Elicitation of #stem-directed #antibodies in rhesus #macaques by a conventional #hemagglutinin immunogen

 

Abstract

Because they can bind many strains of influenza, antibodies targeting the hemagglutinin (HA) stem have been attractive targets for vaccine development. Many monoclonal antibodies (mAbs) directed at the HA stem have been isolated from humans, and these mAbs have mediated broad protection in animal models. We describe here HA stem-directed mAbs isolated from rhesus macaques immunized with an "ordinary" H1 HA trimer. All immunized rhesus macaques developed high serum titers with broad reactivity to diverse H1N1 and H5N1 viruses, and 7 isolated mAbs strongly blocked canonical stem antibody CR6261 binding to H1. MAb DH726.1 robustly protected mice from lethal challenge with H1N1 and H5N1 viruses, and cryo-EM showed the binding footprint overlapped that of some human mAbs. These findings suggest that vaccination with the standard, trimeric HA immunogens may be sufficient to elicit stem antibodies at titers adequate to protect against zoonotic H5N1 influenza.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

NIH NIAID, Division of Microbiology and Infectious Diseases, P01-AI089618

NIH NIAID Division of AIDS, Center for HIV/AIDS Vaccine Immunology, U19-AI067854

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.07.16.738984v1

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Immunoinformatics-Guided Design and In Silico Evaluation of a Multi-Epitope #Vaccine Against #Influenza A #H10N5 and #H3N2 Strains Based on HA and NA Proteins

 

Abstract

Influenza A viruses H3N2 and H10N5 represent, respectively, a persistently dominant seasonal pathogen and a newly documented zoonotic threat with the latter strain variants responsible for the first confirmed human fatality in January 2024, yet no vaccine platform currently addresses co-protection against both subtypes within a unified immunogen. We report here the immunoinformatics based vaccine design and multi-layered computational validation of a 419-amino-acid multi-epitope subunit vaccine construct targeting conserved hemagglutinin (HA) and neuraminidase (NA) antigens identified through multiple sequence alignment of the avian H10N5 (A/swine/Hubei/10/2008) and H3N2 human reference strain sequences to identify viral agents undergoing mammalian adaptations. Linear B-cell, cytotoxic T lymphocyte (CTL), and helper T lymphocyte (HTL) epitopes were predicted using ABCpred, BCEpred, BepiPred 2.0, NetMHCpan 2.1, and NetMHCpan 4.0, then filtered through VaxiJen 3.0, AllerTOP v2.1, and ToxinPred to retain only antigenic, non-allergenic, non-toxic candidates. The final construct, incorporating an avian β-defensin N-terminal adjuvant with GPGPG, AAY, and EAAAK linkers, exhibited a molecular weight of 43.9 kDa, instability index of 31.15, and SOLPro solubility probability of 0.763. Tertiary structure modeling via I-TASSER and GalaxyRefine achieved 84.4% Ramachandran-favored residues. Molecular docking against TLR3 and TLR7 yielded binding free energies of −16.1 and −16.8 kcal/mol with picomolar dissociation constants. Molecular dynamics simulations confirmed complex stability over extended trajectories. Furthermore, codon optimization produced a Codon Adaptation Index of 1.0 for E. coli K12 expression. In silico immune simulation demonstrated robust activation of humoral and cellular immunity including elevated IgG1, IgM, IFN-γ, IL-2, rapid NK cell expansion, and broad B-cell clonal diversity. These findings establish a computationally validated candidate capable of providing protection against influenza in multiple host organisms, warranting experimental advancement.

Competing Interest Statement

The authors have declared no competing interest.

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.07.03.736294v1

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Preclinical #immunogenicity of the #LP81-adapted BNT162b2 #COVID19 #vaccine

 

Abstract

SARS-CoV-2 evolution toward antigenically distinct lineages drives escape from host immunity. JN.1 lineage derivatives have recently dominated the global epidemiologic landscape. In preclinical models, an LP.8.1-adapted BNT162b2 vaccine elicited higher serum neutralizing antibody responses against contemporary, circulating JN.1 sublineages, including the epidemiologically dominant XFG lineage, as compared to JN.1 and KP.2 vaccines. These findings supported the selection of an LP.8.1-adapted vaccine for the composition of the 2025-26 COVID-19 vaccine formula.

