Reduced virulence of the MARTX toxin increases the persistence of outbreak-associated Vibrio vulnificus in host reservoirs.
Ontology highlight
ABSTRACT:
SUBMITTER: Choi S
PROVIDER: S-EPMC8191300 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Vibrio vulnificus is an environmental organism that causes septic human infections characterized by high morbidity and mortality. The annual incidence and global distribution of this pathogen are increasing as ocean waters warm. Clinical strains exhibit variations in the primary virulence toxin, suggesting a potential for the emergence of new strains with altered virulence properties. A clonal outbreak of tilapia-associated wound infections in Israel serves as a natural experiment for the sudden emergence of a new V. vulnificus strain. The effector domain content of the multifunctional autoprocessing RTX (MARTX) toxin of the outbreak-associated biotype 3 (BT3) strains was previously shown to harbor a modification generated by recombination. The modification introduced an actin-induced adenylate cyclase effector domain (ExoY) and an effector domain that disrupts the Golgi organelle (DmX). Here, we report that the exchange of these effector domains for a putative progenitor biotype 1 toxin arrangement produces a toxin that slows the lysis kinetics of targeted epithelial cells but increases cellular rounding phenotypes in response to bacteria. In addition, replacing the biotype 3 toxin variant with the putative progenitor biotype 1 variant renders the resulting strain significantly more virulent in mice. This suggests that the exchange of MARTX effector domains during the emergence of BT3 generated a toxin with reduced toxin potency, resulting in decreased virulence of this outbreak-associated strain. We posit that selection for reduced virulence may serve as a route for this lethal infectious agent to enter the human food chain by allowing it to persist in natural hosts. IMPORTANCEVibrio vulnificus is a serious infection linked to climate change. The virulence capacity of these bacteria can vary by gene exchange, resulting in new variants of the primary virulence toxin. In this study, we tested whether the emergence of an epidemic strain of V. vulnificus with a novel toxin variant correlated with a change in virulence. We found that restoring the biotype 3 toxin variant to the putative progenitor-type toxin resulted in dramatically increased virulence, revealing that the emergence of the biotype 3 strain could be linked to virulence reduction. This reduced virulence, previously found also in the biotype 1 strain, suggests that reduced virulence may stimulate outbreaks, as strains have greater capacity to enter the human food chain through reduced impact to environmental hosts.
| S-EPMC5555677 | biostudies-other
Project description:To understand toxin-stimulated host-pathogen interactions, we performed dual-transcriptome sequencing experiments using human epithelial (HT-29) and differentiated THP-1 (dTHP-1) immune cells infected with the sepsis-causing pathogen Vibrio vulnificus (either the wild-type [WT] pathogen or a multifunctional-autoprocessing repeats-in-toxin [MARTX] toxin-deficient strain). Gene set enrichment analyses revealed MARTX toxin-dependent responses, including negative regulation of extracellular related kinase 1 (ERK1) and ERK2 (ERK1/2) signaling and cell cycle regulation in HT-29 and dTHP-1 cells, respectively. Further analysis of the expression of immune-related genes suggested that the MARTX toxin dampens immune responses in gut epithelial cells but accelerates inflammation and nuclear factor κB (NF-κB) signaling in immune cells. With respect to the pathogen, siderophore biosynthesis genes were significantly more highly expressed in WT V. vulnificus than in the MARTX toxin-deficient mutant upon infection of dTHP-1 cells. Consistent with these results, iron homeostasis genes that limit iron levels for invading pathogens were overexpressed in WT V. vulnificus-infected dTHP-1 cells. Taken together, these results suggest that MARTX toxin regulates host inflammatory responses during V. vulnificus infection while also countering host defense mechanisms such as iron limitation.IMPORTANCEV. vulnificus is an opportunistic human pathogen that can cause life-threatening sepsis in immunocompromised patients via seafood poisoning or wound infection. Among the toxic substances produced by this pathogen, the MARTX toxin greatly contributes to disease progression by promoting the dysfunction and death of host cells, which allows the bacteria to disseminate and colonize the host. In response to this, host cells mount a counterattack against the invaders by upregulating various defense genes. In this study, the gene expression profiles of both host cells and V. vulnificus were analyzed by RNA sequencing to gain a comprehensive understanding of host-pathogen interactions. Our results suggest that V. vulnificus uses the MARTX toxin to subvert host cell immune responses as well as to oppose host counterattacks such as iron limitation.
