RNA vaccines open a new window in the field of immunology

Publicação: 6 de August de 2021

Technology could revolutionize immunization efforts against HIV, malaria, flu, and many other diseases

With the approval of the first vaccines that use messenger RNA, it will be possible to act more quickly in future epidemics and prevent thousands of deaths

The messenger RNA platform may be new to a global audience, but it’s a technology that researchers have been relying on for nearly three decades. More simplified than conventional approaches, this approach that has led to remarkably safe and effective vaccines against a new virus also holds promise against old enemies such as HIV, tuberculosis, malaria and other diseases that cause countless deaths in low-income countries. It is also being tested to treat some cancers, including melanoma and brain tumors. It could be a new way to fight autoimmune diseases. Furthermore, it is being seen as a possible alternative to gene therapy for intractable diseases such as sickle cell anemia.

Unlike DNA, which is a relatively more stable molecule and can be stored over months and years at temperatures ranging between 4° and -20°, RNA is much more unstable, degrading very easily, which is why which is why the development of an RNA vaccine becomes extremely complex. In 2005, a series of scientific papers began to spread the knowledge gained on mechanisms to stabilize the structure of RNA when the molecule was injected into the muscles of animals during laboratory tests. So, the scientists decided to introduce the RNA into a capsule, that is, packaged into small particles and thus not released into the bloodstream. Once inside the human body, the synthetic fragment of genetic material, now stable, makes the body itself synthesize the protein encoded by it.

Until 2020, there were no vaccines made from messenger RNA on the market. The pandemic, like any health crisis, accelerated science and, of course, the development of vaccines for other diseases. An example of this is the research published on June 18 in the scientific journal Nature Messenger RNA expressing PfCSP induces functional, immune responses against malaria in mice who claims to have developed a new malaria vaccine based on messenger RNA technology. The expectation is that the immunizing agent can replace existing and, until now, limited therapies against the disease. Hope comes after the success of COVID-19 mRNA vaccines. Advances in RNA genetic technology have helped researchers move closer to the Holy Grail by accelerating many stages of vaccine research and development.

To learn more about the subject, the Communication Office of the Brazilian Society of Tropical Medicine (SBMT) interviewed Dr. Rafael Dhalia, Researcher at FIOCRUZ Pernambuco and Member of the Pernambuco Academy of Sciences and Dr. Ernesto Torres de Azevedo Marques Júnior, Researcher at FIOCRUZ Pernambuco and Researcher at the University of Pittsburgh.

Check the interview in full:

SBMT: With the approval of the first vaccines that use messenger RNA, there is the possibility to act more quickly in future epidemics and prevent thousands of deaths with the more agile creation of a cheap and fast production immunizer — although many countries still face the challenges of logistics and related to the political interests of their governors. What is your opinion about this?

Dr. Rafael Dhalia: The messenger RNA technology allows, in fact, a rapid adaptation of production platforms, making it possible to quickly change the genetic information of the RNA in situations of future epidemics, in order to control the infection by new microorganisms. The logistical challenge of storing at extremely low temperatures, -70 degrees Celsius, has already been overcome, and it is now possible to store in common freezers, and even in a refrigerator. But like all relatively new technology, and which had never been implemented before for mass vaccination, the cost is still high and has only been serving medium to high purchasing power countries. In fact, there is a politicization of the use of all Covid-19 vaccines that has cost thousands of lives but this politicization is not restricted to RNA vaccines. Countries that have invested the most in protecting their population through mass vaccination, social distancing measures and encouraging hygiene measures and the use of masks, have been experiencing a drastic reduction in the number of hospitalizations and deaths due to infection by Sars-Cov-2 and their economies have already started to grow again. On the other hand, countries that adhered to obscurantism and conspiracy theories, denying science (as is the case in Brazil), have been facing a huge number of daily deaths and have even become a granary for new variants.

SBMT: Messenger RNA vaccine technology is not new. What have been the difficulties encountered during the last two decades?

Dr. Ernesto T. A. Marques: Immunogenic proteins are synthesized by the organism itself from instructions contained in the messenger RNA, and RNA vaccine technology started in the 90’s, in fact it is not a new discovery, it has only been optimized. Among the various difficulties encountered in recent decades, without a doubt the greatest is the preservation of the messenger RNA molecule, which is extremely fragile. The technology of chemical synthesis had to be continually improved, stabilizing molecules were developed and encapsulation techniques for mechanical protection, and transport of RNA into cells, were also improved. All of this allowed us to advance towards the development of RNA vaccines against Sars-Cov-2, by Pfizer and Moderna. The CureVac vaccine, developed in Germany, with the perspective of preservation in a common refrigerator and stability at room temperature for 24 hours, also reached phase III of the development of RNA vaccines against Covid-19.

SBMT: For many years, the use of messenger RNA provoked very aggressive immune reactions. Why did this happen and what changed?

Dr. Rafael Dhalia: Two advances were very important for improving immune responses. First, a lot of attention was paid to the molecular structure of the antigen, which in the case of Sars-Cov-2 is the “Spike” protein. This protein was stabilized in its pre-fusion trimeric form, which allowed to induce a much more efficient immune response against the virus than the immune response induced by the natural infection itself. Second, the way messenger RNA enters cells has been optimized, allowing for safer and more effective targeting of the immune response. RNA was encapsulated in nanoparticles of molecules, made with specific types of fat, called liposomes. Several formulations and concentrations were optimized, so that the liposomes became inert and facilitated, as much as possible, the messenger RNA molecule to cross cell membranes, so that the cell could then produce the SARS-CoV-2 protein and present it to the immune system.

SBMT: In your opinion, what will be the future applications of mRNA vaccine technology?

