RNA is often described as the single-stranded cousin of DNA, the double-stranded molecule that makes up the genomes of all living organisms. Many types of non-living viruses, however, carry their genetic information in a double-stranded form of RNA (dsRNA). When the human immune system detects the presence of this foreign RNA, it sounds the alarm by increasing the production of protective cytokines called interferons (IFN), which activate the innate immune response against viral invaders.

Scientists have attempted to harness this natural antiviral response by creating therapeutic dsRNAs that mimic features of viral genomes. But meddling with the innate immune system is a double-edged sword. Viral RNA analogs can also activate molecular pathways that lead to excessive inflammation in the body, which could cause more harm than their antiviral benefits.

Now, a group of researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University has discovered a new class of immunostimulatory dsRNAs that potently induces the production of two forms of IFN (IFN-I and IFN-III) while limiting the inflammation commonly observed with previous types of RNA-based immunostimulants.

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