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How do mRNA Vaccines Work?

Messenger RNA (mRNA) is a molecule required for protein production inherent in every cell in the body. The unique biological roles of mRNA make them particularly useful across research and development, and their specialized characteristics have been used to advance clinical diagnostics and medicine. For example, mRNA vaccines help aid your immune system to fight infections faster and prevent the onset of viral symptoms, like those from COVID-19. mRNA vaccines introduce very small amounts of mRNA into the body, that specifically corresponds to a subunit of the viral protein. The viral-associated mRNA then undergoes translation, and in return the body develops specialized antibodies to target the newly developed viral-associated proteins for destruction. In the chance that you become infected with the actual virus later on, your immune system has already developed a base defense system, ready to specifically and efficiently remove the virus.

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These mRNA vaccines work as a first line of defense when the real virus strikes. mRNA vaccines are a powerful alternative to conventional vaccines due to their enhanced potency, increased safety, and capacity for quick clinical development into the test trials phase. Additionally, mRNA vaccines have increased potential for rapid low-cost pharmaceutical manufacturing, typically including a production step (that involves one- or two-step in vitro transcription), and then a secondary isolation step (mRNA purification). Just in the last decade alone, key technological innovations have been targeted at improving mRNA quality, specifically to advance the purity, stability, safety, and yield of the product.

mRNA Vaccine Production and mRNA Purification

Due to the increased demand for mRNA vaccines, the industry requires cost-effective, high throughput manufacturing processes for large scale mRNA production, isolation, and purification. The process of creating mRNA requires several reagents including polymerases and substrates. After the production step, the reaction mixture contains a number of impurities (e.g., harmful enzymes, leftover DNA and nucleoside triphosphates [NTPs]) that must be removed. The mRNA production step inevitably creates abnormal mRNAs, that may be double stranded or truncated, that must also be removed. Optimized mRNA purification helps efficiently remove these contaminants, thereby providing a high yield of mRNA product downstream.

mRNA vaccine manufacturing therefore relies on streamlined large-scale purification processes to ensure that the outcome mRNA remains of the highest purity and yield achievable. There are several types of purification processes for RNA, and more specifically for mRNA, that can help guarantee mRNA purification proceeds as organized and profitable as possible. Key factors in the most efficient mRNA purification processes are those that adhere strictly to GMP guidelines, incorporate the use of automated or semi-automated equipment and instruments, and offer simplified yet effective steps.

To learn more about isolation and purification, and how it can be used towards recombinant proteins, check out our free guide below.

Traditional mRNA Purification

mRNA must be purified differently than other RNAs due to its unique feature, the poly-A tail, which is a string of adenine nucleic acids at the very end of each molecule. The poly-A tail serves to keep the mRNA stable from degradation, increases the stability of the molecule, and allows the mRNA to be exported from the nucleus to the cytoplasm where it is then translated. mRNA manufacturing efforts attempt to mimic this biochemical process, which can be much easier said than done. Even if the in vitro transcription steps can be executed with high precision, subsequent mRNA purification must be highly optimized. An inefficient mRNA purification technique may result in an mRNA product that demonstrates decreased translation efficiency when used in mRNA vaccines, or one that exhibits an unwanted immunostimulatory profile in the patient.

Traditional lab-scale mRNA purification involves the removal of DNA based on DNase enzyme digestion and lithium chloride precipitation. These methods do poorly to allow the complete removal of aberrant mRNA species, though the removal of these effective mRNA is essential and critical to the efficiency and safety of downstream mRNA products. More recent methods of mRNA purification include affinity, ion exchange, or hydrophobic applications, generally incorporating the use of chromatographic columns. The main obstacles for traditional mRNA purification techniques lie in the challenges to overcome less than optimal purification yields, which leads to costly inefficiencies in the long run.

mRNA Purification Using Magnetic Beads Separation

More advancing techniques rely on the use of functionalized magnetic beads for mRNA purification technologies. In one method, magnetic beads are pre-conjugated to oligo-dT  (deoxythymine) tails which are specialized primers that specifically attract and hybridize to the poly-A tails of the mRNAs. The vessel containing the working solution, which holds the magnetic bead-bound-mRNA complexes, is then placed in a magnetic rack or biomagnetic separator. The magnetic field from the magnet attracts the magnetic beads, and forces the mRNA to localize in place within the working solution. At this point, the rest of the solution contains all unwanted or non-target material, which can safely be removed while the mRNA remains undisturbed. The remaining mRNA can be resuspended in fresh buffer, and the vessel is removed from the magnetic field. Once removed, mRNA dissociates from the magnetic beads through optimized buffer conditions. The vessel can undergo magnetic capture again to isolate the freed magnetic beads, and the mRNA can be transferred into a new container.

mRNA purification using magnetic beads separation technologies overcomes many of the challenges faced in traditional mRNA purification. The consumables required are the vessel used to contain the working solution and the reagents. The magnetic beads, if well maintained, can be reused multiple times, and the magnetic rack or biomagnetic separator system will last for a lifetime. The process is also incredibly fast, and many mRNA purification kits using magnetic beads take as little as 15 minutes to perform. Functionalized magnetic beads are also acutely attracted to mRNA, and will avoid being attached to all other non-target materials within the working solution, which makes the process highly accurate, precise, and exact. These attributes make mRNA purification using magnetic beads separation an easy cost efficient alternative to conventional methods, and offer simple protocols that even newer laboratory personnel can safely and quickly perform.

Learn More About mRNA Purification in Our Other Sepmag Articles!

To read more about how mRNA functions within the body and to find a comprehensive protocol on how to use magnetic beads for mRNA purification, check out our article mRNA isolation. If you’re interested in learning more about the process of mRNA extraction and how you can utilize magnetic beads in experimentation, read our article mRNA extraction. Interested in information on knowing which magnetic bead based mRNA purification kits available, specifically suited for your news? Read our article mRNA purification kit! Lastly, if you’re wondering about the purification of RNA in general, we have an article about that too: RNA purification protocol.

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Lluis M. Martínez | SEPMAG Chief Scientific Officer

Founder of SEPMAG, Lluis holds a PhD in Magnetic Materials by the UAB. He has conducted research at German and Spanish academic institutions. Having worked in companies in Ireland, USA and Spain, he has more than 20 years of experience applying magnetic materials and sensors to industrial products and processes. He has filed several international patents on the field and co-authored more than 20 scientific papers, most of them on the subject of magnetic particle movement.

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