Clinical clues for autoimmunity and neuroinflammation in patients with autistic regression

Autism Spectrum Disorder and Sleep

Children and adolescents with autism spectrum disorder (ASD) experience sleep disturbances, particularly insomnia, at rates much higher than the general population. Daytime behavioral problems and parental stress are associated with the resultant sleep deprivation. Behavioral interventions, parental education, and melatonin are effective treatments. The epidemiology of sleep disturbances in youth with ASD is reviewed in this article as well as the latest in treatments.

Autistic Regression and Exposure to Industrial Chemicals: Preliminary Observations

Exposure to industrial pollutants is a potential risk factor not fully explored in ASD with regression (ASD+R). We studied geographical collocation patterns of industrial air chemical emissions and the location of homes of children with ASD+R at different exposure times, compared with ASD cases without regression (ASD-R). Fifteen of 111 emitted chemicals collocated with ASD+R, and 65 with ASD-R. ASD+R collocated more strongly with different neurotoxicants/immunotoxicants a year before diagnosis, whereas ASD-R were moderately collocated with chemicals across all exposure periods. This preliminary exploratory analysis of differences in exposure patterns raises a question regarding potential pathophysiological differences between the conditions.

Neuroimmune mechanisms in autism etiology - untangling a complex problem using human cellular models

Autism spectrum disorder (ASD) affects 1 in 36 people and is more often diagnosed in males than in females. Core features of ASD are impaired social interactions, repetitive behaviors and deficits in verbal communication. ASD is a highly heterogeneous and heritable disorder, yet its underlying genetic causes account only for up to 80% of the cases. Hence, a subset of ASD cases could be influenced by environmental risk factors. Maternal immune activation (MIA) is a response to inflammation during pregnancy, which can lead to increased inflammatory signals to the fetus. Inflammatory signals can cross the placenta and blood brain barriers affecting fetal brain development. Epidemiological and animal studies suggest that MIA could contribute to ASD etiology. However, human mechanistic studies have been hindered by a lack of experimental systems that could replicate the impact of MIA during fetal development. Therefore, mechanisms altered by inflammation during human pre-natal brain development, and that could underlie ASD pathogenesis have been largely understudied. The advent of human cellular models with induced pluripotent stem cell (iPSC) and organoid technology is closing this gap in knowledge by providing both access to molecular manipulations and culturing capability of tissue that would be otherwise inaccessible. We present an overview of multiple levels of evidence from clinical, epidemiological, and cellular studies that provide a potential link between higher ASD risk and inflammation. More importantly, we discuss how stem cell-derived models may constitute an ideal experimental system to mechanistically interrogate the effect of inflammation during the early stages of brain development.

Developmental regression in children: Current and future directions

Developmental regression describes when a child loses previously established skills, such as the ability to speak words and is most recognised in neurodevelopmental conditions including Autism; Developmental Epileptic Encephalopathies, such as Landau Kleffner syndrome, and genetic conditions such as Rett syndrome and Phelan McDermid syndrome. Although studies have reported developmental regression for over 100 years, there remain significant knowledge gaps within and between conditions that feature developmental regression. The certainty of evidence from earlier work has been limited by condition-specific studies, retrospective methodology, and inconsistency in the definitions and measures used for classification. Given prior limitations in the field, there is a paucity of knowledge about neurocognitive mechanisms, trajectories and outcomes for children with developmental regression, and their families. Here we provide a comprehensive overview, synthesise key definitions, clinical measures, and aetiological clues associated with developmental regression and discuss impacts on caregiver physical and mental health to clarify challenges and highlight future directions in the field.

