间接FLISA法检测钩端螺旋体特异性IgM方法的探讨

为研制钩端螺旋体（钩体）特异性IgM检测试剂,并用于早期诊断钩体病,以钩体外膜蛋白为抗原,探索间接ELISA法检测钩体特异性IgM的各项实验条件,并对钩体病患者血清标本进行检测,结果,１０５份健康人血ＩgM阴性,钩体IgM阳性血清可被特异性阻断,２－巯基乙醇破坏试验阳性,试剂存放４℃和３７℃4天的检测结果基本一致,检测临床钩体病人112份血清,IgM阳性83份,阳性率74．11％,与常规TAT法基本一致,0－7病日的阳性率明显高于MAT法,说明该法检测钩体病IgM具有特异,敏感,快速,稳定,简便等优点,对钩体病早期诊断有一定的价值。     

内蒙地区发热患者血清中冠状病毒抗体的检测

目的分析内蒙地区发热患者中冠状病毒的感染情况。方法以SARS冠状病毒感染Vero细胞涂片为冠状病毒抗原片,用间接免疫荧光法分别检测55例发热患者和68例正常人血清中冠状病毒的IgG、IgM抗体。结果发热患者血清中冠状病毒IgG抗体和IgM抗体阳性率分别为29.1%(16/55)和10.9%(6/55),而正常人血清中只检测到2.9%(2/68)的IgG抗体,且未检测到IgM抗体,2组患者的IgG和IgM抗体阳性率比较差异均有显著性;随机选取7例患者的IgG阳性血清进行SRAS冠状病毒的特异性抗体封闭实验,结果有6例血清仍为阳性,有1例血清转为阴性,说明冠状病毒IgG抗体阳性血清中85.7%为普通冠状病毒特异性,14.3%为SARS冠状病毒特异性。结论普通冠状病毒是内蒙地区发热患者的主要病原体之一,部分患者还存在SARS冠状病毒的既往感染。     

检测梅毒螺旋体抗体的纤维膜条方法的建立及其在诊断中的应用

目的：建立以纤维膜为载体的检测梅毒螺旋体抗体的方法,检查病人血清中对梅毒螺旋体多种抗原的抗体,用于梅毒感染的诊断。方法：将基因工程表达及纯化的梅毒螺旋体蛋白tp15、tp17、tp42和tp47分别结合在纤维膜上,用载抗原的纤维膜条检查血清中的抗体,抗体阳性者在相应抗原位置显示出特异条带。结果：梅毒螺旋体感染者血清中存在特异性抗体,在检查的460份临床诊断的患者血清中,对tp15、tp17、tp42和tp47抗原的抗体检出率分别为41.3%、100%、98.7%和51.7%;134份献血员血清抗体阴性。结论：建立的检测梅毒螺旋体感染的方法可同时检查对多种抗原的抗体,以纤维膜条作为诊断条检测血清抗体方法简便,用于临床诊断更特异、更敏感。     

ELISA法检测流行性腮腺炎病毒感染特异性IgM抗体的研究

用流行性腮腺炎(流腮)病毒Enders株接种鸡胚尿囊腔培养,尿囊液经聚乙二醇6000处理制备流腮病毒抗原,用ELISA法检测流腮患者血清中特异性IgM抗体,其敏感性,特异性、重复性和稳定性都很高。 79份流腮患者血清,检出特异性IgM72份,阳性率为91％,32例非流腮患者IgM全部阴性、两者有极显著差异(P<0.01)。 10份血清作血清倍比稀释至1∶3200测IgM仍全部阳性,1∶6400稀释仅1例阴性,1∶12800稀释5例中仍有2例阳性。 10份血清作流腮抗原特异性抗体阻断试验,光密度抑制率均大于50％,平均为87％,10份标本作2-ME和SPA阻断后检测IgM抗体,结果2-ME阻断标本全部阴转,而SPA阻断标本仍阳性,证实所检测为流腮特异性抗体。 24份标本2次重复检测流腮IgM,其阴、阳性结果一致,这期间抗原放4℃ 1个月,提示抗原的稳定性和方法的重复性都很好。本方法敏感性明显高于血凝抑制试验,其阳性率分别为91％和61％,两者有显著差异。而且所用试剂简单经济,操作简便,快速,适用于临床早期诊断,易于广泛推广应用。     

