Cross-clade #protection against #human #H5N1 isolates by a clade 2.3.4.4b HA #mRNA #vaccine in mice

 

Abstract

The recent spread of clade 2.3.4.4b H5N1 high pathogenicity avian influenza (HPAI) viruses into mammals, despite limited human infections to date, has raised serious public health concerns and highlights the need for rapidly deployable vaccines, such as mRNA-based platforms, to strengthen pandemic preparedness. Here, we evaluated the effectiveness of an mRNA vaccine encoding the HA of NIID-002, a WHO-recommended H5 candidate vaccine virus (CVV) derived from A/Ezo red fox/Hokkaido/1/2022 (clade 2.3.4.4b) against A/Texas/37/2024 (TX37; clade 2.3.4.4b) and A/Cambodia/2311257/2023 (Cam23; clade 2.3.2.1e). The mRNA was formulated with ssPalmO, a low-inflammatory self-degradable ionizable lipid nanoparticle (LNP). BALB/c mice were immunized intramuscularly twice with the mRNA-LNP vaccine containing either 1 μg or 10 μg of H5 HA mRNA. After boosting, strong, dose-dependent serum IgG responses against NIID-002 HA were detected by ELISA. The mice were then challenged with a lethal dose of homologous TX37 or heterologous Cam23. All mice in the 10-μg group survived both challenges, demonstrating robust cross-clade protection. In the 1-μg group, complete protection without significant body weight loss was observed against TX37, whereas partial protection was observed following Cam23 challenge. Viral titers were significantly reduced in multiple tissues of the vaccinated mice compared to the unvaccinated controls. Our findings demonstrate that the NIID-002-HA mRNA vaccine confers protection against homologous and heterologous zoonotic H5N1 strains in a mouse model. This low-inflammatory ssPalmO-LNP platform thus supports safe, rapid vaccine development against emerging H5N1 viruses with pandemic potential.

Source: 

Link: https://doi.org/10.1016/j.vaccine.2026.129215

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N70S/Y155H Combined #Mutation of #Neuraminidase of Avian #Influenza #H9N2 Virus confers #oseltamivir and #zanamivir #resistance and pathogenicity to Mice

 

Highlights

    • H9N2 viruses recently circulating in China harbors novel N70S/Y155H dual mutations in N2;

    • H9N2 viruses with N70S/Y155H mutations exhibit high pathogenicity to BALB/c mice.

    • N70S/Y155H linked mutations in N2 confer resistance to oseltamivir and zanamivir, rather than peramivir.

    • Neuraminidase inhibitors exhibited limited efficacy on H9N2 virus with novel N70S /Y155H dual mutations.

Abstract

Recently, H9N2 avian influenza virus (AIV) poses a significant threat to both the poultry industry and public health. Therefore, investigating the impact of its neuraminidase mutations on susceptibility to neuraminidase inhibitors (NAIs) is of great importance for clinically preventing potential cross-species transmission of H9N2. In this study, our results revealed that NAI resistance-related mutations of most H9N2 viruses isolated from China during 1998 to 2024 mainly occurred at positions N70S, E119A/D/G/V, Q133K, Q136A, D151E, Y155H, I222V, R224K, E276D, R292K, N294S, and R371K. Among them, the combined N70S and Y155H mutations are common characteristics of H9N2 viruses circulating in recent years. In vivo experiments demonstrated that these H9N2 viruses harboring the combined N70S and Y155H mutations exhibit high pathogenicity to BALB/c mice without prior adaption. In vitro neuraminidase inhibition assays confirmed that these H9N2 viruses bearing the N70S/Y155H mutations exhibited greater reduced inhibition than their counterparts bearing the N70S or Y155H single mutation to oseltamivir and zanamivir, but remained highly sensitive to peramivir. Notably, the in vivo protective effect of NAIs against H9N2 virus with combined N70S and Y155H mutations is limited, possibly due to the restricted ability of these drugs to ameliorate the excessive inflammatory responses. Therefore, there is an urgency to strengthen research on epidemiological surveillance and prevention strategies for avian influenza H9N2 harboring these mutations.

