Real-time Reverse Transcriptase PCR Assay Research Articles

Optimization of an allelic discrimination real-time RT-PCR assay for detection of H275Y oseltamivir resistance gene mutation among influenza A(H1N1)pdm09 patients from 2020 to 2022.

Influenza virus is known to cause mild to severe respiratory infections and is also prone to genetic mutations. Of all the mutations, neuraminidase (NA) gene mutations are a matter of concern, as most approved antivirals target this protein. During the 2020 influenza season, an emergence of mutation in the NA gene, affecting the binding of the World Health Organization (WHO)-recommended probes to the specific site of the NA gene, was reported by our group. As a result of this mutation, the WHO-recommended allelic discrimination real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay was unable to detect wild-type (H275) or mutant oseltamivir-resistant (Y275) strains of influenza A(H1N1)pmd09 viruses. In the current study, the WHO-recommended probes were redesigned according to the mutation in the probe binding site. Fifty undetermined samples (2020-2021) from the previous study were retested with the newly designed probes and found to be positive for H275 and/or Y275. The results obtained were similar to the Sanger sequencing results from the previous study, suggesting that the redesigned probes were efficient in discriminating between wild-type and mutant-type viruses. Furthermore, 133 samples from 2022, making a total of 183 samples (2020-2022), were tested using improved allelic discrimination real-time RT-PCR, and the overall prevalence rate of oseltamivir resistance in 2020-2022 was found to be 0.54%.

Tracking SARS-CoV-2 Omicron lineages using real-time reverse transcriptase PCR assays and prospective comparison with genome sequencing

Omicron has become the dominant SARS-CoV-2 variant globally since December 2021, with distinct waves being associated with separate Omicron sublineages. Rapid detection of BA.1, BA.2, BA.4, and BA.5 was accomplished in the province of Alberta, Canada, through the design and implementation of real-time reverse transcriptase PCR assays targeting S:N501Y, S:ins214EPE, S:H69/V70, ORF7b:L11F, and M:D3N. Using the combination of results for each of these markers, samples could be designated as belonging to sublineages within BA.1, BA.2, BA.4, or BA.5. The analytical sensitivity of these markers ranged from 132 to 2229 copies/mL and in-laboratory accuracy was 98.9–100%. A 97.3% agreement using 12,592 specimens was demonstrated for the assays compared to genome sequencing. The use of these assays, combined with genome sequencing, facilitated the surveillance of SARS-CoV-2 lineages throughout a BA.5-dominated period.

A-259 Detecting Human RNase P Gene Prevents False-Negative of SARS-CoV-2

Abstract Background Real-time Reverse transcriptase—polymerase chain reaction (RT-PCR) is a regular technique for detecting SARS-CoV-2 infection. Human RNase P sequence is using as internal control for PCR assay usually. This article discusses the correlation between SARS-CoV-2 PCR result and human RNase P gene result. Methods Nasopharyngeal swabs were collected from two patients within three consecutive days. We detected for SARS-CoV-2 target gene and human RNase P gene by using real-time RT-PCR assay, which SARS-CoV-2 target gene includes E gene, Rarp gene and N gene . And the threshold cycle values (Ct) were determined by cobas® z 480. Evaluate the results of SARS-CoV-2 and RNase P gene detection. All samples were also analysis for SARS-CoV-2 infection in Taiwan Centers for Disease Control. Results Results of SARS-CoV-2 PCR assay were consistent in both laboratories. SARS-CoV-2 target genes were detected from specimens of both patients on day1. Ct values of E gene were 29.63 and 29.50. Ct values of Rdrp gene were 32.23 and 32.50. Ct values of N gene were 33.09 and 32.68. Ct values of RNase P gene were 21.21 and 21.22. On day 2 and 3, all specimens were negative detected for SARS-CoV-2 PCR. Ct values of RNase P gene were 25.73 and 26.16 on day 2 and 29.82 and 30.28 on day 3. Conclusion The Ct values of human RNase P gene detection can be correlated with the numbers of collected cells. Comparing the results of two patients for three consecutive days, the Ct value of human RNase P gene related to SARS-CoV-2 PCR result. Collection technique can be a factor to affect Ct value of human RNase P gene detection. Develop acceptance range for Ct value of RNase P gene detection can be a quality standard for sample collection to prevent false-negative of SARS-CoV-2.

Evaluation of a rapid, chip-based, micro-PCR assay for detection of rabies virus in human and canine specimens.