The Role of SNAP-25 in Autism Spectrum Disorders Onset Patterns

Autism spectrum disorders (ASD) can present with different onset and timing of symptom development; children may manifest symptoms early in their first year of life, i.e., early onset (EO-ASD), or may lose already achieved skills during their second year of life, thus showing a regressive-type onset (RO-ASD). It is still controversial whether regression represents a neurobiological subtype of ASD, resulting from distinct genetic and environmental causes. We focused this study on the 25 kD synaptosomal-associated protein (SNAP-25) gene involved in both post-synaptic formation and adhesion and considered a key player in the pathogenesis of ASD. To this end, four single nucleotide polymorphisms (SNPs) of the SNAP-25 gene, rs363050, rs363039, rs363043, and rs1051312, already known to be involved in neurodevelopmental and psychiatric disorders, were analyzed in a cohort of 69 children with EO-ASD and 58 children with RO-ASD. Both the rs363039 G allele and GG genotype were significantly more frequently carried by patients with EO-ASD than those with RO-ASD and healthy controls (HC). On the contrary, the rs1051312 T allele and TT genotype were more frequent in individuals with RO-ASD than those with EO-ASD and HC. Thus, two different SNAP-25 alleles/genotypes seem to discriminate between EO-ASD and RO-ASD. Notably, rs1051312 is located in the 3' untranslated region (UTR) of the gene and is the target of microRNA (miRNA) regulation, suggesting a possible epigenetic role in the onset of regressive autism. These SNPs, by discriminating two different onset patterns, may represent diagnostic biomarkers of ASD and may provide insight into the different biological mechanisms towards the development of better tailored therapeutic and rehabilitative approaches.

Evidence of neuroinflammation and immunotherapy responsiveness in individuals with down syndrome regression disorder

Background

Down syndrome regression disorder is a symptom cluster consisting of neuropsychiatric regression without cause. This study evaluated the incidence of neurodiagnostic abnormalities in individuals with Down syndrome regression disorder and determined if abnormalities are indicative of responses to therapeutic intervention.

Methods

A retrospective, multi-center, case-control study was performed. Patients were required to have subacute onset and the presence of four of five symptom groups present (cognitive decline, expressive language, sleep derangement, loss of ability to perform activities of daily living, and/or a new movement disorder) and no other explanation for symptoms.

Results

Individuals with Down syndrome regression disorder were comparable to a cohort of individuals with only Down syndrome although had higher rates of autoimmune disease (p = 0.02, 95%CI 1.04–1.75). Neurodiagnostic abnormalities were found on EEG (n = 19, 26%), neuroimaging (n = 16, 22%), and CSF (n = 9, 17%). Pleocytosis was appreciated in five cases, elevated total protein in nine, elevated IgG index in seven, and oligoclonal bands in two. Testing within 2 years of symptom onset was more likely to have neurodiagnostic abnormalities (p = 0.01, 95%CI 1.64–37.06). In individuals with neurodiagnostic abnormalities, immunotherapy was nearly four times more likely to have a therapeutic effect than in those without neurodiagnostic abnormalities (OR 4.11, 95%CI 1.88–9.02). In those with normal neurodiagnostic studies (n = 43), IVIg was effective in 14 of 17 (82%) patients as well although other immunotherapies were uniformly ineffective.

Conclusions

This study reports the novel presence of neurodiagnostic testing abnormalities in individuals with Down syndrome regression disorder, providing credence to this symptom cluster potentially being of neurologic and/or neuroimmunologic etiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11689-022-09446-w.

Regressive Autism Spectrum Disorder: High Levels of Total Secreted Amyloid Precursor Protein and Secreted Amyloid Precursor Protein-α in Plasma

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder characterized by social communication difficulties, repetitive behaviors, and parochial interests. Individuals with regressive ASD (RA), a unique subtype, have poor outcomes. Moreover, there are currently no validated blood-based biomarkers for ASD, hindering early diagnosis and treatment. This study was the first to examine plasma levels of total secreted amyloid precursor protein (sAPPtotal), secreted amyloid precursor protein-α (sAPPα), and secreted amyloid precursor protein-β (sAPPβ) in children diagnosed with RA (n = 23) and compare them with the levels in age-matched children with non-regressive ASD (NRA) (n = 23) and typically developing (TD) controls (n = 23). We found that sAPPtotal and sAPPα levels were significantly higher in children with RA than in children with NRA or in TD controls. In contrast, no difference was observed in sAPPβ levels. In conclusion, increased plasma levels of sAPPtotal and sAPPα may be valuable biomarkers for the early identification of ASD regression. Prospective studies will be conducted using a larger sample to further investigate these differences.

