Clade 2.2 H5N1 influenza viruses have caused an unusually high number of human infections, providing a unique opportunity to investigate early molecular steps associated with host adaptation. Although most work has focused on hemagglutinin (HA), the contribution of neuraminidase (NA) to these early adaptive events has remained unclear. By analyzing publicly available sequences from clade 2.2-infected patients, we identified 20 NA mutations and compared their phenotypes to 20 mutations acquired during diversification in primary human airway cells under drug-free conditions. Most patient-derived NA mutations resulted in modest reductions in sialidase activity, keeping activity within a functional range that supported improved replication in α2,6 sialylglycan (α2,6 Sia)-dominant environments, whereas excessive reduction impaired fitness. Notably, the phenotypes of culture-selected and patient-derived mutations were highly concordant, suggesting that these NA changes arose through natural selection rather than antiviral pressure. Re-analysis of patient sequences further revealed that many adaptive NA mutations co-occur with HA mutations that confer only weak, partial α2,6 Sia binding. Using reverse genetics, we found that such naturally occurring HA/NA mutation pairs acted cooperatively in a receptor-context-dependent manner to support α2,6-associated replication relative to HA-only mutants, placing these variants within a constrained "early-adaptation space" characterized by limited α2,6 engagement and moderately reduced NA activity. Together, these findings indicate that early human adaptation of clade 2.2 H5N1 involves not only HA and PB2, but also incremental, cooperative tuning of NA function. Monitoring coordinated HA-NA evolution may therefore improve risk assessment frameworks for zoonotic influenza viruses poised at early stages of human host adaptation.

Background A simultaneous outbreak of respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) occurred in Ube, Yamaguchi Prefecture, Japan, from January to April 2025. Both viruses belong to the family Pneumoviridae and cause clinically similar respiratory illnesses in children. Whether sharing a care room between RSV-infected and hMPV-infected children leads to cross-infection has not been previously investigated. Methods Children aged 11 months to 11 years who tested positive for RSV or hMPV by rapid antigen tests at Suzuki Pediatric Clinic were enrolled in the sick-child care facility of the same clinic. RSV-positive and hMPV-positive children were cared for in the same room. Cross-infection was prospectively monitored for 1 to 4 months after discharge. Results A total of 54 children participated (RSV: 22, hMPV: 32; male: 31, female: 23; median age: 3 years, range: 11 months to 11 years). Shared care was conducted over 23 sessions from January to April 2025, with 2 to 7 children per session in rooms measuring 10.4 to 22.4 m². No cross-infection was observed during the 1- to 3-month follow-up period. One RSV-infected infant (aged 11 months) subsequently developed hMPV infection 21 days after discharge; however, given that this interval exceeds the known incubation period of hMPV (3–6 days), this case was considered a community-acquired infection. Conclusion Shared sick-child care of RSV- and hMPV-infected children did not result in cross-infection over a follow-up period of 1 to 3 months. Viral interference, possibly mediated by the innate immune response including interferon induction, may explain this finding. Shared-room care of children with RSV and hMPV may be a safe and practical option for sick-child care facilities during co-epidemic periods.

Avian influenza viruses continue to challenge poultry and human health; therefore, careful surveillance and evaluation of emerging viruses are important for animal disease control and human influenza pandemic preparedness. In this study, we detected a series of H3N3 subtype avian influenza viruses in chickens, pigeons, and ducks during our routine surveillance and diagnosis between September 2022 and May 2023. We performed extensive analyses to fully understand the origins of these viruses and their risk to animals and humans. We found that the viruses were complex reassortants; the viruses from chickens and pigeons carry genes mainly derived from H3N8 viruses and H10N3 viruses, whereas the two duck viruses were reassortants of duck and wild bird viruses. The chicken and pigeon, but not duck, viruses replicated in multiple organs of chickens and were shed for up to 13 days, but none caused disease or death. Six of the viruses tested all bound to both avian- and human-type receptors. Seventeen viruses were tested in mice and most replicated efficiently but were not lethal. Six viruses were tested in guinea pigs, and four of them transmitted efficiently via respiratory droplets. Our study thus identified novel H3N3 avian influenza viruses and revealed their zoonotic potential, thereby emphasizing the importance of careful monitoring and control of H3 viruses in animals.