| S-EPMC7426173 | biostudies-literature
Project description:The objective of this study was to analyze multifunctional autoprocessing repeats-in-toxin (MARTX) toxin domain organization within the aquatic species Vibrio vulnificus as well as to study the evolution of the rtxA1 gene. The species is subdivided into three biotypes that differ in host range and geographical distribution. We have found three different types (I, II, and III) of V. vulnificus MARTX (MARTX(Vv)) toxins with common domains (an autocatalytic cysteine protease domain [CPD], an α/β-hydrolase domain, and a domain resembling that of the LifA protein of Escherichia coli O127:H6 E2348/69 [Efa/LifA]) and specific domains (a Rho-GTPase inactivation domain [RID], a domain of unknown function [DUF], a domain resembling that of the rtxA protein of Photorhabdus asymbiotica [rtxA(PA)], and an actin cross-linking domain [ACD]). Biotype 1 isolates harbor MARTX(Vv) toxin types I and II, biotype 2 isolates carry MARTX(Vv) toxin type III, and biotype 3 isolates have MARTX(Vv) toxin type II. The analyzed biotype 2 isolates harbor two identical copies of rtxA1, one chromosomal and the other plasmidic. The evolutionary history of the gene demonstrates that MARTX(Vv) toxins are mosaics, comprising pieces with different evolutionary histories, some of which have been acquired by intra- or interspecific horizontal gene transfer. Finally, we have found evidence that the evolutionary history of the rtxA1 gene for biotype 2 differs totally from the gene history of biotypes 1 and 3.
| S-EPMC3020528 | biostudies-literature
Project description:V. vulnificus-infected patients suffer from hemolytic anemia and circulatory lesions, often accompanied by venous thrombosis. However, the pathophysiological mechanism of venous thrombosis associated with V. vulnificus infection remains largely unknown. Herein, V. vulnificus infection at the sub-hemolytic level induced shape change of human red blood cells (RBCs) accompanied by phosphatidylserine exposure, and microvesicle generation, leading to the procoagulant activation of RBCs and ultimately, acquisition of prothrombotic activity. Of note, V. vulnificus exposed to RBCs substantially upregulated the rtxA gene encoding multifunctional autoprocessing repeats-in-toxin (MARTX) toxin. Mutant studies showed that V. vulnificus-induced RBC procoagulant activity was due to the pore forming region of the MARTX toxin causing intracellular Ca2+ influx in RBCs. In a rat venous thrombosis model triggered by tissue factor and stasis, the V. vulnificus wild type increased thrombosis while the ΔrtxA mutant failed to increase thrombosis, confirming that V. vulnificus induces thrombosis through the procoagulant activation of RBCs via the mediation of the MARTX toxin.