Source: 

Link: https://doi.org/10.1016/j.antiviral.2026.106540

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Comparison of #Baloxavir-Based Combinations and Monotherapies for Treating #Influenza #H5N1 Clade 2.3.4.4b Virus #Infection in Mice

 

Abstract

Highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus continues to cause animal outbreaks and sporadic zoonotic infections. In a mouse model of lethal influenza disease, we compared oseltamivir, baloxavir, and molnupiravir monotherapies with 2-drug combinations. Baloxavir-based combinations improved survival, reduced lung viral loads, and prevented extrapulmonary dissemination, supporting H5N1 preparedness strategies.

Source: 

Link: https://doi.org/10.3201/eid3210.260186

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A single-cycle, recombinant VSV #platform #Nipah #vaccine cross-protects against #Hendra virus in nonhuman #primates

 

Abstract

Nipah virus (NiV) and Hendra virus (HeV) are highly pathogenic paramyxoviruses that produce severe, often fatal disease in humans and animals. Zoonotic spillover of these henipaviruses from the Pteropid bat natural reservoir occurs near-annually in Southeast Asia and Oceania. Outbreaks of NiV disease frequently exceed case fatality rates of 75%, and person-to-person transmission makes controlling outbreaks in low-resource environments challenging. HeV is less transmissible between humans; however, the overall mortality rate is 57%. Approaches to human vaccine development have largely focused on NiV given the larger case burden, and immunogen selection has centered on display of the NiV attachment (G) or fusion (F) surface glycoproteins. However, experimental vaccines displaying these NiV antigens have failed to uniformly cross-protect against HeV disease in preclinical models. The HeV (G) antigen was shown to cross-protect against both HeV and NiV when delivered in a protein subunit form; however, attempts to utilize mRNA or canarypox vectors failed to achieve equivalent protection. We previously developed and evaluated a single-cycle recombinant vesicular stomatitis virus-vectored vaccine displaying the (G) glycoprotein of Nipah virus strain Bangladesh (NiV-B). This experimental vaccine (G*rVSV∆G-NiV-G) demonstrated ideal characteristics of rapid and durable protection against NiV-B challenge in nonhuman primates. In the present work, we show that the G*rVSV∆G-NiV-G vaccine cross-protects against lethal HeV challenge, with the protective response driven by a balance of both cell-mediated and humoral compartments.

Source: 

Link: https://doi.org/10.1371/journal.ppat.1014646

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#Oropouche virus disrupts #neurodevelopment and exhibits #congenital infection potential

 

Abstract

Oropouche virus (OROV) historically caused a self-limiting disease, yet recent strains have been clinically linked to congenital infection and neurodevelopmental disease. These observations highlight the need to study OROV as a congenital pathogen. Here, using both a historical and currently circulating strain, we show OROV infects neurons across differentiation states in human forebrain organoids. Compared with the neurotropic congenital pathogen Zika virus (ZIKV), OROV exhibits a heightened capacity for neuroinfection and pathology in both forebrain organoids and neonatal mice. The increased permissiveness of OROV is driven, in part, by a broader neuronal tropism and a relative insensitivity to neuronal type I interferon-mediated antiviral responses. Consistent with clinical observations, neonatal neuroinfection results in rapid and severe neuropathology marked by cerebral hemorrhage. Finally, using a transient type I interferon-blockade model, we demonstrate that OROV can productively infect the murine placenta and cause fetal growth restriction. Together, our complementary models support a unified framework in which placental and fetal barriers limit productive fetal brain infection, yet OROV exhibits marked neurotropism and neuropathogenic potential upon gaining access to developing neural tissues. These findings reinforce the need for vigilant monitoring of OROV as an emerging pathogen associated with adverse pregnancy outcomes and congenital disease.

Source: 

Link: https://doi.org/10.1038/s41467-026-77859-5

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Limited added #benefit of seasonal #influenza #vaccination before #H5 vaccination in mice and #ferrets challenged with #H5N1

 

ABSTRACT

Limited A(H5)-specific vaccine supply is expected early in a potential A(H5N1) pandemic, raising the question of whether licensed seasonal influenza vaccines could enhance protection when administered before A(H5) vaccination. We evaluated this strategy in mouse and ferret models using clade 2.3.4.4b A(H5N1) viruses. Seasonal influenza vaccination induced antibodies to seasonal haemagglutinins but did not induce detectable antibodies against A(H5) and did not consistently enhance A(H5)-directed antibody responses after A(H5) vaccination. In lethal challenge studies, seasonal vaccine priming before A(H5) vaccination was associated with improved outcomes compared with A(H5) vaccination alone in one of three mouse experiments, but this effect was not observed in the other two mouse experiments or in ferrets. These findings suggest that seasonal influenza vaccine priming provides limited added benefit to A(H5) vaccine-mediated protection against A(H5N1) under the conditions tested.

