Polymorphism of flagellin A gene in Helicobacter pylori

AIM:To study the polymorphism of flagellin A genotype and Its significance in Helicobecter pylori(H.pylori). METHODS:As the template,genome DNA was purified from six clinical isolates of H.pylori from outpatients,and the corresponding flagellion A fragments were amplified by polymerase chain reaction.All these products were sequenced.These sequences were compared with each other,and analyzed by software of FASTA program. RESULTS:Spaciflc PCR products were amplified from all of these H.pylorl isolates and no length divergence was found among them.Compared with each other,the highest ungappad identity is 99.10%,while the lowest is 94.65%. Using FASTA program,the alignments between query and llbary sequences derived from different H.pylori strains were higher than 90%. CONCLUSION:The nucleotide sequence of flagellin A in H. pylori is highly conservative with Incident divergence.This Information may be useful for gene diagnosis and further study on flagellar antigen phenotype.

Gene cloning and prokaryotic expression of recombinant flagellin A from Vibrio parahaemolyticus

The Gram-negative Vibrio parahaemolyticus is a common pathogen in humans and marine animals. Bacteria flagellins play an important role during infection and induction of the host immune response. Thus, flagellin proteins are an ideal target for vaccines. We amplified the complete flagellin subunit gene （tTaA） from V. parahaemolyticus ATCC 17802. We then cloned and expressed the gene into Escherichia coli BL21 （DE3） cells. The gene coded for a protein that was 62.78 kDa. We purified and characterized the protein using Ni-NTA affinity chromatography and Anti-His antibody Western blotting, respectively. Our results provide a basis for further studies into the utility of the FlaA protein as a vaccine candidate against infection by Vibrio parahaemolyticus. In addition, the purified FlaA protein can he used for further functional and structural studies.

Helicobacter pylori specific immune response induced by conservative flagellin linear B-cell epitope

AIM:To testify the immunogenicity of a conservative B-cell linear epitope of Helicobacter pylori ( H pylori) flagellin A. METHODS: Different programs were used to analyze the secondary structure, molecular hydropathy, and surface accessibility of Hpyloriflagellin A. Linear B-cell epitopes were estimated based on the structural and physiochemical information. Analysis of residue divergence was proposed to screen a conservative linear epitope. The 29-peptide (Pep29mer) synthesized by chemical method, including the predicted conservative B-cell epitope and a known K^2d compatible T-cell epitope, was used to immunize mice, and then H pylori-specific antibodies were detected by ELISA. RESULTS: Based on the analyses of divergent amino acid residues, structural and physiochemical characteristics, it was strongly suggested that the short fragment NDSDGR was the core of a conservative linear epitope in flagellin A. Animals immunized by Pep29mer acquired efficient immune response. In detail, serum Hpylori-specific IgA and IgGl increased significantly in immunized group, while IgG2a only had an insignificant change. Hpylori-specific IgA in gastrointestinal flushing fluid also increased significantly. CONCLUSION: The conservative short fragment NDSDGR is the core of a linear B-cell epitope of flagellin A.

转燕麦噬酸菌蛋白激发子基因flagellin的链霉工程菌株构建及鉴定

利迪链霉菌A01可以产生大量的抗生素——纳他霉素,其通过结合病原真菌细胞膜上的甾醇分子而起到抑制病原菌生长的作用。燕麦噬酸菌的鞭毛蛋白组分FLAGELLIN可以诱导植物抗性,激发活性氧及水杨酸防御反应途径。本研究将燕麦噬酸菌蛋白激发子基因flagellin克隆,接合转移入利迪链霉菌A01中,使工程菌增加诱导植物抗性的功能。PCR验证表明:成功获得了含flagellin基因的阳性工程菌株,证明通过链霉工程菌构建可实现抗生与诱抗的协同作用,预计会提高防治植物病害的效果。

