多重PCR种特异性检测恶性疟原虫和间日疟原虫方法的建立

目的建立恶性疟原虫和间日疟原虫种特异性检测的多蕈PCR方法,用于疟疾的检测和诊断.方法根据疟原虫18S核糖体小亚基ssRNA的基因序列设计合成8对11条引物,通过对恶性疟、间日疟患者及健康对照者血样的DNA进行扩增,选择出敏感性和特异性最佳的引物用于建立多重PCR方法,并用梯度变化的方法分别对引物浓度、复性温度、延伸温度和循环次数等反应参数进行比较分析,优化PCR反应条件.利用优化后的多重PCR埘采自云南和上海的139份疟疾患者血样和32份非疟疾患者血样进行检测,以镜检方法为金标准,分析多重PCR方法检测患者血样的敏感性和特异性.结果从8对11条引物中优选出2对共3条引物用于建立多重PCR.利用这3条引物进行多重PCR,一次反应即可完成对恶性疟原虫和间日疟原虫的种特异性鉴定.对疟疾和非疟疾患者血样检测结果显示,该方法检测患者血样的敏感性为97.8%,特异性为100%.结论多重PCR方法敏感、特异、可进行批量检测,适用于对人群的疟疾监测和疑似疟疾病例的诊断,并能鉴定恶性疟原虫和间日疟原虫虫种.     

多重PCR快速检测恶性疟和间日疟的研究

目的 建立一种简便快速、能同时检测恶性疟和间日疟的核酸检测方法。方法 针对两种疟原虫18S rRNA基因设计2对(3条引物),优化引物浓度与退火温度,建立可扩增出两种疟原虫基因片段的多重PCR。并进行最低检测限确定和临床标本检测,以镜检法为金标准分析灵敏度和特异度等指标。结果 该方法可扩增出431 bp(恶性疟原虫)和341 bp(间日疟原虫)基因片段,最低检测限为10²copies/反应,检测临床标本的结果与镜检法无差别(P＞0.05),敏感度为93.55%,特异度为70.83%,阳性预测值为89.23%,阴性预测值为80.95%。结论 所建立的多重PCR方法可快速检测疟疾感染并鉴别分型,灵敏度高,值得推广。     

FY*X real-time polymerase chain reaction with melting curve analysis associated with a complete one-step real-time FY genotyping

BACKGROUND AND OBJECTIVES: The Duffy (FY) blood group system is controlled by four major alleles: FY*A and FY*B, the Caucasian common alleles, encoding Fy(a) and Fy(b) antigens; FY*X allele responsible for a poorly expressed Fy(b) antigen, and FY*Fy a silent predominant allele among Black population. Despite the recent development of a real-time fluorescent polymerase chain reaction (PCR) method for FY genotyping FY*X genotyping has not been described by this method. This study focused on the real-time FY*X genotyping development associated with a complete, one-step real-time FY genotyping, based on fluorescence resonance energy transfer (FRET) technology. MATERIALS AND METHODS: Seventy-two blood samples from Fy(a+b-) Caucasian blood donors were studied by real-time PCR only. Forty-seven Caucasian and Black individual blood samples, referred to our laboratory, were studied by PCR-RFLP and real-time PCR. For each individual, the result of the genotype was compared to the known phenotype. RESULTS: The FY*X allele frequency calculated in an Fy(a+b-) Caucasian blood donors population was 0.014. With the Caucasian and Black patient samples we found a complete correlation between PCR-RFLP and the real-time PCR method whatever the alleles combination tested. When the known phenotype was not correlated to FY*X genotype, the presence of the Fy(b) antigen was always confirmed by adsorption-elution. CONCLUSION: The real-time technology method is rapid and accurate for FY genotyping. From now, we are able to detect the FY*X allele in all the alleles combinations studied. Regarding its significant frequency, the detection of the FY*X allele is useful for the correct typing of blood donors and recipients considering the therapeutic use of blood units and the preparation of test red blood cells for antibody screening.     

