An HLA-G(∗)14bp insertion/deletion polymorphism associates with the development of autistic spectrum disorders

Immunogenetics of autism spectrum disorder: A systematic literature review

The aetiology of autism spectrum disorder (ASD) is complex and, partly, accounted by genetic factors. Nonetheless, the genetic underpinnings of ASD are poorly defined. The presence of immune dysregulations in autistic individuals, and their families, supports a role of the immune system and its genetic regulators. Albeit immune responses belong either to the innate or adaptive arms, the overall immune system genetics is broad, and encompasses a multitude of functionally heterogenous pathways which may have different influences on ASD. Hence, to gain insights on the immunogenetic underpinnings of ASD, we conducted a systematic literature review of previous immune genetic and transcription studies in ASD. We defined a list of immune genes relevant to ASD and explored their neuro-immune function. Our review confirms the presence of immunogenetic variability in ASD, accounted by inherited variations of innate and adaptive immune system genes and genetic expression changes in the blood and post-mortem brain of autistic individuals. Besides their immune function, the identified genes control neurodevelopment processes (neuronal and synaptic plasticity) and are highly expressed in pre/peri-natal periods. Hence, our synthesis bolsters the hypothesis that perturbation in immune genes may contribute to ASD by derailing the typical trajectory of neurodevelopment. Our review also helped identifying some of the limitations of prior immunogenetic research in ASD. Thus, alongside clarifying the neurodevelopment role of immune genes, we outline key considerations for future work into the aetiology of ASD and possible novel intervention targets.

Maternal immune activation during pregnancy is associated with more difficulties in socio-adaptive behaviors in autism spectrum disorder

Autism spectrum disorder (ASD) are neurodevelopmental conditions characterised by deficits in social communication and interaction and repetitive behaviours. Maternal immune activation (MIA) during the mid-pregnancy is a known risk factor for ASD. Although reported in 15% of affected individuals, little is known about the specificity of their clinical profiles. Adaptive skills represent a holistic approach to a person's competencies and reflect specifically in ASD, their strengths and difficulties. In this study, we hypothesised that ASD individual with a history of MIA (MIA+) could be more severely socio-adaptively impaired than those without MIA during pregnancy (MIA-). To answer this question, we considered two independent cohorts of individuals with ASD (PARIS study and FACE ASD) screened for pregnancy history, and used supervised and unsupervised machine learning algorithms. We included 295 mother-child dyads with 14% of them with MIA+. We found that ASD-MIA+ individuals displayed more severe maladaptive behaviors, specifically in their socialization abilities. MIA+ directly influenced individual's socio-adaptive skills, independent of other covariates, including ASD severity. Interestingly, MIA+ affect persistently the socio-adaptive behavioral trajectories of individuals with ASD. The current study has a retrospective design with possible recall bias regarding the MIA event and, even if pooled from two cohorts, has a relatively small population. In addition, we were limited by the number of covariables available potentially impacted socio-adaptive behaviors. Larger prospective study with additional dimensions related to ASD is needed to confirm our results. Specific pathophysiological pathways may explain these clinical peculiarities of ASD- MIA+ individuals, and may open the way to new perspectives in deciphering the phenotypic complexity of ASD and for the development of specific immunomodulatory strategies.

HLA-G*14 bp indel variant in autism spectrum disorder in a population from southern Brazil

Altered immune response during pregnancy has been associated with ASD susceptibility. HLA-G is expressed by the trophoblast at the maternal/fetal interface and induces allogenic tolerance toward the fetus. A 14-bp insertion in the HLA-G 3'UTR (rs371194629) was associated with reduced levels of HLA-G. We aimed to assess the influence of the HLA-G*14 bp indel variant in ASD susceptibility and symptomatology in a Brazilian admixed sample. The insertion genotype (14 bp+/14 bp+) was firstly associated with hetero aggression, but statistical significance was lost after correction (p = 0.035, pcorrected = 0.35). No association between the HLA-G variant and susceptibility to ASD or differential clinical manifestations were observed.

Empathy and behavior in children affected by autism spectrum disorders

BACKGROUND

Many studies have already shown that individuals suffering from autism spectrum disorders (ASD) present low levels of empathy: in fact, reduced emotional reciprocity is considered a clinically significant indicator of autistic functioning. We decided to investigate the role of empathy in determining pathological behaviors in children affected by ASD considering parents' point of view; and to evaluate the presence of differences between mothers and fathers' perception of their child's empathy and behaviors.