Source: 

Link: https://www.nature.com/articles/s41541-026-01515-8

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#Sialic acid-anchored #haemagglutinin stalk neutralizing #antibody M-SiaB enhances #protection against highly pathogenic #influenza #H5N1/Texas/2024

 

Abstract

The recently emerged cattle H5N1/Texas/2024 strain highlights the need for effective prophylactic and therapeutic drug interventions, yet most existing neutralizing antibodies (NAbs) have limited efficacy against genetically divergent pathogenic influenza viruses. Here we engineer a sialic acid-anchored tandem M-SiaB by fusing a hemagglutinin (HA) stalk-specific monoclonal NAb with a sialic acid-receptor-binding domain (SiaB). M-SiaB shows 4- to 20-fold greater neutralizing potency against diverse authentic influenza viruses compared to the parental NAb and suppresses multiple stages of the viral life cycle, including viral attachment, entry and release. Importantly, intranasal M-SiaB confers markedly enhanced protection against nasal challenges with the pathogenic H1N1/PR8 and H5N1/Texas/2024 strains. Notably, a single dose of M‑SiaB maintains survival after a highly lethal H5N1/Texas/2024 challenge for up to 21 days. These findings demonstrate that simultaneously targeting HA stalk and sialic acid-receptor is a promising strategy to enhance the potency and breadth of NAbs against genetically divergent pathogenic influenza viruses.

Source: Nature Communications, https://www.nature.com/ncomms/

Link: https://www.nature.com/articles/s41467-026-74633-5

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Effectiveness of #baloxavir marboxil in nonhuman #primates infected with highly pathogenic avian #influenza #H7N9 virus

 

Summary

Background

Highly pathogenic avian influenza (HPAI) A(H7N9) virus poses a potential public health threat, underscoring the need for effective antiviral options for outbreak preparedness. Baloxavir marboxil (BXM) is a cap-dependent endonuclease inhibitor approved for seasonal influenza, but its in vivo efficacy against HPAI A(H7N9) virus has not been fully evaluated.

Methods

We evaluated the efficacy of BXM in cynomolgus macaques infected with a reverse genetics-generated HPAI A(H7N9) virus. Animals received either low- or high-dose BXM, single-dose oseltamivir, or vehicle at 4 or 48 h post-infection (hpi). BXM administration was designed to mimic human pharmacokinetics. Viral titres, body temperature, body weight, lung pathology, and treatment-emergent viral substitutions were analysed.

Findings

Early treatment (4 hpi) with BXM significantly reduced viral titres in nasal and tracheal swabs, lessened weight loss, and decreased pulmonary inflammation and alveolar damage compared to untreated or oseltamivir-treated animals. Virus pathogenicity was relatively mild; no animals died. Delayed treatment (48 hpi) showed limited benefit. The PA-I38T (83.8%) and PA-E23G (78.6%) substitutions associated with BXM resistance were detected in one animal, and a PA-K34R (85.4%) substitution was detected in another animal. These substitutions reduce BXM susceptibility and were detected at low titres.

Interpretation

Although the dosing regimen used in this study involved repeat dosing to achieve the plasma drug concentrations after a single dose in humans, these findings highlight the importance of early antiviral intervention and support BXM use as a potential countermeasure against HPAI A(H7N9) virus infection, as resistance-associated substitutions remained limited in the macaque model. BXM may be a valuable therapeutic option for HPAI A(H7N9) virus infections.

Funding

Supported by the Japan Agency for Medical Research and Development (JP20wm0125002, JP223fa627001) and Shionogi & Co., Ltd.

