Replication Capacity of Avian Influenza A(H9N2) Virus in Pet Birds and Mammals, Bangladesh

Recombinant Hemagglutinin protein and DNA-RNA-combined nucleic acid vaccines harbored by Yeast elicit protective immunity against H9N2 Avian Influenza infection

A safe, convenience, and effective vaccine for controlling avian influenza virus infection is crucial in scale poultry production. Yeasts are considered useful vaccine vehicles for the delivery of antigens, which has been used to protect human and animal health. We report here the development of H9N2 strain hemagglutinin (HA)-based recombinant protein vaccines (rH9HA) and DNA-RNA-combined vaccine (rH9-DNA-RNA) in Saccharomyces cerevisiae for the first time. The immunogenicity assay indicated that both rH9HA and rH9-DNA-RNA could induce robust production of serum IgG, mucosal sIgA, and cellular immune responses. The reshape and diversification of gut microbiota and an enriched Lactobacillus, Debaryomyces were observed after oral immunization with rH9HA or rH9-DNA-RNA yeast vaccine, which might contribute to modulate the intestinal mucosal immunity and antiviral process. Oral immunized birds with either rH9HA or rH9-DNA-RNA were effectively protected from H9N2 virus challenge. Our findings suggested that yeast-derived H9N2 HA-based recombinant protein vaccines and DNA-RNA-combined nucleic acid vaccines are feasible and efficacious, opening up a new avenue for rapid and cost-effective production of avian influenza vaccines to achieve good protection effect.

Non-basic amino acids in the hemagglutinin proteolytic cleavage site of a European H9N2 avian influenza virus modulate virulence in turkeys

H9N2 avian influenza virus (AIV) is the most widespread low pathogenic (LP) AIV in poultry and poses a serious zoonotic risk. Vaccination is used extensively to mitigate the economic impact of the virus. However, mutations were acquired after long-term circulation of H9N2 virus in poultry, particularly in the hemagglutinin (HA) proteolytic cleavage site (CS), a main virulence determinant of AIV. Compared to chickens, little is known about the genetic determinants for adaptation of H9N2 AIV to turkeys. Here, we describe 36 different CS motifs in Eurasian H9N2 viruses identified from 1966 to 2019. The European H9N2 viruses specify unique HACS with particular polymorphism by insertion of non-basic amino acids at position 319. Recombinant viruses carrying single HACS mutations resembling field viruses were constructed (designated G319, A319, N319, S319, D319 and K319). Several viruses replicated to significantly higher titers in turkey cells than in chicken cells. Serine proteases were more efficient than trypsin to support multicycle replication in mammalian cells. Mutations affected cell-to-cell spread and pH-dependent HA fusion activity. In contrast to chickens, mutations in the HACS modulated clinical signs in inoculated and co-housed turkeys. G319 exhibited the lowest virulence, however, it replicated to significantly higher titers in contact-turkeys and in vitro. Interestingly, H9N2 viruses, particularly G319, replicated in brain cells of turkeys and to a lesser extent in mammalian brain cells independent of trypsin. Therefore, the silent circulation of potentially zoonotic H9N2 viruses in poultry should be monitored carefully. These results are important for understanding the adaptation of H9N2 in poultry and replication in mammalian cells.

Genetically and Antigenically Divergent Influenza A(H9N2) Viruses Exhibit Differential Replication and Transmission Phenotypes in Mammalian Models

Low-pathogenicity avian influenza A(H9N2) viruses, enzootic in poultry populations in Asia, are associated with fewer confirmed human infections but higher rates of seropositivity compared to A(H5) or A(H7) subtype viruses. Cocirculation of A(H5) and A(H7) viruses leads to the generation of reassortant viruses bearing A(H9N2) internal genes with markers of mammalian adaptation, warranting continued surveillance in both avian and human populations. Here, we describe active surveillance efforts in live poultry markets in Vietnam in 2018 and compare representative viruses to G1 and Y280 lineage viruses that have infected humans. Receptor binding properties, pH thresholds for HA activation, in vitro replication in human respiratory tract cells, and in vivo mammalian pathogenicity and transmissibility were investigated. While A(H9N2) viruses from both poultry and humans exhibited features associated with mammalian adaptation, one human isolate from 2018, A/Anhui-Lujiang/39/2018, exhibited increased capacity for replication and transmission, demonstrating the pandemic potential of A(H9N2) viruses.IMPORTANCE A(H9N2) influenza viruses are widespread in poultry in many parts of the world and for over 20 years have sporadically jumped species barriers to cause human infection. As these viruses continue to diversify genetically and antigenically, it is critical to closely monitor viruses responsible for human infections, to ascertain if A(H9N2) viruses are acquiring properties that make them better suited to infect and spread among humans. In this study, we describe an active poultry surveillance system established in Vietnam to identify the scope of influenza viruses present in live bird markets and the threat they pose to human health. Assessment of a recent A(H9N2) virus isolated from an individual in China in 2018 is also reported, and it was found to exhibit properties of adaptation to humans and, importantly, it shows similarities to strains isolated from the live bird markets of Vietnam.

