1.Inflammatory disorders that affect the cerebral small vessels.
Fei HAN ; Siyuan FAN ; Bo HOU ; Lixin ZHOU ; Ming YAO ; Min SHEN ; Yicheng ZHU ; Joanna M WARDLAW ; Jun NI
Chinese Medical Journal 2025;138(11):1301-1312
This comprehensive review synthesizes the latest advancements in understanding inflammatory disorders affecting cerebral small vessels, a distinct yet understudied category within cerebral small vessel diseases (SVD). Unlike classical SVD, these inflammatory conditions exhibit unique clinical presentations, imaging patterns, and pathophysiological mechanisms, posing significant diagnostic and therapeutic challenges. Highlighting their heterogeneity, this review spans primary angiitis of the central nervous system, cerebral amyloid angiopathy-related inflammation, systemic vasculitis, secondary vasculitis, and vasculitis in autoinflammatory diseases. Key discussions focus on emerging insights into immune-mediated processes, neuroimaging characteristics, and histopathological distinctions. Furthermore, this review underscores the importance of standardized diagnostic frameworks, individualized immunomodulation approaches, and novel targeted therapies to address unmet clinical demands.
Humans
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Cerebral Small Vessel Diseases/pathology*
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Inflammation/pathology*
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Cerebral Amyloid Angiopathy/pathology*
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Vasculitis, Central Nervous System/pathology*
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Vasculitis/pathology*
2.Research advances in the application of artificial intelligence in transfusion medicine
Xinxin YANG ; Shilan XU ; Bing HAN ; Lixin WANG ; Fu CHENG ; Dongmei YANG ; Bin TAN ; Li QIN ; Chunxia CHEN
Chinese Journal of Blood Transfusion 2025;38(11):1502-1513
Objective: To review the current development of artificial intelligence (AI) technology in the field of transfusion medicine. Methods: A systematic search was conducted in the Clarivate Web of Science Database from inception to December 2024 for literature related to AI and transfusion. A total of 4 775 publications were identified. Based on inclusion and exclusion criteria, 133 original studies were ultimately included and analyzed using a narrative synthesis approach. Results: Research on AI in transfusion has surged since 2020 (accounting for 77% of all publications), with China ranking second globally in publication volume. Among the included studies, 69.2% focused on predicting individual transfusion needs, followed by inventory management (8.3%), diagnosis and prediction of adverse transfusion reactions (6.0%), factors influencing transfusion outcomes (5.3%), blood group identification (5.3%), blood quality testing (4.5%), and precise blood volume measurement (1.5%). Additionally, 4.5% of the studies were published in journals with an impact factor greater than 10; 19.5% developed software or applications; 31.5% were multi-center studies; 48.1% utilized decision tree methods, while 31.5% employed neural network approaches; and 14.2% conducted external validation of the algorithms. Conclusion: AI demonstrates significant potential in transfusion risk prediction, decision support, and blood management. However, challenges remain, including limited model generalizability, insufficient algorithm interpretability, and barriers to clinical translation. The deep integration of AI with transfusion medicine will accelerate the advent of precision transfusion era, maximizing blood resource utilization, reducing waste, and ensuring transfusion safety.