Source: 

Link: https://www.thelancet.com/journals/ebiom/article/PIIS2352-3964(26)00233-1/fulltext

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A #drug #repurposing screen identifies #antiviral compounds against #Puumala #Orthohantavirus

Abstract

Hantaviruses are zoonotic negative-sense RNA viruses that cause haemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS), yet no approved antiviral therapies are available. To identify host-directed modulators of hantavirus infection we performed a drug repurposing screen using live Puumala virus (PUUV). We identified and validated 70 drugs with antiviral activity in A549 cells and primary human endothelial cells. Functional clustering confirmed the known infection-inhibitory effect of several groups of compounds, including inhibitors of heat shock proteins, mTOR pathway and nucleotide synthesis. Our screen also identified compounds yet unexplored as antivirals against Hantaviruses, such as certain antibiotics. Our dataset provides a systematic map of host pathways influencing PUUV infection and highlights candidate compounds and cellular processes that can modulate this process.

Source: 

Link: https://www.nature.com/articles/s41598-026-57843-1

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#Antibodies Cross-Reactive with #Bundibugyo Virus in #Ferrets Vaccinated with #Ebola Virus #Vaccine

 

Abstract

Banked serum samples from ferrets previously immunized with the Ebola virus vaccine revealed a prominent but limited humoral immune response that cross-reacted with Bundibugyo virus. The supporting immunogenicity data we report may help guide the ongoing response to the current outbreak of Bundibugyo virus in the Democratic Republic of the Congo.

Source: Emerging Infectious Diseases Journal, https://wwwnc.cdc.gov/eid/

Link: https://wwwnc.cdc.gov/eid/article/32/8/26-0948_article

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Potent In Vitro #Antiviral Activity of 4'-Fluorouridine Against Diverse #Orthohantaviruses including #Andes Virus

 

Highlights:

    • 4′-fluorouridine exhibits broad-spectrum activity against 16 orthohantaviruses.

    • The compound inhibits hantavirus replication by targeting the viral polymerase.

    • Efficacy is maintained in human endothelial and airway epithelial cells.

Abstract

Hantaviruses are emerging pathogens responsible for severe and often fatal diseases, including hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS), for which no FDA-approved antivirals currently exist. Using a Seoul virus minigenome system, we first confirmed that the ribonucleoside analog 4’-fluorouridine (EIDD-2749) effectively targets the hantavirus polymerase complex, inhibiting viral RNA transcription and replication. We subsequently evaluated its antiviral activity against a comprehensive panel of 16 hantaviruses representing both Old and New World lineages including both the Chilean and Argentinian strains of Andes virus. 4’-fluorouridine demonstrated potent, dose-dependent inhibition across all viruses tested, with EC50 values uniformly in the low- to sub-micromolar range. Collectively, these findings establish 4’-fluorouridine as a highly potent, pan-hantavirus inhibitor and a promising candidate for further preclinical development.

Source: 

Link: https://www.sciencedirect.com/science/article/abs/pii/S0166354226001269?via%3Dihub

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A neutralizing #nanobody targeting a conserved lateral patch on HA1 confers #protection against multiple #H7 avian #influenza viruses

 

ABSTRACT

Human infections with H7 avian influenza viruses (AIVs) have been documented globally, involving multiple subtypes and geographic regions. However, effective therapeutics targeting H7 influenza viruses remain limited. Here, a panel of nanobodies targeting the HA1 domain of hemagglutinin (HA) was identified by yeast two-hybrid (Y2H) screening, and six candidates were subsequently validated to exhibit hemagglutination inhibition (HI) activity. Of these, a subset also displayed virus microneutralization (MN) activity, while all showed binding activity in ELISA assays. Among them, Nb74 exhibited inhibitory activity against four Chinese recombinant vaccine-matched strains (Rv1–Rv4), which were generated based on the HA sequences of the corresponding inactivated vaccine strains H7-Re1 to H7-Re4. The HI-IC50 values were 0.23, 0.57, 3.65, and 43.75 µg/mL, respectively, and the MN-IC50 values for Rv1–Rv3 were 0.02, 0.06, and 1.09 µg/mL. It also retained activity against diverse clinical isolates although HI potency varied among strains. In mouse challenge experiments, intratracheal administration of Nb74 conferred robust protection, achieving 100% and 80% survival against Rv1 and Rv2, respectively, when administered prophylactically (2 mg/kg) or therapeutically (4 mg/kg). Treated mice showed accelerated body weight recovery, reduced lung viral load, and alleviated pulmonary pathology. Mechanistic analyses indicated that Nb74 neutralizes virus by blocking viral attachment to the host. Furthermore, combined hydrogen-deuterium exchange mass spectrometry (HDX-MS) with escape mutant analysis mapped its epitope to a conserved lateral patch on the HA1 subunit, consistent with a conformational epitope. Overall, these results demonstrate the therapeutic promise of intratracheally delivered Nb74 and provide insights for H7 AIVs vaccine design.