METHODS

We compared empathy levels in a sample of 58 patients with ASD as reported by a parent-filled questionnaire with the results of a global evaluation conducted by means of play observations, clinician-rated scales, a semistructured interview with both caregivers and parent-filled questionnaires.

RESULTS

The majority of ASD patients have low levels of empathy according to both parents' points of view; noteworthy, mothers and fathers are highly concordant in this respect. Children's levels of empathy negatively correlate with many behavioral problems, both internalizing and externalizing. Furthermore, we found that mothers tend to perceive more internalizing problems, while fathers are more willing to notice externalizing ones.

CONCLUSIONS

Involving both caregivers in children's diagnostic assessment could deepen patient's evaluation and finally the therapeutic results. Mothers and fathers seem to be highly consistent in describing the psychological characteristics of their child, but not in respect to symptoms.

Alterations of natural killer cells activatory molecules phenotype and function in mothers of ASD children: a pilot study

Introduction

Autism spectrum disorder (ASD) is accompanied by complex immune alterations and inflammation, and the possible role played by Natural Killer (NK) in such alterations is only barely understood.

Methods

To address this question we analysed activating and inhibitory NK receptors, as well as NK cells phenotype and function in a group of mothers of children who developed ASD (ASD-MO; N=24) comparing results to those obtained in mothers of healthy children who did not develop (HC-MO; N=25).

Results

Results showed that in ASD-MO compared to HC-MO: 1) NK cells expressing the inhibitory receptor ILT2 are significantly decreased; 2) the activating HLA-G14bp+ polymorphism is more frequently observed and is correlated with the decrease of ILT2-expressing cells; 3) the CD56bright and CD56dim NK subsets are increased; 4) IFNγ and TNF production is reduced; and 5) perforin- and granzymes-releasing NK cells are increased even in unstimulated conditions and could not be upregulated by mitogenic stimulation.

Discussion

Results herein reinforce the hypothesis that ASD relatives present traits similar to, but not as severe as the defining features of ASD (Autism endophenotype) and identify a role for NK cells impairment in generating the inflammatory milieu that is observed in ASD.

Possible Effect of the use of Mesenchymal Stromal Cells in the Treatment of Autism Spectrum Disorders: A Review

Autism spectrum disorder (ASD) represents a set of heterogeneous neurodevelopmental conditions defined by impaired social interactions and repetitive behaviors. The number of reported cases has increased over the past decades, and ASD is now a major public health burden. So far, only treatments to alleviate symptoms are available, with still unmet need for an effective disease treatment to reduce ASD core symptoms. Genetic predisposition alone can only explain a small fraction of the ASD cases. It has been reported that environmental factors interacting with specific inter-individual genetic background may induce immune dysfunctions and contribute to the incidence of ASD. Such dysfunctions can be observed at the central level, with increased microglial cells and activation in ASD brains or in the peripheral blood, as reflected by high circulating levels of pro-inflammatory cytokines, abnormal activation of T-cell subsets, presence of auto-antibodies and of dysregulated microbiota profiles. Altogether, the dysfunction of immune processes may result from immunogenetically-determined inefficient immune responses against a given challenge followed by chronic inflammation and autoimmunity. In this context, immunomodulatory therapies might offer a valid therapeutic option. Mesenchymal stromal cells (MSC) immunoregulatory and immunosuppressive properties constitute a strong rationale for their use to improve ASD clinical symptoms. In vitro studies and pre-clinical models have shown that MSC can induce synapse formation and enhance synaptic function with consequent improvement of ASD-like symptoms in mice. In addition, two preliminary human trials based on the infusion of cord blood-derived MSC showed the safety and tolerability of the procedure in children with ASD and reported promising clinical improvement of core symptoms. We review herein the immune dysfunctions associated with ASD provided, the rationale for using MSC to treat patients with ASD and summarize the current available studies addressing this subject.

Lactobacillus plantarum PS128 and Other Probiotics in Children and Adolescents with Autism Spectrum Disorder: A Real-World Experience

Autism Spectrum Disorder is a neurodevelopmental disorder. Recent data suggest that probiotics can reduce some symptoms of this disorder and Lactobacillus plantarum PS128 has been reported to be especially useful. We recruited a sample of 131 autistic children and adolescents (M:F = 122:19; age: 86.1 ± 41.1 months) and evaluated their changes after use of probiotics by mean of CGI. We found some significant improvements with very few side effects; these positive effects were more evident in younger children. Patients taking Lactobacillus plantarum PS128 had greater improvements and fewer side effects than those taking other probiotics. Our real-life data are consistent with existing literature showing a specific effect of Lactobacillus plantarum PS128 in Autism Spectrum Disorder.

