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The vibrio pathogenicity island-encoded mop protein modulates the pathogenesis and reactogenicity of epidemic vibrio
Dalin Zhang1, Zheng Xu, Weiyun Sun
1Department of Epidemiology and Preventive Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
Abstract:
Epidemic Vibrio cholerae possess the VPI (Vibrio pathogenicity island) essential virulence gene cluster. The VPI is 41.2 kb in size and encodes 29 potential proteins, several of which have no known function. We show that the VPI-encoded Orf4 is a predicted 34-kDa periplasmic protein containing a zinc metalloprotease motif. V. cholerae seventh-pandemic (El Tor) strain N16961 carrying an orf4 mutation showed no obvious difference relative to its parent in the production of cholera toxin and the toxin-coregulated pilus, motility, azocasein digestion, and colonization of infant mice. However, analysis of rabbit ileal loops revealed that the N16961 orf4 mutant is hypervirulent, causing increased serosal hemorrhage and reactogenicity compared to its parent. Histology revealed a widening of submucosa, with an increase in inflammatory cells, diffuse lymphatic vessel dilatation, edema, endothelial cell hypertrophy of blood vessels, blunting of villi, and lacteal dilatation with lymphocytes and polymorphonuclear leukocytes. The mutant could be complemented in vivo with an orf4 gene on a plasmid but not with an orf4 gene containing a site-directed mutation in the putative zinc metalloprotease motif. Although its mechanism of its action is being studied further, our results suggest that the Orf4 protein is a zinc metalloprotease that modulates the pathogenesis and reactogenicity of epidemic V. cholerae. Based on our findings, we name this VPI-encoded protein Mop (for modulation of pathogenesis).
Insights
A newly identified Vibrio cholerae protein, Mop (modulation of pathogenesis), acts as a zinc metalloprotease. This protein modulates cholera
Area of Science:
- Microbiology
- Molecular Biology
- Pathogenesis
Background:
- Vibrio cholerae, the causative agent of cholera, possesses the Vibrio pathogenicity island (VPI).
- The VPI gene cluster encodes essential virulence factors, including 29 potential proteins, some with unknown functions.
Purpose of the Study:
- To investigate the function of the VPI-encoded Orf4 protein in Vibrio cholerae pathogenesis.
- To characterize the enzymatic activity and role of Orf4 in disease progression.
Main Methods:
- Site-directed mutagenesis to create an orf4 deletion mutant and a catalytically inactive mutant.
- Phenotypic analysis of the mutant strains, including virulence assays in infant mice and rabbit ileal loops.
- Histological examination of infected tissues.
- Complementation studies in vivo.
Main Results:
- The VPI-encoded Orf4 protein is a zinc metalloprotease, now named Mop.
- A V. cholerae orf4 mutant exhibited hypervirulence in rabbit ileal loops, with increased hemorrhage and inflammation.
- Histology revealed significant tissue damage, including edema and inflammatory cell infiltration.
- Complementation with wild-type orf4 restored virulence, while a catalytically inactive mutant did not.
Conclusions:
- Orf4 (Mop) is a VPI-encoded zinc metalloprotease that modulates Vibrio cholerae pathogenesis and disease reactogenicity.
- Mop plays a crucial role in the inflammatory response and tissue damage observed during cholera infection.
- Targeting Mop may offer a novel therapeutic strategy for cholera.