Pre-Absorbed Immunoproteomics: A Novel Method for the Detection of Streptococcus suis Surface Proteins

Wei Zhang,Fang Tang,Guangjin Liu,Jing Shao,Yan Lu,Chengping Lu,Huochun Yao,Yinli Bao,Tjeerd Kimman

doi:10.1371/journal.pone.0021234

Abstract

Streptococcus suis serotype 2 (SS2) is a zoonotic pathogen that can cause infections in pigs and humans. Bacterial surface proteins are often investigated as potential vaccine candidates and biomarkers of virulence. In this study, a novel method for identifying bacterial surface proteins is presented, which combines immunoproteomic and immunoserologic techniques. Critical to the success of this new method is an improved procedure for generating two-dimensional electrophoresis gel profiles of S. suis proteins. The S. suis surface proteins identified in this study include muramidase-released protein precursor (MRP) and an ABC transporter protein, while MRP is thought to be one of the main virulence factors in SS2 located on the bacterial surface. Herein, we demonstrate that the ABC transporter protein can bind to HEp-2 cells, which strongly suggests that this protein is located on the bacterial cell surface and may be involved in pathogenesis. An immunofluorescence assay confirmed that the ABC transporter is localized to the bacterial outer surface. This new method may prove to be a useful tool for identifying surface proteins, and aid in the development of new vaccine subunits and disease diagnostics.

Highlights

Streptococcus suis is a swine pathogen that can cause meningitis, pneumonia, septicemia, and arthritis in animals [1]
We demonstrate that our immunoproteomic-based approach can detect bacterial surface proteins
We identified two SS2 surface proteins from S. suis, including muramidase-released protein precursor (MRP), which is known to be a strong SS2 virulence factor [11,12], and an ABC transporter protein that we show is located on the bacterial cell surface

Summary

Introduction

Streptococcus suis is a swine pathogen that can cause meningitis, pneumonia, septicemia, and arthritis in animals [1]. We used untreated and ‘‘pre-absorbed’’ antisera to probe 2-DE blots of S. suis cell lysates. We used bioinformatics predictions and immunofluorescence to verify that the proteins identified were located on the bacterial cell surface.

Results

Conclusion