Sex differences in #vaccine-induced #neuraminidase cross-recognition and #protection against #H5N1 in mice

 

Abstract

Despite concerns about the spread and pandemic potential of H5N1, there is no commercial H5N1 vaccine. Seasonal influenza vaccines offer some cross-protection against H5N1, but to date there has been no consideration of whether protection differs between the sexes. We investigated immune responses and protection in adult male and female C57BL/6 mice following vaccination with either inactivated H1N1 or H5N1 (LAIV backbone) virus vaccines. Vaccination induced strong homologous antibody responses, with females generating greater total IgG than males against both H1N1 and H5N1 vaccine, which was primarily mediated by greater IgG responses to neuraminidase (NA) than hemagglutinin (HA) protein. IgG cross-recognition of H1N1 also was greater among H5N1 vaccinated females and was primarily caused by greater IgG responses to N1. IgG2b and IgG2c were the primary isotypes generated in response to these vaccines, with females having greater IgG2b responses and greater binding to FcγRIV for avian and human NA than males in response to both homologous and heterologous vaccination. Antibody-dependent complement deposition was measured as an FcR-mediated non-neutralizing response against HA and NA and was robust in both sexes. Vaccinated females had greater neutralizing antibody titers than males against the homologous vaccine virus, 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 cleared virus faster than their male counterparts. These findings highlight that female-biased NA-specific antibodies result in greater cross-protection and should be considered in studies of influenza vaccines.

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

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.05.26.728011v1

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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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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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A single PA-X #mutation in #bovine-origin #H5N1 #influenza virus reduces #pathogenicity in mice

 

Abstract

Dairy cows have emerged as a reservoir for human infection with highly pathogenic avian influenza (HPAI) H5N1. At the bovine-human interface, H5N1 strains may acquire adaptive mutations that influence their zoonotic potential. Sequence analysis identified a K142E substitution (bovine to human) in the PA and PA-X proteins, with the potential to affect both polymerase activity and host shutoff. Here, we used a loss-of-function approach to investigate how the bovine substitution (E142K) in PA/PA-X impacts viral replication, host shutoff activity, and pathogenicity in the human H5N1 background. Viral growth kinetics demonstrated that the virus containing the E142K substitution is attenuated, with reduced replication compared to wild-type (WT) virus. Consistently, PA-X-mediated host shutoff activity was reduced, resulting in increased induction of interferon (IFN) responses relative to WT. In vivo, mice infected with the E142K mutant virus survived, whereas infection with the WT virus was uniformly lethal. Despite comparable viral titers and inflammation score in mouse lungs, cytokine and chemokine profiling revealed distinct immune responses, with reduced CCL2 and increased CCL5 and IFN-γ in mice infected with the E142K mutant virus compared to mice infected with the WT virus. These findings indicate that increased virulence of the human-adapted strain is driven by a PA-X mutation that modulates inflammatory responses, producing distinct immune signatures linked to host survival or viral lethality rather than changes in polymerase activity by PA. Collectively, these results highlight PA-X as a key determinant of pathogenicity of H5N1 and a potential target for the rational design of antiviral strategies.

Competing Interest Statement

The authors have declared no competing interest.

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.05.09.724031v1

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#Genetic and #biological characterization of #H9N2 avian #influenza viruses isolated from #swine in #China

 

Abstract

Background

H9N2 avian influenza virus (AIV) has been circulating in poultry in China for decades and are undergoing adaptation to mammals, posing potential pandemic risks. To investigate the prevalence of H9N2 AIVs in swine, we conducted surveillance in Shandong Province from 2021 to 2023.

