Performance of the RT-LAMP-based eazyplex® SARS-CoV-2 as a novel rapid diagnostic test.

BACKGROUND: Diagnostic assays for severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2) that are easy to perform and produce fast results are essential for timely decision making regarding the isolation of contagious individuals. OBJECTIVE: We evaluated the CE-approved eazyplex® SARS-CoV-2, a ready-to-use real time RT-LAMP assay for identification of the SARS-CoV-2 N and ORF8 genes from swabs in less than 30 min without RNA extraction. STUDY DESIGN: Oropharyngeal and nasal swabs from 100 positive and 50 negative patients were inoculated into 0.9 % saline and tested by NeuMoDx™ RT-PCR. An aliquot was diluted fivefold in Copan sputum liquefying (SL) solution and directly analyzed by eazyplex® SARS-CoV-2. In addition, 130 patient swabs were prospectively tested with both methods in parallel. Analytical sensitivity of the assay was determined using virus stock dilutions. RESULTS: Positive percent agreement (PPA) between the eazyplex® SARS-CoV-2 and RT-PCR was 74 % for samples with Ct values < 35. When using a Ct cut-off ≤ 28 the PPA increased to 97.4 %. In the prospective part of the study overall PPA of the eazyplex® kit was 66.7 % but increased to 100 % when only Ct values ≤ 28 were considered. There were no false positive results. The median time to positivity was 12.5 min for the N gene and 16.75 min for ORF8. Analytical sensitivity was 3.75 TCID50/mL. 105 virus copies/mL were reproducibly detected. CONCLUSION: The eazyplex® SARS-CoV-2 is a rapid assay that accurately identifies samples with high viral loads. It may be useful for near-patient testing outside of a molecular diagnostic laboratory.

SARS-CoV-2 causes severe epithelial inflammation and barrier dysfunction.

Infections with SARS-CoV-2 can be asymptomatic, but they can also be accompanied by a variety of symptoms that result in mild to severe coronavirus disease-19 (COVID-19) and are sometimes associated with systemic symptoms. Although the viral infection originates in the respiratory system, it is unclear how the virus can overcome the alveolar barrier, which is observed in severe COVID-19 disease courses. To elucidate the viral effects on the barrier integrity and immune reactions, we used mono-cell culture systems and a complex human chip model composed of epithelial, endothelial, and mononuclear cells. Our data show that SARS-CoV-2 efficiently infected epithelial cells with high viral loads and inflammatory response, including interferon expression. By contrast, the adjacent endothelial layer was neither infected nor did it show productive virus replication or interferon release. With prolonged infection, both cell types were damaged, and the barrier function was deteriorated, allowing the viral particles to overbear. In our study, we demonstrate that although SARS-CoV-2 is dependent on the epithelium for efficient replication, the neighboring endothelial cells are affected, e.g., by the epithelial cytokines or components induced during infection, which further results in the damage of the epithelial/endothelial barrier function and viral dissemination.IMPORTANCESARS-CoV-2 challenges healthcare systems and societies worldwide in unprecedented ways. Although numerous new studies have been conducted, research to better understand the molecular pathogen-host interactions are urgently needed. For this, experimental models have to be developed and adapted. In the present study we used mono cell-culture systems and we established a complex chip model, where epithelial and endothelial cells are cultured in close proximity. We demonstrate that epithelial cells can be infected with SARS-CoV-2, while the endothelium did not show any infection signs. Since SARS-CoV-2 is able to establish viremia, the link to thromboembolic events in severe COVID-19 courses is evident. However, whether the endothelial layer is damaged by the viral pathogens or whether other endothelial-independent homeostatic factors are induced by the virus is essential for understanding the disease development. Therefore, our study is important as it demonstrates that the endothelial layer could not be infected by SARS-CoV-2 in our in vitro experiments, but we were able to show the destruction of the epithelial-endothelial barrier in our chip model. From our experiments we can assume that virus-induced host factors disturbed the epithelial-endothelial barrier function and thereby promote viral spread.

