Folate Receptor Autoantibodies Research Articles

Identifying Rare Genetic Variants of Immune Mediators as Risk Factors for Autism Spectrum Disorder.

Autism spectrum disorder (ASD) affects more than 1% of children, and there is no viable pharmacotherapeutic agent to treat the core symptoms of ASD. Studies have shown that children with ASD show changes in their levels of immune response molecules. Our previous studies have shown that ASD is more common in children with folate receptor autoantibodies. We also found that children with ASD have abnormal gut immune function, which was characterized by a significant increase in the content of immunoglobulin A and an increase in gut-microbiota-associated epitope diversity. These studies suggest that the immune mechanism plays an important role in the occurrence of ASD. The present study aims to systematically assess gene mutations in immune mediators in patients with ASD. We collected genetic samples from 72 children with ASD (2–12 years old) and 107 healthy controls without ASD (20–78 years old). We used our previously-designed immune gene panel, which can capture cytokine and receptor genes, the coding regions of MHC genes, and genes of innate immunity. Target region sequencing (500×) and bioinformatics analytical methods were used to identify variants in immune response genes associated with patients with ASD. A total of 4 rare variants were found to be associated with ASD, including HLA-B: p.A93G, HLA-DQB1: p.S229N, LILRB2: p.R322H, and LILRB2: c.956-4C>T. These variants were present in 44.44% (32/72) of the ASD patients and were detected in 3.74% (4/107) of the healthy controls. We expect these genetic variants will serve as new targets for the clinical genetic assessment of ASD, and our findings suggest that immune abnormalities in children with ASD may have a genetic basis.

Folate Receptor Alpha Autoantibodies in Autism Spectrum Disorders: Diagnosis, Treatment and Prevention.

Folate deficiency and folate receptor autoimmune disorder are major contributors to infertility, pregnancy related complications and abnormal fetal development including structural and functional abnormalities of the brain. Food fortification and prenatal folic acid supplementation has reduced the incidence of neural tube defect (NTD) pregnancies but is unlikely to prevent pregnancy-related complications in the presence of folate receptor autoantibodies (FRAb). In pregnancy, these autoantibodies can block folate transport to the fetus and in young children, folate transport to the brain. These antibodies are prevalent in neural tube defect pregnancies and in developmental disorders such as cerebral folate deficiency (CFD) syndrome and autism spectrum disorder (ASD). In the latter conditions, folinic acid treatment has shown clinical improvement in some of the core ASD deficits. Early testing for folate receptor autoantibodies and intervention is likely to result in a positive outcome. This review discusses the first identification of FRAb in women with a history of neural tube defect pregnancy and FRAb’s association with sub-fertility and preterm birth. Autoantibodies against folate receptor alpha (FRα) are present in about 70% of the children with a diagnosis of ASD, and a significant number of these children respond to oral folinic acid with overall improvements in speech, language and social interaction. The diagnosis of folate receptor autoimmune disorder by measuring autoantibodies against FRα in the serum provides a marker with the potential for treatment and perhaps preventing the pathologic consequences of folate receptor autoimmune disorder.

First case report of cerebral folate deficiency caused by a novel mutation of FOLR1 gene in a Chinese patient

BackgroundCerebral folate deficiency (CFD) is a neurological disease, hallmarked by remarkable low concentrations of 5-methyltetrahydrofolic acid (5-MTHF) in cerebrospinal fluid (CSF). The primary causes of CFD include the presence of folate receptor (FR) autoantibodies, defects of FR encoding gene FOLR1, mitochondrial diseases and congenital abnormalities in folate metabolism.Case presentationHere we first present a Chinese male CFD patient whose seizure onset at 2 years old with convulsive status epilepticus. Magnetic Resonance Imaging (MRI) revealed the development of encephalomalacia, laminar necrosis in multiple lobes of the brain and cerebellar atrophy. Whole Exome Sequencing (WES) uncovered a homozygous missense variant of c.524G > T (p.C175F) in FOLR1 gene. Further laboratory tests demonstrated the extremely low level of 5-MTHF in the CSF from this patient, which was attributed to cerebral folate transport deficiency. Following the intravenous and oral treatment of calcium folinate, the concentrations of 5-MTHF in CSF were recovered to the normal range and seizure symptoms were relieved as well.ConclusionsOne novel variation of FOLR1 was firstly identified from a Chinese male patient with tonic-clonic seizures, developmental delay, and ataxia. The WES and laboratory results elucidated the etiology of the symptoms. Clinical outcomes were improved by early diagnosis and proper treatment.

