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Due to the high reproduction rate of COVID-19, it is important to identify and isolate infected patients at the early stages of infection. The limitations of current diagnostic methods are speed, cost, and accuracy. Furthermore, new viral variants have emerged with higher rates of infectivity and mortality, many with mutations at various primer binding sites, which may evade detection via conventional PCR kits. Therefore, a rapid method that is sensitive, specific, and cost-effective is needed for a point-of-care molecular test. Accordingly, we developed a rapid molecular SARS-CoV-2 detection kit with high specificity and sensitivity, RT-PCR, taking advantage of the loop-mediated isothermal amplification (LAMP) technique. Four sets of six primers were designed based on conserved regions of the SARS-CoV-2 genome: two outer, two inner and two loop primers. Using the optimized protocol, SARS-CoV-2 genes were detected as quickly as 10 min but were most sensitive at 30 min, detecting as little as 100 copies of template DNA. We then coupled the RT-LAMP with a lateral flow dipstick (LFD) for multiplex detection. The LFD could detect two genic amplifications on a single strip, making it suitable for multiplexed detection. The development of a multiplexed RT-LAMP-LFD reaction on crude VTM samples would be suitable for the point-of-care diagnosis of COVID-19 in diagnostic laboratories as well as in private homes.
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Aim: To evaluate the significance of E gene analysis in addition to N and RdRp genes of SARS-CoV-2, and to compare the specificity and sensitivity of targets. Material(s) and Method(s): We used two reverse transcription-PCR assays: one targeting N, E and RdRp and the other targeting N and RdRp genes and analyzed variation in threshold cycle (Ct) values. Result(s): Of the 155 samples, 70.32% tested positive: all three genes were detected in 45.87%, N and RdRp in 19.27% and only N in 34.86%. Patients negative for the E gene were tested after symptoms disappeared and Ct values were significantly higher. Conclusion(s): Samples negative for the E gene were potentially false positive and clinical conditions should be assessed while interpreting results.Copyright © 2023 Future Medicine Ltd.
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Background. Determining if a patient with SARS-CoV-2 remains infectious is an infection control challenge in healthcare settings;specially, among critically ill or profoundly immunosuppressed patients. We use an assay that detects minus-strand RNA as a surrogate for actively replicating SARS-CoV-2. We report positive strand-specific assays in relationship to time since admission and describe patients with a detectable strand-specific assay >20 days since admission. Methods. We use a 2-step rRT-PCR specific to the minus strand of the SARS-CoV-2 envelope gene. The strand-specific assay is used to evaluate for infectivity in asymptomatic patients with a positive admission screening or pre-procedural test or if ongoing replication is suspected (critical illness or profound immunosuppression). We retrieved strand-specific test results for patients hospitalized at Stanford Healthcare during August 2020-March 2022. We describe clinical characteristics for patients with a detectable minus strand-specific test >20 days since admission. Results. A total of 774 strand-specific tests were collected from 624 hospitalized patients. A total of 523 patients had only one test (84%) and 101 (16%) had >=2 tests. The test positivity rate varied by time since admission: 19% in tests performed 0-5 days, 28% in 6-10 days, 22% in 11-20 days, and 41% in those >20 days since admission. Among 35 patients tested >20 days since admission, 13 (37%) had >=1 detectable minus strand-specific test. Most were male (n=8, 62%) and mean age was 59. Of 13 patients with a detectable assay, seven (54%) had prolonged viral replication with persistent symptoms and detectable minus strand assays for >20 days from symptom onset. Of these seven patients, four had a transplant (3 lung, 1 liver), 1 ovarian cancer, 1 CAR-T cell therapy, and 1 ESRD without immunosuppression. The remaining eight patients with a detectable assay >20 days since admission had illness onset while hospitalized. Conclusion. Among hospitalized patients with SARS-CoV-2 infection, we found a varying positivity rate according to the timing of testing, possibly reflecting different indications for the test. The strand-specific assay may help assess for infectiousness in profoundly immunocompromised patients.
