SARS-CoV-2 Entry Factors Expressed in Ocular Tissue

Aged woman looking through optometry in hospital
Wrinkled senior female looking through lens while wearing protective face mask. Aged woman is sitting behind optometry in doctor’s office. She is in hospital for eye exam during COVID-19 pandemic.
A study advises proper eye protection in certain circumstances can help avoid COVID-19 infection.

Two proteins key to SARS-CoV-2 infection are expressed on nasal, ocular, and oral epithelial surfaces, with nasal motile cilia particularly primed to encounter SARS-CoV-2 during viral transmission, according to a research team’s submission to The Journal of Allergy and Clinical Immunology. 

According to researchers, tissue tropism is “one key to understanding the pathogenesis of SARS-CoV-2.” To gain insights into the initial SARS-CoV-2-host interactions, researchers sought to characterize the protein expression of angiotensin-converting enzyme 2 (ACE2) and transmembrane protease, serine 2 (TMPRSS2), an essential protein and entry factor for the disease. 

Investigators performed immunofluorescent staining on tissue microarrays, including normal human head and neck tissues. Tissue samples from people who had died from SARS-CoV-2 infections were collected during autopsy. 

Results indicated that both ACE2 and TMPRSS2 protein expressions localize to “a variety of human airway, ocular, and oral epithelial surfaces,” which suggests that the SARS-CoV-2 virus is capable of entering the body through all facial mucosal surfaces. In particular, these proteins are both “highly expressed” in nasal mucosa motile cilia, and investigators found SARS-CoV-2 spike transcripts in the nasal epithelia of patients who were infected. 

“Prophylaxes and therapeutics for COVID-19 should…focus on a nasal route of administration,” the research concludes. “Similarly, proper eye protection should be worn during certain circumstances.”


Lee I, Nakayama N, Jiang S, et al. SARS-CoV-2 entry factors are expressed in nasal, ocular, and oral tissues: Implications for COVID-19 prophylaxes/therapeutics. J Allergy Clin Immunol. Published online February 1, 2021. doi:10.1016/j.jaci.2020.12.055