AEG-1肺归巢域与Flagellin融合基因的杆状病毒制备及鉴定

目的通过重叠PCR方法获得AEG-1C-Flic融合基因,采用Bac-To-Bac杆状病毒表达系统获得重组AEG-1C-Flic杆状病毒,为后续AEG-1C-Flic病毒样颗粒疫苗的制备奠定基础。方法从鼠伤寒沙门菌的基因组中PCR扩增细菌鞭毛蛋白Flagellin,采用重叠PCR的方法将AEG1肺归巢域段基因与Flagellin融合,并添加猴免疫缺陷病毒(simian immunodeficiency virus,SIV)包膜蛋白gp41信号肽与跨膜区,构建AEG-1C-Flic pFastBacTM重组表达载体,转座大肠杆菌E.coliDH10Bac感受态细胞后获得重组杆粒,重组杆粒转染昆虫细胞Tn5,获得AEG-1CFlic重组杆状病毒,并采用Western Blot方法对该病毒进行鉴定。结果构建的AEG-1C-Flic杆状病毒表达载体经双酶切及测序正确,通过转化E.coli DH10Bac感受态细胞获得重组Bacmid,经PCR鉴定大小正确,Western Blot结果显示Bacmid转染Tn5细胞后成功获得重组杆状病毒rBv AEG-1C-Flic。结论成功构建的AEG-1C-Flic杆状病毒可用于新型AEG1-病毒样颗粒疫苗的制备。

激动剂Flagellin对中性粒细胞凋亡和Bax蛋白表达的影响

目的:研究TLR激动剂flagellin影响中性粒细胞凋亡及凋亡调控蛋白Bax的表达。方法:分离培养正常人的外周血中性粒细胞,分为实验组(flagellin刺激组)、凋亡抑制组(LPS刺激组)和自然凋亡组。用流式细胞术检测不同组中性粒细胞的凋亡发生率,通过Western blotting技术检测各组中性粒细胞Bax蛋白的表达。结果:flagellin使中性粒细胞自发性凋亡的发生率增高,与凋亡抑制组和自然凋亡组比较差异有统计学意义(P<0.01);接受flagellin刺激的中性粒细胞表达Bax蛋白高于凋亡抑制组与自然凋亡组(P<0.01)。结论:在TLR激动剂诱发的中性粒细胞生存效应中,flagellin可能通过上调中性粒细胞胞内Bax蛋白的表达来缩短中性粒细胞的生命期限。

Calcium phosphate nanoparticles show an effective activation of the innate immune response in vitro and in vivo after functionalization with flagellin

For subunit vaccines,adjuvants play a key role in shaping the magnitude,persistence and form of targeted antigen-specific immune response.Flagellin is a potent immune activator by bridging innate inflammatory responses and adaptive immunity and an adjuvant candidate for clinical application.Calcium phosphate nanoparticles are efficient carriers for different biomolecules like DNA,RNA,peptides and proteins.Flagellin-functionalized calcium phosphate nanoparticles were prepared and their immunostimulatory effect on the innate immune system,i.e.the cytokine production,was studied.They induced the production of the proinflammatory cytokines IL-8 （Caco-2 cells） and IL-1β（bone marrow-derived macrophages; BMDM） in vitro and IL-6 in vivo after intraperitoneal injection in mice.The immunostimulation was more pronounced than with free flagellin.

Relationship between genotype and phenotype of flagellin C in Salmonella

AIM: To discover the relationship between the genotype and antigen serotype of flagellin C among Salmonella strains. METHODS: Fragment of Salmonella flagellin C in plasmid pLS408 was cloned, sequenced and compared with the corresponding sequence in other strains. Salmonella strains including two typhi strains, one paratyphoid strain, one enteritidis and one typhimurium strain were isolated from outpatients. Genome DNA was purified respectively from these clinical isolates, then the corresponding flagellin C fragment was amplified by polymerase chain reaction,and the amplification products were analyzed by agarose gel electrophoresis. RESULTS: The cloned fragment includes 582 nucleotides encoding the variable region and partial conservative region of Salmonella flagellin C in plasmid pLS408. With comparison to the corresponding sequences reported previously, there is only a little difference from other strains with the same flagellar serotype in both nucleotide and amino acid level. Specific PCR products were amplified in Salmonella strains with flagellar serotype H-1-d including S. muenchen, typhi and typhimurium, but not in S. paratyphoid C or S. enteritidis strains. CONCLUSION: In this experiment, the specificity of nucleotide sequence could be found in flagellin C central variable regions as it exists in flagellar serotypes in Salmonella. It may be helpful to developing a rapid, sensitive, accurate and PCR-based method to detect Salmonella strains with serotype H-1-d.