3.Features of HBV RNA level in different stages of the natural history of chronic hepatitis B virus infection and its correlation with HBV DNA and HBsAg
Han GAO ; Juanli WU ; Yushuang ZHANG ; Yiheng ZHANG ; Lei WANG ; Tao LI ; Lixin ZHANG
Journal of Clinical Hepatology 2025;41(4):637-642
ObjectiveTo investigate the features of serum HBV RNA in different stages of the natural history of chronic hepatitis B virus (HBV) infection without antiviral treatment, as well as its correlation with serum HBV DNA and HBsAg. MethodsA total of 306 treatment-naïve patients with chronic HBV infection who attended Department of Infections Diseases and Hepatoloty, the Second Hospital of Shandong University from January 2023 to June 2024 were divided into six groups based on the different stages of natural history, i.e., HBeAg-positive chronic HBV infection group with 29 patients, HBeAg-positive chronic hepatitis B (CHB) group with 107 patients, HBeAg-negative chronic HBV infection group with 18 patients, HBeAg-negative CHB group with 60 patients, HBeAg-positive indeterminate-phase chronic HBV infection group with 7 patients, and HBeAg-negative indeterminate-phase chronic HBV infection group with 85 patients. Real-time isothermal RNA amplification was used to measure serum high-sensitivity HBV RNA. The Kruskal-Wallis H test was used for comparison between multiple groups of continuous data, while the Mann-Whitney U test was used for comparison between two groups. The Spearman method was used to investigate the correlation of HBV RNA with HBV DNA and HBsAg. ResultsThe HBeAg-positive chronic HBV infection group showed the highest level of serum HBV RNA [7.5 (7.4 — 7.9) log10 copies/mL], followed by the HBeAg-positive CHB group [7.4 (6.4 — 7.9) log10 copies/mL], the HBeAg-negative CHB group [4.5 (3.0 — 5.7) log10 copies/mL], and the HBeAg-negative chronic HBV infection group [1.0 (1.0 — 2.0) log10 copies/mL]; the HBeAg-positive indeterminate-phase chronic HBV infection group had a serum HBV RNA level of 3.9 (3.7 — 5.7) log10 copies/mL, and the HBeAg-negative indeterminate-phase chronic HBV infection group had a serum HBV RNA level of 2.0 (1.0 — 3.0) log10 copies/mL; there was a significant difference in serum HBV RNA level between the six groups (H=830.770, P<0.001). There was a significant difference in HBV RNA level between the HBeAg-positive chronic HBV infection group and all the other groups except the HBeAg-positive CHB group (all P<0.001). In the 306 patients with HBV infection, HBV RNA was strongly correlated with HBV DNA (r=0.92, P<0.001) and was moderately correlated with HBsAg (r=0.67, P<0.001). The correlation between serum HBV RNA and HBsAg in HBeAg-positive patients (r=0.61, P<0.001) was stronger than that in HBeAg-negative patients (r=0.31, P<0.001). For the patients with HBeAg-positive chronic HBV infection, the male patients with ALT>30 U/L and the female patients with ALT>19 U/L had a significantly lower serum HBV RNA level than the male patients with ALT≤30 U/L and the female patients with ALT≤19 U/L (P<0.001), and there was no significant difference in serum HBV RNA level between the latter group of patients and the HBeAg-positive CHB group (P>0.05). ConclusionIn patients with chronic HBV infection who do not receive antiviral therapy, there is a difference in serum HBV RNA level in different stages of natural history, and serum HBV RNA level has the strongest correlation with HBV DNA and a relatively weak correlation with HBsAg. In patients with HBeAg-positive chronic HBV infection, serum HBV RNA level in male patients with ALT>30 U/L and female patients with ALT>19 U/L are in the transition stage between HBeAg-positive chronic HBV infection and HBeAg-positive CHB.
