S213P in the non-structural protein 1 of subtype H1N1 avian influenza A viruses mediates airborne transmissibility in the ferret model.

Abstract

<p>The non-structural protein 1 (NS1) of influenza A viruses is a multifunctional protein that produces an environment conducive to influenza virus replication by facilitating viral genome replication and antagonizing host antiviral responses. Our previous studies of shorebird-isolated subtype H1N1 avian influenza A viruses (AIVs) revealed a role for NS1 in airborne transmission in a ferret model of human influenza virus transmission. They also revealed that a single mutation, S213P, in the NS1 of these viruses abrogated airborne transmission, although the host responses that were determinants of airborne transmissibility were unknown. Here, we studied the host pathology and transcriptomic responses in ferret nasal turbinates following infection with A/ruddy turnstone/Delaware/300/2009 (H1N1) (DE300), an AIV that is airborne transmissible in the ferret model, and DE300 that contains NS1 S213P as a loss-of-function mutation. S213P was associated with reduced pathology in the respiratory epithelium of the ferret upper respiratory tract, the determinant anatomic site of influenza virus airborne transmission. This reduced tissue pathology was associated with an almost absence of cellular debris and exudate that stained for influenza virus antigen in the airways of the nasal epithelium, which was abundant in animals infected with airborne transmissible AIVs. Transcriptomic studies of the nasal epithelium of infected ferrets revealed that S213P led to upregulation of pathways regulating the innate immune response and cell fate by apoptosis, rather than inflammatory-mediated cell death associated with airborne-transmissible AIVs. Our findings suggest that these responses underlie the formation of debris in the nasal cavity that stain for influenza virus antigen and likely mediate the formation of virus-laden particles that mediate airborne transmission. Overall, this study indicates that NS1 is an important mediator of the host responses in the upper respiratory tract underlying airborne transmission.</p>