Retroreflection-based sandwich type affinity sensing of isothermal gene amplification product for foodborne pathogen detection

Loop-mediated isothermal amplification (LAMP) is an outstanding method for molecular diagnostics, as the rapid, specific, and sensitive amplification of target genes is possible. However, it is necessary to measure fluorescence...

Diagnóstico de ectima contagioso em pequenos ruminantes através da Reação em Cadeia da Polimerase em Tempo Real

The virus of contagious ecthyma (CEV), also known as orf virus (ORFV) is the etiological agent of contagious ecthyma (CE) in sheep and goat and belongs to the Parapoxvirus genus, family Poxviridae. In some cases, CE can be confused with vesicular diseases so there is need for differentiation especially because, according to the standards of the National Program for the Eradication of FMD (PNEFA), goats and sheep are not vaccinated against Foot and Mouth Disease (FMD), acting as sentinel animals. Although initial studies have demonstrated the usefulness of the polymerase chain reaction (PCR) as a diagnostic test, there are no studies involving its use on Brazilian field samples, which may be genetically distinct from previously studied samples, as described in a study of restriction sites analysis of Brazilian CE samples. This work was conducted with the goal of standardizing a PCR (qPCR) test using SYBR Green I dye for molecular diagnosis of EC in DNA extracted from lesions of affected animal or cell culture inoculated in field samples. The products were detected with qPCR dissociation curve analysis which showed a peak at 88 ºC indicating that positive samples have only one specific amplification product. All DNA samples tested (29 animals crusts and their cell cultures) were positive in the qPCR. The qPCR was able to detect the DNA of at least 10,000 times dilution corresponding to 0.056 ng of DNA. It is believed that with the additional qPCR validations reported in this study, it can be used for differential diagnosis in the health surveillance of PNEFA.

Web-based LinRegPCR: application for the visualization and analysis of (RT)-qPCR amplification and melting data

Background The analyses of amplification and melting curves have been shown to provide valuable information on the quality of the individual reactions in quantitative PCR (qPCR) experiments and to result in more reliable and reproducible quantitative results. Implementation The main steps in the amplification curve analysis are (1) a unique baseline subtraction, not using the ground phase cycles, (2) PCR efficiency determination from the exponential phase of the individual reactions, (3) setting a common quantification threshold and (4) calculation of the efficiency-corrected target quantity with the common threshold, efficiency per assay and Cq per reaction. The melting curve analysis encompasses smoothing of the observed fluorescence data, normalization to remove product-independent fluorescence loss, peak calling and assessment of the correct peak by comparing its melting temperature with the known melting temperature of the intended amplification product. Results The LinRegPCR web application provides visualization and analysis of a single qPCR run. The user interface displays the analysis results on the amplification curve analysis and melting curve analysis in tables and graphs in which deviant reactions are highlighted. The annotated results in the tables can be exported for calculation of gene-expression ratios, fold-change between experimental conditions and further statistical analysis. Web-based LinRegPCR addresses two types of users, wet-lab scientists analyzing the amplification and melting curves of their own qPCR experiments and bioinformaticians creating pipelines for analysis of series of qPCR experiments by splitting its functionality into a stand-alone back-end RDML (Real-time PCR Data Markup Language) Python library and several companion applications for data visualization, analysis and interactive access. The use of the RDML data standard enables machine independent storage and exchange of qPCR data and the RDML-Tools assist with the import of qPCR data from the files exported by the qPCR instrument. Conclusions The combined implementation of these analyses in the newly developed web-based LinRegPCR (https://www.gear-genomics.com/rdml-tools/) is platform independent and much faster than the original Windows-based versions of the LinRegPCR program. Moreover, web-based LinRegPCR includes a novel statistical outlier detection and the combination of amplification and melting curve analyses allows direct validation of the amplification product and reporting of reactions that amplify artefacts.

Simple and Fast DNA Based Sensor System for Screening of Small-Molecule Compounds Targeting Eukaryotic Topoisomerase 1