Autoimmune Encephalitis and Autism Spectrum Disorder

The concept of "acquired autism" refers to the hypothesis that amongst the massive heterogeneity that encompasses autism spectrum disorder (ASD) there may be several phenotypes that are neither syndromic nor innate. Strong and consistent evidence has linked exposure to various pharmacological and infective agents with an elevated risk of a diagnosis of ASD including maternal valproate use, rubella and herpes encephalitis. Autoimmune encephalitis (AE) describes a group of conditions characterised by the body's immune system mounting an attack on healthy brain cells causing brain inflammation. The resultant cognitive, psychiatric and neurological symptoms that follow AE have also included ASD or autism-like traits and states. We review the current literature on AE and ASD. Drawing also on associated literature on autoimmune psychosis (AP) and preliminary evidence of a psychosis-linked subtype of ASD, we conclude that AE may either act as a potentially causative agent for ASD, and/or produce symptoms that could easily be mistaken for or misdiagnosed as autism. Further studies are required to discern the connection between AE and autism. Where autism is accompanied by regression and atypical onset patterns, it may be prudent to investigate whether a differential diagnosis of AE would be more appropriate.

Maternal immune-related conditions during pregnancy may be a risk factor for neuropsychiatric problems in offspring throughout childhood and adolescence

BACKGROUND

Emerging research suggests that maternal immune activation (MIA) may be associated with an increased risk of adverse neurodevelopmental and mental health outcomes in offspring. Using data from the Raine Study, we investigated whether MIA during pregnancy was associated with increased behavioral and emotional problems in offspring longitudinally across development.

METHODS

Mothers (Generation 1; N = 1905) were classified into the following categories: AAAE (Asthma/Allergy/Atopy/Eczema; N = 1267); infection (during pregnancy; N = 1082); no AAAE or infection (N = 301). The Child Behavior Checklist (CBCL) was administered for offspring at ages 5, 8, 10, 14, and 17. Generalized estimating equations were used to investigate the effect of maternal immune status on CBCL scores.

RESULTS

AAAE conditions were associated with significant increases in CBCL Total (β 2.49; CI 1.98-3.00), Externalizing (β 1.54; CI 1.05-2.03), and Internalizing (β 2.28; CI 1.80-2.76) scores. Infection conditions were also associated with increased Total (β 1.27; CI 0.77-1.78), Externalizing (β 1.18; CI 0.70-1.66), and Internalizing (β 0.76; CI 0.28-1.24) scores. Exposure to more than one AAAE and/or infection condition was associated with a greater elevation in CBCL scores than single exposures in males and females. Females showed greater increases on the Internalizing scale from MIA, while males showed similar increases on both Internalizing and Externalizing scales.

CONCLUSIONS

MIA was associated with increased behavioral and emotional problems in offspring throughout childhood and adolescence. This highlights the need to understand the relationship between MIA, fetal development, and long-term outcomes, with the potential to advance early identification and intervention strategies.

Prevalence and Age of Onset of Regression in Children with Autism Spectrum Disorder: A Systematic Review and Meta-analytical Update

A systematic review published in 2013 reported 32% of children on the autism spectrum experience skill loss, known as autistic regression. However, the frequency varied depending on definition and measures used to capture skills. Retrospective parent report and prospective observation indicate loss of language and/or social skills, with motor skills typically unaffected. Our aim was to update the prevalence and age of onset of autistic regression through a meta-analysis of the literature to understand if there have been changes to the reported onset and prevalence since 2010. A systematic literature search was conducted using Medline, Embase, PsycINFO, and the Cochrane Library databases and included studies published from 2010 onward. Risk of bias assessment was performed on included studies. A random effects model was used to calculate the pooled prevalence and age of onset of autistic regression. Ninety-seven studies were included in the systematic review, of which 75 studies involving 33,014 participants had sufficient data for meta-analytic syntheses. The pooled proportion of autistic regression was 30% (95% confidence interval [CI]: 27-32%) but heterogeneity was high (I² = 96.91) and did not reduce with sensitivity or subgroup analyses based on study design or clinical differences, respectively. Prevalence varied according to risk of bias (low: 27%) and definition of regression (language: 20%, language/social: 40%, mixed: 30%, and unspecified: 27%). Weighted average age of onset was 19.8 months. Findings from this meta-analysis highlight the importance of developing a standardized definition of autistic regression, and tools to measure this at multiple time points during early childhood development. LAY SUMMARY: About a third of children with Autism Spectrum Disorder experience loss of skills, which is also known as autistic regression. This paper provides an update of the rate of autistic regression in children and the age when they first experience loss of skills, based on current studies. The findings from this review contribute to our understanding of the onset patterns of autistic regression. Unfortunately, studies are not sufficiently similar, making it difficult to provide clear answers on the exact timing or type of regression seen in different children.