4.Effect of cathepsin B/NLRP3 pathway on M1/M2 polarization of macrophages induced by LPS
Yibo WANG ; Yuting DAI ; Jiangxiao CAI ; Zhonglin LI ; Weiwei QIN ; Lixin SUN ; Wei HAN
Chinese Journal of Immunology 2025;41(1):63-68
Objective:To evaluate the effect of cathepsin B(CTSB)/NOD-like receptor pyrin domain containing 3(NLRP3)pathway on the polarization of macrophages induced by LPS.Methods:The well-growing RAW264.7 mouse mononuclear macrophage lines were cultured in vitro and divided into 3 groups(n=6)according to the random number table method:control group(C group),LPS group(L group)and LPS+CA074-me(CTSB inhibitors)group(B group).C group was cultured normally for 24 h,L group was cultured with LPS concentration of 1 μg/ml medium for 24 h.B group was pretreated with CTSB inhibitor CA074-me 30 μmol/L for 1 h before LPS induction,and co-cultured with LPS concentration of 1 μg/ml medium for 24 h.After 24 hours,the morphological changes of the cells were observed by microscope,the concentrations of IL-1β and IL-18 in the supernatant were determined by ELISA.The ex-pressions of cathepsin B precursor(pro-CTSB),mature cathepsin B(mature-CTSB),NLRP3,apoptosis-related speck protein(ASC)and apoptosis-related speck protein-1(caspase-1)were detected by Western blot.The mRNA expression levels of CD32,inducible ni-tric oxide synthase(iNOS),arginase 1(Arg-1)and CD206 were detected by qRT-PCR.The positive expression rates of M1 macro-phage surface marker CD86 and M2 macrophage surface marker CD206 were detected by flow cytometry.Results:Compared with group C,the morphology of cells in groups L and B became larger and pseudopodia appeared.The concentrations of IL-1β and IL-18 in cell supernatant were increased,the expressions of pro-CTSB,mature-CTSB,NLRP3,ASC and caspase-1 were increased,and the expressions of CD32,iNOS mRNA were up-regulated and the positive rates of CD86 and CD206 were increased(P<0.01).Arg-1 and CD206 mRNA in group B were up-regulated(P<0.01).Compared with group L,the pseudopodia of group B were reduced,and the morphology was closer to group C.The concentration of IL-1β and IL-18 in the supernatant,the expression of mature-CTSB,NLRP3,ASC and caspase-1,CD32 and iNOS mRNA and the positive rate of CD86 were down-regulated in group B.The expression of pro-CTSB,Arg-1 and CD206 mRNA and the positive rate of CD206 were increased(P<0.01).Conclusion:Inhibition of CTSB/NLRP3 pathway can reduce the inflammatory response,reduce the LPS-induced polarization of RAW264.7 cells to M1 macrophages,and pro-mote their polarization to M2 macrophages.
5.Dynamic patterns of pulmonary vascular endothelial subpopula-tion changes in bleomycin-induced pulmonary fibrosis mouse model
Liujinhong HAN ; Junjie DU ; Huiying LIU ; Lixin XIE
Chinese Journal of Pharmacology and Toxicology 2025;39(5):352-360
OBJECTIVE To quantify pulmonary vascular endothelial subpopulations during bleomycin-induced pulmonary fibrosis in mice.METHODS Sixty male C57BL/6 mice were randomly divided into five groups(n=12 per group)corresponding to distinct observation timepoints:0,1,2,3,and 4 weeks.A model was established via intratracheal instillation of bleomycin(3 mg·kg-1).Lung tissues were harvested at 0,1,2,3 and 4 weeks post-bleomycin induction.Pathological staining was performed to assess lung histoarchitecture and collagen fiber deposition.Single-cell suspensions were analyzed by flow cytometry to quantify temporal changes in pulmonary vascular endothelial subpopulations,including pulmonary macrovascular endothelial cells,general capillaries,and aerocyte capillaries.Immunofluo-rescence staining was performed to validate the expressions of endothelial markers(CD31,APLN,APLNR,CD93).Single-cell transcriptomic data from the Tabula Muris database was analyzed to evalu-ate gene expression profiles of vascular endothelial subpopulations.RESULTS Pathological staining revealed progressive destruction of lung histoarchitecture and collagen deposition during bleomycin-induced pulmonary fibrosis.Flow cytometry demonstrated three-phase dynamics in vascular endothelial cells(CD45-CD31+CD90.2-):a significant decrease during the acute inflammatory phase,stabilization in the fibrotic phase,and partial recovery during the resolution phase.The proportion of von Willebrand factor-positive(VWF+)vascular endothelial cells significantly decreased during the resolution phase,whereas VWF-vascular endothelial cells increased.Single-cell transcriptomics identified Cd93 asa specific gene for general capillary endothelial cells,with a negative correlation with"aerocyte"genes enriched in gas-exchange alveolar capillary endothelial cells.Immunofluorescence confirmed CD93 localization to general capillary endothelial cells.A flow sorting strategy based on CD45-CD31+CD90.2-VWF-CD93-effectively enriched alveolar capillary endothelial cells.This subpopulation trended upward in pulmonary vascular endothelial composition during bleomycin induction.CONCLUSION During bleo-mycin-induced pulmonary fibrosis in mice,pulmonary vascular endothelial subpopulations exhibit dynamic compositional heterogeneity across fibrotic injury and repair phases.
