A plasmid-loaded biomimetic nanoplatform targeting the PAD2-METs-OPN axis against recurrent herpes simplex keratitis.

The high recurrence rate of herpes simplex keratitis (HSK) is primarily attributed to the reactivation of herpes simplex virus type 1 (HSV-1) within the trigeminal ganglion (TG), a latent viral reservoir cannot be eradicated by current antiviral or anti-inflammatory therapies. This study aims to elucidate the novel immune mechanisms regulating viral reactivation within the TG and to develop a targeted therapeutic strategy based on this mechanism. We found that macrophages are the key effector cells inhibiting viral reactivation in recurrent HSK models, exerting their core antiviral function through the release of macrophage extracellular traps (METs) rather than neutrophil extracellular traps (NETs). Mechanistically, MET formation is highly dependent on the activity of peptidylarginine deiminase 2 (PAD2). Importantly, METs function not merely as physical capture structures but act as signaling vehicles by releasing osteopontin (OPN) as a key messenger. OPN activates the expression of the interferon-stimulated gene ISG15 in adjacent neurons, thereby establishing a previously unrecognized "PAD2-METs-OPN-Neuron ISG15" immune-neuron synergistic antiviral axis. To translate this mechanism into a therapeutic strategy, we engineered a lipid nanoparticle encapsulating a PAD2-overexpressing plasmid, which was further camouflaged with macrophage membranes to construct the biomimetic delivery system pPAD2@MNPs. Unlike conventional gene delivery platforms, this system leverages the "homing effect" via VLA-4/LFA-1 on the membrane surface binding to VCAM-1/ICAM-1 at inflammatory sites, this system achieves precise targeting of TG lesions. In vivo experiments confirmed that local administration of pPAD2@MNPs significantly upregulates PAD2 expression within the TG, effectively reducing viral load and improving corneal pathology scores. Furthermore, biosafety evaluations revealed no significant systemic toxicity or major organ damage induced by this nano-system. In summary, this study reveals a novel mechanism of immune-neuron crosstalk in regulating HSV-1 latency within the TG and provides a safe and effective targeted nanomedicine strategy for the radical treatment of recurrent HSK.