Results

Two H9N2 influenza virus strains, A/swine/Shandong/417/2021(Sw/SD/417/21) and A/swine/Shandong/662/2022 (Sw/SD/662/22), were successfully isolated from swine and genetically characterized. Phylogenetic analyses showed that both isolates were reassortants containing gene segments from multiple H9N2 AIV lineages and closely related to currently circulating H9N2 AIV. Key molecular marker analysis revealed that both isolates carried mammalian-adaptive residues in the HA receptor-binding sites (183 N, 190 V, 226 L), a novel HA cleavage site variant (PSKSSRGL), PB2 mutations (A588V, E627V), and the M2 S31N substitution, suggesting potential adaptation to mammalian hosts and resistance to adamantane antivirals. Mice infection experiments demonstrated efficient viral replication in the respiratory tract, particularly in the lungs, but only mild histopathological changes were observed, with no significant weight loss or mortality, indicating low pathogenicity in mice. Serological surveillance of 3,172 swine serum samples showed a low prevalence of H9N2 influenza virus infection (0.44%), with positive samples sporadically distributed across regions and years.

Conclusion

In summary, although H9N2 AIV infection in swine is rare and generally mild, the presence of mammalian-adaptive markers and reassortant genomes highlights the potential risk of cross-species transmission and subclinical adaptation. Continuous avian–swine–human influenza surveillance is therefore essential to mitigate the potential threat posed by H9N2 AIV.

Source: 

Link: https://link.springer.com/article/10.1186/s12917-026-05501-z

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Variable #transmission efficiency of #mammalian origin #HPAI D1.1 #H5N1 strains in #ferrets

 

Abstract

Highly pathogenic avian influenza H5N1 2.3.4.4b genotype D1.1 lineage continues to predominate in the United States wild bird population and has spilled over into dairy cattle three independent times. To assess the transmission risk of this sublineage, we performed direct-contact transmission experiments for three distinct D1.1 strains in ferrets. Two of these strains were isolated from humans and one from a lethal cat infection. We found that only one human isolate (A/NV/10/2025) was able to transmit efficiently between ferrets. Compared to the other strains, this isolate harbored the mammalian adaptive PB2 D701N mutation, suggesting this mutation may be critical for D1.1 transmission as opposed to the PB2 E627K substitution present in the lethal cat isolate. Based on these data we conclude that the transmission fitness of D1.1 strains is modest but that special attention should be paid to emergence of adaptation at the PB2 701 position.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

National Institute of Allergy and Infectious Diseases, https://ror.org/043z4tv69, 75N93021C00015, 75N93021C00017

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.05.07.722809v1

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Characterization of atypical #Ebola virus disease in #ferrets

 

Abstract

Ebola virus (EBOV) infection typically results in severe—and often lethal—acute disease. However, increasing evidence suggests that EBOV can persist in certain immune-privileged tissues, which may then serve as reservoirs for the later reemergence of EBOV and disease recrudescence. Here, we report atypical EVD recrudescence in a ferret model inoculated with an otherwise lethal dose of EBOV and treated with low doses of a highly potent monoclonal antibody cocktail. Among 32 antibody-treated ferrets, 14 animals survived, while 8 succumbed to acute EVD within about 5–8 days. The remaining 10 animals succumbed to atypical EVD between 12 and 18 days post-infection (DPI) despite having shown no, or very minor, signs of illness during the acute phase of disease. While viremia disappeared by 14 DPI in most animals that succumbed to atypical EVD, it rebounded modestly just prior to death. Unlike animals that died of acute EVD, those that died of atypical EVD showed only a moderate systemic inflammatory response and few signs of organ dysfunction, in line with low levels of virus in the liver and spleen. Interestingly, however, ferrets that died of atypical EVD showed high levels of virus in the brain, consistent with increased markers of inflammation in the central nervous system and significant pathological changes, including a breakdown in the blood-brain barrier and severe meningoencephalitis. Not only does this study shed important light on the atypical and underappreciated manifestations of EVD, but it also establishes the ferret as a valuable model of EBOV recrudescence.

