The interferon-ɣ inducible factor 16 (IFI16) restricts adeno-associated virus serotype 2 (AAV2) transduction in an immune-modulatory independent way

Abstract

We determined the transcription profile of AAV2-infected primary human fibroblasts. Subsequent analysis revealed that cells respond to AAV infection through changes in several significantly affected pathways including cell cycle regulation, chromatin modulation, and innate immune responses. Various assays were performed to validate selected differentially expressed genes and confirmed not only the quality but also the robustness of the raw data. One of the genes upregulated in AAV2 infected cells was the interferon- γ inducible factor 16 (IFI16). IFI16 is known as a multifunctional cytosolic and nuclear innate immune sensor for double-stranded, as well as single-stranded DNA, exerting its effects through various mechanisms, such as interferon response, epigenetic modifications, or transcriptional regulation. IFI16 thereby constitutes a restriction factor for many different viruses amongst them, as shown here, AAV2 and thereof derived vectors. Indeed, the post-transcriptional silencing of IFI16 significantly increased AAV2 transduction efficiency, independent of the structure of the virus/vector genome. We also show that IFI16 exerts its inhibitory effect on AAV2 transduction in an immune-modulatory independent way, by interfering with Sp1-dependent transactivation of wild-type AAV2 and AAV2 vector promoters.