RECOGNITION OF FOOT-AND-MOUTH-DISEASE VIRUS AND ITS CAPSID PROTEIN VP1 BY BOVINE PERIPHERAL T-LYMPHOCYTES

The role of T cells in immunity to foot-and-mouth disease virus is sti ll poorly defined compared to that of the humoral response. In this pa per we describe a systematic, longitudinal study on the cellular recog nition of FMDV and its subunit protein VP1 by bovine peripheral blood T lymphocytes. Multiple vaccination with a single virus serotype induc ed a serotype crossreactive proliferative T cell repertoire that varie d in magnitude between individual animals and with the serotype of the vaccine used. Primary proliferative T cell responses of vaccinated an d acutely infected cattle were weak relative to the magnitude of respo nses determined for the same animals after boosting. In contrast, the level of circulating antibody produced after both primary and secondar y exposure to virus was good. Phenotypic analysis of lymphocytes from vaccinated or infected cattle showed a small increase in CD8(+) T cell s after infection compared to vaccination. However, in general the pro files of circulating lymphocytes elicited were similar. Thus, we were not able to use proliferative or phenotypic analyses to distinguish be tween vaccinated and convalescent cattle. T cell recognition of VP1 by multiply-vaccinated cattle was serotype-specific implying that the cr oss-reactive responses observed with whole virus may be attributed to proteins other than VP1. In contrast to other studies, immunization wi th recombinant VP1 induced only low levels of neutralizing antibody an d failed to elicit profound proliferative responses or protection even after two immunizations.