Activation mechanism of human Hageman factor-plasma kallikrein-kinin system by Vibrio vulnificus metalloprotease

The cytochrome d oxidase complex regulated by fexA is an Achilles' heel in the in vivo survival of vibrio vulnificus

Vibrio vulnificus is a halophilic estuarine bacterium causing severe opportunistic infections. To successfully establish an infection, V. vulnificus must adapt to redox fluctuations in vivo. In the present study, we show that deletion of V. vulnificus fexA gene caused hypersensitivity to acid and reactive oxygen species. The ΔfexA mutant exhibited severe in vivo survival defects. For deeper understanding the role of fexA gene on the successful V. vulnificus infection, we analyzed differentially expressed genes in ΔfexA mutant in comparison with wild type under aerobic, anaerobic or in vivo culture conditions by genome-scale DNA microarray analyses. Twenty-two genes were downregulated in the ΔfexA mutant under all three culture conditions. Among them, cydAB appeared to dominantly contribute to the defective phenotypes of the ΔfexA mutant. The fexA deletion induced compensatory point mutations in the cydAB promoter region over subcultures, suggesting essentiality. Those point mutations (PcydSMs) restored bacterial growth, motility, cytotoxicity ATP production and mouse lethality in the ΔfexA mutant. These results indicate that the cydAB operon, being regulated by FexA, plays a crucial role in V. vulnificus survival under redox-fluctuating in vivo conditions. The FexA-CydAB axis should serve an Achilles heel in the development of therapeutic regimens against V. vulnificus infection.

Vibrio vulnificus VvpE Stimulates IL-1β Production by the Hypomethylation of the IL-1β Promoter and NF-κB Activation via Lipid Raft–Dependent ANXA2 Recruitment and Reactive Oxygen Species Signaling in Intestinal Epithelial Cells

An inflammatory response is a hallmark of necrosis evoked by bacterial pathogens. Vibrio vulnificus, VvpE, is an elastase that is responsible for tissue necrosis and inflammation; however, the molecular mechanism by which it regulates host cell death has not been characterized. In the present study, we investigate the cellular mechanism of VvpE with regard to host cell death and the inflammatory response of human intestinal epithelial (INT-407) cells. The recombinant protein (r)VvpE (50 pg/ml) caused cytotoxicity mainly via necrosis coupled with IL-1β production. The necrotic cell death induced by rVvpE is highly susceptible to the knockdown of annexin A (ANXA)2 and the sequestration of membrane cholesterol. We found that rVvpE induces the recruitment of NADPH oxidase 2 and neutrophil cytosolic factor 1 into membrane lipid rafts coupled with ANXA2 to facilitate the production of reactive oxygen species (ROS). The bacterial signaling of rVvpE through ROS production is uniquely mediated by the phosphorylation of redox-sensitive transcription factor NF-κB. The silencing of NF-κB inhibited IL-1β production during necrosis. rVvpE induced hypomethylation and region-specific transcriptional occupancy by NF-κB in the IL-1β promoter and has the ability to induce pyroptosis via NOD-, LRR-, and pyrin domain–containing 3 inflammasome. In a mouse model of V. vulnificus infection, the mutation of the vvpE gene from V. vulnificus negated the proinflammatory responses and maintained the physiological levels of the proliferation and migration of enterocytes. These results demonstrate that VvpE induces the hypomethylation of the IL-1β promoter and the transcriptional regulation of NF-κB through lipid raft–dependent ANXA2 recruitment and ROS signaling to promote IL-1β production in intestinal epithelial cells.

Protease-armed bacteria in the skin

The skin constitutes a formidable barrier against commensal and pathogenic bacteria, which permanently and transiently colonise the skin, respectively. Commensal and pathogenic species inhabiting skin both express proteases. Whereas proteases secreted by commensals contribute to homeostatic bacterial coexistence on skin, proteases from pathogenic bacteria are used as virulence factors, helping them colonise skin with breached integrity of the epithelial layer. From these initial sites of colonisation, pathogens can disseminate into deeper layers of skin, possibly leading to the spread of infection. Secreted bacterial proteases probably play an important role in this process and in the deterrence of innate defence mechanisms. For example, Staphylococcus aureus proteases are essential for changing the bacterial phenotype from adhesive to invasive by degrading adhesins on the bacterial cell surface. Secreted staphylococcal proteases mediate pathogen penetration by degrading collagen and elastin, essential components of connective tissue in the dermis. The activation of the contact system and kinin generation by Streptococcus pyogenes and S. aureus proteases contributes to an inflammatory reaction manifested by oedema, redness and pain. Kinin-enhanced vascular leakage might help bacteria escape into the circulation thereby causing possible systemic dissemination of the infection. The inflammatory reaction can also be fueled by the activation of protease-activated receptors on keratinocytes. Concomitantly, bacterial proteases are involved in degrading antimicrobial peptides, disarming the complement system and neutrophils and preventing the infiltration of the infected sites with immune cells by inactivation of chemoattractants. Together, this provides protection for colonising and/or invading pathogens from attack by antibacterial forces of the skin.

