Characterization of a novel reassortant influenza A virus (H2N2) from a domestic duck in Eastern China

Dual receptor-binding, infectivity, and transmissibility of an emerging H2N2 low pathogenicity avian influenza virus

The 1957 H2N2 influenza pandemic virus [A(H2N2)pdm1957] has disappeared from humans since 1968, while H2N2 avian influenza viruses (AIVs) are still circulating in birds. It is necessary to reveal the recurrence risk and potential cross-species infection of these AIVs from avian to mammals. We find that H2 AIVs circulating in domestic poultry in China have genetic and antigenic differences compared to the A(H2N2)pdm1957. One H2N2 AIV has a dual receptor-binding property similar to that of the A(H2N2)pdm1957. Molecular and structural studies reveal that the N144S, and N144E or R137M substitutions in hemagglutinin (HA) enable H2N2 avian or human viruses to bind or preferentially bind human-type receptor. The H2N2 AIV rapidly adapts to mice (female) and acquires mammalian-adapted mutations that facilitated transmission in guinea pigs and ferrets (female). These findings on the receptor-binding, infectivity, transmission, and mammalian-adaptation characteristics of H2N2 AIVs provide a reference for early-warning and prevention for this subtype.

Adenoviral-Vectored Centralized Consensus Hemagglutinin Vaccine Provides Broad Protection against H2 Influenza a Virus

Several influenza pandemics have occurred in the past century, one of which emerged in 1957 from a zoonotic transmission of H2N2 from an avian reservoir into humans. This pandemic caused 2–4 million deaths and circulated until 1968. Since the disappearance of H2N2 from human populations, there has been waning immunity against H2, and this subtype is not currently incorporated into seasonal vaccines. However, H2 influenza remains a pandemic threat due to consistent circulation in avian reservoirs. Here, we describe a method of pandemic preparedness by creating an adenoviral-vectored centralized consensus vaccine design against human H2 influenza. We also assessed the utility of serotype-switching to enhance the protective immune responses seen with homologous prime-boosting strategies. Immunization with an H2 centralized consensus showed a wide breadth of antibody responses after vaccination, protection against challenge with a divergent human H2 strain, and significantly reduced viral load in the lungs after challenge. Further, serotype switching between two species C adenoviruses enhanced protective antibody titers after heterologous boosting. These data support the notion that an adenoviral-vectored H2 centralized consensus vaccine has the ability to provide broadly cross-reactive immune responses to protect against divergent strains of H2 influenza and prepare for a possible pandemic.

Isolation and Selection of Duck Primary Cells as Pathogenic and Innate Immunologic Cell Models for Duck Plague Virus

Duck plague virus (DPV) is a representative pathogen transmitted among aquatic animals that causes gross lesions and immune inhibition in geese and ducks. The mechanism of organ tropism and innate immune evasion of DPV has not been completely deciphered due to a lack of cell models to study the innate immune manipulation and pathogenicity of aquatic viruses. In the present study, we isolated five types of duck primary cells [duck embryo fibroblasts (DEFs), neurons, astrocytes, peripheral blood mononuclear cells (PBMCs), and monocytes/macrophages] to identify appropriate cell models for DPV, using tropism infection and innate immunologic assays. Cells responded differently to stimulation with DNA viruses or RNA virus analogs. DPV infection exhibited broad tropism, as the recombinant virulent strain (CHv-GFP) infected DEFs, neurons, astrocytes, and monocytes/macrophages, but not the PBMCs, as the expression of EGFP was negligible. The basal levels of innate immunity molecules were highest in monocytes/macrophages and lower in DEFs and astrocytes. Conversely, the titer and genomic copy number of the attenuated virus strain was higher in DEFs and astrocytes than in neurons and monocytes/macrophages. The titer and genomic copy number of the attenuated virus strain were higher compared with the virulent strain in DEFs, neurons, and astrocytes. The innate immune response was not significantly induced by either DPV strain in DEFs, neurons, or astrocytes. The virulent strain persistently infected monocytes/macrophages, but the attenuated strain did so abortively, and this was accompanied by the phenomenon of innate immune inhibition and activation by the virulent and attenuated strains, respectively. Blockage of IFNAR signaling promoted replication of the attenuated strain. Pre-activation of IFNAR signaling inhibited infection by the virulent strain. The selection assay results indicated that induction of innate immunity plays an essential role in controlling DPV infection, and monocytes/macrophages are an important cell model for further investigations. Our study provided practical methods for isolating and culturing duck primary cells, and our results will facilitate further investigations of organ tropism, innate immune responses, latent infection, and the effectiveness of antiviral drugs for treating DPV and potentially other aerial bird pathogens.

