Objective To evaluate whether Vibrio vulnificus secreted exotoxin-hemolysin (VVH) can activate platelet, an important blood immune cell, and to explore the possible molecular mechanism of platelet activation by VVH. Methods Transcriptomics and immunohistochemistry were used to analyze whether Vibrio vulnificus infection caused platelet activation in mice. Then, flow cytometry was used to identify whether VVH was the main stimulator of platelet activation. Naturally expressed VVH toxin was purified and prepared. The effects of extracellular and intracellular Ca²⁺ signal inhibitors on VVH activated platelets were evaluated by flow cytometry and Western blotting. The immune activation effect of VVH in the early stage of Vibrio vulnificus infection was analyzed in vivo. Results VVH was the main stimulator of platelet activation in Vibrio vulnificus culture supernatant. Natural VVH can induce the increase of P-selectin (CD62P) on platelet surface, the formation of platelet-neutrophil complex (PNC), and the release of platelet microvesicles. The activation mechanism may be related to the VVH pore-dependent Ca²⁺-calmodulin (CaM) -myosin light chain kinase (MLCK) signaling pathway, which led to the release of platelet alpha particles and cascade activation of platelets. In a mouse model of ALD infected by Vibrio vulnificus gavage, VVH was strongly associated with platelet activation. Conclusion This study shows that VVH is an important platelet activating molecule in the early stage of Vibrio vulnificus infection, and its induction of platelet activation may be related to the pathogenic process.
Animals ; Platelet Activation/drug effects* ; Hemolysin Proteins/pharmacology* ; Vibrio vulnificus/metabolism* ; Mice ; Blood Platelets/drug effects* ; Vibrio Infections/immunology* ; P-Selectin/metabolism* ; Bacterial Proteins ; Female

Vibrios are universal conditioned-pathogenic bacteria in marine culture environment, and the outbreak of vibrio disease resulted in a serious damage to aquaculture. Considering that vibrio disease in aquatic species, especially fishes, usually originated from mixed infection of different species (serotypes or subspecies) of vibrios, it is important to select the potential cross-protective protein antigens as candidates of polyvalent or combined vaccines. In present research, several strains of vibrios were isolated from infected large yellow croaker (Pseudosciaena crocea) and subsequently identified as six strains of V. harveyi, one V. parahaemolyticus and one V. alginolyticus by physiological, biochemical and molecular biological methods. Their outer membrane proteins (OMPs) were extracted and the SDS-PAGE and Western blotting results show that three immuno-blots with common molecular weight presented at approximate 45 kDa, 35 kDa and 22 kDa on their OMP electrophoretogram, indicating the existence of antigens with cross-protection in their OMPs. With the aids of combination of two-dimensional electrophoresis (2-D) and Western blotting and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), a deduced porin (GenBank Accession No. ZP_01260407) from V. alginolyticus and a maltoporin precursor (GenBank Accession No. NP_801154) from V. parahaemolyticus were able to react with polyclonal antibody to whole V. harveyi, suggesting these two proteins could act as the cross-protective antigens and the vaccines prepared with these porins would be probable to bring cross protection to three different vibrios.
Animals ; Antigens, Bacterial ; immunology ; Bacterial Outer Membrane Proteins ; immunology ; Cross Reactions ; Fish Diseases ; microbiology ; Perciformes ; microbiology ; Vibrio ; classification ; immunology ; isolation & purification ; pathogenicity ; Vibrio Infections ; microbiology