The role of persistent inflammation in failed recovery after perinatal brain injury: is resolution the cure?

Perinatal brain injury (PBI) is a major predictor of neurological disability. Commonly associated with prematurity, infection, stroke, hypoxia-ischemia, hemorrhage, and/or toxin exposure, PBI triggers acute and persistent systemic inflammation. There are many stages of vulnerability to PBI during development including pregnancy, birth - term and preterm, and neonatal age. The vulnerable stages can compound inflammation through injury to the placental-fetal-brain axis, adaptive and innate immune system development, neural-immune communication, and central nervous system maturation. Neonates exhibit unique inflammatory signatures and lasting neural-immune responses to various etiologies. Chronic immune dysregulation and priming to a secondary, later-in-life immune challenge defines different forms of PBI while shaping the neonatal and adult immune response with long-term changes. Immunomodulated changes impact regulatory, helper and innate T cells, neutrophils, natural killer cells and immune responsiveness. The major routes of persistent and compounding inflammation in PBI are perinatal neural-immune interactions, cytokine influx, and glial crosstalk. Most treatments are not administered long enough or in the optimal time window to combat sustained inflammation in tertiary and quaternary phases of PBI pathophysiology and are ineffective in reducing neonatal mortality and morbidity and promoting functional recovery. Indeed, persistent systemic and central inflammation is a likely explanation for failed recovery of PBI after the resolution of acute insults. We propose attenuating persistent inflammation and normalizing systemic immune reactivity as key to reducing the functional impact of PBI throughout the lifespan through various avenues including therapeutic treatment, gut microbiome modulation, and novel immunomodulation from preclinical research.