Research into vaccines based on RNA began decades ago when scientists theorized that they could harness RNA to produce viral proteins within a cell, prompting a protective immune response. RNA vaccine research drew scientists’ attention during the development of SARS-CoV-2 vaccines during the COVID-19 pandemic, which opened the door for research targeting other diseases with RNA-based therapeutics.
Continue reading “Custom in vitro Transcription Reagents for Manufacturing RNA Therapeutics”We’ve learned a few important lessons from the COVID-19 pandemic.
Perhaps the most significant one is the importance of an early and rapid global response to the initial outbreak. A coordinated response—including widespread use of masks and other personal protective equipment (PPE), travel restrictions, lockdowns and social distancing—could save lives and reduce long-term health effects (1). Widespread availability of effective vaccines goes hand in hand with these measures.
Last month, Pfizer/BioNTech announced the US Food and Drug Administration (FDA) had granted emergency use authorization (EUA) for a new adapted-bivalent COVID-19 booster vaccine for individuals 12 years and older. This vaccine combines mRNA encoding the wild-type Spike protein from the original vaccine with another mRNA encoding the Spike protein of the Omicron BA.4/BA.5 subvariants. Moderna also announced FDA EUA for its new Omicron-targeting COVID-19 booster vaccine. The Omicron variant of SARS-CoV-2 shows multiple mutations across its subvariants, and it is currently the dominant SARS-CoV-2 variant of concern across the world.
Booster doses of vaccines have become a way of life, both due to declining effectiveness of the original vaccines especially in older adults (2), and the rapid mutation rate of SARS-CoV-2 (3). Clinical data for the new Pfizer/BioNTech booster vaccine showed superior effectiveness in eliciting an immune response against Omicron BA.1 compared to the original vaccine. Previously, Moderna published interim results from an ongoing phase 2-3 clinical trial, showing that the new bivalent booster vaccine elicited a superior neutralizing antibody response against Omicron, compared to its original COVID-19 vaccine (4).
Continue reading “mRNA Vaccine Manufacturing: Responding Effectively to a Global Pandemic”
Cell-free gene expression systems are a staple tool for the researcher seeking to understand the regulation of transcription and translation. Many factors can affect the efficiency of cell-free gene expression including vector sequence, reaction components and the template DNA concentration. One factor that has not been extensively studied is how DNA template length influences gene expression.
Continue reading “How Does DNA Template Length Influence Gene Expression in Cell Free Systems?”
Transcription is the production of RNA from a DNA sequence. It’s a necessary life process in most cells. Transcription performed in vitro is also a valuable technique for research applications—from gene expression studies to the development of RNA virus vaccines.
During transcription, the DNA sequence is read by RNA polymerase to produce a complimentary, antiparallel RNA strand. This RNA strand is called a primary transcript, often referred to as an RNA transcript. In vitro transcription is a convenient method for generating RNA in a controlled environment outside of a cell.
In vitro transcription offers flexibility when choosing a DNA template, with a few requirements. The template must be purified, linear, and include a double stranded promoter region. Acceptable template types are plasmids or cloning vectors, PCR products, synthetic oligos (oligonucleotides), and cDNA (complimentary DNA).
In vitro transcription is used for production of large amounts of RNA transcripts for use in many applications including gene expression studies, RNA interference studies (RNAi), generation of guide RNA (gRNA) for use in CRISPR, creation of RNA standards for quantification of results in reverse-transcription quantitative PCR (RT-qPCR), studies of RNA structure and function, labeling of RNA probes for blotting and hybridization or for RNA:protein interaction studies, and preparation of specific cDNA libraries, just to name a few!
In vitro transcription can also be applied in general virology to study the effects of an RNA virus on a cell or an organism, and in development and production of RNA therapeutics and RNA virus vaccines. The large quantity of viral RNA produced through in vitro transcription can be used as inoculation material for viral infection studies. Viral mRNA transcripts, typically coding for a disease-specific antigen, can be quickly created through in vitro transcription, and used in the production of vaccines and therapeutics.
Continue reading “In Vitro Transcription and the Use of Modified Nucleotides”Transcribed RNA can be used to study RNA structure and how it relates to function or how proteins and RNA interact. It can also be used for gene silencing using RNAi (studied more often as a possible therapeutic option) or simply serve as a molecular standard in Real-time RT-PCR. Transcribed RNA is also used in Class 2 Clustered Regularly Interspaced Short Palindromic Repeat systems, or CRISPR.
The CRISPR system, which is naturally occurring in bacteria, has been manipulated to perform gene editing in a laboratory environment. To perform CRISPR in the laboratory environment, you need two main reagents:
Guo et al. used Promega’s RiboMAX™ Large-Scale RNA Production System to produce gRNA to be used in CRISPR for their study to determine the effects of the loss of, or mutations in, a specific gene in fruit flies (1). Atg101 is a gene that plays an important role in autophagy, an intracellular pathway for removing toxins or damaged parts of cells.
Continue reading “Studying Autophagy in Flies Using CRISPR”
A widely used molecular biology technique, in vitro transcription uses bacteriophage DNA-dependent RNA polymerases to synthesize template-directed RNA molecules. Enzymes like bacteriophage SP6, T3 and T7 RNA polymerases are used to produce synthetic RNA transcripts, which can be used as hybridization probes, as templates for in vitro translation applications, or in structural studies (X-ray crystallography and NMR). Synthesized RNA transcripts are also used for studying cellular RNA functionality in processes such as splicing, RNA processing, intracellular transport, viral infectivity and translation.
Problems in the transcription reaction can result in complete failure (i.e., no transcript generated) or in transcripts that are the incorrect size (i.e., shorter or longer than expected). Below is a discussion of the most common causes of in vitro transcription problems.
Continue reading “In Vitro Transcription: Common Causes of Reaction Failure”
Cell-free protein synthesis has emerged as powerful alternative to cell based protein expression for functional and structural proteomics. The TNT® SP6 High-Yield Protein Expression System uses a high-yield wheat germ extract supplemented with SP6 RNA polymerase and other components. Coupling transcriptionaland translational activities eliminates the inconvenience of separate in vitro transcription and purification steps for the mRNA, while maintaining the high levels of protein expression (1).
Continue reading “Optimized Wheat Germ Extract for High-Yield Protein Expression of Functional, Soluble Protein”