IMMUNE-RESPONSE TO A MURRAY VALLEY ENCEPHALITIS-VIRUS EPITOPE EXPRESSED IN THE FLAGELLIN OF AN ATTENUATED STRAIN OF SALMONELLA

Recent developments in vaccine construction include the use of attenua ted, avirulent strains of Salmonella as carriers of foreign antigens. These recombinant strains can elicit a heterologous immune response wh en injected into animals, demonstrating potential for their use in the construction of many vaccines. In the present study, a B-cell epitope of Murray Valley encephalitis virus (MVE) was identified and expresse d in a Salmonella strain to evaluate its potential to induce a specifi c immune response to MVE. A synthetic oligonucleotide encoding the B-c ell epitope (residues E(201-224)) of the envelope protein of MVE was i nserted into the cloned flagellin gene of the Salmonella strain. The c onstruct was sequenced to ensure correct orientation of the epitope. E xpression of the epitope was demonstrated by Western blot analysis and immunogold electron microscopy with monoclonal antibody specific to t he epitope. Electron microscopy analysis revealed multiple copies of t he epitope along the flagella. The recombinant Salmonella carrying the hybrid flagellin gene elicited an immune response to the MVE epitope in a mouse model, The MVE-specific antibodies partially neutralised th e virus in vitro. The significance of this system for engineering vacc ines for other medically important flaviviruses is discussed.