Out of all things one could anticipate out of a year, a vaccine is usually not the first thing that comes to mind. Well, 2020 begs to differ. The COVID-19 pandemic has seen unprecedented progress made towards the development of a vaccine. Of these vaccine candidates, the one technique catching eyeballs because of its spectacular preliminary efficacy results is the mRNA technology.
mRNA or messenger RNA plays a big role in protein synthesis inside the cells. The DNA holds the genetic instructions that cells need to make proteins, which carry out nearly every function in the human body (even disease-related). Through a process called ‘transcription’, an RNA copy of a DNA sequence is generated which holds the instruction to produce a particular protein. This copy, which is the mRNA, travels to the ribosomes which essentially reads or ‘translates’ the mRNA and synthesizes proteins according to the instructions. An mRNA vaccine leverages this by providing genetic code for the cells to produce viral proteins. Once these proteins are generated, which are not the disease itself, the body launches an immune response against the virus in the form of antibodies and immune cells enabling the recipient to develop immunity towards that disease. Ideally, this approach can be used to produce any protein making it very versatile. The mRNA vaccine can enter targeted cells and direct protein production which is not possible with other drug approaches. Since mRNA cannot reverse transcribe into DNA and only interacts with the ribosomes, it cannot alter cell genetics. mRNA is also a very fragile molecule and is rapidly broken down by specific proteins which ensure it does not stay inside the body long after it is administered.
Theoretically, it sounds quite a straightforward process but it is easier said than done as there are a whole set of challenges to overcome when it comes to mRNA-based vaccines. The main challenge has been figuring out the delivery system of the drug to targeted cells while evading the immune system. If the immune system is triggered, it can induce a serious inflammatory response and the protein production is limited thus reducing efficacy. Along with it comes the need for cold storage supply chain and a completely new manufacturing process. It is aggravated by the fact that not a single mRNA drug has progressed beyond clinical trials.
Scientists have clinically tested mRNA vaccines for a wide range of infectious diseases, including rabies, influenza, and Zika. But none have come even near to the progress made by COVID-19 vaccine candidates from Moderna and Pfizer, whose interim results have exceeded expectations. This might be attributed to the sheer amount of resources poured into their development. It is not surprising either that the first promising results came from mRNA-based vaccines. As soon as the genetic sequence for Sars-CoV-2 was published, the companies working on this technology were able to start producing the virus’ mRNA rather quickly. Once approved by the regulators, these will be the first mRNA-based vaccines to be made available for public use.
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