One-step RT-PCR Assay Research Articles

Quantitative multiplex one-step RT-PCR assay for identification and quantitation of Sabin strains of poliovirus in clinical and environmental specimens

An improved quantitative multiplex one-step RT-PCR (qmosRT-PCR) for simultaneous identification and quantitation of all three serotypes of poliovirus is described. It is based on using serotype-specific primers and fluorescent TaqMan oligonucleotide probes. The assay can be used for high-throughput screening of samples for the presence of poliovirus, poliovirus surveillance and for evaluation of virus shedding by vaccine recipients in clinical trials to assess mucosal immunity. It could replace conventional methods based on cell culture virus isolation followed by serotyping. The assay takes only few hours, and was found to be simple, specific, sensitive and has large quantitative linearity range. In addition, the method could be used as readout in PCR-based poliovirus titration and neutralization assays.

Evaluation of Seegene Allplex Respiratory Panel 1 kit for the detection of influenza virus and human respiratory syncytial virus

BackgroundInfluenza (FLUV) and human respiratory syncytial (HRSV) viruses are etiological agents of respiratory infections that cause a significant morbidity and mortality worldwide. A rapid and accurate diagnosis of these respiratory viruses is essential for an appropriate patient management. Molecular tests are the best detection option due to their high sensitivity and specificity. Seegene’s Allplex™ Respiratory Panel 1 (Allplex RP1) is a real-time one-step RT-PCR assay for the simultaneous detection of FLUAV, FLUBV, HRSV-A and HRSV-B. In addition, it allows the determination of FLUAV subtype (H1, H3 and H1pdm09). ObjectivesThis study aims to evaluate Allplex RP1 as a rapid molecular test for the detection of FLUAV, FLUBV, HRSV-A and HRSV-B viruses. Study designThe Allplex RP1 assay will be compared with other two commercial molecular assays, Prodesse ProFlu+ and ProFAST+ (Hologic, Madison, WI, USA), and GeneXpert Flu/RSV XC (Cepheid, USA). ResultsAllplex RP1, ProFlu+ and GeneXpert tests showed 95%, 91% and 96% of accuracy; and 94%, 88% and 95% of sensitivity, respectively. Moreover, Allplex RP1 showed a FLUAV subtype sensitivity of 91% and 88% for FLUAV-H1pdm09 and FLUAV-H3 respectively, and ProFAST+ assay showed sensitivities of 100% for both targets. The three assays showed a 100% of specificity and PPV, while the NPV were 84%, 73% and 86% for Allplex RP1, Prodesse and GeneXpert, respectively. ConclusionsIn this study, Seegene’s Allplex RP1 assay showed to be highly sensitive, specific, and suitable for detection of FLUV and HRSV, including FLUAV subtyping. In addition, it is also a hands-on-time saving assay due to the automated nucleic acid extraction and PCR setup.

Decreased Km to dNTPs is an essential M-MuLV reverse transcriptase adoption required to perform efficient cDNA synthesis in One-Step RT-PCR assay.

Personalized medicine and advanced diagnostic tools based on RNA analysis are focusing on fast and direct One-Step RT-PCR assays. First strand complementary DNA (cDNA) synthesized by the reverse transcriptase (RT) is exponentially amplified in the end-point or real-time PCR. Even a minor discrepancy in PCR conditions would result in big deviations during the data analysis. Thus, One-Step RT-PCR composition is typically based on the PCR buffer. In this study, we have used compartmentalized ribosome display technique for in vitro evolution of the Moloney Murine Leukemia Virus reverse transcriptase (M-MuLV RT) that would be able to perform efficient full-length cDNA synthesis in PCR buffer optimized for Thermus aquaticus DNA polymerase. The most frequent mutations found in a selected library were analyzed. Aside from the mutations, which switch off RNase H activity of RT and are beneficial for the full-length cDNA synthesis, we have identified several mutations in the active center of the enzyme (Q221R and V223A/M), which result in 4-5-fold decrease of Km for dNTPs (<0.2 mM). The selected mutations are in surprising agreement with the natural evolution process because they transformed the active center from the oncoretroviral M-MuLV RT-type to the lenitiviral enzyme-type. We believe that this was the major and essential phenotypic adjustment required to perform fast and efficient cDNA synthesis in PCR buffer at 0.2-mM concentration of each dNTP.

