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). The cellular immune response against FMDV in this experimental animal is unknown and was analyzed by in vivo and in vitro studies. In guinea pigs immunized with an FMDV A5 vaccine, a marked change in T-lymphocyte 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-positive and, therefore, helper cells. T-cells from these animals were re-stimulated in vitro with homologous inactivated virus. The antigen-specific proliferative response of the T-cells in vitro was measured using the thymidine incorporation assay. A proliferative response to FMDV was observed that depended on the dose of the antigen. High concentration 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.