Duffy blood group genotypes among malaria Plasmodium vivax patients of Baoulch population in southeastern Iran

Objective:To determine the distribution of Duffy blood group genotypes in Balouch population as a major ethnic group that living in a sub-tropical area in south East of Iran.Methods:In this study,the Duffy blood group FY phenolypes were determined using indireet anti-globulin technique and also genotype by PCR-RFLP in 160 vivax malaria patients and 160 control individuals.Results:The results showed that the most common Duffy geitolype was FYA/FYB(46.6%)followed by FYA/FYA(15.3%),FYA/FYO(14.4%),FYB/FYO(11.9%,),FYB/FYB(10%)and FYO/FYO(1.9%).In case individuals,frequency of FY A.FYB and FYO alleles were 0.471,0.431and 0.097,respectively compaired to 0.444,0.353 and 0.203,respectively in control(non-infected)group.Conclusions:This data provide evidence that individuals with the FYA/FYB genotype have higher susceptibility to malaria and there are significant associations between Duffy blood group variants and susceptibility or resistance to vivax malaria.     

Structure-function analysis of the extracellular domains of the Duffy antigen/receptor for chemokines: characterization of antibody and chemokine binding sites

The Duffy antigen/receptor for chemokines (DARC), a seven-transmembrane glycoprotein carrying the Duffy (Fy) blood group, acts as a widely expressed promiscuous chemokine receptor. In a structure-function study, we analysed the binding of chemokines and anti-Fy monoclonal antibodies (mAbs) to K562 cells expressing 39 mutant forms of DARC with alanine substitutions spread out on the four extracellular domains (ECDs). Using synthetic peptides, we defined previously the Fy6 epitope (22-FEDVW-26), and we characterized the Fya epitope as the linear sequence 41-YGANLE-46. In agreement with these results, mutations of F22-E23, V25 and Y41, G42, N44, L45 on ECD1 abolished the binding of anti-Fy6 and anti-Fya mAbs to K562 cells respectively, Anti-Fy3 binding was abolished by D58-D59 (ECD1), R124 (ECD2), D263 and D283 (ECD4) substitutions. Mutations of C51 (ECD1), C129 (ECD2), C195 (ECD3) and C276 (ECD4 severely reduced anti-Fy3 and CXC-chemokine ligand 8 (CXCL-8) binding. CXCL-8 binding was also abrogated by mutations of F22-E23, P50 (ECD1) and D263, R267, D283 (ECD4). These results defined the Fya epitope and suggested that (1) two disulphide bridges are involved in the creation of an active chemokine binding pocket; (2) a limited number of amino acids in ECDs 1-4 participate in CXCL-8 binding; and (3) Fy3 is a conformation-dependent epitope involving all ECDs. We also showed that N-glycosylation of DARC occurred on N16SS and did not influence antibody and chemokine binding.     

我国分离株间日疟原虫与红细胞黏附关键区DBPⅡ区基因多态性分析

目的　了解我国季节流行区间日疟原虫红内期候选抗原DBP基因多态性特点。方法　疟原虫基因组DNA提取。PCR扩增DBPRⅡ区基因片段,序列直接测序分析。结果　成功扩增18个DBPRⅡ区基因片段,发现9个核苷酸突变,产生4种基因型,导致9个氨基酸置换。其中G115 1-A116 9-A12 70为主导基因型,G384 -H390 -I4 2 4是主导氨基酸型。结论　我国季节流行区分离株DBP基因突变位点完全含盖在以往报道的位点中,同时表明我国分离株DBP基因突变位点有限,提示我国分离株红内期候选抗原DBP蛋白功能相对保守。     

Evaluation of the Abbott Cell-Dyn 4000 hematology analyzer for detection and therapeutic monitoring of Plasmodium vivax in the Republic of Korea

The Cell-Dyn 4000 automated hematology analyzer (CD4000) has the ability to detect malaria patients, but it remained unclear whether it could detect persistent malaria post-treatment. To investigate this, we used the CD4000 to evaluate 68 Korean patients with Plasmodium vivax malaria, and control groups of 50 patients with fever and 50 asymptomatic patients. The results from the instrument-generated scatter plot (derived by laser light depolarization) were compared with microscopy results. During the initial diagnosis, the sensitivity of the CD4000 in detecting malaria was 91.2%. On day 3 of follow-up, the CD4000 results matched those from microscopy by 96.7%. Malaria was not detected by either method beyond 14 days post-presentation. Interestingly, the atypical depolarizing events, which typify the presence of malaria in the analyzer, were highly correlated with the levels of parasitaemia in serially diluted samples of the leucocyte-depleted blood, and the CD4000 detected parasites down to the level of 288 +/- 17.7/microl. Our findings suggest that the phenomenon of atypical light depolarization could be influenced by parasitaemia levels, and be used as a screening method for P. vivax malaria patients, as well as for the therapeutic monitoring.     

