Engineered RNA biosensors enable ultrasensitive SARS-CoV-2 detection in a simple color and luminescence assay

The continued resurgence of the COVID-19 pandemic with multiple variants underlines the need for diagnostics that are adaptable to the virus. We have developed toehold RNA–based sensors across the SARS-CoV-2 genome for direct and ultrasensitive detection of the virus and its prominent variants. Here, isothermal amplification of a fragment of SARS-CoV-2 RNA coupled with activation of our biosensors leads to a conformational switch in the sensor. This leads to translation of a reporter protein, for example, LacZ or nano-lantern that is easily detected using color/luminescence. By optimizing RNA amplification and biosensor design, we have generated a highly sensitive diagnostic assay that is capable of detecting as low as 100 copies of viral RNA with development of bright color. This is easily visualized by the human eye and quantifiable using spectrophotometry. Finally, this PHAsed NASBA-Translation Optical Method (PHANTOM) using our engineered RNA biosensors efficiently detects viral RNA in patient samples. This work presents a powerful and universally accessible strategy for detecting COVID-19 and variants. This strategy is adaptable to further viral evolution and brings RNA bioengineering center-stage.

Analysis, quantification, and visualization of RT-LAMP technique for detection of COVID-19

Background: SARS-Cov-2 is a new virus that caused an epidemic disease, COVID-19. According to the world health organization, detecting the patients/carriers is by the far the most important action to prevent the pandemic. Recently, the loop-mediated isothermal amplification (LAMP) technique has become more popular due to the easy handling of a one-step kit used for the detection of many diseases than RT-PCR-based techniques. Methods: Herein, we used the RT-LAMP technique so as to detect COVID-19. To this end, 40 paired-samples of patients and healthy people had been collected and tested by RT-PCR for N and E genes of SARS-CoV-2. The RT-LAMP test has been performed on samples for the RdRp gene. The sensitivity and specificity of tests have been determined. Results: The testing results are consistent with the conventional RT-qPCR. Additionally, we also showed that a one-step process without RNA extraction is feasible to achieve RNA amplification directly from a sample. Conclusion: We confirmed that RT-LAMP is a rapid, simple, and sensitive method that can be used as a large-screening method, particularly in regional hospitals with limited access to high-technologies.

A Review on the Efficiency of NASBA Molecular Technique for Diagnosis of Acute Toxoplasmosis in Pregnant Mothers

Introduction: Toxoplasmosis is a worldwide disease caused by an intracellular protozoan called Toxoplasma gondii and in mothers who become infected during pregnancy, it can cause serious damage to the fetus by passing through the placenta. The aim of this study was to review the effectiveness of the NASBA molecular technique in diagnosing the acute form of Toxoplasmosis in pregnant mothers. Material and Methods: In this study, the websites of PubMed, Google Scholar, SID, Magiran, Web of Science, IranDoc were searched and articles related to the title have been reviewed from 1990 to 2020. Results: Nucleic Acid Sequence-Based Amplification (NASBA) is an isothermal method that has the processes of nucleic acid extraction, amplification, and identification of amplified products. This technique is based on transcription and is specifically used for RNA amplification, so it is highly specific in identifying living and active microorganisms. All steps in this amplification method are performed at 41 °C and the amplified products can be identified by appropriate detection methods such as electrochemical luminescence (ECL). Conclusion: Since all steps of amplification are performed by NASBA at the same temperature of 41°C, unlike molecular PCR technique, a thermocycler is not required, so setting it up will not cost much for laboratories and it can be useful in providing a suitable solution for toxoplasmosis screening in pregnant mothers.

Functional expression of the reverse transcriptase αβ heterodimer from avian myeloblastosis virus in Escherichia coli

The α subunit of avian myeloblastosis virus reverse transcriptase (AMV-RT) is generated from the β subunit by proteolysis, and the αβ heterodimer represents the active form. The codon optimized gene was expressed in E. coli, and an active αβ heterodimer was generated. The RNA amplification activity of the purified recombinant AMV-RT αβ heterodimer was similar to that of the native one.

Ultra-rapid detection of SARS-CoV-2 in public workspace environments

Managing the pandemic caused by SARS-CoV-2 requires new capabilities in testing, including the possibility of identifying, in minutes, infected individuals as they enter spaces where they must congregate in a functioning society, including workspaces, schools, points of entry, and commercial business establishments. Here, the only useful tests (a) require no sample transport, (b) require minimal sample manipulation, (c) can be performed by unlicensed individuals, (d) return results on the spot in much less than one hour, and (e) cost no more than a few dollars. The sensitivity need not be as high as normally required by the FDA for screening asymptomatic carriers (as few as 10 virions per sample), as these viral loads are almost certainly not high enough for an individual to present a risk for forward infection. This allows tests specifically useful for this pandemic to trade-off unneeded sensitivity for necessary speed, simplicity, and frugality. In some studies, it was shown that viral load that creates forward-infection risk may exceed 105 virions per milliliter, easily within the sensitivity of an RNA amplification architecture, but unattainable by antibody-based architectures that simply target viral antigens. Here, we describe such a test based on a displaceable probe loop amplification architecture.