Molecular cloning and functional identification of an apple flagellin receptor MdFLS2 gene

The leucine-rich repeat receptor kinase flagellin-sensing 2 gene(MdFLS2; Gene ID: MDP0000254112) was cloned from Royal Gala apple(Malus×domestica Borkh.). This gene contained a complete open reading frame of 3 474 bp that encoded 1 158 amino acids. The phylogenetic tree indicated that Prunus persica FLS2 exhibited the highest sequence similarity to MdFLS2. The PlantCare database suggests that the promoter sequence of MdFLS2 contains several typical cis-acting elements, including ethylene-, gibberellin-, salicylic acid-, and drought-responsive elements. Quantitative real-time PCR analysis showed that MdFLS2 was widely expressed in the different tissues of the apple and most highly expressed in the leaves. Furthermore, MdFLS2 was significantly induced by the flagellin elicitor peptide flg22. Treatment of the apple seedling leaves with flg22 resulted in an increase in leaf callose levels with increased treatment duration. An increase in the production of Oalong with the expression of disease-related genes was also observed. An oxidative burst was detected in the treated seedlings, but not in the control seedlings, indicating that flg22 had stimulated the expression of the MdFLS2 gene and its downstream target genes. Furthermore, the ectopic expression of MdFLS2 complemented the function of the Arabidopsis fls2 mutant and conferred enhanced flg22 tolerance to the transgenic Arabidopsis, suggesting that MdFLS2 acts as a positive regulator in the response to pathogens in apple.

Effect of Acacetin on flagellin induced NLRC4 inflammasome activation in mouse bone marrow-derived macrophages

Objective:To investigate the effect of acacetin on flagellin induced NLRC4 inflammasome activation in mouse bone marrow-derived macrophages(BMDMs).Methods:Mouse BMDMs were divided into control group,LPS group,LPS+flagellin group and LPS+acacetin+flagellin group.All groups were added with complete medium,then primed with LPS(50 ng/mL)for 3 hrs except the control group,whereafter,LPS+flagellin group was treated with flagellin(10μmol/L)for 0.5 hr and LPS+acacetin+flagellin group was treated with acacetin(10μmol/L)for 0.5 hr following by flagellin(10μmol/L)for 0.5 hr.Pro-caspase-1,pro-IL-1βin cell lysate and caspase-1,IL-1βin supernatant were detected by Western blot(WB).IL-1β,IL-18 and TNF-αin supernatant were measured by enzyme-linked immunosorbent assay(ELISA).And the activity of LDH in supernatant was assessed by LDH test kit.Results:Compared with the control group,in LPS+flagellin group,the expression of caspase-1,IL-1βprotein in supernatant were significantly increased(all P-values<0.05),but the differences of the expression of pro-caspase-1 and pro-IL-1βprotein in cell lysate were not significant.Compared with LPS+flagellin group,in LPS+acacetin+flagellin group,the expression of caspase-1,IL-1βprotein in supernatant were significantly reduced(all P-values<0.05),while the differences of the expression of pro-caspase-1 and pro-IL-1βprotein in cell lysate were not significant.ELISA showed that compared with the control group,the levels of IL-1β,IL-18,and TNF-αand the activity of LDH in supernatant of LPS+flagellin group were significantly increased(all P-values<0.05).Compared with LPS+flagellin group,in LPS+Acacetin+flagellin group,the level of IL-1βin supernatant was significantly decreased(P<0.05),meanwhile,the decreases of the levels IL-18,TNF-αand the activity of LDH were not significant.Conclusions:We found that Acacetin can effectively inhibit flagellin induced NLRC4 inflammasome activation and reduce cell damage in mouse BMDMs.