Plasmodium vivax Duffy binding protein: baseline antibody responses and parasite polymorphisms in a well‐consolidated settlement of the Amazon Region

Objective  To investigate risk factors associated with the acquisition of antibodies against Plasmodium vivax Duffy binding protein (PvDBP) – a leading malaria vaccine candidate – in a well‐consolidated agricultural settlement of the Brazilian Amazon Region and to determine the sequence diversity of the PvDBP ligand domain (DBP_II) within the local malaria parasite population. Methods  Demographic, epidemiological and clinical data were collected from 541 volunteers using a structured questionnaire. Malaria parasites were detected by conventional microscopy and PCR, and blood collection was used for antibody assays and molecular characterisation of DBP_II. Results  The frequency of malaria infection was 7% (6% for P. vivax and 1% for P. falciparum), with malaria cases clustered near mosquito breeding sites. Nearly 50% of settlers had anti‐PvDBP IgG antibodies, as detected by enzyme‐linked immunosorbent assay (ELISA) with subject’s age being the only strong predictor of seropositivity to PvDBP. Unexpectedly, low levels of DBP_II diversity were found within the local malaria parasites, suggesting the existence of low gene flow between P. vivax populations, probably due to the relative isolation of the studied settlement. Conclusion  The recognition of PvDBP by a significant proportion of the community, associated with low levels of DBP_II diversity among local P. vivax, reinforces the variety of malaria transmission patterns in communities from frontier settlements. Such studies should provide baseline information for antimalarial vaccines now in development.     

套式/多重PCR诊断疟疾的敏感性、特异性和稳定性初探

目的 提高标签引物?鄄套式/多重PCR诊断疟疾的敏感性、特异性与稳定性。 方法 用滤纸法采集非疟疾发热病人血样30份及其他传染病（感冒， 流感， 伤寒， 肝炎等）患者血样20份；抽取恶性疟和间日疟各1例患者血4 m1，进行系列稀释制备不同疟原虫含量的感染血样；健康者血样作对照。用热裂解法制备DNA模板，用线粒体细胞色素氧化酶基因作为靶基因，应用相关软件和网络资源（Primer Premier 5.0, PUBMED, NCBI-BLAST和Mfold服务器）设计和优化标签引物?鄄套式/多重PCR，并用于检测所采集制备的各种血样。 结果 间日疟与恶性疟患者血系列稀释为含 1 000、100、10和1个虫/μl后经标签引物?鄄套式/多重PCR检测，恶性疟和间日疟患者各稀释含虫血样分别在611 bp和255 bp出现1条带，能检测到原虫密度均为1个虫/μl血；非疟疾发热病人血样30份及其他传染病患者血样均为阴性；健康者血样未出现扩增条带，每种血样反复测试3次以上均获得同样结果。 结论 经优化的标签引物-套式/多重PCR在疟疾诊断中具有较高的敏感性、特异性和稳定性。     

Semi-nested, multiplex polymerase chain reaction for detection of human malaria parasites and evidence of Plasmodium vivax infection in Equatorial Guinea

