Infection of chicken H9N2 influenza viruses in different species of domestic ducks

Current situation and control strategies of H9N2 avian influenza in South Korea

The H9N2 avian influenza (AI) has become endemic in poultry in many countries since the 1990s, which has caused considerable economic losses in the poultry industry. Considering the long history of the low pathogenicity H9N2 AI in many countries, once H9N2 AI is introduced, it is more difficult to eradicate than high pathogenicity AI. Various preventive measures and strategies, including vaccination and active national surveillance, have been used to control the Y439 lineage of H9N2 AI in South Korea, but it took a long time for the H9N2 virus to disappear from the fields. By contrast, the novel Y280 lineage of H9N2 AI was introduced in June 2020 and has spread nationwide. This study reviews the history, genetic and pathogenic characteristics, and control strategies for Korean H9N2 AI. This review may provide some clues for establishing control strategies for endemic AIV and a newly introduced Y280 lineage of H9N2 AI in South Korea.

Influence of Host Sialic Acid Receptors Structure on the Host Specificity of Influenza Viruses

Influenza viruses need to use sialic acid receptors to invade host cells, and the α-2,3 and α-2,6 sialic acids glycosidic bonds linking the terminal sialic acids are generally considered to be the most important factors influencing the cross-species transmission of the influenza viruses. The development of methods to detect the binding of influenza virus HA proteins to sialic acid receptors, as well as the development of glycobiological techniques, has led to a richer understanding of the structure of the sialylated glycan in influenza virus hosts. It was found that, in addition to the sialic acid glycosidic bond, sialic acid variants, length of the sialylated glycan, Gal-GlcNAc-linked glycosidic bond within the sialylated glycan, and sulfation/fucosylation of the GlcNAc within the sialylated glycan all affect the binding properties of influenza viruses to the sialic acid receptors, thus indirectly affecting the host specificity of influenza viruses. This paper will review the sialic acid variants, internal structural differences of sialylated glycan molecules that affect the host specificity of influenza viruses, and distribution characteristics of sialic acid receptors in influenza virus hosts, in order to provide a more reliable theoretical basis for the in-depth investigation of cross-species transmission of influenza viruses and the development of new antiviral drugs.

Enhanced stability of M1 protein mediated by a phospho-resistant mutation promotes the replication of prevailing avian influenza virus in mammals

Avian influenza virus (AIV) can evolve multiple strategies to combat host antiviral defenses and establish efficient infectivity in mammals, including humans. H9N2 AIV and its reassortants (such as H5N6 and H7N9 viruses) pose an increasing threat to human health; however, the mechanisms involved in their increased virulence remain poorly understood. We previously reported that the M1 mutation T37A has become predominant among chicken H9N2 isolates in China. Here, we report that, since 2010, this mutation has also been found in the majority of human isolates of H9N2 AIV and its emerging reassortants. The T37A mutation of M1 protein enhances the replication of H9N2 AIVs in mice and in human cells. Interestingly, having A37 instead of T37 increases the M1 protein stability and resistance to proteasomal degradation. Moreover, T37 of the H9N2 M1 protein is phosphorylated by protein kinase G (PKG), and this phosphorylation induces the rapid degradation of M1 and reduces viral replication. Similar effects are also observed in the novel H5N6 virus. Additionally, ubiquitination at K187 contributes to M1-37T degradation and decreased replication of the virus harboring T37 in the M1 protein. The prevailing AIVs thereby evolve a phospho-resistant mutation in the M1 protein to avoid viral protein degradation by host factors, which is advantageous in terms of replication in mammalian hosts.

H9N2 avian influenza virus (AIV) and its reassortants (such as H5N6 and H7N9 viruses) pose an increasing threat to human health, but the mechanisms involved in their increased virulence remain poorly understood. Notably, the role of viral M1 protein in increasing the mammalian infection of AIV has been rarely reported. Here, we demonstrate that a phospho-resistant T37A mutation, encoded by the M1 protein of recently prevalent chicken H9N2 virus, increases M1 protein stability and viral replication in mammalian cells. The T37, but not the A37, in H9N2 M1 protein can be phosphorylated by protein kinase G (PKG). Through the T37A mutation, viral M1 protein evades phosphorylation-mediated proteasomal degradation, resulting in increased avian H9N2 virus replication in mice and in human cells. Similar effects were also observed for the novel H5N6 virus. This study provides insight into a novel strategy by which AIV evades mammalian host defenses. It is necessary to pay close attention to the epidemiological and public health implications of AIVs carrying this mutant M1 protein.

