T-LYMPHOCYTE RESPONSES IN GUINEA-PIGS VACCINATED WITH FOOT-AND-MOUTH-DISEASE VIRUS

The guinea pig provides an alternative experimental model for analysis of the immune response against foot-and-mouth disease virus (FMDV). T he cellular immune response against FMDV in this experimental animal i s unknown and was analyzed by in vivo and in vitro studies. In guinea pigs immunized with an FMDV A(5) vaccine, a marked change in T-lymphoc yte count appeared. For analyzing which functional T-cell compartment was affected, immunofluorescence studies, using monoclonal antibodies directed against differentiation antigens on guinea pig lymphoid cells , were performed. The proliferating T-cells were predominantly CD4-pos itive and, therefore, helper cells. T-cells from these animals were re -stimulated in vitro with homologous inactivated virus. The antigen-sp ecific proliferative response of the T-cells in vitro was measured usi ng the thymidine incorporation assay. A proliferative response to FMDV was observed that depended on the dose of the antigen. High concentra tion of virus had an inhibitory effect on T-cell proliferation. These data indicate that the guinea pig is a useful model for analysis of T- cell mediated mechanisms in the pathogenesis and immunity of foot-and- mouth disease.