SARS-CoV-2 RNA-dependent RNA polymerase as a target for high-throughput drug screening.

The ongoing COVID-19 pandemic caused by the SARS-CoV-2 has necessitated rapid development of drug screening tools. RNA-dependent RNA polymerase (RdRp) is a promising target due to its essential functions in replication and transcription of viral genome. To date, through minimal RNA synthesizing machinery established from cryo-electron microscopy structural data, there has been development of high-throughput screening assays for directly screening inhibitors that target the SARS-CoV-2 RdRp. Here, we analyze and present verified techniques that could be used to discover potential anti-RdRp agents or repurposing of approved drugs to target the SARS-CoV-2 RdRp. In addition, we highlight the characteristics and application value of cell-free or cell-based assays in drug discovery.

SARS-CoV-2 RNA-dependent RNA polymerase as a target for high-throughput drug screening

The ongoing COVID-19 pandemic caused by the SARS-CoV-2 has necessitated rapid development of drug screening tools. RNA-dependent RNA polymerase (RdRp) is a promising target due to its essential functions in replication and transcription of viral genome. To date, through minimal RNA synthesizing machinery established from cryo-electron microscopy structural data, there has been development of high-throughput screening assays for directly screening inhibitors that target the SARS-CoV-2 RdRp. Here, we analyze and present verified techniques that could be used to discover potential anti-RdRp agents or repurposing of approved drugs to target the SARS-CoV-2 RdRp. In addition, we highlight the characteristics and application value of cell-free or cell-based assays in drug discovery.

Detection of SARS-CoV-2 RNA Using a DNA Aptamer Mimic of Green Fluorescent Protein.

RNA detection is important in diverse diagnostic and analytical applications. RNAs can be rapidly detected using molecular beacons, which fluoresce upon hybridizing to a target RNA but require oligonucleotides with complex fluorescent dye and quencher conjugations. Here, we describe a simplified method for rapid fluorescence detection of a target RNA using simple unmodified DNA oligonucleotides. To detect RNA, we developed Lettuce, a fluorogenic DNA aptamer that binds and activates the fluorescence of DFHBI-1T, an otherwise nonfluorescent molecule that resembles the chromophore found in green fluorescent protein. Lettuce was selected from a randomized DNA library based on binding to DFHBI-agarose. We further show that Lettuce can be split into two separate oligonucleotide components, which are nonfluorescent on their own but become fluorescent when their proximity is induced by a target RNA. We designed several pairs of split Lettuce fragments that contain an additional 15-20 nucleotides that are complementary to adjacent regions of the SARS-CoV-2 RNA, resulting in Lettuce fluorescence only in the presence of the viral RNA. Overall, these studies describe a simplified RNA detection approach using fully unmodified DNA oligonucleotides that reconstitute the Lettuce aptamer templated by RNA.

Radiation dose levels in chest computed tomography scans of coronavirus disease 2019 pneumonia: A survey of 2119 patients in Chongqing, southwest China.

ABSTRACT: To investigate computed tomography (CT) diagnostic reference levels for coronavirus disease 2019 (COVID-19) pneumonia by collecting radiation exposure parameters of the most performed chest CT examinations and emphasize the necessity of low-dose CT in COVID-19 and its significance in radioprotection.The survey collected RIS data from 2119 chest CT examinations for 550 COVID-19 patients performed in 92 hospitals from January 23, 2020 to May 1, 2020. Dose data such as volume computed tomography dose index, dose-length product, and effective dose (ED) were recorded and analyzed. The radiation dose levels in different hospitals have been compared, and average ED and cumulative ED have been studied.The median dose-length product, volume computed tomography dose index, and ED measurements were 325.2 mGy cm with a range of 6.79 to 1098 mGy cm, 9.68 mGy with a range of 0.62 to 33.80 mGy, and 4.55 mSv with a range of 0.11 to 15.37 mSv for COVID-19 CT scanning protocols in Chongqing, China. The distribution of all observed EDs of radiation received by per patient undergoing CT protocols during hospitalization yielded a median cumulative ED of 17.34 mSv (range, 2.05-53.39 mSv) in the detection and management of COVID-19 patients. The average number of CT scan times for each patient was 4.0 ±â€Š2.0, and the average time interval between 2 CT scans was 7.0 ±â€Š5.0 days. The average cumulative ED of chest CT examinations for COVID-19 patients in Chongqing, China greatly exceeded public limit and the annual dose limit of occupational exposure in a short period.For patients with known or suspected COVID-19, a chest CT should be performed on the principle of rapid-scan, low-dose, single-phase protocol instead of routine chest CT protocol to minimize radiation doses and motion artifacts.