Development of a one-step RT-PCR assay for detection of pancoronaviruses (α-, β-, γ-, and δ-coronaviruses) using newly designed degenerate primers for porcine and avian `fecal samples

Coronaviruses (CoVs) are critical human and animal pathogens because of their potential to cause severe epidemics of respiratory or enteric diseases. In pigs, the newly emerged porcine deltacoronavirus (PDCoV) and re-emerged porcine epidemic diarrhea virus (PEDV) reported in the US and Asia, as well as the discovery of novel CoVs in wild bats or birds, has necessitated development of improved detection and control measures for these CoVs. Because the previous pancoronavirus (panCoV) RT-PCR established in our laboratory in 2007–2011 did not detect deltacoronaviruses (δ-CoVs) in swine fecal and serum samples, our goal was to develop a new panCoV RT-PCR assay to detect known human and animal CoVs, including δ-CoVs. In this study, we designed a new primer set to amplify a 668 bp-region within the RNA-dependent RNA polymerase (RdRP) gene that encodes the most conserved protein domain of α-, β-, γ-, and δ-CoVs. We established a one-step panCoV RT-PCR assay and standardized the assay conditions. The newly established panCoV RT-PCR assay was demonstrated to have a high sensitivity and specificity. Using a panel of 60 swine biological samples (feces, intestinal contents, and sera) characterized by PEDV, PDCoV and transmissible gastroenteritis virus-specific RT-PCR assays, we demonstrated that sensitivity and specificity of the newly established panCoV RT-PCR assay were 100%. 400 avian fecal (RNA) samples were further tested simultaneously for CoV by the new panCoV RT-PCR and a one-step RT-PCR assay with the δ-CoV nucleocapsid-specific universal primers. Four of 400 avian samples were positive for CoV, three of which were positive for δ-CoV by the conventional RT-PCR. PanCoV RT-PCR fragments for 3 of the 4 CoVs were sequenced. Phylogenetic analysis revealed the presence of one γ-CoV and two δ-CoV in the sequenced samples. The newly designed panCoV RT-PCR assay should be useful for the detection of currently known CoVs in animal biological samples.

Development and Validation of Multiplex One-Step Real-Time TaqManqRT-PCR Assays for Detection and Quantification of Arboviral Encephalitis Viruses

Arboviral encephalitis is a group of animal and human illness that is mostly caused by several distinct families of viruses including orthobunya virus, phlebovirus, flaviviruses, and the alphaviruses. Although specific signs and symptoms vary by the type of central nervous system (CNS), initial signs and symptoms are very similar. Therefore rapid immunologic and molecular tools for differential diagnosis of arboviral encephalitis viruses are important for effective case management and control of the spread of encephalitis. The qRT-PCR assay, especially multiplex PCR, has the potential to produce considerable savings in time and resources in the laboratory detection. Meanwhile, the use of IC can prevent false negatives effectively by monitoring the processes of nucleic acid extraction and amplification. This report describes the development of a panel of internally controlled multiplex one-step real-time RT-PCR assays in which two virus specific-probe sets were used in the same reaction for the detection of 15 species arboviral encephalitis viruses: the comparative sensitivity of multiplex one-step qRT-PCR assays to single plex one-step qRT-PCR assays as well as one-step RT-PCR assays for detection of each viral species. And total of 150 human serum samples were detected to evaluate the multiplex one-step qRT-PCR assays. These multiplex one-step real-time RT-PCR assays with IC were evaluated in terms of sensitivity, linearity, precision, specificity, and also field samples including serum and vector. These assays can detect and differentiate arboviral encephalitis viruses by high throughput, sensitive, and specific way. It is useful for clinical management and outbreak control of arboviral encephalitis viruses and vector surveillance.

