As the SARS‐CoV‐2 pandemic continues to rage across the United States and around the globe, the demand for COVID‐19 testing is increasing. The vast majority of the COVID-19 assays use RT‐qPCR to detect the viral RNA in patient samples such as nasopharyngeal swabs, which are collected and stored in viral or universal transport media (VTM/UTM). The general workflow for these COVID‐19 assays can be broken down as follows:
Collect and store patient samples
Ship samples to testing laboratory
Extract RNA from samples
Amplify and analyze samples
While many companies who manufacture the products that are used in these steps have been able to adapt and significantly increase their production capacities, there are still gaps between the supply of these products and the global test demand. Both the sample collection and storage step and the RNA extraction/purification step have a tendency to bottleneck and experience supply constraints. One way to address these bottlenecks and expand production capacity for these in‐demand products is to evaluate the viability of skipping a step in the workflow, without hindering the ability to detect viral RNA from samples.
In the nine months since the first cases of COVID-19 were noticed in Wuhan, China, the virus has spread around the globe and infected over 22 million people. As with all emerging infectious diseases, we often find ourselves with more questions than answers. However, through the tireless work of researchers, doctors and public health officials worldwide, we have learned a lot about the virus, how it spreads and how to contain it.
A protein first purified and sold by Promega almost four decades ago has emerged as a crucial tool in many COVID-19 testing workflows. RNasin® Ribonuclease Inhibitor was first released in 1982, only four years after the company was started. At that time, the entire Promega catalog fit on a single sheet of 8.5 × 11” paper, and RNasin was one of the first products to draw widespread attention to Promega. Today, the demand for this foundational product has skyrocketed as it supports labs responding to the COVID-19 pandemic.
What is RNasin® Ribonuclease Inhibitor?
RNA is notoriously vulnerable to contamination by RNases. These enzymes degrade RNA by breaking the phosphodiester bonds forming the backbone of the molecule. To say that RNases are everywhere is barely an exaggeration – almost every known organism produces some form of RNase, and they’re commonly found in all kinds of biological samples. They’re easily introduced into experimental systems, since even human skin secretes a form of RNase. Once they’re present, it’s very hard to get rid of them. Even an autoclave can’t inactivate RNases; the enzymes will refold and retain much of their original activity.
RNasin® Ribonuclease Inhibitor is a protein that has been shown to inhibit many common contaminating RNases, but without disrupting the activity of enzymes like reverse transcriptase that may be essential to an experiment. It works by binding to the RNase enzyme, prevent it from acting on RNA molecules. This is important for ensuring that RNA samples are intact before performing a complex assay.
We have all been hearing a lot about RT-PCR, rRT-PCR and RT-qPCR lately, and for good reason. Real-Time Reverse Transcriptase Polymerase Chain Reaction (rRT-PCR) is the technique used in by the Center for Disease Control (CDC) to test for COVID-19. Real-time RT-PCR, or quantitative RT-PCR (RT-qPCR)*, is a specialized PCR technique that visualizes amplification of the target sequesnce as it happens (in real time) and allows you to measure the amount of starting target material in your reaction. You can read more about the basics of this technique, and watch a webinar here. For more about RT-PCR for COVID-19 testing, read this blog.
Both qPCR and RT-qPCR are powerful tools for scientist to have at their disposal. These fundamental techniques are used to study biological process in a wide range of areas. Over the decades, Promega has supported researchers with RT-qPCR and qPCR reagents and systems to study everything from from diseases like COVID-19 and cancer to viruses in elephants and the circadian rhythm of krill.
Remdesivir (RDV or GS-5734) was used in the treatment of the first case of the SARS-CoV-2 (formerly 2019-nCoV ) in the United States (1). RDV is not an approved drug in any country but has been requested by a number of agencies worldwide to help combat the SARS-CoV-2 virus (2). RDV is an adenine nucleotide monophosphate analog demonstrated to inhibit Ebola virus replication (3). RDV is bioactivated to the triphosphate form within cells and acts as an alternative substrate for the replication-necessary RNA dependent RNA polymerase (RdRp). Incorporation of the analog results in early termination of the primer extension product resulting in the inhibition.
Why all the interest in RDV as a treatment for SARS-CoV-2 ? Much of the interest in RDV is due to a series of studies performed by collaborating groups at the University of North Carolina Chapel Hill (Ralph S. Baric’s lab) and Vanderbilit University Medical Center (Mark R. Denison’s lab) in collaboration with Gilead Sciences.
Scientists have had a love-hate relationship with PCR amplification for decades. Real-time or quantitative PCR (qPCR) can be an amazingly powerful tool, but just like traditional PCR, it can be quite frustrating. There are several parameters that can influence the success of your PCR assay. We’ve highlighted ten things to consider when trying to improve your qPCR results.
I will admit that over the years, I have watched various crime scene investigation shows and read several books by Kathy Reichs and Patricia Cornwell because I was fascinated by forensic science. These same books and shows are a guilty pleasure because as a scientist, I know these portrayals do not accurately reflect how laboratory work is done. Answers are not so cut and dried as an exact estimation of time of death—for example, death was five hours before the body was found in an abandoned warehouse. However, scientists are always looking for ways to improve accuracy in time of death estimates, which are currently based on a few physical clues that are affected by environment and other factors. One approach taken by Sampaio-Silva et al. (1) was to assess the RNA degradation using reverse transcription quantitative PCR (RT-qPCR).
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