UC Davis

Maternal immune dysregulation is considered the crucial link connecting the maternal environment and altered fetal neurodevelopment and immune function. Thus, elucidating the impact of the maternal immune response during gestation on offspring developmental outcomes is of critical importance. Studies reveal that maternal immune perturbation, autoimmune diseases, asthma, allergies, and chronic inflammation during gestation are associated with significantly heightened risks of various neurodevelopmental disorders in offspring. Similarly, evidence suggests that the maternal immune system actively influences the development and functionality of the fetal immune system in a process known as immune imprinting, or training. While previous studies delineate the association between the gestational maternal environment with NDD diagnosis, as well as maternal-fetal immune imprinting, significant gaps persist in our comprehension of the role of maternal immune dysregulation in both the genesis of NDDs and its enduring impact on offspring immune function.

In this dissertation, I employed the use of a translationally relevant, maternal immune activation (MIA) nonhuman primate (NHP) model to investigate immune dysfunction and abnormalities in offspring exposed to maternal immune activation. Explicitly, the primary objectives of this work included; 1) Determining whether induction of MIA in the dam induces immune differences in exposed offspring as compared to control offspring; 2) assessment of the severity or magnitude of deviation from typical immune function in the MIA-exposed offspring; 3) investigating if MIA-exposed offspring exhibit immune function analogous to age-matched control offspring; and 4) identification of potential predictors or indicators of the severity of immune dysfunction using maternal immune baseline measurements and post-injection immune measurements. With a focus on early life timepoints, this dissertation contributes valuable information to the field by examining pre-pubescent and immediate post-pubescent years, an area of study that has been overlooked in previous research. More specifically, it aims to provide insights into the long-term impacts of maternal immune activation on offspring immune function and development observed during these critical developmental stages.

In addition to the primary focus on nonhuman primate data, this dissertation includes human data derived from the Childhood Autism Risks from Genetics and the Environment (C.H.A.R.G.E.) study. This integration further deepens our understanding of the interplay between immune functionality and neurodevelopmental outcomes.

To assess the impact of maternal immune perturbation on immune function in offspring, Chapter 1 details the use of a longitudinal study of MIA in an NHP model. Samples from 24 dam-infant pairs previously published by Vlasova et al., 2021, were analyzed. Briefly, pregnant NHP dams were subjected to polyinosinic:polycytidylic acid (PolyICLC) challenges during their first trimester to induce MIA. Dam sickness behaviors, immune cell counts, as well as cytokine and chemokine profiles were assessed. Likewise, offspring immune profiles were assessed at postnatal day (PND) 30, 90, and 180 by plasma cytokine and chemokine concentrations. The chapter demonstrates that MIA successfully induced distinct immediate and sustained immune responses with increased expression of antiviral cytokines such as IFN-, IL-12/23, IL-15, and IL-18 in conjunction with cytokines and chemokines associated with pro-inflammatory, anti-inflammatory, T cell, and TH2 responses in MIA dams relative to saline control dams. Correspondingly, offspring exposed to MIA during gestation displayed significantly increased innate and adaptive immune cells as compared to control offspring. Further, persistent changes in circulating cytokine and chemokine expression over time were observed in MIA-exposed offspring, indicating continual divergence of immune profiles between exposed and non-exposed offspring. The findings within Chapter 1 suggest that MIA exposure during gestation affects both the maternal immune response and offspring immune status, highlighting a direct link between maternal immune activation during pregnancy and potential deviations in offspring immune function in early life.

Studies using various MIA models suggest the potential of transient changes in immune profiles of MIA-exposed offspring over time. While Chapter 1 supports the notion that the maternal immune response modulates offspring immune profiles, Chapter 2 emphasizes and directly evaluates the lasting effects of maternal immune perturbation on the peripheral and functional immune profile of exposed offspring. Utilizing the same 24 dam-infant pairings described in Chapter 1, this chapter integrates plasma, cerebral spinal fluid (CSF), and peripheral immune cell data as supplementary parameters to assess the influence of maternal immune perturbation on immune function in NHP offspring aged 2-4 years. To expand on our understanding of immune status over time within these NHP offspring, plasma cytokine and chemokine levels at 2-, 3-, and 4-years of age were analyzed, revealing continued divergence in immune status between MIA-exposed offspring and control offspring. These findings are accompanied by analysis of cytokine and chemokine levels in the CSF at 2.5- and 3.5-years of age which highlight the lifelong effects of MIA On offspring neurodevelopment and immune function, as our MIA-exposed offspring exhibited higher concentrations of pro-inflammatory cytokines and chemokines, even in the absence of a stimulus, compared to control offspring well past birth. To investigate immune functionality, Chapter 2 details the isolation of peripheral blood mononuclear cells from MIA-exposed and control offspring at 2.5 and 3.5 years of age. Subsequently, these cells were cultured in the presence of either media alone, PHA, LPS, or PolyIC. These stimulation assays demonstrate pronounced differences in immune function as MIA offspring displayed distinct responses, varying not only by year but stimulation type, in contrast to control offspring. Collectively, the results presented within Chapter 2 provide evidence that maternal immune responses during gestation have a nuanced, long-lasting influence on offspring immune system development and function.

In Chapter 3, as part of the C.H.A.R.G.E. study, we evaluated the immune functionality of a cohort consisting of 31 children diagnosed with autism spectrum disorder (ASD) and 22 typically developing (TD) children by isolating their peripheral blood mononuclear cells and culturing these cells in the presence of media alone, PHA, LPS, or PolyIC. Through the analysis of the immune response in this cohort, nuanced similarities and differences among age-matched ASD and TD groups were identified, revealing distinct immune profiles between ASD and TD children. This emphasizes the complex, intricate relationship between immune dysregulation and atypical neurodevelopment. Furthermore, the retrospective nature of this population-based study facilitated the examination of newborn neonatal bloodspots of corresponding study participants. This unique opportunity enabled discernment of potential correlations between the expression of immune factors identified during newborn screening and those present, or absent, in 5-year-olds, ultimately allowing evaluation of the developmental trajectory of the immune profile as it relates to neurodevelopmental disorders.

The innovative studies outlined in Chapters 1 and 2 contribute to our understanding of the extensive influence maternal-fetal immune imprinting has on offspring immune responses. By delineating the complex interplay between the prenatal environment and immune function in offspring, these investigations also demonstrate the critical role of maternal immune influence in shaping both fetal neurodevelopment and immune function. Furthermore, the findings suggested that neurodevelopmental status may effectively presage immune responses and overall immune outcomes in offspring. This notion is further exemplified in Chapter 3, which shifts focus to offspring immune function in response to various immune challenges. Taken together, the findings from all chapters showcase the ongoing interplay between neurodevelopment and immune function, highlighting the intricate relationship between these systems and their implications for offspring outcomes.