Biological and molecular characterization of tomato brown rugose fruit virus and development of quadruplex RT-PCR detection

Tomato brown rugose fruit virus(ToBRFV) is a novel tobamovirus firstly reported in 2015 and poses a severe threat to the tomato industry. So far, it has spread to 10 countries in America, Asia, and Europe. In 2019, ToBRFV was identified in Shandong Province(ToBRFV-SD), China. In this study, it was shown that ToBRFV-SD induced mild to severe mosaic and blistering on leaves, necrosis on sepals and pedicles, and deformation, yellow spots, and brown rugose necrotic lesions on fruits. ToBRFV-SD induced distinct symptoms on plants of tomato, Capsicum annumm, and Nicotiana benthamiana, and caused latent infection on plants of Solanum tuberosum, Solanum melongena, and N. tabacum cv. Zhongyan 102. All the 50 tomato cultivars tested were highly sensitive to ToBRFV-SD. The complete genomic sequence of ToBRFV-SD shared the highest nucleotide and amino acid identities with isolate IL from Israel. In the phylogenetic tree constructed with the complete genomic sequence, all the ToBRFV isolates were clustered together and formed a sister branch with tobacco mosaic virus(TMV). Furthermore, a quadruplex RT-PCR system was developed that could differentiate ToBRFV from other economically important viruses affecting tomatoes, such as TMV, tomato mosaic virus, and tomato spotted wilt virus. The findings of this study enhance our understanding of the biological and molecular characteristics of ToBRFV and provide an efficient and effective detection method for multiple infections, which is helpful in the management of ToBRFV.

Real-time RT-PCR Assay for the detection of Tahyna Virus

A real-time RT-PCR （RT-qPCR） assay for the detection of Tahyna virus was developed to monitor Tahyna virus infection in field-collected vector mosquito samples. The targets selected for the assay were S segment sequences encoding the nucleocapsid protein from the Tahyna virus. Primers and probes were selected in conserved regions by aligning genetic sequences from various Tahyna virus strains available from GenBank. The sensitivity of the RT-qPCR approach was compared to that of a standard plaque assay in BHK cells. RT-qPCR assay can detect 4.8 PFU of titrated Tahyna virus. Assay specificities were determined by testing a battery of arboviruses, including representative strains of Tahyna virus and other arthropod-borne viruses from China. Seven strains of Tahyna virus were confirmed as positive; the other seven species of arboviruses could not be detected by RT-qPCR. Additionally, the assay was used to detect Tahyna viral RNA in pooled mosquito samples. The RT-qPCR assay detected Tahyna virus in a sensitive, specific, and rapid manner; these findings support the use of the assay in viral surveillance.

Detection of Citrus yellow vein clearing virus by Quantitative Real-time RT-PCR

To develop a rapid and reliable detection method for Citrus yellow vein clearing virus(CYVCV), a quantitative real-time reverse transcriptionpolymerase chain reaction(q RT-PCR) system based on SYBR Green I was established by using a pair of specific primers designed from its conserved coat protein gene. The sensitivity, specificity, and applicability of the system were evaluated accordingly. The results showed that amplicons were produced from CYVCV isolates, whereas no amplicons from non-CYVCV citrus virus samples, including Citrus tristeza virus(CTV) and Citrus tatter leaf virus(CTLV), were obtained. The sensitivity of the q RT-PCR was 100-fold higher than that of conventional RT-PCR. An excellent linear correlation(R2= 0.999) was obtained from two standard curves of c RNA, and the amplification efficiency was 102%. The data from field citrus samples detection showed that the q RT-PCR system could be used in determining the concentration of CYVCV in different citrus species.