Source: 

Link: https://doi.org/10.1080/22221751.2026.2731495

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#Pathogenesis and natural history of the #Bundibugyo species of #Orthoebolavirus in nonhuman #primates

 

Abstract

The current outbreak of Bundibugyo virus (BDBV) in Africa is a global public health concern particularly as there are no licensed medical countermeasures (MCM). Well characterized animal models that accurately replicate human BDBV infection are needed to develop effective MCM. We exposed 21 cynomolgus monkeys (CM) to BDBV to examine the progression and natural history of BDBV disease (BVD). BVD was more protracted than reported for Ebola and Sudan infection in CM with a lower lethality rate of 67% consistent with lower human BVD mortality rates. IHC and spatial proteomics identified CD209+, CD68+, and/or HLA-DR+ macrophages and dendritic cells as early targets of BDBV. These infected cells frequently colocalized with fibrin and infiltrating MPO+ neutrophils and S100A9+ myeloid-derived suppressor cells, consistent with the development of an active inflammatory response and early coagulopathy. Transcriptomic and proteomic analyses of the circulating immune response correspondingly reflected a cytokine-driven hyperinflammatory state in CM that succumbed to disease. Surviving animals resolved systemic inflammation by the study endpoint; however, BDBV antigen was identified in immune privileged tissues with lesion-associated inflammation aligning with known post-Ebola sequela in humans. This data should assist in identifying weaknesses in the disease course that can be exploited to develop new MCM.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

National Institute of Allergy and Infectious Diseases, https://ror.org/043z4tv69, U19AI109945

The University of Texas Medical Branch at Galveston, https://ror.org/016tfm930, N/A

Source: 

Link: https://doi.org/10.64898/2026.08.10.743937

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Updated #H1N1pdm09 #influenza virus #ferret infection #model permits refined #antiviral #assessment using aerosol inhalation challenge

 

Abstract

Seasonal influenza viruses continue to pose a significant threat to human health. As influenza viruses exhibit sustained genetic drift, it is imperative that animal studies utilize challenge strains that reflect contemporary, currently circulating viruses when evaluating pathogenicity, viral tropism, transmissibility, and antiviral sensitivity to better inform public health responses. Ferrets are considered the gold-standard small animal model for assessing currently circulating influenza viruses. Seasonal influenza A(H1N1)pdm09 viruses replicate well in both the upper and lower respiratory tract of ferrets, providing an important model for developing improved vaccination and therapeutic strategies; however, many of these studies have relied on a 2009 virus isolate. Utilising representative influenza A(H1N1)pdm09 virus strains from 2009 to 2022, we explored virus replication kinetics and lung pathogenesis in ferrets following intranasal inoculation with these contemporary strains. Our results revealed strain specific differences, with greater lung viral loads and pathogenesis following inoculation with A/Sydney/5/2021 compared to other strains. Efficient transmissibility of A/Sydney/5/2021 virus to naïve recipients was also observed following both contact and airborne exposure to infected donor ferrets. To refine this updated model, we performed side-by-side evaluation of oseltamivir antiviral efficacy following traditional intranasal or aerosol inhalation influenza challenges. Pre-treatment with oseltamivir demonstrated greater reductions in viral shedding from the upper respiratory tract than post-infection treatment of ferrets infected by aerosol inhalation, while the intranasal route showed reduced oseltamivir efficacy independent of the timing of antiviral treatment. These findings provide the basis for using an updated A(H1N1)pdm09 challenge virus for ferret studies as an alternative to the commonly used, but now less relevant 2009 early pandemic viruses. It also highlights how different methods of virus inoculation can influence outcomes of ferret antiviral studies, with an aerosol challenge model able to demonstrate differences between therapeutic and prophylactic treatments, which were not apparent with an intranasal challenge model.

