QseC Inhibition as a Novel Antivirulence Strategy for the Prevention of Acute Hepatopancreatic Necrosis Disease (AHPND)-Causing Vibrio parahaemolyticus.

Qian Yang,Qingyao Wang,Songzhe Fu,Peizhuo Zou,Jie Huang,Zhi Cao,Guosi Xie

doi:10.3389/fcimb.2020.594652

Abstract

Acute hepatopancreatic necrosis disease (AHPND) caused by Vibrio parahaemolyticus resulted in great economic losses in global shrimp aquaculture. There is an urgent need for development of novel strategies to combat AHPND-causing V. parahaemolyticus (Vp AHPND), given that one of the greatest challenges currently is the widespread use of antibiotics and subsequent emergence of multidrug-resistant bacteria. Here, we proposed a broad-spectrum antivirulence approach targeting a conserved histidine kinase, QseC, which has been demonstrated to activate virulence expression in several Gram-negative pathogens. Our results showed that QseC mediated the catecholamine stimulated effects on growth and flagellar motility of Vp AHPND. Transcriptome analysis revealed that QseC was involved in the global regulation of the virulence of Vp AHPND as the ΔqseC mutant exhibited a decreased expression of genes related to type IV pilin, flagellar motility, and biofilm formation, while an overexpression of type VI secretion system and cell wall biosynthesis. Subsequently, the bacterial catecholamine receptor antagonist LED209 not only neutralized the stimulatory effects of host catecholamines on the growth and motility of Vp AHPND in vitro, but also attenuated the virulence of Vp AHPND towards brine shrimp larvae and white shrimp in vivo. Additionally, LED209 presented no interference with pathogen growth, nor the toxicity to the experimental animals. These results suggest that QseC can be an attractive antivirulence therapy target, and LED209 is a promising candidate for development of broad-spectrum antivirulence agents. This is the first study that demonstrated the role of QseC in the global regulation of Vp AHPND infection and demonstrated the antivirulence potential of LED209, which provides insight into the use of an antivirulence approach for targeting not only Vp AHPND, but also a much larger collection of pathogenic bacteria.

Highlights

Vibrio parahaemolyticus is a gram-negative, halophilic bacterium that is disseminated worldwide in marine and estuarine environments (Jones, 2014)
The growth response of VpAHPND strains to different catecholamines was investigated in a minimal salts medium supplemented with 30% (v/v) adult bovine serum, which exposed VpAHPND to conditions similar to those inside a host, including limited nutrient availability, iron limitation, and immune defense antibodies
The results revealed that the addition of all three kinds of catecholamines tested (i.e., EPI, NE, and DA) could significantly increase the growth of VpAHPND 123 wild type and complemented strain, but not of DqseC mutant (Figure 1A)

Summary

Introduction

Vibrio parahaemolyticus is a gram-negative, halophilic bacterium that is disseminated worldwide in marine and estuarine environments (Jones, 2014). It is frequently isolated from environmental, seafood and clinical samples, and is considered to be the leading cause of human foodborne illness in the United States and Asian countries (Newton et al, 2012; Yu et al, 2013). Specific virulent strains of V. parahaemolyticus, which contain a ~70 kb plasmid with genes encoding homologues of the Photorhabdus insect-related (Pir) binary toxin PirABVP, have recently been identified as the causative agent of acute hepatopancreatic necrosis disease (AHPND) in global shrimp industry (Tran et al, 2013). The development of alternative antimicrobial therapies to remedy this disease is urgently needed

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