Source: 

Link: https://journals.asm.org/doi/10.1128/jvi.00563-26

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Evaluation of #antiviral #treatments for highly pathogenic avian #influenza virus #infections in #feline species

 

Abstract

In 2020, highly pathogenic avian influenza (HPAI) isolates from clade 2.3.4.4b emerged in Europe and spread globally, including in bovine hosts in the USA. Viruses from this clade cause minimal disease in dairy cattle, characterized by decreased milk production but low mortality rates. Infections have also occurred in feline hosts. In contrast to cows, infection of cats (and closely related species, including skunks and foxes) can result in severe neurological signs and mortality. Documented feline H5N1 infections from clade 2.3.4.4.b have a mortality rate of approximately 80% following rapid onset of clinical signs. No antiviral compounds have been tested in an experimental feline model; however, anecdotal clinical evidence suggests early treatment with oseltamivir may improve outcomes in felines with HPAI. Here, we show the in vitro efficacy of several influenza inhibitors in feline glial astrocyte (PG-4) and kidney (CRFK) cell culture models using the clade 2.3.4.4.b virus Tx2/24 (H5N1). The neuraminidase inhibitor oseltamivir carboxylate did not effectively inhibit viral replication in either cell line. The cap-dependent endonuclease inhibitor baloxavir exhibited the strongest inhibition of this virus, with EC50 values of 30 nM in PG-4 and 1 μM in CRFK cells. Amantadine and rimantadine, M2 ion channel inhibitors, were unable to completely inhibit viral replication in either cell line at any concentration utilized. The broad-spectrum nucleoside analog GS-441524 demonstrated little to no inhibition of viral replication in either cell line. Additionally, the mutagenic NHC analogs EIDD-1931 and EIDD-2801 successfully inhibited viral replication at the maximum tested concentration of 100 μM but exhibited significant cytotoxicity. Our findings suggest that baloxavir should be considered by veterinary clinicians as the first-line drug of choice when presented with felines or other species infected with HPAI.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Cornell Feline Health Center, Ithaca, US

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.06.09.730954v1

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#Human ACE2‑specific benzothiazole-based allosteric #inhibitor against pan ‑ #sarbecoviruses

 

Abstract

Emerging SARS‑CoV‑2 variants and related zoonotic sarbecoviruses rely on ACE2 for cell entry, motivating host‑directed antivirals that block spike-ACE2 interaction. Here, we characterize MB‑32, a benzothiazole small molecule that binds ACE2, selectively disrupts binding of SARS‑CoV‑2 spike receptor‑binding domain to ACE2, and preserves ACE2 enzymatic activity across species. MB‑32 potently inhibits entry of SARS‑CoV‑2 variants, SARS‑CoV‑1 and diverse bat/pangolin sarbecoviruses in ACE2‑expressing cells, while sparing vesicular stomatitis virus and authentic MERS‑CoV, indicating non‑virucidal, ACE2‑focused activity. Biochemical and biophysical analyses, supported by ACE2 mutagenesis, support a model in which MB‑32 engages a non‑catalytic surface pocket on the ACE2 N‑terminal helix to allosterically disrupt spike attachment. Intranasal MB‑32 achieves high airway concentrations, protects male ACE2‑transgenic mice and hamsters from SARS‑CoV‑2 disease, and prevents contact transmission of Omicron‑lineage viruses without detectable cardiovascular toxicity. These findings establish MB‑32 as a host‑targeted ACE2 entry inhibitor and provide a framework for small‑molecule ACE2‑directed antivirals against current and future sarbecovirus spillovers.