Thiết lập quy trình tổng hợp in vitro phân đoạn RNA của 5 loài virus Ebola

An in vitro transcribed RNA protocol of 5 pathogenic Ebola virus species ZEBOV, SEBOV, BEBOV, TEBOV, REBOV using synthesized plasmids was established with high efficient and following steps: (1) Cloning synthesized plasmids containing NP sequence and 3'UTR region of EBOV in E. coli; (2) 20 μl volume in vitro RNA transcription reaction: 5X TranscriptAid Reaction Buffer; 10 mM dNTPs mix; 0.8 - 1 μg plasmid DNA; 2 μl TranscriptAid Enzyme Mix and DEPC-treated water, 37 °C /2 hours, 2 μl DNase I, 37 °C /15 minutes by TranscriptAid T7 High Yield Transcription Kit. (3) Evaluation of in vitro transcribed RNA by electrophoresis and one-step RT-PCR assay. The in vitro transcribed RNA of 5 Ebola virus species with 900-1400 ng/µl concentration and from 1.8-2.1 A260/A280 ratio.

Rapid detection of Enterovirus and Coxsackievirus A10 by a TaqMan based duplex one-step real time RT-PCR assay

A TaqMan based duplex one-step real time RT-PCR (rRT-PCR) assay was developed for the rapid detection of Coxsackievirus A10 (CV-A10) and other enterovirus (EVs) in clinical samples. The assay was fully evaluated and found to be specific and sensitive. When applied in 115 clinical samples, a 100% diagnostic sensitivity in CV-A10 detection and 97.4% diagnostic sensitivity in other EVs were found.

Easy and inexpensive molecular detection of dengue, chikungunya and zika viruses in febrile patients

Dengue (DENV), chikungunya (CHIKV) and zika (ZIKV) are arthropod-borne viruses (arboviruses) sharing a common vector, the mosquito Aedes aegypti. At initial stages, patients infected with these viruses have similar clinical manifestations, however, the outcomes and clinical management of these diseases are different, for this reason early and accurate identification of the causative virus is necessary. This paper reports the development of a rapid and specific nested-PCR for detection of DENV, CHIKV and ZIKV infection in the same sample. A set of six outer primers targeting the C-preM, E1, and E gene respectively was used in a multiplex one-step RT-PCR assay, followed by the second round of amplification with specific inner primers for each virus. The specificity of the present assay was validated with positive and negative serum samples for viruses and supernatants of infected cells. The assay was tested using clinical samples from febrile patients. In these samples, we detected mono and dual infections and a case of triple co-infection DENV-CHIKV-ZIKV. This assay might be a useful and an inexpensive tool for detection of these infections in regions where these arboviruses co-circulate.

A new real-time RT-qPCR assay for the detection, subtyping and quantification of human respiratory syncytial viruses positive- and negative-sense RNAs

Human respiratory syncytial virus (RSV) is a major health problem and the main cause of hospitalization due to bronchiolitis. RSV is divided into two antigenic subgroups, RSV-A and -B that co-circulate worldwide. Rapid and sensitive detection is desirable for proper patient handling while assessment of viral load may help to evaluate disease severity and progression. Finally RSV subtyping is needed to determine the prevalence and pathogenicity of each RSV subgroup, as well as their sensitivity to treatment. In this study, we took into account the most recent circulating RSV variants and designed two quantitative TaqMan one-step RT-PCR assays to detect and quantify both RSV subgroups separately. Standard dilutions of transcripts of positive and negative polarities were included in the assay validation to assess potential differences in sensitivity on negative-sense genomes and positive-sense RNAs. In addition, RSV detection in respiratory specimens of different types and sampled in different populations was compared to commercially available RSV diagnostic tools. Altogether, the RSV-A and -B assays revealed sensitive and quantitative over a wide range of viral loads, with a slight improved sensitivity of the RSV-B assay on positive sense transcripts, and allowed accurate RSV subtyping. We thus provide a useful tool for both RSV diagnostics and research.

One-step Quantitative RT-PCR Assays for Detecting, Genotyping and Differentiating Wild-Type Group a Rotaviruses and Vaccine (Rotarix® and RotaTeq®) Strains in Stool Samples.

One-step Quantitative RT-PCR Assays for Detecting, Genotyping and Differentiating Wild-Type Group a Rotaviruses and Vaccine (Rotarix® and RotaTeq®) Strains in Stool Samples.

