Cattle were immunised orally, nasally or subcutaneously with either S. typhimurium 4/74 aroA- aroD- or S. typhimurium 4/74 htrA-based live vaccines expressing Fragment C (TetC) of tetanus toxin from plasmid pTetnir15. Oral inoculation with S. typhimurium 4/74 aroA- aroD-- (pTetnir15) elicited mucosal anti-TetC IgA but no measurable systemic humoral responses to TetC. Subcutaneous inoculation with the same strain elicited both mucosal IgA and systemic anti-TetC IgG1 responses. Nasal inoculation did not elicit any detectable anti-TetC responses. Oral delivery of S. typhimurium htrA- proved fatal in inoculated animals. None of the animals inoculated with either mutant S. typhimurium developed detectable T cell proliferative responses to the guest antigen. Cattle were also inoculated with tetanus toxoid adsorbed in alum or emulsified in Freund's complete adjuvant. Animals inoculated subcutaneously with Ttox emulsified in FCA developed systemic IgG1 and IgG2 antibody, while animals inoculated with Ttox adsorbed in alum developed systemic IgG1 but little IgG2 to Ttox. Both of these groups of animals developed measurable TetC-specific proliferative T cell responses that were associated with the production of IFNγ.