Rapid genotyping of HLA-B27 among Korean population by real-time PCR melting curve analysis

BackgroundReal-time PCR and melting curve analysis is the relatively recent method for HLA-B27 genotyping, which has advantages of being simple and rapid.MethodsThe accuracy of melting curve analysis for HLA-B27 was assessed in 153 clinical samples and 52 DNA samples from International Histocompatibility Workshop (IHW) cell lines, with sequence-based typing (SBT) as the reference method. We predicted melting reaction for various HLA-B27 subtypes using simulation software.ResultsFor clinical samples, 53 HLA-B27-positive and 100 negative results by melting curve analysis were confirmed by completely concordant SBT results. The B*27:05 allele was found in 50 patients, and the B*27:04 allele in 3 patients. Among 62 known alleles, 21 alleles had differences in the target sequence, including 10 alleles having mismatches in the primer binding site. In these alleles, differences in melting points (T_m) were predicted to be ≤ 1.2 °C. The predicted results were obtained when IHW samples were tested, which revealed slight lower T_m for B*27:06 and negative results for B*27:07.ConclusionsGenotyping of HLA-B27 by melting curve analysis was fast and reliable for routine laboratory testing for frequent alleles. In silico melting simulations provided useful information about the utility and limitation of this method for diverse HLA-B27 alleles.     

Simultaneous detection of Marburg virus and Ebola virus with TaqMan‐based multiplex real‐time PCR method

BackgroundMarburg virus (MARV) and Ebola virus (EBOV) are acute infections with high case fatality rates. It is of great significance for epidemic monitoring and prevention and control of infectious diseases by the development of a rapid, specific, and sensitive quantitative PCR method to detect two pathogens simultaneously.MethodsPrimers and TaqMan probes were designed according to highly conserved sequences of these viruses. Sensitivity, specificity, linear range, limit of detection, and the effects of hemolysis and lipid on real‐time qPCR were evaluated.ResultsThe linearity of the curve allowed quantification of nucleic acid concentrations in range from 10³ to 10⁹ copies/ml per reaction (MARV and EBOV). The limit of detection of EBOV was 40 copies/ml, and MARV was 100 copies/ml. It has no cross‐reaction with other pathogens such as hepatitis b virus (HBV), hepatitis c virus (HCV), human papillomavirus (HPV), Epstein‐Barr virus (EBV), herpes simplex virus (HSV), cytomegalovirus (CMV), and human immunodeficiency virus (HIV). Repeatability analysis of the two viruses showed that their coefficient of variation (CV) was less than 5.0%. The above results indicated that fluorescence quantitative PCR could detect EBOV and MARV sensitively and specifically.ConclusionsThe TaqMan probe‐based multiplex fluorescence quantitative PCR assays could detect EBOV and MARV sensitively specifically and simultaneously.     

Rapid DNA typing of HLA-B27 allele by real-time PCR using lightcycler technology

For clinical diagnostic routine we developed a fast DNA typing of HLA-B27 by PCR and real-time detection using LightCycler technology. The method combines the sensitivity and specificity of PCR with the swiftness of the LightCycler system. The amplification step was performed with a primer set coding for a region in the third exon common to B*2701 to B*2705. The PCR cycles were monitored continuously using the SYBR Green I dye. Beta-globin was used as an internal control. An analysis of 32 samples with one PCR run was completed within 40 minutes. After amplification a melting curve analysis permitted the accurate identification of the PCR amplicons. The mean melting temperatures (Tm) were 90.5 degrees C and 87.3 degrees C, which are characteristic for HLA-B27 and beta-globin, respectively. A comparison of 300 samples which were typed for HLA-B27 with a conventional sequence-specific polymerase chain reaction (SSP-PCR) and with the new method demonstrated a perfect correlation (specificity 100%). In summary, the method described is fast, reliable, cost-effective and well adapted for routine laboratory testing.     

中国汉族人群HLA-B*40组的多态性研究

为了研究中国汉族人群HLA—B^*40等位基因的分布特点，探讨其可能对临床供者选择的影响，从中华骨髓库深圳分库中随机抽取381名志愿供者，用PCR—SSO方法进行HLA—B基因分型；另从已分型的1270例供者中选出低分辨率结果为B^*40纯合子的样本。所有B^*40阳性标本采用PCR—SBT及PCR—SSP方法进行高分辨率分型。结果表明：随机抽取的381例样本通过Hardy—Weinberg平衡检验，HLA—B^*40的基因频率为0．1692。在实验中仅检测到B^*4001，B^*4002，B^*4003，B^*4006，其血清学特异性分属B60，B61。各等位基因相对频率B^*4001为0．1192，B^*4002为0．0154，B^*4003为0．0038．B^*4006为0．0308。B^*40纯合子在高分辨水平上检测，其等位基因表现出一定的规律性，低分辨结果为B^*40XX(B^*4001组)，一，高分辨都是B^*4001；低分辨为B^*40XX(B^*4002组)．一，高分辨则为B^*4002或B^*4006或二者杂合子。结论：中国汉族人群B^*40基因家族中B^*4001占绝对优势。为了选择最适供者，建议临床配型中使用高分辨率基因分型。     

