Objective:To develop a recombinant protein vaccine based on KPC-2, a drug resistance target in Klebsiella pneumoniae, and evaluate its immunogenicity, protective efficacy and mechanism in a mouse model of pneumonia. Methods:KPC-2 was expressed in Escherichia coli and purified using GST affinity chromatography. A recombinant protein vaccine was prepared with KPC-2 and used to immunize New Zealand rabbits through subcutaneous injection. Serum samples were isolated from cardiac blood and Protein G chromatography was used to purify polyclonal antibodies against KPC-2. Opsonophagocytic killing assay was used to assess the bactericidal activity of the polyclonal antibodies in vitro. Female BALB/c mice were immunized three times with the recombinant protein vaccine, and the titers of specific IgG antibodies in serum were measured by indirect ELISA. One week after the last vaccination, the mice were infected with Klebsiella pneumoniae strain SRT through tracheal intubation, and received a single intravenous dose of meropenem (0.1 mg) 1 h later. The protective efficacy of the KPC-2 recombinant protein vaccine was evaluated by comparing the survival rates, bacterial colonization and histopathological changes between vaccine group and adjuvant group as well as the survival rates between meropenem group and normal saline group. Moreover, the protective efficacy of polyclonal antibodies against KPC-2 was evaluated through passive immunization. Results:The level of specific IgG antibodies in serum was significantly higher in the vaccine group than in the adjuvant group ( t=4.325, P<0.05). The survival rate in the vaccine group was also higher than that of the adjuvant group [70% (7/10) vs 10% (1/10), P<0.05]. Furthermore, lung inflammation was less severe and bacterial burden was reduced in the vaccine group as compared with those of the control group ( t=3.127, P<0.05). Both active and passive vaccination strategies demonstrated strong protective efficacy against Klebsiella pneumoniae infection, and had a synergistic effect when used in combination with antibiotic therapy. The polyclonal antibodies against KPC-2 had bactericidal activity in vitro ( t=5.427, P<0.05). Conclusions:The prepared KPC-2 vaccine has better immunogenicity and protective efficacy. It can induce strong humoral immune responses. This study suggest that drug resistance target may be used as a candidate antigen for future vaccine development.

Objective:To investigate the effects of SINC, a novel secreted protein of Chlamydia psittaci, on the apoptosis of host cells and the regulatory role of mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling pathway in it. Methods:HeLa cells were treated with recombinant SINC. The expression of Bax and Bcl-2 at protein level and the phosphorylation of ERK1/2 were analyzed by Western blot. Hoechst 33258 staining was used to detect the apoptosis of HeLa cells after SINC stimulation. Moreover, HeLa cells were pretreated with MEK1/2 inhibitor U0126 (50 μmol/L), and then stimulated with different concentrations of SINC for different time. Flow cytometry was used to detect the changes in cell apoptosis rates and Western blot was performed to detect the expression of Bax and Bcl-2 at protein level.Results:Treating HeLa cells with 10 μg/ml of SINC for 18 h resulted in down-regulated Bax and up-regulated Bcl-2 at protein level. Besides, the ratio of Bax/Bcl-2 was the lowest and a significant increase in the ratio of phosphorylated ERK1/2 (p-ERK1/2) to ERK1/2 was observed. Hoechst 33258 staining showed that the number of apoptotic bodies decreased significantly after stimulating HeLa cells with 5, 10 and 15 μg/ml of SINC. In the presence of MEK1/2 inhibitor U0126, the expression of Bcl-2 at protein level was down-regulated, while the expression of cleaved PARP was significantly up-regulated. Flow cytometry showed a significantly enhanced apoptosis of HeLa cells.Conclusions:SINC can inhibit the apoptosis of HeLa cells through activating the MAPK/ERK signaling pathway.