Rabies, a lethal zoonotic encephalitis, remains a significant global health concern, causing an estimated 60 000 annual fatalities worldwide. Dogs serve as the primary reservoirs and vectors for transmitting this infection to humans. Definitive diagnosis of rabies in both human and animal cases necessitates laboratory testing involving various clinical specimens. However, the complexity of laboratory infrastructure and the need for skilled personnel, along with the challenge of maintaining cold-chain integrity during sample referral, hinder the decentralization of diagnostic facilities. This study aimed to assess the efficacy of the Truenat rabies assay, a rapid, portable, semiautomated, and closed PCR-based system, for the diagnosis of rabies in both humans and animals. The Truenat assay demonstrated a sensitivity of 100% and a specificity of 86.96% when compared with the fluorescent antibody test (FAT), as the reference standard, on 147 canine brain samples tested. Notably, the Truenat assay exhibited a sensitivity and specificity of 100% when tested on 48 human brain specimens. Furthermore, an examination of 148 human antemortem samples (cerebrospinal fluid, saliva, and skin biopsy) using both the Truenat assay and a validated real-time reverse transcriptase PCR assay revealed a κ value of 0.505, indicative of a moderate level of agreement between the two tests. Thus, the Truenat assay offers a robust, reliable, and affordable point-of-care solution to enhance rabies diagnostic capacity in endemic areas.

Paslahepevirus balayani (Hepatitis E Virus) in Italian Nonungulate Wildlife: Molecular Detection and Characterization of an Isolate from a Crested Porcupine (Hystrix cristata).

Paslahepevirus balayani (hepatitis E virus [HEV]) is the causative agent of hepatitis E, a worldwide zoonosis involving a wide range of hosts among domestic and wild animals. This species is characterized by a great genomic heterogeneity and includes eight genotypes, HEV-1 to HEV-8. The HEV-3 genotype is one of the most common types circulating in Italy in humans and Suidae. Although domestic and wild Sus scrofa and deer (Cervidae) are recognized as the main reservoirs of HEV, several other wild species are potential carriers. A total of 228 liver samples were collected from nonungulate wild animals, found dead, in the framework of the regional passive surveillance program in Umbria and Marche regions (central Italy) during 2018-20. These were tested using real-time reverse-transcriptase PCR (RT-PCR) for detection of RNA of HEV-1 to HEV-4 and confirmed by nested RT-PCR assay. One of the 11 samples collected from crested porcupines (Hystrix cristata) tested positive for the presence of HEV RNA; all other samples were negative. Sequence analysis based on the full-length genome revealed that this isolate, 49434/UM/2018 (accession no. OL658617), belongs to the HEV-3e subtype. These findings suggest a potential role of crested porcupines as a carrier of HEV infection.

Molecular Profiling of Inflammatory Mediators in Human Respiratory Syncytial Virus and Human Bocavirus Infection.

Infections due to human respiratory syncytial virus (HRSV) and human bocavirus (HBoV) can mediate the release of several pro-inflammatory cytokines such as IL-6, IL-8, and TNF-α, which are usually associated with disease severity in children. In this study, the change in the expression profile of cytokines and chemokines were determined during HRSV, HBoV, and HRSV coinfection with HBoV in 75 nasopharyngeal aspirates (NPAs) samples, positive real-time reverse transcriptase PCR Assay (rRT-PCR) for HRSV (n = 36), HBoV (n = 23) infection alone or HRSV coinfection with HBoV (n = 16). The samples were collected from hospitalized children. qPCR-based detection revealed that the levels of IL-6, IL-8, IL-10, IL-13, IL-33, and G-CSF were significantly (p < 0.05) greater in patients than in controls. IL-4, IL-17, GM-CSF, and CCL-5 were significantly elevated in children with HRSV coinfection with HBoV than in other groups (p < 0.05). TNF-α, IL-6, IL-8, IL-10, IL-13, and IL-33 in children with HRSV were significantly increased in severe infections compared to mild infections. Whereas, IL-10, IL-13, and IL-33 were significantly increased in severe infection in compared a mild infection in children with HBoV. Further large-scale investigations involving isolates are needed to enhance our knowledge of the association between viral infections and cytokine expression patterns during the different stages of HRSV and HBoV infection.

