Conventional mRNA vaccines, which proved central to the response to the Covid-19 pandemic, work by delivering instructions that tell cells to build a protein the immune system can learn to recognize. Unlike traditional vaccines that use a weakened or inactivated dose of a pathogen, RNA vaccines hand the body a molecular blueprint. The approach proved fast, flexible, and scalable, but conventional mRNA is transient: each molecule yields a limited amount of protein before it is degraded, which is why booster doses have been needed to sustain immunity.

Self-amplifying mRNA takes a different approach. Derived from the replication machinery of certain viruses, saRNA carries the genetic instructions not only for a target antigen but also for the machinery needed to copy itself inside host cells. In principle, a single saRNA molecule can generate many copies of itself and, in turn, far more antigen than a conventional mRNA dose. That amplification suggests that much smaller quantities of vaccine could deliver equivalent or longer-lasting protection, an advantage that could matter enormously for pandemic preparedness, for reaching populations in resource-limited settings, and for applications well beyond infectious disease.

The problem lies in what the amplification process leaves behind. As saRNA replicates inside a cell, it inevitably generates double-stranded RNA, or dsRNA, a molecular signature that mammalian cells treat as an alarm bell for viral infection. Antiviral defenses keyed to dsRNA respond by restricting the replication of the saRNA, making it less stable, less able to copy itself, and less effective at instructing the cell to produce the protein that trains the immune system. This built-in conflict between the vaccine and the cell’s own defenses has been a fundamental barrier limiting how potent an saRNA vaccine can be.

Dr Pierre Maillard and Dr Raul Yusef Sanchez David, scientists at Queen Mary University of London’s Blizard Institute, identified a way to ease that conflict. Their strategy involves NoV B2, a protein derived from Nodamura virus that is known to suppress RNA interference, one of the cell’s natural defenses against double-stranded RNA. When the researchers added NoV B2 alongside saRNA, the protein reduced the extent to which cells restricted the replicating vaccine RNA. The result was a marked increase in the amount of target protein produced, an effect the team observed in both stem cells and regular cells.

Crucially, the enhancement came without undermining the saRNA’s ability to stimulate the immune system. That balance matters, because any strategy that simply silenced cellular antiviral responses wholesale could risk blunting the very immune activation a vaccine depends on. By specifically tuning the intracellular response to double-stranded RNA, the Queen Mary team preserved the immunological signal while freeing the vaccine to amplify more effectively. The researchers describe the approach as tuning intracellular immunity, a phrase that captures the precision of the intervention.

The implications extend well beyond infectious disease. Because saRNA can drive sustained production of therapeutic proteins inside cells, the same technology underpins efforts in gene therapy, cancer immunotherapy, and protein replacement therapies. If the protein-boosting effect observed in the laboratory translates successfully in living organisms, the Queen Mary team’s innovation could make gene therapy safer and more affordable, make cancer vaccines more potent, and transform protein replacement therapy from a regimen of repeated infusions into a process in which a patient’s own body generates the medicine it needs.

Dr Maillard emphasized the broader significance of the result. The findings, he said, identify a strategy to overcome a fundamental barrier limiting self-amplifying vaccines, and if they translate successfully in vivo, they could open new possibilities for vaccine design as well as for gene therapies and cancer treatment. The team is now working with Queen Mary Innovation, the university’s technology transfer company, to find a commercial partner to help develop the technique for clinical use, a step that will determine how quickly the laboratory advance reaches patients.

The advance arrives at a moment of uncertainty for the field. The United States has announced 500 million dollars in cuts to mRNA vaccine research, a decision that sparked widespread concern across the global scientific and public health communities. Against that backdrop, the Queen Mary work has been framed by the university as evidence of the continued strength of the United Kingdom as a place to invest in impactful research and innovation. Whether saRNA vaccines fulfill their promise of protection at lower doses, rolled out further and faster than previously imaginable, will depend on how the technology performs in the clinic, but the barrier that once seemed inherent to the platform has now been shown to be one that can be engineered away.

Subject of Research: Cells

Article Title: Scientists overcome key barrier to self-amplifying vaccines

Article References: Scientists overcome key barrier to self-amplifying vaccines. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: self-amplifying mRNA, saRNA vaccines, NoV B2 protein, double-stranded RNA, Queen Mary University of London, Nature Communications, Scientists, overcome, barrier, self-amplifying, vaccines, scientific research