Autism Spectrum Disorder from the Womb to Adulthood: Suggestions for a Paradigm Shift

The wide spectrum of unique needs and strengths of Autism Spectrum Disorders (ASD) is a challenge for the worldwide healthcare system. With the plethora of information from research, a common thread is required to conceptualize an exhaustive pathogenetic paradigm. The epidemiological and clinical findings in ASD cannot be explained by the traditional linear genetic model, hence the need to move towards a more fluid conception, integrating genetics, environment, and epigenetics as a whole. The embryo-fetal period and the first two years of life (the so-called 'First 1000 Days') are the crucial time window for neurodevelopment. In particular, the interplay and the vicious loop between immune activation, gut dysbiosis, and mitochondrial impairment/oxidative stress significantly affects neurodevelopment during pregnancy and undermines the health of ASD people throughout life. Consequently, the most effective intervention in ASD is expected by primary prevention aimed at pregnancy and at early control of the main effector molecular pathways. We will reason here on a comprehensive and exhaustive pathogenetic paradigm in ASD, viewed not just as a theoretical issue, but as a tool to provide suggestions for effective preventive strategies and personalized, dynamic (from womb to adulthood), systemic, and interdisciplinary healthcare approach.

Non-classical human leukocyte antigen class I in Tunisian children with autism

Autism spectrum disorders (ASD) are one of the most common childhood morbidities characterized by deficits in communication and social skills. Increasing evidence has suggested associations between immune genes located in the human leukocyte antigen (HLA) complex and etiology of autism.

In this study, we investigated whether the non-classical class I HLA-G, -E, and -F polymorphisms are associated with genetic predisposition to autism in Tunisia. We aimed to find a correlation between HLA-G genotypes and soluble HLA-G (sHLA-G) levels. We have analyzed the HLA-G, -E, and -F genotypes of 15 autistic children and their parents. DNA typing of HLA class I genes was performed using PCR-SSP and PCR-RFLP methods. Also, we evaluated the serum levels of HLA-G (1 and 5) by a validated ELISA technique in autistic probands and their parents.

No association was found between any polymorphism and autism in the study subjects. Additionally, we found no correlation between sHLA-G1 and sHLA-G5 and autism. Also, no significant difference in sHLA-G testing in parents and offspring was found. However, parents carrying [GG] genotype presented a higher sHLA-G levels than those carrying ([CC]+[GC]) genotypes (p = 0.037).

From this preliminary study, we conclude that the investigated polymorphisms of HLA-G, -E, and -F genes did not lead to autism susceptibility in Tunisian children. However, the CGTIGA haplotype was found to be associated with the disease.

Understanding the genetic contribution of the human leukocyte antigen system to common major psychiatric disorders in a world pandemic context

The human leukocyte antigen (HLA) is a complex genetic system that encodes proteins which predominantly regulate immune/inflammatory processes. It can be involved in a variety of immuno-inflammatory disorders ranging from infections to autoimmunity and cancers. The HLA system is also suggested to be involved in neurodevelopment and neuroplasticity, especially through microglia regulation and synaptic pruning. Consequently, this highly polymorphic gene region has recently emerged as a major player in the etiology of several major psychiatric disorders, such as schizophrenia, autism spectrum disorder and bipolar disorder and with less evidence for major depressive disorders and attention deficit hyperactivity disorder. We thus review here the role of HLA genes in particular subgroups of psychiatric disorders and foresee their potential implication in future research. In particular, given the prominent role that the HLA system plays in the regulation of viral infection, this review is particularly timely in the context of the Covid-19 pandemic.

