Conjunctival infection with SARS-CoV-2 unlikely
SARS-CoV-2 is assumed to use angiotensin-converting enzyme 2 (ACE2) and other auxiliary proteins for cell entry. Recent studies have described conjunctival congestion in 0.8% of patients who have laboratory-confirmed SARS-CoV-2, and there has been speculation that SARS-CoV-2 can be transmitted through the conjunctiva. However, it is currently unclear whether conjunctival epithelial cells express ACE2 and its cofactors.
In this study, a total of 38 conjunctival samples from 38 patients—including 12 healthy conjunctiva, 12 melanoma, seven squamous cell carcinoma, and seven papilloma samples—were analyzed using high-throughput RNA sequencing to assess mRNA expression of the SARS-CoV-2 receptor ACE2 and its cofactors including TMPRSS2, ANPEP, DPP4, and ENPEP. ACE2 protein expression was assessed in eight healthy conjunctival samples using immunohistochemistry.
The study’s results indicate that the SARS-CoV-2 receptor ACE2 is not substantially expressed in conjunctival samples on the mRNA (median 0.0 transcripts per million [TPM], min 0.0 TPM, max 1.7 TPM) and protein levels. Similar results were obtained for the transcription of other auxiliary molecules.
In conclusion, this study finds no evidence for a significant expression of ACE2 and its auxiliary mediators for cell entry in conjunctival samples, making conjunctival infection with SARS-CoV-2 via these mediators unlikely.