重组钩端螺旋体外膜蛋白酶联免疫吸附(ELISA)检测方法的建立

目的建立以重组外膜蛋白为基础的钩端螺旋体抗体间接ELISA检测方法。方法以基因重组技术获取重组钩端螺旋体外膜蛋白LipL32,以该蛋白为抗原,特异的钩体抗血清进行ELISA方阵滴定、交叉性试验、阻断试验,并对北京地区的70份犬血清使用建立的ELISA方法以及德国Virion公司的全菌体钩端螺旋体ELISA试剂盒进行相互验证。结果方阵滴定试验确立以100ng/孔为抗原包被浓度,1∶160为血清稀释度。交叉性试验具有广泛性、阻断试验标明该方法特异性强、灵敏度高。两种方法数据经χ2检验,两者检出率之间差异不显著。结论重组LipL32蛋白具有结合活性。初步建立了以重组LipL32蛋白为抗原的钩端螺旋体抗体间接ELISA检测方法。     

新型布尼亚病毒抗体检测方法的建立及初步应用

目的:建立新型布尼亚病毒IgG抗体ELISA检测方法。方法:用基因工程重组表达的新型布尼亚病毒NP抗原包被酶联板,建立间接ELISA法检测新型布尼亚病毒IgG抗体,并进行特异性和灵敏度评价,健康人群中检测结果计算临界值(均值+3标准差)。检测70例发热伴血小板减少综合征患者恢复血清和69份健康人血清样品。结果:在70份患者血清样品中,检测出新型布尼亚病毒IgG抗体阳性51例,阳性率为72.14%(51/70);69份健康人血清样品中,检测出1份阳性,特异性为98.6%(1/69)。结论:建立的新型布尼亚病毒IgG抗体ELISA检测方法特异性强、灵敏度高,可用于新型布尼亚病毒感染的检测及流行病学调查。     

抗细小病毒B19-VP2单克隆抗体的建立

制备抗细小病毒B19－VP2单克隆抗体,用于检测人血清中的B19抗原,辅助诊断相关疾病;也可用于制备人类细小病毒基因工程疫苗。用纯化的基因工程表达的B19－VP2蛋白免疫BALB/c小鼠,取免疫小鼠的脾细胞和小鼠骨髓瘤Sp2/0细胞融合,有限稀释法克隆细胞。ELISA及IF证明抗体特异性。克隆筛选出4株细胞,并初步建立了检测B19－VP2抗原的双抗体夹心酶联免疫吸附试验,为双抗体夹心法检测B19抗原为临床相关疾病诊断提供了检测手段。     

问号钩端螺旋体中一个新的OmpA家族蛋白抗原性及保守性研究

目的克隆表达和鉴定问号钩端螺旋体(L.interrogans)黄疸出血群赖型赖株中一个新的外膜蛋白(Omp)A家族基因LA0301,研究LA0301编码蛋白的抗原性和在15个钩端螺旋体(简称钩体)血清群代表株中的保守性,探讨其在疫苗研究中的意义。方法生物信息学软件分析预测LA0301的特征。构建原核表达重组体pQE31-LA0301,经IPTG诱导后用十二烷基磺酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)及蛋白质印迹法(Western blot)鉴定表达情况。用表达的重组蛋白免疫BALB/c小鼠,Western印迹检测其免疫反应性和在不同血清型钩体中的保守性。酶联免疫吸附试验(ELISA)和Western印迹检测兔抗钩体全菌血清中的LA0301编码蛋白的抗体。结果生物信息学预测结果显示,LA0301具有OmpA家族的结构域。克隆表达了重组质粒pQE31-LA0301,重组蛋白能刺激BALB/c小鼠产生特异性抗体,效价为1:32000。在兔抗钩体全菌血清中检测到特异的LA0301蛋白抗体,并在15个血清群的代表株钩体中均可检测到LA0301蛋白。结论LA0301蛋白是问号钩体中一个新的OmpA家族蛋白,具有良好的抗原性和保守性,并且能在钩体感染的过程中刺激机体产生相应的抗体。为进一步研究钩体新型疫苗候选基因奠定了基础。     