Vitamin D Receptor Polymorphisms Associated with Autism Spectrum Disorder

Vitamin D is endowed with a number of biological properties, including down-regulation of inflammation, and might contribute to the pathogenesis of autism spectrum disorders (ASD). Vitamin D binds to the vitamin D Receptor (VDR); the biological activity of the ensuing complex depends on VDR FokI, BsmI, ApaI, and TaqI gene polymorphisms. We evaluated such Single Nucletoide Polymorphismsm (SNPs) in a cohort of 100 Italian families with ASD children. FokI genotype distribution was skewed in ASD children compared with their healthy sibs (P_c = 0.03 2 df) and to a group of 170 Italian healthy women (HC) (P_c = 0.04 2 df). FokI genotype and allelic distribution skewing were also observed in mothers of ASD children compared to HC (P_c = 0.04 2 df). Both Transmission Disequilibrium Test for single loci and haplotype analysis distribution revealed a major FokI (C) allele-mediated protective effect, which was more frequently transmitted (73%) than not transmitted to healthy sibs (P = 0.02). A protective FokI-, BsmI-, ApaI-, and TaqI (CCAG) haplotype was more frequently carried by healthy sibs than by ASD children (P = 1 × 10^-4 ; OR: 0.1, 95% CI: 0.03-0.4) too. Finally, a strong gene-dose association of FokI (T) allele with both higher Childhood Autism Rating Scale score (P_c = 0.01) and, particularly, with hyperactivity behavior (P_c = 0.006) emerged in ASD children. Because the protein produced by the FokI (T) allele is transcriptionally less active than that produced by the FokI (C) allele, the reduced biological activity of the vitamin D/VDR complex prevalent in ASD could favor ASD- and maternal immune activation- associated inflammation. Vitamin D supplementation might be useful in preventative and rehabilitation protocols for ASD. Autism Res 2020, 13: 680-690. © 2020 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Vitamin D deficiency and Vitamin D receptor (VDR) polymorphisms are associated with structural and functional brain abnormalities and behavioral disorders. We analyzed the association of VDR gene polymorphisms in a cohort of 100 Italian families with ASD children. A strong correlation between one of the VDR polymorphisms and hyperactivity behavior was evidenced in ASD children. In healthy mothers, the same VDR polymorphism was also correlated with an increased risk of giving birth to children with ASD.

HLA-G allelic distribution in Sardinian children with Autism spectrum disorders: A replication study

Recent results show that in mainland Italian children with Autism spectrum disorder (ASD), HLA-G coding alleles distribution is skewed and an association between HLA-G*01:05N and ASD is present. Herein, in an independent cohort of Sardinian ASD (sASD) children and their relatives, we verify whether HLA-G allele association with ASD could be confirmed in this genetically peculiar insular population. One hundred children with a diagnosis of ASD, born in Sardinia and of Sardinian descent, 91 of their mothers, and 40 of their healthy siblings were enrolled. DNA sequencing analysis of HLA-G exon 2, 3 and 4 was used to obtain HLA-G allelic frequencies. Alleles distribution was compared with that of continental ASD children and with a control group of Caucasoid couples of multiparous women and their partners from Brazil and Denmark. Skewing of HLA-G allele distribution was replicated in sASD children; in particular, the HLA-G*01:03 allele, associated with reduced fetal tolerogenicity and development of myeloid leukemia, was more common in both ASD groups compared to controls (p_c = 1 × 10^-3; OR:3.5, 95%CI: 1.8-6.8). However, given the lack of data on HLA-G*01:03 allelic distribution among Sardinian healthy subjects, we cannot exclude a population effect. These data confirm an association of HLA-G locus with ASD development, particularly with those alleles linked to a lower expression of tolerogenic HLA-G protein, thus warranting further studies on HLA-G polymorphism distribution in different ASD populations.

Genetic Polymorphism of HLA-G 14-bp Insertion/Deletion in Pancreas Transplant Recipients and Its Association With Type 1 Diabetes Mellitus

OBJECTIVES

Human leukocyte antigen-G is an immuno-modulatory factor that affects acute allograft rejection and autoimmune diseases such as type 1 diabetes mellitus. In this study, possible associations between human leukocyte antigen-G 14-bp insertion/deletion polymorphism and acute pancreas rejection were investigated.

MATERIALS AND METHODS

Human leukocyte antigen-G genotyping was assessed in 102 Iranian pancreas transplant recipients (including 41 with acute rejection and 61 with nonacute rejection). Results were compared with 100 individuals in a normal control group.

RESULTS

No significant differences in genotype frequencies of human leukocyte antigen-G 14-bp insertion / deletion were observed in recipients who had acute rejection episodes. On the other hand, the insertion / insertion genotype was a risk factor for susceptibility to type 1 diabetes mellitus (odds ratio = 3.82, 95% confidence interval, 1.37- 11.22; P = .005).