Development of a multiplex one-step real-time RT-PCR assay for the simultaneous detection of eight viruses associated with febrile rash illnesses

Fever and rash illnesses(FRIs)are a series of common diseaseswith fever and rashes as clinicalmanifestations,most of which are caused by viral infection.The rashes of FRIs are generally nonspecific;therefore it is difficult to identify FRIassociated viruses solely based on clinical symptoms.To achieve rapid and accurate identification of FRI pathogens,a multiplex one-step real-time reverse transcription-polymerase chain reaction(RT-PCR)assay was developed and evaluated in this study.Primers and probes were selected for the detection of measles virus(MeV),rubella virus(RV),human enterovirus(EV),varicella-zoster virus(VZV),dengue virus(DENV),human parvovirus B19(B19),Epstein-Barr virus(EBV),and human herpes virus 6(HHV-6),which cover the most common pathogenic viruses of FRIs.Detection of the eight FRI-associated viruses,which was divided into two groups/tubes,was simultaneously performed under universal optimized reaction conditions in multiplex one-step real-time RT-PCR assay.The multiplex realtime RT-PCR showed high sensitivity and specificity in detecting the eight FRI-associated viruses.The limits of detection(LODs)for the eight viruses were in the range of 47–177 copies/reaction,and no cross reactions for the eight FRIassociated viruses were found in the multiplex assay.In addition,the results of the multiplex real-time RT-PCR assay were consistent with the results of a monoplex real-time RT-PCR assay and sequencing for clinical specimens obtained from FRI patients.With its advantages of high efficiency and rapid and accurate diagnosis,multiplex real-time RT-PCR was very feasible for the early diagnosis of FRI pathogenic viruses and would be of great help for the proper treatment,monitoring,and initiation of preventive measures for FRI cases.

A quantitative RT-PCR assay for rapid detection of Eurasianlineage H10 subtype influenza A virus

Dear Editor,Influenza A viruses(IAVs)are single-stranded,negative sense RNA viruses.IAV subtype is determined on the basis of the viral surface glycoproteins,hemagglutinin(HA),and neuraminidase(NA).To date,18 HA and 11NA subtypes have been reported(Tong et al.,2012).

A sensitive SYBR Green RT-qPCR method for grapevine virus E and its application for virus detection in different grapevine sample types

To develop a rapid and high-sensitivity method for detection of grapevine virus E(GVE),a SYBR Green based real-time fluorescence quantitative RT-PCR method(RT-qPCR)was established.This method could be used to detect GVE specifically,and the sensitivity was about 100 times greater than conventional RT-PCR.An excellent linear correlation(R=0.997)and a high amplification efficiency(E=97.5%)were obtained from the standard curve of this method.Reproducibility tests revealed that the coefficients of variation in the intra-and inter-assay results were 0.31-1.03%and 0.82--262%,respectively,indicating a good reproduiblity.The RT-qPCR method could be used to detect GVE in a wide range of grapevine sample types.The detection rates of RT-qPCR for nearly all sample types from different positions and seasons were higher than conventional RT-PCR.The detection rates in spring,summer,autumn and winter increased gradually.Samples in autumn and winter were best for detection,and the detection rates of most samples were 80-100%,which were 10 to 40%higher than conventional RT-PCR.In general,old petioles and branches were the best tissues for GVE detection.The detection rates of these samples in each season were all 100%,which were 20 to 40%higher than conventional RT-PCR.The second highest rates were in the old leaf,with detection rates for RT-qPCR of 80-100%in all seasons,which were 20 to 40%higher than conventional RT-PCR.GVE could be difficultly detected in young leaves by conventional RT-PCR,and the detection rates were only 0-50%,while by RT-qPCR the rates could increase to 0--80%.A total of 33 out of 363 samples(belonging to 68 cultivars)from 20 regions in China were detected to be positive by RT-qPCR(9.1%),which was more than twice the rate of the conventional RT-PCR(3.9%).

A Pair of Novel Primers for Universal Detection of the NS1 Gene from Various Bluetongue Virus Serotypes

Twenty five serotypes of Bluetongue virus (BTV) have been identified worldwide. Rapid and reliable methods of virus universal detection are essential for fighting against bluetongue (BT). We have therefore developed and evaluated a pair of primers which can detect various serotypes of BTV by RT-PCR. Analysis of the viral protein 7 (VP7) and the non-structural protein (NS1) gene from different serotypes of BTV by DNAstar showed that the 5' end of the NS1 gene is the most conserved region. The primer pairs (P1 and P2) were designed based on the highly conserved region of NS1. The novel primers were evaluated by detecting BTV serotypes 1, 3, 5, 8, 10, 11, 21 and 22. The specificity of the primers was estimated by comparing to gene sequences of viruses published in GenBank, and further assessed by detecting BTV serotype 1-12 and Epizootic hemorrhagic disease virus (EHDV) serotype 1-4. The sensitivity and repeatability of PCR with the novel primers were evaluated by successfully detecting the recombinant plasmid pGEM-T121 containing the diagnosed nucleotide sequence. Our results suggest that these unique primers can be used in high throughout and universal detection of the NS1 gene from various BTV serotypes.