A semi-nested, multiplex polymerase chain reaction (PCR) based on the amplification of the sequences of the 18S small subunit ribosomal RNA (ssrRNA) gene was tested in a field trial in Equatorial Guinea (a hyperendemic focus of malaria in west central Africa). The method uses a primary PCR amplification reaction with a universal reverse primer and two forward primers specific for the genus Plasmodium and to mammals (the mammalian-specific primer was included as a positive control to distinguish uninfected cases from inhibition of the PCR). The second amplification is carried out with the same Plasmodium genus-specific forward primer and four specific reverse primers for each human Plasmodium species. The PCR amplified products are differentiated by fragment size after electrophoresis on a 2% agarose gel. Four villages from three regions of the island of Bioko (Equatorial Guinea) and two suspected Plasmodium vivax-P. ovale infections from the hospital of Malabo were tested by microscopy and PCR. The PCR method showed greater sensitivity and specificity than microscopic examination and confirmed the existence of a focus of P. vivax infections in Equatorial Guinea suspected by microscopic examination. It also provided evidence of several mixed infections, mainly P. falciparum and P. malariae, the two predominant species causing malaria in Equatorial Guinea.     

应用Taq Man荧光PCR定性定量检测炭疽芽孢杆菌

目的　发展一种快速、敏感、特异的检测炭疽芽孢杆菌的方法。方法　应用基于TaqMan荧光探针的实时(real time)PCR技术,针对致病炭疽毒株的两个质粒pXO1、pXO2上的pagA ,cap基因和染色体上的ropB基因设计引物和探针定性、定量检测炭疽芽孢杆菌。构造并应用上述探针的外标对照及pagA的内标对照,采用多重荧光定量PCR技术建立荧光定量方法并发现假阴性;采用UDG抗污染和ROX矫正背景噪音,提高检验能力;用该方法检测炭疽芽孢杆菌疫苗株感染的动物脾脏标本,盲法评价该方法在实际工作的应用。结论　该方法能特异、灵敏、高效地检测炭疽芽孢杆菌,该方法的推广和应用对有效防范炭疽生物恐怖袭击、提高突发事件应对能力、快速诊断具有重要意义。     

Field evaluation of the ICT malaria P.f/P.v immunochromatographic test for diagnosis of Plasmodium falciparum and P.vivax infection in forest villages of Chhindwara, central India

A rapid new immunochromatographic test (ICT malaria P.f/P.v) for diagnosis of Plasmodium falciparum and P.vivax was evaluated against thick blood smears in forest villages of Chhindwara, Madhya Pradesh, where both Plasmodium falciparum and P.vivax are prevalent. 344 symptomatic patients (Gond ethnic tribe) in five villages were screened by field staff of the Malaria Research Centre in October 1999. For P.falciparum, the ICT was 97.5% sensitive and 88% specific, with a positive predictive value (PPV) of 87.6% and a negative predictive value (NPV) of 97.6%. For P.vivax the sensitivity was only 72%, the specificity 99%, with a PPV of 92% and an NPV of 96%. Although a negative test result was inadequate to exclude parasitaemia < or = 300/microl for P.falciparum and < or = 1500/microl for P.vivax, the test is potentially useful in remote areas.     

Short communication: Erythrocyte binding antigen (EBA-175) of Plasmodium falciparum: improved genotype determination by nested polymerase chain reaction

We have designed primers to the conserved region of the erythrocyte binding antigen (EBA)-175 gene which amplify specifically the two alleles by polymerase chain reaction (PCR) and by nested PCR. This approach provides a specific, sensitive and rapid method for genotype determination in a large number of Plasmodium falciparum field isolates.     

A new multiplex real-time polymerase chain reaction assay for the diagnosis of periprosthetic joint infection

Objectives: A new multiplex real-time polymerase chain reaction (PCR) assay was developed to detect methicillin-resistant Staphylococcus (MRS) and to distinguish between gram-positive and gram-negative bacteria. In this study, we validated the sensitivity and specificity of this assay with periprosthetic joint infections (PJIs) and evaluated the utility of PCR for culture-negative PJI.

Methods: Forty-five samples from 23 infectious PJI cases and 106 samples from 64 non-infectious control cases were analyzed by real-time PCR using a LightCycler Nano^® system. Twenty-eight clinical samples, comprising bacteria of known species isolated consecutively in the microbiological laboratory of our hospital, were used to determine the spectrum of bacterial species that could be detected using the new multiplex primers and probes.

Results: The sensitivity and specificity of the MRS- and universal-PCR assays were 92% and 99%, and 91% and 88%, respectively. Twenty-eight species of clinically isolated bacteria were detected using this method and the concordance rate for the identification of gram-positive or gram-negative organisms was 96%. Eight samples were identified as PCR-positive despite a culture-negative result.