Putative virulence factors identified in Vibrio vulnificus strains isolated from oysters and seawater in Mexico

The presence of Vibrio vulnificus was analyzed in oyster and estuarine water samples from Mexico by PCR amplification of the vvhA gene and some putative virulence factors were tested. Samples were collected from 12 different sampling points over a one-year period; 31% samples were positive for V. vulnificus and all isolates were identified as biotype 1. All strains were cytotoxic and proteolytic, 98% showed adherence to epithelial cells, 91.4% were DNase-positive, 77.6% were mucinase-positive, 97.8% were lecithinase-positive and 79.8% were lipase positive. Regarding colony morphology, 51% strains were opaque, 20% were translucid, 28% were both opaque and translucid, and 80.8% showed a capsule. This is the first report on the isolation of V. vulnificus strains from environmental samples in Mexico, which may pose a health risk for local fisherman and seafood consumers.

Vibrio vulnificus infection and metalloprotease

Vibrio vulnificus is ubiquitous in aquatic environments; however, it occasionally causes serious and often fatal infections in humans. These include invasive septicemia contracted through consumption of raw seafood, as well as wound infections acquired through contact with brackish or marine waters. In most cases of septicemia, the patients have underlying disease(s), such as liver dysfunction or alcoholic cirrhosis, and the secondary skin lesions including cellulitis, edema and hemorrhagic bulla appear on the limbs. Although V. Vul produces various virulent factors including polysaccharide capsule, type IV pili, hemolysin and proteolytic enzymes, the 45-kDa metalloprotease may be a causative factor of the skin lesions, because the purified protease enhances vascular permeability through generation of chemical mediators and also induces serious hemorrhagic damage through digestion of the vascular basement membrane. As well as other bacteria, V. Vul can regulate the protease production through the quorum-sensing system depending on bacterial cell density. However, this system operates efficiently at 25 degrees C, but not at 37 degrees C. Therefore, V. vulnificus may produce sufficient amounts of the protease only in the interstitial tissue of the limbs, in which temperature is lower than the internal temperature of the human body.

Inactivation of Vibrio vulnificus hemolysin by oligomerization but not proteolysis

Vibrio vulnificus extracellular protease (VvpE) is believed to destroy its hemolysin (VvhA) in the late growth phase, without obvious experimental evidence. So, we attempted to elucidate the mechanism. The hemolytic activity steeply increased with the expression of the VvhA in the early growth phase, and then abruptly declined with the expression of VvpE in the late growth phase. However, the VvhA activity also abruptly declined in a VvpE-deficient mutant. In Western blot, the degradation of VvhA was not observed; instead, the oligomerization of VvhA increased with the concomitant loss of hemolytic activity. These results evidently indicate that the inactivation of VvhA is due to the novel oligomerization of VvhA by unknown mechanism, but not to the destruction of VvhA by VvpE, so that the routine functional assay measuring hemolytic activity cannot reflect the actual production of VvhA.

Vibrio vulnificusmetalloprotease VvpE has no direct effect on the iron-assimilation from human holotransferrin

In order to elucidate the role of Vibrio vulnificus metalloprotease VvpE in the uptake of iron from human transferrin, we constructed a VvpE-deficient mutant and a merozygotic vvpE-transcriptional reporter from the wild type strain MO6-24/O. All three strains were able to grow only in deferrated Heart Infusion broth (DF-HI) with human holotransferrin (HT), but not in DF-HI containing partially iron-saturated transferrin or apotransferrin, without noticeable differences among the strains. All strains consumed most iron in the early growth phase. Both the transcription and extracellular production of VvpE proceeded at undetectable levels when bacterial growth was severely retarded in the DF-HI. When HT or FeCl(3) was added to the DF-HI, the retarded bacterial growth was restored and vvpE transcription dramatically increased in the late growth phase, but the extracellular VvpE production was negligible as compared to its transcription. All strains were unable to degrade HT even in normal HI broth containing HT, in which extracellular VvpE activity was remarkably high. The uptake of iron from HT in all strains was consistent with the production of catechol-siderophore rather than hydroxamate-siderophore. Similar results were also observed when clinical isolates from septicemic patients were used. In conclusion, we determined that VvpE was not directly involved in the siderophore-mediated iron-uptake from human transferrin. In addition, the discrepancy between the transcription and extracellular production of VvpE suggests that additional posttranscriptional events are involved in the extracellular production of VvpE.

