Scientists may have discovered “universal vaccine”

Every year, researchers try to predict the four strains of the flu virus most likely to prevail in the next flu season.

Scientists at the University of California (United States) have revealed a new strategy for an RNA-based vaccine that is effective against any strain of a virus and safe even for babies and those with a weakened immune system.

The vaccine, how it works and a demonstration of its effectiveness in mice are described in an article published today in the scientific journal Proceedings of the National Academy of Sciences, according to a statement from the University of California – Riverside (UCR).

«What I want to highlight in relation to this vaccine strategy is that it is broad (…) applicable to any number of viruses, (…) effective against any variant of a virus and safe for a broad spectrum of people. This could be the universal vaccine we were looking for,” said Rong Hai, virologist at UCR and author of the article, cited in the statement.

Every year, researchers try to predict the four strains of the flu virus most likely to prevail in the next flu season and the updated vaccine should be taken annually.

The same happened with vaccines against SARS-CoV-2, the coronavirus that causes Covid-19, which were being reformulated to target subvariants of the dominant strains in circulation.

By targeting a part of the viral genome that is common to all strains of a virus, the new strategy will eliminate the need to create different vaccines.

“Traditionally, vaccines contain a live, killed or modified version of a virus. The body's immune system recognizes a protein in the virus and mounts an immune response", producing "T cells that attack the virus and prevent its spread" and "'memory' B cells that train the immune system" to prevent future attacks.

The vaccine now revealed “uses a modified live version of a virus”, but “does not depend” on the aforementioned immune response – so it can be taken by babies with an incipient immune system or by immunocompromised people –, but rather on small RNA molecules that silence the genes that cause the disease.

«A host – a person, a mouse, whoever is infected – will produce small interfering RNAs as an immunological response to the viral infection. These RNAi then kill the virus,” explained Shouwei Ding, professor of microbiology at UCR and main author of the article, cited in the statement.

Since viruses cause disease because they produce proteins that block the host's RNAi response, creating a mutant virus that cannot produce the protein to suppress RNAi weakens the virus.

"It can replicate to a certain extent, but then it loses the battle to the host's RNAi response," Ding said, adding: "a virus weakened in this way can be used as a vaccine to strengthen our RNAi immune system."

The new strategy was tested on mutant mice, lacking T and B cells, and it was found that with one injection of vaccine, the mice were protected from a lethal dose of the unmodified virus for at least 90 days (some studies show that nine days in rats are approximately equivalent to a human year). Even newborn mice produce small RNAi molecules, so the vaccine also protected them.

UC Riverside has already obtained a U.S. patent for this RNAi vaccine technology and the researchers' next step is to create a flu vaccine to protect children.

“If we are successful, they will no longer depend on their mothers’ antibodies,” said Ding.

Scientists say the chance of a virus having a mutation to avoid this vaccination strategy is still small.

“Viruses can mutate in areas not targeted by traditional vaccines. However, in this case, the target of the thousands of small RNAs is your entire genome. They cannot escape,” said Hai.

With a “cut and paste” strategy, researchers also believe they can make a single vaccine for any type of virus.

“There are several well-known human pathogens, such as dengue fever and SARS. They all have similar viral functions", so the new strategy "must be suitable for these viruses", said Ding.