Highly pathogenic H5N1 avian influenza (HPAI H5N1) viruses occasionally infect, but typically do not transmit, in mammals. In the spring of 2024, an unprecedented outbreak of HPAI H5N1 in bovine herds occurred in the USA, with virus spread within and between herds, infections in poultry and cats, and spillover into humans, collectively indicating an increased public health risk1-4. Here we characterize an HPAI H5N1 virus isolated from infected cow milk in mice and ferrets. Like other HPAI H5N1 viruses, the bovine H5N1 virus spread systemically, including to the mammary glands of both species, however, this tropism was also observed for an older HPAI H5N1 virus isolate. Bovine HPAI H5N1 virus bound to sialic acids expressed in human upper airways and inefficiently transmitted to exposed ferrets (one of four exposed ferrets seroconverted without virus detection). Bovine HPAI H5N1 virus thus possesses features that may facilitate infection and transmission in mammals.

Congenital pulmonary lymphangiectasia (CPL) is associated with fetal pulmonary venous obstructive physiology. The precise morbidity of CPL is unknown as CPL is generally fatal in neonates. Here, we report an infant with secondary CPL in total anomalous pulmonary venous connection (TAPVC). He developed severe pulmonary hypertension (PH) after corrective surgery for TAPVC. However, cardiac catheterization showed mild left pulmonary venous obstruction (PVO), which was deemed unnecessary for re-intervention. He died at 11 months-old due to an exacerbation of PH. Autopsy revealed medial hypertrophy of the pulmonary arteries, mild left PVO, and marked dilatation and proliferation of the pulmonary lymphatics which might have been involved in the PH, although CPL was not conclusively identified based on the previous biopsy findings. We should be aware of the possibility of CPL in addition to postoperative PVO when encountering patients with fetal pulmonary venous obstructive physiology. Furthermore, a cautious approach to the interpretation of lung biopsy results is warranted.

