Recombinant vaccinia viruses expressing either the premembrane/truncated envelope (PrM/TrE) or truncated envelope (TrE) protein of louping ill virus were constructed. Both constructs expressed authentic E proteins as determined by their size and antigenic reactivity with a panel of monoclonal antibodies. The deletion of the C-terminal hydrophobic domain of the envelope glycoprotein resulted in the secretion of E protein into the supernatant culture medium. The immunisation of mice with these recombinant viruses showed that the recombinant expressing PrM/TrE proteins induced neutralising and protective antibodies against challenge with louping ill or tick-borne encephalitis virus, but that the recombinant expressing the E or the TrE protein alone failed to induce any detectable immune responses against homologous or heterologous virus challenge.