Performance of a one-step quantitative duplex RT-PCR for detection of rotavirus A and noroviruses GII during two periods of high viral circulation

Rotavirus A (RVA) and noroviruses (NoV) are the major viral agents of acute gastroenteritis (AGE) worldwide. In the present study, we aimed to evaluate the performance of a one-step duplex quantitative RT-PCR (dRT-qPCR) assay, established for detection and quantification of RVA and NoV genogroup II (GII) using a single DNA standard curve (SC), as well as to investigate the association between fecal viral load and optical density (OD) values, and viruses’ genotyping. The results obtained by dRT-qPCR in 530 fecal samples from AGE cases were compared with methods employed for the diagnosis of those viruses as follows: enzyme immunoassay (EIA) and polyacrylamide gel electrophoresis (PAGE) for RVA; and qualitative PCR for NoV. By using dRT-qPCR, we detected RVA and NoV in 353 (66%), increasing the positivity rate by 22.5% for RVA and 11.5% NoV, comparing the number of positive samples. RVA and NoV GII were detected in a range of 5.17×103 to 6.56×109 and 3.76×103 to 9.13×1010 genome copies per gram of feces, respectively. We observed a significant direct correlation between genome copies values and optical density, using dRT-qPCR and EIA assays, respectively (Spearman ρ=0.41; p<0.0001). Viruses characterization demonstrated a predominance of NoV GII.4 Sidney 2012 variant during October 2013 to February 2014, followed by the emergence of RVA genotype G12P[8] in 2014. The established assay using a single SC provides an early feedback concerning detection and quantification, with the advantage of detecting simultaneously RVA and NoV GII, reducing time and reagent costs.

Rapid Detection and Molecular Typing of Dengue Virus by Using Multiplex-Nested-RT-PCR

world. We have evaluated the combination of one-step RT-PCR and multiplex nested PCR assays for detectingdengue viruses from clinical samples. Twelve patients were screened for the dengue virus, using a pair of primersthat conserve for several Flavivirus. The results showed that in 12 suspect patients, 100% were positive for Flavivirusand there are some genotypic variation among them, that indicated by several RT-PCR products higher than 511 bp,the expected product for RT-PCR. Further assay was performed to clarify the presence and serotypes of dengue virususing multiplex nested PCR. Serotyping results indicated that 83,3% of samples can be confirmed for dengue virus.Among the dengue virus positive 16,7 % are dengue-2, 16.7 % are dengue-3, and the most common 50% are dengue-4,whereas dengue-1 were not found among the patients. The combination of RT-PCR and multiplex nested PCR assaycan be used for rapid analysis dengue samples in early phase which is potentially useful for clinical, epidemiologyand also evolutionary studies.Key words: Flavivirus, dengue virus, serotype, RT-PCR, multiplex nested PCR

Quantification of the Minimal Residual Disease in Pediatric Philadelphia-Positive Acute Lymphoblastic Leukemia