H2 influenza viruses: designing vaccines against future H2 pandemics

Influenza-related pathologies affect millions of people each year and the impact of influenza on the global economy and in our everyday lives has been well documented. Influenza viruses not only infect humans but also are zoonotic pathogens that infect various avian and mammalian species, which serve as viral reservoirs. While there are several strains of influenza currently circulating in animal species, H2 influenza viruses have a unique history and are of particular concern. The 1957 'Asian Flu' pandemic was caused by H2N2 influenza viruses and circulated among humans from 1957 to 1968 before it was replaced by viruses of the H3N2 subtype. This review focuses on avian influenza viruses of the H2 subtype and the role these viruses play in human infections. H2 influenza viral infections in humans would present a unique challenge to medical and scientific researchers. Much of the world's population lacks any pre-existing immunity to the H2N2 viruses that circulated 50-60 years ago. If viruses of this subtype began circulating in the human population again, the majority of people alive today would have no immunity to H2 influenza viruses. Since H2N2 influenza viruses have effectively circulated in people in the past, there is a need for additional research to characterize currently circulating H2 influenza viruses. There is also a need to stockpile vaccines that are effective against both historical H2 laboratory isolates and H2 viruses currently circulating in birds to protect against a future pandemic.

Characterization of avian influenza H9N2 viruses isolated from ostriches (Struthio camelus)

H9N2 subtype avian influenza viruses (AIVs) have been isolated from various species of wild birds and domestic poultry in the world, and occasionally transmitted to humans. Although H9N2 AIVs are seldom isolated from ostriches, seven such strains were isolated from sick ostriches in China between 2013 and 2014. Sequence analysis showed several amino acid changes relating to viral adaptation in mammals were identified. The phylogenetic analyses indicated that these isolates were quadruple reassortant viruses, which are different from the early ostrich isolates from South Africa or Israel. Most of the ostrich virus carried a human-type receptor-binding property. The chicken experiments showed the ostrich strains displayed low pathogenicity, while they could cause mild to severe symptoms in chicken. Theses strains could efficiently transmit among chickens, and one strain showed higher transmissibility. The virus could not kill mice, and merely replicated in the lung of mice. The ostrich strains could not efficiently transmit between guinea pigs in the direct contact model. These results suggested we should pay attention to the interface between ostrich and other domestic fowl, and keep an eye on this population when monitoring of influenza virus.

In Vitro Neutralization Is Not Predictive of Prophylactic Efficacy of Broadly Neutralizing Monoclonal Antibodies CR6261 and CR9114 against Lethal H2 Influenza Virus Challenge in Mice

