Tracy Shutao Xie, University of Ottawa

Tracy Shutao Xie (University of Ottawa), Claudia Santos Saenz (University of Ottawa), Morgan Jennings (University of Ottawa), Geneviève Laroche (University of Ottawa), Marceline Côté (University of Ottawa)

Breaking & Entering

In 2023, 41 cases of highly pathogenic avian influenza (HPAI) A(H5N5) virus containing a novel 22-aa deletion in the neuraminidase (NA) stalk region were detected in birds and mammals in Atlantic Canada. NA is one of two important influenza A virus surface proteins and is known for facilitating viral egress, but also plays a complementary role to hemagglutinin (HA) during entry. Though NA truncations have been characterized, previous studies are limited to A(H5N1), the dominant subtype of the ongoing HPAI panzootic. A(H5N5) detections remain rare and it is unknown how the Canadian N5 subtype truncation may affect A(H5N5) virulence, transmission, and host tropism. Using a lentiviral pseudotyping system, this project will characterize viral entry and fusion of A(H5N5) expressing short-stalk NA (ssNA) — representative of the 41 Canadian strains — compared to A(H5N5) carrying a mutant long-stalk NA (lsNA). Viral entry will be assessed by exposing target cells expressing avian or human receptors to pseudotypes, followed by flow cytometry quantification. For viral fusion, cells will be transfected with HA and ssNA or lsNA, treated with low pH to induce HA fusion, and imaged for syncytia formation. Preliminary data show that pseudotypes expressing mutant lsNA resulted in lower viral entry compared to wild-type ssNA, regardless of target cell receptor type; this supports the increasingly recognized notion that NA also functions in entry, not just egress. By characterizing a novel HPAI mutation specific to Canada, this project will help shape policies and responses to the ever-growing public health threat posed by HPAI.