C-852-03. Lung Prevotella Melaninogenica Is Enriched Post Burn + Inhalation Injury, and Reprograms Innate Immune Cells In Vitro

Abstract Introduction The lung microbiome has been implicated in immune dysregulation after burn with inhalation injury. We investigated whether Prevotella melaninogenica (PM) is detectable in bronchoalveolar lavage (BAL), whether PM or its products alter innate immune responses in vitro, and whether BAL PM burden correlates with inflammatory readouts. Methods BAL from patients (n = 12) with burn + inhalation injury underwent bacterial 16S rRNA microbiome profiling and targeted qPCR for a PM-specific genome sequence. In vitro, human monocyte, NK-cell, and neutrophil models were exposed to PM-conditioned broth (PMCB), with and without low-dose LPS stimulation, followed by multiplex cytokine assays and immune profiling for select cytokines and Damage-Associated Patterns (DAMPs). In a further cohort of patient BAL samples (n = 40), we enumerated PM-copy number using PM-specific qtPCR assay. Associations between PM copy number and other variables were tested using Spearman correlation with Benjamini-Hochberg false discovery rate (FDR) control. Results Prevotella was among the most prevalent airway taxa by 16S rRNA profiling. PMCB reprogrammed immune pathways and altered cytokine secretion across monocytes, neutrophils, and NK cells, with a consistent significant additive effect on TNF, IL-10, and IL-6 secretion compared to PMCB-free controls. In BAL, the PM-specific qPCR signal was positively associated with multiple measures, including BAL cell-free DNA (q = 0.0019; n = 40), and IL-6 concentration (q = 0.0269), but not any other cytokine or other DAMP tested. These remained significant after adjustment for days post injury, sex, and TBSA. Conclusions PM is prevalent in the injured airway, PM products reprogram innate immune cells in vitro, and BAL PM burden correlates with airway inflammation. These findings support a model in which PM contributes to maladaptive innate immune signaling after inhalation injury. Applicability of Research to Practice Early identification of PM and targeted modulation of PM-driven pathways may enable risk stratification and immune-focused interventions to reduce pulmonary complications after burn with inhalation injury. Funding for the study Funded by NIGMS and NHLBI.