| S-EPMC9385741 | biostudies-literature
Project description:The multifunctional-autoprocessing repeats-in-toxin (MARTX) toxins are bacterial protein toxins that serve as delivery platforms for cytotoxic effector domains. The domain of unknown function in position 5 (DUF5) effector domain is present in at least six different species' MARTX toxins and as a hypothetical protein in Photorhabdus spp. Its presence increases the potency of the Vibrio vulnificus MARTX toxin in mouse virulence studies, indicating DUF5 directly contributes to pathogenesis. In this work, DUF5 is shown to be cytotoxic when transiently expressed in HeLa cells. DUF5 localized to the plasma membrane dependent upon its C1 domain and the cells become rounded dependent upon its C2 domain. Both full-length DUF5 and the C2 domain caused growth inhibition when expressed in Saccharomyces cerevisiae. A structural model of DUF5 was generated based on the structure of Pasteurella multocida toxin facilitating localization of the cytotoxic activity to a 186 amino acid subdomain termed C2A. Within this subdomain, an alanine scanning mutagenesis revealed aspartate-3721 and arginine-3841 as residues critical for cytotoxicity. These residues were also essential for HeLa cell intoxication when purified DUF5 fused to anthrax toxin lethal factor was delivered cytosolically. Thermal shift experiments indicated that these conserved residues are important to maintain protein structure, rather than for catalysis. The Aeromonas hydrophila MARTX toxin DUF5(Ah) domain was also cytotoxic, while the weakly conserved C1-C2 domains from P. multocida toxin were not. Overall, this study is the first demonstration that DUF5 as found in MARTX toxins has cytotoxic activity that depends on conserved residues in the C2A subdomain.
| S-EPMC4177264 | biostudies-literature
Project description:Vibrio vulnificus is an foodborne pathogen that can cause gastroenteritis and septicemia in humans. V. vulnificus secretes a multifunctional autoprocessing repeats-in-toxin (MARTX) toxin as an essential virulence factor to cause disease. MARTX toxins are pore-forming toxins that translocate multiple functionally independent effector domains into a target cell. MARTX toxins of V. vulnificus can contain anywhere from 3 to 5 of the 10 identified effector domains and strains with different effector repertories having varying virulence potential. The goal of this study was to compare how different effector combinations from an F-type MARTX toxin differentially remodel the transcriptional response of human intestinal epithelial cells (IECs). F-type MARTX toxins contain five effector domains – the actin crosslinking domain (ACD), two copies the makes caterpillar floppy-like domain (MCF), and alpha-beta hydrolase (ABH) domain, and the Ras/Rap1 specific endopeptidase (RRSP). Cultured human IECs were treated with V. vulnificus or strains modified to secrete a toxin with only ACD, ACD with MCF-ABH, ACD with RRSP, or no active effectors. We demonstrate that when no active effectors are present, the bacterium induces minimal changes in the transcriptional profile of IECs. However, the strains containing different effector combinations each uniquely remodeled the transcriptional profile of IECs. These data provide insight into how V. vulnificus strains with varying effector combinations can differentially regulate the host cell response to cause disease.
2021-11-21 | GSE189194 | GEO
Project description:(1)H, (13)C, and (15)N chemical shift assignments are presented for the isolated four-helical bundle membrane localization domain from the domain of unknown function 5 (DUF5) effector (MLD(VvDUF5)) of the MARTX toxin from Vibrio vulnificus in its solution state. We have assigned 97% of all backbone and side-chain carbon atoms, including 96% of all backbone residues. Secondary chemical shift analysis using TALOS+ demonstrates four helices that align with those predicted by structure homology modeling using the MLDs of Pasteurella multocida toxin (PMT) and the clostridial TcdB and TcsL toxins as templates. Future studies will be towards solving the structure and determining the dynamics in the solution state.
| S-EPMC3859858 | biostudies-literature
Project description:The multifunctional-autoprocessing repeats-in-toxin (MARTX(Vv)) toxin that harbours a varied repertoire of effector domains is the primary virulence factor of Vibrio vulnificus. Although ubiquitously present among Biotype I toxin variants, the 'Makes caterpillars floppy-like' effector domain (MCF(Vv)) is previously unstudied. Using transient expression and protein delivery, MCF(Vv) and MCF(Ah) from the Aeromonas hydrophila?MARTX(Ah)) toxin are shown for the first time to induce cell rounding. Alanine mutagenesis across the C-terminal subdomain of MCF(Vv) identified an Arg-Cys-Asp (RCD) tripeptide motif shown to comprise a cysteine protease catalytic site essential for autoprocessing of MCF(Vv). The autoprocessing could be recapitulated in vitro by the addition of host cell lysate to recombinant MCF(Vv), indicating induced autoprocessing by cellular factors. The RCD motif is also essential for cytopathicity, suggesting autoprocessing is essential first to activate the toxin and then to process a cellular target protein resulting in cell rounding. Sequence homology places MCF(Vv) within the C58 cysteine protease family that includes the type III secretion effectors YopT from Yersinia spp. and AvrPphB from Pseudomonas syringae. However, the catalytic site RCD motif is unique compared with other C58 peptidases and is here proposed to represent a new subgroup of autopeptidase found within a number of putative large bacterial toxins.