6.Role of PAD4-mediated development of NETs in lung ischemia-reperfusion injury in mice
Jiahao LIU ; Shuangni GUO ; Jiahua ZHOU ; Xueting WANG ; Fuguo MA ; Wei HAN ; Lixin SUN
Chinese Journal of Anesthesiology 2025;45(11):1445-1450
Objective:To evaluate the role of peptidylarginine deiminase 4 (PAD4)-mediated development of neutrophil extracellular traps (NETs) in lung ischemia-reperfusion injury (LIRI) in mice.Methods:Ninety-six clean-grade healthy male C57BL/6 mice, aged 6-8 weeks, weighing 20-25 g, were divided into 4 groups ( n=24 each) using a table of random numbers: sham operation group (group S), sham operation + PAD4 specific inhibitor GSK484 group (group S+ G), lung ischemia-reperfusion group (group L), and lung ischemia-reperfusion + GSK484 group (group L+ G). After anesthesia and mechanical ventilation, mice were subjected to left hilum occlusion for 1 h followed by 2 h of reperfusion to establish the LIRI model in L and L+ G groups. Mice underwent thoracotomy for 3 h without left hilum occlusion in S and S+ G groups. In S+ G and L+ G groups, GSK484 4 mg/kg was intraperitoneally injected once a day for 3 days before developing the model. At the end of reperfusion, blood samples were collected from the abdominal aorta for blood gas analysis to record arterial partial pressure of oxygen (PaO 2). Mice were then sacrificed to collect bronchoalveolar lavage fluid (BALF) and to obtain lung tissues. The concentrations of interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α) and myeloperoxidase (MPO) in BALF were measured using enzyme-linked immunosorbent assay. The wet/dry lung weight (W/D) ratio was calculated. The lung tissues were obtained for microscopic examination of pathological changes (with a light microscope) which were scored after hematoxylin-eosin staining and for determination of the contents of superoxide dismutase (SOD) and malondialdehyde (MDA) (by colorimetric assay) and expression of PAD4, neutrophil elastase (NE), high-mobility group box 1 (HMGB1), and citrullinated histone 3 (Cit-H3) (by Western blot). Results:Compared with group S, lung injury scores and W/D ratios were significantly increased, PaO 2 was decreased, the concentrations of IL-1β, IL-6, TNF-α and MPO in BALF were increased, the content of SOD was decreased, the content of MDA was increased, and the expression of PAD4, NE, HMGB1 and Cit-H3 was up-regulated in L and L+ G groups ( P<0.05), and no significant changes were observed in the aforementioned parameters in group S+ G ( P>0.05). Compared with group L, lung injury scores and W/D ratios were significantly decreased, PaO 2 was increased, concentrations of IL-1β, IL-6, TNF-α, and MPO in BALF were decreased, the content of SOD was increased, the content of MDA was decreased, and the expression of PAD4, NE, HMGB1 and Cit-H3 was down-regulated in group L+ G ( P<0.05). Conclusions:Up-regulated PAD4 expression can promote the development of NETs and aggravate oxidative stress and inflammatory responses in lung tissues, thereby participating in LIRI in mice.