Objective:To investigate whether tetrandrine could be used as an agonist of cGAMP to enhance the activation of cGAS-STING signaling pathway and analyze the antiviral function of tetrandrine.Methods:THP1-Lucia-ISRE and RAW-Lucia-ISRE cells were incubated with different doses of tetrandrine in combination with cGAMP, respectively. IRF3 reporter activity was analyzed by luciferase reporter assay. Western blot was used to detect the activation of cGAS-STING signaling pathway. The expression of IFN-β, CXCL10 and CCL5 at mRNA level was quantified by real-time quantitative PCR. The expression of IFN-β at protein level was assessed by ELISA. HeLa cells stably expressing STING-GFP gene (HeLa-STNG-GFP cells) were constructed and stimulated with tetrandrine and cGAMP, then puncta-like structures were imaged by ZEISS LSM780. THP1-Lucia-ISRE cells were infected with herpes simplex virus type 1 (HSV-1) in the presence or absence of tetrandrine or cGAMP. The antiviral function of tetrandrine was analyzed by Western blot and fluorescence intensity assay.Results:Tetrandrine enhanced cGAMP-mediated IRF3 responses and activated cGAS-STING signaling pathway in combination with cGAMP. Tetrandrine combined with cGAMP triggered STING translocation and the formation of puncta-like structures in HeLa-STNG-GFP cells. The titer of HSV-1, the expression of HSV-glycoprotein D/UL30 and the fluorescence intensity of HSV-GFP were all decline after treating HSV-1-infected THP1-Lucia-ISRE cells with tetrandrine and cGAMP.Conclusions:Tetrandrine combined with cGAMP activates cGAS-STING signaling pathway, thus enhancing the host antiviral response.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by Dabie bandavirus (DBV), characterized by fever, leukopenia, thrombocytopenia and multiple organ damage. Immune dysfunction induced by DBV is closely associated with the pathogenesis of SFTS. Monocytes/macrophages that are essential in innate immunity are the target cells of DBV, and their interaction with DBV plays an important role in the pathogenesis of SFTS. The review summarizes the progress in the features and mechanisms of monocyte/macrophage-mediated immune responses to DBV infection.

The immune response against infection is a multifaceted process encompassing the activation and migration of diverse immune cells, as well as the clearance of pathogens. The behaviors of immune cells and the identification of pathogens play pivotal roles as indicators for disease diagnosis and prediction. In recent years, the utilization of microfluidic chip technology has gained substantial attention within the areas of biology, pharmacology, and clinical research and diagnosis. This is primarily attributed to the numerous advantages it offers, including miniaturization, enhanced throughput, heightened sensitivity, expedited analysis, and reduced sample consumption. As a result, microfluidic technology has facilitated the development and utilization of immune cell behavioral assays, bacterial growth studies, and drug-screening assays. This paper is to review the application of microfluidic technology in the field of anti-infection immunity research, focusing on the analysis of migratory behavior of innate immune cells, deformation of their nuclei, and rapid identification of pathogenic bacteria and viruses. The primary objective of this review is to advance the application of microfluidic technology in research on both anti-infection immunity and clinical diagnosis.

Outer membrane vesicle (OMV), originating from the outermost membrane of cells, is the extracellular vesicles released by gram-negative bacteria, containing bacterial outer membrane components such as phospholipids, lipopolysaccharide (LPS), outer membrane protein, and bacterial-specific antigens. OMV plays an important role in bacterial physiology and pathogenesis, involving in biofilm formation, horizontal gene transfer, stress and inflammatory responses, and delivery of toxins and other biomolecules. It also plays a vital role in immune regulation and the establishment and maintenance of balanced intestinal microflora. This article provides an overview of the roles of OMV in bacterial infections and immune regulation and the potential application value of OMV in tumor-targeted therapy and new vaccine preparation in the hope to provide new ideas for the prevention and treatment of bacterial infections.

