title: Horses experimentally infected with Sarcocystis neurona develop altered immune responses in vitro.
abstract: Equine protozoal myeloencephalitis (EPM) due to Sarcocystis neurona infection is 1 of the most common neurologic diseases in horses in the United States. The mechanisms by which most horses resist disease, as well as the possible mechanisms by which the immune system may be suppressed in horses that develop EPM, are not known. Therefore, the objectives of this study were to determine whether horses experimentally infected with S. neurona developed suppressed immune responses. Thirteen horses that were negative for S. neurona antibodies in serum and cerebrospinal fluid (CSF) were randomly assigned to control (n = 5) or infected (n = 8) treatment groups. Neurologic exams and cerebrospinal fluid analyses were performed prior to, and following, S. neurona infection. Prior to, and at multiple time points following infection, immune parameters were determined. All 8 S. neurona-infected horses developed clinical signs consistent with EPM, and had S. neurona antibodies in the serum and CSF. Both infected and control horses had increased percentages (P < 0.05) of B cells at 28 days postinfection. Infected horses had significantly decreased (P < 0.05) proliferation responses as measured by thymidine incorporation to nonspecific mitogens phorbol myristate acetate (PMA) and ionomycin (I) as soon as 2 days postinfection.
authors.affiliation: Department of Large Animal Clinical Sciences, Phase II, Duck Pond Dr., Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia 24061-0442, USA. switonsk@vt.edu
authors.forename: Sharon G
authors.initials: SG
authors.lastname: Witonsky
authors.forename: Siobhan
authors.initials: S
authors.lastname: Ellison
authors.forename: Jibing
authors.initials: J
authors.lastname: Yang
authors.forename: Robert M
authors.initials: RM
authors.lastname: Gogal
authors.forename: Heather
authors.initials: H
authors.lastname: Lawler
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Namalwar
authors.initials: N
authors.lastname: Sriranganathan
authors.forename: Frank
authors.initials: F
authors.lastname: Andrews
authors.forename: Daniel
authors.initials: D
authors.lastname: Ward
authors.forename: David S
authors.initials: DS
authors.lastname: Lindsay
mesh_terms: D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D004679:Encephalomyelitis / Q000276:immunology / Q000469:parasitology / Q000662:veterinary*; D005260:Female; D005434:Flow Cytometry / Q000662:veterinary; D006734:Horse Diseases / Q000276:immunology* / Q000469:parasitology; D006736:Horses; D007371:Interferon-gamma / Q000096:biosynthesis; D007962:Leukocytes / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D011897:Random Allocation; D012522:Sarcocystis / Q000276:immunology*; D012523:Sarcocystosis / Q000276:immunology / Q000662:veterinary*
chemical_list: D007371:Interferon-gamma