title: Cell-mediated cytolysis of equine herpesvirus-infected cells by leukocytes from young vaccinated horses.
abstract: The objective of this study was to determine whether the administration of modified-live equine herpesvirus (EHV-1) to young horses with residual maternal antibodies stimulated EHV-specific cytolytic responses, and whether these responses were crossreactive between EHV-1 and EHV-4. Eighteen clinically normal Belgian cross-foals were used in the study and were commingled in two adjacent pens. Skin biopsies were harvested from 16 foals within 24 h of birth and fibroblast cultures were established, expanded and cryopreserved. Beginning at approximately 10 weeks of age, 10 randomly chosen foals were inoculated on days 0, 21, and 43 of the study with a vaccine containing modified-live EHV-1. Blood mononuclear leukocytes were obtained on days 0, 32, and 50 for the assessment of EHV-specific cytolytic activity using 5 h and 18 h chromium release assays. EHV-1-specific antibodies were assessed by enzyme-linked immunosorbent assay using serum collected on days -21, 0, 32, and 50 of the study. Lymphocyte blastogenic tests and bioassays for interferon activity were conducted on day 50. After two vaccinations, mononuclear leukocytes from seven of ten vaccinated foals had cytolytic activity against autologous EHV-1 cells and leukocytes from six of ten lysed EHV-4-infected cells when tested in an 18 h assay. This activity was enhanced by exogenous interleukin 2 and was markedly reduced using target cells from unrelated horses. Cytotoxicity was not detected in a 5 h assay following in vitro stimulation of leukocytes. After three vaccinations, blood leukocytes from 6/6 vaccinated foals and 0/6 unvaccinated foals had proliferative responses EHV-1. There were no significant differences in interferon production by leukocytes from these foals. Twelve foals tested had low concentrations of (maternal) EHV-1-specific antibody prior to vaccination. Five of eight foals tested had increases in EHV-specific antibodies, while 4/4 commingled unvaccinated foals had a decrease or no change in EHV-specific antibodies. These results demonstrate cytotoxic cellular immune responses can be induced in young horses with maternal antibodies following administration of modified-live vaccine.
authors.affiliation: Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, Canada.
authors.forename: J A
authors.initials: JA
authors.lastname: Ellis
authors.forename: E
authors.initials: E
authors.lastname: Steeves
authors.forename: A K
authors.initials: AK
authors.lastname: Wright
authors.forename: J R
authors.initials: JR
authors.lastname: Bogdan
authors.forename: W C
authors.initials: WC
authors.lastname: Davis
authors.forename: E W
authors.initials: EW
authors.lastname: Kanara
authors.forename: D M
authors.initials: DM
authors.lastname: Haines
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000096:biosynthesis / Q000276:immunology; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D005347:Fibroblasts / Q000276:immunology / Q000821:virology; D006566:Herpesviridae Infections / Q000276:immunology* / Q000662:veterinary*; D004861:Herpesvirus 1, Equid / Q000276:immunology*; D006734:Horse Diseases / Q000276:immunology*; D006736:Horses; D007111:Immunity, Cellular; D016130:Immunophenotyping / Q000662:veterinary; D007372:Interferons / Q000096:biosynthesis; D007963:Leukocytes, Mononuclear / Q000276:immunology / Q000821:virology; D008213:Lymphocyte Activation; D011897:Random Allocation; D014765:Viral Vaccines / Q000276:immunology*
chemical_list: D000914:Antibodies, Viral; D014765:Viral Vaccines; D007372:Interferons