Experimental direct-contact transmission of influenza A/H9N2 virus in the guinea pig model in Iran

Aim: The present study aims to evaluate risk factors for the transmission of A/H9N2 viruses in guinea pig model. Materials & methods: Lung tissue samples were collected from the chicken clinically infected with influenza A/H9N2 virus in 2018. Next, virus isolation and titration, as well as reverse transcription PCR were performed. Then, hemagglutnation and neuraminidase genes was sequenced to identify different positions (hotspots) involved in transmission and host adaptation. Results: Influenza A/H9N2 virus could replicate in low titers in the nasal turbinate and transmit from infected to noninfected guinea pigs. Conclusion: Hotspots on the surface glycoproteins had the potential to alter transmission properties in the new host.

Antiviral efficacy of nanoparticulate vacuolar ATPase inhibitors against influenza virus infection

Background

Influenza virus infections are a major public health concern worldwide. Conventional treatments against the disease are designed to target viral proteins. However, the emergence of viral variants carrying drug-resistant mutations can outpace the development of pathogen-targeting antivirals. Diphyllin and bafilomycin are potent vacuolar ATPase (V-ATPase) inhibitors previously shown to have broad-spectrum antiviral activity. However, their poor water solubility and potential off-target effect limit their clinical application.

Methods

In this study, we report that nanoparticle encapsulation of diphyllin and bafilomycin improves the drugs’ anti-influenza applicability.

Results

Using PEG-PLGA diblock copolymers, sub-200 nm diphyllin and bafilomycin nanoparticles were prepared, with encapsulation efficiency of 42% and 100%, respectively. The drug-loaded nanoparticles have sustained drug release kinetics beyond 72 hours and facilitate intracellular drug delivery to two different influenza virus-permissive cell lines. As compared to free drugs, the nanoparticulate V-ATPase inhibitors exhibited lower cytotoxicity and greater in vitro antiviral activity, improving the therapeutic index of diphyllin and bafilomycin by approximately 3 and 5-fold, respectively. In a mouse model of sublethal influenza challenge, treatment with diphyllin nanoparticles resulted in reduced body weight loss and viral titer in the lungs. In addition, following a lethal influenza viral challenge, diphyllin nanoparticle treatment conferred a survival advantage of 33%.

Conclusions

These results demonstrate the potential of the nanoparticulate V-ATPase inhibitors for host-targeted treatment against influenza.

Domestic canaries (Serinus canaria forma domestica) are susceptible to low pathogenic avian influenza virus infections

Avian influenza viruses have been isolated from many bird species; however, little is known about the susceptibility of pet birds to low pathogenic avian influenza (LPAI) viruses. To address this research gap, domestic canaries (Serinus canaria forma domestica) were experimentally infected with H5 and H7 LPAI viruses to determine susceptibility and to evaluate samples for diagnostic purposes. Clinical evidence of infection (e.g. ruffled plumage and apathy) and mortality were noted for the canaries inoculated with chicken-adapted LPAI viruses. Real-time reverse transcription-polymerase chain reaction (RRT-PCR) demonstrated higher viral RNA levels in buccal compared to faecal samples. No clinical signs or mortality were observed in canaries inoculated with LPAI virus originating from wild birds; however, the canaries in this group did have evidence of viral RNA in buccal and faecal samples. Overall, this study showed that domestic canaries are susceptible to LPAI virus infections and that they can shed large amounts of viral RNA, primarily through the respiratory route. Thus, buccal swabs might be better samples than faeces for efficient detection of some LPAI virus infections in these birds. Although canaries have not been identified as a significant reservoir for LPAI viruses, they may be infected by LPAI viruses. Thus, the importance of the control of domestic canaries for detection of LPAI viruses should not be underestimated, especially in the contexts of international commercial exchange and outbreaks. RESEARCH HIGHLIGHTS Canaries are susceptible to infection with H5/H7 LPAI viruses. Canaries inoculated with LPAI viruses excrete large amounts of viral RNA. Buccal swabs may be appropriate specimens for AI virus detection in canaries. The control of canaries for LPAI virus detection should not be overlooked.