中国北方汉族骨髓供者HLA-B＊15组基因多态性的PCR-SBT分型研究

为了研究中国北方汉族骨髓供者HLA—B＊15等位基因的分布特征，探讨其可能对临床供体选择的影响，从中华骨髓库陕西分库内随机抽取815名已知低分辨分型结果中国北方汉族骨髓供者，采用聚合酶链反应-碱基序列直接测序（PCR—SBT）方法对其中206例HLA—B＊15阳性样本和另外附加17例样本进行HLA—B位点DNA测序分析，并应用同源模建分子模拟技术对所有结果模拟出三维结构，用计算机软件Swiss—PdbViewer比较模拟结构间的差异大小。结果表明：随机抽取的815例样本HIJA—A、B、DRB1基因分布符合Hardy—Weinberg平衡定律，HIJA—B＊15基因频率为0．1379，总共检出16种HIJA—B＊15等位基因，分属7种血清学特异性，以B＊1501、B＊1511、B＊1502和B＊1518为主，频率分别为0．0485、0．0215、0．0178和0．0160，累计频率构成比占全部B＊15的75．11％，其余12种B＊15等位基因频率均〈0．0100。19例HIJA—B＊15，-测序分析表明，其中10例中低分辨水平上的纯合子中仅4例为真正意义上的B＊15xx，-纯合子，且均由各自优势基因构成。三维结构模拟分析发现同一血清型中既存在结构差异微小的等位基因，如B＊1501、1505、1507、1525、1527、1532（RMSD≤0．02nm），也存在差异较大的等位基因，如B＊1502、1511、1521之间以及B＊1503、1546之间（RMSD均为0．29nm），而一些分属不同血清型的等位基因之间结构却近似（RMSD值≤0．02nm）。结论：本研究应用PCR—SBT，首次取得了中国北方汉族样本量最大的高分辨水平HLA—B＊15基因多态性分布特征，这将有助于临床患者寻找合适供者，并为移植免疫及本地区群体遗传学等方面的研究提供了重要依据，且对于临床选择最适供者，像HLA—B＊15这样血清学特异性及基因亚型高度多态性的家族进行准确的高分辨分型是必要的。     

强直性脊柱炎患者HLA-B~* 27基因亚型及序列研究

目的研究已确诊的强直性脊柱炎(AS)患者HLA-B*27亚型的43个等位基因分布情况,为本地区临床诊断AS提供理论和实践基础。方法经HLA-B*27低分辨基因检测阳性的AS确诊患者标本70份应用PCR-SSP检测;在判读结果为B位点杂合子的27份中随机抽取17份,加上因HLA-B位点多态性及试剂盒局限性而无法判定确切结果的3份标本应用PCR-SBT检测。结果 50名患者表达HLA-B*2704阳性(包括纯合子31名,杂合子19名)2,1名患者表达HLA-B*2705阳性(包括:纯合子10名,杂合子11名),其中1名患者同时表达HLA-B*2704/2705杂合。HLA-B*2704合计阳性率为71.42%,占总标本数的70.41%;HLA-B*2705合计阳性率为30.01%,占总标本数的29.59%。通过直接计算法得出B*2704等位基因频率为0.578 6,B*2705等位基因频率为0.285 7。结论上海地区AS就诊患者HLA-B*27基因亚型为HLA-B*2704和HLA-B*2705此2种,以HLA-B*2704为主。配合应用PCR-SSP与PCR-SBT此2种分型方法具有互补意义,可以获得较为准确的分型结果。     

