Comparison of pathogenicities of H7 avian influenza viruses via intranasal and conjunctival inoculation in cynomolgus macaques

Lectin Staining to Detect Human and Avian Influenza Virus Receptors in the Airway of Nonhuman Primates

Hemagglutinin (HA) on the surface of influenza viruses binds to sialic acids, mainly N-acetylneuraminic acid (Neu5Ac) or N-glycolylneuraminic acid. Neu5Ac and N-glycolylneuraminic acid lie at the terminal end of sugar chains on the cell surface. Human influenza viruses preferentially bind to sialic acids bound to galactose by the alpha2-6 linkage (Neu5Acα2-6Gal), abundant in the human airway. In contrast, avian influenza viruses preferentially bind to Neu5Acα2-3Gal, abundant in the intestine of ducks. Sambucus nigra lectin (SNA) and Maackia amurensis lectin (MAA) bind to Neu5Acα2-6Gal and Neu5Acα2-3Gal, respectively. These two lectins have therefore been applied to detect sialic acids on the airway epithelium of animals.

Low replicative fitness of neuraminidase inhibitor-resistant H7N9 avian influenza a virus with R292K substitution in neuraminidase in cynomolgus macaques compared with I222T substitution

Human cases of H7N9 influenza A virus infection have been increasing since 2013. The first choice of treatment for influenza is neuraminidase (NA) inhibitors (NAIs), but there is a concern that NAI-resistant viruses are selected in the presence of NAIs. In our previous study, an H7N9 virus carrying AA substitution of threonine (T) for isoleucine (I) at residue 222 in NA (NA222T, N2 numbering) and an H7N9 virus carrying AA substitution of lysine (K) for arginine (R) at residue 292 in NA (NA292K, N2 numbering) were found in different macaques that had been infected with A/Anhui/1/2013 (H7N9) and treated with NAIs. In the present study, the variant with NA292K showed not only resistance to NAIs but also lower replication activity in MDCK cells than did the virus with wild-type NA, whereas the variant with NA222T, which was less resistant to NAIs, showed replication activity similar to that of the wild-type virus. Next, we examined the pathogenicity of these H7N9 NAI-resistant viruses in macaques. The variants caused clinical signs similar to those caused by the wild-type virus with similar replication potency. However, the virus with NA292K was replaced within 7 days by that with NA292R (same as the wild-type) in nasal samples from macaques infected with the virus with NA292K, i.e. the so-called revertant (wild-type virus) became dominant in the population in the absence of an NAI. These results suggest that the clinical signs observed in macaques infected with the NA292K virus are caused by the NA292K virus and the NA292R virus and that the virus with NA292K may not replicate continuously in the upper respiratory tract of patients without treatment as effectively as the wild-type virus.

Avian H5N1 influenza virus infection causes severe pneumonia in the Northern tree shrew (Tupaia belangeri)

Avian-origin influenza viruses like H5N1 and H7N9 often cause severe symptoms with high mortality in humans. Animal models are useful for clarification of the mechanisms of pathogenicity of these infections. In this study, to expand the potential utility of the Northern tree shrew (Tupaia belangeri) for influenza virus infection, we assessed the pathogenicity of H5N1 and H7N9 avian influenza viruses in tupaia. Infectious virus was detected continuously from nasal, oral, tracheal, and conjunctival swab samples in the animals infected with these viruses. H5N1 influenza virus infection of tupaia caused severe diffuse pneumonia with fever and weight loss. In contrast, H7N9 influenza virus infection caused focal pneumonia. The severity of pneumonia was correlated with proinflammatory cytokine transcript levels. These results indicated that tupaia can be another suitable animal model for avian influenza virus research.

Assessment of low pathogenic avian influenza virus transmission via raw poultry meat and raw table eggs

A rapid qualitative assessment has been done by performing a theoretical analysis on the transmission of low pathogenic avian influenza (LPAI) via fresh meat from poultry reared or kept in captivity for the production of meat (raw poultry meat) or raw table eggs. A predetermined transmission pathway followed a number of steps from a commercial or non-commercial poultry establishment within the EU exposed to LPAI virus (LPAIV) to the onward virus transmission to animals and humans. The combined probability of exposure and subsequent LPAIV infection via raw poultry meat containing LPAIV is negligible for commercial poultry and humans exposed via consumption whereas it is very unlikely for non-commercial poultry, wild birds and humans exposed via handling and manipulation. The probability of LPAIV transmission from an individual infected via raw poultry meat containing LPAIV is negligible for commercial poultry and humans, whereas it is very unlikely for non-commercial poultry and wild birds. The combined probability of exposure and subsequent LPAIV infection via raw table eggs containing LPAIV is negligible for commercial poultry and humans and extremely unlikely to negligible for non-commercial poultry and wild birds. The probability of LPAIV transmission from an individual infected via raw table eggs containing LPAIV is negligible for commercial poultry and humans and very unlikely to negligible for non-commercial poultry and wild birds. Although the presence of LPAIV in raw poultry meat and table eggs is very unlikely to negligible, there is in general a high level of uncertainty on the estimation of the subsequent probabilities of key steps of the transmission pathways for poultry and wild birds, mainly due to the limited number of studies available, for instance on the viral load required to infect a bird via raw poultry meat or raw table eggs containing LPAIV.

The Marmoset as an Animal Model of Influenza: Infection With A(H1N1)pdm09 and Highly Pathogenic A(H5N1) Viruses via the Conventional or Tracheal Spray Route

To control infectious diseases in humans, it is important to understand the pathogenicity of the infecting organism(s). Although non-human primates, such as cynomolgus and rhesus macaques, have been used for influenza virus infection models, their size can limit their use in confined animal facilities. In this study, we investigated the susceptibility of marmosets to influenza viruses to assess the possibility of using these animals as a non-human primate model for influenza research. We first used an influenza A (H1N1)pdm09 virus to compare two inoculation routes: the conventional route, via a combination of the intratracheal, intranasal, ocular, and oral routes; and the tracheal spray route. In marmosets inoculated via the tracheal spray route, we found inflammation throughout the lungs and trachea. In contrast, in marmosets inoculated via the conventional route, the inflammation was confined to roughly the center of the lung. These data suggest that the tracheal spray route may be more suitable than the conventional route to inoculate marmosets with influenza viruses. We also tested an influenza A(H5N1) highly pathogenic avian influenza (HPAI) virus and found that some marmosets inoculated with this virus via the tracheal spray route showed weight loss, decreased body temperature, and loss of appetite and activity. The replication of this H5N1 virus in respiratory organs was confirmed. These results indicate the potential of marmosets as an animal model for infection with seasonal or HPAI viruses.

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.