The anti-psoriatic effect of Gallic acid is associated with the suppression of keratin 6 and Nrf2

Background: Psoriasis is recognized as an autoimmune dermatosis, and keratin 6 (KRT 6) is a hallmark of psoriasis. Gallic acid (GA) is a natural small molecule with a series of biological activities. However, the effect of GA on psoriasis has not been clarified. background: Psoriasis is recognized as an autoimmune dermatosis and keratin 6 (KRT 6) is a hallmark of psoriasis. Gallic acid (GA) is a natural small molecule with a series of biological activities. However, the effect of GA on psoriasis has not been clarified. Aims: This study aims to investigate the anti-psoriatic activity of GA in psoriasis-like mice and in vitro. objective: This study aimed to investigate the antipsoriatic activity of GA both in psoriasis-like mice and in vitro. Methods: The transcriptions of the Homo sapiens KRT6 gene, and Mus musculus KRT6 gene, were identified using a quantitative real-time reverse transcriptase PCR (qRT-PCR) assay. Expressions of KRT 6, STAT3, pSTAT3, Nrf2, and pNrf2 in HaCaT cells and skin biopsies were determined with a western blotting assay. The immunofluorescence (IF) assay was used to examine the expression of KRT6, pSTAT3, and pNrf2 in HaCaT cells. The expression of KRT 6, PCNA, Ki67, and CD3 was evaluated on the skin of psoriasis-like mice and quantified with histochemical scores (H scores). method: The transcriptions of the Homo sapiens KRT6 gene and Mus musculus KRT6 gene were identified using a quantitative real-time reverse transcriptase PCR (qRT-PCR) assay. Expressions of KRT 6, STAT3, pSTAT3, Nrf2, and pNrf2 in HaCaT cells and skin biopsies were determined with a Western blotting assay. The immunofluorescence (IF) assay was used to examine the expression of KRT6, pSTAT3 and pNrf2 in HaCaT cells. Expression of KRT 6, PCNA, Ki67, and CD3 was evaluated on skin from psoriasis-like mice and quantified with histochemical scores (H scores). Results: GA significantly inhibited KRT 6 gene transcription and expression in psoriasis-like disease both in vitro and in vivo. It significantly inhibited the expression of keratinocyte proliferation markers (PCNA and Ki67), suppressed the expression of CD3 (a marker of T cells), and decreased the thickness of the folded skin, as well as improved the splenomegaly in imiquimod-induced mice similar to psoriasis. Furthermore, the suppressing effect of GA on KRT 6 was abolished by the continuous activation of Nrf2 rather than STAT3, although GA significantly inhibited Nrf2 and STAT3 activation in IL-17A-induced HaCaT cells. result: GA significantly inhibited KRT 6 gene transcription and expression in psoriasis-like disease both in vitro and in vivo. GA significantly inhibited the expression of keratinocyte proliferation markers (PCNA and Ki67), suppressed the expression of CD3 (a marker of T cells), and decreased the thickness of the folded skin, as well as improved the splenomegaly in imiquimod-induced mice similar to psoriasis. Furthermore, the suppressing effect of GA on KRT 6 was abolished by continuously activated Nrf2 rather than STAT3, although GA significantly inhibited Nrf2 and STAT3 activation in IL-17A-induced HaCaT cells. Conclusions: KRT 6 acts as a potential target for GA against psoriasis, and the anti-psoriatic effect of GA could be related to Nrf2 signaling. other: By pharmacological development, this bioactivity of GA could be applied in the treatment of psoriasis in the future.

Diagnostic Efficacy of Chest Computed Tomography for Coronavirus Disease 2019.

A significant discrepancy between the results of previous studies is identified regarding the diagnostic efficacy of chest computed tomography (CT) for coronavirus disease 2019 (COVID-19). We aimed to evaluate the diagnostic efficacy of chest CT for COVID-19. Suspected cases of COVID-19 with fever, cough, dyspnea, and evidence of pneumonia on chest CT scan were enrolled in the study. The accuracy, sensitivity, and specificity of chest CT were determined according to real-time reverse transcriptase-polymerase chain reaction (RT-PCR) results as the gold standard method. The study population comprised 356 suspected cases of COVID-19 (174 men and 182 women; age range 3-96 years; mean age ± standard deviation, 55.21 ± 18.38 years). COVID-19 patients were diagnosed using chest CT with 89.8% sensitivity, 78.1% accuracy, 21.3% specificity, 84.7% positive predictive value, and 30.23% negative predictive value. The odds ratio was 2.39 (95% confidence interval, 1.16-4.91). Typical CT manifestations of COVID-19 were observed in 48 (13.5%) patients with negative RT-PCR results and 30 (8.4%) patients with confirmed positive RT-PCR results had no radiological manifestations. Kappa coefficient of chest CT for diagnosis of COVID-19 was 0.78. The results show that when RT-PCR results are negative, chest CT could be considered as a complementary diagnostic method for the diagnosis of COVID-19 patients. A more comprehensive diagnostic method could be established by combining the chest CT examination, clinical symptoms, and RT-PCR assay.