SLE患者血清中SARS-CoV抗体阳性原因分析

为了探讨严重急性呼吸综合征(SARS)冠状病毒(SARS-CoV)抗体测定在系统性红斑狼疮(SLE)患者中的假阳性问题,应用酶联免疫吸附试验(ELISA)和荧光定量RT-PCR技术检测了66例正常对照和31例SLE患者血清中SARS-CoV抗体的阳性率。结果,66例正常对照中,IgM抗体均阴性,IgG抗体的阳性率为3.0%(2/66);31例SLE患者中,IgM抗体和IgG抗体阳性率分别为29%(9/31)和58.1%(18/31),IgG抗体和IgM抗体同时阳性为22.6%(7/31)。经RTPCR检测,上述阳性病例均为阴性。结论:用非纯化抗原制备的ELISA试剂盒测定SLE患者的SARS-CoV抗体,可能出现假阳性,两种抗体同时测定可降低诊断的假阳性率,提高诊断的特异性。在SLE患者中出现假阳性的原因可能与包被的抗原有关。     

猪圆环病毒2型(PCV2)核衣壳蛋白免疫原性的鉴定和应用及其多抗在PCV2感染诊断中的应用

猪圆环病毒2型ORF2编码与病毒毒力相关的结构蛋白--核衣壳蛋白(Cap),该蛋白可以用于PCV2感染的血清学调查,但不同区域的PCV2分离株的ORF2特别是其抗原表位序列存在一定的突变.本研究将PCV2浙江分离株ORF2的主要抗原表位以及PCV1 ORF2进行了原核表达,将分别纯化的融合蛋白Cap2s和Cap1s免疫SPF兔后制备多抗,并进一步分析了纯化蛋白的免疫原性和多抗的特性.Western blot结果表明无论Cap2s和Cap1s均能与两个多抗发生交叉反应,而PCV2或PCV1阳性猪血清只能分别特异性地识别Cap2s和Cap1s.IFA结果则证明两个多抗对于天然Cap蛋白无交叉反应性.利用Cap2s作为包被抗原对13个猪场的259份血清样品的PCV2抗体进行ELISA检测,平均阳性率为80.69%(209/259),而各猪场的阳性率差异较大(48.28%～100%).以上结果表明Cap2s可作为一个型特异性抗原用于浙江省本地猪场猪群血清中PCV2抗体的监控,而其多抗也可用于免疫组化对PCV2感染进行有效诊断.     

Development of species-specific PCR primer sets for the detection of Leptospira

Spirochetes of the genus Leptospira infect animals and humans and are the causative agents for the emerging infectious disease leptospirosis. Rapid and simple assays for the identification of individual Leptospira species are currently not available. For identification of individual Leptospira species, PCR primers that detect the ompL1 gene sequence for the majority of pathogenic leptospires were developed in this study. The primer pairs detect Leptospira interrogans, Leptospira borgpetersenii, Leptospira kirschneri, Leptospira santarosai, Leptospira weilii and Leptospira noguchii, without cross-reacting with other Leptospira species. The development of the primers revealed a divergence of the ompL1 gene within L. interrogans, splitting this species into two separate groups. The species-specific primers will be especially useful in epidemiological studies and disease outbreak investigations for the detection of Leptospira species in human, animal and environmental samples.     

Differential TLR recognition of leptospiral lipid A and lipopolysaccharide in murine and human cells

Leptospira interrogans is a spirochete that is responsible for leptospirosis, a zoonotic disease. This bacterium possesses an unusual LPS that has been shown to use TLR2 instead of TLR4 for signaling in human cells. The structure of its lipid A was recently deciphered. Although its overall hexa-acylated disaccharide backbone is a classical feature of all lipid A forms, the lipid A of L. interrogans is peculiar. In this article, the functional characterization of this lipid A was studied in comparison to whole parental leptospiral LPS in terms of cell activation and use of TLR in murine and human cells. Lipid A from L. interrogans did not coagulate the Limulus hemolymph. Although leptospiral lipid A activated strongly murine RAW cells, it did not activate human monocytic cells. Results obtained from stimulation of peritoneal-elicited macrophages from genetically deficient mice for TLR2 or TLR4 clearly showed that lipid A stimulated the cells through TLR4 recognition, whereas highly purified leptospiral LPS utilized TLR2 as well as TLR4. In vitro experiments with transfected human HEK293 cells confirmed that activation by lipid A occurred only through murine TLR4-MD2 but not through human TLR4-MD2, nor murine or human TLR2. Similar studies with parental leptospiral LPS showed that TLR2/TLR1 were the predominant receptors in human cells, whereas TLR2 but also TLR4 contributed to activation in murine cells. Altogether these results highlight important differences between human and mouse specificity in terms of TLR4-MD2 recognition that may have important consequences for leptospiral LPS sensing and subsequent susceptibility to leptospirosis.     

