Pathogenicity and transmission of novel highly pathogenic H7N2 variants originating from H7N9 avian influenza viruses in chickens.

The H7 subtype avian influenza viruses are circulating widely worldwide, causing significant economic losses to the poultry industry and posing a serious threat to human health. In 2019, H7N2 and H7N9 co-circulated in Chinese poultry, yet the risk of H7N2 remained unclear. We isolated and sequenced four H7N2 viruses from chickens, revealing them as novel reassortants with H7N9-derived HA, M, NS genes and H9N2-derived PB2, PB1, PA,NP, NA genes. To further explore the key segment of pathogenicity, H7N2-H7N9NA and H7N2-H9N2HA single-substitution were constructed. Pathogenicity study showed H7N2 isolates to be highly pathogenic in chickens, with H7N2-H7N9NA slightly weaker than H7N2-Wild type. Transcriptomic analysis suggested that H7N9-derived HA genes primarily drove the high pathogenicity of H7N2 isolates, eliciting a strong inflammatory response. These findings underscored the increased threat posed by reassorted H7N2 viruses to chickens, emphasizing the necessity of long-term monitoring of H7 subtype avian influenza viruses.

Noninvasive serum N-glycans associated with ovarian cancer diagnosis and precancerous lesion prediction.

BACKGROUND: Ovarian cancer (OC) is one of the most common gynecological tumors with high morbidity and mortality. Altered serum N-glycome has been observed in many diseases, while the association between serum protein N-glycosylation and OC progression remains unclear, particularly for the onset of carcinogenesis from benign neoplasms to cancer. METHODS: Herein, a mass spectrometry based high-throughput technique was applied to characterize serum N-glycome profile in individuals with healthy controls, benign neoplasms and different stages of OC. To elucidate the alterations of glycan features in OC progression, an orthogonal strategy with lectin-based ELISA was performed. RESULTS: It was observed that the initiation and development of OC was associated with increased high-mannosylationand agalactosylation, concurrently with decreased total sialylation of serum, each of which gained at least moderately accurate merits. The most important individual N-glycans in each glycan group was H7N2, H3N5 and H5N4S2F1, respectively. Notably, serum N-glycome could be used to accurately discriminate OC patients from benign cohorts, with a comparable or even higher diagnostic score compared to CA125 and HE4. Furthermore, bioinformatics analysis based discriminative model verified the diagnostic performance of serum N-glycome for OC in two independent sets. CONCLUSIONS: These findings demonstrated the great potential of serum N-glycome for OC diagnosis and precancerous lesion prediction, paving a new way for OC screening and monitoring.

Avian influenza A virus H7N9 in China, a role reversal from reassortment receptor to the donator.

Reassortment can introduce one or more gene segments of influenza A viruses (IAVs) into another, resulting in novel subtypes. Since 2013, a new outbreak of human highly pathogenic avian influenza has emerged in the Yangtze River Delta (YRD) and South-Central regions of China. In this study, using Anhui province as an example, we discuss the possible impact of H7N9 IAVs on future influenza epidemics through a series of gene reassortment events. Sixty-one human H7N9 isolates were obtained from five outbreaks in Anhui province from 2013 to 2019. Bioinformatics analyses revealed that all of them were characterized by low pathogenicity and high human or mammalian tropism and had introduced novel avian influenza A virus (AIV) subtypes such as H7N2, H7N6, H9N9, H5N6, H6N6, and H10N6 through gene reassortment. In reassortment events, Anhui isolates may donate one or more segments of HA, NA, and the six internal protein-coding genes for the novel subtype AIVs. Our study revealed that H7N9, H9N2, and H5N1 can serve as stable and persistent gene pools for AIVs in the YRD and South-Central regions of China. Novel AIV subtypes might be generated continuously by reassortment. These AIVs may have obtained human-type receptor-binding abilities from their donors and prefer binding to them, which can cause human epidemics through accidental spillover infections. Facing the continual threat of emerging avian influenza, constant monitoring of AIVs should be conducted closely for agricultural and public health.

Antigenic Architecture of the H7N2 Influenza Virus Hemagglutinin Belonging to the North American Lineage.

