IN-VITRO CYTOTOXIC ACTIVITY OF EQUINE LYMPHOCYTES ON EQUINE HERPESVIRUS-1 INFECTED ALLOGENIC FIBROBLASTS

The objectives of this study were to: (1) develop a technique to analy ze the in vitro cytotoxic activity of lymphocytes from adult horses ag ainst equine herpesvirus-1 (EHV-1) infected allogenic equine dermal fi broblasts (EDF); (2) evaluate the ability of a 72-h in vitro incubatio n with interleukin-2 (IL-2) to enhance the lymphocytic cytolytic activ ity against EHV-1 infected EDF; (3) compare the cytotoxic activity of lymphocytes isolated from pregnant mares and non-pregnant mares agains t EHV-1 infected EDF; (4) ascertain if any correlations existed betwee n the percent cytotoxicity and percentage of lymphocytes phenotypicall y identified by five different mouse-anti-equine monoclonal antibodies ; and (5) determine if any correlation existed between virus-neutraliz ing antibody titers and the percent cytotoxicity. Results of the study indicate that in vitro cytotoxic activity of equine lymphocytes again st EHV-1 infected allogenic fibroblasts can be measured with a standar d 4-h Cr-51 release assay. This activity was enhanced by an in vitro i ncubation with IL-2. The cytolytic activity of freshly isolated lympho cytes was greater for non-pregnant than pregnant mares. However, after IL-2 stimulation the cytolytic activity was greater for lymphocytes f rom pregnant mares. A positive correlation was not detected between th e percentage of phenotypically identified cells and the percent cytoto xicity, although several negative correlations were present. This sugg ests that the cytotoxic activity was either not mediated by any of the phenotypically identified cell populations or that the activity was m ediated by several different cell populations. No correlation was dete cted between virus-neutralizing antibody titers and the percent cytoto xicity.