Inflammatory Conditions During Pregnancy and Risk of Autism and Other Neurodevelopmental Disorders

Maternal Immune Activation and Autism in Offspring: What Is the Evidence for Causation?

The maternal immune activation hypothesis has gained attention over the past 2 decades as a potential contributor to the etiology of autism. This hypothesis posits that maternal conditions associated with inflammation during pregnancy may increase the risk of autism in offspring. Autism is highly heritable, and causal environmental contributors to autism largely remain elusive. We review studies on maternal conditions during pregnancy, all associated with some degree of systemic inflammation, namely maternal infections, autoimmunity, and high body mass index. We also review studies of inflammatory markers in biological samples collected from mothers during pregnancy or from neonates and their relationship with autism assessed in children later in life. Recent reports indicate familial clustering of autism, autoimmunity, and infections, as well as genetic correlations between autism and aspects of immune function. Given this literature, there is an apparent risk of confounding of the reported associations between inflammatory exposures and autism by familial genetic factors in both clinical and epidemiological cohort studies. We highlight recent studies that have attempted to address potential confounding to assess evidence of causal effects of inflammation during early life in autism.

Profiling of activated monocyte populations in autism and associations with increased severity and comorbid behaviors

Immune dysfunction in autism spectrum disorder (ASD) has been widely reported and is associated with increased impairments in social interactions, communication, repetitive behaviors, anxiety and gastrointestinal problems. Several lines of evidence point towards increased activation of the innate immune system including activation of microglia, increases in innate inflammatory cytokines/chemokines in blood, brain tissue and CSF, activated dendritic cells and macrophages, and abnormal peripheral monocyte cell function. Monocytes are major players in innate immunity and have important functions in the phagocytosis of pathogens or debris, immune defense and cytokine/chemokine production. However, little is known about the frequencies of different circulating monocytes populations in ASD compared with similarly aged typically developing (TD) controls. In this study, the profile of circulating monocytes exhibiting different markers of activation were assessed in 77 children with ASD, and 49 TD controls who were enrolled as part of the Autism Phenome Project and were of a similar age, 2-4 years old. The frequencies of monocytes expressing the activation marker CD137 (4-1BB) were significantly increased in children with ASD and associated with greater behavioral impairments. In addition, although the frequencies of non-classical monocytes (CD14+CD16+) were not significantly different across groups, they were linked to worse behaviors in both the context of ASD and TD. Conversely classical monocytes were associated with better behavioral outcomes. These data further implicate monocytes and innate immune cells in the complex pathophysiology of ASD. Monocyte cells play key roles in modulating immune responses and differences in the activation profiles of these cells may result in immune dysfunction in children with ASD.

The association of maternal COVID-19-infection during pregnancy on the neonatal immune profile and associations with later diagnosis of neurodevelopmental disorders

Despite the prevalence and significant concern of COVID-19 in maternal and offspring health, little is known about the impact of COVID-19 during pregnancy on newborn immunity and neurodevelopment. This study aimed to examine 1) the relationship between maternal COVID-19 during pregnancy and newborn immune profiles and investigate the 2) associations between specific newborn immune profiles and the risk of subsequent diagnosis of a neurodevelopmental disorder (NDD) among children with prenatal exposure to COVID-19. Newborn dried bloodspots (NBS) from 545 children born at Kaiser Permanente Northern California between January 2020 and September 2021 (460 [223 males, 237 females] to COVID-19-infected [COVID+] mothers; 85 [45 males, 40 females] to COVID-19-uninfected [COVID-] mothers) were used to profile newborn immune molecules via a 42-plex cytokine/chemokine assay. Among the 460 children born to COVID+ mothers, 73 (47 males, 27 females) were later diagnosed with an NDD. In the first set of analyses examining the association between maternal COVID-19 infection during pregnancy and newborn immune profile, the results adjusted for covariates but uncorrected for multiple comparisons showed that newborns of COVID+ mothers had significantly higher levels of IL-22 (estimate [est.] = 0.16, 95 % Cl 0.01, 0.3, p = 0.04) and GM-CSF (est. = 0.27, 95 % Cl 0.09, 0.46, p = 0.004) compared to newborns of COVID- mothers. These differences were no longer statistically significant after multiple comparison adjustments. In the second analysis exploring the association between newborn profile and later diagnosis of NDD among newborns born to COVID+ mothers, the results adjusted for covariates revealed an association between higher neonatal levels of IL-22 (hazard ratio [HR] = 0.49, 95 % Cl 0.33, 0.75, p = 0.001) and lower risk of a later diagnosis of an NDD, which remained significant after multiple comparison adjustments (p = 0.04). Other neonatal cytokines/chemokines/growth factors such as sCD40L (HR = 0.7, 95 % Cl 0.57, 0.9, p = 0.009), IP-10 (HR = 0.46, 95 % Cl 0.25, 0.83, p = 0.009), MIG (HR = 0.52, 95 % Cl 0.3, 0.9, p = 0.02), FLT-3L (HR = 0.45, 95 % Cl 0.24, 0.83, p = 0.01), PDGF AB/BB (HR = 0.56, 95 % Cl 0.36, 0.99, p = 0.046), VEGF (HR = 0.57, 95 % Cl 0.34, 0.98, p = 0.04), and IL-4 (HR = 0.48, 95 % Cl 0.26, 0.93, p = 0.03) were no longer statistically significant after multiple comparison adjustments. Despite the imbalance between the number of COVID-19 exposed and unexposed newborns in this study cohort, our novel findings enhance our understanding of the potential impact of maternal COVID-19 infection during pregnancy on the developing neonatal immune system. Our findings highlight the role of immune molecules, beyond those considered to be pro-inflammatory, that may be crucial in maternal and newborn immunity against COVID-19 infection during pregnancy. Furthermore, our results suggest that reduced levels of neonatal immune molecules in newborns of COVID + mothers may be linked to an increased risk of a subsequent diagnosis of an NDD.