Conclusion: This novel multiplex real-time PCR system has acceptable sensitivity and specificity and several advantages; therefore, it has potential use for the diagnosis of PJIs, particularly in culture-negative cases.     

Plasmodium falciparum malaria and the immunogenetics of ABO, HLA, and CD36 (platelet glycoprotein IV)

Plasmodium falciparum malaria has long been a killer of the young, and has selected for polymorphisms affecting not only erythrocytes, but the immunogenetics of three histocompatibility systems: ABO, human leukocyte antigen (HLA), and CD36. The ABO system is important because the original allele, encoding glycosylation with the A sugar, acts as an adhesion ligand with infected red blood cells (iRBC), thereby promoting vasoocclusion. The prevalence of blood group O, which reduces this cytoadhesion, has increased in endemic areas. Other adaptations which could mitigate A-mediated rosetting include weaker A expression and increased soluble A secretion. The role of the HLA system in malaria has been harder to verify. Although HLA-B53 and DRB1*04 may be associated with clinical outcome, HLA studies are challenged by numerous comparisons in this most polymorphic of systems, and confounded by increasingly heterogeneous populations. Certain HLA markers may also reflect linkage artefact with other malaria-relevant polymorphisms. HLA may be less important because the parasite predominantly invades a compartment which does not express HLA. Adhesion of iRBCs is also mediated by CD36, expressed on platelets, monocytes, and microvascular endothelium. CD36 on monocytes is involved in clearing iRBC, while CD36 on platelets and the endothelium may play a role in tissue sequestration. The genetics of CD36 expression are complex, and recent research is fraught with inconsistent results. The solution may lie in examining genotype-phenotype correlations, zygosity effects on differential tissue expression, or other mechanisms altering CD36 tissue expression. Carefully designed prospective studies should bridge the gap between in-vitro observations and clinical outcomes.     

Development of white blood cell fragments, during the preparation and storage of platelet concentrates, as measured by using real-time polymerase chain reaction

BACKGROUND AND OBJECTIVES: White blood cell (WBC) fragments may cause human leucocyte antigen (HLA) immunization in recipients. We investigated the occurrence and production of WBC fragments in platelet concentrates (PCs) and plasma units, during storage and filtration, by using real-time polymerase chain reaction (PCR) and flow cytometry. MATERIALS AND METHODS: To study the occurrence of WBC fragments, 'male' WBCs were spiked into double-filtered 'female' PCs in a concentration series of 0.03-100 WBCs/microl (n = 4 per level). To study the production of WBC fragments, 'male' WBCs were spiked into 'female' plasma units to 4 x 10(9) WBCs/l and stored at room temperature prior to filtration (n = 4 per storage time; t = 0, 24 or 48 h). DNA was measured by both albumin real-time PCR and Y real-time PCR. Intact WBCs were counted by using flow cytometry. The number of WBC fragments was calculated by subtracting cell-free DNA (real-time PCR on supernatant) and intact WBCs (flow cytometry) from the total DNA amount (real-time PCR). RESULTS: Spiking of 'male' WBCs into 'female' PCs showed that the Y real-time PCR is linear and has a reproducible quantitative range down to 0.03 WBC/microl, but that the albumin-PCR, in unspiked samples, revealed a total of 6-10 WBC equivalents/microl (eq/microl). After centrifugation, half of this was observed as cell-free DNA in the supernatant, suggesting that the remaining DNA is derived from WBC fragments. The number of intact WBCs, amount of cell-free DNA and number of WBC fragments after filtration increased significantly when filtration was delayed for up to 48 h, from 0.1 WBC/microl, 1.3 WBC eq/microl and 0.6 WBC eq/microl at t = 0 h to 25 WBC/microl, 38 WBC eq/microl and 57 WBC eq/microl at t = 48 h, respectively. CONCLUSIONS: WBC fragments occur in WBC-reduced PCs and increase when products are stored, prior to filtration, up to levels that are equivalent to the amounts of intact WBCs that induce HLA immunization (i.e. > 5 x 10(6)/unit).     

