IL-17 in serum and cerebrospinal fluid of pediatric patients with acute neuropsychiatric disorders: implications for PANDAS and PANS

Background: Acute neuropsychiatric disorders are heterogeneous conditions resulting from interaction between genetic and environmental features. Among these, post infectious forms like Pediatric Acute-onset Neuropsychiatric Syndrome (PANS) and Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS) are common. Preclinical studies suggest a role of CNS T-helper-17/interleukin-17 (IL-17) inflammatory mediated response in the pathogenesis of these disorders. We analyze serum and cerebral-spinal fluid (CSF)-IL-17 concentrations in a cohort of patients with acute neuropsychiatric disease. Methods: We retrospectively included patients <14 years with acute neuropsychiatric symptoms from 2016 to 2020. IL-17 was determined on serum and CSF by means of quantitative sandwich enzyme immunoassay technique, and values were compared to serum and CSF controls. Variables were identified using univariate analysis with Pearson's regression test and X2 test. Results: 58 subjects were included (67.8 % males, average age: 8.5 years). 50.8 % were classified as PANDAS, 11.8 % as PANS. Mean concentrations of serum IL-17 were higher in the study group compared to controls (p < 0.0001). We observe a trend of increasing IL-17 in post-pubertal children both on serum (p = 0.05) and on CSF (p = 0.04). Coupled IL-17 concentration were higher in the CSF than in serum (p = 0.003), with a marked significance in the PANDAS and PANS group (p < 0.001). Conclusion: IL-17 is elevated in children and adolescents with acute neuropsychiatric conditions, both on serum and CSF. IL-17 could be involved in the pathogenesis of acute neuropsychiatric disorders in childhood. Further studies are necessary to validate its potential role as a diagnostic or prognostic biomarker.