التأثير التآزري المضاد للأورام للثيموكينون مع الريسفيراترول ضد خط خلايا سرطان الرئة البشرية

Introduction: Thymoquinone (TQ) and resveratrol are natural anticancer and chemo-preventive agents through mechanism(s) that are not fully understood. This study aimed to test the anticancer potential activity of the combination of TQ and Resveratrol, and their underlying mechanisms in the human lung cancer cell line, A549 cells. Materials and methods: The A549 cells were treated with the different concentrations (25, 50, 75, 100, or 200 μM) of TQ, resveratrol, and their combination for 24h. The antiproliferative activity against A549 cells was assessed using (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Trypan blue exclusion assay. Apoptosis markers were assessed by using a real-time reverse transcriptase PCR Assay (rRT-PCR). Results : We found that the proliferation of A549 lung cancer cells was inhibited by TQ, and resveratrol and their combination in a concentration-dependent manner, during a defined period. The combination therapy also could inhibit the growth of A549 cells at 25 μM with a 50% inhibitory concentration (IC50) value of 37 ± 3.18μM. These combinations were significantly (P &lt; 0.001) elevated caspase-3, caspase-8, caspase-9, p53, p21, Fas, FasL, and Bax mRNA levels in treating A549 cells compared to the untreated cells. The anticancer effect of this combination is mediated by the activation of the extrinsic and the intrinsic pathways. Conclusion: all these results give a new promising combination with the enhanced anticancer effect.

Evolving strategy for an evolving virus: Development of real-time PCR assays for detecting all SARS-CoV-2 variants of concern

In order to detect the SARS-CoV-2 variants of concern (VOCs), five real-time reverse transcriptase PCR (rRT-PCR) assays were designed to target the critical discriminatory mutations responsible for the following amino acid changes in the spike protein: two Δ69–70 + N501Y + E gene triplexes (one optimized for Alpha [B.1.1.7] and one optimized for Omicron [B.1.1.529]), a K417N + 242–244 wild-type duplex, a K417T + E484K duplex, and a L452R + P681 + E484Q triplex. Depending on the assay, sensitivity was 98.97–100% for the detection of known VOC-positive samples, specificity was 97.2–100%, limit of detection was 2–116 copies/reaction, intra- and interassay variability was less than 5%, and no cross-reactivity with common respiratory pathogens was observed with any assay. A subset of rRT-PCR- positive VOC samples were further characterized by genome sequencing. A comparison of the lineage designation by the VOC rRT-PCR assays and genome sequencing for the detection of the Alpha, Beta, Gamma, Delta and Omicron variants showed clinical sensitivities of 99.97–100 %, clinical specificities of 99.6–100 %, positive predictive values of 99.8–100%, and negative predictive values of 99.98–100 %. We have implemented these rRT-PCR assays targeting discriminatory single nucleotide polymorphisms for ongoing VOC screening of SARS-CoV-2 positive samples for surveillance purposes. This has proven extremely useful in providing close to real-time molecular surveillance to monitor the emergence of Alpha, the replacement of Alpha by Delta, and the replacement of Delta by Omicron. While the design, validation and implementation of the variant specific PCR targets is an ever-evolving approach, we find the turn-around-time, high throughput and sensitivity to be a useful complementary approach for SARS-CoV-2 genome sequencing for surveillance purposes in the province of Alberta, Canada.

Comparative performance of CDC-modified SARS-CoV-2 real-time PCR assay with four different commercial assays: laboratory-based study.

