292 - Quantifying complement proteins in pediatric CSF as potential markers of CNS pruning and pathology

Publication Number: 4287.292

Hannah Yen, Boston Children's Hospital, Beverly, MA, United States; Daniel Wilton, Boston Children's Hospital, Boston, MA, United States; Maria Goldman, Boston Children's Hospital, Cambridge, MA, United States; Hanne Van der Heijden, Harvard Medical School, Boston, MA, United States; Erin Borglund, Boston Children's Hospital, Boston, MA, United States; Ryan Guardado, Boston Children's Hospital, Brighton, MA, United States; Maya J. Golden, Boston Children's Hospital, Boston, MA, United States; Matthew B.. Johnson, Broad Institute of MIT and Harvard, Boston, MA, United States; Beth Stevens, Boston Children's Hospital, Milton, MA, United States

Background: There is a crucial need to identify biological markers that reflect aspects of neurodevelopmental disease progression, to predict onset of symptoms and help inform treatment decisions. Genetic studies and postmortem expression data have shown dysregulation of complement proteins in individuals with neurological disorders, implicating the role of these proteins-important constituents of the innate immune system-in the pathogenesis of these disorders. The ability to evaluate complement as potential biomarkers is complicated by the fact that the levels of these proteins are not well characterized prior to the onset of clinical symptoms.

Objective: Our aim is to measure the levels and activity of select complement proteins (C3, C4, and iC3b) in the cerebrospinal fluid (CSF) of pediatric patients undergoing diagnostic screening. We seek to measure impacts of developmental age, sex, and diagnoses, with a particular focus on psychosis conditions.

Design/Methods: CSF was obtained from 161 pediatric patients from 0 to 23 years undergoing diagnostic lumbar punctures for various conditions (e.g. idiopathic intracranial hypertension/IIH, seizure/epilepsy, psychosis). The numbers of males and female patients were comparable.
Complement protein levels and activity in the CSF were measured using novel sandwich ELISA assays developed in-house and assessed for specificity and sensitivity using purified proteins, complement activators and depleted serum. All samples were run in quadruplicates and held under strict criteria for re-testing on the basis of cumulative variance ( < 25%). Dilution linearity thresholds were enforced.

Results: Complement levels showed age-dependent changes independent of diagnoses, as well as sex-specific differences appearing around 10 years of age, coinciding with the onset of puberty. Levels of iC3b were specifically elevated in psychosis patients.

Conclusion(s): Age- and sex-specific changes in complement protein levels suggest their potential as biomarkers for early-onset neurological disease. Elevated iC3b in pediatric patients with psychosis is similar to preliminary data our group has gathered from adults with schizophrenia, highlighting the potential role for iC3b in predicting risk for schizophrenia. Future directions include validation of our findings at other sites.

Figure 1. Demographic and diagnostic breakdown of the pediatric donor population
(A) The frequency of different diagnostic indications represented in the CSF collection. (B) The distribution of patient ages comprising the CSF collection.

Figure 2. Complement levels in pediatric CSF is impacted by patient age and diagnoses.
(A) CSF complement protein levels displayed as a function of patient age. (B) CSF complement protein levels in patients diagnosed with IIH, psychosis, or a neuroimmunology indication.