The North American low pathogenic H7N2 avian influenza A viruses, which lack the 220-loop in the hemagglutinin (HA), possess dual receptor specificity for avian- and human-like receptors. The purpose of this work was to determine which amino acid substitutions in HA affect viral antigenic and phenotypic properties that may be important for virus evolution. By obtaining escape mutants under the immune pressure of treatment with monoclonal antibodies, antigenically important amino acids were determined to be at positions 125, 135, 157, 160, 198, 200, and 275 (H3 numbering). These positions, except 125 and 275, surround the receptor binding site. The substitutions A135S and A135T led to the appearance of an N-glycosylation site at 133N, which reduced affinity for the avian-like receptor analog and weakened binding with tested monoclonal antibodies. Additionally, the A135S substitution is associated with the adaptation of avian viruses to mammals (cat, human, or mouse). The mutation A160V decreased virulence in mice and increased affinity for the human-type receptor analog. Conversely, substitution G198E, in combination with 157N or 160E, displayed reduced affinity for the human-type receptor analog.

Adaptation of the H7N2 Feline Influenza Virus to Human Respiratory Cell Culture.

During 2016-2017, the H7N2 feline influenza virus infected more than 500 cats in animal shelters in New York, USA. A veterinarian who had treated the cats became infected with this feline virus and showed mild respiratory symptoms. This suggests that the H7N2 feline influenza virus may evolve into a novel pandemic virus with a high pathogenicity and transmissibility as a result of mutations in humans. In this study, to gain insight into the molecular basis of the transmission of the feline virus to humans, we selected mutant viruses with enhanced growth in human respiratory A549 cells via successive passages of the virus and found almost all mutations to be in the envelope glycoproteins, such as hemagglutinin (HA) and neuraminidase (NA). The reverse genetics approach revealed that the HA mutations, HA1-H16Q, HA2-I47T, or HA2-Y119H, in the stalk region can lead to a high growth of mutant viruses in A549 cells, possibly by changing the pH threshold for membrane fusion. Furthermore, NA mutation, I28S/L, or three-amino-acid deletion in the transmembrane region can enhance viral growth in A549 cells, possibly by changing the HA-NA functional balance. These findings suggest that the H7N2 feline influenza virus has the potential to become a human pathogen by adapting to human respiratory cells, owing to the synergistic biological effect of the mutations in its envelope glycoproteins.

Emerging Respiratory Viruses of Cats.

In recent years, advances in diagnostics and deep sequencing technologies have led to the identification and characterization of novel viruses in cats as protoparviruses and chaphamaparvoviruses, unveiling the diversity of the feline virome in the respiratory tract. Observational, epidemiological and experimental data are necessary to demonstrate firmly if some viruses are able to cause disease, as this information may be confounded by virus- or host-related factors. Also, in recent years, researchers were able to monitor multiple examples of transmission to felids of viruses with high pathogenic potential, such as the influenza virus strains H5N1, H1N1, H7N2, H5N6 and H3N2, and in the late 2019, the human hypervirulent coronavirus SARS-CoV-2. These findings suggest that the study of viral infections always requires a multi-disciplinary approach inspired by the One Health vision. By reviewing the literature, we provide herewith an update on the emerging viruses identified in cats and their potential association with respiratory disease.

High-sensitivity detection of two H7 subtypes of avian influenza viruses (AIVs) by immunochromatographic assay with highly chromatic red silica nanoparticles.

In this work, a sensitive and quantitative immunochromatographic assay (ICA) detection method for avian influenza viruses (AIVs) of the H7 hemagglutinin (HA) antigen was established based on highly chromatic red silica nanoparticles (SiNPs). It can detect two H7 subtypes of influenza viruses, H7N2 and H7N9. The highly chromatic red SiNPs were prepared by adsorbing C.I. Direct Red 224 on the surface of the SiNPs for multiple times using the layer by layer (LbL) self-assembly method under the electrostatic action of ethylene imine polymer (PEI) and poly(sodium-p-styrenesulfonate) (PSS). The highly chromatic red silica nanoparticles modified with anti-H7 HA mAb1 were used as immunodetection probes. The accumulated highly chromatic red SiNPs on the T-line can be observed by the naked eye to qualitatively detect the H7 HA antigen. The quantitative analysis is carried out by using a camera and Image J software. Within the range of 0.1-10 ng mL-1, the linear equation between the H7 HA antigen concentration and the peak area of the T-line gray value was y = 868.9722 + 435.4836X (R2 = 0.9716), and the limit of detection (LOD) of this method was 0.08 pg mL-1 (S/N = 3). The highly chromatic red SiNP based ICA for the detection of H7 HA has no cross activity with other subtypes of influenza viruses. This method of combining highly chromatic colored markers with ICA has great potential in practical applications for the rapid and quantitative detection of other types of AIVs.