Objective:To establish an antibody expression system to reduce the antibody-dependent enhancement (ADE) effect of target antibody.Methods:Site-directed mutagenesis was used to mutate the 234 and 235 sites of the Fc region of the mammalian cell antibody expression vector-L234A and L235A to establish the antibody expression vector pFRT-IgG1κ-FcM. An antibody Wt-WNV with significant ADE effect obtained in previous work was selected and expressed by the pFRT-IgG1κ-FcM system to obtain mutant antibody FcM-WNV. The binding ability of FcM-WNV to target antigen West Nile virus envelope protein-DⅢ (WNV E-DⅢ) was detected by ELISA, and the its binding ability to human high-affinity IgG Fc receptor hFcγRⅠ (hCD64 ) was analyzed by flow cytometry. The neutralizing activity of FcM-WNV in vitro was detected by pseudovirus infection of host cells (BHK21 and K562). Results:The expression levels of FcM-WNV and Wt-WNV were comparable, and FcM-WNV could recognize and bind to WNVE-DIII in a concentration-dependent manner. Compared with Wt-WNV, the binding ability of FcM-WNV to hCD64 was significantly weakened, showing a significant decrease in fluorescence intensity. Consistent with the previous experimental results, Wt-WNV at a concentration of 5 μg/ml significantly enhanced the infection of K562 by WNV pseudovirus, while FcM-WNV at a concentration of 5 μg/ml could effectively block pseudovirus infection in both K562 and BHK21 cells.Conclusions:The established antibody expression system can effectively reduce the ADE effect of the target antibody.

Objective:To investigate the expression of IL-18, IL-18-binding protein a(IL-18BPa) and IL-18 receptor α(IL-18Rα) by peripheral blood CD4 + Th17 cells of patients with allergic rhinitis (AR) and the effects of allergens on their expression. Methods:This study enrolled 45 outpatients with AR and 23 healthy control subjects receiving physical examination in the First Affiliated Hospital of Jinzhou Medical University from October 2019 to September 2020. According to the results of skin prick test, the 45 patients were divided into two groups: AR group with positive results (24 cases) and nAR group with negative results (21 cases). Blood samples of them were collected. Flow cytometry was used to analyze the effects of allergens on the expression of IL-18, IL-18BPa and IL-18Rα at protein level by peripheral blood CD4 + Th17 cells. The level of IL-17A in plasma was measured by Bioplex system, and its correlation with the percentage of IL-18 + Th17 cells was analyzed. Results:Compared with the healthy control group, the AR group showed increased ratios of CD4 + Th17 and IL-18 + Th17 cells ( P<0.01), decreased ratio of IL-18BPa + Th17 cells ( P<0.01), enhanced mean fluorescence intensity (MFI) of IL-18BPa ( P<0.01) and reduced MFI of IL-18Rα ( P<0.01); the nAR group showed enhanced MFI of IL-18BPa ( P<0.000 1) and reduced MFI of IL-18Rα ( P<0.000 1). The ratio of IL-18 + Th17 cells and the MFI of IL-18Rα in the AR group were higher than those in the nAR group ( P<0.05, P<0.01). House dust mite extract and Platanus pollen extract induced the expression of IL-18 and IL-18BPa by CD4 + Th17 cells of AR patients ( P<0.05). Moreover, house dust mite extract directly induced the CD4 + Th17 cells isolated from the healthy control subjects to express IL-18 and IL-18R ( P<0.05). Compared with healthy control subjects, AR patients had higher level of IL-17A in plasma and it was moderately correlated with the ratio of IL-18 + Th17 cells ( P<0.05). Conclusions:Allergens may be involved in the pathogenesis of AR by inducing blood CD4 + Th17 cells to express IL-18 and IL-18Rα.

