ETIDIOH - NEW

  Abstract Stabilizing the pre-fusion structures of antigenic proteins can enhance the effectiveness of antiviral vaccines . The pre-fusion form of hemagglutinin (HA) from the influenza virus typically adopts a stable trimeric structure . However, the recombinant ectodomain of HA from the A/California/04/2009 (H1N1) influenza virus formed a monomer in solution rather than the expected trimer. To promote trimer formation in the pre-fusion conformation, we redesigned five amino acid residues in the stem region of HA that are involved in trimerization. The engineered HA protein formed a stable trimer at both pH 8.0 and pH 5.5. Additionally, the thermal stability of the modified protein improved, as indicated by an approximately ten-degree increase in its denaturation temperature. Cryo-EM analysis at 2.2 angstrom resolution confirmed that the mutant HA protein adopted the pre-fusion structure. Furthermore, the stabilized mutant exhibited enhanced immunogenicity in mice . We applied the...

  Abstract In recent years, the four main swine influenza A virus (IAV-S) subtypes circulating in swine in the EU have been H1avN1, H1huN2, H1N1pdm09, and H3N2 . The latter emerged in 1984 from a reassortment event between a human seasonal H3N2 and H1avN1, and is currently detected at low prevalence in swine in Italy . Here, we describe nine H3N2 IAV-S isolates belonging to three novel genotypes , first detected in Italy in 2021 , likely resulting from reassortment events between swine and human IAVs. The first genotype was characterized by a hemagglutinin (H3 HA) of human seasonal origin , a neuraminidase (N2 NA) derived from H1huN2 strains circulating in Italian swine, and an avian-like internal gene cassette (IGC). The second genotype differed in its IGC constellation: PB2, PB1, PA and NP segments were of pandemic origin ( pdm09 ), while NS and M segments derived from the Eurasian avian-like lineage . The third genotype combined a human-derived H3, a Gent/84-derived N2, and a pd...

  Abstract Influenza A virus (IAV) infection is associated with a wide variety of neurological complications , of which mild complications like impaired cognitive functioning are most prominent . Even though several studies have shown that many influenza viruses can enter the CNS, the neuropathogenesis of seasonal ( H3N2 and H1N1 ) and pandemic (pH1N1 2009) IAV infections is poorly understood. Therefore, we aimed to investigate the cellular tropism, replication efficiency and associated functional consequences using a human stem cell-derived neural co-culture model of neurons and astrocytes . All viruses were able to infect neurons in the co-culture model, although this infection did not result in efficient replication and release of progeny virus. In addition, infection did not result in visible cell death or apoptosis. However, functional analyses revealed that IAV inoculation resulted in a reduction of spontaneous neural activity and a partial reduction of neural excitability. T...

  Highlights -- Higher Mortality in COVID-19 ECMO Patients : COVID-19 patients on ECMO had a significantly higher in-hospital mortality rate (52%) compared to H1N1 patients (6%) (p < 0.0001). -- Increased Complications in COVID-19 : COVID-19 patients had a higher incidence of complications, including: •  Secondary bloodstream infections (OR = 14.3; p = 0.003) •  Neurological complications •  Acute kidney injury requiring renal replacement therapy (RRT) -- Longer ECMO Duration in COVID-19 : COVID-19 patients required longer durations of ECMO support compared to H1N1 patients. -- Age and Comorbidities Impact Mortality : Even after adjusting for age, BMI, gender, and ECMO duration, COVID-19 conferred a 16-fold higher risk of mortality compared to H1N1 (adjusted OR = 16.8). Abstract Background Veno-venous Extracorporeal Membrane Oxygenation (V-V ECMO) in management of refractory respiratory failure due to viral respiratory infections has increased with recent pandemic...

Abstract Background .  Highly pathogenic avian influenza A(H5) viruses pose a pandemic threat , with a history of zoonotic spillovers into humans that are presumed immunologically naive. Whether the general population is currently immunologically naive to circulating A(H5) influenza viruses is unknown.  Methods .  To evaluate the presence of cross-reactive immune responses to emerging A(H5) clade 2.3.4.4b influenza viruses in the general population, we conducted comprehensive immune profiling on cross-sectional samples from healthcare workers (n=107). Samples were collected in August and September 2024 in the scope of an ongoing prospective follow-up study: Surveillance of rEspiratory viruses iN healThcare and anImal workers in the NethErLands (SENTINEL).  Findings .  Low-level antibody responses directed against the A(H5) hemagglutinin (HA) head were detected in a limited number of individuals , but without hemagglutination inhibition activity. Nevertheless, we...

