Specific cells in the eye are infected with Covid-19

You can contract the SARS-CoV-2 virus through the eye – this is probably something that many of us thought was a proven fact. However, with the present study this statement has only just been shown probable.

Postdoc Anne Zebitz Eriksen, who is currently visiting at Icahn School of Medicine at Mount Sinai, has investigated the possibility of contracting the SARS-CoV-2 virus that causes COVID-19, through the eye together with colleagues at the university.

Anne Zebitz Eriksen explains: “The eye represents an exposed surface layer with a mucosal tear film similar to the surface layer of the lung, and it is important to know if the virus can spread through this route, to be able to take the right preventive measures to reduce the spread of the virus.”

The research team analysed donor eyes from patients, who had died while positive for Covid-19. They found that specific cells in the eye were infected, namely the surface epithelium of the cornea and the limbus tissue at the very edge of the cornea, where it connects to the white part of the eye (the sclera). And two specific receptors, ACE2 and TMPRSS2, which are responsible for SARS-CoV-2 entry into cells, were also highly represented.

Further tests were done on cells from non-infected donor eyes to check for the two entry factors and to investigate if the cells could be infected with the virus. Results showed that the entry factors, ACE2 and TMPRSS2 that interact with the spike protein on the viral surface, were present in all types of tissues tested, but significantly higher in the limbus. When the cells were exposed to the SARS-CoV-2 virus all the tissue types tested got infected, but the limbus cells showed a higher viral replication than the cornea and the sclera - the white part of the eye.

For the first time, an eye organoid model, i.e. a model of the eye grown from stem cells, was used to investigate the SARS-CoV-2 virus.

“We saw that the model eye got infected and that the virus was replicating in the eye-model cells. Further investigations revealed that a small subset of the cells representing the limbus, were the cells that predominately was infected with SARS-CoV-2” Anne Zebitz Eriksen says. She continues “Remarkably, the eye organoid model show that even though all cells are exposed to the virus, then it is mainly one type of cells that become infected, this tells us that these cells must be especially vulnerable in terms of contact transmission for some reason.”

In conclusion, even though this study cannot finally conclude that it is possible to contract the SARS-CoV-2 virus through the eyes, it certainly shows that the eye very much is a potential entryway for the virus, and that protecting the eye surface from exposure to the virus e.g., by wearing face-shields or glasses, is a valid protective measure.

Read the full scientific paper in Cell - Stem Cell: “SARS-CoV-2 infects human adult donor eyes and hESC-derived ocular epithelium”.