A systematic, quantitative review of blood autoantibodies in schizophrenia

The relationship between schizophrenia or schizoaffective disorder and type 1 diabetes mellitus: a scoping review of observational studies

OBJECTIVE

Both schizophrenia and type 1 diabetes mellitus (T1D) are known as immune-related disorders. We systematically reviewed observational studies to explore the relationship between schizophrenia or schizoaffective disorder and T1D.

METHODS

A preliminary search of articles was completed using the following databases: Airiti Library, CINAHL Complete (via EBSCOhost), OVID MEDLINE, Embase, and PubMed. Two researchers independently assessed each study's quality based on Joanna Briggs Institute (JBI). A narrative review summarized the potential relationship between the two diseases.

RESULTS

Eleven studies were included in the final analysis. Six observational studies investigated the risk of schizophrenia and schizoaffective disorder in patients with T1D. Two studies showed negative correlations, one showed no correlation, and three showed positive correlations. On the other hand, five studies reported the prevalence of T1D in patients with schizophrenia. Two of them showed positive associations, and three others showed no association. Although the majority of the included studies suggested a positive association between the two medical conditions, these studies were still too heterogeneous to draw consistent results.

CONCLUSION

We found conflicting results regarding the bidirectional relationship between schizophrenia or schizoaffective disorder and T1D. These may stem from differences in study design, sampling methods, or definition of diagnoses, which are essential aspects to consider in future research.

Multiple serum anti-glutamate receptor antibody levels in clozapine-treated/naïve patients with treatment-resistant schizophrenia

BACKGROUND

Glutamatergic function abnormalities have been implicated in the etiology of treatment-resistant schizophrenia (TRS), and the efficacy of clozapine may be attributed to its impact on the glutamate system. Recently, evidence has emerged suggesting the involvement of immune processes and increased prevalence of antineuronal antibodies in TRS. This current study aimed to investigate the levels of multiple anti-glutamate receptor antibodies in TRS and explore the effects of clozapine on these antibody levels.

METHODS

Enzyme linked immunosorbent assay (ELISA) was used to measure and compare the levels of anti-glutamate receptor antibodies (NMDAR, AMPAR, mGlur3, mGluR5) in clozapine-treated TRS patients (TRS-C, n = 37), clozapine-naïve TRS patients (TRS-NC, n = 39), and non-TRS patients (nTRS, n = 35). Clinical symptom severity was assessed using the Positive and Negative Symptom Scale (PANSS), while cognitive function was evaluated using the MATRICS Consensus Cognitive Battery (MCCB).

RESULT

The levels of all four glutamate receptor antibodies in TRS-NC were significantly higher than those in nTRS (p < 0.001) and in TRS-C (p < 0.001), and the antibody levels in TRS-C were comparable to those in nTRS. However, no significant associations were observed between antibody levels and symptom severity or cognitive function across all three groups after FDR correction.

CONCLUSION

Our findings suggest that TRS may related to increased anti-glutamate receptor antibody levels and provide further evidence that glutamatergic dysfunction and immune processes may contribute to the pathogenesis of TRS. The impact of clozapine on anti-glutamate receptor antibody levels may be a pharmacological mechanism underlying its therapeutic effects.

Cytokine alterations in CSF and serum samples of patients with a first episode of schizophrenia: results and methodological considerations

We determined cytokine levels in paired serum/CSF samples from first-episode schizophrenia (FES) participants (n = 20) and controls (n = 21) using a 13-plex immunoassay. Applying strictly-determined detection limits, 12 cytokines were found in serum and two in CSF. Higher serum MCP-1 levels (p = 0.007) were present in FES versus controls, which correlated with serum IgG (R = - 0.750; p = 0.013). Finally, IL-18 levels correlated with body weight in FES (R = 0.691; p = 0.041). This study demonstrates potential limitations in the sensitivity of multiplex cytokine assays for CSF studies in mental disorders and suggests that some published studies in this area should be re-evaluated.

[Mental disorders in patients with systemic lupus erythematosus: association with activity and the course of rheumatic disease]

AIM

To clarify the relationship between the clinical and psychopathological features of mental disorders, clinical and laboratory manifestations of activity and the nature of the course of systemic lupus erythematosus (SLE).

