Broad and systemic immune-modulating capacity of plant-derived dsRNA.

Double-stranded RNA (dsRNA) is well characterized as an inducer of anti-viral interferon responses. We previously reported that dsRNA extracted from a specific edible plant possesses an immune-modulating capacity to confer, in mice, resistance against respiratory viruses, including the H1N1 strain of the influenza A virus (IAV). We report here that the systemic immune-activating capacity of the plant-derived dsRNA protected mice from infection by a highly virulent H5N1 strain of the IAV. In addition, subcutaneous inoculation of the dsRNA together with the inactivated virion of the H5N1 strain of the IAV suppressed the lethality of the viral infection as compared with individual inoculation of either dsRNA or HA protein, suggesting its potential usage as a vaccination adjuvant. Moreover, intra-peritoneal inoculation of the dsRNA limited the growth of B16-F10 melanoma cells through the activation of NK cells in murine models. Taken together, this study demonstrated the systemic immune-modulating capacity of a plant-derived dsRNA and its potential for nucleic acid-based clinical applications.

A Plant-Derived Nucleic Acid Reconciles Type I IFN and a Pyroptotic-like Event in Immunity against Respiratory Viruses.

Nucleic acids carrying pathogen-associated molecular patterns trigger innate immune responses and are used to activate host immunity. Although synthetic nucleic acids have been used for that purpose, they have shown limitations for in vivo and clinical applications. To address this issue, we tested a naturally occurring dsRNA extracted from rice bran (rb-dsRNA) and characterized it as a potent ligand of TLR3 and MDA5. In this study, intranasal administration of rb-dsRNA induced production of type I IFNs by alveolar macrophages and protected mice from morbidity and mortality resulting from respiratory virus infection, such as influenza A virus. This protection was completely absent in mice lacking both TRIF and MDA5, indicating the essential role of TLR3- and MDA5-dependent pathways. Interestingly, IFNAR1-deficient mice retained residual antiviral protection, which was abolished by pharmacological inhibition of caspase 1, but not IL-1ß signaling. In fact, rb-dsRNA activated caspase 1 via TRIF, resulting in the release of IL-1ß and LDH. In addition to the direct antiviral activity, rb-dsRNA modulated the immune cell population in the lungs by repopulating virus-depleted alveolar macrophages. Our data demonstrate that rb-dsRNA orchestrates IFN-dependent and -independent direct antiviral protection and that it is a potent immune stimulator modulating antiviral immunity in the lungs. These findings open doors to a range of precise immune-modulating studies and therapeutic options.