Oxidative Stress, Folate Receptor Autoimmunity, and CSF Findings in Severe Infantile Autism.

Background Biomarkers such as oxidative stress, folate receptor alpha (FRα) autoimmunity, and abnormal brain serotonin turnover are common in autism. Methods Oxidative stress biomarkers with pro- and antioxidants were measured in the severe form of infantile autism (n = 38) and controls (n = 24). Children and parents had repeated testing for serum FR autoantibodies, spinal fluid dopamine and serotonin metabolites, pterins, and N5-methyltetrahydrofolate (MTHF). Statistical analysis assessed correlations between variables. Genetic analysis included the SLC6A4 and SLC29A4 genes encoding synaptic serotonin reuptake proteins. Results Compared to controls, the autism group showed a significant increase in oxidative DNA damage in lymphocytes, plasma ceruloplasmin and copper levels with a high copper/zinc ratio, thiol proteins, and superoxide dismutase (SOD) activity. Vitamin C levels were significantly diminished. In most autistic patients, the vitamin A (64%) and D (70%) levels were low. Serum FR autoantibodies fluctuating over 5–7 week periods presented in 68% of all autistic children, 41% of parents vs. 3.3% of control children and their parents. CSF showed lowered serotonin 5-hydroxyindole acetic acid (5HIAA) metabolites in 13 (34%), a low 5HIAA to HVA (dopamine metabolite) ratio in 5 (13%), low 5HIAA and MTHF in 2 (5%), and low MTHF in 8 patients (21%). A known SLC6A4 mutation was identified only in 1 autistic child with low CSF 5HIAA and a novel SLC29A4 mutation was identified in identical twins. Low CSF MTHF levels among only 26% of subjects can be explained by the fluctuating FR antibody titers. Two or more aberrant pro-oxidant and/or antioxidant factors predisposed to low CSF serotonin metabolites. Three autistic children having low CSF 5HIAA and elevated oxidative stress received antioxidative supplements followed by CSF 5HIAA normalisation. Conclusion In autism, we found diverse combinations for FR autoimmunity and/or oxidative stress, both amenable to treatment. Parental and postnatal FR autoantibodies tend to block folate passage to the brain affecting folate-dependent pathways restored by folinic acid treatment, while an abnormal redox status tends to induce reduced serotonin turnover, corrected by antioxidant therapy. Trial Registration. The case-controlled study was approved in 2008 by the IRB at Liège University (Belgian Number: B70720083916). Lay Summary. Children with severe infantile autism frequently have serum folate receptor autoantibodies that block the transport of the essential vitamin folate across the blood-brain barrier to the brain. Parents are often asymptomatic carriers of these serum folate receptor autoantibodies, which in mothers can block folate passage across the placenta to their unborn child. This folate deficiency during the child's intrauterine development may predispose to neural tube defects and autism. Oxidative stress represents a condition with the presence of elevated toxic oxygen derivatives attributed to an imbalance between the formation and protection against these toxic reactive oxygen derivatives. Oxidative stress was found to be present in autistic children where these reactive oxygen derivatives can cause damage to DNA, which changes DNA function and regulation of gene expression. In addition, excessive amounts of these toxic oxygen derivatives are likely to damage the enzyme producing the neuromessenger serotonin in the brain, diminished in about 1/3 of the autistic children. Testing children with autism for oxidative stress and its origin, as well as testing for serum folate receptor autoantibodies, could open new approaches towards more effective treatments.