The coronavirus infectious disease (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viruses. The pandemic has emerged as a global public health crisis, and the threat of fast-spreading of the latest variants of the coronavirus (such as omicron, delta) is rampant. Therefore, a fast and reliable diagnostic assay is needed to make the clinical decision for further treatment. The study aims to develop a Centers for Disease and Prevention (CDC)–modified qualitative real-time reverse transcriptase PCR (RT-qPCR) assay and parallel assessment of commercially available RT-qPCR assay (Altona, Seegene, BD, and GBC) to detect SARS-CoV-2. Two hundred nine samples were chosen randomly out of around two hundred thousand samples. The panel consisted of SARS-CoV-2-positive (n = 156) and SARS-CoV-2-negative (n = 52) nasopharyngeal swab specimens for a primary clinical evaluation. Furthermore, 29 positive samples were sequenced using Oxford Nanopore Minion technology. Two hundred nine patient sample data of the cycle threshold (Ct) readings for target genes of five assays are 100% sensitive for Ct values. Mean Ct values for N1, N2, RdRp, S, and E of the positive controls in CDC assay, RealStar®, Allplex, GBC, and SD Biosensor were 17.5 ± 0.49, 16.9 ± 0.51, 20 ± 0.49, 21.7 ± 0.38, and 23.1 ± 0.43, respectively. F test value shows ≥ 1, which was statistically significant. All assays showed an efficiency of < 120% and R squares were < 0.99, which is well above the required threshold value. Thus, when taking the CDC-modified assay as a gold standard, the other four assays demonstrated a p value of 0.0000, concordance at 100%, and a Kappa at 1.000. A maximum-likelihood (ML) tree was constructed and compared based on full-length SARS-CoV-2 with Wuhan isolate. These isolates are closely related to the B.1.617 lineage and reference sequences. Therefore, we conclude that all RT-PCR kits assessed in this study shall be used for routine diagnostics of COVID-19 in patients. Supplementary informationThe online version contains supplementary material available at 10.1007/s00580-022-03356-y.

Development and Validation of Rapid In-House Diagnostic ELISA Kits for Detection of Human Orthopneumovirus in Clinical Samples.

Currently, the standard assay employed to diagnose human orthopneumovirus infection is real-time reverse transcriptase PCR assay (rRT-PCR), a costly and time-consuming procedure that requires the manipulation of infectious viruses. In addition to RT-PCR, serological tests can complement the molecular diagnostic methods and have proven to be important tools in sero-surveillance. In this study, we report the development, optimization, and validation of a novel and rapid in-house diagnostic ELISA kit to detect human orthopneumovirus in clinical samples. We developed three sensitive ELISA formats through the immunization of rats with novel recombinant pPOE-F or pPOE-TF vectors. The two vectors expressed either the full-length (pPOE-F) or the truncated form (pPOE-TF) of the fusion (F) protein. The developed ELISA kits were optimized for coating buffer, capture antibody, blocking buffer, sample antigen, detection antibodies, and peroxidase-conjugated antibody, and validated using 75 rRT-PCR-confirmed nasopharyngeal aspirate (NPA) human orthopneumovirus samples and 25 negative samples collected from hospitalized children during different epidemic seasons between 2014 and 2017. Our results indicate that rats immunized with pPOE-F or pPOE-TF showed significant induction of high levels of MPAs. Validation of the ELISA method was compared to the rRT-PCR and the sensitivity hierarchy of these developed ELISA assays was considered from highest to lowest: indirect competitive inhibition ELISA (93.3%) > indirect antigen-capture ELISA (90.6%) > direct antigen-capture ELISA (86.6%). The development of the rapid in-house diagnostic ELISA kits described in this study demonstrates that a specific, rapid and sensitive test for human orthopneumovirus antigens could be successfully applied to samples collected from hospitalized children during different epidemics and can help in the efficient diagnosis of respiratory syncytial viral infections.

Real-Time RT-PCR Allelic Discrimination Assay for Detection of N501Y Mutation in the Spike Protein of SARS-CoV-2 Associated with B.1.1.7 Variant of Concern.

