Objective:To investigate the effects of Vibrio vulnificus ( Vv) quorum-sensing protein LuxS on the homeostasis of pulmonary innate immune cells in sepsis-induced acute lung injury. Methods:This study constructed luxS knockout and complemented Vv strains. The time required for wild type, luxS knockout, and complemented Vv strains to grow to an absorbance of 600 nm in liquid medium was measured using a spectrophotometer. Iron-overloaded mice were intraperitoneally infected with 1×10 5 CFU of the above three kinds of Vv strains, respectively. Clinical scoring for sepsis-induced dyspnea was used to evaluate the respiratory quality in mice. At 7 h after infection, the pathological changes in lung tissues were observed by HE staining; the bacterial loads in lung tissues were measured; the single-cell suspension of lung tissues was analyzed by flow cytometry. Uniform manifold approximation and projection (UMAP) was used to reduce the dimension of the distribution of CD45 + immune cells in lung tissues of mice in the PBS control group and infection groups with different strains. The frequency and absolute number of innate immune cells in lung tissues were analyzed by multicolor flow cytometry. One-way analysis of variance and t test were used for statistical analysis. Results:There was no significant difference in the growth rate of wild type, luxS knockout, and complemented Vv strains in liquid medium. Compared with the mice infected with the wild type or complemented strain, the mice infected with the luxS knockout strain exhibited overall alleviated respiratory difficulty, decreased inflammatory cell infiltration in lung tissues, and reduced bacterial load in lung tissues ( P<0.05). Besides, there was no significant difference in clinical respiratory scores, inflammatory cell infiltration, or bacterial loads between the mice infected with the complemented strain and wild type strain. UMAP analysis showed that compared with the mice infected with the luxS knockout strain, the mice infected with the wild type or complemented strain showed increased proportions of neutrophils and eosinophils in lung tissues. Results of multicolor flow cytometry analysis further verified that the proportions of neutrophils and eosinophils were significantly lower in the mice infected with the luxS knockout strain than in the mice infected with wild type or complemented strain ( P<0.01, P<0.000 1), while the proportion of alveolar macrophages was significantly higher as compared with that in the mice infected with wild type or complemented strain ( P<0.01). Conclusion:During Vv infection, LuxS may promote acute lung injury by affecting the homeostasis of neutrophils, eosinophils and resident macrophages in lung tissues.

Objective:To investigate the role of autophagy in the regulatory of phagocytosis in Vibrio vulnificus ( V. vulnificus)-infected murine macrophages. Methods:The expression of cellular autophagy-related proteins in PBS-treated and V. vulnificus-infected RAW264.7 and BMMφ cells was detected by Western blot. The co-localization of V. vulnificus-GFP and LC3Ⅱ protein in V. vulnificus-GFP-infected RAW264.7 and BMMφ cells were detected using confocal microscopy. The phagocytosis of V. vulnificus in V. vulnificus-GFP-infected RAW264.7 and BMMφ cells with or without autophagy inhibition using Bafilomycin A1 was detected by flow cytometry. Results:The up-regulated levels of Atg7, Atg12 and Atg16L1 proteins, increased LC3Ⅱ/actin ratio, as well as down-regulated p62 protein levels were significantly detected in V. vulnificus-infected RAW264.7 and BMMφ cells. The co-localization of V. vulnificus-GFP and LC3Ⅱ protein was clearly observed in V. vulnificus-GFP-infected RAW264.7 and BMMφ cells. Enhanced phagocytosis of V. vulnificus and increased autophagy were exhibited in V. vulnificus-GFP-infected RAW264.7 and BMMφ cells, while weakened phagocytosis, accumulation of Atg7, Atg12, Atg16L1, LC3Ⅱ and p62 protein levels, as well as blocking autophagy flux were detected in those cells within autophagy inhibition using Bafilomycin A1. Conclusion:Autophagy induced by V. vulnificus infection could promote phagocytosis of V. vulnificus in macrophages.