Generation of active fragments from human zymogens in the brady kinin-generating cascade by extracellular proteases from Vibrio vulnificus and V. parahaemolyticus

Vibrio vulnificus is an opportunistic human pathogen causing septicemia, and the infection is characterized by formation of the edematous skin lesions on limbs. This pathogenic species secretes a thermolysin-like metalloprotease as a virulence determinant. The metalloprotease was confirmed to activate human factor XII-plasma kallikrein-kinin cascade that results in liberation of bradykinin, a chemical mediator enhancing the vascular permeability, from high-molecular weight kininogen. Namely, the metalloprotease showed to generate active fragments by cleavage of Arg-Ile, Arg-Val or Gly-Leu peptide bond in human zymogens (plasma prekallikrein and factor XII). In spite of induction of the sufficient vascular permeability-enhancing and edema-forming reaction in the guinea pig model, a serine protease from V. parahaemolyticus, a human pathogen causing primarily watery diarrhea, showed far less ability to activate and to cleave the human zymogens. These results in part may explain why only V. vulnificus often causes serious edematous skin damages in humans.

Regulation of Vibrio vulnificus virulence by the LuxS quorum-sensing system

Vibrio vulnificus is a halophilic estuarine bacterium that causes fatal septicaemia and necrotizing wound infections. We tested whether V. vulnificus produces signalling molecules (autoinducer 1 and/or 2) stimulating Vibrio harveyi quorum-sensing system 1 and/or 2. Although there was no evidence for signalling system 1, we found that V. vulnificus produced a signalling activity in the culture supernatant that induced luminescence expression in V. harveyi through signalling system 2. Maximal autoinducer 2 (AI-2) activity was observed during mid-exponential to early stationary phase and disappeared in the late stationary phase when V. vulnificus was grown in heart infusion broth containing 2.5% NaCl. V. vulnificus showed increased signalling activity when it was cultured in the presence of glucose (0.5%) and at low pH (pH 6.0). From a cosmid library of V. vulnificus type strain ATCC 29307, we have identified the AI-2 synthase gene (luxSVv) showing 80% identity with that of V. harveyi (luxSVh) at the amino acid level. To investigate the pathogenic role of luxSVv, a deletion mutant of the clinical isolate V. vulnificus MO6-24/O was constructed. The luxSVv mutant showed a significant delay in protease production and an increase in haemolysin production. The decreased protease and increased haemolysin activities were restored to the isogenic wild-type level by complementation with the wild-type luxSVv allele. The change in phenotypes was also complemented by logarithmic phase spent media produced by the wild-type bacteria. Transcriptional activities of the haemolysin gene (vvhA) and protease gene (vvpE) were also observed in the mutant using chromosomal PvvhA::lacZ and PvvpE::lacZ transcriptional reporter constructs: transcription of vvhA was increased and of vvpE decreased by the mutation. The mutation resulted in an attenuation of lethality to mice. Intraperitoneal LD50 of the luxSVv mutant increased by 10- and 750-fold in ferric ammonium citrate-non-overloaded and ferric ammonium citrate-overloaded mice respectively. The time required for the death of mice was also significantly delayed in the luxSVv mutant. Cytotoxic activity of the organism against HeLa cells, measured by lactate dehydrogenase (LDH) release assay, was also decreased significantly by the mutation. Taken together, the V. vulnificus LuxS quorum-sensing system seems to play an important role in co-ordinating the expression of virulence factors.