Source: 

Link: https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014604

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Pan - #Ebolavirus nanoparticle #vaccine provides protection in rodents from lethal #infection by #Zaire and #Sudan viruses

 

Abstract

Both Zaire ebolavirus (EBOV) and Sudan ebolavirus (SUDV) are members of the genus Ebolavirus and cause outbreaks marked by high fatality rates and repeated spillover from animal reservoirs. Filoviral glycoproteins (GPs) are the primary targets of neutralizing antibodies and form the basis of current vaccines. Here we describe the design, structural characterization, and evaluation of two-component self-assembling icosahedral I53-50 nanoparticles displaying prefusion EBOV or SUDV GP antigens, either individually or in cocktail and mosaic multivalent formats. EBOV-GP-I53-50 and SUDV-GP-I53-50 nanoparticles elicited strong homologous protection in mice and guinea pigs. In the mouse-adapted EBOV model (maEBOV), mosaic and cocktail formulations produced weak survival below that of the matched EBOV-GP-I53-50 GP immunogen. In contrast, in the gpaSUDV guinea pig model (gpSUDV), cocktail and mosaic nanoparticles elicited robust protection against gpSUDV, and detectable antibody responses to both SUDV and EBOV GPs. These findings demonstrate that multivalent GP-I53-50 nanoparticle immunogens can protect rodents from death, severe clinical signs of disease, and weight loss in relevant models. Together with the established clinical safety of the I53-50 platform, these results support continued efforts toward the development of a pan-ebolavirus vaccine.

Source: 

Link: https://www.nature.com/articles/s41467-026-76114-1

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Elicitation of Potent #H5N1 - and #H7N9-Neutralizing #Antibody Responses in Rh. Macaques by Sequential Heterologous #Vaccination with #mRNA and Adenoviral Vectors Encoding Full-Length Hemagglutinins

 

Abstract

Highly pathogenic avian influenza (HPAI) represents an enormous pandemic risk amid the ongoing H5N1 panzootic. HPAI, defined by its high lethality in domestic poultry, includes the influenza A virus (IAV) H5N1 and H7N9 subtypes and has a 40–50% case fatality rate in humans. To facilitate the development of efficacious HPAI vaccination regimens and isolation of HPAI-neutralizing monoclonal antibodies (nmAbs) for prophylactic and therapeutic use, we performed a proof-of-concept pilot study wherein we developed an array of mRNA and adenovirus-vectored vaccines encoding HPAI hemagglutinins (HAs) and then assessed their immunogenicity in IAV-naïve Indian rhesus macaques (RMs). All RMs developed binding IgG recognizing both HPAI HAs. HPAI-nAbs were detected in RMs vaccinated with full-length HAs, but not in RMs vaccinated with HA stems alone. Potent HPAI neutralization activity was observed in two animals with serum ID50 titers of ~1:100,000 against H5N1 and ~1:50,000 against H7N9. Most RMs developed cross-reactive IgG recognizing the HAs of additional IAV subtypes, and HA-specific B cells were readily identifiable in vaccinee PBMCs by flow cytometric analysis. The results of our pilot study suggest that elicitation of potent HPAI-nAb responses is enhanced by vaccination with the HA head domain and that vaccination with the HA stem alone tends to elicit binding non-nAbs. Furthermore, use of our fluorophore-conjugated HA probes to identify HA-specific B cells could enable HPAI-nmAb isolation. Collectively, our findings could facilitate the development of novel vaccines and nmAb therapeutics leveraging the superior neutralization potency of HA head-specific Abs to prevent and treat HPAI infections in humans.

Source: 

Link: https://www.mdpi.com/1999-4915/18/9/981

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#Safety, humoral and cellular immune responses to a pre-pandemic adjuvanted #influenza #H5N8 #vaccine

 