Monitoring of aquatic birds and surveillance of avian influenza and Newcastle disease of waterfowls at the National Park of Urmia Lake

BACKGROUND

Urmia lake, as a national park, is one of the most valuable aquatic ecosystems in the Middle East and quatitative and qualitative changes in Urmia lake water have a great impact on its ecological performance and in the region.

OBJECTIVES

This project was designed to study the effects of the extent of Urmia lake water surface area on the area size and on the number of aquatic birds of the six selected habitats in 2011-2019. The presence of avian influenza (AI) and Newcastle disease (ND) viruses in migratory aquatic birds together with their impacts on poultry farms as well as on rural birds was also under surveillance in 2018-2019.

METHODS

Changes of Urmia lake and its impacts on area size of the six selected birds habitats were monitored by GIS. The small monitoring program with circular plot point counts was used for counting of the number of birds of the six selected habitats. At least, 100 samples (oropharyngeal and cloacal swabs) were collected. each sample was placed in a sterile plastic tube containg transport media and assigned with an number and store untill used. Reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR test were used for detection of AI and ND viruses in the samples.

RESULTS

The results revealed that changes in the water surface area of Urmia lake had a gsignificat impacts on area size and the number of aquatic birds of the six selected habitats. The surveillance results showed that 5% of the samples were AIV positvie while 25% of the samples were pasitive for NDV including 20% for non-virulent NDV (lNDV) and 5% for virulent NDV (vNDV) strains.

CONCLUSION

This study showed that fluctuation of Urmia lake's water surface area influenced (p < 0.05) the area size of the six selected aquatic birds' habitats and had a great impacts on the number of the migratory birds. Detection of AIV and vNDV emphesises that the seasonal migratory waterfowls spread AI and vND viruses to the ponds and estuaries as well as to the rural birds and industrialised poultry units around the Urmia lake. Potential public health treats were also discussed.

Antigenic Evolution Characteristics and Immunological Evaluation of H9N2 Avian Influenza Viruses from 1994–2019 in China

The H9N2 subtype avian influenza viruses (AIVs) have been circulating in China for more than 20 years, attracting more and more attention due to the potential threat of them. At present, vaccination is a common prevention and control strategy in poultry farms, but as virus antigenicity evolves, the immune protection efficiency of vaccines has constantly been challenged. In this study, we downloaded the hemagglutinin (HA) protein sequences of the H9N2 subtype AIVs from 1994 to 2019 in China—with a total of 5138 sequences. The above sequences were analyzed in terms of time and space, and it was found that h9.4.2.5 was the most popular in various regions of China. Furthermore, the prevalence of H9N2 subtype AIVs in China around 2006 was different. The domestic epidemic branch was relatively diversified from 1994 to 2006. After 2006, the epidemic branch each year was h9.4.2.5. We compared the sequences around 2006 as a whole and screened out 15 different amino acid positions. Based on the HA protein of A/chicken/Guangxi/55/2005 (GX55), the abovementioned amino acid mutations were completed. According to the 12-plasmid reverse genetic system, the rescue of the mutant virus was completed using A/PuertoRico/8/1934 (H1N1) (PR8) as the backbone. The cross hemagglutination inhibition test showed that these mutant sites could transform the parental strain from the old to the new antigenic region. Animal experiments indicated that the mutant virus provided significant protection against the virus from the new antigenic region. This study revealed the antigenic evolution of H9N2 subtype AIVs in China. At the same time, it provided an experimental basis for the development of new vaccines.