Philadelphia (Ph) chromosome in acute lymphoblastic leukemia (ALL) is found nearly in 20-30% adults and 5% children. Ph chromosome results from the reciprocal translocation t(9;22)(q34;q11) joining the tyrosine kinase c-ABL1 proto-oncogene on chromosome 9 to BCR gene on chromosome 22. The majority of Ph breakpoint in ALL occurs in the minor breakpoint cluster region at first intron of the BCR gene, and results in the fusion of BCR exon 1 to ABL1 exon 2 (e1a2) generating the oncoprotein p190BCR-ABL1. Ph+ ALL patients present an aggressive disease with a poor prognosis. Current treatment includes potent chemotherapy and tyrosine kinase inhibitors, such as imatinib. The aim of this study was to quantify BCR-ABL1 transcripts in ALL Ph+ patients at different stages of treatment in order to evaluate the kinetics of the tumor clone in response to treatment.We reported a preliminary analysis of the clinical trial GATLA LLA-Ph+2011 (Grupo Argentino de Tratamiento de la Leucemia Aguda LLA-Ph+) that includes patients from 1 to 21 years old newly diagnosed Ph+ ALL. Written informed consent was obtained from all subjects. Diagnosis of Ph+ALL was confirmed by the presence of Ph chromosome and/or positive molecular analysis for detection of BCR-ABL1 fusion transcripts. All patients received induction treatment consisting of vincristine, daunorubicin, prednisolone, asparaginase, and metrotexate. Imatinib was administered 300 mg/m2/day from day 15 of induction until the initiation of conditioning for alloHSCT or to the end of maintenance therapy. The clinical protocol consist in an induction IA (33 days) and IB (28 days), consolidation RA1, RA2 and RA3, re-induction (Protocol II A and B, 36 days each) and maintenance to complete 2 years of treatment. Eligible patients are transplanted after the third block.Minimal residual disease (MRD) monitoring was performed by one-step quantitative RT-PCR assays in bone marrow and/or peripheral blood, using RotorGene® Qiagen; at the end of induction AI, previous RA1, RA2, RA3 and protocol II Fase IIA, IIB and during maintenance or post-alloHSCT. BCR-ABL1 quantification was expressed relative to the amount of ABL1 mRNA. We studied a control group of pediatrics positive P190 isoform bone marrow samples at diagnosis in order to establish our basal reference to estimate the logarithmic reduction of BCR-ABL1 transcripts for our cohort. The obtained mean value of BCR-ABL1(e1a2)/ABL1 in the control group was 55.5% (range 29% - 92%). The molecular response was defined as optimal (OMR, OMR-undetectable) if the BCR-ABL1/ABL1 ratio was lower than 0.055%.A total of 25 subjects (male: female = 16: 9) were enrolled into the study from November 2011 to July 2014. The median age was 7 (range 2 - 19) years old. Type of BCR breakpoint was minor (e1a2) in 96% of patients, and only one present a rearrangement corresponding to major BCR (b3a2). During the follow up (median: 15 months), five patients (20%) died: 3 by sepsis, 1 by post alloHCT complications, and 1 due to disease progression. Two patients had to rotate to dasatinib because of disease relapse: one in central nervous system and the other post alloHCT. Our preliminary results showed that the overall survival was 79%±10% and the survival free of event (death, molecular and disease relapse) was 67%±10% at 12 months.We serially measured BCR-ABL1 at different trial stage (AI, RA1, RA2, RA3, Protocol II) and OMR was 13.3%, 41.2%, 33.3%, 45.5% and 76.9%, respectively. Among 17 evaluable patients on maintenance and post alloHCT, 88% (15/17) obtained OMR values, and among them, 87% (13/15) presented OMR-undetectable values.We evaluated the kinetics of the tumor clone under treatment regarding prognostic factors. Patients older than 10 years showed a higher rate of OMR at RA1 (83% vs 27%, p=0.05). However, all evaluated younger patients reached an OMR at protocol II stage (100% vs 33%, p=0.045), showing a sustained and deeper molecular response. Other evaluated parameters did not show a relationship with OMR at different stages.Our preliminary data showed that BCR-ABL1 quantification may be a good marker to evaluate response to treatment in Ph+ positive ALL patients. BCR–ABL1 transcripts dropped to undetectable levels in 76% (13/17) of evaluable cases at the later stage of treatment. Also, 77% of patients achieved an OMR at Protocol II not only might provide a better chance for receiving alloHSCT but also might contribute to durable remissions. DisclosuresNo relevant conflicts of interest to declare.

Molecular differentiation and phylogenetic analysis of the Egyptian foot-and-mouth disease virus SAT2

