Background: Bordetella pertussis causes whooping cough, the least controlled vaccine-preventable disease in Australia. Since the switch to the acellular vaccine (ACV), Australian epidemic strains changed to single nucleotide polymorphism (SNP) Cluster I from SNP Cluster II. Our previous proteomic analysis identified upregulation of transport proteins and downregulation of immunogenic proteins in the whole cell and secretome of Cluster I which was associated with higher fitness in the mouse model. Additionally, current ACVs have been shown to be less efficacious against current epidemic strains in mice models and there is an ongoing need to discover new antigens to improve the effectiveness of ACVs. One important source of novel antigens is the surfaceome. Therefore, the aim of this study was to establish surface shaving in B. pertussis to compare the surfaceome of SNP Cluster I and II and identify novel surface antigens for vaccine development.
Methods: B. pertussis strains L1423 (SNP Cluster I) and L1191 (SNP Cluster II) were grown in THIJS media. Surface shaving with 1 μg of trypsin for 5 min and LC-MS/MS were used to identify surface proteins. Flow cytometry and CFU were used to assess cell lysis after shaving.
Results and conclusion: Surface shaving identified 666 peptides from 126 proteins with the most abundant being virulence-associated and known outer membrane proteins. The proportion of previously identified immunogenic proteins was significantly higher in the surfaceome than in the whole cell and secretome. Of the 126 proteins, 6 were unique to L1423 including two transport proteins. There were 2 proteins unique to L1191, both of which are immunogenic. Two immunogenic type III secretion system proteins were downregulated in L1423, providing further evidence of proteomic adaptation in Cluster I. This study established the surface saving method for the analysis of B. pertussis surfaceome and identified unknown surface proteins which may be potential vaccine antigens.