ABSTRACTThe N501Y amino acid mutation caused by a single point substitution A23063T in the spike gene of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is possessed by three variants of concern (VOCs), B.1.1.7, B.1.351, and P.1. A rapid screening tool using this mutation is important for surveillance during the coronavirus disease 2019 (COVID-19) pandemic. We developed and validated a single nucleotide polymorphism real-time reverse transcription PCR assay using allelic discrimination of the spike gene N501Y mutation to screen for potential variants of concern and differentiate them from SARS-CoV-2 lineages without the N501Y mutation. A total of 160 clinical specimens positive for SARS-CoV-2 were characterized as mutant (N501Y) or N501 wild type by Sanger sequencing and were subsequently tested with the N501Y single nucleotide polymorphism real-time reverse transcriptase PCR assay. Our assay, compared to Sanger sequencing for single nucleotide polymorphism detection, demonstrated positive percent agreement of 100% for all 57 specimens displaying the N501Y mutation, which were confirmed by Sanger sequencing to be typed as A23063T, including one specimen with mixed signal for wild type and mutant. Negative percent agreement was 100% in all 103 specimens typed as N501 wild type, with A23063 identified as wild type by Sanger sequencing. The identification of circulating SARS-CoV-2 lineages carrying an N501Y mutation is critical for surveillance purposes. Current identification methods rely primarily on Sanger sequencing or whole-genome sequencing, which are time consuming, labor intensive, and costly. The assay described herein is an efficient tool for high-volume specimen screening for SARS-CoV-2 VOCs and for selecting specimens for confirmatory Sanger or whole-genome sequencing.IMPORTANCE During the coronavirus disease 2019 (COVID-19) pandemic, several variants of concern (VOCs) have been detected, for example, B.1.1.7, B.1.351, P.1, and B.1.617.2. The VOCs pose a threat to public health efforts to control the spread of the virus. As such, surveillance and monitoring of these VOCs is of the utmost importance. Our real-time RT-PCR assay helps with surveillance by providing an easy method to quickly survey SARS-CoV-2 specimens for VOCs carrying the N501Y single nucleotide polymorphism (SNP). Samples that test positive for the N501Y mutation in the spike gene with our assay can be sequenced to identify the lineage. Thus, our assay helps to focus surveillance efforts and decrease turnaround times.

149. Extraction-free RT-PCR to Detect SARS-CoV-2 Variants of Concern

BackgroundSARS-CoV-2 variants of concern (VOC) have challenged real-time reverse transcriptase polymerase chain reaction (RT-PCR) methods for the diagnosis of COVID-19. MethodsThe CDC 2019-Novel Coronavirus real-time RT-PCR panel was modified to create a single-plex extraction-free proxy RT-PCR assay, VOCFast™. This assay uses the nucleocapsid N1 as well as novel primer/probe pairs to target VOC mutations in the Orf1a and spike (S) genes. For analytical validation of VOCFast, synthetic controls for the Wuhan, alpha/B.1.1.7, beta/B.1.351, and gamma/P.1 strains were tested at various concentrations. Clinical validation was performed using patient anterior nares swab and saliva specimens collected in the Denver, CO area between Nov 2020 and Feb 2021 or in March 2021. Orthogonal next-generation sequencing (NGS) was also performed. ResultsSimilar N1 quantification cycle (Cq) values corresponding to viral load were observed for all strains, suggesting that VOC mutations do not affect performance of the N1 primer/probe. Orf1a-mut and S1-mut primer/probes generated a stable high Cq value for the Wuhan strain. Conversely, Orf1a-mut Cq values were inversely correlated with viral load for all VOC. The S1-mut Cq was inversely correlated with viral load of the alpha strain, but did not reliably amplify beta/gamma VOC. The limit of detection was 8 copies/uL. The first set of COVID-19 patient specimens revealed no amplification using Orf1a-mut whereas 53% of specimens collected in Mar 2021 demonstrated amplification by Orf-1a. Orthogonal testing by the SARS-CoV-2 NGS Assay and COVID-DX software demonstrated that 12/12 alpha strains, 2/2 beta/gamma strains, and 33/33 Wuhan strains were correctly identified by VOCFast. Detection of VOC in clinical specimens and validation by NGS ConclusionThe combination of the N1, Orf1a-mut, and S1-mut primers/probes in VOCFast can distinguish the Wuhan, alpha, and beta/gamma strains and it consistent with NGS results. Testing of clinical samples revealed that VOC emerged in Denver, CO in March 2021. Future work to discriminate beta, gamma, and emerging VOC is ongoing. In summary, VOCFast is an extraction-free RT-PCR assay for nasal swab and saliva specimens that can identify VOC with a turnaround time suitable for clinical testing. Disclosures Brian L. Harry, MD PhD, Summit Biolabs Inc. (Grant/Research Support, Shareholder) Mara Couto-Rodriguez, MS, Biotia (Employee) Dorottya Nagy-Szakal, MD PhD, Biotia Inc (Employee, Shareholder) Niamh B. O’Hara, PhD, Biotia (Board Member, Employee, Shareholder) Shi-Long Lu, MD PhD, Summit Biolabs Inc. (Grant/Research Support, Shareholder)

Laboratory and Field Evaluations of a Commercially Available Real-Time Loop-Mediated Isothermal Amplification Assay for the Detection of West Nile Virus in Mosquito Pools.