Objective:To investigate the effects of Vibrio vulnificus ( Vv) quorum-sensing protein LuxS on the homeostasis of pulmonary innate immune cells in sepsis-induced acute lung injury. Methods:This study constructed luxS knockout and complemented Vv strains. The time required for wild type, luxS knockout, and complemented Vv strains to grow to an absorbance of 600 nm in liquid medium was measured using a spectrophotometer. Iron-overloaded mice were intraperitoneally infected with 1×10 5 CFU of the above three kinds of Vv strains, respectively. Clinical scoring for sepsis-induced dyspnea was used to evaluate the respiratory quality in mice. At 7 h after infection, the pathological changes in lung tissues were observed by HE staining; the bacterial loads in lung tissues were measured; the single-cell suspension of lung tissues was analyzed by flow cytometry. Uniform manifold approximation and projection (UMAP) was used to reduce the dimension of the distribution of CD45 + immune cells in lung tissues of mice in the PBS control group and infection groups with different strains. The frequency and absolute number of innate immune cells in lung tissues were analyzed by multicolor flow cytometry. One-way analysis of variance and t test were used for statistical analysis. Results:There was no significant difference in the growth rate of wild type, luxS knockout, and complemented Vv strains in liquid medium. Compared with the mice infected with the wild type or complemented strain, the mice infected with the luxS knockout strain exhibited overall alleviated respiratory difficulty, decreased inflammatory cell infiltration in lung tissues, and reduced bacterial load in lung tissues ( P<0.05). Besides, there was no significant difference in clinical respiratory scores, inflammatory cell infiltration, or bacterial loads between the mice infected with the complemented strain and wild type strain. UMAP analysis showed that compared with the mice infected with the luxS knockout strain, the mice infected with the wild type or complemented strain showed increased proportions of neutrophils and eosinophils in lung tissues. Results of multicolor flow cytometry analysis further verified that the proportions of neutrophils and eosinophils were significantly lower in the mice infected with the luxS knockout strain than in the mice infected with wild type or complemented strain ( P<0.01, P<0.000 1), while the proportion of alveolar macrophages was significantly higher as compared with that in the mice infected with wild type or complemented strain ( P<0.01). Conclusion:During Vv infection, LuxS may promote acute lung injury by affecting the homeostasis of neutrophils, eosinophils and resident macrophages in lung tissues.

Objective:To investigate the role of autophagy in the regulatory of phagocytosis in Vibrio vulnificus ( V. vulnificus)-infected murine macrophages. Methods:The expression of cellular autophagy-related proteins in PBS-treated and V. vulnificus-infected RAW264.7 and BMMφ cells was detected by Western blot. The co-localization of V. vulnificus-GFP and LC3Ⅱ protein in V. vulnificus-GFP-infected RAW264.7 and BMMφ cells were detected using confocal microscopy. The phagocytosis of V. vulnificus in V. vulnificus-GFP-infected RAW264.7 and BMMφ cells with or without autophagy inhibition using Bafilomycin A1 was detected by flow cytometry. Results:The up-regulated levels of Atg7, Atg12 and Atg16L1 proteins, increased LC3Ⅱ/actin ratio, as well as down-regulated p62 protein levels were significantly detected in V. vulnificus-infected RAW264.7 and BMMφ cells. The co-localization of V. vulnificus-GFP and LC3Ⅱ protein was clearly observed in V. vulnificus-GFP-infected RAW264.7 and BMMφ cells. Enhanced phagocytosis of V. vulnificus and increased autophagy were exhibited in V. vulnificus-GFP-infected RAW264.7 and BMMφ cells, while weakened phagocytosis, accumulation of Atg7, Atg12, Atg16L1, LC3Ⅱ and p62 protein levels, as well as blocking autophagy flux were detected in those cells within autophagy inhibition using Bafilomycin A1. Conclusion:Autophagy induced by V. vulnificus infection could promote phagocytosis of V. vulnificus in macrophages.