Pediatrics InternationalVolume 66, Issue 1 e15743 CLINICAL NOTE Japanese siblings with multicentric osteolysis nodulosis and arthropathy Seigo Okada, Corresponding Author Seigo Okada [email protected] orcid.org/0000-0002-9150-1913 Department of Pediatrics, Yamaguchi University Graduate School of Medicine, Ube, Japan Correspondence Seigo Okada, Department of Pediatrics, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi 755-8505, Japan. Email: [email protected]Search for more papers by this authorEitaro Suzuki, Eitaro Suzuki Suzuki Children's Clinic, Ube, JapanSearch for more papers by this authorYasuo Suzuki, Yasuo Suzuki Suzuki Children's Clinic, Ube, JapanSearch for more papers by this authorTadashi Moriwake, Tadashi Moriwake Department of Pediatrics, Iwakuni Clinical Center, National Hospital Organization, Iwakuni, JapanSearch for more papers by this authorKosei Hasegawa, Kosei Hasegawa orcid.org/0000-0002-1751-6527 Department of Pediatrics, Okayama University Hospital, Okayama, JapanSearch for more papers by this authorAyumi Omuro, Ayumi Omuro Division of Cardiology, Department of Medicine and Clinical Science, Yamaguchi University Graduate School of Medicine, Ube, JapanSearch for more papers by this authorShunji Hasegawa, Shunji Hasegawa Department of Pediatrics, Yamaguchi University Graduate School of Medicine, Ube, JapanSearch for more papers by this author Seigo Okada, Corresponding Author Seigo Okada [email protected] orcid.org/0000-0002-9150-1913 Department of Pediatrics, Yamaguchi University Graduate School of Medicine, Ube, Japan Correspondence Seigo Okada, Department of Pediatrics, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi 755-8505, Japan. Email: [email protected]Search for more papers by this authorEitaro Suzuki, Eitaro Suzuki Suzuki Children's Clinic, Ube, JapanSearch for more papers by this authorYasuo Suzuki, Yasuo Suzuki Suzuki Children's Clinic, Ube, JapanSearch for more papers by this authorTadashi Moriwake, Tadashi Moriwake Department of Pediatrics, Iwakuni Clinical Center, National Hospital Organization, Iwakuni, JapanSearch for more papers by this authorKosei Hasegawa, Kosei Hasegawa orcid.org/0000-0002-1751-6527 Department of Pediatrics, Okayama University Hospital, Okayama, JapanSearch for more papers by this authorAyumi Omuro, Ayumi Omuro Division of Cardiology, Department of Medicine and Clinical Science, Yamaguchi University Graduate School of Medicine, Ube, JapanSearch for more papers by this authorShunji Hasegawa, Shunji Hasegawa Department of Pediatrics, Yamaguchi University Graduate School of Medicine, Ube, JapanSearch for more papers by this author First published: 26 February 2024 https://doi.org/10.1111/ped.15743Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article. CONFLICT OF INTEREST STATEMENT The authors declare no conflicts of interest. REFERENCES 1Bhavani GSL, Shah H, Shukla A, et al. Multicentric osteolysis Nodulosis and arthropathy. 2016 Jul 14 [updated 2021 Sep 9]. In: MP Adam, DB Everman, GM Mirzaa, et al., editors. GeneReviews®. Seattle (WA): University of Washington, Seattle; 1993-2023 Available from: https://www.ncbi.nlm.nih.gov/books/NBK373578/ Google Scholar 2de Vos IJHM, Wong ASW, Welting TJM, Coull BJ, van Steensel MAM. Multicentric osteolytic syndromes represent a phenotypic spectrum defined by defective collagen remodeling. Am J Med Genet A. 2019; 179: 1652–1664. 10.1002/ajmg.a.61264 PubMedGoogle Scholar 3Mandragos E, Myrgiotis D, Strongylos S, Papamerkouriou YM, Michelarakis J. Clinical radiological and molecular profile of a patient affected with multicentric osteolysis Nodulosis and arthropathy. Cureus. 2021; 13:e16615. PubMedGoogle Scholar 4Elsebaie H, Mansour MA, Elsayed SM, Mahmoud S, El-Sobky TA. Multicentric osteolysis, Nodulosis, and arthropathy in two unrelated children with matrix metalloproteinase 2 variants: genetic-skeletal correlations. Bone Rep. 2021; 15:101106. 10.1016/j.bonr.2021.101106 CASPubMedGoogle Scholar Volume66, Issue1January/December 2024e15743 ReferencesRelatedInformation

The outbreak of clade 2.3.4.4b highly pathogenic avian influenza viruses of the H5N1 subtype (HPAI H5N1) in dairy cattle in the USA has so far resulted in spillover infections of at least 14 farm workers1-3, who presented with mild respiratory symptoms or conjunctivitis, and one individual with no known animal exposure who was hospitalized but recovered3,4. Here we characterized A/Texas/37/2024 (huTX37-H5N1), a virus isolated from the eyes of an infected farm worker who developed conjunctivitis5. huTX37-H5N1 replicated efficiently in primary human alveolar epithelial cells, but less efficiently in corneal epithelial cells. Despite causing mild disease in the infected worker, huTX37-H5N1 proved lethal in mice and ferrets and spread systemically, with high titres in both respiratory and non-respiratory organs. Importantly, in four independent experiments in ferrets, huTX37-H5N1 transmitted by respiratory droplets in 17-33% of transmission pairs, and five of six exposed ferrets that became infected died. PB2-631L (encoded by bovine isolates) promoted influenza polymerase activity in human cells, suggesting a role in mammalian adaptation similar to that of PB2-627K (encoded by huTX37-H5N1). In addition, bovine HPAI H5N1 virus was found to be susceptible to polymerase inhibitors both in vitro and in mice. Thus, HPAI H5N1 virus derived from dairy cattle transmits by respiratory droplets in mammals without previous adaptation and causes lethal disease in animal models.