Purification of a serine protease of Vibrio parahaemolyticus and its characterization

A 50 kDa protease designated as VPP1 was purified from the culture supernatant of a clinical strain of Vibrio parahaemolyticus by ammonium sulfate fractionation, Sephacryl S-200 HR gel filtration and Fractogel EMD TMAE 650 ion-exchange chromatography. VPP1 was inhibited by EDTA, EGTA and serine protease inhibitors, suggesting that it is a calcium-dependent serine protease. N-terminal amino acid sequence of VPP1 was quite similar to that of V. metschnikovii protease and antibody against VPP1 inhibited the activity of V. metschnikovii protease, suggesting the similarity of the two proteases. It was demonstrated that VPP1 or its related protease widely distribute in not only V. parahaemolyticus but also V. alginolyticus.

Isolation and characterization of a Vibrio vulnificus mutant deficient in both extracellular metalloprotease and cytolysin

We isolated a Vibrio vulnificus mutant that was deficient in both metalloprotease and cytolysin by allelic exchange. The virulence of this mutant in mice and its cytotoxicity for HEp-2 cells were comparable to those of the wild-type strain, indicating that neither factor was essential for these properties. The cytolysin, but not the protease, seemed to be important for causing damage in the alimentary tract of the mice.

Regulation of metalloprotease gene expression in Vibrio vulnificus by a Vibrio harveyi LuxR homologue

Expression of the Vibrio vulnificus metalloprotease gene, vvp, was turned up rapidly when bacterial growth reached the late log phase. A similar pattern of expression has been found in the metalloprotease gene of Vibrio cholerae, and this has been shown to be regulated by a Vibrio harveyi LuxR-like transcriptional activator. To find out whether a LuxR homologue exists in V. vulnificus, a gene library of this organism was screened by colony hybridization using a probe derived from a sequence that is conserved in various luxR-like genes of vibrios. A gene containing a 618-bp open reading frame was identified and found to be identical to the smcR gene of V. vulnificus reported previously. An isogenic SmcR-deficient (RD) mutant was further constructed by an in vivo allelic exchange technique. This mutant exhibited an extremely low level of vvp transcription compared with that of the parent strain. On the other hand, the cytolysin gene, vvhA, was expressed at a higher level in the RD mutant than in the parent strain during the log phase of growth. These data suggested that SmcR might not only be a positive regulator of the protease gene but might also be involved in negative regulation of the cytolysin gene. Virulence of the RD mutant in either normal or iron-overloaded mice challenged by intraperitoneal injection was comparable to that of the parent strain, indicating that SmcR is not required for V. vulnificus virulence in mice.

Construction and phenotypic evaluation of a Vibrio vulnificus vvpE mutant for elastolytic protease

Vibrio vulnificus is an opportunistic gram-negative pathogen that commonly contaminates oysters. Predisposed individuals who consume raw oysters can die within days from sepsis, and even otherwise healthy people are susceptible to serious wound infection after contact with contaminated seafood or seawater. Numerous secreted and cell-associated virulence factors have been proposed to account for the fulminating and destructive nature of V. vulnificus infections. Among the putative virulence factors is an elastolytic metalloprotease. We cloned and sequenced the vvpE gene encoding an elastase of V. vulnificus ATCC 29307. The functions of the elastase were assessed by constructing vvpE insertional knockout mutants and evaluating phenotypic changes in vitro and in mice. Although other types of protease activity were still observed in vvpE mutants, elastase activity was completely absent in the mutants and was restored by reintroducing the recombinant vvpE gene. In contrast to previous characterization of elastase as a potential virulence factor, which was demonstrated by injecting the purified protein into animals, inactivation of the V. vulnificus vvpE gene did not affect the ability of the bacteria to infect mice and cause damage, either locally in subcutaneous tissues or systemically in the liver, in both iron-treated and normal mice. Furthermore, a vvpE mutant was not affected with regard to cytolytic activity toward INT407 epithelial cells or detachment of INT407 cells from culture dishes in vitro. Therefore, it appears that elastase is less important in the pathogenesis of V. vulnificus than would have been predicted by examining the effects of administering purified proteins to animals. However, V. vulnificus utilizes a variety of virulence factors; hence, the effects of inactivation of elastase alone could be masked by other compensatory virulence factors.

