Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2024

Preclinical assessment of a non-M protein group A streptococcal vaccine demonstrating protective efficacy in the non-human primate model of pharyngitis (103532)

Tania Rivera-Hernandez 1 2 , Diane G Carnathan 3 , Nichaela Harbison-Price 2 , Johanna Richter 2 , Maria Lawrenz 4 , Céline Lemoine 4 , Amanda J Cork 2 , Jacelyn MS Loh 5 , Bodie F Curren 2 , Laura Davis 2 , Brody Pullinger 2 , Ruby Pelingon 2 , Stephan Brouwer 2 , Reuben McGregor 5 , Nia Bickham 2 , Gayathiri Elangovan 2 , Miguel Aguirre 2 , Ismail Sebina 6 , Rhiannon A Bolton 6 , Isabel G Courtney 6 , Thomas Proft 5 , Nikki J Moreland 5 , Patrice Dubois 4 , Nicolas Collin 4 , Gabrielle T Belz 6 , Guido Silestri 3 , Mark J Walker 2
  1. Unidad de Investigación Médica en Inmunoquímica, Hospital de Especialidades del Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, Mexico City, Mexico
  2. Australian Infectious Diseases Research Centre and Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
  3. Emory Vaccine Center and Emory National Primate Research Center, Emory University, Atlanta, Georgia, USA
  4. Vaccine Formulation Institute (VFI), Geneva, Switzerland
  5. School of Medical Science, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
  6. Frazer Institute, The University of Queensland, Brisbane, Queensland, Australia

The preferred product characteristics for a Group A Streptococcus (GAS) vaccine, as outlined by the World Health Organization, recommend effective protection against pharyngitis as a relevant and feasible goal for early phase clinical development. The non-human primate (NHP) model of GAS pharyngitis has been used to investigate vaccine immunogenicity and efficacy. However, vaccines currently in preclinical development have yet to demonstrate a reduction in NHP pharyngeal colonisation following GAS challenge. In this study, we employed the NHP pharyngitis model to investigate the efficacy of the preclinical GAS vaccine Combo#5 formulated with the experimental adjuvant SMQ. SMQ is a squalene-in-water emulsion containing the saponin QS21 and the synthetic toll-like receptor 4 ligand 3D(6-acyl)-PHAD®, which elicits a more balanced Th1/Th2-type immune response compared with the clinically approved vaccine adjuvant alum (aluminium hydroxide). Vaccination of NHPs with Combo#5-SMQ resulted in reduced GAS colonisation compared with negative controls. These findings suggest that the Combo#5-SMQ vaccine formulation protects against pharyngeal colonisation and highlights the feasibility of developing a GAS vaccine that blocks colonisation and subsequent disease burden in humans.