Influenza A Virus Challenge Models in Cynomolgus Macaques Using the Authentic Inhaled Aerosol and Intra-Nasal Routes of Infection

Abstract

Non-human primates are the animals closest to humans for use in influenza A virus challenge studies, in terms of their phylogenetic relatedness, physiology and immune systems. Previous studies have shown that cynomolgus macaques (Macaca fascicularis) are permissive for infection with H1N1pdm influenza virus. These studies have typically used combined challenge routes, with the majority being intra-tracheal delivery, and high doses of virus (> 107 infectious units). This paper describes the outcome of novel challenge routes (inhaled aerosol, intra-nasal instillation) and low to moderate doses (103 to 106 plaque forming units) of H1N1pdm virus in cynomolgus macaques. Evidence of virus replication and sero-conversion were detected in all four challenge groups, although the disease was sub-clinical. Intra-nasal challenge led to an infection confined to the nasal cavity. A low dose (103 plaque forming units) did not lead to detectable infectious virus shedding, but a 1000-fold higher dose led to virus shedding in all intra-nasal challenged animals. In contrast, aerosol and intra-tracheal challenge routes led to infections throughout the respiratory tract, although shedding from the nasal cavity was less reproducible between animals compared to the high-dose intra-nasal challenge group. Intra-tracheal and aerosol challenges induced a transient lymphopaenia, similar to that observed in influenza-infected humans, and greater virus-specific cellular immune responses in the blood were observed in these groups in comparison to the intra-nasal challenge groups. Activation of lung macrophages and innate immune response genes was detected at days 5 to 7 post-challenge. The kinetics of infection, both virological and immunological, were broadly in line with human influenza A virus infections. These more authentic infection models will be valuable in the determination of anti-influenza efficacy of novel entities against less severe (and thus more common) influenza infections.

The characteristics of hDPP4 transgenic mice subjected to aerosol MERS coronavirus infection via an animal nose‐only exposure device

“…The exposure device, which exposed only the mouse nose, generated MERS-CoV aerosol particles of 1.27 ± 0.61 μm to infect transgenic mice expressing hDPP4 and simulated the natural route of infection. 21,22…”

Non-human primate orthologues of TMPRSS2 cleave and activate the influenza virus hemagglutinin

“…The experimental infection of macaques with FLUAV results in viral spread and influenza symptoms, which are usually not as pronounced as those observed in human influenza patients [29,30]. Nevertheless, infection of macaques with highly pathogenic FLUAV, the pandemic H1N1 virus of 1918 and H5N1 avian influenza viruses, induces severe disease and the macaque model has been successfully used for vaccine-, treatment-and pathogenesis-studies [31][32][33].…”

Constitutive TRIM22 expression within the respiratory tract identifies tissue-specific and cell-type dependent intrinsic immune barriers to influenza A virus infection

“…In order to determine whether TRIM22 expression increased during infection, we compared healthy macaques with those infected with IAV (A/California/04/2009 (H1N1); Cal). These macaques had previously been shown to be infected and to be undergoing an induced innate immune response at the point of euthanasia [65]. Automated staining and quantitation of sectioned samples demonstrated TRIM22 expression did not increase in the respiratory tract of IAV infected macaques (Fig 1I, J).…”

“…No animals were directly subjected to experimentation as part of this scientific study. All animal tissues were obtained from material produced in previously described experiments [65] with permission from Public Health England (PHE). Procedures associated with this earlier study were approved by the PHE Ethical Review Committee (Porton Down, UK) and authorized under UK Home Office project licence 30/3083.…”

“…Formalin fixed and paraffin embedded tissue samples were processed for haematoxylin and TRIM22 immunohistochemistry (IHC) staining, as previously described [65]. Tissue sections were independently assessed for TRIM22 expression by a qualified pathologist.…”