Validation of enzyme-linked immunosorbent assays for the diagnosis of bovine brucellosis

The purpose of this study was to evaluate the performance of the indirect enzyme immunoassay (IELISA) and the competitive enzyme immunoassay (CELISA) for the diagnosis of bovine brucellosis in comparison to conventional serological tests routinely used in Argentina. Serum samples (n = 3500), from Brucella-free herds, from vaccinated cattle and from naturally infected cattle, were tested by the following tests: buffered antigen agglutination test (BPAT), rose bengal test (RBT), 2-mercaptoethanol test (2-ME), complement fixation test (CFT), IELISA and CELISA. Sensitivity and specificity of the BPAT, RBT, IELISA and CELISA were determined relative to the 2-ME and the CFT. The CELISA was considered suitable for eliminating most serological reactions of vaccinated animals and was more specific than the other tests. The results indicate the potential use of the CELISA as a complementary assay in the brucellosis control and eradication program in Argentina and other countries, where Brucella abortusstrain 19 vaccination is mandatory.     

How to substantiate eradication of bovine brucellosis when aspecific serological reactions occur in the course of brucellosis testing

Collaborative work was financed by the EU to develop and assess new diagnostic tools that can differentiate between bovine brucellosis and bovine infections due to Yersinia enterocolitica O:9 either in conjunction with, or as an alternative to, the classical serological, bacteriological or allergic skin tests. Sixteen heifers were experimentally infected with Brucella abortus biovar 1 (five heifers), Brucella suis biovar 2 (two heifers), Y. enterocolitica O:9 (six heifers) and Y. enterocolitica O:3 (three heifers). Four heifers, naturally infected with Y. enterocolitica O:9 that presented aspecific brucellosis serological reactions were also included in the experiment. A self-limited infection was induced in cattle by B. suis biovar 2. All the brucellosis serological tests used, i.e. the slow agglutination test (SAW), the Rose Bengal test (RB), the complement fixation test (CFT), indirect and competitive ELISA’s, lacked specificity when used to analyze sera from Y. enterocolitica O:9 infected animals. A Yersinia outer membrane proteins (YOPs)-ELISA was also used and although the test is able to detect a Yersinia group infection, it provided no evidence of whether or not there is a possible brucellosis infection when dual infections are present. The brucellergen IFN-γ test showed a lack of specificity also. The only test that was proven to be specific is the brucellergen skin test. All brucellosis serological tests, except the indirect ELISA, were limited in their ability to detect B. abortus persistently infected animals.

Based on these experimental studies, a strategy was implemented as part of the year 2001 Belgian Brucellosis Eradication Program to substantiate the eradication of bovine brucellosis. Epidemiological inquiries have identified risk factors associated with aspecific serological reactions, possible transmission and infection of cattle by B. suis biovar 2 from infected wild boars; and both legal and administrative measures taken by the veterinary services. No cases of bovine brucellosis have been confirmed in Belgium since March 2000.     

Characterization of the caprine model for ruminant brucellosis

The relationship between man, the goat, and brucellosis is historical. Today Brucella melitensis and Brucella abortus pose a serious economic and public health threat in many countries throughout the world. Infection of pregnant goats and sheep with B. melitensis results in abortion during the third trimester of pregnancy. Although nearly eradicated in the US, bovine brucellosis is still a problem in many countries and the potential for re-infection of domestic stock from wildlife reservoirs in this country is a regulatory nightmare. Humans infected with this pathogen develop undulant fever, which is characterized by pyrexia, arthritis, osteomyelitis, and spondylitis. Although available for both organisms, currently available vaccines have problems ranging from false positive serological reactions to limited efficacy in different animal species. With the continued need for new and better vaccines, we have further developed a goat model system to test new genetically derived strains of B. melitensis and B. abortus for virulence as measured by colonization of maternal and fetal tissues, vaccine safety, and vaccine efficacy.     

