The role of RTX toxins in host specificity of animal pathogenic Pasteurellaceae.
Abstract: RTX toxins are bacterial pore-forming toxins that are particularly abundant among pathogenic species of Pasteurellaceae, in which they play a major role in virulence. RTX toxins of several primary pathogens of the family of Pasteurellaceae are directly involved in causing necrotic lesions in the target organs. Many RTX toxins are known as haemolysins because they lyse erythrocytes in vitro, an effect that is non-specific, but which serves as a useful marker in bacteriological identification and as an easily measurable signal in vitro in experimental studies. More recent studies have shown that the specific targets of most RTX toxins are leukocytes, with RTX toxins binding to the corresponding β-subunit (CD18) of β2 integrins and then exerting cytotoxic activity. After uptake by the target cell, at sub-lytic concentrations, some RTX toxins are transported to mitochondria and induce apoptosis. For several RTX toxins the binding to CD18 has been shown to be host specific and this seems to be the basis for the host range specificity of these RTX toxins. Observations on two very closely related species of the Pasteurellaceae family, Actinobacillus suis, a porcine pathogen particularly affecting suckling pigs, and Actinobacillus equuli subsp. haemolytica, which causes pyosepticaemia in new-born foals (sleepy foal disease), have revealed that they express different RTX toxins, named ApxI/II and Aqx, respectively. These RTX toxins are specifically cytotoxic for porcine and equine leukocytes, respectively. Furthermore, the ApxI and Aqx toxins of these species, when expressed in an isogenetic background in Escherichia coli, are specifically cytotoxic for leukocytes of their respective hosts. These data indicate the determinative role of RTX toxins in host specificity of pathogenic species of Pasteurellaceae.
Copyright © 2011 Elsevier B.V. All rights reserved.
Publication Date: 2011-05-19 PubMed ID: 21645978DOI: 10.1016/j.vetmic.2011.05.018Google Scholar: Lookup
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Summary
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The research explores the significant role that RTX toxins play in determining the host specificity in pathogenic species of the Pasteurellaceae family of bacteria. The study highlights RTX toxins as major contributors to virulence, causing destruction in target organs and apoptosis in leukocytes.
Understanding RTX Toxins
- The study focuses on RTX (Repeats in Toxin) toxins, which are a type of pore-forming toxins particularly found abundantly in the pathogenic species of Pasteurellaceae.
- These toxins are majorly responsible for causing necrotic, or cell death inducing, lesions in the target organs of the host.
- Furthermore, they are referred to as haemolysins due to their ability to lyse, or break down, erythrocytes (red blood cells) during lab tests, demonstrating their nonspecific destructive ability and providing a measurable signal for experimental studies.
Target and Effects of RTX Toxins
- Recent research has shown that the main targets of most RTX toxins are leukocytes (white blood cells), an essential part of the immune system.
- The RTX toxins bind to the β-subunit (CD18) of β2 integrins (a protein complex) on the leukocytes before exerting their cytotoxic activity, leading to cell death.
- In situations where the toxins are present in sub-lytic concentrations, they are taken in by the target cell, transported to the mitochondria and trigger apoptosis or programmed cell death.
Role in Host Specificity
- One of the significant findings is that the binding of several RTX toxins to the CD18 subunit has displayed host specificity, explaining the host range specificity of these toxins.
- For instance, in two close species within the Pasteurellaceae family – Actinobacillus suis (which primarily affects suckling pigs) and Actinobacillus equuli subsp. haemolytica (causing disease in newborn foals), their different RTX toxins (ApxI/II and Aqx) were found to be specifically cytotoxic for porcine and equine leukocytes.
- The study also mentions how these specific RTX toxins, when expressed in an identical background in Escherichia coli, remained cytotoxic for leukocytes of their original hosts, again demonstrating host specificity.
- These findings point towards the crucial role of RTX toxins in determining the host specificity of pathogenic species within the Pasteurellaceae family.
Cite This Article
APA
Frey J.
(2011).
The role of RTX toxins in host specificity of animal pathogenic Pasteurellaceae.
Vet Microbiol, 153(1-2), 51-58.
https://doi.org/10.1016/j.vetmic.2011.05.018 Publication
Researcher Affiliations
- Institute of Veterinary Bacteriology, University of Bern, Laenggasstrasse 122, CH-3012 Bern, Switzerland. joachim.frey@vbi.unibe.ch
MeSH Terms
- Actinobacillus Infections / microbiology
- Actinobacillus Infections / veterinary
- Actinobacillus equuli
- Animals
- Bacterial Toxins / metabolism
- Hemolysin Proteins / metabolism
- Horses
- Host Specificity
- Pasteurellaceae / metabolism
- Pasteurellaceae / pathogenicity
- Pasteurellaceae Infections / microbiology
- Pasteurellaceae Infections / veterinary
- Swine
- Virulence
Citations
This article has been cited 17 times.- Kamali M, Carossino M, Del Piero F, Peak L, Mitchell MS, Willette J, Baker R, Li F, Kenéz Á, Balasuriya UBR, Go YY. Pathological Features and Genomic Characterization of an Actinobacillus equuli subsp. equuli Bearing Unique Virulence-Associated Genes from an Adult Horse with Pleuropneumonia.. Pathogens 2023 Jan 31;12(2).
- da Silva GC, Rossi CC, Rosa JN, Sanches NM, Cardoso DL, Li Y, Witney AA, Gould KA, Fontes PP, Callaghan AJ, Bossé JT, Langford PR, Bazzolli DMS. Identification of small RNAs associated with RNA chaperone Hfq reveals a new stress response regulator in Actinobacillus pleuropneumoniae.. Front Microbiol 2022;13:1017278.
- Ballesteros-Monrreal MG, Arenas-Hernández MMP, Barrios-Villa E, Juarez J, Álvarez-Ainza ML, Taboada P, De la Rosa-López R, Bolado-Martínez E, Valencia D. Bacterial Morphotypes as Important Trait for Uropathogenic E. coli Diagnostic; a Virulence-Phenotype-Phylogeny Study.. Microorganisms 2021 Nov 18;9(11).
- Tang B, Bojesen AM. Immune Suppression Induced by Gallibacterium anatis GtxA During Interaction with Chicken Macrophage-Like HD11 Cells.. Toxins (Basel) 2020 Aug 20;12(9).
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