Transcriptional Insights into Key Genes and Pathways Underlying Muscovy Duck Subcutaneous Fat Deposition at Different Developmental Stages

Simple Summary

Subcutaneous fat is an important factor affecting the meat quality and feed conversion rate of waterfowl. The current study compared the transcriptome data of Muscovy duck subcutaneous fat among three developmental stages, aiming at exploring the key regulatory genes for subcutaneous fat deposition. The results generated abundant candidate genes and pathways involving in subcutaneous fat deposition in Muscovy duck. This study provides an important reference for revealing the developmental mechanisms of subcutaneous fat in duck.

Abstract

Subcutaneous fat is a crucial trait for waterfowl, largely associated with meat quality and feed conversion rate. In this study, RNA-seq was used to identify differentially expressed genes of subcutaneous adipose tissue among three developmental stages (12, 35, and 66 weeks) in Muscovy duck. A total of 138 and 129 differentially expressed genes (DEGs) were identified between 35 and 12 weeks (wk), and 66 and 35 wk, respectively. Compared with 12 wk, subcutaneous fat tissue at 35 wk upregulated several genes related to cholesterol biosynthesis and fatty acid biosynthesis, including HSD17B7 and MSMO1, while it downregulated fatty acid beta-oxidation related genes, including ACOX1 and ACSL1. Notably, most of the DEGs (92.2%) were downregulated in 66 wk compared with 35 wk, consistent with the slower metabolism of aging duck. Protein network interaction and function analyses revealed GC, AHSG, FGG, and FGA were the key genes for duck subcutaneous fat from adult to old age. Additionally, the PPAR signaling pathway, commonly enriched between the two comparisons, might be the key pathway contributing to subcutaneous fat metabolism among differential developmental stages in Muscovy duck. These results provide several candidate genes and pathways potentially involved in duck subcutaneous fat deposition, expanding our understanding of the molecular mechanisms underlying subcutaneous fat deposition during development.

Pathogenicity of H9N2 low pathogenic avian influenza viruses of different lineages isolated from live bird markets tested in three animal models: SPF chickens, Korean native chickens, and ducks

Since its first appearance in 1996, H9N2 avian influenza virus (AIV) of the Y439 lineage persisted in Korean live bird markets (LBMs) until the last documented occurrence in 2018. However, in June 2020, the avian influenza surveillance program detected a novel H9N2 AIV belonging to the Y280 lineage, which has zoonotic potential, in a Korean native chicken (KNC) from a LBM. In this study, we infected KNCs and ducks (the 2 major species held at LBMs), as well as SPF chickens, with Y280-lineage H9N2 AIV LBM261/20 and Y439-equivalent LBM294/18 to compare pathogenicity and transmissibility. In SPF chickens, LBM261/20 replicated mostly in the respiratory tract and spread rapidly among birds. By contrast, LBM294/18 replicated preferentially in the gastrointestinal tract and transmitted more slowly than LBM261/20. LBM261/20 replicated for a longer time in KNCs than in SPF chickens, and only in the respiratory tract; by contrast, LBM294/18 was detected in the oropharynx and cloaca. Ducks did not shed either virus or seroconvert. Taken together, the data suggest that the scheme used to monitor the newly introduced H9N2 AIV of the Y280 lineage needs to be modified to place emphasis on oropharyngeal sampling. Such changes will facilitate better disease control and protect public health.

Lactobacillus plantarum surface-displayed influenza antigens (NP-M2) with FliC flagellin stimulate generally protective immune responses against H9N2 influenza subtypes in chickens

The H9N2 avian influenza virus (AIV) causes serious economic losses to the poultry industry every year. Vaccines that induce a mucosal immune response may be successful against influenza virus infection because its transmission occurs primarily in the mucosa. To develop novel and potent oral vaccines based on Lactobacillus plantarum (L. plantarum) to control the spread of AIV in poultry industry, in the present study, we constructed and expressed fusions of the influenza antigens NP and M2 with the Salmonella Typhimurium flagellinprotein FliC on the surface of L. plantarum. Oral immunization of chicks was performed, and serum antibodies, mucosal antibodies, and specific cellular immunity were detected. Immunizing chicks with avian influenza virus was evaluated. The results showed high levels of IgG in addition to high levels of secretory immunoglobulin A (sIgA) in chickens orally administered recombinant L. plantarum. In addition, the fusion may significantly increase the levels of NP- and M2-specific T cell-mediated immunity in the case of mucosal administration of NC8-pSIP409-pgsA'-NP-M2-FliC. Recombinant NC8-pSIP409-pgsA'-NP-M2-FliC mediated effectively protected chickens against influenza virus and reduced virus titers in the lung. Our study outcomes indicate that the expression of influenza NP-M2 and a mucosal adjuvant (FliC), by L. plantarum could generate a mucosal vaccine candidate for animals in the future to defend against AIVs.