Prednisolone as Adjunctive Treatment to Risperidone in Children With Regressive Type of Autism Spectrum Disorder: A Randomized, Placebo-Controlled Trial

OBJECTIVES

This study aimed to evaluate efficacy and safety of prednisolone as an adjunctive treatment to risperidone, in children with regressive autism spectrum disorder (ASD).

METHODS

The current 12-week, randomized, single-blinded, placebo-controlled trial recruited 37 patients with regressive ASD. The participants were allocated to receive either 1 mg/kg per day prednisolone or matched placebo in addition to risperidone. The Aberrant Behavior Checklist-Community Edition (ABC-C) scale and Childhood Autism Rating Scale (CARS) were used to measure behavioral outcomes at weeks 0, 4, 8, and 12 of the study course. The primary outcome was the change in ABC-irritability subscale score, whereas the secondary outcomes were the change in scores of other ABC-C subscales, in CARS score, and in the level of inflammatory biomarkers.

RESULTS

Twenty-six patients completed the 12 weeks of study period. Repeated-measures analysis demonstrated significant effect for time-treatment interaction in the CARS (F (1, 2.23) = 13.22, P < 0.001), as well as 4 subscales of the ABC-C including: irritability (F (1, 2.12) = 3.84, P = 0.026), hyperactivity (F (1, 2.09) = 3.56, P = 0.039), lethargy (F (1, 2.18) = 31.50, P < 0.001), and stereotypy (F (1, 1.89) = 4.04, P = 0.026). However, no significant time-treatment interaction was identified for inappropriate speech subscale (F (1, 2.03) = 1.71, P = 0.191). In addition, inflammatory biomarkers were significantly decreased after 3 months of prednisolone add-on. No significant adverse event was detected during the trial.

CONCLUSIONS

Prednisolone, as an add-on to risperidone, could remarkably improve core features in children with regressive ASD.

Autism Spectrum Disorder and Sleep

Children and adolescents with autism spectrum disorder (ASD) experience sleep disturbances, particularly insomnia, at rates much higher than the general population. Daytime behavioral problems and parental stress are associated with the resultant sleep deprivation. Behavioral interventions, parental education, and melatonin are effective treatments. The epidemiology of sleep disturbances in youth with ASD is reviewed in this article as well as the latest in treatments.

Immune regulation of neurodevelopment at the mother-foetus interface: the case of autism

Autism spectrum disorder (ASD) is a neurodevelopmental disorder defined by deficits in social communication and stereotypical behaviours. ASD’s aetiology remains mostly unclear, because of a complex interaction between genetic and environmental factors. Recently, a strong consensus has developed around ASD’s immune‐mediated pathophysiology, which is the subject of this review. For many years, neuroimmunological studies tried to understand ASD as a prototypical antibody‐ or cell‐mediated disease. Other findings indicated the importance of autoimmune mechanisms such as familial and individual autoimmunity, adaptive immune abnormalities and the influence of infections during gestation. However, recent studies have challenged the idea that autism may be a classical autoimmune disease. Modern neurodevelopmental immunology shows the double‐edged nature of many immune effectors, which can be either beneficial or detrimental depending on tissue homeostasis, stressors, neurodevelopmental stage, inherited and de novo gene mutations and other variables. Nowadays, mother–child interactions in the prenatal environment appear to be crucial for the occurrence of ASD. Studies of animal maternal–foetal immune interaction are being fruitfully carried out using different combinations of type and timing of infection, of maternal immune response and foetal vulnerability and of resilience factors to hostile events. The derailed neuroimmune crosstalk through the placenta initiates and maintains a chronic foetal neuroglial activation, eventually causing the alteration of neurogenesis, migration, synapse formation and pruning. The importance of pregnancy can also allow early immune interventions, which can significantly reduce the increasing risk of ASD and its heavy social burden.