TLR5 involvement in attenuated IL-8 production in nuclear decorin silenced oral mucosal dysplastic keratinocytes and squamous cell carcinoma

Head and neck cancer is one of the most prevalent cancers in the world. Roughly half of these malignancies originate from oral mucosa and constitute Oral squamous cell carcinomas. Despite many advances in diagnostic and therapeutic regimens, five year survival rate remains at roughly 50 %, indicating the need for in depth understanding of the oral squamous cell carcinoma immunobiology. We have previously shown that in human dysplastic oral keratinocytes (DOK) and malignant squamous cells carcinoma (SCC-25), multifunctional proteoglycan decorin is aberrantly expressed and localized in the nucleus bound to nuclear EGFR. In vitro nuclear decorin knockdown significantly reduced IL-8 and IL8-dependent migration, invasion and angiogenesis in these cells. Since toll-like receptor (TLR) signalling leads to IL-8 production we examined here if these receptors play a role in decorin silencing mediated reduction in IL-8 levels. We have used immunological and molecular techniques to study toll-like receptors involvement in attenuated IL-8 production in nuclear decorin silenced (stable knockdown) oral mucosal dysplastic keratinocytes and squamous carcinoma cells. We show that nuclear decorin silenced DOK and SCC-25 cells show marked diminution of TLR5 mRNA and protein expression compared with respective controls that translated into loss of function in response to appropriate TLR ligand. In these mucosal oral epithelia, decorin stable knockdown significantly down-regulated IL-8 production following activation with TLR5 ligand flagellin. These data suggest that decorin silencing interferes with IL-8 production, in part, by altering TLR5 expression and signaling in dysplastic and malignant oral epithelia. This study highlights the significance of TLR5 expression and signaling in mucosal cancers.

蒜芥茄SsFLS2基因的克隆及其表达分析

【目的】克隆云南野生蒜芥茄(Solanum sisymbriifolium Lam.)中的FLS2基因,并对其编码蛋白的理化性质、亚细胞定位、系统进化以及表达情况予以分析,初步探究野茄FLS2基因在黄萎病胁迫下的生物学功能。【方法】基于前期所测转录组数据(蒜芥茄接种黄萎病病原菌),克隆获取蒜芥茄FLS2基因,命名为SsFLS2;利用生物信息学分析软件对SsFLS2基因的理化性质进行分析,并通过实时荧光定量PCR(Real-time fluorescence quantitative PCR,RT-qPCR)检测其在蒜芥茄根、茎、叶的表达以及在接种黄萎病病原菌后不同时间的表达情况。【结果】蒜芥茄SsFLS2基因全长3655 bp,具有完整的ORF框,编码1126个氨基酸。其编码蛋白的分子式为C_(5596)H_(8814)N_(1494)O_(1627)S_(4),理论分子量为124.34 kD,理论等电点(pI)为7.33,总平均亲水性系数为0.081。该蛋白二级结构主要由42.81%的无规则卷曲、40.23%的α-螺旋、13.23%的延伸链以及3.73%的β-折叠组成,且存在跨膜结构,定位于细胞膜上,其中可被磷酸化且超过阈值线的位点,共计151个。SsFLS2蛋白的氨基酸序列与马铃薯(Solanum tuberosum)同源蛋白(XP 006358149.2)的关系最近。RT-qPCR检测发现,在蒜芥茄根、茎、叶中均有SsFLS2基因的表达,且根、叶中的相对表达量极显著高于茎部;接种黄萎病病原菌后72 h内,处理组和对照组均在24 h时,SsFLS2基因的相对表达量大幅度增加且极显著高于其他时间点。【结论】本研究成功克隆蒜芥茄的SsFLS2基因,并对其编码蛋白的理化性质及基因表达情况等进行分析。结果表明,SsFLS2是蒜芥茄响应黄萎病胁迫的重要基因,结果可为进一步研究该基因在蒜芥茄黄萎病抗性中的功能奠定基础。

Over-activation of TLR5 signaling by high-dose flagellin induces liver injury in mice

Flagellin is a potent activator of a broad range of cell types that are involved in innate and adaptive immunity. Therefore, it is a good adjuvant candidate for vaccines, and it might function as a biological protectant against both major acute radiation syndrome during cancer radiotherapy and a mitigator of radiation emergencies. However, accumulating evidence has implicated flagellin in the occurrence of some inflammatory diseases, such as acute lung inflammation, cardiovascular collapse and inflammatory bowel disease. The aim of this study was to elucidate whether only flagellin-TLR5 signaling activation plays a role in the pathophysiology of liver or whether some other flagellin activity also contributes to liver injury either via bacterial infections or during clinical applications. Recombinant flagellin proteins with or without TLR5-stimulating activity were used to evaluate the role of flagellin-TLR5 signaling in liver injury in wild-type and TLR5 KO mice. Gross lesions and large areas of hepatocellular necrosis were observed in liver tissue 12 h after the intraperitoneal administration of 100 or 200 pg flagellin （FliC） in a dose-and time-dependent manner in wild-type mice, but not in TLR5 KO mice. Deletion of the N-terminal or TLR5 binding domain of flagellin inhibited flagellin-induced inflammatory responses and the subsequent acute liver function abnormality and damage. These data confirmed that flagellin is an essential determinant of liver injury and demonstrated that the over-activation of TLR5 signaling by high-dose flagellin caused acute inflammatory responses, neutrophil accumulation and oxidative stress in the liver, which contributes to the progression and severity of flagellin-induced liver injury.

