Heterotypic recognition of foot-and-mouth disease virus by cattle lymphocytes

Vaccine Research Department, AFRC Institute for Animal Health, Pirbright Laboratory, Ash Road, Pirbright, Surrey GU24 0NF, U.K. Lymphoproliferation against foot-and-mouth disease (FMD) virus was examined using peripheral blood mononuclear cells from vaccinated cattle. Ten weeks after revaccination the optimum conditions for proliferation were obtained with 1 µg/ml of purified virus after 5 to 6 days in culture. This contrasted with the response at 20 months post-revaccination, when the response required less antigen and showed a peak response after 3 to 4 days in culture. Proliferation was specific for FMD virus, but was cross-reactive between serotypically distinct strains of the virus. The proliferative response to isolated virus proteins (VP) involved all three major capsid proteins (VP1, -2 and -3), although the proliferation of lymphocytes from hetero-typically vaccinated cattle was due to VP3. Furthermore, the response induced by purified virus, chemically fixed virus and subunit virus particles was indistinguishable and thus it is likely that processing was required for the induction of proliferation. Together these data strongly suggest that FMD virus-induced lymphoproliferation is T cell-mediated and that VP3 may contain dominant, cross-reactive sequences. Received 29 June 1989; accepted 26 September 1989.