Ultrasensitive RNA biosensors for SARS-CoV-2 detection in a simple color and luminescence assay

The COVID-19 pandemic underlines the need for versatile diagnostic strategies. Here, we have designed and developed toehold RNA-based sensors for direct and ultrasensitive SARS-CoV-2 RNA detection. In our assay, isothermal amplification of a fragment of SARS-CoV-2 RNA coupled with activation of our biosensors leads to a conformational switch in the sensor. This leads to translation of a reporter-protein e.g. LacZ or Nano-lantern that is easily detected using color/luminescence. This response can be visualized by the human eye, or a simple cell phone camera as well as quantified using a spectrophotometer/luminometer. By optimizing RNA-amplification and biosensor-design, we have generated a highly-sensitive diagnostic assay; with sensitivity down to attomolar (100 copies of) SARS-CoV-2 RNA. Finally, this PHAsed NASBA-Translation Optical Method (PHANTOM) efficiently detects the presence of viral RNA in human patient samples, with clear distinction from samples designated negative for the virus. The biosensor response correlates well with Ct values from RT-qPCR tests and thus presents a powerful and easily accessible strategy for detecting Covid infection.

Rapid detection of SARS-CoV-2 with Cas13

To combat disease outbreaks such as the COVID-19 pandemic, flexible diagnostics for rapid viral detection are greatly needed. We report a nucleic acid test that integrates distinct mechanisms of DNA and RNA amplification optimized for high sensitivity and rapid kinetics, linked to Cas13 detection for specificity. We paired this workflow, termed Diagnostics with Coronavirus Enzymatic Reporting (DISCoVER), with extraction-free sample lysis using shelf-stable reagents that are widely available at low cost. DISCoVER has been validated on saliva samples to incentivize frequent testing for more widespread community surveillance and robustly detected attomolar levels of SARS-CoV-2 within 30 minutes, while avoiding false positives in virus-negative saliva. Furthermore, DISCoVER is compatible with multiplexed CRISPR probes to enable simultaneous detection of a human gene control or alternative pathogens.

Screening of Fish Cell Lines for Piscine Orthoreovirus-1 (PRV-1) Amplification: Identification of the Non-Supportive PRV-1 Invitrome

Piscine reovirus (PRV) is the causative agent of heart and skeletal muscle inflammation (HSMI), which is detrimental to Atlantic Salmon (AS) aquaculture, but so far has not been cultivatable, which impedes studying the disease and developing a vaccine. Homogenates of head kidney and red blood cells (RBC) from AS in which PRV-1 had been detected were applied to fish cell lines. The cell lines were from embryos, and from brain, blood, fin, gill, gonads, gut, heart, kidney, liver, skin, and spleen, and had the shapes of endothelial, epithelial, fibroblast, and macrophage cells. Most cell lines were derived from the Neopterygii subclass of fish, but one was from subclass Chondrostei. Cultures were examined by phase contrast microscopy for appearance, and by quantitative polymerase chain reaction (qPCR) for PRV-1 RNA amplification and for the capacity to transfer any changes to new cultures. No changes in appearance and Ct values were observed consistently or transferable to new cultures. Therefore, 31 cell lines examined were unable to support PRV-1 amplification and are described as belonging to the non-supportive PRV-1 invitrome. However, these investigations and cell lines can contribute to understanding PRV-1 cellular and host tropism, and the interactions between virus-infected and bystander cells.

Ultra-rapid detection of SARS-CoV-2 in public workspace environments

Managing the pandemic caused by SARS-CoV-2 requires new capabilities in testing, including the possibility of identifying, in minutes, infected individuals as they enter spaces where they must congregate in a functioning society, including workspaces, schools, points of entry, and commercial business establishments. Here, the only useful tests (a) require no sample transport, (b) require minimal sample manipulation, (c) can be performed by unlicensed individuals, (d) return results on the spot in much less than one hour, and (e) cost no more than a few dollars. The sensitivity need not be as high as normally required by the FDA for screening asymptomatic carriers (as few as 10 virions per sample), as these viral loads are almost certainly not high enough for an individual to present a risk for forward infection. This allows tests specifically useful for this pandemic to trade-off unneeded sensitivity for necessary speed, simplicity, and frugality. In some studies, it was shown that viral load that creates forward-infection risk may exceed 105 virions per milliliter, easily within the sensitivity of an RNA amplification architecture, but unattainable by antibody-based architectures that simply target viral antigens. Here, we describe such a test based on a displaceable probe loop amplification architecture.