Abstract

Highly pathogenic avian influenza (HPAI) A(H5) viruses can be transmitted from infected birds to various mammalian species, including humans. Avian influenza viruses (AIVs), members of the Orthomyxoviridae family, possess segmented RNA genomes prone to reassortment, favoring the emergence of novel genetic traits that may alter transmissibility, pathogenicity, and antigenicity. Although no sustained human-to-human transmission has been reported, the potential adaptation of these viruses poses a significant pandemic threat. This study aimed to evaluate the non-clinical safety, toxicity, and humoral immune responses induced by an adjuvanted H5 influenza vaccine in rats and rabbits, to support future clinical safety trials in humans. Male and female Wistar rats and New Zealand rabbits were observed for 14, 28, and 90 days after receiving two intramuscular doses of the H5N8 vaccine (15 μg HA/dose) formulated with the IB160 oil-in-water emulsion adjuvant. No systemic comorbidities, central nervous system alterations, or relevant clinical signs were observed. Hematological parameters remained within normal ranges, with total and differential leukocyte counts showing only minor fluctuations (<1% of total leukocytes). Mild biochemical variations in urea and hepatic transaminase levels were not correlated with histopathological alterations. The vaccine elicited a robust humoral response soon after immunization, with all groups reaching protective HAI-antibody titers. Although antibody levels declined over time, particularly in males, they remained significantly above baseline, indicating durable immunological memory. Furthermore, the vaccine induced a specific cellular immune response, confirmed by IL-2 and TNF production by antigen-specific T lymphocytes in splenic cell cultures after the booster dose. In conclusion, the H5N8 vaccine with the IB160 adjuvant was well tolerated locally and systemically, without compromising vital organ function. The safety and immunogenicity findings are consistent with expectations for adjuvanted influenza vaccines, demonstrating strong and durable humoral and cellular immune responses.

Source: 

Link: https://www.sciencedirect.com/science/article/abs/pii/S0264410X26008583?via%3Dihub

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Sex differences in #vaccine-induced #neuraminidase cross-recognition impact #H5N1 #dissemination to the lower respiratory tract in mice

 

Abstract

H5N1 vaccines have been poorly immunogenic in humans, creating a challenge for vaccine development. Seasonal influenza vaccines offer some cross-protection against H5N1, but there has been no consideration of whether protection differs between the sexes. We investigated sex differences in antibody responses following receipt of either beta-propiolactone inactivated whole virus H1N1 or H5N1 (LAIV backbone) vaccines in C57BL/6 mice. Using systems serology assays, vaccination induced strong homologous and heterologous antibody responses, with females generating greater IgG titers than males against whole virus H1N1 and H5N1, which was primarily mediated by greater IgG responses to neuraminidase (NA) than hemagglutinin (HA) protein. Cross-reactive H5N1 IgG titers were greater among H1N1-vaccinated females, and primarily mediated by greater N1-specific IgG titers. IgG2b and IgG2c were the primary antibody isotypes generated in response to these vaccines, with females having greater IgG2b titers and enhanced binding to FcγRIV for avian and human NA than males following either homologous or heterologous vaccination. Antibody-dependent complement deposition was measured as an FcR-mediated non-neutralizing response against HA and NA and was more robust among H1N1 and H5N1 vaccinated females than their male counterparts in response to homologous HA only. Vaccinated females tended to have greater neutralizing antibody titers than males against the homologous vaccine strain, with limited cross-neutralizing antibodies detected in either sexes. Neuraminidase inhibition titers were greater in vaccinated females than males against the heterologous virus following H1N1 vaccination and against both the vaccine and heterologous viruses following H5N1 vaccination. When H1N1 and H5N1 vaccinated mice were challenged with a lethal dose of A/Texas/37/2024 H5N1, all H5N1 vaccinated mice were protected, regardless of sex. Among H1N1 vaccinated mice, while both sexes were protected against disease, H1N1 vaccinated females restricted virus to the upper respiratory tract and had lower pulmonary virus titers than males at 3 days post challenge. These findings highlight that sex differences in vaccine-induced NA-specific antibody responses are associated with differential respiratory dissemination of H5N1 and that sex should be considered in studies of vaccine-induced cross-reactive influenza immunity.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

NIH/NIAID Johns Hopkins Center of Excellence for Influenza Research and Response, 75N93021C00045

Richard Eliasberg Family Foundation

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.05.26.728011v3

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Immunogen selection and prior #immunity shape #antibody breadth following immunisation with avian #H5 #hemagglutinin

 