LC3-associated phagocytosis (LAP) is a special phagocytosis occurring at the intersection of the two pathways of phagocytosis and autophagy. A hallmark event of the LAP process is the recruitment of microtubule-associated proteinⅠlight chain type 3-Ⅱ(LC3Ⅱ) to the phagosome surface of the monolayer membrane structure. The LAP pathway relies on the functions of the RUN domain and cysteine-rich domain containing, Beclin 1-interacting protein (Rubicon) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. The LC3-associated phagosome (LAPosome) binds to the lysosome to digest and degrade the contents. In recent years, increasing studies have found that LAP plays an important role in the infections caused by pathogenic microorganisms including fungi and bacteria. LAP is a crucial way in the host to resist and degrade the infection of pathogenic microorganisms. However, some pathogenic microorganisms can effectively escape from LAP in the host and even use LAPosome as a place for colonization and replication. This article summarized the recent progress in the role of LAP in host defense against pathogenic microorganism infection and the significance of it in the occurrence and development of diseases.

Objective:To investigate the role of NOD-like receptor protein 3 (NLRP3) in the regulation of phagocytosis in Vibrio vulnificus ( V. vulnificus)-infected macrophages. Methods:Expression profiles of phagocytosis-related genes in PBS- and V. vulnificus-infected J774A.1 cells were analyzed by RNA-Seq. NLRP3-knockout (NLRP3 KO) J774A.1 cells were constructed using CRISPR-Cas9 gene-editing system. The phagocytosis of V. vulnificus and pHrodo RED-labelled Escherichia coli ( E. coli) bioparticles in parental and NLRP3 KO J774A.1 cells was detected by flow cytometry. Real-time PCR was performed to measure the expression of Fgr2 b gene at mRNA level in PBS- and V. vulnificus-treated parental and NLRP3 KO J774A.1 cells. Results:The expression of 18 phagocytosis-related genes was upregulated in V. vulnificus-infected J774A.1 cells than in PBS-treated J774A.1 cells ( P<0.05). There was a 5 bp deletion in the exon 2 of NLRP3 gene in NLRP3 KO J774A.1 cells, resulting in frameshift mutation and complete loss of NLRP3 expression. NLRP3 KO J774A.1 cells exhibited enhanced phagocytosis of V. vulnificus and pHrodo RED-labelled E. coli bioparticles than parental J774A.1 cells ( P<0.05). Besides, the expression of Fgr2 b gene at mRNA level was significantly increased in V. vulnificus-infected NLRP3 KO J774A.1 cells than in parental J774A.1 cells ( P<0.05). Conclusions:The phagocytosis of V. vulnificus in macrophages could be negatively regulated by NLRP3, which was possibly mediated through the regulation of Fgr2 b gene expression.