CONCLUSIONS

Our results provided evidence revealing that the human leukocyte antigen-G insertion / insertion genotype might be involved in the pathogenesis of type 1 diabetes mellitus.

Immune Abnormalities in Autism Spectrum Disorder-Could They Hold Promise for Causative Treatment?

Autism spectrum disorders (ASD) are characterized by impairments in language and communication development, social behavior, and the occurrence of stereotypic patterns of behavior and interests. Despite substantial speculation about causes of ASD, its exact etiology remains unknown. Recent studies highlight a link between immune dysfunction and behavioral traits. Various immune anomalies, including humoral and cellular immunity along with abnormalities at the molecular level, have been reported. There is evidence of altered immune function both in cerebrospinal fluid and peripheral blood. Several studies hypothesize a role for neuroinflammation in ASD and are supported by brain tissue and cerebrospinal fluid analysis, as well as evidence of microglial activation. It has been shown that immune abnormalities occur in a substantial number of individuals with ASD. Identifying subgroups with immune system dysregulation and linking specific cellular immunophenotypes to different symptoms would be key to defining a group of patients with immune abnormalities as a major etiology underlying behavioral symptoms. These determinations would provide the opportunity to investigate causative treatments for a defined patient group that may specifically benefit from such an approach. This review summarizes recent insights into immune system dysfunction in individuals with ASD and discusses the potential implications for future therapies.

HLA-class II haplotypes and Autism Spectrum Disorders

Infections and autoimmunity are associated with autism spectrum disorders (ASD), with both strongly influenced by the genetic regulation of the human leukocyte antigen (HLA) system. The relationship between ASD and the HLA genetic diversity requires further investigation. Using a case control design, the distribution of HLA class II-DRB1 and DQB1 alleles, genotypes and haplotypes were investigated in ASD patients, versus healthy controls (HC). ASD patients meeting DSM-IV TR criteria and HC (474 and 350 respectively) were genotyped at medium resolution using a Luminex-based SSO technology. Comparisons of genotypes, allele frequencies associated with a haplotype analysis were performed. Results indicate: (i) the HLA-DRB1 *11-DQB1*07 haplotype was more prevalent in ASD patients, versus HC (Pc = 0.001), partially replicating previous data and possibly linking to gastro-intestinal (GI)-related pro-inflammatory processes, given that this haplotype associates with pediatric celiac disorders; (ii) the HLA-DRB1 *17-DQB1*02 haplotype was higher in HC, versus ASD patients (Pc = 0.002), indicating that this is a protective haplotype. Using the Autism Diagnostic Interview to assess clinical dimensions, higher scores on social (Pc = 0.006) and non-verbal functioning (Pc = 0.004) associated with the DRB1 *11 DQB1*07 haplotype. Our results support HLA involvement in ASD, with possible relevance to GI and gut-brain axis dysregulation.

The HLA-G Genetic Contribution to Bipolar Disorder: A Trans-Ethnic Replication

Bipolar disorder (BD) is frequently associated with immune dysfunctions. Studying the genetic diversity of the immuno-modulatory human leukocyte antigen (HLA)-G locus in a French BD cohort, we previously reported an association between a functionally relevant 14 bp Ins/Del polymorphism and BD risk. The present study investigated the genetic and expression diversities of HLA-G in a geographically distinct South Indian population-group BD patients, as well as the influence of exposure to the neurotropic Toxoplasma gondii pathogen. Three functionally relevant HLA-G polymorphisms, i.e. HLA-G 14 bp Ins/Del (rs66554220), +3142G>C (rs1063320) and +3187A>G (rs9380142) were genotyped by polymerase chain reaction (PCR) and real-time PCR. Sub-samples of BD patients and healthy controls (HC) were investigated for plasma levels of soluble HLA-G (sHLA-G) isoforms, as well as circulating stigma of T. gondii infection. Findings indicate: (i) the frequency of the HLA-G 14 bp Del/Del genotype was higher in BD cases, as compared to HC; (ii) the HLA-G + 3142 C allele and CC genotype were more prevalent in BD patients than in HC; (iii) sHLA-G levels were significantly higher in BD cases, especially in females and in the early onset sub-group; and (iv) the InsGA haplotype was more prevalent in HC. Our findings further support the genetic contribution of HLA-G to BD risk, as well as indicate relevant expression profiles. Such data may also indicate a potential developmental role in BD etiology, given that HLA-G is an important immune regulator from the intrauterine period and across development.