Source: 

Link: https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1013916

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Prior #immunity to seasonal #influenza #H3N2 virus confers varying levels of cross - #protection against challenge with clade 2.3.4.4b #H5N1, #H7N9, or #H9N2 virus in a #ferret model

 

ABSTRACT

Evaluating how prior immunity to seasonal influenza viruses influences subsequent zoonotic influenza A virus (IAV) infection in animal models is critical for pandemic preparedness. In this study, we investigated the cross-protective effect of pre-existing A(H3N2) immunity in ferrets challenged with three distinct subtypes of zoonotic IAVs: low pathogenic A(H7N9) and A(H9N2) viruses, and highly pathogenic clade 2.3.4.4b A(H5N1) virus. Our results show that A(H3N2) preimmunity conferred some protection against A(H5N1) and A(H9N2) virus infection, as evidenced by more rapid viral clearance in the upper respiratory tract, reduced virus shedding in the nasal wash on select days post-inoculation, and a lowered frequency of viral detection in specific tissues compared with naive animals. In contrast, A(H3N2) preimmunity provided minimal cross-protection against A(H7N9) infection, as weight loss and viral dissemination in tissues were not significantly reduced in A(H3N2) preimmune ferrets relative to naive animals. These findings highlight the variable breadth and magnitude of cross-protection elicited by prior seasonal IAV immunity against zoonotic influenza virus challenges in the ferret model. Seasonal influenza A(H3N2) preimmunity provided differing levels of cross-protection against zoonotic influenza A virus infections in ferrets.

Source: 

Link: https://journals.asm.org/doi/10.1128/spectrum.03974-25

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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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#Prion shedding is reduced by chronic wasting disease {#CWD} #vaccination

 

Abstract

Chronic wasting disease (CWD) is a strictly fatal and highly contagious prion disease of wild and farmed cervids currently expanding in North America. Prion diseases are caused by conversion of the cellular prion protein to its pathological isoform PrPSc. Vaccination is considered a promising strategy to contain CWD, even though prion diseases do not show classical immune responses. For CWD containment, it is important that vaccines reduce shedding of prions in excreta, a major contributor to transmission. Here, we tested the effect of vaccines on prion shedding in feces and urine by vaccinating and prion infecting knock-in mice that recapitulate CWD pathogenesis as found in cervids. Vaccination reduced or even prevented CWD shedding in feces and urine collected between 30–90% of incubation time to disease. This is the first report showing that prion shedding can be blocked in a prion disease. For CWD specifically it may reduce the environmental prion burden and break the disease transmission cycle.

Source: 

Link: https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014166

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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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Dual-route #H5N1 #vaccination induces systemic and mucosal #immunity in murine and bovine #models

 

Abstract

Highly pathogenic H5N1 avian influenza (clade 2.3.4.4b) has spread widely among dairy cattle herds since early 2024, causing major economic losses. This zoonotic event emphasizes the urgent need for H5 vaccines eliciting strong, durable, cross-reactive immune responses in cows. To address this, we immunized mice and cattle with a centralized consensus H5 vaccine, localizing near the central node of the human H5 phylogenetic tree. The vaccine was delivered using serotype-switched adenoviral vectors in a prime–boost regimen, combined with intramuscular and intranasal coadministration to target systemic and mucosal immunity and elicit strong humoral and cellular immune responses. This approach strategically integrates multiple innovative features: centralized consensus immunogens, mucosal targeting, and vector serotype switching aimed at maximizing immune protection against H5N1 viruses. Our results show that vaccination elicits strong humoral and cellular immunity in both mice and calves. In challenge experiments, vaccinated mice were fully protected against lethal infection with divergent H5N1 strains, including A/bovine/Ohio/B24OSU-439/2024. Vaccine-induced immunity was consistent across species, supporting the translatability of the mouse model findings to cattle. Overall, our findings represent a promising approach for immunizing key livestock, including cattle, against highly pathogenic avian influenza H5N1, mitigating agricultural losses, and reducing the risk of zoonotic transmission.