H5N1 avian influenza viruses bearing the clade 2.3.2.1 hemagglutinin (HA) gene have been widely detected in birds and poultry in several countries. During our routine surveillance, we isolated 28 H5N1 viruses between January 2017 and October 2020. To investigate the genetic relationship of the globally circulating H5N1 viruses and the biological properties of those detected in China, we performed a detailed phylogenic analysis of 274 representative H5N1 strains and analyzed the antigenic properties, receptor-binding preference, and virulence in mice of the H5N1 viruses isolated in China. The phylogenic analysis indicated that the HA genes of the 274 viruses belonged to six subclades, namely clades 2.3.2.1a to 2.3.2.1f; these viruses acquired gene mutations and underwent complicated reassortment to form 58 genotypes, with G43 being the dominant genotype detected in eight Asian and African countries. The 28 H5N1 viruses detected in this study carried the HA of clade 2.3.2.1c (two strains), 2.3.2.1d (three strains), or 2.3.2.1f (23 strains), and formed eight genotypes. These viruses were antigenically well-matched with the H5-Re12 vaccine strain used in China. Animal studies showed that the pathogenicity of the H5N1 viruses ranged from non-lethal to highly lethal in mice. Moreover, the viruses exclusively bound to avian-type receptors and have not acquired the ability to bind to human-type receptors. Our study reveals the overall picture of the evolution of clade 2.3.2.1 H5N1 viruses and provides insights into the control of these viruses.

Human infections with the H7N9 influenza virus have been eliminated in China through vaccination of poultry; however, the H7N9 virus has not yet been eradicated from poultry. Carefully analysis of H7N9 viruses in poultry that have sub-optimal immunity may provide a unique opportunity to witness the evolution of highly pathogenic avian influenza virus in the context of vaccination. Between January 2020 and June 2023, we isolated 16 H7N9 viruses from samples we collected during surveillance and samples that were sent to us for disease diagnosis. Genetic analysis indicated that these viruses belonged to a single genotype previously detected in poultry. Antigenic analysis indicated that 12 of the 16 viruses were antigenically close to the H7-Re4 vaccine virus that has been used since January 2022, and the other four viruses showed reduced reactivity with the vaccine. Animal studies indicated that all 16 viruses were nonlethal in mice, and four of six viruses showed reduced virulence in chickens upon intranasally inoculation. Importantly, the H7N9 viruses detected in this study exclusively bound to the avian-type receptors, having lost the capacity to bind to human-type receptors. Our study shows that vaccination slows the evolution of H7N9 virus by preventing its reassortment with other viruses and eliminates a harmful characteristic of H7N9 virus, namely its ability to bind to human-type receptors.

Zoonotic avian influenza viruses have continued to infect people on occasion. During treatment, antiviral resistant viruses have occasionally emerged, highlighting the need for a novel strategy for treating human illness. After pancreatin treatment, edible bird's nest (EBN), swiftlet saliva consumed for health purposes, possesses anti-avian viral activity by inhibiting receptor-binding hemagglutinin (HA) activity. Glycan analysis revealed an abundance of α2,3Neu5Ac decoy receptors in pancreatin-treated EBN. Fucosylated tri-α2,3Neu5Ac tri-antennary N-glycans (N-35) and di-α2,3Neu5Ac core 2 O-glycans (O-15) are predominant, accounting for 53.46% and 44.66% of total N- and O-glycan amounts, respectively. Isobologram analysis revealed that the treated EBN had a strong synergistic effect with either oseltamivir carboxylate or zanamivir, a competitive inhibitor of receptor-destroying neuraminidases (NAs), against the avian H5N1 virus. Taken together, EBN has the potential to be developed as a food-derived avian viral trap to prevent and decrease avian virus infection as well as in combination with a viral releasing-NA inhibitor to increase therapeutic potency, reduce toxicity, delay resistance development, and potentially prevent pandemic onset.