Influenza viruses of the H1N1, H2N2, and H3N2 subtypes have caused previous pandemics. H2 influenza viruses represent a pandemic threat due to continued circulation in wild birds and limited immunity in the human population. In the event of a pandemic, antiviral agents are the mainstay for treatment, but broadly neutralizing antibodies (bNAbs) may be a viable alternative for short-term prophylaxis or treatment. The hemagglutinin stem binding bNAbs CR6261 and CR9114 have been shown to protect mice from severe disease following challenge with H1N1 and H5N1 and with H1N1, H3N2, and influenza B viruses, respectively. Early studies with CR6261 and CR9114 showed weak in vitro activity against human H2 influenza viruses, but the in vivo efficacy against H2 viruses is unknown. Therefore, we evaluated these antibodies against human- and animal-origin H2 viruses A/Ann Arbor/6/1960 (H2N2) (AA60) and A/swine/MO/4296424/06 (H2N3) (Sw06). In vitro, CR6261 neutralized both H2 viruses, while CR9114 only neutralized Sw06. To evaluate prophylactic efficacy, mice were given CR6261 or CR9114 and intranasally challenged 24 h later with lethal doses of AA60 or Sw06. Both antibodies reduced mortality, weight loss, airway inflammation, and pulmonary viral load. Using engineered bNAb variants, antibody-mediated cell cytotoxicity reporter assays, and Fcγ receptor-deficient (Fcer1g^-/-) mice, we show that the in vivo efficacy of CR9114 against AA60 is mediated by Fcγ receptor-dependent mechanisms. Collectively, these findings demonstrate the in vivo efficacy of CR6261 and CR9114 against H2 viruses and emphasize the need for in vivo evaluation of bNAbs.IMPORTANCE bNAbs represent a strategy to prevent or treat infection by a wide range of influenza viruses. The evaluation of these antibodies against H2 viruses is important because H2 viruses caused a pandemic in 1957 and could cross into humans again. We demonstrate that CR6261 and CR9114 are effective against infection with H2 viruses of both human and animal origin in mice, despite the finding that CR9114 did not display in vitro neutralizing activity against the human H2 virus. These findings emphasize the importance of in vivo evaluation and testing of bNAbs.

Serological and virological surveillance of avian influenza virus in domestic ducks of the north-east region of Bangladesh

Background

Wild waterfowl are considered as the natural reservoir for avian influenza (AI) viruses. Bangladesh has been experiencing highly pathogenic avian influenza (HPAI) outbreaks since 2007, mostly in chickens and occasionally in ducks. Ducks play an important role in the persistence and genetic recombination of AI viruses. This paper presents the results of serological and virological monitoring of AI in domestic ducks in 2013 in the north-east region of Bangladesh.

Results

A total of 871 and 662 serum samples and 909 and 302 pairs of cloacal and oropharyngeal swabs from domestic ducks of Mymensingh and Sylhet division, respectively, were analysed. Antibodies to type A influenza virus were detected by blocking ELISA in 60.73 and 47.73% serum samples of Mymensingh and Sylhet division, respectively. On haemagglutination-inhibition (HI) test 17.5% of ELISA positive serum samples were found to be seropositive to H5 avian influenza virus. Five cloacal swabs and one oropharyngeal swab were positive for M gene of type A influenza virus by real time RT-PCR (rRT-PCR), but all of them were negative for H5 influenza virus. Three of the six viruses were successfully characterized as H1N5, H2N5 and H7N5 subtype of AI virus, the other three remained uncharacterized. On sequencing and phylogenetic analysis the HA and NA genes were found to be of Eurasian avian lineage. The H7 virus had cleavage site motif of low pathogenic virus.

Conclusions

Low pathogenic avian influenza viruses were detected from apparently healthy domestic ducks. A small proportion of domestic ducks were found seropositive to H5 AI virus.

Cherry Valley Ducks Mitochondrial Antiviral-Signaling Protein-Mediated Signaling Pathway and Antiviral Activity Research

Mitochondrial antiviral-signaling protein (MAVS), an adaptor protein of retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs)-mediated signal pathway, is involved in innate immunity. In this study, Cherry Valley duck MAVS (duMAVS) was cloned from the spleen and analyzed. duMAVS was determined to have a caspase activation and recruitment domain at N-terminal, followed by a proline-rich domain and a transmembrane domain at C-terminal. Quantitative real-time PCR indicated that duMAVS was expressed in all tissues tested across a broad expression spectrum. The expression of duMAVS was significantly upregulated after infection with duck Tembusu virus (DTMUV). Overexpression of duMAVS could drive the activation of interferon (IFN)-β, nuclear factor-κB, interferon regulatory factor 7, and many downstream factors (such as Mx, PKR, OAS, and IL-8) in duck embryo fibroblast cells. What is more, RNA interference further confirmed that duMAVS was an important adaptor for IFN-β activation. The antiviral assay showed that duMAVS could suppress the various viral replications (DTMUV, novel reovirus, and duck plague virus) at early stages of infection. Overall, these results showed that the main signal pathway mediated by duMAVS and it had a broad-spectrum antiviral ability. This research will be helpful to better understanding the innate immune system of ducks.

