Although influenza viruses typically cause respiratory tract disease, some viruses, particularly those with an H7 hemagglutinin, have been isolated from the eyes of conjunctivitis cases. Previous work has shown that isolates of multiple subtypes from both ocular and respiratory infections are capable of replication in human ex vivo ocular tissues and corneal or conjunctival cell monolayers, leaving the determinants of ocular tropism unclear. Here, we evaluated the effect of several variables on tropism for ocular cells cultured in vitro and examined the potential effect of the tear film on viral infectivity. All viruses tested were able to replicate in primary human corneal epithelial cell monolayers subjected to aerosol inoculation. The temperature at which cells were cultured postinoculation minimally affected infectivity. Replication efficiency, in contrast, was reduced at 33°C relative to that at 37°C, and this effect was slightly greater for the conjunctivitis isolates than for the respiratory ones. With the exception of a seasonal H3N2 virus, the subset of viruses studied in multilayer corneal tissue constructs also replicated productively after either aerosol or liquid inoculation. Human tears significantly inhibited the hemagglutination of both ocular and nonocular isolates, but the effect on viral infectivity was more variable, with tears reducing the infectivity of nonocular isolates more than ocular isolates. These data suggest that most influenza viruses may be capable of establishing infection if they reach the surface of ocular cells but that this is more likely for ocular-tropic viruses, as they are better able to maintain their infectivity during passage through the tear film.

IMPORTANCE The potential spread of zoonotic influenza viruses to humans represents an important threat to public health. Unfortunately, despite the importance of cellular and tissue tropism to pathogenesis, determinants of influenza virus tropism have yet to be fully elucidated. Here, we sought to identify factors that limit the ability of most influenza viruses to cause ocular infection. Although ocular symptoms in humans caused by avian influenza viruses tend to be relatively mild, these infections are concerning due to the potential of the ocular surface to serve as a portal of entry for viruses that go on to establish respiratory infections. Furthermore, a better understanding of the factors that influence infection and replication in this noncanonical site may point toward novel determinants of tropism in the respiratory tract.

尽管流感病毒通常会引起呼吸道疾病，但已从结膜炎病例的眼中分离出了某些病毒，尤其是带有H7血凝素的病毒。先前的工作表明，来自眼和呼吸道感染的多种亚型分离株能够在人离体眼组织和角膜或结膜细胞单层中复制，因此尚不清楚眼向性的决定因素。在这里，我们评估了几个变量对体外培养的眼细胞向性的影响并研究了泪膜对病毒感染性的潜在影响。测试的所有病毒都能够在经过气溶胶接种的人类原始角膜上皮细胞单层中复制。接种后培养细胞的温度对感染性的影响最小。相比之下，在33°C时的复制效率相对于在37°C时降低了，对于结膜炎分离株，这种效果比对呼吸道分离株的效果稍大。除季节性H3N2病毒外，在多层角膜组织构建物中研究的病毒子集在气雾剂或液体接种后也能高效复制。人的眼泪显着抑制了眼和非眼分离株的血凝反应，但对病毒感染性的影响更大，眼泪比眼分离株更能减少非眼分离株的传染性。这些数据表明，大多数流感病毒如果到达眼细胞表面就可能能够感染，但对亲眼性病毒则更有可能，因为它们能够更好地在通过泪膜的过程中保持感染力。

重要性人畜共患流感病毒可能传播给人类，这是对公共卫生的重要威胁。不幸的是，尽管细胞和组织趋向性对发病机理很重要，但流感病毒趋向性的决定因素尚未得到充分阐明。在这里，我们寻求确定限制大多数流感病毒引起眼部感染的能力的因素。尽管由禽流感病毒引起的人类眼部症状往往相对较轻，但由于眼表有可能充当继续建立呼吸道感染的病毒的入口，因此这些感染令人担忧。此外，对影响该非典型部位感染和复制的因素的更好理解可能指向呼吸道嗜性的新决定因素。