An Examination of Changes in Urinary Metabolites and Behaviors with the Use of Leucovorin Calcium in Children with Autism Spectrum Disorder (ASD)

Children with autism spectrum disorder (ASD) have been found to have a high prevalence of folate receptor auto-antibodies (FRAA), which may impair the normal transport of folate from blood into the cerebrospinal fluid (CSF). Leucovorin calcium (LC) is believed to bypass the folate transport system and restore function. We sought to examine changes in behavior and urinary metabolites in children and young adults with ASD being treated with LC. Students attending a K-12 school for ASD were recruited for an open-label, 12-week study of high-dose LC (2 mg/kg/day, max dose 50 mg/day). The primary outcome measures were the mean changes in the Aberrant Behavior Checklist (ABC) and the Social Responsiveness Scale (SRS). We also examined changes in Pediatric Quality of Life (PedsQL) and urinary metabolites. Changes were assessed with paired sample t-tests. Twelve students aged 13 to 19 (2 girls, 10 boys) completed the study. The parent-reported SRS showed a non-significant decrease (improvement) of 7.8 points (95% CI − 1.6 to 17.3, p = 0.095), and the ABC showed a non-significant decrease of 2.4 points (95% CI − 6.4 to 11.3, p = 0.56). The teacher-reported ABC and the parent-reported PedsQL showed very little change. Urinary metabolites with the greatest changes were involved in folate, phosphatidylcholine, and tocopherol metabolism. In an open-label study of school-aged children with ASD, LC treatment did not lead to significant improvements. The parent-reported SRS showed a non-significant improvement of 7.8 points, which is clinically important and worthy of future study with larger samples. The potential benefits of LC may be limited to children with a specific physiological abnormality (e.g., FRAA status) and may require a targeted treatment approach. Urinary metabolites may be a useful tool to identify children who are likely to respond to treatment.

Targeted Biomedical Treatment for Autism Spectrum Disorders.

A diagnosis of autism spectrum disorders (ASD) represents presentations with impairment in communication and behaviour that vary considerably in their clinical manifestations and etiology as well as in their likely pathophysiology. A growing body of data indicates that the deleterious effect of oxidative stress, mitochondrial dysfunction, immune dysregulation and neuroinflammation, as well as their interconnections are important aspects of the pathophysiology of ASD. Glutathione deficiency decreases the mitochondrial protection against oxidants and tumor necrosis factor (TNF)-α; immune dysregulation and inflammation inhibit mitochondrial function through TNF-α; autoantibodies against the folate receptors underpin cerebral folate deficiency, resulting in disturbed methylation, and mitochondrial dysfunction. Such pathophysiological processes can arise from environmental and epigenetic factors as well as their combined interactions, such as environmental toxicant exposures in individuals with (epi)genetically impaired detoxification. The emerging evidence on biochemical alterations in ASD is forming the basis for treatments aimed to target its biological underpinnings, which is of some importance, given the uncertain and slow effects of the various educational interventions most commonly used. Literature-based review of the biomedical treatment options for ASD that are derived from established pathophysiological processes. Most proposed biomedical treatments show significant clinical utility only in ASD subgroups, with specified pre-treatment biomarkers that are ameliorated by the specified treatment. For example, folinic acid supplementation has positive effects in ASD patients with identified folate receptor autoantibodies, whilst the clinical utility of methylcobalamine is apparent in ASD patients with impaired methylation capacity. Mitochondrial modulating cofactors should be considered when mitochondrial dysfunction is evident, although further research is required to identify the most appropriate single or combined treatment. Multivitamins/multiminerals formulas, as well as biotin, seem appropriate following the identification of metabolic abnormalities, with doses tapered to individual requirements. A promising area, requiring further investigations, is the utilization of antipurinergic therapies, such as low dose suramin. The assessment and identification of relevant physiological alterations and targeted intervention are more likely to produce positive treatment outcomes. As such, current evidence indicates the utility of an approach based on personalized and evidence-based medicine, rather than treatment targeted to all that may not always be beneficial (primum non nocere).