Objective:To investigate the effects of TNF-α knockout on liver and spleen neutrophil responses to Vibrio vulnificus bloodstream infection in a mouse model. Methods:(1) TNF-α-knockout (TNF-α -/-) and wild-type (WT) C57BL/6J mice aged 6-8 weeks were randomly divided into four groups with six in each group: uninfected WT group, infected WT group, uninfected TNF-α -/- group and infected TNF-α -/- group. The mouse model of bloodstream infection was constructed by intraperitoneal injection of Vibrio vulnificus CGMCC1.1758 (2×10 8 CFU/200 μl), while the mice in the uninfected groups were injected intraperitoneally with equal amount of PBS. (2) Liver immune cells and splenocytes were isolated 4 h after infection and subjected to analyze the percentages and numbers of neutrophils, and the changes in cell viability, cellular reactive oxygen species (ROS) level and phagocytosis by flow cytometry. In addition, effects of Vibrio vulnificus bloodstream infection on mTOR signaling pathway in murine neutrophils were evaluated in vivo. Results:(1)Compared with the uninfected WT group, the percentages and numbers of neutrophils in liver and spleen tissues of the infected WT group increased significantly. The percentage and number of liver neutrophils were significantly higher in the infected TNF-α -/- group than in the infected WT group, but no significant difference in spleen neutrophils was detected between the two groups. (2) Compared with the infected WT group, the phagocytosis of liver neutrophils rather than that of spleen neutrophils was enhanced in the infected TNF-α -/- group. (3) The survival rates of neutrophils in both liver and spleen were decreased, while the cellular ROS level was significantly increased in the infected WT group compared with those of the uninfected WT group. Compared with the infected WT group, the infected TNF-α -/- group had increased survival rates of both liver and spleen neutrophils, but decreased level of ROS. (4) The levels of p-AKT (S473) in liver and spleen neutrophils of the infected WT group were lower than those of the uninfected WT group. Compared with the infected WT group, the infected TNF-α -/- group had lower level of p-AKT (S473) in liver neutrophils, but higher p-AKT (S473) level in spleen neutrophils. There were no significant differences in p-4E-BP1(T37/46) levels between the uninfected WT group and the infected WT group. The p-4E-BP1 (T37/46) level in liver neutrophils was lower in the infected TNF-α -/- group than in the infected WT group, but no significant difference in p-4E-BP1 (T37/46) levels in spleen neutrophils was observed between the two groups. Conclusions:TNF-α had different effects on the neutrophils in spleen and liver tissues of mice with Vibrio vulnificus bloodstream infection. It played a critical role in regulating the recruitment, phagocytic function and mTOR signaling of liver neutrophils after Vibrio vulnificus infection in vivo.

Objective:To investigate the cytotoxicity of a recombinant Vibrio vulnificus cytolysin membrane pore-forming peptide (rMpf) to J774A.1 cells as well as its influences on reactive oxygen species (ROS) and lysosomes, and to analyze the cellular localization of the rMpf. Methods:The rMpf was expressed using an Escherichia coli expression system and then used to treat murine J774A.1 cells in vitro. The viability of rMpf- and PBS-treated J774A.1 cells and the levels of ROS and lysosomes in these cells were analyzed by flow cytometry. Confocal microscopy was used to observe the cellular localization of rMpf in the J774A.1 cells. Results:No significant differences in cell viability, ROS production or lysosome formation in J774A.1 cells were found between low-dose (4 μg/ml) rMpf-treated and untreated groups. However, the cell viability, ROS production and lysosome formation were significantly decreased after treating J774A.1 cells with higher doses of rMpf (20 and 60 μg/ml). Moreover, the rMpf was found to localize in both the cytoplasm and nuclei of J774A.1 cells in a dose-dependent manner.Conclusions:The rMpf could localize in both the cytoplasm and nuclei of J774A.1 cells. It would inhibit the cellular ROS production and lysosome formation to damage macrophage function. This study provided a novel sight for understanding the cytotoxic domain and pathogenesis of Vibrio vulnificus cytolysin and other membrane pore-forming cytolysins.

