Role of H7 hemagglutinin in murine infectivity of influenza viruses following ocular inoculation

- Influenza viruses can cause conjunctivitis in humans.
- A murine ocular inoculation model facilitates the study of ocular infectivity.
- Virulence determinants were studied for their association with ocular infection.
- H7 subtype viruses exhibit a strong ocular tropism in this model.

H7 subtype influenza viruses have demonstrated an ocular tropism in humans, causing conjunctivitis and not respiratory symptoms in many infected individuals. However, the molecular determinants which confer ocular tropism are still poorly understood. Here, we used a murine model of ocular inoculation to demonstrate that H7 influenza viruses are more likely to cause infection following ocular exposure than are non-H7 subtype viruses. We included investigation regarding the potential role of several properties of influenza viruses with murine infectivity following ocular inoculation, including virus lineage, pathogenicity, and HA cleavage site composition. Furthermore, we examined the potential contribution of internal proteins to murine ocular infectivity. These studies establish a link between H7 subtype viruses and the risk of heightened infectivity in a mammalian species following ocular exposure, and support the development of non-traditional inoculation methods and models to best understand the human risk posed by influenza viruses of all subtypes.