CD4(+) T-cell responses to bovine viral diarrhoea virus in cattle

Friesian calves were infected with one of three isolates of bovine viral di arrhoea virus (BVDV) and used to establish parameters for an in vitro model of BVDV-reactive T-cell responses in cattle. The study assessed virus clea rance, seroconversion, maturation of lymphoproliferative responses (both du ring and following disease resolution) and the antigen-specificity of CD4() T cells from recovered animals. Seroconversion and virus-specific lymphop roliferation were not detected until viraemia had resolved. Interestingly, lymphoproliferation was detected earlier in the animals infected with cytop athic viruses than in those infected with noncytopathic virus despite broad ly similar rates of virus clearance and seroconversion for both biotypes. C D4(+) and CD8(+) T cells were induced to proliferate by virus-infected stim ulator cells whereas only CD4(+) T cells responded to non-infectious antige ns. Lymphoproliferation was strain cross-reactive and MHC-restricted. Induc tion of T-cell proliferation by recombinant proteins identified the major e nvelope proteins E-rns and E2 and the nonstructural (NS) 2-3 protein as T-c ell determinants. In addition, the capsid (C) and/or the amino-terminal pro teinase, N-pro were identified as T-cell determinants from the responses of short-term T-cell lines. Thus, in this model, the CD4(+) T-cell repertoire induce by acute BVDV infection includes at least the major envelope protei ns, NS2-3, and capsid and/or N-pro. (C) 2000 Elsevier Science B.V. All righ ts reserved.