Objective:The cellular immunity of 5 Mycobacterium tuberculosis recombinant proteins and their compositions was evaluated.Method:A total of 88 fresh venous blood from peripheral heparin anticoagulant population, 42 of which were from tuberculosis patients treated by The Tuberculosis Prevention and Treatment Center of Changping District, Beijing, and 46 of healthy volunteers were provided by the Infection Diseases of Chinese Center for Disease Control and Prevention. Healthy volunteers without a history of tuberculosis exposure and any clinical signs and symptoms. Using the Mycobacterium tuberculosis standard strain H37Rv DNA as a template, complete genes of the selected 5 recombinant proteins Rv3874, Rv3875, Rv2031c, Rv1411c and Rv3418c by PCR amplified; 5 recombinant proteins were cloned, expressed and purified as stimulants by genetic recombination and protein purification techniques, and the effector T cell enzyme-linked immunospot assay (ELISPOT) was used to detect cellular immunity in the population.Results:The recombinant proteins Rv3874, Rv3875, Rv2031c, Rv1411c and Rv3418c were successfully cloned, expressed and purified; And the sensitivities were 50.00%, 71.43%, 69.04%, 73.81% and 76.19%, and the specificities were 86.96%, 76.09%, 71.74%, 39.13% and 36.96%. In addition, the positive predictive value, negative predictive value, area under the curve and Youden index were 52.46% to 77.78%, 62.96% to 74.47%, 0.511 to 0.754 and 0.129 to 0.475, respectively. Except for Rv1411c and Rv3418c, the number of spot-forming cell (SFC) detected by Rv3874, Rv3875 and Rv2031c in tuberculosis patients was higher than healthy volunteers, and the differences were statistically significant ( P<0.001). Among the 26 compositions composed of 5 recombinant proteins, the sensitivity was 80.95% to 95.24%, and the specificity was 68.89% to 24.44%. As the number of recombinant proteins in the composition increases, the sensitivity gradually increased, but the specificity decreased. Conclusion:The recombinant proteins of Mycobacterium tuberculosis Rv3874, Rv3875 and Rv2031c have strong ability to stimulate T cells to produce immune response, and have certain antigenicity. The efficacy of Rv1411c and Rv3418c alone as diagnostic antigens is not ideal, and the composition composed of multi-component antigens has certain application value. This article provides experimental evidence for the immune diagnosis of tuberculosis and the preparation of new anti-tuberculosis vaccines.

Objective:The cellular immunity of 5 Mycobacterium tuberculosis recombinant proteins and their compositions was evaluated.Method:A total of 88 fresh venous blood from peripheral heparin anticoagulant population, 42 of which were from tuberculosis patients treated by The Tuberculosis Prevention and Treatment Center of Changping District, Beijing, and 46 of healthy volunteers were provided by the Infection Diseases of Chinese Center for Disease Control and Prevention. Healthy volunteers without a history of tuberculosis exposure and any clinical signs and symptoms. Using the Mycobacterium tuberculosis standard strain H37Rv DNA as a template, complete genes of the selected 5 recombinant proteins Rv3874, Rv3875, Rv2031c, Rv1411c and Rv3418c by PCR amplified; 5 recombinant proteins were cloned, expressed and purified as stimulants by genetic recombination and protein purification techniques, and the effector T cell enzyme-linked immunospot assay (ELISPOT) was used to detect cellular immunity in the population.Results:The recombinant proteins Rv3874, Rv3875, Rv2031c, Rv1411c and Rv3418c were successfully cloned, expressed and purified; And the sensitivities were 50.00%, 71.43%, 69.04%, 73.81% and 76.19%, and the specificities were 86.96%, 76.09%, 71.74%, 39.13% and 36.96%. In addition, the positive predictive value, negative predictive value, area under the curve and Youden index were 52.46% to 77.78%, 62.96% to 74.47%, 0.511 to 0.754 and 0.129 to 0.475, respectively. Except for Rv1411c and Rv3418c, the number of spot-forming cell (SFC) detected by Rv3874, Rv3875 and Rv2031c in tuberculosis patients was higher than healthy volunteers, and the differences were statistically significant ( P<0.001). Among the 26 compositions composed of 5 recombinant proteins, the sensitivity was 80.95% to 95.24%, and the specificity was 68.89% to 24.44%. As the number of recombinant proteins in the composition increases, the sensitivity gradually increased, but the specificity decreased. Conclusion:The recombinant proteins of Mycobacterium tuberculosis Rv3874, Rv3875 and Rv2031c have strong ability to stimulate T cells to produce immune response, and have certain antigenicity. The efficacy of Rv1411c and Rv3418c alone as diagnostic antigens is not ideal, and the composition composed of multi-component antigens has certain application value. This article provides experimental evidence for the immune diagnosis of tuberculosis and the preparation of new anti-tuberculosis vaccines.