Maternal immune conditions are increased in males with autism spectrum disorders and are associated with behavioural and emotional but not cognitive co-morbidity

Epidemiological and animal research shows that maternal immune activation increases the risk of autism spectrum disorders (ASD) in offspring. Emerging evidence suggests that maternal immune conditions may play a role in the phenotypic expression of neurodevelopmental difficulties in children with ASD and this may be moderated by offspring sex. This study aimed to investigate whether maternal immune conditions were associated with increased severity of adverse neurodevelopmental outcomes in children with ASD. Maternal immune conditions were examined as predictors of ASD severity, behavioural and emotional well-being, and cognitive functioning in a cohort of 363 children with ASD (n = 363; 252 males, 111 females; median age 3.07 [interquartile range 2.64-3.36 years]). We also explored whether these outcomes varied between male and female children. Results showed that maternal asthma was the most common immune condition reported in mothers of children with ASD. A history of maternal immune conditions (p = 0.009) was more common in male children with ASD, compared to female children. Maternal immune conditions were associated with increased behavioural and emotional problems in male and female children. By contrast, maternal immune conditions were not associated with decreased cognitive function. The findings demonstrate that MIA may influence the expression of symptoms in children with ASD and outcomes may vary between males and females.

Bridging the Gap Between Physical Health and Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a highly complex and heterogeneous developmental disorder that affects how individuals communicate with other people and relate to the world around them. Research and clinical focus on the behavioural and cognitive manifestations of ASD, whilst important, have obscured the recognition that ASD is also commonly associated with a range of physical and mental health conditions. Many physical conditions appear with greater frequency in individuals with ASD compared to non-ASD populations. These can contribute to a worsening of social communication and behaviour, lower quality of life, higher morbidity and premature mortality. We highlight some of the key physical comorbidities affecting the immune and the gastrointestinal systems, metabolism and brain function in ASD. We discuss how healthcare professionals working with individuals with ASD and parents/carers have a duty to recognise their needs in order to improve their overall health and wellbeing, deliver equality in their healthcare experiences and reduce the likelihood of morbidity and early mortality associated with the condition.

Is Autism Inborn And Lifelong For Everyone?

Autism or autism spectrum disorder (ASD) is described as a lifelong condition with core behavioural symptoms appearing during infancy or early childhood. Genetic and other effects occurring during the earliest times of life are thought to play a significant contributory role to the presentation of autism, denoting that autism is typically seen as an innate or inborn condition. Such descriptions have, and continue to, define autism research and clinical practice. Inspection of the existing research literature, however, suggests that within the vast heterogeneity of autism, not everyone experiences autism in such a prescribed way. Various reports have observed the presentation of "acquired autism" following a period of typical development. Other findings have documented an abatement of clinically relevant autistic features and related comorbid pathology for some. Such reports offer important insights into the heterogeneity and complexity of autism.

Autism With and Without Regression: A Two-Year Prospective Longitudinal Study in Two Population-Derived Swedish Cohorts

Two community-based cohorts of children with autism spectrum disorder, examined using similar assessment protocols, were pooled (n = 301) and subdivided according to history of regression. Those with regression (n = 62), 20.5% of the combined cohort, were contrasted with those without regression (n = 241) at first assessment (age range 19–60 months) and at 2-year follow-up on a range of measures. The regression group was significantly more functionally impaired, with regard to intellectual function (p < .001), language development (p < .001), and to severity of autism (p < .01) at both T1 and T2. Only 14 (23.3%) had a clearly identified underlying etiology [24 (18.6%) in the non-regressive group]. There were no significant differences between those who had regressed ‘from normal’ and those who had regressed ‘from low’ functioning.

