Study Reveals Eye's Surprising Defense Against Brain Infections

In a study published in the journal Nature, researchers have found that vaccines injected into the eyes of mice can effectively combat the herpes virus, a leading cause of brain encephalitis. Contrary to expectations, the vaccine triggers an immune response via lymphatic vessels along the optic nerve, illuminating a previously unrecognized pathway for immunological interactions between the brain and eyes.

Shared Immune Response: Understanding the Brain-Eye Connection

"There is a shared immune response between the brain and the eye," explains Eric Song, an associate research scientist at Yale School of Medicine's Department of Immunobiology and the paper's corresponding author. "And the eyes provide easier access for drug therapies than the brain does."

Insights into Eye's Defense Mechanisms

Delving into the immunological connections between the brain and eyes, Song's research team discovered two distinct lymphatic systems governing immune responses in different regions of the eye. Following vaccination with inactivated herpes virus, they observed that lymphatic vessels in the optic nerve sheath at the rear of the eye not only shielded mice from active herpes infections but also offered protection against bacteria and brain tumors.

Promising Therapeutic Approaches

Leveraging these newfound insights, Song's team is currently evaluating novel drugs developed in their lab, administered through eye injections. These drugs hold promise for addressing conditions such as macular edema and leaky blood vessels of the retina, commonly associated with diabetes and glaucoma.

"These results reveal a shared lymphatic circuit capable of mounting a unified immune response between the posterior eye and the brain, highlighting an understudied immunological feature of the eyes and opening up the potential for new therapeutic strategies in ocular and central nervous system diseases," the authors note.

Co-lead authors of the study include Xiangyun Yin, an associate researcher in Yale's Department of Immunobiology; Sophia Zhang, an undergraduate student at Yale College; and Ju Hyun Lee, a doctoral student in the Department of Biomedical Engineering.

Reference

Eric Song, Compartmentalized ocular lymphatic system mediates eye–brain immunity, Nature (2024)