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Treatment for horses may lead to therapy for type of blindness

Picture a horse running across an open field, the wind blowing his mane, his hooves stamping into the grassy knoll, eyes on the horizon.

Now picture that horse's vision slowly spotting and fading, the horizon blurring, until ultimately, he can't see anything at all.

That's the tragedy that a multidisciplinary team of scientists are trying to prevent. One day, their work may even be helpful for people.

A recent University of Florida study, in Frontiers in Immunology, looked at the potential of an eye drop they developed to treat the sight-robbing disease known as equine recurrent autoimmune uveitis.

Researchers from UF's Institute of Food and Agricultural Sciences (UF/IFAS) microbiology and cell science department, UF College of Veterinary Medicine and College of Medicine ophthalmology department worked together to see if they could restore and protect the vision of horses with this condition.

Uveitis is a leading cause of blindness in horses and in humans. It is responsible for about 10% of blindness and visual handicap in the U.S., which accounts for about 30,000 new cases of blindness each year, according to the Cleveland Clinic.

Uveitis is a serious condition where the uvea, the middle layer of the eye, is inflamed and can cause vision loss in two ways: structures of the eye break down, and light to the retina is blocked. If caught early, medicine can prevent uveitis from causing loss of eyesight, but in more advanced cases, the damage is already done, said Lauren Stewart Stafford, a former UF/IFAS microbiology and cell science Ph.D. student who is now a post-doc at Case Western Reserve University.

The way uveitis affects eyes—and the way the treatment works—is similar in horses and people, said Joseph Larkin, associate professor in the UF/IFAS microbiology and cell science department.

"It turns out that the place where the drug sits to have its effect in the eye is the same in people and in horses," he said. "We think that if we're able to prove its effect in horses, we'll also be able to treat the disease in people. People go blind if they have this disease, so it definitely alters their quality of life permanently."

Traditionally, steroids are the go-to treatment for uveitis, but they aren't a viable long-term solution due to side effects, Larkin said. Since recurrent uveitis keeps coming back after treatment, a more sustainable long-term solution is needed.

The treatment tested in the study took an autoimmune route because in autoimmune uveitis, immune cells are destroying the structures inside the eye, he said.

The drops they developed contained a SOCS1-KIR mimetic peptide, which is a synthetic molecule that mimics a building block of a protein, used in many types of therapies.

A SOCS1-KIR peptide is a Suppressor of Cytokine Signaling (SOCS) 1 Kinase Inhibitory Region (KIR). This is a molecule that regulates chemical messaging between immune cells to reduce inflammatory activity and potentially improve cell communication.

In a prior study by these researchers, the team demonstrated the treatment's effectiveness in horses at UF's College of Veterinary Medicine.

Larkin said that several horses came into the study with a painful sensitivity to light and were either mostly or entirely blind. Several horses improved—they were in less pain and could see more than before.

"Once we reduced the inflammation, one horse was even able to see again," he said.

This study demonstrated possible methods into how the treatment changed the horses' immune response. The next step, Larkin said, would be to do a clinical trial with horses.