| S-EPMC4583801 | biostudies-literature
Project description:Vibrio vulnificus biotype 2-serovar E is a zoonotic clonal complex that can cause death by sepsis in humans and fish. Unlike other biotypes, Bt2 produces a unique type of MARTXVv (Multifunctional-Autoprocessive-Repeats-in-Toxin; RtxA13), which is encoded by a gene duplicated in the pVvBt2 plasmid and chromosome II. In this work, we analyzed the activity of this toxin and its role in human sepsis by performing in vitro, ex vivo, and in vivo assays. First, we demonstrated that the ACD domain, present exclusively in this toxin variant, effectively has an actin-cross-linking activity. Second, we determined that the whole toxin caused death of human endotheliocytes and monocytes by lysis and apoptosis, respectively. Finally, we tested the hypothesis that RtxA13 contributes to human death caused by this zoonotic serovar by triggering an early cytokine storm in blood. To this end, we used a Bt2-SerE strain (R99) together with its rtxA13 deficient mutant, and a Bt1 strain (YJ016) producing RtxA11 (the most studied MARTXVv) together with its rtxA11 deficient mutant, as controls. Our results showed that RtxA13 was essential for virulence, as R99ΔΔrtxA13 was completely avirulent in our murine model of infection, and that R99, but not strain YJ016, induced an early, strong and dysregulated immune response involving the up-regulation of a high number of genes. This dysregulated immune response was directly linked to RtxA13. Based on these results and those obtained ex vivo (human blood), we propose a model of infection for the zoonotic serovar of V. vulnificus, in which RtxA13 would act as a sepsis-inducing toxin.
| S-EPMC5517466 | biostudies-literature
Project description:Vibrio vulnificus is an opportunistic pathogen that causes gastroenteritis and septicemia in humans. The V. vulnificus multifunctional-autoprocessing repeats-in-toxin (MARTX) toxin is a pore-forming toxin that translocates multiple functionally independent effector domains into target cells and an essential virulence factor for fatal disease. The effector repertoire delivered and thus the mechanism of action of the toxin can differ dramatically across V. vulnificus isolates. Here, we utilize a strain of V. vulnificus that carries an F-type MARTX toxin that delivers an actin cross-linking domain (ACD) and four other effector domains. We demonstrate that ACD is the primary driver of virulence following intragastric infection and of bacterial dissemination to distal organs. We additionally show that ACD activates the transcription of intermediate early response genes in cultured intestinal epithelial cells (IECs). However, the genes activated by ACD are suppressed, at least in part, by the codelivered Ras/Rap1-specific endopeptidase (RRSP). The transcriptional response induced by strains translocating only RRSP results in a unique transcriptional profile, demonstrating that the transcriptional response to V. vulnificus is remodeled rather than simply suppressed by the MARTX toxin effector repertoire. Regardless, the transcriptional response in the intestinal tissue of infected mice is dominated by ACD-mediated induction of genes associated with response to tissue damage and is not impacted by RRSP or the three other effectors codelivered with ACD and RRSP. These data demonstrate that while other effectors do remodel early intestinal innate immune responses, ACD is the dominant driver of disease progression by ACD+ V. vulnificus during intestinal infection.
| S-EPMC9022507 | biostudies-literature