High prevalence of serum folate receptor autoantibodies in children with autism spectrum disorders

Background: Supplementation of folic acid by pregnant mothers is thought to lower the risk of autism spectrum disorders (ASDs) in the offspring. Folic acid is taken up by cells via receptors with high affinity for folate and reduced folic acid derivatives. However, this is blocked by the presence of folate receptor autoantibodies (FRAA). Cerebral FRAA have been detected with high frequency in children with ASDs, suggesting the existence of a link between folic acid uptake and disease aetiology.Methods: We investigated the frequency of FRAA in serum samples from 40 children with ASDs and 42 gender- and age-matched children with typical development (TD). Serum FRAA concentrations were measured by enzyme-linked immunosorbent assay.Results: We found a significant difference in the frequency of serum FRAA in the two study cohorts. Serum FRAA were present in 77.5% (31/40) of children with ASDs compared with 54.8% (23/42) of TD children (p = 0.03746, Fischer’s exact test). Thus, serum FRAA are more prevalent in children with ASDs than in TD children.Conclusions: Our data suggest that children with ASDs may have defects in folic acid absorption that play a role in the onset of ASDs.

Gene variants in the folate pathway are associated with increased levels of folate receptor autoantibodies.

Folate receptors (FRs) facilitate embryonic uptake of folates and are important for proper early embryonic development. There is accumulating evidence that blocking FR autoantibodies contribute to developmental diseases. However, genetic factors associated with the expression of FR autoantibodies remain unknown. We investigated the effects of genetic polymorphisms in folate pathway genes on FR autoantibody titers in women. We recruited 302 pregnant women in China. The FR antigen-down immunoassay was used to measure levels of FR autoantibodies including human immunoglobulin G (IgG) and immunoglobulin M (IgM) in maternal plasma. Genotypes were identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry and polymerase chain reaction methods. General linear model was used to analyze the effects of genetic variants on FR autoantibody levels. Significant associations were observed between genotypic variations and levels of FR autoantibodies. Plasma levels of FR autoantibodies in women with the TT genotype at MTHFR rs1801133 were significantly higher than those of women with the CC genotype (IgG: β = 0.62, 95% CI 0.21-1.04; IgM: β = 0.42, 95% CI 0.12-0.72). For DNMT3A rs7560488, the level of FR autoantibody IgG significantly increased in the TT genotype compared with CC genotype (β = 0.90, 95% CI 0.20-1.59). For MTHFD2 rs828903, genotype GG was associated with elevated levels of FR autoantibody IgM compared to the AA genotype (β = 0.60, 95% CI 0.10-1.10). No association was detected between genetic variants of the DHFR gene with FR autoantibodies levels. Genetic variations in MTHFR, DNMT3A, and MTHFD2 genes were associated with elevated plasma levels of FR autoantibodies.

Genetic assessment and folate receptor autoantibodies in infantile-onset cerebral folate deficiency (CFD) syndrome

