Defective interfering (DI) RNAs are naturally occurring truncated viral RNAs generated during the replication of most RNA viruses. These RNAs contain deletions and mutations that distinguish them from full-length viral genomes. While these RNAs are termed "defective" due to their inability to independently generate complete viruses or replicate efficiently, DI RNAs can profoundly influence viral pathogenesis through viral interference and activation of host antiviral immune responses. In the presence of a helper virus, DI RNAs can be packaged into virions to form defective interfering particles (DIPs), which facilitate their transmission between cells.
Our research focuses on DI290 RNA, a 290-nucleotide RNA identified in dengue virus (DENV)-infected cell cultures and human clinical samples. We demonstrate that delivery of DI290 via DIPs or lipid nanoparticles effectively suppresses DENV infection in both in vitro and in vivo models. Mechanistic studies revealed that DI290 is recognised by host pattern recognition receptors (PRRs), resulting in activation of interferon signalling and induction of interferon-stimulated genes (ISGs) that establish a robust antiviral state. In addition to inhibiting DENV replication, DI290 exhibited broad-spectrum antiviral activity against multiple RNA viruses, including respiratory syncytial virus, yellow fever virus, Zika virus, Japanese encephalitis virus and SARS-CoV-2.
Collectively, our findings demonstrate that DI290 functions as a potent innate immune agonist and broad-spectrum antiviral RNA. These results highlight the potential of DI290 as a novel RNA-based therapeutic platform for the treatment of viral infections.