Understanding Neurodevelopmental Disorders: The Promise of Regulatory Variation in the 3'UTRome

Neurodevelopmental disorders have a strong genetic component, but despite widespread efforts, the specific genetic factors underlying these disorders remain undefined for a large proportion of affected individuals. Given the accessibility of exome sequencing, this problem has thus far been addressed from a protein-centric standpoint; however, protein-coding regions only make up ∼1% to 2% of the human genome. With the advent of whole genome sequencing we are in the midst of a paradigm shift as it is now possible to interrogate the entire sequence of the human genome (coding and noncoding) to fill in the missing heritability of complex disorders. These new technologies bring new challenges, as the number of noncoding variants identified per individual can be overwhelming, making it prudent to focus on noncoding regions of known function, for which the effects of variation can be predicted and directly tested to assess pathogenicity. The 3'UTRome is a region of the noncoding genome that perfectly fulfills these criteria and is of high interest when searching for pathogenic variation related to complex neurodevelopmental disorders. Herein, we review the regulatory roles of the 3'UTRome as binding sites for microRNAs or RNA binding proteins, or during alternative polyadenylation. We detail existing evidence that these regions contribute to neurodevelopmental disorders and outline strategies for identification and validation of novel putatively pathogenic variation in these regions. This evidence suggests that studying the 3'UTRome will lead to the identification of new risk factors, new candidate disease genes, and a better understanding of the molecular mechanisms contributing to neurodevelopmental disorders.

HLA-G coding region polymorphism is skewed in autistic spectrum disorders

Different isoforms of HLA-G protein are endowed with a differential ability to induce allogenic tolerance during pregnancy. As prenatal immune activation is suggested to play a role in the onset of autistic spectrum disorders (ASD), we evaluated HLA G*01:01-*01:06 allelic polymorphism in a cohort of Italian children affected by ASD (N=111) their mothers (N=81), and their healthy siblings (N=39). DNA sequencing analysis of HLA-G exon 2, 3 and 4 was used to obtain HLA-G allelic frequencies; alleles distribution was compared with that of two control groups of Caucasoid couples of multiparous women and their partners from Brazil and Denmark. HLA-G distribution was significantly different in ASD children compared to both control groups (Brazilian p_c=1×10^-4; Danish p_c=1×10^-3). Since HLA-G distribution was similar in the two control groups, their data were pooled. Results indicated that HLA-G*01:01 was significantly less frequent (p_c=1×10^-4; OR:0.5, 95%CI: 0.3-0.7) whereas HLA-G*01:05N was significantly more frequent (p_c=2×10^-3; OR:7.3, 95%CI: 2.4-26.6) in ASD children compared to combined controls. Finally, no clear pattern emerged when HLA-G allelic distribution was analyzed in healthy sibs. Notably, HLA-G allelic distribution found in ASD mothers was similar to that observed in the control subgroup of women with recurrent miscarriages, whilst it was significantly different compared to women without miscarriages (p_c=6×10^-4 df=12). Since HLA-G*01:01 is associated with the elicitation of KIR-mediated tolerogenic responses and HLA-G*01:05N correlates with NK cells activation, results herein indicate that an immune activating milieu during pregnancy is more likely observed in association with the development of ASD, similarly to what occurs in women with recurrent miscarriages.

Neuroinflammation in Autism Spectrum Disorders: Role of High Mobility Group Box 1 Protein

The pathogenesis of autism spectrum disorder (ASD) likely involves genetic and environmental factors, impacting the complex neurodevelopmental and behavioral abnormalities of the disorder. Scientific research studies emerging within the past two decades suggest that immune dysfunction and inflammation have pathogenic influences through different mechanisms, all leading to both a chronic state of low grade inflammation, and alterations in the central nervous system and immune response, respectively. The high mobility group box-1 protein (HMGB1) is an inflammatory marker which has been shown to play a role in inducing and influencing neuroinflammation. Current evidences suggest a possible role in the multiple pathogenic mechanisms of ASD. The aim of this manuscript is to review the major hypothesis for ASD pathogenesis, with specific regards to the immunological ones, and to provide a comprehensive review of the current data about the association between HMGB1 and ASD. A systematic search has been carried out through Medline via Pubmed to identify all original articles published in English, on the basis of the following keywords: “HMGB1”, “autism”, “autism spectrum disorder”, “neuroinflammation”, and “child”.