Maternal thyroid autoimmunity associated with acute-onset neuropsychiatric disorders and global regression in offspring

Epidemiological studies, animal models, and case-control studies indicate maternal immune activation may be an important factor involved in disease expression of autism spectrum disorder (ASD), Tourette syndrome, and obsessive-compulsive disorder (OCD). We report eight children (mean age 6y 6mo [range 4-15y]; six males and two females) referred over a 2-year period with at least one of these neurodevelopmental disorders plus a maternal history of thyroid autoimmunity. Seven of eight children presented with an abrupt onset of neuropsychiatric symptoms (OCD [n=6], tics [n=5], and/or psychosis [n=1]), associated with an autistic or global regression. Four children had a pre-existing diagnosis of ASD. Six presentations were preceded by infection, and symptoms followed a relapsing-remitting course in seven children. All children responded to immunomodulatory treatment as indicated by a reduction in psychiatric symptoms, and seven children were also managed with conventional treatment with additional improvement. We propose that maternal autoimmunity can activate fetal microglia or alter transcription of neurodevelopmental vulnerability and/or immune genes in utero, and is an environmental factor that increases the expression and severity of neurodevelopmental problems, and susceptibility to deteriorations after infectious or stress stimuli. WHAT THIS PAPER ADDS: Maternal thyroid autoimmunity may represent a risk factor for neuropsychiatric disorders in offspring. Atypical neuropsychiatric features in these children may be due to maternal immune activation in utero.

Changing conceptualizations of regression: What prospective studies reveal about the onset of autism spectrum disorder

Until the last decade, studies of the timing of early symptom emergence in autism spectrum disorder (ASD) relied upon retrospective methods. Recent investigations, however, are raising significant questions about the accuracy and validity of such data. Questions about when and how behavioral signs of autism emerge may be better answered through prospective studies, in which infants are enrolled near birth and followed longitudinally until the age at which ASD can be confidently diagnosed or ruled out. This review summarizes the results of recent studies that utilized prospective methods to study infants at high risk of developing ASD due to family history. Collectively, prospective studies demonstrate that the onset of ASD involves declines in the rates of key social and communication behaviors during the first years of life for most children. This corpus of literature suggests that regressive onset patterns occur much more frequently than previously recognized and may be the rule rather than the exception.

Regression in autism spectrum disorder: A critical overview of retrospective findings and recommendations for future research

Historically, two onset patterns in autism spectrum disorder (ASD) were described: early onset of symptoms and regression in which one-third appear to show a loss of previously established skills in the second year of life. Since this phenomenon could represent a distinct ASD subtype and provide more insight into the etiology, diagnosis, and prognosis, many studies have compared these two groups. The present review discusses definitions, etiology, and methods used in research with a retrospective design and provides an overview of the results on early development and outcomes. However, retrospective research has not provided clear answers on regression as a distinct subtype of ASD and the historic division between early onset and regression does not seem to fit the empirical findings. Based on inconsistent results, future research on onset patterns in ASD needs to be more systematic on the definitions and methods used. Several recommendations to enhance the reliability of future retrospective results are discussed. The combination of a categorical and dimensional approach provides a new interesting framework.

Regression in autism spectrum disorder: Reconciling findings from retrospective and prospective research

The way in which the behavioral manifestations of autism spectrum disorder (ASD) emerge in infancy is variable. Regression-loss of previously acquired skills-occurs in a subset of children. However, the etiology and significance of regression remains unclear. Until recently, investigation of regression relied on retrospective report by parents or examination of home videos from early in life. However, home videos and retrospective report of the nature and timing of regression, and association with factors such as illness or immunization, is potentially subject to bias. The advent of prospective studies of infant siblings at familial high-risk of ASD has the potential to document regression as it occurs. Recent research has suggested that subtle loss of skills occurs in a larger proportion of children with ASD than previously assumed; however, there are few reports of clear-cut regressions, such as that involving dramatic loss of language and other established skills, in the prospective literature. This could be because of the following: clear-cut regression occurs less commonly than parent report suggests, study design limits the potential to detect regression, or there are differences between multiplex and simplex families in the rate of de novo genetic mutations and therefore regression risk. This review will bring together literature from retrospective and prospective research and attempt to reconcile diverging findings, with a specific focus on methodological issues. Changing conceptualizations of regression will be discussed, as well as etiological factors that may be associated with regression. The main challenges that need to be addressed to measure regression in prospective studies will be set out. Autism Research 2018, 11: 1602-1620. © 2018 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Regression-a loss of previously established skills-occurs in a subset of children with ASD. Parental recall is not always accurate but studying younger siblings of children with ASD, 10-20% of whom will develop ASD, should make it possible to measure regression as it occurs. Clear-cut regression, like loss of language, has not often been reported in infant sibling studies, but recent research suggests that gradual loss of social engagement might be more common. This review looks at the evidence for regression from infant sibling studies and asks how study design affects the likelihood of capturing regression.