Background: Eukaryotic topoisomerase 1 is a potential target of anti-parasitic and anti-cancer drugs. Parasites require topoisomerase 1 activity for survival and, consequently, compounds that inhibit topoisomerase 1 activity may be of interest. All effective topoisomerase 1 drugs with anti-cancer activity act by inhibiting the ligation reaction of the enzyme. Screening for topoisomerase 1 targeting drugs, therefore, should involve the possibility of dissecting which step of topoisomerase 1 activity is affected. Methods: Here we present a novel DNA-based assay that allows for screening of the effect of small-molecule compounds targeting the binding/cleavage or the ligation steps of topoisomerase 1 catalysis. This novel assay is based on the detection of a rolling circle amplification product generated from a DNA circle resulting from topoisomerase 1 activity. Results: We show that the binding/cleavage and ligation reactions of topoisomerase 1 can be investigated separately in the presented assay termed REEAD (C|L) and demonstrate that the assay can be used to investigate, which of the individual steps of topoisomerase 1 catalysis are affected by small-molecule compounds. The assay is gel-free and the results can be detected by a simple colorimetric readout method using silver-on-gold precipitation rendering large equipment unnecessary. Conclusion: REEAD (C|L) allows for easy and quantitative investigations of topoisomerase 1 targeting compounds and can be performed in non-specialized laboratories.

First report of grapevine rupestris vein feathering virus in Vitis vinifera L. from Japan

The production of wine grapes is gaining widespread popularity and being carried out on approximately 2,200 hectares of land in Japan. Scions grafted onto rootstocks generally have been imported from the EU, USA, New Zealand, and Australia into Japan. Unfortunately, viruses have spread in Japanese vineyards by slipping through the net of plant quarantine. Grapevine rupestris vein feathering virus (GRVFV), which was detected in a Greek grapevine accessions, is a member of genus Marafivirus in family Tymoviridae (El Beaino et al. 2001). GRVFV has been detected in many countries such as USA, Canada, Australia, New Zealand, Italy, Spain, Switzerland, Czech Republic, Uruguay, and Pakistan (Jo et al. 2015; Eichmeier et al. 2016; Xiao and Meng 2016; Blouin and MacDiarmid 2017; Reynard et al. 2017; Cho et al. 2018; Mahmood et al. 2019; Wu et al. 2020). Herein we report GRVFV infection in Vitis vinifera L. grapevines from Japan. In February 2021, dormant canes from 18 V. vinifera cv. Cabernet Sauvignon with leafroll-like disease symptoms, growing in a vineyard located in Kanagawa Prefecture, were collected. No typical vein banding symptom by GRVFV were observed in the grapevines during the growing season. Total RNA was isolated from the canes using an RNeasy Plant Mini Kit and QIAshredder (Qiagen, Valencia, CA), and subjected to cDNA synthesis using a PrimeScript 1st Strand cDNA Synthesis Kit (Takara Bio, Shiga, Japan). RT-PCR was performed with GRVFV_6156F and GRVFV_6600R primers for GRVFV detection (Reynard et al. 2017). The expected 445 nucleotides (nt) amplification product was obtained from four of 18 grapevines. Sequence analysis of the products revealed 91% identities to corresponding sequences of GRVFV isolates CHASS (KY513702) and Mauzac (KY513701) from Switzerland. Genome walking to determine the whole-genome sequence of the GRVFV isolates from the four grapevines was performed. Briefly, the upstream and downstream of the 445 nt amplification product were amplified from first-strand cDNA using gene-specific primers designed from the product and CHASS-specific primers. Each amplified fragment was Sanger sequenced. Next, gene-specific primers were designed to obtain the complete genome of GRVFV as 13 overlapping DNA fragments from each of the four grapevine samples. An identical complete genome of 6,704 bp was assembled from the overlapping DNA fragments using MEGA 10 software and named as NA1 isolate (DDBJ accession no. LC619667). Phylogenetic analysis of the NA1 genome and corresponding sequences of GRVFV from other countries showed that NA1 formed a cluster with isolate NZ ChTK0004 from New Zealand (MF000326; Supplementary Figure 1). In pairwise comparisons, the complete NA1 genome was most identical at 88% and 87%, respectively to isolates NZ ChTK0004 and Mauzac. The predicted amino acid sequences of NA1 polyprotein shared high homologies (96%) to the corresponding polyprotein sequences of NZ ChTK0004 and Mauzac, suggesting that NA1 is genetically similar to GRVFV isolates from New Zealand and Switzerland. The NA1-infected Cabernet Sauvignon was co-infected with Grapevine leafroll-associated virus 3, Grapevine virus A, and Grapevine rupestris stem pitting-associated virus according to RT-PCR assay for grapevine virus detection (Nakaune and Nakano 2006). The results underscore the importance of intensifying quarantine measures to prevent introduction of exotic viruses via contaminated wine grape vegetative cuttings.