Although the specific cDNA amplification mechanisms of reverse-transcriptase polymerase chain reaction (RT-PCR) and RT loop-mediated isothermal amplification (RT-LAMP) are very different, both molecular assays serve as options to detect arboviral RNA in mosquito pools. Like RT-PCR, RT-LAMP uses a reverse transcription step to synthesize complementary DNA (cDNA) from an RNA template and then uses target-specific primers to amplify cDNA to detectable levels in a single-tube reaction. Using laboratory-generated West Nile virus (WNV) samples and field-collected mosquito pools, we evaluated the sensitivity and specificity of a commercially available WNV real-time RT-LAMP assay (Pro-AmpRT™ WNV; Pro-Lab Diagnostics, Inc., Round Rock, Texas) and compared the results to a validated real-time RT-PCR assay. Laboratory generated virus stock samples containing ≥ 2.3 log10 plaque-forming units (PFU)/ml and intrathoracically inoculated mosquitoes containing ≥ 2.4 log10 PFU/ml produced positive results in the Pro-AmpRT WNV assay. Of field-collected pools that were WNV positive by real-time RT-PCR, 74.5% (70 of 94) were also positive by the Pro-AmpRT WNV assay, resulting in an overall Cohen's kappa agreement of 79.4% between the 2 tests. The Pro-AmpRT WNV assay shows promise as a suitable virus screening tool for vector surveillance programs provided agencies are aware of its characteristics and limitations.

Detection of dengue virus serotypes by single-tube multiplex RT-PCR and multiplex real-time PCR assay

BackgroundAll four dengue serotypes cause infection, with one of them predominantly reported from a particular geographical region. Coinfection by more than one serotype is reported from hyperendemic regions. These coinfections are clinically more severe than infection with a single serotype. This study was carried out to detect the predominant dengue serotype and presence of coinfections. MethodsAcute-phase serum samples of patients suffering from dengue infection were collected. They were screened for the presence of IgM, IgG and NS1Ag by a rapid test. Conventional multiplex reverse transcriptase polymerase chain reaction (RT-PCR) and multiplex real-time RT-PCR assays were carried out for detection and serotyping of the dengue virus. ResultsA total of 196 samples were positive by the rapid card test. Of these, 139 were NS1Ag positive, 40 were positive only for IgM, 5 were positive only for IgG and 12 samples were positive for different combinations of antigen and antibodies. All four serotypes were detected in these samples by PCR. DENV-3 was found to be most common circulating serotype. A total of 22 cases were found to have coinfection with more than one dengue serotypes. Samples having only antibodies and no antigen on rapid card test were also positive for virus by PCR. ConclusionPrevalence of dengue co-infections is increasing. Moreover, it is important to screen for dengue virus in those samples also which do not show NS1Ag on rapid tests and have either one or both the antibodies. Real-time multiplex RT-PCR is found to be more sensitive in detecting coinfection than conventional multiplex RT-PCR.

Epidemiological screening and serotyping analysis of dengue fever in the Southwestern region of Saudi Arabia.

Dengue is an acute systemic viral disease that has been developed globally in both chronic and epidemic transmission periods. Dengue virus (DENV) is a member of the Flavivirus genus of the Flaviviridae family, which endangers public health. Limited studies have been performed in the Saudi Arabia and there are no epidemiological as well as molecular screening of DENV in the Southwestern region and this current study was conducted on the epidemiology of dengue in the Southwestern region of Saudi Arabia. Simultaneously, we have screened the 100 patients for DENV using the real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay. The current study results confirmed that 6637 people from various hospitals and locations in Jazan, Southwestern regions, were enrolled in this study from 2012 to 2020. The overall mean age was 30.02 ± 18.01 years, with 62.8% of males and 37.2% of females enrolled. This study included nearly three-fourths of the Saudi participants and one-fourth of the expatriates, and 56.6% of the positive cases were enrolled. In 2019, the most instances were enrolled, with 44% of positive cases. When screened using the RT-PCR assay, 93% of the positive patients were recruited, according to the quality control analysis. In conclusion, the current study results confirmed the prevalence of DENV was increased drastically since 2012 to 2020. High number of cases were registered prior to the Pandemic. The screening for DENV was performed with RT-PCR assay and NSI antigen should also be implemented to cross-check the results which was previously performed with RT-PCR analysis.

