A Commensal-Derived Lipoteichoic Acid Engages an Inducible Neuronal PD-1 Checkpoint to Suppress Inflammatory Pain.

BACKGROUND

Immune checkpoint receptors regulate adaptive immunity but are increasingly recognized as modulators of neuroimmune interactions. The upstream signals that induce neuronal checkpoint pathways during inflammation and their functional relevance in inflammatory pain remain incompletely understood. We investigated whether a defined commensal-derived molecule engages a neuroimmune checkpoint axis to modulate inflammatory pain.

METHODS

SELTA, a lipoteichoic acid purified from a commensal Staphylococcus epidermidis strain, was evaluated for TLR2-dependent activity, regulation of Pdcd1 transcription and PD-1 protein expression in dorsal root ganglion (DRG) neurons, effects on intracellular calcium signaling, and behavioral outcomes in experimental autoimmune prostatitis (EAP) a model of inflammation-induced chronic pelvic pain. Conditional Pdcd1 deletion was performed in sensory neurons (Advillin-Cre) and CD4+ T cells to determine cell-specific requirements.

RESULTS

SELTA selectively activated TLR2/6 signaling and increased Pdcd1 transcription and PD-1 protein expression in DRG neurons under inflammatory conditions. SELTA enhanced phosphorylation of PD-1 at tyrosine 248 and significantly reduced ATP-evoked intracellular Ca2+ responses in mouse primary sensory neurons. Pharmacologic neutralization of PD-1 abrogated SELTA-mediated suppression of calcium signaling. In vivo, SELTA produced concentration-dependent attenuation of pelvic hypersensitivity in EAP. Conditional deletion of PD-1 in vivo in Advillin-expressing sensory neurons or CD4+ T cells significantly reduced SELTA-induced analgesia, while combined deletion did not further diminish the effect.