Ebola virus: what happens in the eyes of those who have had the disease?

Three years after the Ebola epidemic hit West Africa, researchers have begun to understand how the virus remains viable for up to one year after infection in the eyes of survivors who develop a form of uveitis. About one in four of the survivors to the Ebola epidemic, which developed in Sierra Leone, suffers from a type of uveitis that is one of the most serious and common complications of the infection and can lead to partial or total loss of vision.

A recent study published in Translational Vision Science & Technology (TVST) describes how the cells underlying the immune privileges enjoyed by the eye are also responsible for the lack of virus clearance from infected tissue. The study explains that the general mechanisms that allow the Ebola virus to persist within the body after recovery from acute infection involve interactions between the virus and host cells such as: moderate virus replication and/or limited immune response to the virus. In fact, the eye is characterised by a privilege of immunityi.e. the ability to limit inflammation, and the monolayers of pigmented epithelial cells are the key components of this ocular immune privilege. These cells are in fact rich in membrane ligands and soluble factors that inhibit inflammatory activity of leucocytes; however, by limiting the immune response, ocular pigment epithelial cells can also promote the persistence of micro-organisms in the eye.

The team of researchers introduced live Ebola virus into Retinal Pigmented Epithelium (EPR) cells, and the scientists observed that the virus easily replicated in the cells while they continued to perform their function of expressing molecules that limit the immune system's ability to fight infection. The resulting weak immune response could be responsible for the persistence of the live virus in the eye.

The study, while explaining how the eye can become a reservoir for Ebola and lays the foundations for a greater understanding of post-Ebola eye disease, on the other hand it opens the door to numerous questions and research insights among which the main one could be: why do some disease survivors carry the virus and develop uveitis and others do not?

Bibliography

Smith JR et al. Translational Vision Science & Technology, 2017;6(4): 12.

Dr. Carmelo Chines
Direttore responsabile