RNA vaccines: A story of scientific tenacity

The perseverance of Hungarian biochemist Katalin Karikó was key to the fact that we now have covid-19 vaccines

5 min
A nurse prepares a Pfizer vaccine
  • "Funding, funding and funding", she asked for.
  • "No, no and no", they replied.

These two lines of dialogue could sum up the beginning of many of the most important scientific discoveries in history. They also sum up the beginning of the discovery that has made it possible for billions of people to be immune to covid-19 without having to go through the disease. This is only possible thanks to vaccines, of course. And, of all the vaccines being administered around the world, the ones from Pfizer and Moderna stand out because they are made with a technology based on a type of molecule called messenger RNA. Developing it was not easy.

RNA is a fundamental molecule for life. In fact, many scientists think that the history of life on Earth began with these molecules. Inside every nucleus of every cell of everyone who reads this is the genetic material (DNA) with the instructions to make the proteins that shape and function your body. The mission of messenger RNA is to become a copy of the information stored in the DNA in the nucleus and carry it to the parts of the cell where the corresponding proteins are made. This very fundamental function quickly raised suspicions in the scientific community: if there is a disease caused by a lack of a protein, instead of dealing directly with the protein, which is technically difficult, you can deal with the messenger RNA that makes the body's cells create the protein.

South African biologist Sydney Brenner, the discoverer of RNA

Reasons for doubt

South African biologist Sydney Brenner discovered RNA in 1961, but it wasn't until the early 1990s that technology made it possible to use it as a therapeutic tool. In 1992, a group of scientists at Scripps Research Institute in the United States used this molecule in laboratory rats to temporarily reverse diabetes insipidus, a disease that causes excess urination due to a lack of antidiuretic hormone. The idea was simple: inject messenger RNA into the rats so that their cells would produce the missing hormone. In 1995, a group of researchers led by David Curiel of the University of Alabama-Birmingham, also in the United States, were the first to develop a vaccine based on messenger RNA. They tested it in mice with the aim of generating an immune system response against tumour cells. They published a proof of concept, but were unable to continue the research due to lack of funding. Beyond the experts working directly with it, almost nobody saw a future for it at the time.

There were a few reasons for investors' doubts. First, messenger RNA is a very delicate molecule that must be kept at temperatures several tens of degrees below zero, which complicates its storage and distribution. With a little heat, the components fall apart. In addition, laboratory experiments indicated that in many cases the vaccines did not produce enough protein to achieve the therapeutic goal. This suggested that the messenger RNA did not reach the inside of the cells correctly. Another major problem was that, when injected, the immune system identified it as a foreign substance and generated inflammation to attack and destroy it.

Hungarian biochemist Katalin Karikó, current Vice President of BioNTech

A lot of stubbornness and some luck

In the early 1990s, a Hungarian researcher, who had received her PhD in biochemistry from the University of Szeged, was a postdoctoral fellow at Temple University in Philadelphia and was convinced that the technology had a chance. It was just a matter of having the money to do the research and finding a way to solve the problems. That is why Katalin Karikó asked for funding again and again. She received so many refusals that, after ten years of insisting, she even thought about giving up research. As a result of the lack of success in obtaining funding, the University of Pennsylvania demoted her from her job. And then, as has happened so many times throughout the history of science, chance intervened in a memorable way to turn Karikó's stubbornness into scientific results.

A chance encounter in the early 2000s led Karikó to begin working with researcher Drew Weissman on an AIDS vaccine. The approach, of course, was to make it from messenger RNA. With funding, the results were soon forthcoming. In 2005 they found the solution to two major problems with the technology. Weissman and Karikó's discovery is comparable to that of a carpenter who polishes a door so that it doesn't rub against the floor or a sculptor who, with a single stroke of a scarp, has just given personality to a bust. RNA molecules are chains of smaller molecules called nucleotides. Researchers realised that if they replaced one of these molecules, uridine, with a slightly different molecule, pseudouridine, the messenger RNA would not attract the attention of the immune system and could enter cells to produce more proteins than before.

Entrepreneurs with a vision

Once the discovery was made, the scientists patented the system to produce the messenger RNA, but the University of Pennsylvania sold it to the company CellScript for $300,000. Soon, two scientists saw potential in the discovery. The first, Derrick Rossi, was a postdoc in stem cells at Stanford University and began using the techniques developed by Weissman and Karikó to reprogramme any cells into embryonic stem cells. The technology worked so well that in 2010 Rossi partnered with other researchers and investors to found the company Moderna. Although the company's initial interests were stem cells, it developed a platform for producing messenger RNA that it would use in the early 2020s to design the covid-19 vaccine.

In parallel, a couple of German scientists of Turkish origin, Ugur Sahin and Özlem Türeci, who were researching cancer immunotherapy, saw in messenger RNA technology the possibility of developing personalised therapeutic vaccines that would generate immune activity to destroy cancer cells. In 2008 they had founded the biotech company BioNTech and after learning of Weissman and Karikó's discoveries they acquired some patents. In 2013 they signed Karikó, who today is vice president of the company. In early 2020 BioNTech would team up with the pharmaceutical company Pfizer to produce the covid-19 vaccine.

The envelope is also important

However, to develop covid-19 vaccines, there is still one more discovery to be made. This time Karikó made it in 2015, as a researcher at Philadelphia University together with Norbert Pardi, a Hungarian biochemist who was born in the same city as her. Although the pseudouridine-modified RNA produced more protein than the previous version, it wasn't enough. To get the molecule to better access to the inside of cells, Karikó and Pardi used nanotechnology techniques to wrap it in a tiny sphere of fat called a lipid nanoparticle. Problem solved.

A technology of the future

"RNA vaccines are not new, but have been investigated for some time, especially in relation to cancer treatment", explains Jorge Carrillo, main investigator of the immunology group at IrsiCaixa. In fact, he points out, "there have been phase 2 trials that have shown that they are safe and that they generate an immune response". Idibaps AIDS researcher Montserrat Plana hopes that "from now on there will be more investment in this technology and that Catalonia will choose to have an RNA platform focused on new pathogens. Plana considers that, "although we still have to work on conservation to make these vaccines more manageable, it is a line that cannot be lost".

Derrick Rossi is co-founder of Moderna
A fast, simple and versatile technology

The production of RNA is simpler and faster than that of traditional vaccine components because, among other things, it does not require cell cultures that take months of work. In fact, on 10 January, 2020, the coronavirus genome was published, and in April Moderna began the first vaccine trials with volunteers. This also means that if a virus mutates significantly, the vaccine can be adapted in a short time. Another interesting feature of these vaccines is that RNA is a substance that degrades very easily. Therefore, once inside the body it does not last long, which makes it a safe technology. RNA, moreover, cannot enter the nucleus of the cell and modify the DNA. On the other hand, these are vaccines that produce a very robust immune response, and they can be produced in a scalable and relatively inexpensive way.

A clean immune response

Messenger RNA vaccines generate an immune response that scientists call clean. Vaccines that use the envelopes of other viruses to encapsulate the genetic material of the pathogen they immunise against generate unnecessary immune responses. Because the structure of these other viruses contains proteins, the immune system also generates defenses against them. Something similar happens with protein vaccines: as there is always some impurity in the final preparation, proteins from the pathogen are introduced along with other proteins that also generate an immune response that would not be necessary. This does not happen with messenger RNA vaccines. The RNA only contains instructions for a protein to be produced, which will give rise to a specific immune response. In the case of covid-19 vaccines, this is the S protein that the virus uses to gain access to the inside of cells and infect them.