The development and function of memory regulatory T cells after acute viral infections

Leptospira interrogans is responsible for a zoonotic disease known to induce severe kidney dysfunction and inflammation. In this work, we demonstrate that L. interrogans induces NLRP3 inflammasome-dependent secretion of IL-1β through the alteration of potassium transport in bone marrow-derived macrophages. Lysosome destabilization also contributed to the IL-1β production upon stimulation with live, but not dead, bacteria. Using bone marrow-derived macrophages from various TLRs and nucleotide-binding oligomerization domain-deficient mice, we further determined that IL-1β production was dependent on TLR2 and TLR4, suggesting a participation of the leptospiral LPS to this process. Hypokaliemia in leptospirosis has been linked to the presence of glycolipoprotein, a cell wall component of L. interrogans that is known to inhibit the expression and functions of the Na/K-ATPase pump. We show in this study that glycolipoprotein activates the inflammasome and synergizes with leptospiral LPS to produce IL-1β, mimicking the effect of whole bacteria. These results were confirmed in vivo, as wild-type mice expressed more IL-1β in the kidney than TLR2/4-deficient mice 3 d postinfection with L. interrogans. Collectively, these findings provide the first characterization, to our knowledge, of bacteria-induced activation of the NLRP3 inflammasome through the downregulation of a specific host potassium transporter.     

Molecular evolution and mosaicism of leptospiral outer membrane proteins involves horizontal DNA transfer

Leptospires belong to a genus of parasitic bacterial spirochetes that have adapted to a broad range of mammalian hosts. Mechanisms of leptospiral molecular evolution were explored by sequence analysis of four genes shared by 38 strains belonging to the core group of pathogenic Leptospira species: L. interrogans, L. kirschneri, L. noguchii, L. borgpetersenii, L. santarosai, and L. weilii. The 16S rRNA and lipL32 genes were highly conserved, and the lipL41 and ompL1 genes were significantly more variable. Synonymous substitutions are distributed throughout the ompL1 gene, whereas nonsynonymous substitutions are clustered in four variable regions encoding surface loops. While phylogenetic trees for the 16S, lipL32, and lipL41 genes were relatively stable, 8 of 38 (20%) ompL1 sequences had mosaic compositions consistent with horizontal transfer of DNA between related bacterial species. A novel Bayesian multiple change point model was used to identify the most likely sites of recombination and to determine the phylogenetic relatedness of the segments of the mosaic ompL1 genes. Segments of the mosaic ompL1 genes encoding two of the surface-exposed loops were likely acquired by horizontal transfer from a peregrine allele of unknown ancestry. Identification of the most likely sites of recombination with the Bayesian multiple change point model, an approach which has not previously been applied to prokaryotic gene sequence analysis, serves as a model for future studies of recombination in molecular evolution of genes.     

Evolutionary Implication of Outer Genes ompL1, lipL32 and lipL41 Membrane Lipoprotein-Encoding of Pathogenic Leptospira Species

Leptospirosis is recognized as the most widespread zoonosis with a global distribution. In this study, the antigenic variation in Leptospira interrogans and Leptospira borgpetersenii isolated from human urine and field rat kidney was preliminarily confirmed by microscopic agglutination test using monoclonal antibodies, and was further subjected to amplification and identification of outer membrane lipoproteins with structural gene variation. Sequence similarity analysis revealed that these protein sequences, namely OmpL1, LipL32 and LipL41, showed no more homologies to outer membrane lipoproteins of non-pathogenic Leptospira and other closely related Spirochetes, but showed a strong identity within L. interrogans, suggesting intra-specific phylogenetic lineages that might be originated from a common pathogenic leptospiral origin. Moreover, the ompL1 gene showed more antigenic variation than lipL32 and lipL41 due to less conservation in secondary structural evolution within closely related species. Phylogenetically, ompL1 and lipL41 of these strains gave a considerable proximity to L. weilii and L. santarosai. The ompL1 gene of L. interrogans clustered distinctly from other pathogenic and non-pathogenic leptospiral species. The diversity of ompL genes has been analyzed and it envisaged that sequence-specific variations at antigenic determinant sites would result in slow evolutionary changes along with new serovar origination within closely related species. Thus, a crucial work on effective recombinant vaccine development and engineered antibodies will hopefully meet to solve the therapeutic challenges.Key words: Leptospira, ompL1, lipL32, lipL41, phylogeny, antigenic variation     