HLA-G∗14bp Insertion and the KIR2DS1-HLAC2 Complex Impact on Behavioral Impairment in Children with Autism Spectrum Disorders

Activating KIR-HLA-C ligand complexes and HLA-G∗14bp insertion/deletion (+/-) polymorphism were associated to Autism Spectrum Disorders (ASD) and were suggested to correlate with inflammation during fetal development. We evaluated whether HLA-G∗14bp(+/-) and KIR-HLA-C complexes are associated with cognitive and behavioral scores and EEG profile in 119 ASD children (58 from Sardinia, 61 from Peninsular Italy). KIR2DS1-C2; KIR2DS2-C1; KIR2DL1-C2; KIR2DL2-C1; KIR2DL3-C1 and HLA-G∗14bp(+/-) were molecularly genotyped by Single Specific Primer PCR and gel electrophoresis. Univariate linear model analysis adjusted for age, gender and provenience showed statistically higher scores of Childhood Autism Rating Scale (CARS) and Autistic Core Behavior in KIR2DS1-C2+/HLA-G∗14bp+ASD children (43.7±1.5, p=0.03; 3.3±0.1, p=0.03, respectively). These results suggested a synergistic polygenic association of KIR2DS1-HLAC2+/HLA-G∗14bp+ pattern with behavioral impairment in ASD children.

The Role of the Immune System in Autism Spectrum Disorder

Autism is a neurodevelopmental disorder characterized by deficits in communication and social skills as well as repetitive and stereotypical behaviors. While much effort has focused on the identification of genes associated with autism, research emerging within the past two decades suggests that immune dysfunction is a viable risk factor contributing to the neurodevelopmental deficits observed in autism spectrum disorders (ASD). Further, it is the heterogeneity within this disorder that has brought to light much of the current thinking regarding the subphenotypes within ASD and how the immune system is associated with these distinctions. This review will focus on the two main axes of immune involvement in ASD, namely dysfunction in the prenatal and postnatal periods. During gestation, prenatal insults including maternal infection and subsequent immunological activation may increase the risk of autism in the child. Similarly, the presence of maternally derived anti-brain autoantibodies found in ~20% of mothers whose children are at risk for developing autism has defined an additional subphenotype of ASD. The postnatal environment, on the other hand, is characterized by related but distinct profiles of immune dysregulation, inflammation, and endogenous autoantibodies that all persist within the affected individual. Further definition of the role of immune dysregulation in ASD thus necessitates a deeper understanding of the interaction between both maternal and child immune systems, and the role they have in diagnosis and treatment.

Common Genetic Variants Found in HLA and KIR Immune Genes in Autism Spectrum Disorder

The “common variant—common disease” hypothesis was proposed to explain diseases with strong inheritance. This model suggests that a genetic disease is the result of the combination of several common genetic variants. Common genetic variants are described as a 5% frequency differential between diseased vs. matched control populations. This theory was recently supported by an epidemiology paper stating that about 50% of genetic risk for autism resides in common variants. However, rare variants, rather than common variants, have been found in numerous genome wide genetic studies and many have concluded that the “common variant—common disease” hypothesis is incorrect. One interpretation is that rare variants are major contributors to genetic diseases and autism involves the interaction of many rare variants, especially in the brain. It is obvious there is much yet to be learned about autism genetics. Evidence has been mounting over the years indicating immune involvement in autism, particularly the HLA genes on chromosome 6 and KIR genes on chromosome 19. These two large multigene complexes have important immune functions and have been shown to interact to eliminate unwanted virally infected and malignant cells. HLA proteins have important functions in antigen presentation in adaptive immunity and specific epitopes on HLA class I proteins act as cognate ligands for KIR receptors in innate immunity. Data suggests that HLA alleles and KIR activating genes/haplotypes are common variants in different autism populations. For example, class I allele (HLA-A2 and HLA-G 14 bp-indel) frequencies are significantly increased by more than 5% over control populations (Table 2). The HLA-DR4 Class II and shared epitope frequencies are significantly above the control populations (Table 2). Three activating KIR genes: 3DS1, 2DS1, and 2DS2 have increased frequencies of 15, 22, and 14% in autism populations, respectively. There is a 6% increase in total activating KIR genes in autism over control subjects. And, more importantly there is a 12% increase in activating KIR genes and their cognate HLA alleles over control populations (Torres et al., 2012a). These data suggest the interaction of HLA ligand/KIR receptor pairs encoded on two different chromosomes is more significant as a ligand/receptor complex than separately in autism.