Key Points -- Question: What were the clinical characteristics, management approaches, and outcomes among children with influenza-associated acute necrotizing encephalopathy (ANE) in the US during the 2023-2024 and 2024-2025 influenza seasons? -- Findings:   In this multicenter case series of 41 children from 23 US hospitals , influenza-associated ANE carried a 27% mortality rate despite multimodal therapy. Most patients (76%) had no significant medical history , despite 15 of 32 tested (47%) having genetic risk alleles potentially related to risk of ANE identified during diagnostic evaluation. The H1 2009 influenza A strain predominated (34% of cases), and only 16% had received seasonal influenza vaccination . Among survivors, 63% had moderate to severe disability at 90-day follow-up. -- Meaning:  Influenza-associated ANE represents a rare but devastating neurologic complication primarily affecting previously healthy children. The high morbidity and mortality emphasize t...

Highlights •  High seropositivity in dogs to highly pathogenic avian influenza (HPAI) H5 virus in the Netherlands during HPAI H5 endemicity in wild birds. •  HPAI H5-seropositivity higher in hunting -training dogs than companion dogs.  •  HPAI H5-seropositivity in hunting-training dogs associated with recent bird contact in/near water. •  High seropositivity in dogs to human H1N1pdm2009 influenza A virus (IAV). •  H1N1pdm2009-seropositivity higher in companion dogs than hunting-training dogs. Abstract Dogs are susceptible to the currently circulating highly pathogenic avian influenza (HPAI) H5 and human H1N1pdm2009 (pandemic H1N1) viruses, yet little is known about the extent to which dogs are exposed to both these viruses. Here we investigated HPAI H5 and human H1N1pdm2009 virus exposure in domestic dogs–including dogs that participated in hunting-training– and investigated lifestyle factors associated with HPAI H5 virus exposure. We screened sera from 538...

Editor’s summary The vast majority of the human population has immunity to influenza A virus (IAV) by prior infection, vaccination, or both . However, protection is generally subtype-specific , and it is not clear whether prior infection against one subtype could confer protection against clade 2.3.4.4b H5N1 IAVs , which are currently circulating in birds and dairy cows . Here, Restori et al. demonstrated that prior infection with the 2009 pandemic H1N1 IAV was protective against subsequent direct infection with H5N1 IAV in ferrets. Moreover, prior immunity reduced susceptibility to infection by transmission from an infected donor ferret. These data suggest that prior immunity to IAV, especially to the 2009 pandemic H1N1 virus, may offer a degree of protection against H5N1 infection. —Courtney Malo Abstract Zoonotic infections with emerging influenza viruses occur in the context of population-wide immunity to seasonal strains . Because of the worldwide spread of highly pathogenic clade...

Abstract The H1N1 virus commonly causes symptoms such as fever, cough, sore throat, which have a self-limited course in most cases . Neurological complications are rare, especially in adults. This case illustrates H1N1-associated acute leukoencephalopathy in a young adult with a favorable outcome and no lasting neurological deficits . The initial presentation included fever, sore throat, and myalgia , evolving into neurological symptoms , including dysarthria, nystagmus, and left-sided motor weakness . Comprehensive laboratory tests ruled out common bacterial, viral, or autoimmune causes, while MRI findings suggested acute leukoencephalopathy of infectious or toxic etiology. Although the urine toxicology screen showed traces of phenol , clinical evidence did not correlate with toxic exposure and pointed towards an infectious origin. A throat swab for Influenza/H1N1 PCR confirmed the diagnosis. Treatment with oseltamivir and methylprednisolone led to symptomatic improvement with no sequ...

Abstract The spill-over of Influenza A virus H5N1 clade 2.3.4.4b from cattle to humans highlights the risk of a human H5N1 pandemic . Given the impact of pre-existing immunity on the course and severity of viral infections, we comprehensively assessed the humoral immunity against the H5N1 A/Texas/37/2024 isolate in H5N1- naive individuals . To this end, we performed complementary binding and neutralization assays on 66 subjects and ranked activities among a panel of 76 influenza A virus isolates. We detected low but distinct cross-neutralizing titers against A/Texas/37/2024 with a 3.9 to 15.6-fold reduction compared to selected H1N1 or H3N2 strains. By cloning and evaluating 136 monoclonal antibodies from memory B cells, we identified potent A/Texas/37/2024-neutralizing monoclonal antibodies in five out of six investigated individuals. These antibodies cross-neutralize H1, compete with antibodies targeting the HA stem, and protect mice from lethal H5N1 challenge. Our findings demonstra...