Abstract

Avian influenza A viruses pose a persistent zoonotic threat to humans owing to their expanding host range and high case fatality rates. In particular, viruses from the 2.3.4.4b clade of the H5 subtype have now been detected in over 60 mammalian species, raising serious pandemic concerns. Understanding immune recognition of the H5 hemagglutinin (HA) is therefore critical for effective vaccine design and pandemic preparedness. To understand the breadth of cross-recognition induced by different H5 strains, we selected genetically diverse H5 human isolates from 2003-2023 and assessed neutralising antibody responses elicited by adjuvanted recombinant HA protein-based vaccines in C57BL/6 mice. Neutralisation activity of sera was determined against seven H5 HA variants using pseudotyped viruses and a PR8-reassortant virus in micro-neutralisation assays. Our results showed a wide variety of cross-strain neutralisation across H5 HA antigen variants. The conventional vaccine strain A/Indonesia/05/2005 displayed narrow activity against emerging clade 2.3.4.4b viruses, whereas ancestral variants exhibited cross-neutralisation profiles showing a diversity of breath but with limited potency. Polyvalent H5 HA formulations and nanoparticle-displayed H5 HA platforms substantially broadened cross-neutralisation against diverse H5 strains. To examine the impact of pre-existing immunity on H5 vaccine immunogenicity in mouse models, mice were primed with either seasonal influenza infection or quadrivalent influenza vaccine (QIV) prior to H5 HA immunisation. QIV pre-vaccination, but not prior influenza infection, enhanced subsequent neutralizing responses towards A/Fujian-Sanyuan/21099/2017 (clade 2.3.4.4b) H5. Collectively, our results demonstrate that immunogen selection and prior immunity shape antibody breadth following immunisation with avian A(H5) hemagglutinin.

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.09.01.748495v1

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Isolation and characterisation of #Nipah virus neutralising candidate therapeutic monoclonal #antibodies from an #mRNA-immunised pig

 

Abstract

Nipah virus (NiV) is a highly pathogenic zoonotic paramyxovirus with epidemic potential. Despite the threat NiV poses, no therapeutics are licensed to treat infection. Studies have shown that monoclonal antibodies (mAb) can protect animals against NiV and the related Hendra virus (HeV). The best studied mAb, m102.4, has been used to treat infected patients on a compassionate basis, and has entered clinical trials. However, there is a need to define additional mAbs with therapeutic potential, which could be combined with m102.4 to improve neutralising potency and breadth. Here, we isolated five high affinity mAbs from an mRNA immunised pig, which bound the G glycoprotein derived from NiV Malaysia strain (NiV-M), and one of which (mAb A2) also bound HeV G. Aligned with this, all mAbs neutralised NiV-M pseudovirus but only mAb A2 neutralised pseudovirus representing the NiV Bangladesh (NiV-B) strain. mAb A2 and the most potent NiV-M neutralising mAb, C1, showed minimal competition with each other and m102.4, suggesting recognition of non-overlapping epitopes. Single-particle cryogenic electron microscopy of the NiV-M G receptor binding domain complexed to A1 and C2 Fab fragments revealed distinct epitopes that did not overlap with the receptor-binding site, targeted by m102.4, suggesting action through steric impedance of receptor binding or interference downstream of receptor engagement. Inoculation of mAb A2 to hamsters did not provide complete protection against NiV-B challenge (60% survival), however, a split dose of mAb A2 and m102.4 provided the same protection as m102.4 alone (100% survival). Collectively, these data demonstrate the potential of the porcine model for isolation of therapeutic candidate mAbs, which contribute both to our understanding of the NiV G antigenic landscape, and the development of mAb combinations, that exert complementary mechanisms of neutralisation, for therapeutic intervention.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

European Commission, https://ror.org/00k4n6c32, VetBioNet, EMJMD LIVE

Innovate UK, 971555

UK Research and Innovation, BBS/E/I/00007031, BBS/E/I/00007037, BBS/E/I/00007038, BBS/E/I/00007039, MR/S007555/1, BB/T008784/1

Wellcome Trust, 203141/Z/16/Z

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.08.28.745669v1?rss=1

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Impaired #Neuraminidase and Polymerase Activities Correspond With Limited Aerosol Infectivity of #B3.13 and #D1.1 #H5N1 Lineages in #Human Respiratory Cultures

 

Abstract

The ongoing panzootic of clade 2.3.4.4b highly pathogenic avian influenza (HPAI) H5N1 viruses has reached a critical point, marked by unprecedented mammalian spillover and sustained outbreaks in U.S. dairy cattle. While these viruses remain highly lethal in traditional ferret models, human infections-primarily linked to the B3.13 and D1.1 lineages-have been notably mild, typically presenting as conjunctivitis with minimal respiratory involvement. In this study, we address this disconnect by evaluating the infectivity of recent H5N1 isolates using a physiologically relevant air-liquid interface (ALI) culture system that incorporates an aerosol settling chamber. We demonstrate that while direct liquid inoculation leads to efficient replication, aerosolized H5N1 strains exhibit a significant defect in their ability to infect human respiratory epithelium. In contrast, a prototypic H5N1 virus remains highly pathogenic and lethal in ferrets regardless of the inoculation route, showing systemic dissemination to the brain and other organs. Our findings identify two primary viral determinants driving this respiratory restriction: reduced neuraminidase (NA) enzymatic activity and impaired polymerase activity. Collectively, these results suggest that commonly used mammalian models may overstate current human pandemic risk. This work highlights the critical need for alternative risk-assessment platforms to identify the specific genetic shifts required for these viruses to overcome existing barriers to human adaptation.