IntroductionCerebral folate deficiency (CFD) syndromes are defined as neuro-psychiatric conditions with low CSF folate and attributed to different causes such as autoantibodies against the folate receptor-alpha (FR) protein that can block folate transport across the choroid plexus, FOLR1 gene mutations or mitochondrial disorders. High-dose folinic acid treatment restores many neurologic deficits. Study aims and methodsAmong 36 patients from 33 families the infantile-onset CFD syndrome was diagnosed based on typical clinical features and low CSF folate. All parents were healthy. Three families had 2 affected siblings, while parents from 4 families were first cousins.We analysed serum FR autoantibodies and the FOLR1 and FOLR2 genes. Among three consanguineous families homozygosity mapping attempted to identify a monogenetic cause. Whole exome sequencing (WES) was performed in the fourth consanguineous family, where two siblings also suffered from polyneuropathy as an atypical finding. ResultsBoys (72%) outnumbered girls (28%). Most patients (89%) had serum FR autoantibodies fluctuating over 5–6 weeks. Two children had a genetic FOLR1 variant without pathological significance. Homozygosity mapping failed to detect a single autosomal recessive gene. WES revealed an autosomal recessive polynucleotide kinase 3´phosphatase (PNKP) gene abnormality in the siblings with polyneuropathy. DiscussionInfantile-onset CFD was characterized by serum FR autoantibodies as its predominant pathology whereas pathogenic FOLR1 gene mutations were absent. Homozygosity mapping excluded autosomal recessive inheritance of any single responsible gene. WES in one consanguineous family identified a PNKP gene abnormality that explained the polyneuropathy and also its contribution to the infantile CFD syndrome because the PNKP gene plays a dual role in both neurodevelopment and immune-regulatory function. Further research for candidate genes predisposing to FRα-autoimmunity is suggested to include X-chromosomal and non-coding DNA regions.

Folate receptor autoantibodies are prevalent in children diagnosed with autism spectrum disorder, their normal siblings and parents.

Folate is an essential nutrient during fetal and infant development. Autoantibodies against the folate receptor alpha can block folate transport from the mother to the fetus and to the brain in infants. Children diagnosed with autism and their immediate family members were evaluated for the prevalence of folate receptor autoantibodies. The autoantibody was highly prevalent in affected families with similar distribution in parents, normal siblings and affected children. The presence of these antibodies appears to have a familial origin and may contribute to developmental deficits when combined with other factors.

Corrigendum for: Levels of folate receptor autoantibodies in maternal and cord blood and risk of neural tube defects in a Chinese population, 106:685-695 (10.1002/bdra.23517).

When the article listed above was published the authors in the “Correspondence to:” footnote were listed in the incorrect order. The corrected footnote is listed below. The authors apologize for this error and any confusion that it may have caused. *Correspondence to: Rongwei Ye, Institute of Reproductive and Child Health/Ministry of Health Key Laboratory of Reproductive Health, Department of Epidemiology and Biostatistics, School of Public Health Peking University, 38 Xueyuan Road, Beijing, 100191, China. E-mail: [email protected]; Linlin Wang, Institute of Reproductive and Child Health/Ministry of Health Key Laboratory of Reproductive Health, Department of Epidemiology and Biostatistics, School of Public Health Peking University, 38 Xueyuan Road, Beijing, 100191, China. E-mail: [email protected].

Levels of folate receptor autoantibodies in maternal and cord blood and risk of neural tube defects in a Chinese population

After years of periconceptional folic acid supplementation, the prevalence of neural tube defects (NTDs) remains stable following the remarkable reduction observed immediately after the fortification practice. There is accumulating evidence that folate receptor (FR) autoimmunity may play a role in the etiology of folate-sensitive NTDs. From 2011 to 2013, 118 NTD cases and 242 healthy controls were recruited from a population-based birth defects surveillance system in Northern China. Enzyme-linked immunosorbent assay was used to measure FR autoantibodies in maternal and cord blood. Logistic regression models were used to estimate the odds ratios (OR) and 95% confidence intervals (95% CI). Plasma FR autoantibodies levels were significantly elevated in mothers of infants with NTDs compared with mothers of healthy controls. Using the lowest tertile as the referent group, 2.20-fold (95% CI, 0.71-6.80) and 5.53-fold increased odds (95% CI, 1.90-16.08) of NTDs were observed for the second and third tertile of immunoglobulin G (IgG), respectively, and the odds of NTDs for each successive tertile of IgM was 0.98 (95% CI, 0.35-2.75) and 3.49 (95% CI, 1.45-8.39), respectively. A dose-response relationship was found between FR autoantibodies levels and risk of NTDs (P < 0.001 for IgG, P = 0.002 for IgM). The same pattern was observed in both subtypes of spina bifida and anencephaly. No significant difference in levels of cord blood FR autoantibodies was observed. Higher levels of FR autoimmunity in maternal plasma are associated with elevated risk of NTDs in a dose-response manner. Birth Defects Research (Part A) 106:685-695, 2016. © 2016 Wiley Periodicals, Inc.