实时荧光定量PCR检测布鲁菌方法的建立

旨在建立实时荧光定量PCR检测布鲁菌的方法。经选取高度保守的具布鲁菌属特异性的BSP31基因设计了一对引物及探针,并采用矩阵法优化反应体系,筛选出引物、探针、dNTP和Mg2+最优浓度配比,同时进行了特异性和灵敏性试验,建立了实时荧光定量PCR检测布鲁菌的方法。该方法可用于对布鲁菌病普查监测及进出境动物及其产品的检验检疫。     

布鲁氏菌致病及免疫机制研究进展

布鲁氏菌病是由布鲁氏菌属的细菌引起的人畜共患传染病 ,目前布鲁氏菌属的细菌主要有七个种。随着分子生物学技术的发展 ,对布鲁氏菌的致病机制在分子水平上有了更进一步的理解 :布鲁氏菌自身一些与致病有关的基因使得布鲁氏菌逃避了巨噬细胞的杀伤作用 ,在巨噬细胞内存活和定居。在布鲁氏菌病免疫过程中 ,先天性免疫应答主要通过补体、巨噬细胞、天然杀伤细胞来参与 ,获得性免疫应答中 ,CD4 、CD8 、rδT细胞起很重要的作用。文章围绕这些与致病、免疫有关的基因及参与免疫反应细胞的研究进展进行了探讨 ,可为今后进行布鲁氏菌病预防及开发新型基因工程苗提供理论依据。     

布鲁氏菌分泌蛋白BPE005的亚细胞定位及与宿主细胞互作蛋白的筛选

【目的】 分析布鲁氏菌分泌蛋白BPE005的蛋白结构及细胞定位,筛选宿主细胞内与其存在相互作用的靶蛋白,为后续研究BPE005的生物学功能奠定基础。【方法】 通过生物信息学软件对BPE0005的蛋白结构进行初步分析;构建PDRRED2-C1-BPE005重组荧光定位载体,转染人胚肾上皮细胞293T,通过扫描激光共聚焦显微镜观察BPE005的细胞定位;构建PGBKT7-BPE005诱饵载体,验证诱饵载体是否有细胞毒性和自激活现象;以小鼠巨噬细胞RAW264.7 mRNA的cDNA文库为AD文库菌液,检测文库滴度,通过酵母双杂交系统筛选宿主细胞内与BPE005相互作用的靶蛋白。【结果】 布鲁氏菌分泌蛋白BPE005属于疏水性蛋白,内含有大量的无规则卷曲、α-螺旋和延伸链。成功构建PDRRED2-C1-BPE005荧光定位载体和PGBKT7-BPE005诱饵蛋白载体,BPE005定位于宿主细胞核。PGBKT7-BPE005诱饵蛋白载体无酵母细胞毒性和自激活现象,AD文库菌液滴度>2×10⁷/mL,筛选出4个宿主细胞内与BPE0005存在相互作用的蛋白:RNA聚合酶Ⅱ多肽G、补体因子H、鸟苷酸环化酶2G及颗粒蛋白。经复筛、测序、BLAST比对、一对一验证后,最终筛选出1个在宿主细胞内与BPE005具有较强相互作用的靶蛋白(RNA聚合酶Ⅱ多肽G)。对该蛋白的作用网络分析表明,RNA聚合酶Ⅱ多肽G对宿主细胞内mRNA的转录和合成具有重大影响。【结论】 布鲁氏菌分泌蛋白BPE005定位于宿主细胞核,在宿主细胞内可与RNA聚合酶Ⅱ多肽G产生较强相互作用,对进一步阐明布鲁氏菌感染过程中关键效应分子的作用机制具有指导意义。     