Salmonella flagella confer anti-tumor immunological effect via activating Flagellin/TLR5 signalling within tumor microenvironment

Salmonella:mediated cancer therapy has achieved remarkable anti-tumor effects in experimental animal models,but the detailed mechanism remains unsolved.In this report,the active involvement of the host immune response in this process was confirmed by comparing the tumor-suppressive effects of Salmonella in immunocompetent and immunodeficient mice bearing melanoma allografts.Since flagella are key inducers of the host immune response during bacterial infection,flagella were genetically disrupted to analyse their involvement in Salmonella-mediated cancer therapy.The results showed that flagellum-deficient strains failed to induce significant anti-tumor effects,even when more bacteria were administered to offset the difference in invasion efficiency.Flagella mainly activate immune cells via Flagellin/Toll-like receptor 5(TLR5)signalling pathway.Indeed,we showed that exogenous activation of TLR5 signalling by recombinant Flagellin and exogenous expression of TLR5 both enhanced the therapeutic efficacy of flagellum-deficient Salmonella against melanoma.Our study highlighted the therapeutic value of the interaction between Salmonella and the host immune response through Flagellin/TLR5 signalling pathway during Salmonella-mediated cancer therapy,thereby suggesting the potential application of TLR5 agonists in the cancer immune therapy.

Rice OsFLS2-Mediated Perception of Bacterial Flagellins Is Evaded by Xanthomonas oryzae pvs. oryzae and oryzicola

Bacterial flagellins are often recognized by the receptor kinase FLAGELLIN SENSITIVE2 （FLS2） and activate MAMP-triggered immunity in dicotyledonous plants. However, the capacity of monocotyledonous rice to recognize flagellins of key rice pathogens and its biological relevance remain poorly understood. We demonstrate that ectopically expressed OsFLS2 in Arabidopsis senses the eliciting fig22 peptide and in vitro purified Acidovorax avenae （Aa） flagellin in an expression level-dependent manner, but does not recognize purified flagellins or derivative fig22x~ peptides ofXanthomonas oryzae pvs. oryzae （Xoo） and or- yzicola （Xoc）. Consistently, the fig22 peptide and purified Aa flageUin, but not Xoo/Xoc flagellins, induce various immune responses such as defense gene induction and MAPK activation in rice. Perception of flagellin by rice does induce strong resistance to Xoo infection, as shown after pre-treatment of rice leaves with Aa flagellin. OsFLS2 was found to differ from AtFLS2 in its perception specificities or sensitivities to different fig22 sequences. In addition, post-translational modification of Xoc flagellin was altered by dele- tion of glycosyltransferase-encoding rbfC, but this had little effect on Xoc motility and rpfC mutation did not detectably reduce Xoc virulence on rice. Deletion of flagellin-encoding fliC from Xoo/Xoc blocked swim- ming motility but also did not significantly alter Xoo/Xoc virulence. These results suggest that Xoo/Xoc carry flg22-region amino acid changes that allow motility while evading the ancient flagellin detection sys- tem in rice, which retains recognition capacity for other bacterial pathogens.

