34] Use of fusions to viral coat proteins as antigenic carriers for vaccine development

Abstract

Publisher Summary The use of RNA bacteriophage, particularly MS2, for presenting epitopes at the surface of a large nucleic acid-flee virus-like particle is described in this chapter. The production of chimeric virus-like particles (VLPs) depends on finding the sites of insertion for the epitopes of interest that do not disrupt the processing and assembly of the particle and present the new sequence in a defined structural context. For some systems, N- or C-terminal extensions are the preferred location; however, such locations suggest that the epitope might not be constrained at one end. In RNA bacteriophages, the preferred site of insertion is at the top of the N-terminal β -hairpin. Appropriate modification of the recombinant coat protein gene allows insertion to occur between residues G14 and T15, allowing presentation in the context of a surface-accessible constrained loop on every subunit of the VLP. The immunoaffinity chromatography experiments described in the chapter suggest that from the three-dimensional structure of the phage particle, insertion of peptide epitopes within the β hairpin blocks access of the anti- MS2 IgG molecules to their epitopes on the wild-type virus. Because it is important to consider secondary immune responses against the epitope carrier in a vaccine, this result is important because it suggests that with enhanced formulations it would be possible to mask B-cell antigenic carrier sites.