Early postmortem mapping of SARS-CoV-2 RNA in patients with COVID-19 and the correlation with tissue damage.

Clinical observations indicate that COVID-19 is a systemic disease. An investigation of the viral distribution within the human body and its correlation with tissue damage can aid in understanding the pathophysiology of SARS-CoV-2 infection. We present a detailed mapping of the viral RNA in 61 tissues and organs of 11 deceased patients with COVID-19. The autopsies were performed within the early postmortem interval (between 1.5 and 15 hr, mean: 5.6 hr) to minimize the bias due to viral RNA and tissue degradation. Very high viral loads (>104copies/ml) were detected in most patients' lungs, and the presence of intact viral particles in the lung tissue could be verified by transmission electron microscopy. Interestingly, viral RNA was detected throughout various extrapulmonary tissues and organs without visible tissue damage. The dissemination of SARS-CoV-2-RNA throughout the body supports the hypothesis that there is a maladaptive host response with viremia and multiorgan dysfunction.

Since the discovery of the new coronavirus that causes COVID-19, scientists have been scrambling to understand the different features of the virus. While a lot more is now known about SARS-CoV-2, several key questions have proved more difficult to answer. For example, it remained unclear where the virus travels to in the body and causes the most harm. To help answer this question, Deinhardt-Emmer, Wittschieber et al. performed postmortem examinations on 11 patients who had recently died of COVID-19. After sampling 61 different organs and tissues from each patient, several tests were used to detect traces of SARS-CoV-2. The experiments showed that the largest pool of SARS-CoV-2 was present in the lungs, where it had caused severe damage to the alveolae, the delicate air sacs at the end of the lungs' main air tubes. Small amounts of the virus were also detected in other organs and tissues, but no severe tissue damage was seen. In addition, Deinhardt-Emmer, Wittschieber et al. found that each patient had increased levels of some of the proteins involved in inflammation and blood clotting circulating their bloodstream. This suggests that the inflammation caused by SARS-CoV-2 leads to an excessive immune reaction throughout the entire body. This research provides important new insights into which areas of the body are most impacted by SARS-CoV-2. These findings may help to design more effective drug treatments that target the places SARS-CoV-2 is most likely to accumulate and help patients fight off the infection at these regions.

Use of the variplex™ SARS-CoV-2 RT-LAMP as a rapid molecular assay to complement RT-PCR for COVID-19 diagnosis.

BACKGROUND: Molecular assays based on reverse transcription-loop-mediated isothermal amplification (RT-LAMP) may be useful for rapid diagnosis of the severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2) because of the easy performance and the option to bypass RNA extraction. OBJECTIVES: This study was designed to evaluate the clinical performance of the CE-labeled variplexTM real time SARS-CoV-2 RT-LAMP assay in comparison to commercial RT-PCRs. STUDY DESIGN: RNA extracted from pharyngeal swabs was tested by variplex™ RT-LAMP and Corman's LightMix™ E gene RT-PCR as reference. Samples of respiratory secretions from Coronavirus infection disease (COVID-19) and negative control patients were analyzed by variplex™ without RNA extraction and tested in parallel with the Allplex™ and VIASURE BD MAX RT-PCRs. RESULTS: Using isolated RNA variplex™ RT-LAMP showed a sensitivity of 75 % compared to LightMix E gene RT-PCR but contrary to the latter it produced no false-positive results. For the evaluation of samples from respiratory secretions concordance analysis showed only a moderate agreement between the variplex™ RT-LAMP conducted on unprocessed samples and Allplex™ and VIASURE RT-PCRs (Cohen's κ ranging from 0.52-0.56). Using the approach to define a sample as true-positive when at least two assays gave a positive result the clinical sensitivities were as follows: 76.3 % for variplex™, 84.2 % for Allplex™ and 68.4 % for VIASURE. However, when results of RT-PCR and RT-LAMP were combined diagnostic sensitivity was increased to 92-100 %. CONCLUSION: The variplex RT-LAMP may serve as a rapid test to be combined with a RT-PCR assay to increase the diagnostic accuracy in patients with suspected COVID-19 infection.