The impact of HLA-G 3' UTR variants and sHLA-G on risk and clinical correlates of schizophrenia

The Major Histocompatibility Complex (MHC)/Human Leukocyte Antigen (HLA) is known to influence the pathogenesis of several complex human diseases resulting from gene-environmental interactions. Recently, it has emerged as one of the risk determinants of schizophrenia. The HLA-G protein (a non-classical MHC class I molecule), encoded by the HLA-G gene, is shown to play important role in embryonic development. Importantly, its genetic variations and aberrant expression have been implicated in pregnancy complications like preeclampsia, inflammation, and autoimmunity. Converging evidence implicates these phenomena as risk mechanisms of schizophrenia. However, the functional implications of HLA-G in schizophrenia are yet to be empirically examined. The impact of two functional polymorphisms [14bp Insertion/Deletion (INDEL) and +3187 A>G] and soluble HLA-G (sHLA-G) levels on schizophrenia risk was evaluated. In this exploratory study, the Ins/Ins genotype of 14bp INDEL was found to confer a strong risk for schizophrenia. Further, low levels of sHLA-G were shown to have a significant impact on Clinical Global Impression (CGI) severity in people with schizophrenia.

Dectin-1 Polymorphism: A Genetic Disease Specifier in Autism Spectrum Disorders?

Introduction

In autism spectrum disorders (ASD), complex gene-environment interactions contribute to disease onset and progress. Given that gastro-intestinal dysfunctions are common in ASD, we postulated involvement of microbial dysbiosis in ASD and investigated, under a case-control design, the influence of DNA polymorphisms in the CLEC7A gene that encodes a pivotal fungal sensor, Dectin-1.

Material and methods

DNAs from 478 ASD patients and 351 healthy controls (HC) were analyzed for the CLEC7A rs16910631G/A and rs2078178 A/G single nucleotide polymorphisms (SNPs). Differences in the distribution of allele, genotype and haplotype by Chi-square testing and nonparametric analysis by Kruskal-Wallis/Mann–Whitney tests, where appropriate, were performed. The free statistical package R.2.13 software was used for the statistical analysis.

Results

We found that the CLEC7A rs2078178 G allele and GG genotype were more prevalent in HC as compared to ASD but failed to reach statistical significance for the latter (pc = 0.01, 0.06 respectively). However, after phenotype-based stratification, the CLEC7A rs2078178 G allele and GG genotype were found to be significantly more frequent in the Asperger group as compared to other ASD subsets (pc = 0.02, 0.01), a finding reinforced by haplotype analysis (rs2078178/rs16910631 G-G/G-G) (pc = 0.002). Further, intellectual quotient (IQ)-based stratification of ASD patients revealed that IQ values increase linearly along the CLEC7A rs2078178 AA, AG and GG genotypes (p = 0.05) and in a recessive manner (GG vs. AA+AG p = 0.02), further confirmed by haplotype distribution (CLEC7A rs2078178-16910631; A-G/A-G, A-G/G-G and G-G/G-G, p = 0.02, G-G/G-G vs. others, p = 0.01).

Conclusion

Our data suggest that the genetic diversity of CLEC7A gene influences the ASD phenotype by behaving as a disease specifier and imply that the genetic control of innate immune response could determine the ASD phenotype.

Serotonin mediated immunoregulation and neural functions: Complicity in the aetiology of autism spectrum disorders

Serotonergic system has long been implicated in the aetiology of autism spectrum disorders (ASD), since platelet hyperserotonemia is consistently observed in a subset of autistic patients, who respond well to selective serotonin reuptake inhibitors. Apart from being a neurotransmitter, serotonin functions as a neurotrophic factor directing brain development and as an immunoregulator modulating immune responses. Serotonin transporter (SERT) regulates serotonin level in lymphoid tissues to ensure its proper functioning in innate and adaptive responses. Immunological molecules such as cytokines in turn regulate the transcription and activity of SERT. Dysregulation of serotonergic system could trigger signalling cascades that affect normal neural-immune interactions culminating in neurodevelopmental and neural connectivity defects precipitating behavioural abnormalities, or the disease phenotypes. Therefore, we suggest that a better understanding of the cross talk between serotonergic genes, immune systems and serotonergic neurotransmission will open wider avenues to develop pharmacological leads for addressing the core ASD behavioural deficits.