In February 2012, a massive new foot-and-mouth disease (FMD) outbreak struck Egypt. In this work, one-step RT-PCR assays were used for in-house detection and differentiation of foot-and-mouth disease virus (FMDV) in Egypt in this year using pan-serotypic and serotype-targeting sequence primers. FMDV SAT2 was the dominant virus in the examined isolates from the epidemic. The complete VP1 coding regions of two isolates were sequenced. The two isolates had 99.2% sequence identity to most contemporary Egyptian SAT2 reference viruses, whereas they had 89.7-90.1% identity to the SAT2/EGY/2/2012 isolate, which was collected from Alexandria, Egypt, and previously sequenced by WRLFMD. Phylogenetic analysis showed that Egypt had one topotype and two lineage of FMDV SAT2 in 2012. The Egyptian and the Palestinian 2012 strains were associated mainly with topotype VII, lineage SAT2/VII/Ghb-12, while the virus isolated from Alexandria Governorate belonged to the SAT2/VII/Alx-12 lineage. Topotype VII also comprised lineages that included strains isolated from Libya in 2012 and 2003. Furthermore, within the same topotype, the Egyptian SAT2/2012 isolates were related to strains from Saudi Arabia, Sudan, Eritrea, Cameroon and Nigeria. Nevertheless, more epidemiological work with neighboring countries is needed to prevent cross-border spread of disease and to reach a precise conclusion about the origin of the 2012 FMDV SAT2 emergency in the Middle East.

A one-step RT-PCR assay to detect and discriminate porcine reproductive and respiratory syndrome viruses in clinical specimens

Outbreaks of highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) have led to large economic losses and, subsequently, have drawn great attention to its diagnosis and prevention. To facilitate rapid discrimination of HP-PRRSV from classical PRRSV (C-PRRSV), we developed a one-step RT-PCR assay. Primer specificities were evaluated with RNA extracted from 8 viral strains and our results revealed that the primers had a high specificity for PRRSV. The assay sensitivity was 25copies/μL for both HP-PRRSV and C-PRRSV. A total of 929 serum samples were identified, of which 20.45% were HP-PRRSV-positive and 1.51% were C-PRRSV-positive, which was completely consistent with that of immunochromatochemistry and sequencing method. The proposed assay can detect the virus 2days prior the onset of symptoms and it can be performed in 2h, thereby providing a rapid method to discriminate HP-PRRSV from C-PRRSV for the identification and prevention of PRRSV infections.

A one-step multiplex RT-PCR assay for simultaneous detection of four viruses that infect peach

A multiplex reverse transcription polymerase chain reaction (mRT-PCR) assay was developed to enable the simultaneous detection and differentiation of four viruses that infect peach, namely Apple chlorotic leaf spot virus (ACLSV), Cherry green ring mottle virus (CGRMV), Prunus necrotic ringspot virus (PNRSV) and Apricot pseudo-chlorotic leaf spot virus (APCLSV). In this study, four pairs of primers, one specific for each virus, were designed; the corresponding PCR products were 632, 439, 346 and 282bp in length for ACLSV, CGRMV, PNRSV and APCLSV, respectively, and the fragments could be distinguished clearly by agarose gel electrophoresis. The sensitivity and specificity of the method were tested using individual RT-PCR and enzyme-linked immunosorbent assay (ELISA), and the identity of the RT-PCR amplification products was also confirmed by DNA sequencing. The results of RT-PCR and ELISA, along with batch detection using samples collected from peach orchards, revealed that this rapid and simple technique is an effective way to identify the four viruses simultaneously. The mRT-PCR assay described in this study was developed for the simultaneous detection of four peach viruses from infected peach samples is reliable and sensitive. In contrast to conventional uniplex RT-PCR, mRT-PCR is more efficient, reducing costs, time and handling when testing large numbers of samples. This rapid and simple method is useful for large-scale surveys of viruses that infect peach.

A novel enterovirus and parechovirus multiplex one-step real-time PCR-validation and clinical experience

As the number of new enteroviruses and human parechoviruses seems ever growing, the necessity for updated diagnostics is relevant. We have updated an enterovirus assay and combined it with a previously published assay for human parechovirus resulting in a multiplex one-step RT-PCR assay. The multiplex assay was validated by analysing the sensitivity and specificity of the assay compared to the respective monoplex assays, and a good concordance was found. Furthermore, the enterovirus assay was able to detect 42 reference strains from all 4 species, and an additional 9 genotypes during panel testing and routine usage.During 15 months of routine use, from October 2008 to December 2009, we received and analysed 2187 samples (stool samples, cerebrospinal fluids, blood samples, respiratory samples and autopsy samples) were tested, from 1546 patients and detected enteroviruses and parechoviruses in 171 (8%) and 66 (3%) of the samples, respectively.180 of the positive samples could be genotyped by PCR and sequencing and the most common genotypes found were human parechovirus type 3, echovirus 9, enterovirus 71, Coxsackievirus A16, and echovirus 25. During 2009 in Denmark, both enterovirus and human parechovirus type 3 had a similar seasonal pattern with a peak during the summer and autumn. Human parechovirus type 3 was almost invariably found in children less than 4 months of age.In conclusion, a multiplex assay was developed allowing simultaneous detection of 2 viruses, which can cause similar clinical symptoms.