BackgroundTwo human cases of avian influenza A (H3N8) virus infection were reported in China in 2022.AimTo characterise H3N8 viruses circulating in China in September 2021-May 2022.MethodsWe sampled poultry and poultry-related environments in 25 Chinese provinces. After isolating H3N8 viruses, whole genome sequences were obtained for molecular and phylogenetic analyses. The specificity of H3N8 viruses towards human or avian receptors was assessed in vitro. Their ability to replicate in chicken and mice, and to transmit between guinea pigs was also investigated.ResultsIn total, 98 H3N8 avian influenza virus isolates were retrieved from 38,639 samples; genetic analysis of 31 representative isolates revealed 17 genotypes. Viruses belonging to 10 of these genotypes had six internal genes originating from influenza A (H9N2) viruses. These reassorted viruses could be found in live poultry markets and comprised the strains responsible for the two human infections. A subset of nine H3N8 viruses (including six reassorted) that replicated efficiently in mice bound to both avian-type and human-type receptors in vitro. Three reassorted viruses were shed by chickens for up to 9 days, replicating efficiently in their upper respiratory tract. Five reassorted viruses tested on guinea pigs were transmissible among these by respiratory droplets.ConclusionAvian H3N8 viruses with H9N2 virus internal genes, causing two human infections, occurred in live poultry markets in China. The low pathogenicity of H3N8 viruses in poultry allows their continuous circulation with potential for reassortment. Careful monitoring of spill-over infections in humans is important to strengthen early-warning systems and maintain influenza pandemic preparedness.

Personal protective equipment (PPE), including medical masks, should be worn for preventing the transmission of respiratory pathogens via infective droplets and aerosols. In medical masks, the key layer is the filter layer, and the melt-blown nonwoven fabric (NWF) is the most used fabric. However, the NWF filter layer cannot kill or inactivate the pathogens spread via droplets and aerosols. Povidone-iodine (PVP-I) has been used as an antiseptic solution given its potent broad-spectrum activity against pathogens. To develop PPE (e.g., medical masks) with anti-pathogenic activity, we integrated PVP-I into nylon-66 NWF. We then evaluated its antiviral activity against influenza A viruses by examining the viability of Madin-Darby canine kidney (MDCK) cells after inoculation with the virus strains exposed to the PVP-I-integrated nylon-66 NWF. The PVP-I nylon-66 NWF protected the MDCK cells from viral infection in a PVP-I concentration-dependent manner. Subsequently, we found to integrate PVP-I into nylon-66 and polyurethane materials among various materials. These PVP-I materials were also effective against influenza virus infection, and treatment with PVP-I nylon-66 NWF showed the highest cell survival among all the tested materials. PVP-I showed anti-influenza A virus activity when used in conjunction with PPE materials. Moreover, nylon-66 NWF integrated with PVP-I was found to be the best material to ensure anti-influenza activity. Therefore, PVP-I-integrated masks could have the potential to inhibit respiratory virus infection. Our results provide new information for developing multi-functional PPEs with anti-viral activity by integrating them with PVP-I to prevent the potential transmission of respiratory viruses.