Immune Dysfunction and Autoimmunity as Pathological Mechanisms in Autism Spectrum Disorders

Autism spectrum disorders (ASD) are a group of heterogeneous neurological disorders that are highly variable and are clinically characterized by deficits in social interactions, communication, and stereotypical behaviors. Prevalence has risen from 1 in 10,000 in 1972 to 1 in 59 children in the United States in 2014. This rise in prevalence could be due in part to better diagnoses and awareness, however, these together cannot solely account for such a significant rise. While causative connections have not been proven in the majority of cases, many current studies focus on the combined effects of genetics and environment. Strikingly, a distinct picture of immune dysfunction has emerged and been supported by many independent studies over the past decade. Many players in the immune-ASD puzzle may be mechanistically contributing to pathogenesis of these disorders, including skewed cytokine responses, differences in total numbers and frequencies of immune cells and their subsets, neuroinflammation, and adaptive and innate immune dysfunction, as well as altered levels of immunoglobulin and the presence of autoantibodies which have been found in a substantial number of individuals with ASD. This review summarizes the latest research linking ASD, autoimmunity and immune dysfunction, and discusses evidence of a potential autoimmune component of ASD.

Modeling Inflammation in Autism Spectrum Disorders Using Stem Cells

Recent reports show an increase in the incidence of Autism Spectrum Disorders (ASD) to 1 in every 59 children up to 8 years old in 11 states in North America. Induced pluripotent stem cell (iPSC) technology offers a groundbreaking platform for the study of polygenic neurodevelopmental disorders in live cells. Robust inflammation states and immune system dysfunctions are associated with ASD and several cell types participate on triggering and sustaining these processes. In this review, we will examine the contribution of neuroinflammation to the development of autistic features and discuss potential therapeutic approaches. We will review the available tools, emphasizing stem cell modeling as a technology to investigate the various molecular pathways and different cell types involved in the process of neuroinflammation in ASD.

Anti-Candida albicans IgG Antibodies in Children With Autism Spectrum Disorders

The gut microbiota are known to have a profound influence on both mucosal and systemic immunity and are important for gastrointestinal (GI) function. In addition, new evidence shows that the microbiota significantly influence neurodevelopment and behavior. Immune dysfunction and GI distress are extremely common in individuals with autism spectrum disorders (ASD). A growing body of evidence suggests that individuals with ASD have significant aberrations in the composition of their gut microbiota, known as dysbiosis. However, these studies have focused on the bacterial components of the microbiota, leaving the fungal microbiota in ASD poorly studied. Increases in fungal species such as Candida albicans are associated with inflammatory bowel disorders, and have recently been implicated in several neurological disorders including schizophrenia. We aimed to determine if children with ASD exhibit elevations in antibodies that target C. albicans, indicating current or previous overgrowth of this fungal species. We measured anti-C. albicans immunoglobulin (IgG) in plasma from 80 children enrolled in the UC Davis MIND Institute CHARGE study. Measurements were acquired using a commercial ELISA kit. Plasma anti-C. albicans antibody positivity was found in 36.5% (19/52) of children with ASD. Anti-C. albicans antibodies in typically developing controls was (14.3%; 4/28). Overall, ASD children had a higher rate of high-positive values compared to typically developed children with an unadjusted odds ratio of 3.45 (95% confidence interval, 1.0409 to 11.4650; p = 0.041, two-tailed). GI dysfunction was found in about half of the ASD children who were positive for anti-Candida IgG. This study provides evidence of a new microbial risk factor for ASD.