AAV Genome's ITR Structure and Innate Immune Activation: A Focus on RLR-MAVS Signaling

The inverted terminal repeat (ITR) structure of the adeno-associated virus (AAV) genome can activate cytoplasmic DNA receptors. Studies have demonstrated that recombinant AAV (rAAV) can induce cyclic GMP-AMP synthase (cGAS) and antiviral genes, such as tumor necrosis factor-alpha (TNF-\u03b1) and interferon-gamma (IFN-\u03b3). The ITR, located at either end of the AAV or within the bidirectional promoter, can generate reverse complementary positive-strand RNA and negative-strand RNA. These RNA molecules can form double-stranded RNA (dsRNA) in target cells, subsequently triggering the innate immune response mediated by the dsRNA recognition receptor. Retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), acting as cytoplasmic RNA sensors, activate downstream innate immune signaling pathways through the adaptor protein mitochondrial antiviral signaling (MAVS). RLRs, including melanoma differentiation-associated gene 5 (MDA5), RIG-I, and laboratory of genetics and physiology 2 (LGP2), are RNA-binding proteins. MDA5 and RIG-I recognize the dsRNA formed by AAV, thereby activating the RLR-MAVS signaling pathway to produce interferon-beta (IFN-\u03b2).