Immune Alterations in the Intrauterine Environment Shape Offspring Brain Development in a Sex-Specific Manner

Exposure to immune dysregulation in utero or in early life has been shown to increase risk for neuropsychiatric illness. The sources of inflammation can be varied, including acute exposures due to maternal infection or acute stress, or persistent exposures due to chronic stress, obesity, malnutrition, or autoimmune diseases. These exposures may cause subtle alteration in brain development, structure, and function that can become progressively magnified across the lifespan, potentially increasing the likelihood of developing a neuropsychiatric conditions. There is some evidence that males are more susceptible to early-life inflammatory challenges than females. In this review, we discuss the various sources of in utero or early-life immune alteration and the known effects on fetal development with a sex-specific lens. To do so, we leveraged neuroimaging, behavioral, cellular, and neurochemical findings. Gaining clarity about how the intrauterine environment affects offspring development is critically important for informing preventive and early intervention measures that may buffer against the effects of these early-life risk factors.

The Association Between In Utero Exposure to Painkillers and Trajectories of Hyperactivity and Emotional Problems in Children with Autism Compared with Neurotypical Peers

Background/Objectives: In utero exposure to painkillers has raised concerns regarding its potential impact on neurodevelopmental disorders, such as autism spectrum disorder (ASD). This study investigates the association between in utero exposure to painkillers and trajectories of hyperactivity and emotional problems in children with and without ASD, separately. Methods: Data were drawn from 5107 participants enrolled in the Longitudinal Study of Australian Children. Emotional and behavioral problems were assessed using the Strengths and Difficulties Questionnaire at ages 4, 6, and 8 years. ASD diagnosis was determined based on parental self-report by age 12. To examine the association between the exposure and the outcomes, mixed linear models were applied to assess the impact of in utero exposure to painkillers on hyperactivity and emotional problems, controlling for sex, time, and other perinatal risk factors. The interaction term between exposure and time was included to evaluate the effect of exposure on the trajectory over time. Results: In utero exposure to painkillers did not significantly affect hyperactivity or emotional problem trajectories in children with ASD. However, in non-ASD children, painkiller exposure was associated with worsening emotional problems by age 8, with males being affected to a greater extent than females. Further, emotional problem scores increased over time by gender, reflecting developmental challenges in early childhood. Conclusions: These findings indicate that prenatal painkiller exposure is unlikely to be a major determinant of the severity of neurodevelopmental outcomes in autistic children, but its role in neurodevelopmental outcomes among neurotypical children warrants further investigation. Future research should prioritize precise exposure assessments and integrate multi-environment interactions to further elucidate the long-term impacts of prenatal painkiller use.

Autism likelihood in infants born to mothers with asthma is associated with blood inflammatory gene biomarkers in pregnancy

Mothers with asthma or atopy have a higher likelihood of having autistic children, with maternal immune activation in pregnancy implicated as a mechanism. This study aimed to determine, in a prospective cohort of mothers with asthma and their infants, whether inflammatory gene expression in pregnancy is associated with likelihood of future autism. Mothers with asthma were recruited to the Breathing for Life Trial. RNA was extracted from blood samples collected at mid-pregnancy. 300 ng total RNA was hybridized with the nCounter Human Inflammation gene expression panel (Nanostring Technologies, 249 inflammation-related genes). Parents completed the First Year Inventory (FYI) at 12-month follow-up, which assessed an infant's likelihood for autism across 2 behavioural domains: social communication and sensory regulation. A total score ≥19.2 indicated increased likelihood for future autism. Inflammatory gene expression was profiled from 24 mothers: four infants scored in the high autism likelihood range; 20 scored in the low autism likelihood range. Six inflammatory genes were differentially expressed and significantly up-regulated in the high autism likelihood group: CYSLTR2, NOX1, C1QA, CXCL10, C8A, IL23R. mRNA count significantly correlated with social communication FYI score for CYSLTR2 (Pearson r = 0.46, p = 0.024) and CXCL10 (r = 0.43, p = 0.036) and with sensory regulation score for ALOX5 (r = -0.43, p = 0.038) and MAFK (r = -0.46, p = 0.022). In this proof-of-concept study, inflammatory gene expression during pregnancy in mothers with asthma was associated with an infant's likelihood of future autism as well as scores relating to social communication and sensory regulation.

The influence of asthma on neuroinflammation and neurodevelopment: From epidemiology to basic models

Asthma is a highly heterogeneous inflammatory disease that can have a significant effect on both the respiratory system and central nervous system. Population based studies and animal models have found asthma to be comorbid with a number of neurological conditions, including depression, anxiety, and neurodevelopmental disorders. In addition, maternal asthma during pregnancy has been associated with neurodevelopmental disorders in the offspring, such as autism spectrum disorders and attention deficit hyperactivity disorder. In this article, we review the most current epidemiological studies of asthma that identify links to neurological conditions, both as it relates to individuals that suffer from asthma and the impacts asthma during pregnancy may have on offspring neurodevelopment. We also discuss the relevant animal models investigating these links, address the gaps in knowledge, and explore the potential future directions in this field.