H9 Influenza Viruses: An Emerging Challenge

Influenza A viruses (IAVs) of the H9 subtype are enzootic in Asia, the Middle East, and parts of North and Central Africa, where they cause significant economic losses to the poultry industry. Of note, some strains of H9N2 viruses have been linked to zoonotic episodes of mild respiratory diseases. Because of the threat posed by H9N2 viruses to poultry and human health, these viruses are considered of pandemic concern by the World Health Organization (WHO). H9N2 IAVs continue to diversify into multiple antigenically and phylogenetically distinct lineages that can further promote the emergence of strains with pandemic potential. Somewhat neglected compared with the H5 and H7 subtypes, there are numerous indicators that H9N2 viruses could be involved directly or indirectly in the emergence of the next influenza pandemic. The goal of this work is to discuss the state of knowledge on H9N2 IAVs and to provide an update on the contemporary global situation.

Live bird markets as evolutionary epicentres of H9N2 low pathogenicity avian influenza viruses in Korea

Live bird markets (LBMs) in Korea have been recognized as a reservoir, amplifier, and source of avian influenza viruses (AIVs); however, little was known about the role of LBMs in the epidemiology of AIVs in Korea until recently. Through 10 years of surveillance (2006–2016) we have isolated and sequenced H9N2 viruses in Korean LBMs. To understand how H9N2 evolves and spreads in Korea, a statistical Bayesian phylogenetic model was used. Phylogenetic analysis suggests that three separate introductions of progenitor gene pools, Korean domestic duck-origin and two wild aquatic bird-origin AIVs, contributed to the generation of the five genotypes of H9N2 viruses in Korea. Phylogenetic reconstruction of ecological states infer that the LBMs are where chickens become infected with the virus, with domestic ducks playing a major role in the transmission and evolution of the H9N2 viruses. Three increases in the genetic diversity of H9N2 viruses were observed and coincided with transitions in host species and the locations (domestic farm, LBM, slaughterhouse, and wild aquatic bird habitat) where the viruses were isolated, accompanying genetic reassortment. Following the introduction of a wild aquatic bird-origin AIVs in 2008, six genes of the Korean lineage H9N2 virus were replaced with genes originating from wild aquatic birds, and viruses with this new genotype became predominant in Korean LBMs.

Avian influenza overview February- August 2019

Between 16 February and 15 August 2019, five HPAI A(H5N8) outbreaks at poultry establishments in Bulgaria, two low pathogenic avian influenza (LPAI) A(H5N1) outbreaks in poultry in Denmark and one in captive birds in Germany, one LPAI A(H7N3) outbreak in poultry in Italy and one LPAI A(H7N7) outbreak in poultry in Denmark were reported in Europe. Genetic characterisation reveals that viruses from Denmark cluster with viruses previously identified in wild birds and poultry in Europe; while the Italian isolate clusters with LPAI viruses circulating in wild birds in Central Asia. No avian influenza outbreaks in wild birds were notified in Europe in the relevant period for this report. A decreased number of outbreaks in poultry and wild birds in Asia, Africa and the Middle East was reported during the time period for this report, particularly during the last three months. Furthermore, only six affected wild birds were reported in the relevant time period of this report. Currently there is no evidence of a new HPAI virus incursion from Asia into Europe. However, passive surveillance systems may not be sensitive for early detection if the prevalence or case fatality in wild birds is very low. Therefore, it is important to encourage and maintain passive surveillance in Europe encouraging a search for carcasses of wild bird species that are in the revised list of target species in order to detect any incursion of HPAI virus early and initiate warning. No human infections due to HPAI viruses - detected in wild birds and poultry outbreaks in Europe - have been reported during the last years and the risk of zoonotic transmission to the general public in Europe is considered very low.