IL-33-Driven Macrophage Reprogramming as a Potential Immunometabolic Strategy for Herpes Simplex Keratitis

Background: Herpes simplex keratitis (HSK), caused by herpes simplex virus type 1 (HSV-1), is a major cause of infectious blindness. Macrophages are key antiviral effector cells, yet the metabolic mechanisms driving their protective responses remain poorly defined. This study aimed to determine whether interleukin-33 (IL-33) modulates macrophage metabolism and function to enhance antiviral protection in HSK. Methods: Bone marrow-derived macrophages (BMDMs) were stimulated with IL-33, followed by phenotypic and functional characterization using qRT-PCR, flow cytometry, and immunofluorescence. Integrated transcriptomic and non-targeted LC-MS metabolomic profiling was performed to uncover regulatory pathways. For in vivo validation, differently treated BMDMs were adoptively transferred subconjunctivally into a mouse HSK model. Clinical scoring, fluorescein staining, TCID₅₀ quantification of tear samples, and corneal viral gene detection were used to evaluate disease severity and viral burden. Results: IL-33 stimulation increased CD169 and MHC-II expression, expanded the CD169⁺ macrophage subset, and suppressed HSV-1 replication in vitro. Multi-omics integration identified 616 differentially expressed genes and 417 differentially expressed metabolites, revealing substantial remodeling of lipid and amino acid metabolism and suggesting a critical IL-33-lipoprotein lipase (LPL)-palmitoylcarnitine (L-PC) metabolic axis. In vivo, prophylactic adoptive transfer of IL-33-treated BMDMs significantly reduced corneal opacity, epithelial injury, tear viral titers, and virogene expression. LPL inhibition eliminated these benefits, whereas L-PC supplementation partially restored antiviral and clinical improvements. Conclusions: IL-33 reprograms macrophages toward a CD169⁺ antiviral phenotype through an LPL-dependent metabolic pathway, establishing an LPL-L-PC axis essential for enhanced antiviral function and protection against HSK. These findings highlight metabolic tuning of macrophages as a potential preventive immunomodulatory approach for HSV-1-induced ocular disease.