Generic and sequence-variant specific molecular assays for the detection of the highly variable Grapevine leafroll-associated virus 3

Grapevine leafroll-associated virus 3 (GLRaV-3) is an economically important virus, which is found in all grapevine growing regions worldwide. Its accurate detection in nursery and field samples is of high importance for certification schemes and disease management programmes. To reduce false negatives that can be caused by sequence variability, a new universal primer pair was designed against a divergent sequence data set, targeting the open reading frame 4 (heat shock protein 70 homologue gene), and optimised for conventional one-step RT-PCR and one-step SYBR Green real-time RT-PCR assays. In addition, primer pairs for the simultaneous detection of specific GLRaV-3 variants from groups 1, 2, 6 (specifically NZ-1) and the outlier NZ2 variant, and the generic detection of variants from groups 1 to 5 were designed and optimised as a conventional one-step multiplex RT-PCR assay using the plant nad5 gene as an internal control (i.e. one-step hexaplex RT-PCR). Results showed that the generic and variant specific assays detected in vitro RNA transcripts from a range of 1×101–1×108 copies of amplicon per μl diluted in healthy total RNA from Vitis vinifera cv. Cabernet Sauvignon. Furthermore, the assays were employed effectively to screen 157 germplasm and 159 commercial field samples. Thus results demonstrate that the GLRaV-3 generic and variant-specific assays are prospective tools that will be beneficial for certification schemes and disease management programmes, as well as biological and epidemiological studies of the divergent GLRaV-3 populations.

A Novel DANP-Coupled Hairpin RT-PCR for Rapid Detection of Chikungunya Virus

Chikungunya has re-emerged as an important arboviral infection of global health significance. Because of lack of a vaccine and effective treatment, rapid diagnosis plays an important role in early clinical management of patients. In this study, we have developed a novel molecular diagnostic platform that ensures a rapid and cost-effective one-step RT-PCR assay, with high sensitivity and specificity, for the early detection of the Chikungunya virus (CHIKV). It uses 2,7-diamino-1,8-naphthyridine derivative (DANP)-labeled cytosine-bulge hairpin primers to amplify the nsP2 region of the CHIKV genome, followed by measurement of the fluorescence emitted from DANP-primer complexes after PCRs. The detection limit of our assay was 0.01 plaque-forming units per reaction of CHIKV. Furthermore, the HP-nsP2 primers were highly specific in detecting CHIKV, without any cross-reactivity with the panel of RNA viruses validated in this study. The feasibility of the DANP-coupled hairpin RT-PCR for clinical diagnosis was evaluated using clinical serum samples from CHIKV-infected patients, and the specificity and sensitivity were 100% (95% CI, 80.0% to 100%) and 95.5% (95% CI, 75.1% to 99.8%), respectively. These findings confirmed its potential as a point-of-care clinical molecular diagnostic assay for CHIKV in acute-phase patient serum samples.

Quantitative one-step RT-PCR assay for rapid and sensitive identification and titration of polioviruses in clinical specimens

Rapid identification and quantitation of polioviruses in clinical specimens is important for surveillance and analysis of virus shedding by vaccine recipients, which could be used to assess the level of mucosal immunity. A quantitative one step RT-PCR was developed for identification and titration of all three poliovirus serotypes. The assay could be an alternative to the traditional procedure based on cell culture isolation and subsequent determination of poliovirus serotype and virus titration. The method is based on quantitative PCR performed with reverse transcription reaction in the same tube. The multiplex assay that quantifies all three serotypes of poliovirus was found to be highly specific, sensitive, and takes only one day to complete.