Abstract An increase in the number of human cases of influenza A/H5N1 infection in the US has raised concerns about the pandemic potential of the virus . Preexisting population immunity is a key determinant for risk assessment and pandemic potential for any virus. Antibody responses against the bovine A/H5N1 hemagglutinin (HA) and neuraminidase (NA) proteins were measured among a population of influenza-vaccinated or influenza-infected individuals . Modest titers of bovine A/H5N1 HA-binding antibodies and low to undetectable neutralizing antibody responses were detected in a cohort of 73 individuals . Conversely, bovine A/H5N1 NA binding and neuraminidase-inhibiting antibody responses were comparable to those against a human A/ H1N1 NA at baseline. Seasonal influenza vaccination failed to significantly increase antibody titers against both HA and NA glycoproteins of bovine A/H5N1. Recent infection with human A/H1N1 but not A/H3N2 viruses induced significant increases in bovine A/H5N1 n...

Highlights •  In a landscape of a very narrow arsenal of influenza antivirals, resistance mutations are a significant threat. •  Resistance mutations were present in 0.5-5% in A and B influenza viruses during the last 15 years. •  However, S247N resistance mutation in the NA gene sharply increased during 2023-2024 season. •  While this mutation does not confer strong resistance by itself, their fixation could increase the risk of resistance in the future if other resistance mutations appears or get fixed together with it. Abstract The therapeutic arsenal against influenza is extremely limited and resistance often arises due to the emergence of mutations , especially in the neuraminidase (NA) gene. This study aimed to evaluate the evolution of NA mutations over 15 years in Spain . To do so, we used the GISAID database from which we downloaded a total of 11,125 influenza A(H1N1)pdm09, A(H3N2), B/Victoria and B/Yamagata NA virus sequences , and analyzed the resistance m...

Highlights •  Antiviral susceptibility to NA inhibitors and PA inhibitor baloxavir was determined for seasonal and zoonotic influenza viruses circulating globally during 2020–2023. •  Low global frequencies (0.1-0.2%) of seasonal influenza viruses with reduced or highly reduced inhibition by NAI inhibitors were observed as in previous years. •  Low global frequencies of seasonal influenza viruses (∼ 0.1%) with reduced susceptibility to baloxavir were observed, with the rate in Japan elevated (3.3%) in 2022–2023, as has been seen previously. •  For zoonotic viruses, 2.7% contained genetic markers associated with reduced or highly reduced inhibition to NA inhibitors and none contained markers associated with reduced susceptibility for baloxavir. •  For the treatment of influenza , NA inhibitors and baloxavir remain suitable. ABSTRACT Antiviral susceptibility of influenza viruses is monitored by the World Health Organization Global Influenza Surveillance and Respon...

Abstract Educational farms provide students with hands-on experience in agricultural and animal practices . However, the close contact between humans and farm animals creates a significant interface for zoonotic disease transmission , yet research on infectious diseases in such settings remains limited. This study investigates the ongoing spillovers of human-origin influenza A virus (IAV) into swine at an educational farm in central Chile , describing IAV prevalence, outbreak dynamics, and the genomic characterization of detected strains. The Menesianos educational farm, located in Melipilla, central Chile, houses approximately 40 swine alongside other domestic animals , such as horses and cows . As part of an active IAV surveillance project, monthly nasal swab samples were collected from pigs between June 2019 and September 2023 for IAV detection via RT-qPCR targeting the M gene, with positive samples subsequently sequenced. During the study period, monthly IAV prevalence ranged from ...

ABSTRACT The highly pathogenic avian influenza virus A(H5N1) clade 2.3.4.4b has caused a human outbreak in North America since March 2024. Here, we conducted a serosurveillance study to determine the risk of A(H5N1) clade 2.3.4.4b (2024 cattle H5N1) to general population. In the initial screening of 180 serum specimens encompassing all age groups, 2.2% (4/180) had detectable neutralizing antibody (nAb) titers against reverse genetics-derived 2024 cattle H5N1, with all collected from older adults aged ≥60 years old. Further screening showed that 4.2% (19/450) of adults aged ≥60 years old had detectable nAb titers against the 2024 cattle H5N1 . 80% (4/5) serum specimens with nAb titer of ≥40 had detectable HI titer, and there was a positive correlation between nAb titer and HA binding (r = 0.3325, 95% confidence interval 0.2477 to 0.4123; P < 0.0001). The nAb titer against seasonal H1N1 virus was 4.2-fold higher for ≥60 years old individuals with detectable H5N1 nAb titer than those ≥...