猪血凝性脑脊髓炎病毒RT-PCR方法的建立及初步应用

为了建立快速检测猪血凝性脑脊髓炎病毒(HEV)的RT-PCR方法,根据GenBank中HEV的HE基因和S基因设计了1对引物,在优化RT-PCR反应条件的基础上,成功的扩增出323bp的特异性条带。检测与HEV亲缘性较高的牛冠状病毒及猪的伪狂犬病毒均为阴性,最低可以检测到10个TCID50/100μl的病毒,说明该方法的有较好的特异性和敏感性。用此RT-PCR方法对感染HEV的小鼠和猪进行检测,结果能从发病动物的多种组织中检测到病原,其中以脑组织的检出率最高。因此,临床疑似病例检测时以脑组织为最佳检测样本。

猪血凝性脑脊髓炎病毒实时荧光RT-PCR检测方法的建立与应用

为建立一种快速、准确、常规的猪血凝性脑脊髓炎病毒(porcine hemagglutinating encephalomyelitis virus,PHEV)检测方法,根据PHEV N蛋白基因序列,设计1对引物和1条探针,建立了PHEV实时荧光RT-PCR检测方法。该方法特异性好,与猪繁殖与呼吸综合征病毒(PRRSV)、猪伪狂犬病病毒(PRV)、猪流行性腹泻病毒(PEDV)、猪传染性胃肠炎病毒(TGEV)、猪瘟病毒(CSFV)和猪圆环病毒2型(PCV2)均无交叉反应;用阳性质粒Puc57-PHEVn评估其敏感性,发现检测下限达10-6 ng/μL(224拷贝/μL)。采集233份发病猪组织样品进行临床检测,发现该方法与巢式RT-PCR的符合率达98.3%,准确筛查出巢式RT-PCR并测序阳性的样品14份,且检出率高于巢式RT-PCR。结果表明,本方法敏感、特异,可用于PHEV临床样品的检测。

猪血凝性脑脊髓炎病毒N蛋白单克隆抗体制备及表位鉴定

为制备猪血凝性脑脊髓炎病毒(porcine hemagglutinating encephalomyelitis virus, PHEV)N蛋白的单克隆抗体,本研究构建了pET-32a-N重组质粒,原核表达并纯化重组N蛋白,免疫BALB/c小鼠,细胞融合后利用间接ELISA进行筛选,获得了3株稳定分泌的阳性杂交瘤细胞株,分别命名为2C3、4F3、5C6。Western blot与间接免疫荧光试验表明,3株单抗均能与293T细胞中表达的N蛋白产生特异性反应。经测定,3株单抗的效价均为1×10^(6),重链类型均为IgG1,轻链类型均为κ。利用一系列表达的部分重叠的N截短蛋白片段,经Western blot鉴定单抗所识别的抗原表位,结果显示,^(267)KPRQK^(271)为单抗2C3、4F3、5C6所识别的表位。本研究为PHEV临床检测方法的建立和表位疫苗的研发奠定了基础。

禽脑脊髓炎病毒Luminex xTAG检测方法的建立

为了建立一种灵敏快速检测禽脑脊髓炎病毒(AEV)的Luminex xTAG技术方法,本试验针对AEV高度保守的VP 1基因设计了1对特异性引物,在上游引物的5′端通过Spacer18间隔添加Tag序列,下游引物的5′端标记生物素,进行反转录-聚合酶链式反应(RT-PCR)扩增,构建质粒标准品,通过优化反应体系建立Luminex xTAG检测方法。用所建立的Luminex xTAG方法进行特异性、敏感性和重复性试验,并与SYBR Green I实时荧光定量RT-PCR方法同时对45份脑组织临床样品进行检测。结果显示,所建立AEV Luminex xTAG检测方法与传染性法氏囊病毒、禽传染性贫血病病毒、新城疫病毒、禽流感病毒、传染性喉气管炎病毒、禽白血病病毒、马立克病毒和禽传染性支气管炎病毒无交叉反应;灵敏度可达1×10^(2)copies/μL;批内和批间重复性试验的变异系数均小于4.0%;对45份临床样品的Luminex xTAG检测结果与SYBR Green I实时荧光定量RT-PCR检测结果一致。结果表明,所建立的AEV Luminex xTAG检测方法特异性好、灵敏度高、重复性和稳定性好,可用于AEV的快速检测。