Source: 

Link: https://www.nature.com/articles/s41467-026-73944-x

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Broad heterologous #protection against #Influenza A viruses by an adjuvant-free modular mucosal T-cell #vaccine #platform

 

Abstract

Rapid antigenic evolution of Influenza A viruses (IAVs) enables their escape from strain-specific vaccine immunity, underscoring the need for broadly protective strategies. Here, we describe a modular, adjuvant-free mucosal vaccine platform that elicits potent and cross-protective T cell immunity. The approach uses overlapping CD4+ and CD8+ epitope-dense regions from the consensus IAV M1 and NP proteins, identified through computational and functional screening. These peptides are delivered using polylactic-co-glycolic acid (PLGA) microparticles, engineered for selective uptake by antigen-presenting cells and enabling sustained, pH-responsive antigen release. This design enhances antigen processing and MHC cross-presentation, functionally substituting for a conventional adjuvant. This formulation drives robust activation of primed human as well as murine CD4+ and CD8+ T cells and confers broad protection against homologous (H1N1, H3N2) as well as heterologous (H5N1) IAV strains in immunized mice. Overall, this adjuvant-free dose-sparing platform establishes an adaptable framework for next-generation broadly-protective vaccines against rapidly evolving viruses.

Competing Interest Statement

R.T.Y. and S.T. are co-inventors on an unpublished patent titled Immunogenic peptide(s), composition(s) and application(s) thereof broadly protective against Influenza, Indian patent application number 202541082426. The other authors declare that they have no competing interests.

Funder Information Declared

DBT-ENDFLU, BT/IN/EU-INF/15/RV/19-20

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.03.29.715080v2

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A mouse #model of #human-derived #H10N3 #influenza enables preclinical evaluation of #antiviral efficacy

 

Highlights

• Revealing one human-derived H10N3 virus was highly lethal to C57BL/6J, ICR, and BALB/c mice;

• Successfully establishing the first human-derived H10N3-infected mice model.

• In vitro antiviral assay revealed that this human-origin H10N3 virus exhibits natural resistance to oseltamivir, but remains sensitive to peramivir and baloxavir.

• Oseltamivir or BM immediate treatment after infection effectively prevented mortality caused by H10N3,but their efficacy with a 24h delay were significantly weaker than that of peramivir.

• BM one-dose treatment with a 24h delay has no protective effect, but BM combination with NAIs exhibits significant additive effect on mortality caused by H10N3.

• BM and NAIs combination may be a promising therapy for combating novel H10N3 virus infection.

Abstract

    Human infections with avian influenza A (H10N3) have recently been reported, representing a notable global public health concern. To seek effective strategies for emerging H10N3 virus infection and provide tools for vaccine and antiviral drugs development, we established a mouse model with a novel human-derived H10N3 virus. Our findings revealed that this human-derived H10N3 virus was highly lethal to C57BL/6J, ICR, and BALB/c mice. Neuraminidase inhibitors (oseltamivir or peramivir) effectively conferred protection for H10N3 low-lethal infection, but the efficacy of peramivir is superior to that of oseltamivir. One single dose of baloxavir marboxil (BM) treatment at 2 h post-infection provides complete protection against mortality, but BM treatment with a 24h delay has no protective effect against mortality caused by H10N3 virus infection. Furthermore, BM multiple doses treatment with a 24h delay for H10N3 infection remains effective in preventing weight loss and enhancing viral clearance, but its protective efficacy against mortality was significantly attenuated. However, both in vitro and in vivo combination of BM with NAIs exhibit significant additive effect against H10N3 virus infection than BM or NAIs monotherapy. Our findings suggest that combination of BM with NAIs represents a promising therapeutic strategy for emerging H10N3 infections in clinical practice.