Genetic and molecular characterization of a novel reassortant H2N8 subtype avian influenza virus isolated from a domestic duck in Zhejiang Province in China

The circulation of the H2 subtype influenza viruses in domestic animals increases the risk of human exposure to these viruses. An H2N8 avian influenza virus (AIV) was isolated from a domestic duck during AIV surveillance of poultry in live poultry markets (LPMs) in Zhejiang Province, Eastern China, in 2013. The phylogenetic trees suggested that this strain is a novel reassortant virus derived from multiple AIV subtypes from aquatic birds and poultry in Eastern Asia. Although this reassortant strain exhibited low pathogenicity in mice, it was able to replicate in the lungs of the mice without prior adaptation. Continued surveillance of domestic ducks in LPMs is required for early detection of AIV outbreaks in poultry and humans.

Novel Highly Pathogenic Avian H5 Influenza A Viruses in Live Poultry Markets, Wuxi City, China, 2013-2014

During 12 recent months of periodic influenza virus surveillance at 9 live poultry markets in Wuxi City China, we identified multiple highly pathogenic H5N6, H5N8, H5N2, and H5N1 avian influenza viruses. The variety of potentially pandemic viruses in this low-risk area is disconcerting and portends an increased pandemic threat.

Nosocomial transmission of avian influenza A (H7N9) virus in China: epidemiological investigation

STUDY QUESTION

Can avian influenza A (H7N9) virus be transmitted between unrelated individuals in a hospital setting?

METHODS

An epidemiological investigation looked at two patients who shared a hospital ward in February 2015, in Quzhou, Zhejiang Province, China. Samples from the patients, close contacts, and local environments were examined by real time reverse transcriptase (rRT) polymerase chain reaction (PCR) and viral culture. Haemagglutination inhibition and microneutralisation assays were used to detect specific antibodies to the viruses. Primary outcomes were clinical data, infection source tracing, phylogenetic tree analysis, and serological results.

STUDY ANSWER AND LIMITATIONS

A 49 year old man (index patient) became ill seven days after visiting a live poultry market. A 57 year old man (second patient), with a history of chronic obstructive pulmonary disease, developed influenza-like symptoms after sharing the same hospital ward as the index patient for five days. The second patient had not visited any poultry markets nor had any contact with poultry or birds within 15 days before the onset of illness. H7N9 virus was identified in the two patients, who both later died. Genome sequences of the virus isolated from both patients were nearly identical, and genetically similar to the virus isolated from the live poultry market. No specific antibodies were detected among 38 close contacts. Transmission between the patients remains unclear, owing to the lack of samples collected from their shared hospital ward. Although several environmental swabs were positive for H7N9 by rRT-PCR, no virus was cultured. Owing to delayed diagnosis and frequent hospital transfers, no serum samples were collected from the patients, and antibodies to H7N9 viruses could not be tested.

WHAT THIS STUDY ADDS

Nosocomial H7N9 transmission might be possible between two unrelated individuals. Surveillance on patients with influenza-like illness in hospitals as well as chickens in live poultry markets should be enhanced to monitor transmissibility and pathogenicity of the virus.

FUNDING, COMPETING INTERESTS, DATA SHARING

Funding support from the Program of International Science and Technology Cooperation of China (2013DFA30800), Basic Work on Special Program for Science and Technology Research (2013FY114600), National Natural Science Foundation of China (81402730), Special Program for Prevention and Control of Infectious Diseases in China (2013ZX10004218), US National Institutes of Health (1R01-AI108993), Zhejiang Province Major Science and Technology Program (2014C03039), and Quzhou Science and Technology Program (20111084). The authors declare no other interests and have no additional data.