncRNAs were subjected to functional annotation and pathway enrichment analysis. The results indicated that the target mRNAs regulated by the S8 virus were mainly enriched in various immunological processes and exhibited a strong correlation with inflammatory-related signaling pathways. Moreover, 12 lncRNAs and 10 mRNAs co-expressed with SDE lncRNAs were selected and successfully verified by RT-qPCR. Among these lncRNAs, NONMMUG032982.2 and NONMMUG032328.2 exhibited strong antiviral activity against IAV. Additionally, these two lncRNAs were chosen for further in-depth bioinformatics analysis, including transcription factor prediction, coding capacity assessment, genomic location, construction of secondary structure, and prediction of potential interacting proteins. Taken together, these findings provide a cluster of lncRNAs probably associated with the virulence of IAV in mice and shed light on the anti-IAV effects of two functional lncRNAs, establishing a molecular foundation for further exploring the regulatory mechanisms of lncRNAs in IAV infection.

Source: Viruses, https://www.mdpi.com/journal/viruses

Link: https://www.mdpi.com/1999-4915/18/3/353

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Structural #insights into #antibody responses against #influenza A virus in its natural reservoir

 

Abstract

While influenza A virus undergoes rapid antigenic drift in humans, at least some subtypes, such as H3, have relatively stable antigenicity in natural waterfowl reservoirs, despite the presence of immune pressure. However, the underlying mechanisms remain poorly understood. This study identified and characterized 187 antibodies to H3 hemagglutinin from experimentally infected mallard ducks, 18 of which were further analyzed by cryo-EM. Compared with human H3 antibodies, duck H3 antibodies exhibited higher glycan-binding propensity, more balanced immunodominance hierarchy, and targeted distinct epitopes. Other unique features of duck H3 antibodies included a convergent CDR H3-independent heavy chain-only binding mode and an N-glycosylated CDR H3 as decoy receptor. By annotating duck immunoglobulin germline genes, we also demonstrated the importance of gene conversion in duck H3 antibodies. Overall, our findings provide insights into how millennia of coevolution have shaped the interplay between influenza A virus antigenic drift and antibody responses in the natural reservoir.

Competing Interest Statement

N.C.W. consults for HeliXon. The authors declare no other competing interests.

Funder Information Declared

National Institutes of Health, https://ror.org/01cwqze88, R01 AI165692

Carl R. Woese Institute for Genomic Biology, Carl R. Woese Institute for Genomic Biology Postdoctoral Fellowship

Vallee Foundation, https://ror.org/05nmp3276, Vallee Scholars Program

Foundation for Partnership Initiatives in the Niger Delta, https://ror.org/041nz5a71, Searle Scholars Program

Howard Hughes Medical Institute, https://ror.org/006w34k90, Emerging Pathogens Initiative

Source: BioRxIV, https://www.biorxiv.org/

Link: https://www.biorxiv.org/content/10.64898/2026.03.11.711171v1

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Identification of a Key #Hemagglutinin #Mutation Mediating #Antibody Escape in #Influenza #H1N1pdm09 Viruses

 

Abstract

Background: 

The H1N1 influenza A virus evades host immunity through continuous antigenic drift, posing a significant challenge to broad-spectrum neutralizing antibody therapies. This study aims to systematically evaluate the neutralizing capacity of the broad-spectrum antibody C12H5 against H1N1 strains from different eras and identify key immune escape mutation sites. 

Methods: 

Three representative H1N1 virus strains from 2009, 2018, and 2023 were selected. An antigen–antibody binding prediction model based on the ESM-2 large language model was constructed by integrating 48,762 GISAID sequence data and deep mutation scanning data from the Bloom laboratory. Candidate escape sites were screened using SHAP (SHapley Additive exPlanations) value analysis. Mutant viruses were constructed via reverse genetics, and their neutralizing capacity and replication fitness were validated through hemagglutination inhibition assays, microneutralization assays, and viral growth kinetics analysis. 

Results: 

Machine learning scoring identified five potential escape sites, with K147 exhibiting the highest overall score (0.92). SHAP analysis revealed that the K147 site within the HA protein’s 130-loop region received the highest importance score (0.28), significantly surpassing other candidate sites. Experimental validation revealed that the K147N mutation reduced neutralizing potency against C12H5 by 8-fold (from 1:1024 to 1:128) and approximately 6-fold in microneutralization assays (from 8.3 log2 to 5.7 log2), while exhibiting a replication advantage in MDCK cells. Microneutralization assays further confirmed an approximately 6-fold reduction in neutralization sensitivity. Structural analysis indicated that K147 is located at the periphery of the HA receptor-binding domain, immediately adjacent to the receptor-binding site. 

Conclusions: 

K147N is identified as the critical mutation mediating C12H5 immune escape, and this mutation has emerged in 2023 circulating strains. This study provides important molecular targets and early warning mechanisms for broad-spectrum antibody optimization and influenza vaccine updates.

Source: 

Link: https://www.mdpi.com/1999-4915/18/3/349

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Mechanism of co-transcriptional cap snatching by #influenza #polymerase

 

Abstract

Influenza virus mRNAs are stable and competent for nuclear export and translation because they receive a 5′ cap(1) structure in a process called cap snatching1. During cap snatching, the viral RNA-dependent RNA polymerase (FluPol) binds to host RNA polymerase II (Pol II) and the emerging transcript2,3. The FluPol endonuclease then cleaves a capped RNA fragment that subsequently acts as a primer for the transcription of viral genes4,5. Here we present the cryogenic electron microscopy structure of FluPol bound to a transcribing Pol II in complex with the elongation factor DSIF in the pre-cleavage state. The structure shows that FluPol directly interacts with both Pol II and DSIF, positioning the FluPol endonuclease domain near the RNA exit channel of Pol II. These interactions are important for the endonuclease activity of FluPol and FluPol activity in cells. A second structure, trapped after cap snatching, shows that the cleaved capped RNA rearranges within FluPol, directing the capped RNA 3′ end toward the FluPol polymerase active site for viral transcription initiation. Together, our results provide the molecular mechanisms of co-transcriptional cap snatching by FluPol.

Source: 

Link: https://www.nature.com/articles/s41586-026-10189-0

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#Zanamivir - #Amantadine Conjugate: A Dual-Action Agent with Broad-Spectrum Synergistic #Antiviral Efficacy

 

Abstract

Influenza A virus is a highly contagious respiratory pathogen, and its rapid and continuous adaptive mutations for immune escape have limited the efficacy of existing vaccines and antiviral drugs. Here, we report a multimechanism anti-influenza platform based on the conjugation of zanamivir (ZMV) with amantadine (Aman). Aman acts as a hydrophobic tag that promotes the degradation of neuraminidase and concurrently enhances the physicochemical properties of ZMV, leading to improved membrane permeability and a significantly prolonged half-life. Meanwhile, the ZMV moiety counteracts Aman-induced cytotoxic autophagy. The resulting conjugate, compound 7j, exhibits potent activity against a wide range of neuraminidase and M2 ion channel mutations. Notably, a single intravenous dose of 7j fully protected mice from a lethal H1N1 challenge. Our work demonstrates that the rational fusion of ZMV and Aman achieves synergistic multimechanistic antiviral activity with enhanced efficacy and safety, offering a new strategy for the development of next-generation anti-influenza drugs.

Source: 

Link: https://pubs.acs.org/doi/10.1021/acs.jmedchem.5c03547

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