Graphene biosensors have the potential to be excellent applications of two-dimensional materials, because graphene has high mobility and specific surface area. However, it is difficult to stably obtain consistent responses from graphene biosensors owing to external disturbances and the lack of understanding their sensing mechanism. We propose a graphene biosensor coated with a gas-permeable silicone elastomer, poly(dimethylsiloxane). The elastomer coating allows only the gas molecules to reach the graphene surface, suppressing the disturbances from other factors, and thereby eliciting stable responses to target ammonia molecules in solution. It allowed us to clarify the relationship between ammonia production via urease reactions and conductivity changes of the graphene biosensor. The biosensor responses were modeled using the combination of the dissociation equilibrium of ammonia, Langmuir's adsorption isotherm, and Michaelis-Menten equation. Findings of this study lay the foundation for practical applications of stable graphene biosensors based on our reasonable response model.

The globally circulating H5N8 avian influenza viruses bearing the clade 2.3.4.4b hemagglutinin (HA) gene are responsible for the loss of more than 33 million domestic poultry since January 2020. Moreover, the H5N8 viruses have reassorted with other avian influenza viruses and formed H5N1, H5N2, H5N3, H5N4, and H5N5 viruses in Europe, Africa, and North America. In this study, we analyzed 15 H5N6 viruses isolated from poultry and seven H5N6 viruses isolated from humans, and found these viruses formed seven different genotypes by deriving the clade 2.3.4.4b HA gene of H5N8 viruses, the neuraminidase of domestic duck H5N6 viruses, and internal genes of different viruses that previously circulated in domestic ducks and wild birds in China. Two of these genotypes (genotype 3 and genotype 6) have caused human infections in multiple provinces. The H5N6 viruses isolated from poultry have distinct pathotypes in mice; some of them replicate systemically and are highly lethal in mice. Although these viruses exclusively bind to avian-type receptors, it is worrisome that they may obtain key mutations that would increase their affinity for human-type receptors during replication in humans. Our study indicates that the novel H5N6 reassortants bearing the clade 2.3.4.4b HA gene of H5N8 viruses were generated through reassortment in domestic ducks and may have spread across a wide area of China, thereby posing a new challenge to the poultry industry and human health. Our findings emphasize the importance of careful monitoring, evaluation, and control of the H5N6 viruses circulating in nature.

Depending on the strain, influenza A virus causes animal, zoonotic, pandemic, or seasonal influenza with varying degrees of severity. Two surface glycoprotein spikes, hemagglutinin (HA) and neuraminidase (NA), are the most important influenza A virus antigens. NA plays an important role in the propagation of influenza virus by removing terminal sialic acid from sialyl decoy receptors and thereby facilitating the release of viruses from traps such as in mucus and on infected cells. Some NA inhibitors have become widely used drugs for treatment of influenza. However, attempts to develop effective and safe NA inhibitors that can be used for treatment of anti-NA drugs-resistant influenza viruses have continued. In this chapter, we describe the following updates on influenza A NA inhibitor development: (i) N-acetylneuraminic acid (Neu5Ac)-based derivatives, (ii) covalent NA inhibitors, (iii) sulfo-sialic acid analogs, (iv) N-acetyl-6-sulfo-β-D-glucosaminide-based inhibitors, (v) inhibitors targeting the 150-loop of group 1 NAs, (vi) conjugation inhibitors, (vii) acylhydrazone derivatives, (viii) monoclonal antibodies, (ix) PVP-I, and (x) natural products. Finally, we provide future perspectives on the next-generation anti-NA drugs.