Canine and Feline Influenza.

Influenza virus infections of carnivores-primarily in dogs and in large and small cats-have been repeatedly observed to be caused by a number of direct spillovers of avian viruses or in infections by human or swine viruses. In addition, there have also been prolonged epizootics of an H3N8 equine influenza virus in dogs starting around 1999, of an H3N2 avian influenza virus in domestic dog populations in Asia and in the United States that started around 2004, and an outbreak of an avian H7N2 influenza virus among cats in an animal shelter in the United States in 2016. The impact of influenza viruses in domesticated companion animals and their zoonotic or panzootic potential poses significant questions for veterinary and human health.

Selection and antigenic characterization of immune-escape mutants of H7N2 low pathogenic avian influenza virus using homologous polyclonal sera.

Understanding the dynamics of the selection of influenza A immune escape variants by serum antibody is critical for designing effective vaccination programs for animals, especially poultry where large populations have a short generation time and may be vaccinated with high frequency. In this report, immune-escape mutants of A/turkey/New York/4450/1994 H7N2 low pathogenic avian influenza virus, were selected by serially passaging the virus in the presence of continuously increasing concentrations of homologous chicken polyclonal sera. Amino acid mutations were identified by sequencing the parental hemagglutinin (HA) gene and every 10 passages by both Sanger and deep sequencing, and the antigenic distance of the mutants to the parent strain was determined. Progressively, a total of five amino acid mutations were observed over the course of 30 passages. Based on their absence from the parental virus with deep sequencing, the mutations appear to have developed de novo. The antigenic distance between the selected mutants and the parent strain increased as the number of amino acid mutations accumulated and the concentration of antibodies had to be periodically increased to maintain the same reduction in virus titer during selection. This selection system demonstrates how H7 avian influenza viruses behave under selection with homologous sera, and provides a glimpse of their evolutionary dynamics, which can be applied to developing vaccination programs that maximize the effectiveness of a vaccine over time.

Identification of novel influenza A virus exposures by an improved high-throughput multiplex MAGPIX platform and serum adsorption.

BACKGROUND: The development of serologic assays that can rapidly assess human exposure to novel influenza viruses remains a public health need. Previously, we developed an 11-plex magnetic fluorescence microsphere immunoassay (MAGPIX) by using globular head domain recombinant hemagglutinins (rHAs) with serum adsorption using two ectodomain rHAs. METHODS: We compared sera collected from two cohorts with novel influenza exposures: animal shelter staff during an A(H7N2) outbreak in New York City in 2016-2017 (n = 119 single sera) and poultry workers from a live bird market in Bangladesh in 2012-2014 (n = 29 pairs). Sera were analyzed by microneutralization (MN) assay and a 20-plex MAGPIX assay with rHAs from 19 influenza strains (11 subtypes) combined with serum adsorption using 8 rHAs from A(H1N1) and A(H3N2) viruses. Antibody responses were analyzed to determine the novel influenza virus exposure. RESULTS: Among persons with novel influenza virus exposures, the median fluorescence intensity (MFI) against the novel rHA from exposed influenza virus had the highest correlation with MN titers to the same viruses and could be confirmed by removal of cross-reactivity from seasonal H1/H3 rHAs following serum adsorption. Interestingly, in persons with exposures to novel influenza viruses, age and MFIs against exposed novel HA were negatively correlated, whereas in persons without exposure to novel influenza viruses, age and MFI against novel HAs were positively correlated. CONCLUSIONS: This 20-plex high-throughput assay with serum adsorption will be a useful tool to detect novel influenza virus infections during influenza outbreak investigations and surveillance, especially when well-paired serum samples are not available.