Dr. Ernesto T. A. Marques: Before the Sars-Cov-2 Pandemic, Moderna, for example, was already developing messenger RNA molecules aiming at vaccines against dozens of other diseases. Among these we can emphasize some arboviruses such as Yellow Fever, Dengue, Zika and Chikungunya, which have been causing recurrent outbreaks in Brazil. With the Pandemic, due to the urgency, all the platforms under development were put aside and everything was adapted, for the development of RNA vaccines against Sars-Cov-2. The entire process was accelerated, from the testing and production steps to phase III testing and mass vaccination. The results observed in the vaccinated populations are extremely encouraging: a reduction in serious cases and deaths, in addition to a reduction in the circulation of the virus. Not even the most optimistic of scientists expected such promising results, in such a short time span. Sars-Cov-2 RNA vaccines will certainly open the way for vaccines that were already under development, such as arboviruses, for example. There is also the potential to develop other “failed” vaccines, such as vaccines for HIV and resistant strains of tuberculosis.

SBMT: When it comes to tropical diseases such as Ebola, HIV, malaria, tuberculosis, Chagas disease, among others, and complex organisms such as parasites and Plasmodium, you believe that the technology of anti-COVID vaccines can help fight these and other diseases?

Dr. Rafael Dhalia: Absolutely. The most diverse technologies were used in the development of vaccines against Sars-Cov-2. From the more traditional ones, such as inactivated virus vaccines, to the most technological ones, such as viral vector (adenovirus) and messenger RNA vaccines. There are also several vaccine initiatives based on protein subunit, using state-of-the-art technologies… such as the use of soluble carrier proteins, which are already in Phase III evaluation. The accumulated knowledge and the integration of technologies from different fields, allowed us to quickly develop vaccines against the new coronavirus. All of this can, and should, be used as a foundation for the development of vaccines against other diseases, and the prevention of new pandemics.

SBMT: According to North American research, developed by scientists at the University of Washington and the Fred Hutchinson Cancer Research Center, the protection produced by messenger RNA vaccines may be more effective against the new variants of the coronavirus than the natural protection obtained after the recovery of a case of COVID-19. What is your opinion about this?

Dr. Ernesto T. A. Marques: We have no doubt that they are right. The main antigen, capable of inducing a neutralizing immune response against Sars-Cov-2, is the “Spike” protein. This antigen is present on the surface of the virus and is very flexible, showing different conformations over time. This flexibility makes its recognition, by the cells of the immune system, difficult. Through structural biology techniques the scientists were able to make the protein “Spike” more rigid, and stabilized in its pre-fusion trimeric form, making the antigen stable in the ideal conformation for the production of neutralizing antibodies resulting in the production of high levels of neutralizing antibodies. In addition, messenger RNA vaccines can have their genetic information rapidly altered, making it possible to stabilize the “Spike” protein already with the mutations present in the variants. Therefore, RNA vaccines are capable of providing protection superior to that conferred by the natural infection of the wild virus and its variants.

SBMT: What are the main challenges to expanding and enabling mRNA treatments?

Dr. Rafael Dhalia: The first big challenge is to enable clinical studies of mRNA vaccines. Evaluate the effectiveness of these vaccines in relation to protection against the most diverse diseases. Another huge challenge is to make its production and distribution viable, not only in the richest countries. There are projects aimed at building messenger RNA micro factories, which can enable the expansion of RNA vaccines, however these initiatives are still concentrated in a few countries. Finally, there are several studies aimed at optimizing the preservation of these molecules, allowing their storage under refrigeration conditions of a common refrigerator.

SBMT: With the arrival of vaccines on the market, should mRNA therapies become more popular?

Dr. Ernesto T. A. Marques: Absolutely. Several biotechnology industries that previously had no confidence in mRNA technology have come to believe in and invest in the development of products based on this technology. In fact, there are already drugs against autoimmune diseases that use mRNA. Furthermore, the more vaccines available, and the greater their use, the scaling and distribution technology becomes more affordable in terms of price. Free competition itself should force suppliers to have more competitive distribution prices.

SBMT: Would you like to add something?

Dr. Rafael Dhalia and Dr. Ernesto T. A. Marques: For about 30 years, RNA vaccine development initiatives had been viewed with suspicion, and no vaccine using this type of technology had been tested on a large scale in humans. The Sars-Cov-2 Pandemic forced us to quickly test these vaccines, even allowing the execution of different development phases simultaneously. Approval of mRNA vaccines for mass vaccination also occurred in record time. Little by little, what was seen with suspicion came to be seen with hope, given the promising results that have been observed. Even so, denial continues through the exaltation of rare cases of allergic reactions due to messenger RNA vaccination, even though it is known that more than 80% of cases were in individuals with a history of allergies, and completely recovered after vaccination. Several fake news are still circulating, such as the claim that the genetic material from RNA vaccines can be integrated into our genetic code. Conspiracy theory completely unfounded, since while messenger RNA is made up of a single strand of genetic material, DNA is a double strand present within the nucleus. Our cells are permanently producing mRNA to meet their survival needs, and these RNAs do not reintegrate into our DNA. The only possibility of integration would be in patients infected with a retrovirus, viruses that have the enzyme reverse transcriptase and integrases, where a series of rare events would be needed: reverse transcription of mRNA into DNA, transport of synthesized DNA into the nucleus and homologous recombination site-directed, if there was any sequence homologous with the genome of the immunized person. However, there is no homology between the mRNA of the SARS-CoV-2 virus and the DNA of the human host. The chance of these phenomena occurring tends to zero. So, it’s another disservice to society. RNA vaccines are safe, effective and very promising, promising to revolutionize current vaccination strategies. Messenger RNA synthesis platforms will be increasingly robust and should be used to meet the repressed demand not only for vaccines already in use, but will also allow us to respond quickly to possible and probable new pandemics.