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.08.18.745466v1

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Characterisation of a #human monoclonal #antibody targeting a conserved epitope at the base of the HA head of #influenza #H3N2 virus

 

Summary

Background

Numerous broadly reactive human monoclonal antibodies (mAbs) against the haemagglutinin (HA) of influenza A viruses have recognised conserved epitopes across HA subtypes or within subtypes. Most heterosubtypic mAbs target the HA stem, the receptor-binding site (RBS), or the trimeric interface. Although at least three H3-specific mAbs recognise epitopes outside these regions, the overall landscape of conserved H3-specific epitopes remains incompletely understood. This study aimed to identify and characterise conserved epitopes on H3-HA to inform the development of vaccines resilient to antigenic change.

Methods

We screened a panel of previously reported H3-HA-reactive human mAbs to identify mAbs recognising conserved epitopes. The candidate clone, 034-10040 4F02 (4F02), was evaluated for neutralising, haemagglutination inhibiting, and HA-mediated fusion-inhibitory, Fc receptor-mediated effector functions in vitro, and for protective efficacy in a lethal mouse challenge model. Cryo-electron microscopy was used to define the structural basis of 4F02 binding. Human sera were screened for antibodies targeting similar epitopes.

Findings

Clone 4F02 recognised the HA of human influenza A (H3N2) viruses that circulated across multiple decades. It neutralised multiple H3N2 viruses, exhibited weak haemagglutination inhibition, blocked HA-mediated fusion activity, activated Fc receptor-mediated signalling, and protected mice against lethal challenge. Cryo-electron microscopy revealed that 4F02 targets the base of the HA head at a head-stem interface spanning antigenic sites C, D, and E. Antibodies targeting similar epitopes were detected, albeit at a low level, in human sera.

Interpretation

Characterisation of the 4F02 epitope reveals a previously underappreciated site of vulnerability at the H3-HA head-stem interface. This finding expands our understanding of conserved epitopes and provides a target for the development of influenza vaccines resilient to antigenic change.

Funding

This work was supported by the Japan Agency for Medical Research and Development, JSPS KAKENHI, the National Institutes of Allergy and Infectious Diseases.

Source: 

Link: https://www.thelancet.com/journals/ebiom/article/PIIS2352-3964(26)00334-8/fulltext

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A mouse #monoclonal #antibody against #H7N9 #influenza virus cross-react with #human #platelets

 

Highlights

    • H7N9–98 mAb specifically binds human platelets and targets a ~60 kDa platelet protein.

    • H7N9 virus induces ITP via molecular mimicry with platelet antigens.

    • H7N9 virus-related ITP correlates with disease severity.

Abstract

Objective

To investigate the association and potential mechanisms between H7N9 influenza virus infection or vaccination and immune thrombocytopenia (ITP), providing foundational data for the prevention and treatment of related ITP.

Methods

Using laboratory-prepared anti-H7N9 influenza virus monoclonal antibodies (mAbs) (H7N9-98 and H7N9-120) as research subjects, the interactions between these antibodies and human platelets were analyzed through Western blotting (WB), immunohistochemistry (IHC), and immunofluorescence (IF) techniques.

Results

The mAb H7N9-98 exhibited specific binding to human platelets, showing positive results in both IHC and IF assays. Western blotting results demonstrated that this antibody could specifically recognize approximately 60 kDa human platelet proteins. The isotype control mAb H7N9-120 did not exhibit the aforementioned binding reactions, with all test results being negative.

Conclusion

These findings suggest that the specific antibodies induced by the H7N9 virus may mediate platelet damage through cross-reactivity with platelet autoantigens. This mechanism warrants further investigation to provide experimental evidence for the pathogenesis of secondary ITP associated with H7N9 infection.