线粒体融合蛋白2基因干扰与过表达对布鲁氏菌诱导巨噬细胞凋亡的影响

[目的] 试验旨在探究线粒体融合蛋白2（MFN2）基因干扰与过表达对布鲁氏菌诱导小鼠巨噬细胞凋亡的影响。[方法] 利用RNA干扰技术设计3条特异性针对MFN2基因的siRNA序列（siMFN2-450、siMFN2-1661、siMFN2-2275）和1条阴性干扰序列（siMFN2-Negative）;利用空质粒pcDNA3.1-EGFP通过过表达技术构建1个重组质粒pcDNA3.1-EGFP-MFN2。双酶切法鉴定过表达重组质粒pcDNA3.1-EGFP-MFN2,通过实时荧光定量PCR和Western blotting检测筛选最佳干扰序列并鉴定重组质粒的过表达效率,使用筛选出的最佳干扰序列和鉴定过表达后的重组质粒分别构建MFN2基因干扰及过表达的转染巨噬细胞模型;用牛种布鲁氏菌疫苗株A19侵染巨噬细胞,按照细菌数：细胞个数=100：1的比例侵染24 h,通过实时荧光定量PCR和Western blotting检测B淋巴细胞瘤-2（Bcl-2）相关X蛋白（BAX）的表达情况,用流式细胞术检测细胞凋亡情况。[结果] 双酶切结果显示,pcDNA3.1-EGFP-MFN2过表达重组质粒构建成功;实时荧光定量PCR和Western blotting结果显示,siMFN2-1661组MFN2的表达极显著降低（P<0.01）,pcDNA3.1-EGFP-MFN2组MFN2的表达极显著增加（P<0.01）,成功构建干扰及过表达MFN2基因的转染巨噬细胞模型;布鲁氏菌侵染干扰MFN2基因表达的巨噬细胞后,BAX蛋白表达水平显著高于siMFN2-Negative组（P<0.05）,BAX转录水平和细胞凋亡率极显著高于siMFN2-Negative组（P<0.01）;布鲁氏菌侵染过表达MFN2基因的巨噬细胞后,BAX的转录及蛋白表达水平均显著低于pcDNA3.1-EGFP组（P<0.05）,细胞凋亡率极显著低于pcDNA3.1-EGFP组（P<0.01）。[结论] 本试验结果表明,干扰MFN2基因的表达会增强布鲁氏菌诱导细胞凋亡的能力,而过表达MFN2基因则会抑制布鲁氏菌诱导细胞凋亡的能力,结果可为研究MFN2基因的生物学功能提供参考,为进一步解析布鲁氏菌的致病机制提供理论基础。     

布鲁菌转录调节因子HFQ诱导机体免疫反应的分析

旨在分析布鲁菌（Brucella）转录调节因子HFQ诱导机体产生的免疫反应。以热灭活牛种布鲁菌S2308为模板,根据GenBank登录的S2308 hfq基因序列（BAB1_1134）设计引物,PCR扩增hfq基因片段后,将其克隆至原核表达载体pET-32a,转化大肠杆菌BL21（DE3）感受态细胞,诱导HFQ蛋白表达;利用SDS-PAGE电泳以及Western blot对重组HFQ蛋白（rHFQ）进行分析;pET-32a空载体、rHFQ和疫苗株M5-90刺激小鼠巨噬细胞RAW 264.7,利用ELISA试剂盒检测细胞因子IFN-γ和IL-4的表达水平;将pET-32a、rHFQ和M5-90免疫小鼠后,检测小鼠脾细胞中IFN-γ和IL-4的水平,以及小鼠血清中IgG抗体水平。结果显示,hfq基因大小为237 bp,编码79个氨基酸,rHFQ大约在25.8 ku处出现蛋白条带,纯化后为单一条带。Western blot结果显示,rHFQ具有较好的反应原性。rHFQ刺激RAW 264.7后,诱导IFN-γ和IL-4的水平与M5-90组相似,显著高于PBS组和pET-32a空载体组,且随着刺激时间的延长而升高。rHFQ免疫小鼠后,诱导脾细胞产生IFN-γ和IL-4的水平,小鼠血清中IgG的水平与M5-90组相似,显著高于PBS组和pET-32a空载体组。布鲁菌HFQ蛋白具有较好的反应原性,并能诱导机体产生较高的细胞免疫和体液免疫水平,是布鲁菌亚单位疫苗研制较理想的候选抗原。     

Brucella abortus is Prevalent in Both Humans and Animals in Bangladesh

To determine the role of different Brucella (B.) spp. in Bangladesh, 62 animal samples and 500 human sera were tested. Animal samples from cattle, goats and sheep (including milk, bull semen, vaginal swabs and placentas) were cultured for Brucella spp. Three test‐positive human sera and all animal samples were screened by Brucella genus‐specific real‐time PCR (RT‐PCR), and positive samples were then tested by IS711 RT‐PCR to detect B. abortus and B. melitensis DNA. Only B. abortus DNA was amplified from 13 human and six animal samples. This is the first report describing B. abortus as the aetiological agent of brucellosis in occupationally exposed humans in Bangladesh. Of note is failure to detect B. melitensis DNA, the species most often associated with human brucellosis worldwide. Further studies are required to explore the occurrence of Brucella melitensis in Bangladesh.