副溶血弧菌TaqMan双重实时-聚合酶链反应检测方法的建立

目的建立副溶血弧菌TaqMan实时-PCR和毒力基因TaqMan双重实时-PCR筛检的实验室检测方法。方法根据副溶血弧菌ItoxR/I基因的保守序列设计引物和TaqMan探针,建立检测副溶血弧菌的实时-PCR方法;根据副溶血弧菌耐热直接溶血素（thermostable direct hemolysin, Itdh/I）和耐热相关溶血素（thermostable related hemolysin, Itrh/I）基因的保守序列设计引物和探针,建立检测致病性副溶血弧菌毒力基因的双重TaqMan实时-PCR方法。对所建立的副溶血弧菌实时-PCR检测方法进行灵敏度和特异度评价。结果副溶血弧菌的检测下限为10sup2/sup拷贝/l,Itdh/I和Itrh/I双重实时PCR的检测下限为10sup2/sup拷贝/l。针对ItoxR/I基因建立的副溶血弧菌实时-PCR方法对11种其他弧菌和肠道细菌的染色体无扩增。结论建立的方法能够特异和敏感地检测副溶血弧菌,并能确定致病性副溶血弧菌的毒力基因,能作为副溶血弧菌的灵敏和快速检测方法。     

广东汉族人群HLA-B~* 15等位基因分布

目的了解广东献血者汉族人群HLA-B*15等位基因的多态性。方法从1 691名广东汉族献血者中采用中/低分辨分型获得带有HLA-B*15基因型466例样本,进一步应用PCR-SBT技术进行测序分型,获得广东汉族人群B*15高分辨分型结果。应用PyPop软件计算HLA-B*15各等位基因频率,同时与其他人群资料进行比较。结果共检测到16种已知HLA-B*15等位基因,其中以B*15∶02(64.75%)最常见,其次为B*15∶01(13.26%),B*15∶25(4.554%),B*15∶27(4.158%),B*15∶12(3.960%),这5种等位基因占B*15等位基因家族的90.69%。在B*15等位基因家族中,表达B75抗原的等位基因B*15∶02、B*15∶11和B*15∶21共占67.92%,但表达B62抗原的B*15等位基因多态性最强,共检出6种等位基因。结论广东汉族人群中HLA-B*15等位基因表现出高度的多态性及其特有的分布特征。     

弗氏枸橼酸杆菌TaqMan实时荧光定量-聚合酶链反应检测方法的建立

目的 建立针对弗氏枸橼酸杆菌的TaqMan实时荧光定量-聚合酶链反应(real time-PCR)检测方法。 方法 针对弗氏枸橼酸杆菌的特有序列设计引物和TaqMan探针,扩增目的基因建立标准曲线,确定检测方法的灵敏度;对20种其他肠道致病菌及院内感染中常见的致病菌进行检测,评价该检测方法的特异性;使用牛奶模拟标本评价方法在实际检测工作中应用性。 结果 TaqMan real time-PCR检测方法对弗氏枸橼酸杆菌重组质粒的检测灵敏度为1.0101拷贝／反应体系;该检测方法在检测30种其他肠道致病菌及院内感染中常见的致病菌时未出现特异性扩增。该检测方法对牛奶模拟样本中弗氏枸橼酸杆菌检测下限为1.0102cfu/ml的菌量;通过对1.0107、1.0105和1.0103三个浓度质粒标准品的重复检测,确定本方法的组内变异系数为1.90%~3.91%;组间变异系数为1.52%~1.69%。 结论 本研究建立的TaqMan real time-PCR检测方法可作为检测弗氏枸橼酸杆菌灵敏、特异、快速的方法。     

Molecular detection and quantification of the protozoan Bonamia ostreae in the flat oyster, Ostrea edulis

Bonamia ostreae is an intracellular protozoan which is recognized as a cause of mortality in European populations of flat oysters (Ostrea edulis). Based on the recent characterization of actin genes of B. ostreae, specific primers were designed for real-time PCR using SYBR^® Green chemistry. Specificity was demonstrated by the unique melting temperature peak observed in positive samples and by the lack of amplification in samples of oysters infected by closely related parasites, including Bonamia exitiosa. A calibration curve using a cloned template was defined to estimate copy number. The assay had a 6 log- dynamic range, mean inter- and intra-assay variation coefficients of <1% and a minimum detection limit of 50 gene copies per reaction. Using infected oyster samples as templates, the assay was at least 10-fold more sensitive than conventional PCR. The quantitative assay was applied to test 132 oysters, and results were compared with the heart imprint method. There was a strong correlation between both techniques, and the results showed that the real-time PCR assay should be useful for studies of the ecology of B. ostreae and its host–parasite relationship.     