Source: 

Link: https://www.sciencedirect.com/science/article/abs/pii/S0166354226000951?via%3Dihub

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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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Computational #design of an ultrapotent #deltacoronavirus miniprotein #inhibitor

 

Significance

Multiple porcine deltacoronavirus (PDCoV) spillovers occurred in Haiti and there are currently no vaccines or therapeutics approved for use in humans. We computationally designed PDCoV miniprotein inhibitors and identified one (MB11) that potently and broadly neutralizes distantly related delta-coronaviruses. MB11 is resistant to multiple biochemical stresses, an ideal property for easy storage and delivery. These data pave the way for developing therapeutics to prepare for possible future PDCoV outbreaks.

Abstract

Multiple spillovers of porcine deltacoronavirus (PDCoV) into humans in Haiti highlight its zoonotic potential and the need for targeted interventions. No approved vaccines or therapeutics are available for use in humans against any DCoVs. Here, we report the de novo design of PDCoV miniprotein inhibitors (aka minibinders, MBs) and show that one of them, MB11, binds with picomolar affinity to the PDCoV receptor-binding domain (RBD). MB11 potently inhibits PDCoV, outcompeting monoclonal antibodies, and cross-reacts with and broadly neutralizes a panel of distantly related DCoVs. We determined a cryoelectron microscopy structure of MB11 bound to the PDCoV RBD which reveals the molecular basis of broad DCoV neutralization through interference with host receptor engagement. Deep mutational scanning of the PDCoV RBD reveals that MB11 has a high barrier to viral escape with only few mutations mediating escape without dampening APN receptor binding. MB11 resists stringent biochemical stresses, including high temperature, low pH, and proteolysis, which may enable delivery to various tissues for viral inhibition. This work delineates a prime candidate for clinical evaluation against PDCoV infection and for pandemic preparedness.

Source: 

Link: https://www.pnas.org/doi/abs/10.1073/pnas.2533456123?af=R

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#Niclosamide Inhibits the #Replication of Highly Pathogenic Avian #Influenza #H5Nx Viruses and Antiviral-Resistant #Mutants

 

Highlights

• Niclosamide blocks the replication of highly pathogenic avian influenza H5 viruses

• Niclosamide is effective against H5 viruses with antiviral-resistant substitutions

• Niclosamide has potential as host-targeting anti-influenza drug

Abstract

The recurrent spillover of highly pathogenic avian influenza (HPAI) H5 viruses into humans represents a major public health concern that is exacerbated by the emergence of drug-resistant viral variants. Host-targeting antiviral approaches, including drug repurposing, offer a promising alternative to conventional virus-directed therapeutics. Here, we evaluated the antiviral activity of niclosamide, an FDA-approved anthelmintic drug, against four HPAI A(H5Nx) viruses, two A(H5N1), one A(H5N6), and one A(H5N8), recently isolated from human cases. Niclosamide inhibited all four viruses in plaque reduction assays with MDCK cells, with low inhibitory concentration 50% (IC50) values (0.68–1.40 μM) and minimal cytotoxicity at effective concentrations. These values were more potent than the IC50 values observed for the RdRp inhibitor favipiravir. Niclosamide treatment plus either baloxavir marboxil or favipiravir resulted in additive or near-additive interactions, as indicated by synergy scores of ±10. Importantly, niclosamide retained antiviral activity against HPAI A(H5Nx) viruses bearing resistance-associated amino acid substitutions (i.e., PA-I38T, baloxavir resistance and PB1-K229R, favipiravir resistance), consistent with its host-directed mechanism of action. Although there are barriers to be overcome such as a narrow therapeutic window, largely attributable to its poor bioavailability and some cytotoxicity, our findings suggest niclosamide has potential as a host-targeting therapeutic option against emerging zoonotic influenza viruses, particularly in settings involving antiviral-resistant escape mutants.

