Stenvik, J. | Search bioRxiv

bioRxiv2025

SLAMF1-peptide mediated epigenetic priming reprograms innate immune responses in sepsis

Sepsis is characterized by profound immune dysregulation, including impaired innate immune responses and epigenetic reprogramming of monocytes. However, strategies to therapeutically restore immune function remain limited. Here, we identify a cell-penetrating peptide, P7-Pen, as a modulator of monocyte epigenetic state and inflammatory responsiveness. Using primary human monocytes and peripheral blood mononuclear cells (PBMCs) from healthy donors and sepsis patients, we demonstrate that P7-Pen enhances cytokine production in response to Toll-like receptor stimulation while having minimal effects under basal conditions. P7-Pen treatment increased global histone acetylation, particularly H3 acetylation, and prevented the development of endotoxin tolerance. Transcriptomic and functional analyses revealed restoration of inflammatory gene expression, including TNF, IL6, and IFNB1, in otherwise hyporesponsive cells. Mechanistically, we identified the lysine deacetylase ABHD14B as a direct binding partner of P7-Pen. Silencing of ABHD14B recapitulated the effects of P7-Pen, leading to enhanced histone acetylation and cytokine production. Importantly, P7-Pen selectively potentiated responses to TLR ligands without inducing basal hyperinflammation. Collectively, our findings identify ABHD14B-dependent epigenetic regulation as a key checkpoint in innate immune tolerance and establish P7-Pen as a novel tool to restore immune responsiveness in sepsis.

immunology↗

bioRxiv2025

A novel TIRAP-MyD88 inhibitor blocks TLR7- and TLR8-induced type I IFN responses

Endosomal toll-like receptors TLR7 and TLR8 are critical sensors of microbial RNA that initiate antiviral and antibacterial immune responses through type I interferon (IFN) and proinflammatory cytokine production. While TIRAP is traditionally associated with plasma membrane TLR signaling, recent evidence suggests it also contributes to signaling via endosomal TLRs. Here, we examined the role of TIRAP in TLR7/8 signaling using P7-Pen, a novel SLAMF1-derived peptide that disrupts the TIRAP-MyD88 interaction. In primary human monocytes and a whole blood model, P7-Pen inhibited TLR7- and TLR8-induced expression and secretion of IRF5-regulated cytokines IFN{beta}, IL-12p40, and IL-12p70, without effect on TNF or IL-6. Mechanistically, P7-Pen blocked TIRAP recruitment to the TLR8-MyD88 complex, leading to reduced late-stage IRAK1 activation, Akt and IKK/{beta} phosphorylation, and downstream IRF5 dimerization and nuclear translocation. Inhibition of Staphylococcus aureus-induced cytokine production by P7-Pen was associated with reduced bacterial phagocytosis, impairing endosomal delivery of bacterial RNA. Notably, P7-Pen failed to inhibit murine TLR7 responses, which correlated with a lack of TIRAP recruitment to MyD88 in mouse macrophages following TLR7 ligand stimulation, highlighting species-specific differences in TLR signaling mechanisms. These findings support a noncanonical role for TIRAP in regulating IRF5-dependent signaling downstream of human TLR7 and TLR8, and demonstrate that selective disruption of TIRAP recruitment by a SLAMF1-derived peptide effectively attenuates IFN{beta} production. This strategy may hold therapeutic potential in diseases characterized by dysregulated type I IFN responses, such as systemic lupus erythematosus and chronic infections.

immunology↗