Metalloprotease is not essential for Vibrio vulnificus virulence in mice

Previous work suggested that a metalloprotease, Vvp, may be a virulence factor of Vibrio vulnificus, which causes severe wound infection and septicemia in humans. To determine the role of Vvp in pathogenesis, we isolated an isogenic protease-deficient (PD) mutant of Vibrio vulnificus by in vivo allelic exchange. This PD mutant was as virulent as its parental strain in mice infected intraperitoneally and was 10-fold more virulent in mice infected via the oral route. Furthermore, the PD mutant was indistinguishable from its parental strain in invasion from peritoneal cavity into blood stream, enhancement of vascular permeability, growth in murine blood, and utilization of hemoglobin and transferrin. These data suggest that Vvp is not essential for virulence in the mouse. However, the cytolysin activity in the culture supernatant of the PD mutant was found to be twofold higher than that of the wild-type strain and remained for a much longer period. The higher cytolysin activity of the PD mutant may be associated with the enhanced virulence in mice infected via the oral route.

Microbial metalloproteases and pathogenesis

Zinc metalloproteases produced by human pathogenic microorganisms show a wide variety of pathological actions. In local infections, the proteases cause necrotic or hemorrhagic tissue damage through digestion of structural components of the ground substance, and also form edematous lesions through generation of inflammatory mediators, while in systemic infections, the proteases act as a synergistic virulence factor through disordered proteolysis of many plasma proteins. Clostridial neurotoxins, Bacteroides fragilis enterotoxin and Bacillus anthracis lethal factor are also zinc metalloproteases.

Cloning and characterization of the gene (empV) encoding extracellular metalloprotease from Vibrio vulnificus

A gene (empV) encoding the extracellular metalloprotease of Vibrio vulnificus CKM-1 has been cloned and sequenced. When the empV gene was expressed in minicells, a unique peptide of approx. 46 kDa was identified. Protease activity staining experiments also indicated a similar M(r) for the protease. The empV gene product (EmpV) is secreted into the periplasm of Escherichia coli, but not out of it. The crude enzyme prepared from the periplasmic fraction of recombinant E. coli was inhibited by a metalloprotease inhibitor and Zn2+ is essential for its protease activity. Nucleotide sequence analysis predicted a single open reading frame (ORF) of 1818 bp encoding a 606 amino acid (aa) polypeptide, with a potential 24 aa signal peptide followed by a long 'pro' sequence consisting of 172 aa. The N-terminal 20 aa sequence for the elastolytic protease (EepV), purified from the culture supernatant of V. vulnificus ATCC 29307, completely identified the beginning of the predicted mature protein within the deduced aa sequence except for 1 aa residue difference. The estimated pI and molecular weight of the predicted mature protein were 5.86 and 44.3 kDa, respectively, which are nearly identical to those of V. vulnificus L-180 extracellular neutral metalloprotease (EnmV) and of strain ATCC 29307 EepV. The estimated molecular weight also closely matches that determined by SDS-PAGE analysis of the minicells and by protease activity staining. The deduced aa sequence of EmpV showed high homology to V. anguillarum metalloprotease (EmpA), V. cholerae HA/protease (HprC), and V proteolyticus neutral protease (NprP), particularly with respect to active-site residues, zinc-binding residues, and cysteine residues.

Pathogenic vibrios in the natural aquatic environment

In recent years, members belonging to the genus Vibrio of the family Vibrionaceae have acquired increasing importance because of the association of several of its members with human disease. The most feared of the Vibrio species is Vibrio cholerae, the causative agent of cholera, a devastating disease of global significance. Other important vibrios of medical importance are V. parahemolyticus, V. vulnificus, V. mimicus, and to a lesser extent V. fluvialis, V. furnissii, V. hollisae, and V. damsela. Recent studies have also implicated V. alginolyticus and V. metschnikovii in human disease, although their complete significance has not yet been established. The virulence of all medically important vibrios is aided by a variety of traits that help breach human defenses. In this review, we provide an overview of the environmental distribution of the pathogenic vibrios and the important virulence traits that enable them to cause disease.

Activation of human matrix metalloproteinases by various bacterial proteinases

Matrix metalloproteinases (MMPs) are zinc-containing proteinases that participate in tissue remodeling under physiological and pathological conditions. To test the involvement of bacterial proteinases in tissue injury during bacterial infections, we investigated the activation potential of various bacterial proteinases against precursors of MMPs (proMMPs) purified from human neutrophils (proMMP-8 and -9) and from human fibrosarcoma cells (proMMP-1). Each proMMP was subjected to treatment with a series of bacterial proteinases at molar ratios of 0.01-0.1 (bacterial proteinase to proMMP), and activities of MMPs generated were determined. Among six different bacterial proteinases, thermolysin family enzymes (family M4) such as Pseudomonas aeruginosa elastase, Vibrio cholerae proteinase, and thermolysin strongly activated all three proMMPs via limited proteolysis to generate active forms of the MMPs. N-terminal sequence analysis of the active MMPs revealed that cleavage occurred at the Val82-Leu83 and Thr90-Phe91 bonds of proMMP-1 and proMMP-9, respectively, which are located near the N terminus of the catalytic domain of MMPs. In contrast, Serratia 56-kDa proteinase and Pseudomonas alkaline proteinase, both of which are classified as members of the serralysin subfamily of zinc metalloproteinases (family M10), and Serratia 73-kDa thiol proteinase did not evidence proteolytic processing or activation of proMMP-1, -8, and -9 under these experimental conditions. These results indicate that bacterial proteinases may play an important role in tissue destruction and disintegration of extracellular matrix at the site of infections.