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Background. SARS-CoV-2 E gene PCRs have been widely used as the first-line assay with a higher sensitivity than those targeting N or RdRp gene. Given the currently available primers and probes were designed at the onset of the pandemic, it is unknown whether the SARS-CoV-2 VOCs have accumulated significant mutations that may affect E gene PCRs. In this study we aim to perform a comprehensive genetic analysis of SARS-CoV-2 E gene sequences to evaluate the impact of the emerging VOCs on E gene PCR performance. Methods. 600 whole-genome sequences of 7 species of human coronaviruses (HCoVs) were retrieved from GenBank and GISAID, including Sarbecoviruses (SARS-CoV-2 variants B1.1.7, B1.351, P.1, B.1.617.2 and B.1.1.529, and SARS-CoV), Embecovirus (OC43, HKU1), Merbecovirus (MERS) and Alphacoronaviruses (229E, NL63). The E gene sequences were retrieved from fulllength genomes of corresponding viruses and aligned by ClustalW multiple alignment. Phylogenetic, conservation and mutation analyses analysis of the enrolled sequences was performed. Results. E gene-based phylogenetic analysis yielded HCoVs typing results consistent with whole genome typing, suggesting E gene is a reliable locus for phylogenetic analysis and typing of HCoVs. Four pan-Sarbecovirus conserved E gene regions were identified with 100% conserved nucleotide similarity among SARS-CoV-2 and its VOCs, as well as SARS-CoV. These regions have appropriate G/C content which may be suitable for primer/probe design for E gene-based pan-Sarbecovirus screening assay. No significant E mutations were found in 137 retrieved SARS-CoV-2 and its VOCs. Interestingly, two novel variations, C26299U and T26354A, were identified in two of our SARS-CoV-2 strains. The latter variation occurred at the 3' end of the target region of the widely used Charite/Berlin (WHO) probe. This variant may lead to a potential failure of the first-line E gene PCR. Conclusion. Our data shed light on the genetic diversity and conservation of E gene of SARS-CoV-2 and may be beneficial for future primer/probe design for novel first-line assay or SARS-CoV-2-specific E gene PCR. SARS-CoV-2 VOCs have not accumulated significant mutations in E gene so far. The impact of novel E gene variations C26299U and T26354A on molecular diagnostic testing warrants further investigation.
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Background. Determining if a patient with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains infectious can be challenging in patients with severe disease or those profoundly immunosuppressed. We use an assay that detects minus-strand RNA as a surrogate for actively replicating SARS-CoV-2. Here, we describe a cohort of patients who had strand-assay reversion: a detectable minus strandspecific assay after having had an undetectable value which may signify relapse of infection or reinfection. Methods. We used a 2-step rRT-PCR specific to the minus strand of the SARS-CoV-2 envelope gene. The strand-specific assay is used to evaluate for infectivity in asymptomatic patients with a positive screening admission or pre-procedural test or in cases when ongoing infection was suspected (critical illness or profound immunosuppression). We collected minus strand-specific assays performed at Stanford Healthcare during August 2020-April 2022. We describe basic demographics and clinical characteristics for patients who reverted from undetectable to detectable using the minus strand-specific assay. Results. A total of 2,505 strand-specific tests were collected from August 2020-April 2022 from 2,064 patients. A total of 292 (14%) had two or more strandspecific tests. Of them, 19 (7%) had an undetected minus strand-specific assay followed by a subsequent detectable value. Of them, seven (37%) had a minus strandspecific CT value of < 33.Most were male (n=4), median age was 54 (range: 8-62). All were profoundly immunosuppressed: Four had hematologic malignancies and three were post transplantation (kidney, lung, bone marrow). Median time from onset of symptoms or first positive test to reversion was 41 days (range:27-159). Median time from undetectable to detectable minus strand specific test was 26 days (range:4-34). All cases were considered relapses or ongoing infection rather than a new infection. Conclusion. Among patients with SARS-CoV-2 infection and consecutive strand-specific testing, a small proportion reverted from negative to positive. Most were profoundly immunosuppressed. The strand-specific assay can be an important tool in the evaluation of suspected cases of relapse or reinfection.