猪血凝性脑脊髓炎病毒抗体的调查

应用血凝和血凝抑制试验检测了从吉林省部分地区采集的猪血清中血凝性脑脊髓炎病毒(HEV)抗体。结果,212份样品中有94份呈现HEV抗体阳性反应,阳性率高达44.3%。被采集血清的猪未表现临床症状,说明该地区的猪群中存在HEV隐性感染。

血凝性脑脊髓炎病毒血凝抑制试验方法的研究

为检测某猪场的猪感染血凝性脑脊髓炎病毒的情况,用250 mL/L 的鸡红细胞和200 g/L的高岭土去除非特异性物质,使用4单位抗原及5 mL/L鸡红细胞做HI 试验,发现这些条件较适宜。用此法对其他5 种猪传染病抗血清进行检查,发现均不产生非特异性血清学反应。另外,本试验用滤纸吸附血清与分离血清做HI比较试验,其HI价差异不显著,从而为以后进行血清学调查提供了一种便利的方法。用分离的HEV与日本HEV 67N毒株抗原进行比较,两者的HI价一致。

1株高致病性血凝性脑脊髓炎病毒的分离与鉴定

利用细胞培养方法从临床表现神经症状的死亡仔猪脑组织内分离获得1株病毒,同时对该病毒进行电镜负染观察、昆明种小鼠致病性试验、RT-PCR检测和部分基因测序分析。电镜观察可见细胞培养物中有大量的直径约115 nm的冠状病毒样粒子;接种病毒的小鼠均出现典型的神经症状,死亡率100%;血凝性脑脊髓炎病毒(HEV)特异性引物RT-PCR扩增结果阳性;其S基因序列与GenBank中登录的HEV-67 N相应基因序列的同源性高达99.6%。结果表明,分离的病毒为猪血凝性脑脊髓炎病毒,分离株暂命名为HEV-CC-2007。

辽宁省猪血凝性脑脊髓炎流行病学调查与分析

从辽宁省各地区采集猪血清样本和HEV感染疑似病例脑组织样品,进行HEV抗体和病原学检测,结果910份样品中有451份呈现HEV抗体阳性反应,阳性率为49.6%;23份疑似病料检测HEV阳性率为73.91%,多与PRRSV等病原混和感染。依据临床样本资料和检测结果综合分析表明,辽宁省各地区普遍存在HEV感染,主要为隐性感染,发病猪均为45日龄以下仔猪。通过检测猪血清HEV抗体效价,可以判断HEV感染状态,为养猪场制定相应的防制措施提供依据。

猪血凝性脑脊髓炎病毒的血清学调查

应用血凝和血凝抑制试验检测了从辽宁省部分地区采集的猪血清中血凝性脑脊髓炎病毒(HEV)的抗体滴度。结果表明,368份血清样品中,有162份呈抗体阳性反应,阳性率高达44.0%。被采集血清的猪未表现出临床症状,说明该地区存在血凝性脑脊髓炎病毒的隐性感染。

猪血凝性脑脊髓炎病毒HE基因的克隆及真核表达

应用特异性引物,从猪血凝性脑脊髓炎病毒(HEV)中扩增出HE蛋白基因,PCR产物纯化后克隆入pGEM-T载体,得到重组质粒pTHE。用EcoRⅠ和NotⅠ双酶切pTHE,回收目的基因HE片段并将其定向克隆到pPICZαA中,构建重组质粒pPICZαA HE。用BstXⅠ酶切pPICZαA HE使其线性化,并电击转化至感受态毕赤酵母细胞GS115。PCR法鉴定阳性重组子,用1%甲醇诱导表达后,进行SDS-PAGE及Western blot分析。结果在酵母菌培养基上清中检测到相对分子量为43 kD的重组蛋白,且该重组蛋白可与HEV多克隆抗体发生特异性血清学反应,表明HEV的HE蛋白片段在Pichia Pastoris中获得成功表达。

