PURPOSE To confirm the ocular tropism of SARS-CoV-2 by evaluating expression of viral entry factors in human ocular tissues using immunohistochemistry. METHODS Fresh donor corneas and primary explant cultures of corneal, limbal, and conjunctival epithelial cells were evaluated for expression of viral entry factors. Using immunohistochemistry, samples were tested for expression of angiotension-converting enzyme 2 (ACE2), dendritic cell-specific intracellular adhesion molecule-3-grabbing non integrin (DC-SIGN), DC-SIGN-related protein (DC-SIGNR), and transmembrane serine protease 2 (TMPRSS2). RESULTS In total, five donor corneas were evaluated for expression of viral entry factors. In all specimens, both ACE2 and TMPRSS2 were expressed throughout the surface epithelium (corneal, limbal, and conjunctival) and corneal endothelium. In corneal stromal cells, ACE2 was sporadically expressed while TMPRSS2 was absent. DC-SIGN/DC-SIGNR expression varied between donor specimens. Four specimens expressed DC-SIGN/DC-SIGNR in a similar distribution to ACE2, but one specimen from a young donor showed no expression of DC-SIGN/DC-SIGNR. ACE2, TMPRSS2, and DC-SIGN/DC-SIGNR were all expressed in cultured corneal, limbal, conjunctival epithelial cells. CONCLUSIONS Both corneal and conjunctival epithelium express ACE2, DC-SIGN/DC-SIGNR, and TMPRSS2 suggesting that the ocular surface is a potential route for transmission of SARS-CoV-2. The risk of viral transmission with corneal transplantation cannot be ruled out given the presence of ACE2 in corneal epithelium and endothelium. Cultured corneal, limbal, and conjunctival epithelial cells mimic the expression of viral entry factors in fresh donor tissue and may be useful for future in vitro SARS-CoV-2 infection studies.
Immunohistochemical study of SARS-CoV-2 viral entry factors in the cornea and ocular surface.