Source: 

Link: https://www.sciencedirect.com/science/article/pii/S016635422600080X?via%3Dihub

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Evaluation of Cross-Immunogenicity of #Ferret #Antisera Following Immunization with #H5N1 #Vaccine Strains

 

Abstract

Background: 

Highly pathogenic avian influenza H5N1 viruses of clade 2.3.4.4b have spread globally since 2021, causing extensive outbreaks in avian populations and repeated spillovers into diverse mammalian hosts, including humans. These cross-species transmission events highlight ongoing pandemic risks and underscore the need for vaccine strategies that reflect viral evolution at the human–animal interface. Despite the availability of licensed H5 vaccines and newly recommended World Health Organization (WHO) candidate vaccine viruses (CVVs), the extent to which these vaccines elicit cross-reactive antibody responses against contemporary clade 2.3.4.4b viruses, including mammalian spillover isolates of avian origin, remains incompletely characterized. 

Method: 

In this study, ferret antisera were generated using four WHO-recommended H5 CVVs, including a clade 1 strain (A/Vietnam/1194/2004) and three clade 2.3.4.4b strains (A/Astrakhan/3212/2020, A/American wigeon/South Carolina/22-000345-001/2021, and A/Ezo red fox/Hokkaido/1/2022), formulated with alum adjuvant to reflect licensed vaccine formulation used in national preparedness programs. Antibody responses and cross-reactive activity were evaluated using hemagglutination inhibition (HI) and microneutralization (MN) assays against homologous vaccine strains and a feline-origin clade 2.3.4.4b H5N1 field isolate from Korea, A/Feline/Korea/SNU-01/2023. 

Results: 

Antisera induced by clade 2.3.4.4b CVVs showed cross-reactive antibody responses against homologous and heterologous clade 2.3.4.4b viruses and demonstrated measurable HI and MN responses against the feline-origin field isolate. In contrast, antisera raised against the clade 1 Vietnam CVV exhibited limited cross-reactivity against clade 2.3.4.4b viruses. Overall, clade 2.3.4.4b CVVs generally showed higher antibody responses than the clade 1 vaccine strain across multiple panels. 

Conclusions: 

These findings provide descriptive insights into antigenic differences between clade 1 and clade 2.3.4.4b viruses and support the antigenic relevance of clade 2.3.4.4b CVVs for contemporary H5N1 strains. This study highlights the importance of ongoing antigenic evaluation to inform vaccine strain selection within a One Health framework.

Source: 

Link: https://www.mdpi.com/2076-393X/14/4/301

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Heterologous Sequential #mRNA #Vaccination of Indian Rhesus #Macaques Elicits Broad Binding and Neutralizing #Antibody Responses Against Diverse #Henipaviruses

 

Abstract

Henipaviruses (HNVs), including Nipah virus (NiV) and Hendra virus (HeV), are highly pathogenic and often lethal zoonotic viruses with broad species tropism and no approved human vaccines. The emergence of genetically divergent HNVs—including Ghana virus (GhV), Langya virus (LayV), and Mojiang virus (MojV)—emphasizes the need for broadly protective countermeasures. Here, we evaluated the antibody (Ab) responses to sequential mRNA vaccines encoding the membrane-bound attachment glycoprotein (gG) from NiV, GhV, and/or LayV in a pilot study with Indian rhesus macaques. Serum binding Ab responses were quantified by ELISA against five soluble gG antigens (NiV, HeV, GhV, LayV, MojV). Functional activity was assessed by neutralization assays using NiV, HeV, and GhV pseudoviruses, and by receptor-blocking ELISA. Sequential vaccination induced high-titer IgG binding against all five HNV gGs with increasing breadth after each dose. Pan-genus regimens elicited moderate neutralizing Ab titers against NiV, HeV, and GhV, whereas the NiV-only regimen elicited potent but narrow neutralization against NiV and HeV. Conversely, the GhV-LayV-GhV regimen elicited strong binding to GhV, LayV, and MojV gG and robust neutralization of GhV pseudovirus, but limited cross-reactivity to NiV and HeV. In this pilot study, we demonstrated that mRNA vaccination can elicit broadly reactive binding and neutralizing Ab responses across phylogenetically distant HNVs. Additionally, we show GhV pseudovirus neutralization for the first time. Collectively, these data provide a foundation for the development of next-generation pan-genus HNV vaccines capable of mitigating future HNV outbreaks.

