Research: EVH-1 Can Activate Platelets and Blood Clots Form

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Editor's Note: Veterinary clinical pathologist Tracy Stokol, BVSc, PhD, of Cornell University is researching how equine herpesvirus-1 affects platelets and what that means to blood clotting in affected animals. Grayson-Jockey Club Research Foundation is funding further research into this area of EHV-1. The following information is from Cornell University.

Equine herpesvirus type I (EHV1) frequently infects horses and is a common cause of respiratory disease, particularly in younger animals. However, in pregnant mares and some older horses, EHV1 enters into the blood, which spreads the infection to the placenta or the spinal cord. Infection of these tissues can result in abortion and a neurologic disease, called equine herpesvirus myeloencephalopathy or EHM. EHM can cause staggering, paralysis and incontinence which, even if mild, can prevent a horse from racing again. In some horses, the disease is so severe, the most humane option is to put the horse down. Horses with EHV1 suffer from abortion and EHM because blood clots form in the vessels that feed the placenta and spinal cord. These clots choke off the blood supply and deprive cells of vital oxygen and nutrients, thus damaging the tissue, sometimes beyond repair. We currently do not know why clots form and consequently do not treat horses with any drugs that could prevent clots from occurring. Platelets are small cells that circulate in blood and are essential for clotting. Clots actually form on the lipid surface of platelets, but only once platelets have been activated. These activated platelets express clot promoting lipids and release small lipid rich particles (microparticles) from their surfaces. These platelet lipids and lipid rich particles provide the surface on which clots form and help clots grow rapidly so that they block a blood vessel. We have exciting novel preliminary results showing that EHV1 activates platelets and causes the expression and release of clot forming lipids from platelets, thus turning the platelet into a potent clot forming agent. We also have results showing that these activated platelets can carry EHV1 infection to blood vessel lining cells cultured in the laboratory, which would help clots form right on the blood vessel surface. We hypothesize that platelets are activated inside the horse’s bloodstream after the horse is infected with EHV1 and that we could block this effect using specific anti platelet drugs, that are already available but not currently used for this purpose.

The principal investigator into this research is Stokol of Cornell's Department of Population Medicine and Diagnostic Sciences. Her email: ts23@cornell.edu; her phone is 607-253-3255. The title of her project is: Platelet Inhibitors: Potential Antithrombotics for EHV-1, which is being funded for $68,368. The project period is from April 1, 2014, until March 31, 2015.