7.Dynamic patterns of pulmonary vascular endothelial subpopula-tion changes in bleomycin-induced pulmonary fibrosis mouse model
Liujinhong HAN ; Junjie DU ; Huiying LIU ; Lixin XIE
Chinese Journal of Pharmacology and Toxicology 2025;39(5):352-360
OBJECTIVE To quantify pulmonary vascular endothelial subpopulations during bleomycin-induced pulmonary fibrosis in mice.METHODS Sixty male C57BL/6 mice were randomly divided into five groups(n=12 per group)corresponding to distinct observation timepoints:0,1,2,3,and 4 weeks.A model was established via intratracheal instillation of bleomycin(3 mg·kg-1).Lung tissues were harvested at 0,1,2,3 and 4 weeks post-bleomycin induction.Pathological staining was performed to assess lung histoarchitecture and collagen fiber deposition.Single-cell suspensions were analyzed by flow cytometry to quantify temporal changes in pulmonary vascular endothelial subpopulations,including pulmonary macrovascular endothelial cells,general capillaries,and aerocyte capillaries.Immunofluo-rescence staining was performed to validate the expressions of endothelial markers(CD31,APLN,APLNR,CD93).Single-cell transcriptomic data from the Tabula Muris database was analyzed to evalu-ate gene expression profiles of vascular endothelial subpopulations.RESULTS Pathological staining revealed progressive destruction of lung histoarchitecture and collagen deposition during bleomycin-induced pulmonary fibrosis.Flow cytometry demonstrated three-phase dynamics in vascular endothelial cells(CD45-CD31+CD90.2-):a significant decrease during the acute inflammatory phase,stabilization in the fibrotic phase,and partial recovery during the resolution phase.The proportion of von Willebrand factor-positive(VWF+)vascular endothelial cells significantly decreased during the resolution phase,whereas VWF-vascular endothelial cells increased.Single-cell transcriptomics identified Cd93 asa specific gene for general capillary endothelial cells,with a negative correlation with"aerocyte"genes enriched in gas-exchange alveolar capillary endothelial cells.Immunofluorescence confirmed CD93 localization to general capillary endothelial cells.A flow sorting strategy based on CD45-CD31+CD90.2-VWF-CD93-effectively enriched alveolar capillary endothelial cells.This subpopulation trended upward in pulmonary vascular endothelial composition during bleomycin induction.CONCLUSION During bleo-mycin-induced pulmonary fibrosis in mice,pulmonary vascular endothelial subpopulations exhibit dynamic compositional heterogeneity across fibrotic injury and repair phases.
8.Role of PAD4-mediated development of NETs in lung ischemia-reperfusion injury in mice
Jiahao LIU ; Shuangni GUO ; Jiahua ZHOU ; Xueting WANG ; Fuguo MA ; Wei HAN ; Lixin SUN
Chinese Journal of Anesthesiology 2025;45(11):1445-1450
Objective:To evaluate the role of peptidylarginine deiminase 4 (PAD4)-mediated development of neutrophil extracellular traps (NETs) in lung ischemia-reperfusion injury (LIRI) in mice.Methods:Ninety-six clean-grade healthy male C57BL/6 mice, aged 6-8 weeks, weighing 20-25 g, were divided into 4 groups ( n=24 each) using a table of random numbers: sham operation group (group S), sham operation + PAD4 specific inhibitor GSK484 group (group S+ G), lung ischemia-reperfusion group (group L), and lung ischemia-reperfusion + GSK484 group (group L+ G). After anesthesia and mechanical ventilation, mice were subjected to left hilum occlusion for 1 h followed by 2 h of reperfusion to establish the LIRI model in L and L+ G groups. Mice underwent thoracotomy for 3 h without left hilum occlusion in S and S+ G groups. In S+ G and L+ G groups, GSK484 4 mg/kg was intraperitoneally injected once a day for 3 days before developing the model. At the end of reperfusion, blood samples were collected from the abdominal aorta for blood gas analysis to record arterial partial pressure of oxygen (PaO 2). Mice were then sacrificed to collect bronchoalveolar lavage fluid (BALF) and to obtain lung tissues. The concentrations of interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α) and myeloperoxidase (MPO) in BALF were measured using enzyme-linked immunosorbent assay. The wet/dry lung weight (W/D) ratio was calculated. The lung tissues were obtained for microscopic examination of pathological changes (with a light microscope) which were scored after hematoxylin-eosin staining and for determination of the contents of superoxide dismutase (SOD) and malondialdehyde (MDA) (by colorimetric assay) and expression of PAD4, neutrophil elastase (NE), high-mobility group box 1 (HMGB1), and citrullinated histone 3 (Cit-H3) (by Western blot). Results:Compared with group S, lung injury scores and W/D ratios were significantly increased, PaO 2 was decreased, the concentrations of IL-1β, IL-6, TNF-α and MPO in BALF were increased, the content of SOD was decreased, the content of MDA was increased, and the expression of PAD4, NE, HMGB1 and Cit-H3 was up-regulated in L and L+ G groups ( P<0.05), and no significant changes were observed in the aforementioned parameters in group S+ G ( P>0.05). Compared with group L, lung injury scores and W/D ratios were significantly decreased, PaO 2 was increased, concentrations of IL-1β, IL-6, TNF-α, and MPO in BALF were decreased, the content of SOD was increased, the content of MDA was decreased, and the expression of PAD4, NE, HMGB1 and Cit-H3 was down-regulated in group L+ G ( P<0.05). Conclusions:Up-regulated PAD4 expression can promote the development of NETs and aggravate oxidative stress and inflammatory responses in lung tissues, thereby participating in LIRI in mice.
