Neonatal Cytokines and Chemokines and Risk of Autism Spectrum Disorder: The Early Markers for Autism (EMA) Study

Background:  Markers of inflammation and/or infection have been associated with autism spectrum disorders (ASD) but prior studies have largely relied on specimens taken after clinical diagnosis. Research on biologic markers early in neurodevelopment is required to evaluate possible causal pathways and screening profiles. Cytokines and chemokines are immune signaling molecules and growth factors that can also affect neuronal development.

Objectives:  To investigate levels of cytokines/chemokines in newborn blood specimens as possible early biologic markers of dysregulation for autism.

Methods:  We conducted a population-based case-control study nested within the cohort of infants born from July 2000 – September 2001 to women who participated in the prenatal screening program in Orange County, California. Cases (n = 84) were all children receiving services for autism spectrum disorder (ASD) at the Regional Center of Orange County. Two comparison groups from the same study population were included:  children with developmental delay (DD, n = 49) receiving services at the same regional center, and children not receiving services for developmental disabilities, randomly sampled from the California birth certificate files and frequency-matched to autism cases on sex, birth year, and birth month (GP, n =159).

Neonatal cytokine and chemokine concentrations were measured in archived newborn screening bloodspots maintained by the California Department of Public Health using a commercially available multiplex bead-based kit (BioSource Human Bead Kit; Invitrogen, Carlsbad, CA, USA). The following cytokines and chemokines were measured: IFN-γ, IL-2, IL-4, IL-5,  IL-6, IL-1β, IL-8, IL-10, IL-12p40, tumor necrosis factor alpha (TNF-α), granulocyte macrophage colony-stimulating factor (GM-CSF), IFN-γ-induced protein 10 (IP-10), MCP-1, Macrophage Inflammatory Protein-1alpha and 1beta (MIP-1α ,MIP-1β), RANTES and EOTAXIN. The assays were carried out in accordance with the protocols provided by the manufacturer. We compared levels of cytokines/ chemokines among ASD vs. GP and DD vs. GP using crude and multivariate logistic regression analyses.

Results: Cytokines were not detected in the vast majority of newborn samples regardless of case or control status. However, ASD cases were more likely than GP controls in a multivariate analysis to have levels of MCP-1 above the 90th percentile (odds ratio (OR) = 3.72, 95% confidence interval (CI) 1.56 – 8.86). They were significantly less likely to have levels of RANTES (OR = 0.36, 95% CI 0.15 – 0.85) above the 10^thpercentile of the GP controls. The DD group was also less likely to have levels of RANTES (OR = 0.31, 95% CI 0.11 – 0.87) and MIP-1α (OR = 0.33, 95% CI 0.12 – 0.91) above the 10th percentile of the GP controls.

 Conclusions: Measurement of newborn levels of the chemokines MCP-1, RANTES and MIP-1α might be useful in understanding mechanisms of early abnormal neurodevelopment. Each of these chemokines plays a role in neuron development. While often associated with inflammation, sufficient levels of these chemokines are needed for healthy neuronal migration. Therefore, changes in levels during critical windows of development could alter neurodevelopmental outcome.