Immunological abnormalities in young patients with dysautonomia

Background: Dysautonomia is a poorly understood condition of unknown etiology. Many patients with dysautonomia have symptoms suggestive of immune dysregulation but there is limited information on their immunologic phenotype. Our aim is to characterize the association between dysautonomia and immunity in a group of young patients with this condition. Methods: A retrospective chart review was conducted in a group of patients with dysautonomia, documented by an abnormal head-up tilt test, referred for immune evaluation to the Allergy-Immunology clinic at our institution (2007–2014). Their clinical history and immune laboratory studies (e.g. immunoglobulin levels, specific antibody responses, ANA, anti-SSA/SSO, dysautonomia autoimmune profile, serum cytokines) were reviewed. Results: Twenty patients (3 males, 17 females), mean age of 19.9 years (15–34), were evaluated. Symptoms suggestive of immune dysfunction included arthralgia (7), joint swelling (3), backache (2), dermatitis (5), alopecia (2), sicca (4), Raynaud’s (1), and recurrent infections (5). Five patients (25%) had autoantibodies (i.e. anti-SSA, ANA, anti-GAD65, folate receptor autoantibodies), and 9 of 14 patients (64%), had elevated serum cytokines. Severe dysautonomia was present in one patient with IDDM and 4 patients with B-cell immunodeficiency, all of which had other coexisting autoimmune problems. Conclusions: Young patients with dysautonomia may suffer from immune dysregulation and the severity of their disease is associated with severe dysautonomia. It remains to be determined if this immune dysregulation is a primary or secondary process.

Role of angiotensin type 1A receptors in the sympathetic activation of angiotensin-dependent hypertension

head-up tilt test, referred for immune evaluation to the AllergyImmunology clinic at our institution (2007–2014). Their clinical history and immune laboratory studies (e.g. immunoglobulin levels, specific antibody responses, ANA, anti-SSA/SSO, dysautonomia autoimmune profile, serum cytokines) were reviewed. Results: Twenty patients (3 males, 17 females), mean age of 19.9 years (15–34), were evaluated. Symptoms suggestive of immune dysfunction included arthralgia (7), joint swelling (3), backache (2), dermatitis (5), alopecia (2), sicca (4), Raynaud’s (1), and recurrent infections (5). Five patients (25%) had autoantibodies (i.e. anti-SSA, ANA, anti-GAD65, folate receptor autoantibodies), and 9 of 14 patients (64%), had elevated serum cytokines. Severe dysautonomia was present in one patient with IDDM and 4 patients with B-cell immunodeficiency, all of which had other coexisting autoimmune problems. Conclusions: Young patients with dysautonomia may suffer from immune dysregulation and the severity of their disease is associated with severe dysautonomia. It remains to be determined if this immune dysregulation is a primary or secondary process.