Differential Modulation of Innate Immune Responses in Human Primary Cells by Influenza A Viruses Carrying Human or Avian Nonstructural Protein 1.

The influenza A virus (IAV) nonstructural protein 1 (NS1) contributes to disease pathogenesis through the inhibition of host innate immune responses. Dendritic cells (DCs) release interferons (IFNs) and proinflammatory cytokines and promote adaptive immunity upon viral infection. In order to characterize the strain-specific effects of IAV NS1 on human DC activation, we infected human DCs with a panel of recombinant viruses with the same backbone (A/Puerto Rico/08/1934) expressing different NS1 proteins from human and avian origin. We found that these viruses induced a clearly distinct phenotype in DCs. Specifically, viruses expressing NS1 from human IAV (either H1N1 or H3N2) induced higher levels of expression of type I (IFN-α and IFN-ß) and type III (IFN-λ1 to IFNλ3) IFNs than viruses expressing avian IAV NS1 proteins (H5N1, H7N9, and H7N2), but the differences observed in the expression levels of proinflammatory cytokines like tumor necrosis factor alpha (TNF-α) or interleukin-6 (IL-6) were not significant. In addition, using imaging flow cytometry, we found that human and avian NS1 proteins segregate based on their subcellular trafficking dynamics, which might be associated with the different innate immune profile induced in DCs by viruses expressing those NS1 proteins. Innate immune responses induced by our panel of IAV recombinant viruses were also characterized in normal human bronchial epithelial cells, and the results were consistent with those in DCs. Altogether, our results reveal an increased ability of NS1 from avian viruses to antagonize innate immune responses in human primary cells compared to the ability of NS1 from human viruses, which could contribute to the severe disease induced by avian IAV in humans.IMPORTANCE Influenza A viruses (IAVs) cause seasonal epidemics which result in an important health and economic burden. Wild aquatic birds are the natural host of IAV. However, IAV can infect diverse hosts, including humans, domestic poultry, pigs, and others. IAVs circulating in animals occasionally cross the species barrier, infecting humans, which results in mild to very severe disease. In some cases, these viruses can acquire the ability to be transmitted among humans and initiate a pandemic. The nonstructural 1 (NS1) protein of IAV is an important antagonist of the innate immune response. In this study, using recombinant viruses and primary human cells, we show that NS1 proteins from human and avian hosts show intrinsic differences in the modulation of the innate immunity in human dendritic cells and epithelial cells, as well as different cellular localization dynamics in infected cells.

Influenza A virus infection induces liver injury in mice.

Respiratory infections such as SARS-CoV in humans are often accompanied by mild and self-limiting hepatitis. As a respiratory disease, influenza A virus (IAV) infection can lead to hepatitis, but the mechanism remains unclear. This study aimed to investigate the occurrence of hepatitis by establishing a model for infected mice for three different subtypes of respiratory IAVs (H1N1, H5N1, and H7N2). Histological analysis was performed, and results showed increase serum aminotransferase (ALT and AST) levels and evident liver injury on days 3 and 7, especially on day 5 post infection. Immunohistochemistry (IHC) results indicated a wide distribution of IAV's positive signals in the liver of infected mice. Real-time PCR results further revealed a similar viral titer to IHC that presented a remarkedly positive correlation with histology injury. All these data showed that the mouse model suitably contributed valuable information about the mechanism underlying the occurrence of hepatitis induced by respiratory influenza virus.

Pathogenicity and Transmissibility of North American H7 Low Pathogenic Avian Influenza Viruses in Chickens and Turkeys.

