A rapid approach for linear epitope profiling of a Streptococcus A vaccine candidate

Abstract

The creation of effective vaccines is a pinnacle achievement of humankind, with the maintenance and expansion of the current repertoire being crucial in supporting human health and well-being globally. Nevertheless, identification of the mechanisms responsible for protection from infection and disease remains difficult, hindering vaccine candidate progression. These factors illustrate the importance of developing a wide range of techniques available to identify and investigate potential antigens. Current tools for assessing antigen-antibody interactions, although hugely valuable, possess limitations in accessibility and throughput which this research aimed to address.

To implement an accessible rapid protocol that profiles the antibody response to linear epitopes after immunisation, we utilised phage display in conjunction with Nanopore Sequencing. A Group A Streptococcus vaccine candidate, TeeVax3, was selected as a model to explore the binding antibody population produced from immunisation and evaluate the immunogenicity of the antigen. Production of a phage library expressing overlapping TeeVax3 peptides was panned against TeeVax3 specific polyclonal antibodies from rabbits, revealing an unexpected bias for the N terminal epitope tag. Further investigation confirmed the immunogenicity of this region for both linear and conformational antibodies, with an epitope of 10- residues being identified via evaluation of binding with synthetic peptides. Although removal of purification tags is inconsistent, particularly in early stages of vaccine development, these findings illustrate the importance of doing so to ensure relevant immune responses are observed. Other potential areas of immunogenicity on the antigen were able to be observed by excluding the N-terminal region dominating the response, verifying the methods potential for evaluating vaccine candidates. The protocol presented here outlines a valuable addition to the toolkit for development of vaccine candidates, which could be easily adapted to a wide range of antigens and correlating antibody responses.