9.Effect of cathepsin B/NLRP3 pathway on M1/M2 polarization of macrophages induced by LPS
Yibo WANG ; Yuting DAI ; Jiangxiao CAI ; Zhonglin LI ; Weiwei QIN ; Lixin SUN ; Wei HAN
Chinese Journal of Immunology 2025;41(1):63-68
Objective:To evaluate the effect of cathepsin B(CTSB)/NOD-like receptor pyrin domain containing 3(NLRP3)pathway on the polarization of macrophages induced by LPS.Methods:The well-growing RAW264.7 mouse mononuclear macrophage lines were cultured in vitro and divided into 3 groups(n=6)according to the random number table method:control group(C group),LPS group(L group)and LPS+CA074-me(CTSB inhibitors)group(B group).C group was cultured normally for 24 h,L group was cultured with LPS concentration of 1 μg/ml medium for 24 h.B group was pretreated with CTSB inhibitor CA074-me 30 μmol/L for 1 h before LPS induction,and co-cultured with LPS concentration of 1 μg/ml medium for 24 h.After 24 hours,the morphological changes of the cells were observed by microscope,the concentrations of IL-1β and IL-18 in the supernatant were determined by ELISA.The ex-pressions of cathepsin B precursor(pro-CTSB),mature cathepsin B(mature-CTSB),NLRP3,apoptosis-related speck protein(ASC)and apoptosis-related speck protein-1(caspase-1)were detected by Western blot.The mRNA expression levels of CD32,inducible ni-tric oxide synthase(iNOS),arginase 1(Arg-1)and CD206 were detected by qRT-PCR.The positive expression rates of M1 macro-phage surface marker CD86 and M2 macrophage surface marker CD206 were detected by flow cytometry.Results:Compared with group C,the morphology of cells in groups L and B became larger and pseudopodia appeared.The concentrations of IL-1β and IL-18 in cell supernatant were increased,the expressions of pro-CTSB,mature-CTSB,NLRP3,ASC and caspase-1 were increased,and the expressions of CD32,iNOS mRNA were up-regulated and the positive rates of CD86 and CD206 were increased(P<0.01).Arg-1 and CD206 mRNA in group B were up-regulated(P<0.01).Compared with group L,the pseudopodia of group B were reduced,and the morphology was closer to group C.The concentration of IL-1β and IL-18 in the supernatant,the expression of mature-CTSB,NLRP3,ASC and caspase-1,CD32 and iNOS mRNA and the positive rate of CD86 were down-regulated in group B.The expression of pro-CTSB,Arg-1 and CD206 mRNA and the positive rate of CD206 were increased(P<0.01).Conclusion:Inhibition of CTSB/NLRP3 pathway can reduce the inflammatory response,reduce the LPS-induced polarization of RAW264.7 cells to M1 macrophages,and pro-mote their polarization to M2 macrophages.