Activation of NLRC4 downregulates TLR5-mediated antibody immune responses against flagellin

Bacterial flagellin is a unique pathogen-associated molecular pattern （PAMP）, which can be recognized by surface localized Toll-like receptor 5 （TLR5） and the cytosolic NOD-like receptor （NLR） protein 4 （NLRC4） receptors. Activation of the TLR5 and/or NLRC4 signaling pathways by flagellin and the resulting immune responses play important roles in anti-bacterial immunity. However, it remains unclear how the dual activities of flagellin that activate the TLR5 and/or NLRC4 signaling pathways orchestrate the immune responses. In this study, we assessed the effects of flagellin and its mutants lacking the ability to activate TLR5 and NLRC4 alone or in combination on the adaptive immune responses against flagellin. Flagellin that was unable to activate NLRC4 induced a significantly higher antibody response than did wild-type flagellin. The increased antibody response could be eliminated when macrophages were depleted in vivo. The activation of NLRC4 by flagellin downregulated the flagellin-induced and TLR5-mediated immune responses against flagellin.

Chimeric flagellin expressed by Salmonella typhimurium induces an ESAT-6-specific Th1-type immune response and CTL effects following intranasal immunization

The flagellin component FliC of Salmonella typhimurium is capable of activating the innate immune system via specific interactions with TLR5 and can also act as a carrier of foreign antigen to elicit antigen-specific immune responses.Thus,we constructed an attenuated Salmonella strain SL5928(fliC/esat)expressing chimeric flagellin that contained the ESAT-6 antigen coding sequence of Mycobacterium tuberculosis inserted into the highly variable region of the Salmonella flagellin coding gene fliCi.The chimeric flagellin functioned normally,as demonstrated using a flagella swarming assay and electron microscopy.To analyze the effects of chimeric flagellin,the cell-mediated immune response and cytotoxic T lymphocyte(CTL)effects specific for ESAT-6 antigen were tested after intranasal immunization of mice with flagellated Salmonella SL5928(fliC/esat).The results showed that SL5928(fliC/esat)intranasal immunization can strongly elicit an ESAT-6-specific T helper(Th)1-type immune response in mucosal lymphoid tissues,such as nasopharynx-associated lymph nodes,lung and Peyer’s patches,and a Th1/Th2 response was elicited in spleen and mesenteric lymph nodes.Furthermore,intranasal immunization of SL5928(fliC/esat)produced efficient CTL effects,as demonstrated using a 5-and 6-carboxyfluorescein diacetate succinimidyl ester(CFSE)assay.Thus,our study revealed that Salmonella flagellin acts as a carrier for foreign antigen and triggers strong Th1 and CTL responses during intranasal immunization.Chimeric flagellin is potentially an effective strategy for the development of novel vaccines against tuberculosis in humans and animals.

Salmonella enterica Flagellin Is Recognized via FLS2 and Activates PAMP-Triggered Immunity in Arabidopsis thaliana

Infections with Salmonella enterica belong to the most prominent causes of food poisoning and infected fruits and vegetables represent important vectors for salmonellosis. Recent evidence indicates that plants recognize S. enterica and raise defense responses. Nonetheless, the molecular mechanisms controlling the interaction of S. enterica with plants are still largely unclear. Here, we show that flagellin from S. enterica represents a prominent pathogenassociated molecular pattern （PAMP） in Arabidopsis thaliana, which induces PAMP-triggered immunity （PTI） via the recognition of the fig22 domain by the receptor kinase FLS2. The Arabidopsis fls2 mutant shows reduced though not abolished PTI activation, indicating that plants rely also on recognition of other S. enterica PAMPs. Interestingly, the S. enterica type III secretion system （T3SS） mutant prgH- induced stronger defense gene expression than wild-type bacteria in Arabidopsis, suggesting that T3SS effectors are involved in defense suppression. Furthermore, we observe that S. enterica strains show variation in the fig22 epitope, which results in proteins with reduced PTI-inducing activity. Altogether, these results show that S. enterica activates PTI in Arabidopsis and suggest that, in order to accomplish plant colonization, S. enterica evolved strategies to avoid or suppress PTI.

