Biology subjects

Schlee, M.

Publications and source records attributed to Schlee, M..

4 recordsLinked to original sources

bioRxiv2022

RIG-I activation primes and trains innate antiviral immune memory

Adaptive processes of the innate immune system, known as trained immunity (TI), are critical to human health and disease, yet they have not been systematically investigated downstream of antiviral sensing. Here, we elucidate the potential of the antiviral cytosolic RNA receptor retinoic acid-inducible gene I (RIG-I) to train, prime and tolerize the innate immune system. Using a specific RIG-I agonist, we observed that repetitive stimulation enhanced interferon-stimulated gene (ISG) and pro-inflammatory cytokine induction in human primary monocytes, epithelial cells and fibroblasts and afforded non-specific antiviral protection. RNA sequencing revealed broad, cell type-specific transcriptional changes, indicative of priming of ISGs and training of the NF{kappa}B pathway, without measurable tolerization, while ATAC sequencing in monocytes demonstrated chromatin remodeling and enhanced accessibility of key transcription factor-binding motifs such as STAT1. Moreover, while STAT1 signaling was critically required, it was not sufficient to recapitulate RIG-I induced TI. Altogether, our data demonstrate that RIG-I-mediated TI promotes an immunologically alert state with important implications for host defense and the application of RIG-I ligands in anti-infective and anti-tumoral therapies. One Sentence SummaryRIG-I activation trains and primes innate immune response at the cellular level, affording non-specific immune protection by immune and non-immune cells.

immunology↗

bioRxiv2022

A conserved isoleucine in the binding pocket of RIG-I controls immune tolerance to mitochondrial RNA

RIG-I is a cytosolic receptor of viral RNA essential for the immune response to numerous RNA viruses. Accordingly, RIG-I must sensitively detect viral RNA yet tolerate abundant self-RNA species. The basic binding cleft and an aromatic amino acid of the RIG-I C-terminal domain(CTD) mediate high-affinity recognition of 5triphosphorylated and 5base-paired RNA(dsRNA). Here, we found that, while 5unmodified hydroxyl(OH)-dsRNA demonstrated residual activation potential, 5-monophosphate(5p)-termini, present on most cellular RNAs, prevented RIG-I activation. Determination of CTD/dsRNA co-crystal structures and mutant activation studies revealed that the evolutionarily conserved I875 within the CTD sterically inhibits 5p-dsRNA binding. RIG-I(I875A) was activated by both synthetic 5p-dsRNA and endogenous long dsRNA within the polyA-rich fraction of total cellular RNA. RIG-I(I875A) specifically interacted with a long, highly structured, polyA-bearing, non-coding mitochondrial(mt) RNA, and depletion of mtRNA from total RNA abolished its activation. Altogether, our study demonstrates that avoidance of 5p-RNA recognition is crucial to preventing mtRNA-triggered RIG-I-mediated autoinflammation.

immunology↗

bioRxiv2021

Ionizing radiation improves RIG-I mediated immunotherapy through enhanced p53 activation in malignant melanoma

Radiation therapy induces cytotoxic DNA damage, which results in cell-cycle arrest and activation of cell-intrinsic death pathways, but its application has been limited by the radioresistance of tumors, such as in malignant melanoma. RIG-I is a cytosolic immune receptor expressed in all somatic cells, including tumor cells, with a key role in sensing viral RNA. RIG-I specific oligonucleotide ligands elicit a robust cell-intrinsic antiviral response and immunogenic cell death in tumor cells and are being tested in clinical trials. Nonetheless, their potential to overcome radioresistance has not yet been explored. Here, we demonstrate that activation of RIG-I enhances the extent and immunogenicity of irradiation-induced tumor cell death in human and murine melanoma cell lines in vitro and improved survival in the murine B16 melanoma model. Pathway analysis of transcriptomic data revealed a central role for p53 downstream of the combination treatment, which was corroborated using p53-/- B16 cells. In vivo, the effect of irradiation on immune-cell activation and inhibition of tumor growth was absent in mice carrying p53-/- B16 tumors, while the response to RIG-I stimulation in those mice was maintained. Our results identify p53 as pivotal for the synergistic antitumoral effect of RIG-I and irradiation, resulting in potent induction of immunogenic tumor-cell death. Thus, the administration of RIG-I ligands in combination with radiotherapy is a promising therapeutic approach to treating radioresistant tumors with a functional p53 pathway, such as malignant melanoma.

immunology↗

bioRxiv2021

RIG-I-induced innate antiviral immunity protects mice from lethal SARS-CoV-2 infection

The SARS-CoV-2 pandemic has underscored the need for rapidly employable prophylactic and antiviral treatments against emerging viruses. Nucleic acid agonists of the innate immune system can be administered to activate an effective antiviral program for prophylaxis in exposed populations, a measure of particular relevance for SARS-CoV-2 infection due to its efficient evasion of the host antiviral response. In this study, we utilized the K18-hACE2 mouse model of COVID-19 to examine whether prophylactic activation of the antiviral receptor RIG-I protects mice from SARS-CoV-2 infection. Systemic treatment of mice with a specific RIG-I ligand one to seven days prior to infection with a lethal dose of SARS-CoV-2 improved their survival of by up to 50 %. Improved survival was associated with lower viral load in oropharyngeal swabs and in the lungs and brain of RIG-I-treated mice. Moreover, despite antiviral protection, the surviving mice that were treated with RIG-I ligand developed adaptive SARS-CoV-2-specific immunity. These results reveal that prophylactic RIG-I activation by synthetic RNA oligonucleotides is a promising strategy to convey short-term, unspecific antiviral protection against SARS-CoV-2 infection and may be a suitable broad-spectrum approach to constraining the spread of newly emerging viruses until virus-specific therapies and vaccines become available.

immunology↗