猪血凝性脑脊髓炎病毒不同佐剂灭活疫苗免疫BALB/c小鼠的比较试验

用血凝/血凝抑制试验(HA/HI)检测自制的猪血凝性脑脊髓炎病毒(HEV)氢氧化铝胶灭活苗和蜂胶佐剂灭活苗免疫BALB/c小鼠后的抗体效价,依据小鼠抗体效价比较不同免疫佐剂的效果。结果表明,用氢氧化铝胶佐剂配制的疫苗可刺激接种动物产生快速免疫应答反应,抗体产生效价高、维持时间长,其效果优于其它佐剂,有望成为HEV灭活疫苗的候选佐剂。

猪血凝性脑脊髓炎病毒S1蛋白基因在毕赤酵母中的表达

应用特异性引物从猪血凝性脑脊髓炎病毒(HEV)中扩增出S1蛋白基因,PCR产物纯化后克隆入pGEM-T载体中,得到重组质粒pTS1。用EcoRI和Not I双酶切pTS1,回收目的基因S1片段将其定向克隆到pPICZαA中,构建重组质粒pPICZαAS1。用BstXI酶切pPICZαAS1使其线性化,并电转至感受态毕赤酵母细胞GS115。PCR法鉴定阳性重组子,用1%甲醇诱导表达后,进行SDS-PAGE及Western blot分析。结果显示,在酵母菌培养基上清中检测到相对分子质量为73000的重组蛋白,且该重组蛋白可与HEV多克隆抗体发生特异性血清学反应,表明HEV的S1蛋白片段在毕赤酵母中获得成功表达。

小鼠脑脊髓炎病毒自然感染调查以及人工感染小鼠试验

目的了解小鼠脑脊髓炎病毒(TMEV)自然感染情况,探究人工感染TMEV小鼠体内各脏器组织中病毒分布及血清抗体变化。方法采用酶联免疫吸附试验(ELISA)和荧光定量RT-PCR(qRT-PCR)检测方法对2010年~2015年广东地区采集的SPF级小鼠、开放环境饲养的小鼠以及野生褐家鼠临床样本进行TMEV检测。36只ICR小鼠经脑内接种TMEV BeAn病毒,每天观察动物的临床症状,在接种第0、3、7、10、17、21、31、39、46天每个时间点分别对3只动物安乐死,剖检并取血清和组织脏器样本进行TMEV检测。结果 SPF级小鼠TMEV抗体阳性率为5.29%(n=2834),核酸阳性率为27.27%(n=457);开放环境饲养的小鼠的抗体和核酸阳性率分别为71.95%(n=82)和53.66%(n=82);野生褐家鼠中核酸阳性率为25.93%(n=27)。TMEV阳性小鼠中仅有两只小鼠表现有明显的临床症状。盲肠内容物、粪便和脑是qRT-PCR检测的最佳选择样本。ICR小鼠脑内接种TMEV BeAn病毒后第3 d可在脑、心脏、肝脏、肺脏和胃中检测到病毒核酸,脾脏、肾脏和盲肠中未检测到病毒核酸。肝脏、心脏、肺脏和胃中的病毒在接种后第10天已完全清除,脑中的病毒一直持续存在到第46天试验结束。小鼠感染后第7天可以检测到抗体,随后抗体水平逐渐升高,接种后17 d抗体阳性率达100%,并一直到46 d都可以维持较高的抗体水平。人工感染小鼠呈隐性感染,临床上并未表现明显症状和眼观病理变化。结论广东地区实验小鼠和野生褐家鼠均存在TMEV感染,且感染率较高。小鼠接种TMEV BeAn毒株后呈隐性感染,感染小鼠第7天可以产生抗体且持续存在。病毒在感染小鼠肝脏、心脏、肺脏和胃中短时间存在,而在脑中长期存在。qRT-PCR与ELISA两种检测方法具有较好的一致性,qRT-PCR检测方法可作为实验动物国家标准的有力补充。