Flagellin of Pseudomonas aeruginosa induces transforming growth factor beta 1 expression in normal bronchial epithelial cells through mitogen activated protein kinase cascades

Background Acute lung infection due to Pseudomonas aeruginosa （P. Aeruginosa） is a serious problem, especially in patients with structural lung conditions or immune compromised hosts, leading to an overwhelming threat with a high risk of morbidity and mortality. As an outcome of infection, fibrosis can be linked with chronic lung diseases. But some fibrotic manifestations, such as an irreversible decrease of lung function and fibrous bands seen on chest imaging, have been found after an acute infection with P. Aeruginosa. Fibrogenesis/remodeling resulting from acute lung infection by P.aeruginosa is rarely reported. This study was designed to explore the relation between fibrogenesis/remodeling and acute infection by P. Aeruginosa in vitro. We used flagellin protein from P. Aeruginosa, a key initiator of acute P.aeruginosa lung infection, to elucidate mechanisms by which acute lung infection with P. Aeruginosa can cause fibrogenesis/remodeling.Methods We studied the effect of flagellin from P. Aeruginosa （flagellin for short） on the transforming growth factor beta 1 （TGF-β1） and interleukin-8 （IL-8） expression, and the possible involvement of the signaling pathway, tumor necrosis factor receptor-associated factor 6 （TRAF6）/mitogen activated protein kinase （MAPK） pathway. Flagellin was purified from the P. Aeruginosa standard strain, PAO1. Normal bronchial epithelial cells BEAS-2B were challenged with different concentrations of flagellin, and cell viability assessment was performed by cell counting kit-8. BEAS-2B cells were incubated with flagellin with the specific MAPK inhibitors or TRAF6 siRNA. Cell lysates and the cultured supernatant were collected. The level of TGF-β1 and IL-8 were detected by enzyme-linked immunosorbant assay （ELISA）. Western blotting was used to detect the protein levels of MAPK signal proteins p38, c-Jun NH2-terminal kinase （JNK） and extracellular regulated kinase （ERK）.Results Expression of TGF-β1 in BEAS-2B cells was elevated by flagellin vs. Control groups （（104.3±20.8） vs.（44.6±4.4） pg/ml （P 〈0.01）） and was ablated by either p38 or JNK inhibitors compared with flagellin treatment （（45.1±18.8）vs. （104.3±20.8） pg/ml and （48.1±20.8） vs. （104.3±20.8） pg/ml, respectively （P 〈0.05））. Flagellin also elevated the expression of IL-8 in BEAS-2B cells vs. The control groups （（554.9±57.7） vs. （51.4±2.2.9） pg/ml （P 〈0.01））, and p38 MAPK inhibitors weaken the expression by flagellin （（301.1 ±155.1） vs. （554.9±57.7） pg/ml （P 〈0.05））. Western blotting revealed that all three MAPK proteins, p38, JNK and ERK were activated by flagellin challenge in an early phase, respectively in 15 minutes （P 〈0.01）, 30 minutes （P 〈0.01） and 15 minutes （P 〈0.01）. TRAF6 siRNA which decreased expression of TRAF6, altered the activation of JNK, p38, and ERK following flagellin treatment, but its influence on the expression of TGF-β1 and IL-8 has no statistical significance.Conclusions Flagellin from P. Aeruginosa PAO1 induces TGF-β1 expression in normal bronchial epithelial cells,BEAS-2B, through the MAPK signal cascade in vitro. It suggests that the fibrogenesis/remodeling process may be initiated from an early stage of acute lung infection due to P. Aeruginosa.

A triple-RBD-based mucosal vaccine provides broad protectionagainst SARS-CoV-2 variants of concern

The rapid mutation and spread of SARS-CoV-2 variants urge the development of effective mucosal vaccines to provide broadspectrum protection against the initial infection and thereby curb the transmission potential.Here,we designed a chimeric tripleRBD immunogen,3Ro-NC,harboring one Delta RBD and two Omicron RBDs within a novel protein scaffold.3Ro-NC elicits potent and broad RBD-specific neutralizing immunity against SARS-CoV-2 variants of concern.Notably,intranasal immunization with 3RoNC plus the mucosal adjuvant KFD(3Ro-NC+KFDi.n)elicits coordinated mucosal IgA and higher neutralizing antibody specificity(closer antigenic distance)against the Omicron variant.In Omicron-challenged human ACE2 transgenic mice,3Ro-NC+KFDi.n immunization significantly reduces the tissue pathology in the lung and lowers the viral RNA copy numbers in both the lung(85.7-fold)and the nasal turbinate(13.6-fold).Nasal virologic control is highly correlated with RBD-specific secretory IgA antibodies.Our data show that 3Ro-NC plus KFD is a promising mucosal vaccine candidate for protection against SARS-CoV-2 Omicron infection,pathology and transmission potential.