Purpose: The spike proteins of SARS-CoV-2 interact with ACE2 or basigin/CD147 receptors, regulating human-to-human transmissions of COVID-19 together with serine protease TMPRSS2. The expression of these receptors on the ocular surface is unknown.
Material and methods: Gene expression of SARS-CoV-2 receptors was investigated in conjunctival epithelial cell samples and in ex-vivo cornea samples using microarray or transcriptome sequencing.
Results: ACE2 is expressed in conjunctival samples at a low level, while BSG and TMPRSS2 are expressed at intermediate levels in both conjunctiva and cornea. Other receptors such as ANPEP, AGTR2 are expressed at low level in the conjunctiva. Two RNA editing enzymes involved in antiviral responses, APOBEC3A, and ADAR-1 were also highly expressed.
Conclusions: The ocular surface may represent an entry point for the SARS-CoV-2 in the human body. The conjunctiva and the cornea can adopt antiviral countermeasures which may explain the low prevalence of eye involvement.
Keywords: ACE2; ADAR; APOBEC3; CD147; COVID-19; SARS-CoV-2; TMPRSS2; conjunctiva; cornea.