Primers application with the Tso31 gene target in the molecular identification of Taenia solium

Background: taeniasis is a zoonotic disease caused by Taenia spp. Human taeniasis caused by Taenia solium can be acquired after consumption of raw insufficiently cooked infected pork meat. Pigs are intermediate host for T.solium. Pigs acquired this infection by eating human feces that contained T.solium eggs. Pigs infected with T.solium can be transmitted to humans. Purposes: identification of T.solium in pig is important because it is indicator of T.solium transmission. Microscopic examination of T.solium eggs is considered less effective and efficient so that many other methods are developed for T.solium detection such as molecular and immunology. Method: This method used specific primer which can detect the Tso31 gene in T.solium. Tso31 gene is one of the most promising antigens to differentiate T.solium from T.saginata. Pig feces samples were taken by random sampling technique from 7 pig farms in Denpasar. Result: from the 30 samples, we found one sample that which gave a single amplification product of 234 bp. This indicates that the pig farms in Denpasar have been infected with T.solium. Conclusion: it is necessary to do meat inspection properly in the market as well as health education about the dangers and impacts of T.solium infection in the community.

Unexpected Cross-Reaction with Honigbergiella-Like DNA in a PCR for Detection of Bovine Tritrichomonas foetus

The prevalence of bovine Tritrichomonas foetus infection has decreased almost to zero in most European countries, such as Poland, which has been Tritrichomonas foetus-free since 1997. However, tri-trichomonosis is a notifiable disease and there is a duty to examine samples from cattle. In this study, we present an unexpected cross-reaction with Honigbergiella-like DNA in a specimen from a bull. The bovine sample was submitted to the Department of Parasitology National Veterinary Research Institute in Pulawy (NVRI) for confirmatory testing after having been examined at the Regional Veterinary Laboratory, during a routine T. foetus diagnosis. Positive results from microscopic observation and cultures were confirmed. Noteworthily, parasites grew on Diamond’s medium only after seven days of incubation, while optimal growth of trichomonads is generally observed after two to four days for this medium. Moreover, by using PCR we obtained positive results for the presence of T. foetus. However, sequencing of the amplification product revealed 99.62% identity with Honigbergiella sp. Our data suggest that false-positive results may occur in commonly used PCR tests. Thus, unexpected results should be carefully interpreted.

Method for detecting hepatitis B virus in blood plasma at low viral load using real-time PCR

A method for detecting HBV DNA in peripheral blood at low viral load using real-time PCR was developed and its significance in identifying HBsAg-negative viral hepatitis B was evaluated. When developing the method, blood plasma samples and liver tissue biopsy material were used from 128 patients living in St. Petersburg, in various regions of the Russian Federation, as well as in the Central Asia countries. We also used blood plasma samples from 96 pregnant women and 37 hemodialysis center patients living in Northwestern Federal District, 199 foreign citizens undergoing medical examination to obtain work permits at the Directorate for Migration in the Northwestern Federal District, 397 conditionally healthy people living in the Socialist Republic of Vietnam. HBV was detected by nested PCR. Analytical sensitivity was tested using the stepwise dilution method. According to the method developed by us, at the first stage, the HBV DNA is amplified using at the first stage oligonucleotides flanking the genome region 2932-3182 ... 1-1846 nt., and at the second stage two oligonucleotides pairs to the genome virus regions (gene S and gene X) and corresponding oligonucleotide fluorescently labeled probes complementary to the amplified fragments regions carrying fluorophores at the 5’-end, and non-fluorescent quenchers at the 3’-end. The channel corresponding to the FAM fluorophore detects the HBV DNA S-region amplification product, and the channel corresponding to the ROX fluorophore detects the HBV DNA X-region amplification product. The method sensitivity for DNA extraction from plasma with a 100 μl volume was 10 IU/ml. Obtaining a threshold cycle Ct for only one FAM or ROX fluorophore may indicate the HBV DNA presence in a sample at a load of less than 10 IU / ml, HBV detection in this case is possible with a repeated PCR study of the corresponding sample with HBV DNA extraction from an increased plasma volume (200-1000 μl). The developed method makes it possible to identify various HBV genovariants, both characteristic and rare in the Russian Federation, circulating in other world regions. The method can be used to detect HBV in risk groups, in the population, as well as in screening blood donors in order to ensure the blood transfusions safety.

Single cell and whole genome amplification product validation of preimplantation genetic testing systems for monogenic disorders

В рамках подготовительных этапов преимплантационного тестирования 9 моногенных заболеваний (ПГT-М) методом гнездовой ПЦР проанализированы 144 локуса (STR и патогенные варианты)109 единичных клеток и 24 образцов продуктов полногеномной амплификации (ПГА) нескольких клеток. Pre-examination single cell validation was performed for preimplantation genetic testing (PGT-M) for 9 monogenic disorders by nested PCR for STR and pathogenic variants. Totally 109 single cells and 24 WGA products (by MDA) were analyzed.