From discovery to COVID-19 vaccine – the journey of mRNA

What are the key technologies that enable mRNA vaccines? What discoveries were needed to make mRNA vaccines viable? Find the answers in this review of: Incorporation of pseudouridine into mRNA enhances translation by diminishing PKR activation. Anderson BR, Muramatsu H, Nallagatla SR, Bevilacqua PC, Sansing LH, Weissman D, Karikó K. Nucleic Acids Res. 2010 Sep;38(17):5884-92. doi: 10.1093/nar/gkq347.

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The COVID-19 vaccines may represent new mRNA-based technology, but multiple decades of research contributed to their rapid development in response to the breakout of the SARS-CoV-2 virus in late 2019. This video will lead you through the discovery of mRNA, the obstacles facing mRNA as a therapeutic agent, how these obstacles were overcome to enable mRNA COVID-19 vaccines, and what the future may hold for mRNA-based technology.

In 1961, mRNA was isolated, and its theoretical biological role published. Its function in encoding for amino acids was also proven. In 1990, injecting in vitro transcribed mRNA expressed the encoded protein in mice, but its therapeutic use was not explored due to its short half-life and unfavourable immunogenicity. In 2004, certain forms of RNA were found to stimulate human dendritic cells and their toll-like receptors. In 2005, Karikó and colleagues suggested an inverse correlation between immunostimulatory potential and the extent of nucleoside modification, playing a pivotal role in advancing mRNA for therapeutic use as its immunogenicity could be reduced. In 2008, Karikó and colleagues demonstrated that incorporating pseudouridine into in vitro transcribed mRNA increased translation and biological stability, and reduced immunogenicity.

In 2010, Anderson and colleagues identified the role of PKR in translation of in vitro transcribed mRNA. They found that unmodified mRNA containing uridine activated PKR more than modified mRNA containing pseudouridine. This activation had a local effect that could suppress translation of other mRNA. The role of PKR in suppressing translation was confirmed using viral proteins that reverse PKR-mediated inhibition of translation and using PKR-deficient cells. Pseudouridine-modified mRNA was determined to not be a competitive inhibitor of PKR, and was found to bind weakly to PKR compared to unmodified mRNA, which resulted in less activation of PKR and thus more translation.

In 2015, N1 methylpseudouridine modification was shown to outperform pseudouridine modification, and was used in the mRNA of the COVID-19 vaccines by BioNTech/Pfizer and Moderna. With these advances in mRNA-based technology, it will not be long before vaccines are developed for other infectious diseases such as influenza, HIV, and malaria. Furthermore, other applications such cell reprogramming, immune checkpoint therapy, and genome editing may be possible.

Creator: Brian Ngo

References:
Anderson, B. R., H. Muramatsu, S. R. Nallagatla, P. C. Bevilacqua, L. H. Sansing et al., 2010 Incorporation of pseudouridine into mRNA enhances translation by diminishing PKR activation. Nucleic Acids Res 38: 5884-5892.
Andries, O., S. Mc Cafferty, S. C. De Smedt, R. Weiss, N. N. Sanders et al., 2015 N1-methylpseudouridine-incorporated mRNA outperforms pseudouridine-incorporated mRNA by providing enhanced protein expression and reduced immunogenicity in mammalian cell lines and mice. J Control Release 217: 337-344.
Jeeva, S., K. -H. Kim, C. H. Shin, B. -Z. Wang, and S. -M. Kang, 2021 An update on mRNA-based viral vaccines. Vaccines 9: 965.
Karikó, K., H. Muramatsu, F. A. Welsh, J. Ludwig, H. Kato et al., 2008 Incorporation of pseudouridine into mRNA yields superior nonimmunogenic vector with increased translational capacity and biological stability. Mol Ther 16: 1833-1840.
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Nance, K. D., and J. L. Meier, 2021 Modifications in an emergency: The role of N1-methylpseudouridine in COVID-19 vaccines. ACS Cent Scie 7: 748-756.
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