Low pathogenic avian influenza (LPAI) viruses can silently circulate in poultry and wild aquatic birds and potentially mutate into highly pathogenic avian influenza (HPAI) viruses. In the U.S., recent emergence and spread of H7N8 and H7N9 HPAI viruses not only caused devastating losses to domestic poultry but also underscored the capability of LPAI viruses to mutate into HPAI viruses. Therefore, in this study, we evaluated pathogenicity and transmissibility of H7N8 and H7N9 LPAI viruses (the progenitors of HPAI viruses) in chickens and turkeys. We also included H7N2 isolated from an outbreak of LPAI in commercial chickens. H7 viruses replicated more efficiently in the respiratory tract than in the gastrointestinal tract, suggesting that their replication is restricted to the upper respiratory tract. Specifically, H7N2 replicated most efficiently in two-week-old chickens and turkeys. In contrast, H7N8 replicated least efficiently in those birds. Further, replication of H7N2 and H7N9 was restricted in the upper respiratory tract of four-week-old specific-pathogen-free (SPF) and broiler chickens. Despite their restricted replication, the two viruses efficiently transmitted from infected to naïve birds by direct contact, leading to seroconversion of contacted chickens. Our findings suggest the importance of continuous monitoring and surveillance of LPAI viruses in the fields.

Heterosubtypic protection against avian influenza virus by live attenuated and chimeric norovirus P-particle-M2e vaccines in chickens.

Avian influenza in poultry continues to be a great concern worldwide, and the currently licensed inactivated influenza vaccines are not effective against the novel strains of influenza virus that continue to emerge in the field. This warrants the development of more broadly protective influenza vaccines or vaccination regimens. Live attenuated influenza vaccines (LAIVs) and subunit vaccines derived from viral peptides, such as the highly conserved ectodomain of influenza virus matrix protein 2 (M2e), can offer a more broadly reactive immune response. In chickens, we previously showed that a chimeric norovirus P particle containing M2e (M2eP) could provide partial but broad immunity, when administered as a standalone vaccine, and also enhanced the protective efficacy of inactivated vaccine when used in a combination regimen. We also demonstrated that a naturally-selected NS1-truncated H7N3 LAIV (pc4-LAIV) was highly efficacious against antigenically distant heterologous H7N2 low pathogenicity avian influenza virus challenge, especially when used as the priming vaccine in a prime-boost vaccination regimen. In this study, we investigated the cross-subtype protective efficacy of pc4-LAIV in conjunction with M2eP using single vaccination, combined treatment, and prime-boost approaches. Chickens vaccinated with pc4-LAIV showed significant reduction of tracheal shedding of a low pathogenicity H5N2 challenge virus. This cross-subtype protective efficacy was further enhanced, during the initial stages of challenge virus replication, in chickens that received a vaccination regimen consisting of priming with pc4-LAIV at 1 day of age and boosting with M2eP. Further, H5N2-specific serum IgG and pc4-LAIV-specific hemagglutination-inhibition antibody titers were enhanced in LAIV-primed and M2eP boost-vaccinated chickens. Taken together, our data point to the need of further investigation into the benefits of combined and prime-boost vaccination schemes utilizing LAIV and epitope-based vaccines, to develop more broadly protective vaccination regimens.

Detection of Avian Influenza A(H7N2) Virus Infection Among Animal Shelter Workers Using a Novel Serological Approach-New York City, 2016-2017.

BACKGROUND: In 2016, an influenza A(H7N2) virus outbreak occurred in cats in New York City's municipal animal shelters. One human infection was initially detected. METHODS: We conducted a serological survey using a novel approach to rule out cross-reactive antibodies to other seasonal influenza viruses to determine whether additional A(H7N2) human infections had occurred and to assess exposure risk. RESULTS: Of 121 shelter workers, one had serological evidence of A(H7N2) infection, corresponding to a seroprevalence of 0.8% (95% confidence interval, .02%-4.5%). Five persons exhibited low positive titers to A(H7N2) virus, indicating possible infection; however, we could not exclude cross-reactive antibody responses to seasonal influenza viruses. The remaining 115 persons were seronegative. The seropositive person reported multiple direct cat exposures without using personal protective equipment and mild illness with subjective fever, runny nose, and sore throat. CONCLUSIONS: We identified a second case of A(H7N2) infection from this outbreak, providing further evidence of cat-to-human transmission of A(H7N2) virus.

H5N1 Influenza a Virus Replicates Productively in Pancreatic Cells and Induces Apoptosis and Pro-Inflammatory Cytokine Response.