Precision Response to the Rise of the SARS-CoV-2 B.1.1.7 Variant of Concern by Combining Novel PCR Assays and Genome Sequencing for Rapid Variant Detection and Surveillance.

ABSTRACTSARS-CoV-2 variants of concern (VOCs) have emerged as a global threat to the COVID-19 pandemic response. We implemented a combined approach to quickly detect known VOCs while continuously monitoring for evolving mutations of the virus. To rapidly detect VOCs, two real-time reverse transcriptase PCR assays were designed and implemented, targeting the spike gene H69/V70 deletion and the N501Y mutation. The H69/V70 deletion and N501Y mutation assays demonstrated accuracies of 98.3% (95% CI 93.8 to 99.8) and 100% (95% CI 96.8 to 100), limits of detection of 1,089 and 294 copies/ml, and percent coefficients of variation of 0.08 to 1.16% and 0 to 2.72% for the two gene targets, respectively. No cross-reactivity with common respiratory pathogens was observed with either assay. Implementation of these tests allowed the swift escalation in testing for VOCs from 2.2% to ∼100% of all SARS-CoV-2-positive samples over 12 January to 9 February 2021, and resulted in the detection of a rapid rise of B.1.1.7 cases within the province of Alberta, Canada. A prospective comparison of the VOC assays to genome sequencing for the detection of B.1.1.7, combined detection of P.1 and B.1.351, and wild-type (i.e., non-VOC) lineages showed sensitivities of 98.2 to 100%, specificities of 98.9 to 100%, positive predictive values of 76.9% to 100%, and negative predictive values of 96 to 100%. Variant screening results inform sampling strategies for regular surveillance by genome sequencing, thus allowing rapid identification of known VOCs while continuously monitoring the evolution of SARS-CoV-2 in the province.IMPORTANCE Different strains, or variants, of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, the virus that causes COVID-19) have emerged that have higher levels of transmission, less susceptibility to our immune response, and possibly cause more severe disease than previous strains of the virus. Rapid detection of these variants of concern is important to help contain them and prevent them from spreading widely within the population. This study describes two newly developed tests that are able to identify and differentiate the variants of concern from regular strains of SARS-CoV-2. These tests are faster and simpler than the main, gold standard method of identifying variants of concern (genome sequencing). These tests also demonstrated a high correlation with genome sequencing and allowed for the rapid and accurate detection of the rise of B.1.1.7 (one of the variants of concern) in the province of Alberta, Canada.

Analysis of external quality assessment samples revealed crucial performance differences between commercial RT-PCR assays for SARS-CoV-2 detection when taking extraction methods and real-time-PCR instruments into account

In limelight of the ongoing pandemic SARS-CoV-2 testing is critical for the diagnosis of infected patients, contact-tracing and mitigating the transmission. Diagnostic laboratories are expected to provide appropriate testing with maximum accuracy. Real-time reverse transcriptase PCR (RT-PCR) is the diagnostic standard. However, only a handful of studies have reviewed their performance in clinical settings. The aim of this study was to compare the performance of the overall analytical matrix including the extraction kit (BD MAX, Promega, Qiagen), the PCR instrument (Agilent Mx3005 P, BD MAX, Qiagen Rotor-Gene, Roche Cobas z 480) and the RT-PCR assay (Altona Diagnostics, CerTest Biotec, R-Biopharm AG) using predefined samples from proficiency testing organizers. The greatest difference of the cycle threshold values between the matrices was nine cycles. One borderline sample could not be detected by three out of twelve analytical matrices and yielded a false negative result. We therefore conclude that diagnostic laboratories should take the complete analytical matrix in addition to the performance values published by the manufacturer for a respective RT-PCR kit into account. With limited resources laboratories have to validate a wide range of kits to determine appropriate analytical matrices for detecting SARS-CoV-2 reliably. The interpretation of clinical results has to be adapted accordingly.

Serological study of healthcare workers in four different hospitals in Madrid (Spain) with no previous history of COVID-19

ObjectivesHealthcare workers (HCWs) have been one of the most severely affected groups during the COVID-19 pandemic, though few studies have sought to determine the rate of undiagnosed cases among this...