The role of folate receptor autoantibodies in preterm birth

ObjectiveCellular uptake of folate is mediated by folate receptor (FR)α. Prior studies indicate that a FRα autoantibody (FRAb) is implicated in poor pregnancy outcomes. The aims of this study were to determine the prevalence of FRAbs in women with preterm and term pregnancies, and to investigate the role of maternal FRAbs in preterm birth. MethodsThis prospective observational study included 23 mothers and 25 preterm infants (two twin births) born at gestational age (GA) ≤32 wk and/or birth weight ≤1500 g (group 1) and 25 mother–term infant pairs (infants born at GA ≥37 wk, group 2). Blocking and binding FRAbs in maternal and in cord blood were determined. The association between maternal FRAbs and pregnancy outcome was measured using multiple logistic regression, adjusted for maternal age and previous preterm birth. ResultsThe prevalence of FRAbs was 65.2% in women with preterm birth, which was twofold higher than in those with term pregnancy (28%; relative risk [RR], 2.3; 95% confidence interval [CI], 1.2–4.7). The prevalence of FRAbs in preterm infants (64%) was significantly higher than in term infants (24%; RR, 2.7; 95% CI, 1.3–5.7). Pregnant women with positive FRAbs had 4.9 times higher odds of having preterm birth (odds ratio, 4.9; 95% CI, 1.4–17.7), adjusted for maternal age and previous preterm birth. ConclusionsThese findings suggest that the presence of FRAbs might be a contributing factor to preterm birth, which could be prevented with appropriate testing and therapeutic interventions. Further studies are warranted to investigate the possible mechanisms of fetal sensitization resulting in FRAb production in utero and its possible clinical correlates.

Folinic acid treatment for schizophrenia associated with folate receptor autoantibodies

BackgroundAuto-antibodies against folate receptor alpha (FRα) at the choroid plexus that block N5-methyltetrahydrofolate (MTHF) transfer to the brain were identified in catatonic schizophrenia. Acoustic hallucinations disappeared following folinic acid treatment. Folate transport to the CNS prevents homocysteine accumulation and delivers one-carbon units for methyl-transfer reactions and synthesis of purines. The guanosine derivative tetrahydrobiopterin acts as common co-factor for the enzymes producing dopamine, serotonin and nitric oxide. MethodsOur study selected patients with schizophrenia unresponsive to conventional treatment. Serum from these patients with normal plasma homocysteine, folate and vitamin B12 was tested for FR autoantibodies of the blocking type on serial samples each week. Spinal fluid was analyzed for MTHF and the metabolites of pterins, dopamine and serotonin. The clinical response to folinic acid treatment was evaluated. ResultsFifteen of 18 patients (83.3%) had positive serum FR auto-antibodies compared to only 1 in 30 controls (3.3%) (χ2=21.6; p<0.0001). FRα antibody titers in patients fluctuated over time varying between negative and high titers, modulating folate flux to the CNS, which explained low CSF folate values in 6 and normal values in 7 patients. The mean±SD for CSF MTHF was diminished compared to previously established controls (t-test: 3.90; p=0.0002).A positive linear correlation existed between CSF MTHF and biopterin levels. CSF dopamine and serotonin metabolites were low or in the lower normal range. Administration of folinic acid (0.3–1mg/kg/day) to 7 participating patients during at least six months resulted in clinical improvement. ConclusionAssessment of FR auto-antibodies in serum is recommended for schizophrenic patients. Clinical negative or positive symptoms are speculated to be influenced by the level and evolution of FRα antibody titers which determine folate flux to the brain with up- or down-regulation of brain folate intermediates linked to metabolic processes affecting homocysteine levels, synthesis of tetrahydrobiopterin and neurotransmitters. Folinic acid intervention appears to stabilize the disease process.

Maternal Folic Acid Supplementation and Risk of Autism—Reply

To the Editor: Dr Suren and colleagues reported on the decreased incidence of autistic disorder in children whose mothers received prenatal folic acid supplementation around the time of conception. The study expands on their previous report of an association between prenatal folic acid and severe childhood language delay, a key feature of autism spectrum disorders. Even though the epidemiological study design precludes a demonstration of causation, this study does suggest an association between folate metabolism and the development of autism spectrum disorders. Aberrant folatedependent metabolism and increased oxidative stress have been identified in autism spectrum disorders. Furthermore, cerebral folate receptor autoantibodies have been identified in up to three quarters of children with autism spectrum disorders. Treatment with folinic acid, a metabolically active form of folic acid, in children with autism spectrum disorders positive for folate receptor autoantibodies has led to significantly improved nonverbal communication, language, attention, and stereotypies. There is a dearth of research focusing on metabolic and immunological dysfunction in autism spectrum disorders and the neurobiological underpinnings of these disorders remain largely elusive. The combination of findings from clinical and epidemiological research should prompt heightened interest in and study of folate-related metabolic and immune processes in autism spectrum disorders.

