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 attenuated, avirulent strains of Salmonella as carriers of foreign antigens. These recombinant strains can elicit a heterologous immune response when 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 expressed in a Salmonella strain to evaluate its potential to induce a specific immune response to MVE. A synthetic oligonucleotide encoding the B-cell epitope (residues E201-224) of the envelope protein of MVE was inserted into the cloned flagellin gene of the Salmonella strain. The construct was sequenced to ensure correct orientation of the epitope. Expression of the epitope was demonstrated by Western blot analysis and immunogold electron microscopy with monoclonal antibody specific to the epitope. Electron microscopy analysis revealed multiple copies of the 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 the virus in vitro. The significance of this system for engineering vaccines for other medically important flaviviruses is discussed.