Source: 

Link: https://www.mdpi.com/1999-4915/18/5/487

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#Preclinical evaluation of an #mRNA #vaccine developed from the first #human isolate of #bovine #H5N1

 

Highlights

• SM102 and DB-Y ionizable lipids deliver H5 mRNA vaccine with high efficiency and safety

• Vaccine-induced antibody and T cell response protect mice from H5N1 challenge

• Pre-existing H1 immunity does not diminish H5-specific immunogenicity

• Vaccine fully protects chicken against clade 2.3.4.4b/h H5 virus challenge

Summary

Given the global threat posed by H5N1 clade 2.3.4.4b avian influenza, rapid development of effective vaccines is imperative. We design an mRNA vaccine encoding hemagglutinin (HA) from A/Texas/37/2024, the first bovine-to-human strain. In murine models, both wild-type and cleavage-site-modified HA vaccines elicit robust and durable humoral immunity, along with a balanced Th1/Th2 response, conferring complete protection against lethal homologous viral challenge. The vaccine, along with the World Health Organization (WHO)-recommended candidate (A/Astrakhan/3212/2020), elicits cross-clade binding antibody responses and demonstrates improvement against specific clades at a 1 μg dose. Pre-existing H1 immunity does not diminish H5-specific immunogenicity. In avian species, the vaccine also provides full protection against lethal clades (2.3.4.4b and 2.3.4.4h). Formulated with another ionizable lipid, the vaccine elicits responses comparable to benchmark lipid nanoparticles (LNPs) and shows a favorable safety profile in rats. This work establishes a rapidly adaptable mRNA-LNP vaccine prototype for pandemic preparedness against evolving avian influenza threats.

Source: 

Link: https://www.cell.com/cell-reports-medicine/fulltext/S2666-3791(26)00119-9?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2666379126001199%3Fshowall%3Dtrue

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MF59-adjuvanted A/Astrakhan #influenza #vaccine induces cross-neutralizing #H5N1 #antibodies in #ferrets against circulating clade 2.3.4.4b viruses

 

Abstract

The continued global spread of highly pathogenic avian influenza A(H5N1) viruses, particularly clade 2.3.4.4b, has increased zoonotic spillover risk and underscored the urgency of pandemic preparedness. Human vaccination is a key strategy for mitigating severe disease and limiting transmission, especially in a setting where avian influenza viruses pose a zoonotic threat. We evaluated the immunogenicity of the MF59-adjuvanted, egg-derived A/Astrakhan/3212/2020 (H5N8) influenza vaccine (CBER-RG8A) in ferrets. To assess cross-reactivity, we generated pseudoviruses bearing HA and NA from circulating A(H5N1) 2.3.4.4b viruses, including North American (B1.13 and D1.1) and Eurasian (DI.2) genotypes. Immunogenicity was assessed using hemagglutination inhibition and microneutralization assays. A single dose elicited robust neutralizing titers (GMT ≥ 160), while a second dose increased titers by ≥3.3-fold. Cross-reactivity was maintained across most strains; however, responses were reduced up to 8-fold against strains harboring the A156T HA mutation, which may introduce a glycosylation site at antigenic site B. Limited responses were detected against divergent clades, with modest titers against clade 2.3.2.1a. These findings suggest broad protection induced by the CSL Seqirus pandemic vaccine against contemporary clade 2.3.4.4b A(H5N1) viruses and underscore the value of ferret immunogenicity data in informing strain selection and regulatory preparedness when human clinical data are unavailable.

Source: 

Link: https://www.nature.com/articles/s41541-026-01438-4

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