PCR-SBT与IMS-ELISA法在强直性脊柱炎患者HLA-B27检测中的比较

目的 比较聚合酶链反应-直接测序法(polymerase chainreaction sequence-based typing,PCR-SBT)和磁珠酶联免疫法(immunomagnetic separation and enzyme-linked immunosorbent assay,IMS-ELISA)检测人类白细胞抗原B27(human leukocyte antigen B27,HLA-B27)在强直性脊柱炎(ankylosing spondylitis,AS)临床诊断中的价值。方法 应用PCR-SBT法和IMS-ELISA法对120例疑似AS患者外周血进行HLA-B27检测。以SPSS17.0软件的配对χ²检验和受试者工作特征曲线下面积对两种方法检测HLA-B27在AS诊断中的价值进行评价。结果 120例疑似AS患者中,PCR-SBT和IMS-ELISA法HLA-B27检测阳性率分别为45.83%(55/120)和37.50%(45/120)。两种方法检测HLA-B27差异有统计学意义(χ²=59.455,P=0.000)。PCR-SBT法敏感度和特异度分别为96.36%和96.92%; IMS-ELISA法的敏感度和特异度分别为69.09%和89.23%。两者的AUC分别为0.966和0.792。结论与IMS-ELISA法相比,在AS的临床诊断中PCR-SBT法检测HLA-B27的敏感度和特异度更高,方法更优。     

Simultaneous detection of duck circovirus and novel goose parvovirus via SYBR green I-based duplex real-time polymerase chain reaction analysis

Beak atrophy and dwarfism syndrome (BADS) is commonly caused by co-infection with duck circovirus (DuCV) and novel goose parvovirus (NGPV). Therefore, concurrent detection of both viruses is important for monitoring and limiting BADS, although such a diagnostic test has not been reported. In this study, we developed a duplex, SYBR Green I-based real-time polymerase chain reaction (PCR) assay to enable the simultaneous detection of DuCV and NGPV. The assay readily distinguished between the two viruses, based on their different melting temperatures (Tm), where the Tm for DuCV was 80 °C and that for NGPV was 84.5 °C. Other non-target duck viruses that were tested did not show melting peaks. The detection limit of the duplex assay was 10¹ copies/μL for both viruses. This method exhibited high repeatability and reproducibility, and both the inter-assay and intra-assay variation coefficients were <1.6%. Thirty-one fecal samples were collected for clinical testing using real-time PCR analysis, and the results were confirmed using sequencing. The rate of co-infection was 6.5%, which was consistent with the sequencing results. This duplex real-time PCR assay offers advantages over other tests, such as rapid, sensitive, specific, and reliable detection of both viruses in a single sample, which enables the quantitative detection of DuCV and NGPV in clinical samples. Using this test may be instrumental in reducing the incidence of BADS and the associated economic losses in the duck and goose industries.     

Establishment of a duplex SYBR green I-based real-time polymerase chain reaction assay for the rapid detection of canine circovirus and canine astrovirus

The similar clinical characteristics of canine circovirus (CaCV) and canine astrovirus (CaAstV) infections and high frequency of co-infection make diagnosis difficult. In this study, a duplex SYBR Green I-based real-time polymerase chain reaction (PCR) assay was established for the rapid, simultaneous detection of CaCV and CaAstV. Two pairs of specific primers were designed based on the Rep gene of CaCV and the Cap gene of CaAstV. By using the real-time PCR assay method, the two viruses can be distinguished by the difference in melting temperatures, 79 °C and 86 °C for CaCV and CaAstV, respectively. This assay had high specificity, showing no cross-reaction with other common canine viruses, as well as high sensitivity, with minimum detection limits of 9.25 × 10¹ copies/μL and 6.15 × 10¹ copies/μL for CaCV and CaAstV, respectively. Based on the mean coefficient of variation, the method had good reproducibility and reliability. In a clinical test of 57 fecal samples, the rates of positive detection by real-time PCR were 14.04% (8/57) and 12.28% (7/57) for CaCV and CaAstV, respectively, and the rate of co-infection was 8.77% (5/57). In conclusion, the newly established duplex SYBR Green I-based real-time PCR assay is sensitive, specific, reliable, and rapid and is an effective tool for the detection of co-infections with CaCV and CaAstV.     

Application of a loop-mediated isothermal amplification method for the detection of pathogenic Leptospira

Leptospirosis is an emerging infectious disease, which is considered to be the most widespread zoonotic disease in the world. There are more than 230 known serovars in the genus Leptospira. A loop-mediated isothermal amplification (LAMP) assay for the rapid detection of pathogenic Leptospira spp. was developed and evaluated through amplification of the lipL41 gene coding for the outer membrane protein LipL41. The LAMP assay did not rely on the isolation and culture of leptospires, and no cross-reactivity was observed with other bacterial species. A SYBR Green I-based LAMP assay was also carried out for the real-time detection of DNA amplification. The lower detection limit of the LAMP assay was approximately 100 copies, which was the same as the polymerase chain reaction (PCR) and real-time PCR assays. The accuracy of the LAMP reaction was confirmed by restriction endonuclease analysis of the amplified product. The LAMP assay is easy to perform and inexpensive, and so may be applied in the rapid and specific diagnosis of Leptospira.     