The inflammatory response and apoptosis have been proved to have a crucial role in the pathogenesis of the influenza A virus (IAV). Previous studies indicated that while IAV commonly causes pancreatitis and pancreatic damage in naturally and experimentally infected animals, the molecular mechanisms of the pathogenesis of IAV infection are less reported. In the present study, we showed for the first time that both avian-like (α-2,3-linked) and human-like (α-2,6-linked) sialic acid (SA) receptors were expressed by the mouse pancreatic cancer cell line PAN02 and the human pancreatic cancer cell line PANC-1. Using growth kinetics experiments, we also showed that PAN02 and PANC-1 cells supported the productive replication of the H5N1 highly pathogenic avian influenza while exhibited the limited replication of IAV subtypes H1N1 and H7N2 in vitro. The in vivo infection of H5N1 in pancreatic cells was confirmed by the histopathological and immunohistochemical staining of pancreas tissue from mice. Other than H1N1 and H7N2, severe damage and extensive positive signals were observed in pancreas of H5N1 infected mice. All three virus subtypes induced apoptosis but also triggered the infected PAN02 and PANC-1 cells to release pro-inflammatory cytokines and chemokines including interferon (IFN)-α, IFN-ß, IFN-γ, chemokine (C-C motif) ligand 2 (CCL2), tumor necrosis factor (TNF)-α, and interleukin (IL)-6. Notably, the subtypes of H5N1 could significantly upregulate these cytokines and chemokines in both two cells when compared with H1N1 and H7N2. The present data provide further understanding of the pathogenesis of H5N1 IAV in pancreatic cells derived from humans and mammals and may also benefit the development of new treatment against H5N1 influenza virus infection.

Lethal influenza A virus preferentially activates TLR3 and triggers a severe inflammatory response.

The "cytokine storm" and excessive inflammation triggered by lethal avian influenza virus (IAV) are responsible for its high virulence and mortality. However, the molecular mechanism behind these effects is unclear. In this study, we used LA795 cells and a mouse model to assess the crucial role of TLR3 during infection with lethal avian influenza A virus and subsequent inflammation. The results showed that IAVs could replicate and proliferate well in LA795 cells and that the replication of H5N1 was more efficient than human H1N1 and lowly pathogenic avian H7N2 viruses. The TLR3 signaling pathways were activated preferentially in vitro and in vivo and a range of pro-inflammatory cytokines were released following H5N1 infection. RNAi and TLR3 knockout mice were used to validate the results. These results are the first to provide insight into the preferential involvement of TLR3 in lethal avian influenza A virus infection and inflammation compared with others such as human or lowly pathogenic avian influenza A viruses. The data will increase understanding of the pathogenesis of lethal avian influenza A virus infection and may help facilitate the development of novel therapeutic aids targeting TLR3 signaling pathways.

Differentiated human airway organoids to assess infectivity of emerging influenza virus.

Novel reassortant avian influenza H7N9 virus and pandemic 2009 H1N1 (H1N1pdm) virus cause human infections, while avian H7N2 and swine H1N1 virus mainly infect birds and pigs, respectively. There is no robust in vitro model for assessing the infectivity of emerging viruses in humans. Based on a recently established method, we generated long-term expanding 3D human airway organoids which accommodate four types of airway epithelial cells: ciliated, goblet, club, and basal cells. We report differentiation conditions which increase ciliated cell numbers to a nearly physiological level with synchronously beating cilia readily discernible in every organoid. In addition, the differentiation conditions induce elevated levels of serine proteases, which are essential for productive infection of human influenza viruses and low-pathogenic avian influenza viruses. We also established improved 2D monolayer culture conditions for the differentiated airway organoids. To demonstrate the ability of differentiated airway organoids to identify human-infective virus, 3D and 2D differentiated airway organoids are applied to evaluate two pairs of viruses with known distinct infectivity in humans, H7N9/Ah versus H7N2 and H1N1pdm versus an H1N1 strain isolated from swine (H1N1sw). The human-infective H7N9/Ah virus replicated more robustly than the poorly human-infective H7N2 virus; the highly human-infective H1N1pdm virus replicated to a higher titer than the counterpart H1N1sw. Collectively, we developed differentiated human airway organoids which can morphologically and functionally simulate human airway epithelium. These differentiated airway organoids can be applied for rapid assessment of the infectivity of emerging respiratory viruses to human.