Source: 

Link: https://www.sciencedirect.com/science/article/pii/S1567134826001346?via%3Dihub

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Trimester-dependent vertical #transmission of #H5N1 #influenza virus through #placental and mammary routes impairs offspring development

 

Abstract

Avian influenza H5N1 has pandemic potential and historically causes more severe disease in pregnant women than the general population. With increasing transmission of H5N1 detected among placental mammals, animal models are necessary for testing countermeasures, including during pregnancy. Pregnant outbred mice infected with a contemporary strain of bovine H5N1 during the second trimester equivalent causes in utero transmission, with infectious virus detected in the uterus, placenta, and fetus. Birth following third trimester infection results in offspring with decreased size, neurodevelopmental delays, and adolescent behavioral impairments, with infectious virus detected in the neonatal milk ring and lungs, as well as mammary tissues. H5N1 viral protein colocalizes with trophoblast cells in the placenta and epithelial cells in mammary tissue that spatially overlap with lectins for α2,3-linked SA. With the pandemic potential of H5N1, our vertical transmission model in placental mammals is essential for understanding viral spread and evaluating treatments during pregnancy.

Source: 

Link: https://www.nature.com/articles/s41467-026-76891-9

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#Nipah virus #Malaysia and #Bangladesh strain-induced #pathogenesis in mice lacking type I #interferon receptor signaling

 

Abstract

Nipah virus (NiV) is a zoonotic highly pathogenic Paramyxovirus inducing lethal outbreaks of encephalitis and Acute Respiratory Distress Syndrome (ARDS) with an average case-fatality rate of 75%. Two viral strains, NiV-Malaysia (NiV-Mal) and NiV-Bangladesh (NiV-Ban), associated to distinct route of transmission, symptoms and lethality have been described. Due to the permanent threat of these emerging infections and the lack of approved therapeutics, it is crucial to improve our understanding regarding NiV-associated pathogenesis. Mice represent a small and accessible animal model, provided with numerous biological tools for the functional assessment of different genes related to antiviral response. Here, we explore the susceptibility of mice deficient for type I interferon receptor (IFNAR KO) to inoculation with either NiV-Mal or NiV-Ban through intraperitoneal or intranasal routes. Our results complement observations showing that IFNAR KO mice are susceptible to NiV-Ban infection via intraperitoneal route, although to a lesser extent than NiV-Mal, and develop encephalitis and a pulmonary syndrome with viral dissemination to various organs. Additionally, intranasal administration of both viral strains exhibited a subclinical infection with viral replication in the brain and the lungs along to the production of neutralizing antibodies in some animals. These results suggest that IFNAR KO mice may represent a reliable model permitting comparative studies of the immunopathogenesis induced by both NiV-Mal and NiV-Ban infections.

Source: 

Link: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0013894

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A novel candidate #vaccine virus derived from #Japan's first #mammalian case of clade 2.3.4.4b #H5N1 highly pathogenic avian #influenza virus

 

Abstract

The development of candidate vaccine viruses (CVVs) for pre-pandemic preparedness requires attenuation of pathogenicity while maintaining immunogenicity. In this study, we developed and characterized NIID-002, a reassortant virus derived from A/Ezo red fox/Hokkaido/1/2022 (H5N1; clade 2.3.4.4b), to evaluate its suitability as a candidate vaccine. NIID-002 exhibited markedly reduced pathogenicity compared with its parental strain, while retaining broad antigenic reactivity and protein yield comparable to other clade 2.3.4.4b CVVs. In mammalian models, NIID-002 demonstrated strong attenuation, causing no lethal infection in mice and only minimal weight loss with limited viral replication in ferrets. Antisera raised against NIID-002 reacted broadly with recent wild-type H5N1 isolates, suggesting potential broad protection. Protein yield analysis confirmed a production efficiency comparable to that of other CVVs within the same clade, supporting its feasibility for large-scale vaccine manufacturing. Overall, NIID-002 fulfills the key requirements for the pandemic preparedness of CVV, combining reduced pathogenicity, broad antigenic reactivity, and adequate production efficiency. These findings highlight its potential as a candidate H5N1 vaccine and underscore the continued need for surveillance and refinement of influenza vaccine strategies to address evolving viral threats.

Source: 

Link: https://www.sciencedirect.com/science/article/abs/pii/S0264410X26008571?via%3Dihub

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