10.Physiological characteristics of Bacillus thuringiensis subspecies israelensis with double mutations of cwlE and sigK and its activity against larvae of Culex pipiens pallens
Lixin HUANG ; Guangjie HAN ; Chuanming LI ; Manman LIN ; Nan ZHANG ; Jian XU
Chinese Journal of Schistosomiasis Control 2024;36(6):606-613
Objective To investigate the physiological characteristics of Bacillus thuringiensis subspecies israelensis (Bti) with double mutations of cwlE and sigK genes and to assess the activity of Bti against larvae of Culex pipiens pallens under different external factors, so as to provide the theoretical evidence for the use of engineered bacteria of Bti for effective mosquito control. Methods B. thuringiensis wild-type strain Bt-59 and Bt-59 strain with cwlE mutation [Bt-59 (ΔcwlE)] were cultured in nutrient broth media for 24 hours, and Bt-59 strains with sigK mutation [Bt-59 (ΔsigK)] and double mutations of cwlE and sigK [Bt-59 (ΔcwlE-sigK)] were cultured in nutrient broth media for 48 hours. Then, 5 μL of culture media were transferred to glass sides, and cell morphology and mother cell lysis were observed under an optical microscope. The optical densities of Bti strain culture media were measured at different time points of culture, and the growth curves of Bt-59, Bt-59 (ΔcwlE), Bt-59 (ΔsigK), and Bt-59 (ΔcwlE-sigK) strains were plotted. The differences in carbon source metabolism of four Bti strains were analyzed using the Biolog microplate culture method, and the metabolic activity of these strains was estimated with average well color development (AWCD). The fermentation media of these four Bti strains were diluted into final concentrations of 2.000, 1.000, 0.500, 0.250, and 0.125 μL/L, and the median lethal concentrations (LC50 values) of these four strains against the third instar larvae of Cx. pipiens pallens were determined. In addition, the fermentation media of Bti strains were processed as follows: pH adjusted to 5, 7 and 9; treated at 30, 40 ℃ and 50 ℃ for 12 hours; and exposed to irradiation with ultraviolet lights for 0 hour and 6 hours. Then, 20 third instar larvae of Cx. pipiens pallens were exposed to the above processed fermentation media at a final concentration of 1 μL/L in 200 mL of water at 26 ℃ for 24 hours, and the mosquito mortality was estimated to evaluate the effects of pH, temperature and ultraviolet irradiation on the larvicidal activity of four Bti strains. Results The growth curves of the Bt-59 strain and its mutants shared a similar changing trend, and both experienced a stable phase 6 hours post-culture. Both spores and crystal proteins were found in Bt-59 and Bt-59 (ΔcwlE) cells, and only crystal proteins were found in Bt-59 (ΔsigK) and Bt-59 (ΔcwlE-sigK) cells. No lysis was found in the cell wall of the Bt-59 (ΔcwlE-sigK) strain, and the crystal protein was embedded in the mother cell. Biolog microplate culture assay showed that the AWCD values of four Bti strains showed a similar changing trend over time, and 33 carbon sources were found to be metabolized by all of the four strains, including dextrin, D-maltose and D-trehalose. The LC50 values of the fermentation media of Bt-59, Bt-59 (ΔcwlE), Bt-59 (ΔsigK), and Bt-59 (ΔcwlE-sigK) strains were 0.60, 0.51, 0.70 μL/L and 0.72 μL/L against Cx. pipiens pallens, respectively. The adjusted mortality of larval Cx. pipiens pallens reduced by 76.60%, 76.00%, 66.67%, and 0 following exposure to the fermentation media of Bt-59, Bt-59 (ΔcwlE), Bt-59 (ΔsigK), and Bt-59 (ΔcwlE-sigK) strains at a pH of 5 relative to at a pH of 7, and the adjusted mortality reduced by 49.02%, 51.06%, 36.36%, and 4.44% following 6-hour exposure to ultraviolet irradiation relative to 0-hour exposure, while the adjusted mortality was 68.33% to 83.33% following treatment with the fermentation media of four Bti strains at different temperatures. Conclusions Bt-59 (ΔcwlE-sigK) strains do not generate spores, and the absence of cwlE and sigK does not affect the growth, carbon source metabolism, and larvicidal activity of Bti strains against larval Cx. pipiens pallens. Cell wall embedding of Bt-59 (ΔcwlE-sigK) strains may protect larvicidal crystal proteins of Bti strains from external environmental factors, including ultraviolet irradiation, and pH alteration.

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