Objective:To construct pancreatic cancer cell lines expressing luciferase and mesothelin (MSLN), and evaluate the feasibility of using them as target cells in analyzing the cytotoxicity activity of immune cells.Methods:Lentiviral vectors expressing luciferase and MSLN genes were constructed, and pancreatic cancer cell lines were infected after lentivirus packaging. Single-cell clones were obtained by limited dilution following antibiotic screening, and the stable expression of the target genes were verified. These cells were used as target cells to detect the cytotoxicity of immune cells by real-time cell analysis (RTCA) and luciferase activity. Besides, these luciferase-expressing cells were transplanted into B-NDG mice to establish the animal models of pancreatic cancer, and in vivo optical imaging technology was used to detect the expression of luciferase and monitor the tumor growth in mice. The cytotoxicity of chimeric antigen receptor T (CAR-T) cells was verified in these animal models. Results:Three pancreatic cancer cell lines, panc-1-luc, panc-1-luc-MSLN and capan-2-luc, that could stably express luciferase and MSLN genes were successfully constructed. The expression of the reporter gene in these cells were high, and positively correlated with the number of cells. There were 95.6% of panc-1-luc-MSLN cells expressing MSLN. MSLN-CAR-T cells had specific killing effect on MSLN-positive panc-1-luc-MSLN cells and capan-2-luc cells, with the minimum killing rates of (70.00±18.19)% and (57.00±5.29)%, respectively. But they had no cytotoxicity to MSLN-negative panc-1-luc cells. RTCA results showed that MSLN-CAR-T cells were able to lyse all three pancreatic cancer cell lines, and the minimum killing rates were (56.33±7.64)%, (93.00±2.65)% and (26.33±28.15)%, respectively. The killing of target cells by NK-92MI cells was not depended on MSLN expression. The cytotoxicity in the mice models of pancreatic cancer was consistent with the results in vitro. The in vivo and in vitro test results suggested that the expression of luciferase by target cells could reflect the cytotoxicity of immune cells. Conclusions:This study establishes three pancreatic cancer cell lines stably expressing luciferase, which can be used to evaluate the cytotoxicity of immunotherapy products targeting tumor cells in vitro and in vivo.

Objective:To investigate the role of the clearance of exogenous myelin antigen in experimental autoimmune encephalomyelitis (EAE).Methods:EAE was induced in C57BL/6J mice by subcutaneous immunization with myelin oligodendrocyte glycoprotein 35-55 (MOG 35-55) or FITC-MOG 35-55. The concentration of exogenous myelin antigen was assessed by analyzing the proliferation of the transferred CFSE-labeled mT/mG-2D2 CD4 + T cells in spleen tissues. The release of exogenous myelin antigen from the inoculation sites was analyzed by immunohistochemistry and flow cytometry. HE staining was used to investigate the mechanism underlying the rapid clearance of exogenous myelin antigen. The role of the clearance of exogenous myelin antigen in EAE was investigated by comparative analysis of EAE induced by subcutaneous immunization in the back and footpads, and analyzing the therapeutic effect of soluble MOG 35-55. Results:The proliferation of mT/mG-2D2 CD4 + T cells in mice was enhanced on day 2 than on day 7 after immunization [(52.6±6.8)% vs (18.5±4.9)%, P<0.01]. There was no significant difference in the proliferation of mT/mG-2D2 CD4 + T cells between EAE mice (day 13) and naive mice [(4.4±1.5)% vs (2.5±1.4)%, P=0.11]. Immunohistochemistry and flow cytometry showed that MOG 35-55 was released and engulfed by CD11b + cells at the inoculation sites, and no more MOG 35-55 was released at the onset of EAE. HE staining showed that granuloma that formed surrounding the antigen emulsion during EAE development prevented antigen release from the emulsion, completely isolating the antigen from the peripheral immune system. The incidence of EAE was relatively low in mice immunized via footpads, which was related to the sustained release of MOG 35-55, but had no direct relation to CD4 + regulatory T cells. Continuous intraperitoneal injection of soluble MOG 35-55 could prevent and treat EAE. Conclusions:Exogenous myelin antigen has been completely cleared in EAE mice, and the occurrence of EAE depends on the clearance of the myelin antigen.