Prenatal Cytokine Expression Profiles in An Autism High-Risk Pregnancy Cohort: Preliminary Results From the EARLI Study

Background:  Many studies document immune aberrations in children already diagnosed with autism, though few have examined immune influences during pregnancy. Levels of selected cytokines in maternal peripheral blood collected at one point during mid-pregnancy have been previously associated with increased risk for autism.   However, the pattern of cytokine expression over the entire pregnancy period has not been examined in relation to autism risk. 

Objectives:  To characterize the cytokine expression levels throughout pregnancy among mothers who have previously given birth to a child diagnosed with ASD.  Future analyses will relate cytokine expression levels during pregnancy with developmental outcomes and ASD status of the child.

Methods:  The Early Autism Risk Longitudinal Investigation (EARLI) study is designed to prospectively follow a population of pregnant women at elevated risk of giving birth to a child with ASD.  Comprehensive data are collected throughout pregnancy and during the first 3 years of life of the baby born into the study.  Venous blood samples (N=292) collected during the first, second, and third trimesters of pregnancy for the first 90 mothers enrolled in the study were analyzed.  Cytokines (eotaxin, GM-CSF, IFN-gamma, IL-1a, IL-1b, IL-2, IL-4, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-17, IP-10, MIP-1a, MIP-1b, MCP-1, RANTES, IL-1ra, TNF-a) were quantified by Luminex multiplex analysis technology. Linear models were used to determine trajectories of log transformed plasma cytokine levels in mothers over the course of pregnancy. Slope values ≥0.1 or ≤-0.1 were used to determine the % of women with increasing or decreasing cytokine levels over this time period. 

Results:  Among this high-risk pregnancy cohort, a panel of cytokines could be measured reliably in blood specimens collected throughout pregnancy, and a wide range of maternal cytokine expression was detected.  Trends in cytokine levels over the entire pregnancy period were detected but were not always in the expected direction. For instance, IL-10 concentrations are expected to increase over the pregnancy period, while IFN-gamma and IL-17 are expected to decrease until a gestational age of 33 weeks.  However, in this sample, 2.3% (N=2) of mothers had decreasing IL-10 concentrations, 11.5% (N=10) had increasing IFN gamma levels, and 6.9% (N=6) had increasing IL-17 levels. For three women, the pattern of expression of all three of these cytokines was in the opposite direction as expected, suggesting the presence of an inflammatory process during pregnancy in a subset of women at higher risk for having a second child with autism.

Conclusions:  Preliminary results indicate that the trajectories of cytokine expression in this high risk population of pregnant women are quite diverse.  Cytokine trajectories that deviate from the expected direction may be useful as early biomarkers for ASD risk in the child.  A three year follow-up of a total population of 1,000 successful births is planned, providing an unprecedented resource of biological and environmental data on an autism high-risk pregnancy cohort.  Once outcome data are available, this resource will enable the investigation of genetic, environmental, and immunological influences in the prenatal and early postnatal period on ASD risk.