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Background and Aims: Recent evidence suggests that the gut is an additional target for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, whether SARS-CoV-2 spreads via gastrointestinal secretions remains unclear. To determine the prevalence of gastrointestinal SARS-CoV-2 infection in asymptomatic subjects, we analyzed gastrointestinal biopsy and liquid samples from endoscopy patients for the presence of SARS-CoV-2. Methods: We enrolled 100 endoscopic patients without known SARS-CoV-2 infection (cohort A) and 12 patients with a previous COVID-19 diagnosis (cohort B) in a cohort study performed at a regional hospital. Gastrointestinal biopsies and fluids were screened for SARS-CoV-2 by polymerase chain reaction (PCR), immunohistochemistry, and virus isolation assay, and the stability of SARS-CoV-2 in gastrointestinal liquids in vitro was analyzed. Results: SARS-CoV-2 ribonucleic acid was detected by PCR in the colonic tissue of 1/100 patients in cohort A. In cohort B, 3 colonic liquid samples tested positive for SARS-CoV-2 by PCR and viral nucleocapsid protein was detected in the epithelium of the respective biopsy samples. However, no infectious virions were recovered from any samples. In vitro exposure of SARS-CoV-2 to colonic liquid led to a 4-log-fold reduction of infectious SARS-CoV-2 within 1 hour (P ≤ .05). Conclusion: Overall, the persistent detection of SARS-CoV-2 in endoscopy samples after resolution of COVID-19 points to the gut as a long-term reservoir for SARS-CoV-2. Since no infectious virions were recovered and SARS-CoV-2 was rapidly inactivated in the presence of colon liquids, it is unlikely that performing endoscopic procedures is associated with a significant infection risk due to undiagnosed asymptomatic or persistent gastrointestinal SARS-CoV-2 infections.
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Background: Knowing the true incidence of HIV-1 infections (recent infections) among people newly diagnosed is pivotal to monitoring the course of the epidemic. We have developed a Primer ID Next Gen Sequencing (PID-NGS) assay to identify recent infection by measuring within-host viral diversity over multiple regions of the HIV-1 genome. We implemented a state-wide project to identify recent infections and transmitted drug resistance mutations (DRMs) in diagnostic samples in near real time. Methods: Serum samples from individuals with newly HIV-1 diagnoses (diagnostic sample collected within 30 days of diagnosis) were sequenced. PID-NGS libraries were constructed covering the coding regions for protease, a portion of reverse transcriptase, integrase, and the env gene. The use of the PID-NGS strategy allows for significant error correction and also a definition of the sampling depth of the viral population. Recent infection was defined as within 9-month of infection. DRMs were summarized at detection sensitivities of 30%, 10% and 1% based on viral population sampling depth. Results: From Jan 2018 to Jun 2021, we successfully sequenced partial genomes from 743 individuals with new diagnoses. Year 2020 had the lowest number of new diagnoses (Fig 1a, red bar). Overall, 39.2% of samples were inferred to have represented infection within the previous 9 months. Percent of recent infection varied significantly over the years, increasing from 29.6% in late 2018 to 50.9% in early 2020, but decreasing significantly to 32.7% in 2021 (Fig 1a, blue lines). Individuals younger than 30 y/o were more likely to be identified with recent infection (p<0.01). NNRTI DRMs, especially K103N, were the most abundant DRMs. Fig 1b shows the trend of DRMs over the four years. We observed a trend of decrease in the overall NNRTI DRMs and an increase in the NRTI DRMs in the population. Further analysis suggests that the increase in NRTI DRMs were from TAMs and their revertants, while clinically important NRTI DRMs (K65R and M184) were low (<1%). Conclusion: We have demonstrated a state-wide, all-in-one platform to monitor HIV-1 recency and DRMs in new diagnoses. The number of new diagnoses decreased significantly in 2020 in concert with the COVID-19 pandemic which suggests a decrease in overall HIV testing. The decline in the percentage of recent infections in early 2021 signals a return to broader HIV-1 testing and diagnosis. The increase of other NRTI DRMs suggests ongoing evolution at these sites within the viral population.
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INTRODUCTION: Real-time quantitative PCR (RT-qPCR) is the gold standard for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is specific, sensitive, and simple quantitative. The target of RT-qPCR is to assess the expression level of the SARS-CoV-2 gene through cycle threshold values (CT-value). AIM: The purpose of this study was to analyze the association between the level of SARS-CoV-2 gene expression and the severity of COVID-19 in patients hospitalized. METHOD: This research is an analytic observational study with the cross-sectional method. While the research sample was taken using a consecutive sampling technique from the Medical Records of Sumedang Hospital and Cideres Hospital, West Java, Indonesia, from December 2020 to March 2021. Patient parameters include analysis of age, sex, comorbidity, and disease severity. The severity of the patient is classified based on complaints and oxygen saturation. The expression level of the SARS-CoV-2 N gene and E gene was assessed by calculating the relative quantification by comparing the expression of the E and N gene with the expression of the internal control gene by the Livak formula (2-ΔΔCT Formula). RESULT: The Spearman correlation test showed that there was a relationship between the expression of SARS-CoV-2 genes E and N genes with the severity of COVID-19 patients (with r = 0.374 and p < 0.0001) and (with r = 0.452 and p < 0.0001). CONCLUSIONS: There is a correlation between the level of expression of genes E and gene N with the severity of patients.