Source: 

Link: https://www.nature.com/articles/s41541-026-01460-6

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Cross - #protection against highly pathogenic avian #influenza #H5N1 virus from seasonal influenza #vaccines: a systematic review and meta-analysis of #ferret studies

 

ABSTRACT

The recent surge in spillover events of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b to humans and mammals in North America has raised urgent pandemic concerns. Human H5N1 vaccines are unavailable in most countries. We synthesized data from ferret challenge trials to evaluate whether widely available seasonal influenza vaccines confer cross-protection against lethal H5N1 infection. We systematically searched PubMed, Embase, and Web of Science for ferret studies of lethal H5N1 challenge published up to 5 July 2025 (PROSPERO #CRD42024520346). Random-effects meta-analyses were conducted to compare vaccine efficacy (VE) of seasonal influenza vaccines and H5N1 vaccines against H5N1-related mortality. Seroprotection was defined as a neutralizing antibody titre of ≥1:40. We identified 35 studies (157 trials). Seasonal influenza vaccines without N1 did not confer significant cross-protection (five trials; VE 14.8%, 95% CI –3.6 to 30.0). In contrast, VE was 73% for N1-containing seasonal influenza vaccines (19 trials; 95% CI 54–84) and 77% for H5N1 vaccines overall (133 trials; 95% CI 72–82) (p = 0.52). The VE of N1-containing seasonal influenza vaccines was modestly lower than that of H5N1 vaccines with seroprotection (88%; 66 trials; 95% CI 84–91; p = 0.009), but comparable to H5N1 vaccines that did not achieve seroprotection (63%; 67 trials; 95% CI 52–71; p = 0.29). The VE of seasonal influenza vaccines against H5N1 was robust across sensitivity analyses, with no evidence of publication bias (p = 0.99). Seasonal influenza vaccines significantly reduce H5N1-associated mortality in ferret trials, suggesting the cross-protection potential of currently available vaccines. Human studies are warranted.

Source: 

Link: https://www.tandfonline.com/doi/full/10.1080/22221751.2026.2654278

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The virus entry #inhibitor ARN-75039 provides therapeutic #protection against #Lassa virus infection in guinea pigs

 

Abstract

Lassa virus (LASV), a member of the Arenaviridae family, causes Lassa fever. There are no vaccines available for prevention of Lassa fever, and the primary therapeutic for treatment (ribavirin) has questionable antiviral activity and no formal approval for use. Here, we evaluated ARN-75039, an orally bioavailable broad-spectrum mammarenavirus entry inhibitor, against LASV infection in outbred Hartley guinea pigs exposed to a guinea pig–adapted LASV. ARN-75039 was administered for 14 days either 3 or 7 days postexposure (dpe) to LASV. In the first two studies, once-daily dosing at 3 dpe provided protection against lethal infection. A third study with twice-daily dosing at 7 dpe also achieved protection. Both drug regimens offered 100% protection at the lowest tested doses of 3.75 mg/kg (once-daily administration) or 7.5 mg/kg (twice-daily administration). ARN-75039–treated animals exhibited minimal disease signs and undetectable viremia. These results suggest that ARN-75039, for which a phase 1 human clinical trial has now been completed, may offer robust protection against LASV infection.

Source: 

Link: https://www.science.org/doi/10.1126/scitranslmed.adx0938

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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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#Genetic and #biological characterization of a #duck-origin clade 2.3.4.4b #H5N6 avian #influenza virus reveals partial #mammalian #adaptation

 

Highlights

• Duck-origin H5N6 virus A/Duck/Jiangsu/628/2022 shares high homology with the human strain A/Yangzhou/125/2022.

• The 628 strain shows mammalian adaptation markers: HA mutations enhance human receptors affinity and NA mutations reduce sensitivity to neuraminidase inhibitors.

• Limited airborne transmission but detectable droplet-mediated spread suggests increased mammalian transmission risk.

Abstract

Clade 2.3.4.4b H5Nx highly pathogenic avian influenza viruses (HPAIVs) have caused extensive outbreaks in poultry worldwide. H5 HPAIVs have caused sporadic but severe human infections in China, representing a persistent zoonotic threat. Here, we identified a duck-origin H5N6 HPAIV (A/Duck/Jiangsu/628/2022) through routine surveillance and assessed its biological characteristics and mammalian pathogenesis. Phylogenetic analysis revealed > 98% nucleotide identity between strain 628 and the concurrent human H5N6 strain A/Yangzhou/125/2022. Molecular characterization identified multiple mammalian adaptation markers: hemagglutinin substitutions (S137A, T160A, T192I) associated with enhanced human receptor binding; neuraminidase mutations (I117T, D198N) linked to reduced neuraminidase inhibitor susceptibility; and polymerase complex changes (PB1-D622G, PA-K142Q) conferring increased mammalian cell replication. In vitro studies demonstrated that 628 virus replicated more efficiently in mammalian than in avian cells and exhibited dual receptor-binding specificity. Mouse pathogenicity assays revealed moderate virulence with progressive lung pathology. Critically, transmission experiments confirmed both direct contact and airborne transmission capabilities of 628 in guinea pigs. These findings demonstrate that circulating H5N6 viruses have acquired partial mammalian adaptation while retaining avian fitness, significantly elevating pandemic potential. Enhanced surveillance of wild bird populations, poultry farms, and live poultry markets is urgently needed to develop effective prevention and control strategies.