Purification, characterization, and primary structure of Clostridium perfringens lambda-toxin, a thermolysin-like metalloprotease

The lambda-toxin of Clostridium perfringens type B NCIB10691 was purified by ammonium sulfate precipitation, followed by size exclusion, anion-exchange, and hydrophobic interaction chromatography. The purified toxin had an apparent molecular mass of 36 kDa, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The toxin possessed casein-hydrolyzing activity, which was inhibited specifically by metal chelators, indicating that the toxin is a metalloprotease. The gene encoding the lambda-toxin (lam), which was shown by Southern analysis to be located on a 70-kb plasmid, was cloned into Escherichia coli cells. Nucleotide and N-terminal amino acid sequencing revealed that the lam gene encodes a 553-amino-acid protein, which is processed into a mature form, the molecular mass of which was calculated to be 35,722 Da. The deduced amino acid sequence of the mature enzyme contains an HEXXH motif characteristic of zinc metalloproteases and is homologous to other known enzymes belonging to the thermolysin family. The purified toxin degraded various biologically important substances, such as collagen, fibronectin, fibrinogen, immunoglobulin A, and the complement C3 component. It caused an increase in vascular permeability and hemorrhagic edema on injection into the dorsal skin of mice. These results suggest that the toxin contributes to the pathogenesis of histolytic infection by lambda-toxin-producing C. perfringens.

Actions of Vibrio vulnificus metalloprotease on human plasma proteinase-proteinase inhibitor systems: a comparative study of native protease with its derivative modified by polyethylene glycol

Vibrio vulnificus, an opportunistic human pathogen causing wound infection and septicemia, produces a metalloprotease (VVP) which is suspected to be a virulent determinant. The interactions of VVP, as well as its derivative (PEG1-VVP) modified with polyethylene glycol, with a variety of human plasma proteins were investigated. We found that native VVP and its derivative were able to act directly on many biologically important human plasma proteins even in the presence of alpha-macroglobulin, the sole plasma inhibitor of native VVP. The activities of both classical and alternative pathways of the complement cascade system were drastically abolished by incubation with either VVP. Furthermore, these proteases rapidly digested the A alpha-chain of human fibrinogen into fragment(s) with no clotting ability. Therefore both VVPs are thought to function as a fibrinogenolytic enzyme, causing delay of the coagulation reaction. VVP and PEG1-VVP were also shown to destroy plasma proteinase inhibitors including alpha 1-proteinase inhibitor, a major inhibitor in human plasma. Because endogenous proteolytic enzymes and their inhibitors are indispensable in maintaining physiological homeostasis, these findings suggest that VVP (and PEG1-VVP) may cause an imbalance of human plasma proteinase-proteinase inhibitor systems, thus eliciting an immunocompromised state in the host and facilitating the development of a systemic V. vulnificus infection such as septicemia.

Vibrio vulnificus may produce a metalloprotease causing an edematous skin lesion in vivo

Vibrio vulnificus, an opportunistic human pathogen, secretes a metalloprotease which has been suspected of being the causative factor for edematous skin lesions. The antibody against alpha-macroglobulin, the sole plasma inactivator of V. vulnificus metalloprotease, delayed clearance of the protease administered into dorsal skin, and increased the edema-forming ability of living bacterial cells. The derivative of the protease, which is resistant to the inactivating action of alpha-macroglobulin, was not excluded from the dorsal skin. Furthermore, the vibrio inoculated into the mammalian serum was found to produce the protease in adequate amounts. These results suggest that V. vulnificus secretes a metalloprotease into the interstitial-tissue space, resulting in the development of an edematous skin lesion, and that the protease is immediately inactivated by alpha-macroglobulin and subsequently excluded.