Antibodies Directed against Shiga-Toxin Producing Escherichia coli Serotype O103 Type III Secreted Proteins Block Adherence of Heterologous STEC Serotypes to HEp-2 Cells

Taseen S Desin,Hugh G Townsend,Andrew A Potter,Gunnar F Kaufmann

doi:10.1371/journal.pone.0139803

Taseen S Desin, Hugh G Townsend + Show 2 more

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https://doi.org/10.1371/journal.pone.0139803

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Journal: PloS one	Publication Date: Oct 9, 2015
Citations: 8	License type: CC BY 4.0

Affiliation: University of Saskatchewan

Abstract

Shiga toxin-producing Escherichia coli (STEC) serotype O103 is a zoonotic pathogen that is capable of causing hemorrhagic colitis and hemolytic uremic syndrome (HUS) in humans. The main animal reservoir for STEC is ruminants and hence reducing the levels of this pathogen in cattle could ultimately lower the risk of STEC infection in humans. During the process of infection, STECO103 uses a Type III Secretion System (T3SS) to secrete effector proteins (T3SPs) that result in the formation of attaching and effacing (A/E) lesions. Vaccination of cattle with STEC serotype O157 T3SPs has previously been shown to be effective in reducing shedding of STECO157 in a serotype-specific manner. In this study, we tested the ability of rabbit polyclonal sera against individual STECO103 T3SPs to block adherence of the organism to HEp-2 cells. Our results demonstrate that pooled sera against EspA, EspB, EspF, NleA and Tir significantly lowered the adherence of STECO103 relative to pre-immune sera. Likewise, pooled anti-STECO103 sera were also able to block adherence by STECO157. Vaccination of mice with STECO103 recombinant proteins induced strong IgG antibody responses against EspA, EspB, NleA and Tir but not against EspF. However, the vaccine did not affect fecal shedding of STECO103 compared to the PBS vaccinated group over the duration of the experiment. Cross reactivity studies using sera against STECO103 recombinant proteins revealed a high degree of cross reactivity with STECO26 and STECO111 proteins implying that sera against STECO103 proteins could potentially provide neutralization of attachment to epithelial cells by heterologous STEC serotypes.

Highlights

Shiga toxin-producing Escherichia coli (STEC) is an enteric pathogen that causes diarroheal illness in humans which can lead to hemorrhagic colitis and haemolytic uremic syndrome (HUS), one of the main causes of renal failure in children [1]
Our results demonstrate that pooled sera against STECO103 recombinant proteins significantly reduced adherence of STECO103 to HEp-2 cells relative to the group incubated with preimmune sera (Fig 1A)
The data clearly suggest that anti-sera to these four proteins were highly effective in blocking STECO103 adherence to HEp-2 cells compared to the group treated with pre-immune serum (Fig 1B and 1C)

Summary

Introduction

Shiga toxin-producing Escherichia coli (STEC) is an enteric pathogen that causes diarroheal illness in humans which can lead to hemorrhagic colitis and haemolytic uremic syndrome (HUS), one of the main causes of renal failure in children [1]. During the process of infection, STEC uses a Type Three Secretion System (T3SS) to inject virulence factors known as effector proteins directly into host cells, leading to the formation of attaching and effacing lesions (A/E) lesions, which are hallmarks of STEC infections. The STEC T3SS secretes over 50 effector proteins that are encoded on the LEE Pathogenicity Island or elsewhere on the chromosome (non-LEE effectors) [7]. Many studies have shown that the STEC T3SS is essential for colonization of cattle, implying that this is a major virulence factor employed by this pathogen [8,9,10]

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