Source: 

Link: https://www.sciencedirect.com/science/article/abs/pii/S037811352600146X?via%3Dihub

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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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Next-generation #inhibitors of #SARS-CoV-2 #Mpro overcome the deficiencies of #Paxlovid

 

Abstract

It remains elusive to design peptidomimetic inhibitors of SARS-CoV-2 main protease (Mpro) refractory to multiple deficiencies of Paxlovid (ritonavir-boosted nirmatrelvir), pertaining mainly to E166X mutations-conferred drug resistance and inherent pharmacokinetic limitations to nirmatrelvir. We identify via virtual screening an iso-quinoline P1 moiety in place of the traditional γ-lactam and design iso-quinoline-containing inhibitors with high affinity for Mpro and its nirmatrelvir-resistant E166X mutants. Further optimization at P4 cultivates distinctive peptidomimetic inhibitors with drastically improved pharmacokinetic properties and significantly enhanced antiviral efficacy independent of ritonavir. Two such inhibitors, FD3-32 and FD3-36, also potent against SARS-CoV-1 and MERS-CoV Mpro, are more effective as a monotherapy regimen than Paxlovid in reducing viral loads in vivo and protecting infected male mice from acute lung injury. Here, we report the discovery of next-generation SARS-CoV-2 Mpro inhibitors that overcome the deficiencies of Paxlovid, promising efficacious antivirals critical for mitigating the current and future pandemics of coronaviruses.

Source: 

Link: https://www.nature.com/articles/s41467-026-71436-6

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Broad #protection against #Influenza A Viruses via an adjuvant-free #mucosal microparticle #vaccine with conserved CD8/CD4 bispecific peptides

 

Abstract

Influenza A viruses (IAVs) cause substantial global morbidity and mortality and are responsible for most known viral pandemics. Their rapid antigenic evolution enables escape from natural and vaccine-induced immunity, requiring annual vaccine reformulation, which offers limited breadth and variable effectiveness. Although a universal influenza vaccine remains a critical objective, most strategies have focused on conserved viral glycoproteins to elicit broadly neutralizing antibodies, with comparatively fewer efforts targeting conserved T cell antigens to achieve cross-subtype protection. Current T cell-based approaches often rely on individual CD8+ epitopes, which are limited by peptide instability, delivery constraints, and dependence on adjuvants. Here, we demonstrate a T cell-focused vaccine strategy that uses evolutionary consensus of IAV M1 and NP from the H1N1 and H3N2 subtypes to predict, map, and screen conserved regions enriched with multiple CD8+ and CD4+ epitopes. We selected the top-performing peptides from immunogenicity screening. We encapsulated them in polylactic-co-glycolic acid microparticles (PLGA-MPs) engineered for selective uptake by APCs and pH-dependent sustained release. Intranasal delivery of this vaccine formulation targeted the primary site of infection and induced robust mucosal immunity without the need for conventional adjuvants. Both human and murine influenza-experienced T cells mounted potent recall responses to the vaccine. In mice, immunization elicited strong CD8+ and CD4+ T cell responses and conferred broad protection against homologous H1N1 and H3N2 as well as heterologous H5N1 IAV subtypes. These findings collectively establish a mucosal, T cell-based vaccine platform that is adjuvant-free and capable of providing broad protection against IAV and other viruses with pandemic potential.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

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

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.03.29.715080v1

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