A real-time PCR assay for detection of emerging infectious Elizabethkingia miricola

Elizabethkingia miricola, a Gram-negative bacillus, is emerging as a life-threatening pathogen in both humans and animals. However, no specific and rapid diagnostic method exists to detect E. miricola. Here, we established a real-time PCR assay for the rapid, sensitive, and specific detection of E. miricola with a wide dynamic range of 10⁸ copies/μL to 10² copies/μL. The detection limit of the real-time assay was 145 copies/μL, which was 100 times more sensitive than conventional PCR. All clinical isolates E. miricola from different host species yield very close Tm (80.25 ± 0.25 °C). Additionally, no cross-reaction or false positives were observed in the assay for non-target bacterial species. The performance of this assay was primarily assessed by testing frog tissue samples. Overall, our study provided a real-time PCR assay, which is a rapid, sensitive, and specific diagnostic method that could be used for early diagnosis and epidemiological investigation of E. miricola.     

Duplex TaqMan real-time PCR assay for simultaneous detection and quantification of Anaplasma capra and Anaplasma phagocytophilum infection

Anaplasma capra and A. phagocytophilum, two species of the family Anaplasmataceae, are zoonotic tick-borne obligate intracellular bacteria affecting wild and domestic ruminants, dogs, cats, horses and humans. A. capra and A. phagocytophilum infections have been steadily increasing in both number and geographic distribution, and the accurate diagnosis of these infections is challenging. This study aimed to develop a rapid, sensitive and reliable duplex real-time PCR assay for the specific detection and differentiation of these Anaplasma species.We designed primers and probes against the conserved regions of A. capra groEL and A. phagocytophilum 16S rRNA genes. A range of PCR-related parameters were evaluated such as the dosage of primers and probes, and annealing temperature. The specificity, sensitivity and repeatability of this assay were evaluated. Assay performance was further evaluated using samples collected from 124 goats in four regions of Henan, China. This set of samples was also tested using conventional PCR under conditions previously described.The developed duplex real-time PCR assay allowed the simultaneous detection of A. capra and A. phagocytophilum in a reasonably short time at levels as small as 10² copies/μL, respectively, with optimal specificity and reproducibility. In addition, this duplex real-time PCR assay is the first DNA-based method designed to detect A. capra and A. phagocytophilum, and will be valuable for timely diagnosis and treatment of these infections.     

TaqMan-MGB探针实时荧光定量-聚合酶链反应检测肺炎支原体方法的建立

目的 建立敏感、特异的TaqMan-MGB探针实时荧光定量-聚合酶链反应(real-time PCR)快速检测方法,为临床标本中肺炎支原体快速检测提供技术支持。方法 选取肺炎支原体重复序列RepMP23中保守区域设计、合成特异性扩增引物和TaqMan-MGB探针,建立并优化real-time PCR检测方法。对优化后的方法使用标准浓度核酸进行扩增效率、灵敏度及特异度评价,并与已报道的肺炎支原体荧光PCR方法进行比较。结果 本研究建立的TaqMan-MGB探针荧光PCR方法对肺炎支原体的检测限为0.2 cfu,比普通TaqMan real-time PCR检测限(3～5 cfu)提高了一个数量级。其检测标准曲线的循环阈值(Ct) 与模板拷贝数呈良好的线性关系(R2=0.999)。用该方法扩增23种呼吸道常见病原菌染色体及人类染色体,结果均为阴性,特异度为100%。结论 TaqMan-MGB探针real-time PCR方法可快速、灵敏、特异地检测肺炎支原体,有很好的应用前景与价值。     

Diagnostic PCR: Comparative sensitivity of four probe chemistries

Three probe chemistries: locked nucleic acid (LNA), minor groove binder (MGB) and Scorpion were compared with a TaqMan probe in a validated real-time PCR assay for detection of food-borne thermotolerant Campylobacter. The LNA probe produced significantly lower Ct-values and a higher proportion of positive PCR responses analyzing less than 150 DNA copies than the TaqMan probe. Choice of probe chemistry clearly has an impact on the sensitivity of PCR assays, and should be considered in an optimization strategy.