Maternal Folic Acid Supplementation and Risk of Autism

To the Editor: Dr Suren and colleagues reported on the decreased incidence of autistic disorder in children whose mothers received prenatal folic acid supplementation around the time of conception. The study expands on their previous report of an association between prenatal folic acid and severe childhood language delay, a key feature of autism spectrum disorders. Even though the epidemiological study design precludes a demonstration of causation, this study does suggest an association between folate metabolism and the development of autism spectrum disorders. Aberrant folatedependent metabolism and increased oxidative stress have been identified in autism spectrum disorders. Furthermore, cerebral folate receptor autoantibodies have been identified in up to three quarters of children with autism spectrum disorders. Treatment with folinic acid, a metabolically active form of folic acid, in children with autism spectrum disorders positive for folate receptor autoantibodies has led to significantly improved nonverbal communication, language, attention, and stereotypies. There is a dearth of research focusing on metabolic and immunological dysfunction in autism spectrum disorders and the neurobiological underpinnings of these disorders remain largely elusive. The combination of findings from clinical and epidemiological research should prompt heightened interest in and study of folate-related metabolic and immune processes in autism spectrum disorders.

The diagnostic utility of folate receptor autoantibodies in blood

Folate supplementation reduces the risk of neural tube defect (NTD) pregnancy, and folinic acid has been used to correct cerebral folate deficiency (CFD) in children with developmental disorders. In the absence of systemic folate deficiency, the discovery of autoantibodies (AuAbs) to folate receptor α (FRα) that block the uptake of folate offers one mechanism to explain the response to folate in these disorders. The association of FRα AuAbs with pregnancy-related complications, CFD syndrome, and autism spectrum disorders and response to folate therapy is highly suggestive of the involvement of these AuAbs in the disruption of brain development and function via folate pathways. The two types of antibodies identified in the serum of patients are blocking antibody and binding antibody. The two antibodies can be measured by the specific assays described and exert their pathological effects either by functional blocking of folate transport as previously shown or hypothetically by disrupting the FR by an antigen-antibody-mediated inflammatory response. We have identified both IgG and IgM AuAbs in these conditions. The predominant antibodies in women with NTD pregnancy belong to the IgG1 and IgG2 isotype and in CFD children, the IgG1 and IgG4 isotype. This review describes the methods used to measure these AuAbs, their binding characteristics, affinity, cross-reactivity, and potential mechanisms by which folate therapy could work. Because these AuAbs are associated with various pathologies during fetal and neonatal development, early detection and intervention could prevent or reverse the consequences of exposure to these AuAbs.

Role of folate receptor autoantibodies in infantile autism

During pregnancy, maternal folate receptor alpha (FRα) autoantibodies could block folate transfer to the fetus and increase the risk of neural tube defects.1 The prevalence of blocking FRα antibodies in healthy adult women was estimated at 4–7% in Spain,2 9–13% in Ireland3 and 10–15% in the US population.1 A low titer of this antibody in a fraction of the adult population appears to be non-pathologic. Postnatally acquired FR autoantibodies blocking folate transport to the brain have been associated with the infantile-onset cerebral folate deficiency syndrome,4 which in a number of patients manifests as low-functioning autism with neurological deficits.5 In a US population with autism spectrum disorder (ASD), either the blocking- or the binding-type autoantibody was detected in 75% of the children and high-dose folinic-acid supplementation improved the core symptoms of autism in these children.6 We studied a population of infantile autism, non-autistic controls with developmental deficits and their parents in Belgium (research project supported by FNRS Belgium No: 3.4.540.09.F). Serum was tested for FRα-blocking autoantibodies as described previously.4 Plasma homocysteine and serum folate were also measured. The samples were coded and blinded to all analysis.