The large variation of influenza A viruses (IAVs) in various susceptible hosts and their rapid evolution, which allows host/tissue switching, host immune escape, vaccine escape, and drug resistance, are difficult challenges for influenza control in all countries worldwide. Access and binding of the IAV to actual receptors at endocytic sites is critical for the establishment of influenza infection. In this chapter, the progress in identification of and roles of glycans and non-glycans on the epithelium and in the immune system in H1-H18 IAV infections are reviewed. The first part of the review is on current knowledge of H1-H16 IAV receptors on the epithelium including sialyl glycans, other negatively charged glycans, and annexins. The second part of the review focuses on H1-H16 IAV receptors in the immune system including acidic surfactant phospholipids, Sia on surfactant proteins, the carbohydrate recognition domain (CRD) of surfactant proteins, Sia on mucins, Sia and C-type lectins on macrophages and dendritic cells, and Sia on NK cells. The third part of the review is about a possible H17-H18 IAV receptor. Binding of these receptors to IAVs may result in inhibition or enhancement of IAV infection depending on their location, host cell type, and IAV strain. Among these receptors, host sialyl glycans are key determinants of viral hemagglutinin (HA) lectins for H1-H16 infections. HA must acquire mutations to bind to sialyl glycans that are dominant on a new target tissue when switching to a new host for efficient transmission and to bind to long sialyl glycans found in the case of seasonal HAs with multiple glycosylation sites as a consequence of immune evasion. Although sialyl receptors/C-type lectins on immune cells are decoy receptors/pathogen recognition receptors for capturing viral HA lectin/glycans protecting HA antigenic sites, some IAV strains do not escape, such as by release with neuraminidase, but hijack these molecules to gain entry and replication in immune cells. An understanding of the virus-host battle tactics at the receptor level might lead to the establishment of novel strategies for effective control of influenza.

SARS-CoV-2 has evolved continuously and accumulated spike mutations with each variant having a different binding for the cellular ACE2 receptor. It is not known whether the interactions between such mutated spikes and ACE2 glycans are conserved among different variant lineages. Here, we focused on three ACE2 glycosylation sites (53, 90 and 322) that are geometrically close to spike binding sites and investigated the effect of their glycosylation pattern on spike affinity. These glycosylation deletions caused distinct site-specific changes in interactions with the spike and acted cooperatively. Of note, the particular interaction profiles were conserved between the SARS-CoV-2 parental virus and the variants of concern (VOCs) Delta and Omicron. Our study provides insights for a better understanding of the importance of ACE2 glycosylation on ACE2/SARS-CoV-2 spike interaction and guidance for further optimization of soluble ACE2 for therapeutic use.

The antigenic changes that occur continually in the evolution of influenza A viruses remain a great challenge for the effective control of disease outbreaks. Here, we identified three amino acid substitutions (at positions 190, 230, and 269) in the HA of EA H1N1 SIVs that determine viral antigenicity and result in escape from neutralizing monoclonal antibodies.

The continued emergence of human illness caused by avian influenza viruses (AIVs) demonstrates the threat of strains such as H5N1, H7N9, H10N8, and now H10N3. The genetic and biological properties of H10N3 viruses are not fully understood. In this study, three H10N3 strains isolated from live poultry markets (LPMs) were systematically studied. Genome sequencing showed that the poultry-origin viruses are highly homologous to the human H10N3 isolate. The three avian strains were A/chicken/Jiangsu/0146/2021(abbreviated as JS146, H10N3), A/chicken/Jiangsu/0169/2021 (JS169, H10N3), and A/chicken/Jiangsu/0189/2021(JS189, H10N3). Animal studies indicated that all three viruses are highly pathogenic to mice and that all could replicate efficiently in mouse nasal turbinate and lungs despite maintaining their avian receptor binding affinity. We also found that these viruses replicated efficiently in A549 cells and chicken embryos. The strain JS146 had sensitivity to the neuraminidase-targeting drugs oseltamivir and zanamivir, whereas JS169 and JS189 were more resistant; genetic comparison implied that a substitution at NA position 368 conferred drug resistance. Importantly, several key molecular markers associated with mammalian adaptation had been detected in both avian and human-isolated H10N3 influenza viruses in the HA (G228S), PB2 (I292V and A588V), PB1 (M317V and I368V), and PA (A343S, K356R and S409N) protein. The above work contributes new insight into the biology of this potentially zoonotic subtype and provides evidence supporting the continued epidemiological monitoring of human infections caused by AIV subtype H10N3.