The eyes have it: influenza virus infection beyond the respiratory tract

Avian and human influenza A viruses alike have shown a capacity to use the eye as a portal of entry and cause ocular disease in human beings. However, whereas influenza viruses generally represent a respiratory pathogen and only occasionally cause ocular complications, the H7 virus subtype stands alone in possessing an ocular tropism. Clarifying what confers such non-respiratory tropism to a respiratory virus will permit a greater ability to identify, treat, and prevent zoonotic human infection following ocular exposure to influenza viruses; especially those within the H7 subtype, which continue to cause avian epidemics on many continents.

Avian influenza

Previous introductions of highly pathogenic avian influenza virus (HPAIV) to the EU were most likely via migratory wild birds. A mathematical model has been developed which indicated that virus amplification and spread may take place when wild bird populations of sufficient size within EU become infected. Low pathogenic avian influenza virus (LPAIV) may reach similar maximum prevalence levels in wild bird populations to HPAIV but the risk of LPAIV infection of a poultry holding was estimated to be lower than that of HPAIV. Only few non-wild bird pathways were identified having a non-negligible risk of AI introduction. The transmission rate between animals within a flock is assessed to be higher for HPAIV than LPAIV. In very few cases, it could be proven that HPAI outbreaks were caused by intrinsic mutation of LPAIV to HPAIV but current knowledge does not allow a prediction as to if, and when this could occur. In gallinaceous poultry, passive surveillance through notification of suspicious clinical signs/mortality was identified as the most effective method for early detection of HPAI outbreaks. For effective surveillance in anseriform poultry, passive surveillance through notification of suspicious clinical signs/mortality needs to be accompanied by serological surveillance and/or a virological surveillance programme of birds found dead (bucket sampling). Serosurveillance is unfit for early warning of LPAI outbreaks at the individual holding level but could be effective in tracing clusters of LPAIV-infected holdings. In wild birds, passive surveillance is an appropriate method for HPAIV surveillance if the HPAIV infections are associated with mortality whereas active wild bird surveillance has a very low efficiency for detecting HPAIV. Experts estimated and emphasised the effect of implementing specific biosecurity measures on reducing the probability of AIV entering into a poultry holding. Human diligence is pivotal to select, implement and maintain specific, effective biosecurity measures.

Infectious Diseases

The chapter describes bacerial, viral, parasitic and fungal infections commonly detected in pet birds. The chapter includes history, etiology, susceptible hosts, transmission, pathogenesis, clinical symptoms, lesion, diagnosis, zoonosis, Treatment and control strategy of Tuberculosis, Salmonellosis, Chlamydiosis, Campylobacteriosis, Lyme disease, other bacterial infection, Newcastle disease, Avian Influenza infection, West Nile Virus infection, Usutu virus infection, Avian Borna Virus infection, Beak and feather disease, other viral infection, Toxoplasmosis, Giardiasis, Cryptosporidiosis, other parasitic infection, Cryptococcosis, Aspergillosis, Other fungal infections.

The replication of Bangladeshi H9N2 avian influenza viruses carrying genes from H7N3 in mammals

H9N2 avian influenza viruses are continuously monitored by the World Health Organization because they are endemic; they continually reassort with H5N1, H7N9 and H10N8 viruses; and they periodically cause human infections. We characterized H9N2 influenza viruses carrying internal genes from highly pathogenic H7N3 viruses, which were isolated from chickens or quail from live-bird markets in Bangladesh between 2010 and 2013. All of the H9N2 viruses used in this study carried mammalian host-specific mutations. We studied their replication kinetics in normal human bronchoepithelial cells and swine tracheal and lung explants, which exhibit many features of the mammalian airway epithelium and serve as a mammalian host model. All H9N2 viruses replicated to moderate-to-high titers in the normal human bronchoepithelial cells and swine lung explants, but replication was limited in the swine tracheal explants. In Balb/c mice, the H9N2 viruses were nonlethal, replicated to moderately high titers and the infection was confined to the lungs. In the ferret model of human influenza infection and transmission, H9N2 viruses possessing the Q226L substitution in hemagglutinin replicated well without clinical signs and spread via direct contact but not by aerosol. None of the H9N2 viruses tested were resistant to the neuraminidase inhibitors. Our study shows that the Bangladeshi H9N2 viruses have the potential to infect humans and highlights the importance of monitoring and characterizing this influenza subtype to better understand the potential risk these viruses pose to humans.