Independent of their target, phosphorothioate (PS)-modified 2’-O-Methyl (2’-OMe) gapmer antisense
oligonucleotides (ASO) are frequent inhibitors of innate immune nucleic acid sensors, including human
TLR3, TLR7, TLR9, and cGAS (Valentin et al., Nucleic Acids Research 2021), a finding that has
important implications for their therapeutic development.
Here, we evaluated the immunomodulatory activity of a non-targeting ASO with pan-inhibitory activity on
TLR3, TLR7 and cGAS, referred to as C2-Mut1, on viral lung infections. Therapeutic intranasal
administration of naked C2-Mut1 significantly decreased aberrant antiviral interferon responses following
Influenza A virus infection, without impacting immune cell recruitment in the bronchoalveolar lavage fluid.
Counterintuitively, this anti-inflammatory activity of C2-Mut1 also resulted in decreased viral titres in the
lung and a reduced weight-loss. Preliminary studies indicated that, when administered intranasally to
SARS-CoV-2-infected K18-hACE2 mice, C2-Mut1 dampened select antiviral markers, and potentiated
the production of pro-inflammatory factors, such as IL-6 and CXCL1. While further studies are currently
ongoing, these findings establish the capacity of intranasal 2’OMe ASOs to modulate virus-driven
inflammation, which we propose emanates from the pan-inhibition of nucleic acid-sensing pathways that
are engaged during infection.
Given the sequence-specific nature of our observations and the non-targeting activity of our ASO, our
results constitute proof-of-principle that 2’OMe gapmer ASOs can exhibit significant immunomodulatory
activities during viral infections, independent of their gene targeting activities. While such
immunosuppressive effects should be considered further in the therapeutic development of ASOs, our
findings also support the potential therapeutic application of pan-inhibitory oligonucleotides for the
management of viral-induced lung hyper-inflammation.