Enrichment polymerase chain reaction for the detection of Ki-ras mutations: relevance of Taq polymerase error rate, initial DNA copy number, and reaction conditions on the emergence of false-positive mutant bands

Screening for oncogene mutations as a marker for malignancy can be a powerful tool for the early diagnosis of cancer. The enrichment polymerase chain reaction (PCR) is a sensitive method for the detection of low-frequency mutations in small samples. However, false-positive results, caused by methodological errors, may have severe clinical implications. When applied to the detection of Ki-ras mutations in pancreatic secretions, the assay sensitivity is limited to approximately 1:1400. Our investigation of Ki-ras mutations in blood samples from patients with pancreatic carcinoma revealed PCR bands presumably derived from mutant Ki-ras in samples from healthy volunteers, while all blood samples of the patients with pancreatic carcinomas showed a wild-type band pattern. Mathematical modeling of the PCR reaction reveals that the rate of false positive PCR results depends on the initial amount of DNA, the Taq polymerase error rate, the number of PCR reaction cycles, reaction efficiency and the restriction endonuclease chosen. The overall error rate of false positive results of the enrichment PCR can be reduced to the square of the rate of a single-step analysis if repeated amplifications of the same DNA specimen show an identical result. Received: 11 December 1998 / Accepted: 7 January 1999     

Distribution of Diego blood group alleles and identification of four novel mutations on exon 19 of SLC4A1 gene in the Chinese Han population by polymerase chain reaction sequence–based typing

Background The Diego blood group system plays an important role in transfusion medicine. Genotyping of DI1 and DI2 alleles is helpful for the investigation into haemolytic disease of the newborn (HDN) and for the development of rare blood group databases. Here, we set up a polymerase chain reaction sequence–based typing (PCR‐SBT) method for genotyping of Diego blood group alleles. Study Design and Methods Specific primers for exon 19 of the solute carrier family 4, anion exchanger, member1 (SLC4A1) gene were designed, and our PCR‐SBT method was established and optimized for Diego genotyping. A total of 1053 samples from the Chinese Han population and the family members of a rare proband with DI1/DI1 genotype were investigated by the PCR‐SBT method. An allele‐specific primer PCR (PCR‐ASP) was used to verify the reliability of the PCR‐SBT method. Results The frequencies of DI1 and DI2 alleles in the Chinese Han population were 0·0247 and 0·9753, respectively. Six new single nucleotide polymorphisms (SNPs) were found in the sequenced regions of the SLC4A1 gene, and four novel SNPs located in the exon 19, in which one SNP could cause an amino acid alteration of Ala858Ser on erythrocyte anion exchanger protein 1. The genotypes for Diego blood group were identical among 41 selected samples with PCR‐ASP and PCR‐SBT. Conclusion The PCR‐SBT method can be used in Diego genotyping as a substitute of serological technique when the antisera is lacking and was suitable for screening large numbers of donors in rare blood group databases.     

Comparison of direct fecal smear microscopy,culture, and polymerase chain reaction for the detection of Blastocystis sp. in human stool samples

ObjectiveTo compare the sensitivity and specificity of direct fecal smear microscopy, culture, and polymerase chain reaction in the detection of Blastocystis sp. in human stool.MethodsHuman stool samples were collected from a community in San Isidro, Rodriguez, Rizal, Philippines. These samples were subjected to direct fecal smear microscopy, culture and polymerase chain reaction to detect the presence of Blastocystis sp.ResultsOf the 110 stool samples collected, 28 (25%) were detected positive for the presence of Blastocystis sp. by two or more tests. Culture method detected the highest number of Blastocystis-positive stool samples (n=36), followed by PCR of DNA extracted from culture (n=26), PCR of DNA extracted from stool (n=10), and direct fecal smear (n=9). Compared to culture, the sensitivity of the other detection methods were 66.7% for PCR from culture and 19.4% for both PCR from stool and direct fecal smear. Specificity of the methods was high, with PCR from culture and direct fecal smear having 97.3%, while PCR from stool at 95.9%.ConclusionsIn this study, in vitro culture is the best method for detecting Blastocystis sp. in human stool samples.