Presentation of multiple copies of a non-dominant surface epitope by circular RNA effectively induce an immune...

There is a pressing need for vaccine development platforms that are rapid, effective, and adaptable to emerging pathogens such as SARS-CoV-2. Circular RNA (circRNA) offers advantages in stability and non-immunogenicity over traditional mRNA approaches. We aimed to investigate the effect of increasing the amplification of a non-dominant surface epitope in the circRNA structure on the induction of an immune response to that epitope in a mouse model.

Two circRNA constructs containing one and ten copies of an epitope were designed using immunoinformatic methods, and their impact on immune responses was investigated. Immunogenicity in mice was assessed by antibody assays, virus neutralization assays, and cytokine analysis.

The titer of anti-SARS-CoV-2 RBD-specific IgG antibody in mice treated with circRNA containing ten copies of the epitope was significantly higher than that in mice treated with circRNA containing a single copy of the epitope. The level of neutralizing antibodies in the circRNA containing ten copies of the epitope was also significantly higher than that in the single-copy group. In addition, the levels of cytokines IFN-γ, TNF-α, and IL-2 were significantly higher in the circRNA containing ten copies of the epitope than in the single copy group.

Combining copy number amplification of a candidate epitope with a circRNA platform could lead to a powerful construct for enhancing immune responses. This approach may offer significant potential for controlling emerging infectious diseases in the future.