Leptospirosis prevalence in Chinese populations in the last two decades

Leptospirosis is a common zoonotic disease in China. From 1991 to 2010, its average annual incidence was 0.70 cases per 100,000 population. During these two decades, three major outbreaks of leptospirosis occurred due to flooding and heavy rainfall. Leptospira interrogans serogroup Icterohaemorrhagiae serovar Lai is the predominant leptospire responsible for at least 60% of Chinese cases, and Apodemus agrarius serves as the major animal host. Based on the differences in predominant leptospiral serovars, epidemic features and incidence, there are three leptospirosis-prevalent regions in China. However, the incidence has significantly decreased in the last ten years.     

Assay for measuring relative potency of leptospiral bacterins containing serovar pomona

An enzyme-linked immunosorbent assay (ELISA) was developed for the quantitation of leptospiral antigen in bacterins containing Leptospira interrogans serovar pomona type kennewicki. A monoclonal antibody (MAb), 2D7, which is directed against a surface antigen on whole cells of L. interrogans serovar pomona type kennewicki, was used in the assay. The capture of antigen in bacterins by a polyclonal antiserum was followed by the addition of the 2D7 ascites fluid, an anti-mouse conjugate and substrate. Biologicals evaluated with this system included preparations containing type kennewicki antigen (homologous) and those not containing type kennewicki antigen (heterologous). Heterologous bacterins gave optical density (OD) values comparable to those of blank wells. Homologous bacterins yielded OD values equal to or greater than those of the National Veterinary Services Laboratories (NVSL) reference pomona bacterin. The relative potencies (RP) of 84 licensed commercial Leptospira pomona bacterin serials were evaluated against the NVSL reference pomona bacterin using the NVSL Relative Potency computer program. Random samples of 1, 2, 3 and 5 ml dose products were selected for evaluation with this system. All products tested passed the hamster potency assay required for leptospiral bacterins. This ELISA system enables detection of antigen in bacterins containing L. interrogans serovar pomona type kennewicki and demonstrates the potential for in vitro testing of leptospiral bacterins.     

The OmpL37 Surface-Exposed Protein Is Expressed by Pathogenic Leptospira during Infection and Binds Skin and Vascular Elastin

Pathogenic Leptospira spp. shed in the urine of reservoir hosts into freshwater can be transmitted to a susceptible host through skin abrasions or mucous membranes causing leptospirosis. The infection process involves the ability of leptospires to adhere to cell surface and extracellular matrix components, a crucial step for dissemination and colonization of host tissues. Therefore, the elucidation of novel mediators of host-pathogen interaction is important in the discovery of virulence factors involved in the pathogenesis of leptospirosis. In this study, we assess the functional roles of transmembrane outer membrane proteins OmpL36 (LIC13166), OmpL37 (LIC12263), and OmpL47 (LIC13050), which we recently identified on the leptospiral surface. We determine the capacity of these proteins to bind to host tissue components by enzyme-linked immunosorbent assay. OmpL37 binds elastin preferentially, exhibiting dose-dependent, saturating binding to human skin (K_d, 104±19 nM) and aortic elastin (K_d, 152±27 nM). It also binds fibrinogen (K_d, 244±15 nM), fibrinogen fragment D (K_d, 132±30 nM), plasma fibronectin (K_d, 359±68 nM), and murine laminin (K_d, 410±81 nM). The binding to human skin elastin by both recombinant OmpL37 and live Leptospira interrogans is specifically enhanced by rabbit antiserum for OmpL37, suggesting the involvement of OmpL37 in leptospiral binding to elastin and also the possibility that host-generated antibodies may promote rather than inhibit the adherence of leptospires to elastin-rich tissues. Further, we demonstrate that OmpL37 is recognized by acute and convalescent leptospirosis patient sera and also by Leptospira-infected hamster sera. Finally, OmpL37 protein is detected in pathogenic Leptospira serovars and not in saprophytic Leptospira. Thus, OmpL37 is a novel elastin-binding protein of pathogenic Leptospira that may be promoting attachment of Leptospira to host tissues.