Abstract Influenza A virus poses significant public health challenges , causing seasonal outbreaks and pandemics. Its rapid evolution motivates continuous monitoring of circulating influenza genomes to inform vaccine and antiviral development. Wastewater-based surveillance offers an unbiased, cost-effective approach for genomic surveillance. We developed a novel tiling amplicon primer panel that covers diversity of influenza A virus, targeting segments of the surface proteins HA, NA, and M of subtypes H1N1 and H3N2. Using this panel, we sequenced nucleic acid extracts from 59 Swiss wastewater samples collected at four locations during the 2022/2023 and 2023/2024 winter seasons. We found that wastewater-based abundance estimates of the dominant H1N1 clades correlated with clinical-based estimates in the 2023/2024 season. Furthermore, wastewater-based sequencing revealed mutations in vaccine and drug target sites , consistent with clinical data. Overall, we demonstrate the effectiveness ...

Highlights •  Impact of genetic evolution in influenza A(H1N1)pdm09 on subtyping assay performance. •  Influenza A subtyping assays are susceptible to primer- or probe-binding mismatches. •  Subclades 6B.1 A.5a.2a.1 and 6B.1 A.5a.2a harbour mutations that caused subtyping failures in some specimens. •  Sequencing confirmed all specimens were H1N1pdm09, within recognized subclades. Abstract Background During the 2023–2024 and early 2024–2025 influenza seasons , several influenza A-positive specimens in our laboratory failed subtyping for H1 , H1pdm09, and H3 using the Allplex Respiratory Panel 1 (Allplex RP1) (Seegene Inc.). This study aimed to identify the cause of these subtyping failures. Materials and Methods Between August 2023 and December 2024 , 23 nasopharyngeal specimens tested positive for influenza A but were unsubtypeable for H1, H1pdm09, and H3. Confirmatory testing by the manufacturer included target-specific PCR for the M and HA genes, followed by seque...

Abstract Influenza A(H1N1)pdm09 virus carrying an I38N substitution was detected in an untreated teenager in Japan . The I38N mutant virus exhibited reduced susceptibility to baloxavir but remained susceptible to neuraminidase inhibitors and showed reduced growth capability . Monitoring antiviral drug susceptibility of influenza viruses is necessary to aid public health planning and clinical recommendations. Source: US Centers for Disease Control and Prevention,  https://wwwnc.cdc.gov/eid/article/31/5/24-1123_article ____

Abstract The unprecedented 2.3.4.4b A(H5N1) outbreak in dairy cattle, poultry, and spillover to humans in the United States (US) poses a major public health threat . Population immunity is a critical component of influenza pandemic risk assessment. We conducted a comprehensive assessment of the population immunity to 2.3.4.4b A(H5N1) viruses and analyzed 1794 sera from 723 people (0.5-88 yrs) in multiple US geographic regions during 2021-2024. Low pre-existing neutralizing and hemagglutinin (HA) head binding antibodies and substantial cross reactive binding antibodies to N1 neuraminidase (NA) of 2.3.4.4b A(H5N1) were detected in US population. Antibodies to group 1 HA stalk were also prevalent with an age-related pattern. A( H1N1 )pdm09 infection and influenza vaccination did not induce neutralizing antibodies but induced significant rise of NA inhibition (NAI) antibodies to N1 of 2.3.4.4b A(H5N1), and group 1 HA stalk antibodies. Understanding population susceptibility to novel influe...

ABSTRACT Unexpected outbreaks caused by the H5N1 highly pathogenic avian influenza virus (HPAIV) in dairy cows in the United States (US) have raised significant veterinary and public health concerns . When and how the H5N1 HPAIV was introduced into dairy cows and the broader epidemiology of influenza A virus (IAV) infections in cattle in the US remain unclear. Herein, we performed a retrospective study to screen more than 1,700 cattle serum samples collected from different bovine breeds in the US from January 2023 to May 2024 using an enzyme-linked immunosorbent assay (ELISA) targeting the nucleoprotein (NP) to detect IAV infections, and the positive samples were further tested by hemagglutination inhibition (HI) assay . Results showed that 586 of 1,724 samples (33.99%) from 15 US states were seropositive by the NP ELISA assay , including 78 samples collected in 2024 and 508 samples collected in 2023 . Moreover, the HI assay revealed that 45 of these ELISA-positive samples were positiv...