MATERIALS AND METHODS

The study included 119 patients - 98 (82.4%) women, mean age 36.5±12.4 years (M±SD) - with a reliable diagnosis of SLE (EULAR/ACR 2019 criteria), 51 (29.5%) of them - with secondary antiphospholipid syndrome - APS (International criteria of 2006).

RESULTS

Among patients with SLE a high frequency of anxiety-depressive spectrum disorders (ADSD) and cognitive impairment (CI) was revealed. There was an association of greater severity of depression with high SLE activity index, acute/subacute onset of the disease course according to the classification of V.A. Nasonova, relapsing-remitting and chronic active current disease activity patterns of SLE according to the classification of S. Barr - M. Petri. Anxiety disorders were associated with subacute onset and relapsing-remitting disease activity patterns of SLE and were not associated with SLE activity index. Bipolar disorder was detected more often in patients with chronic SLE. Acute psychosis/delirium was associated with acute onset of SLE. Organic CI was associated with APS, chronic onset and long quiescent disease activity patterns of SLE. The episindrome and schizotypal disorder in patients with SLE are more often caused by concomitant APS.

CONCLUSION

Patients with high SLE activity index should be of particular concern to rheumatologists regarding the diagnosis of depressive disorders. Patients with concomitant APS need timely diagnosis and treatment of CI and episindrome in order to improve the prognosis of the disease and the overall quality of life.

Circulating Cell-Free DNA Levels in Psychiatric Diseases: A Systematic Review and Meta-Analysis

The cell-free DNA (cfDNA) levels are known to increase in biological fluids in various pathological conditions. However, the data on circulating cfDNA in severe psychiatric disorders, including schizophrenia, bipolar disorder (BD), and depressive disorders (DDs), is contradictory. This meta-analysis aimed to analyze the concentrations of different cfDNA types in schizophrenia, BD, and DDs compared with healthy donors. The mitochondrial (cf-mtDNA), genomic (cf-gDNA), and total cfDNA concentrations were analyzed separately. The effect size was estimated using the standardized mean difference (SMD). Eight reports for schizophrenia, four for BD, and five for DDs were included in the meta-analysis. However, there were only enough data to analyze the total cfDNA and cf-gDNA in schizophrenia and cf-mtDNA in BD and DDs. It has been shown that the levels of total cfDNA and cf-gDNA in patients with schizophrenia are significantly higher than in healthy donors (SMD values of 0.61 and 0.6, respectively; p < 0.00001). Conversely, the levels of cf-mtDNA in BD and DDs do not differ compared with healthy individuals. Nevertheless, further research is needed in the case of BD and DDs due to the small sample sizes in the BD studies and the significant data heterogeneity in the DD studies. Additionally, further studies are needed on cf-mtDNA in schizophrenia or cf-gDNA and total cfDNA in BD and DDs due to insufficient data. In conclusion, this meta-analysis provides the first evidence of increases in total cfDNA and cf-gDNA in schizophrenia but shows no changes in cf-mtDNA in BD and DDs. Increased circulating cfDNA in schizophrenia may be associated with chronic systemic inflammation, as cfDNA has been found to trigger inflammatory responses.

Kynurenine pathway abnormalities are state-specific but not diagnosis-specific in schizophrenia and bipolar disorder

Schizophrenia (SCZ) and bipolar disorder (BD) are associated with immunological dysfunctions that have been hypothesized to lead to clinical symptomatology in particular through kynurenine pathway abnormalities. The aim of this study was thus to investigate the impact of serum kynurenine metabolite levels on diagnosis, clinical state, symptom severity and clinical course in a large French transdiagnostic cohort of SCZ and BD patients. Four patient groups (total n = 507) were included in a cross-sectional observational study: 1) hospitalized acute bipolar patients (n = 205); 2) stable bipolar outpatients (n = 116); 3) hospitalized acute schizophrenia patients (n = 111) and 4) stable schizophrenia outpatients (n = 75), in addition to healthy controls (HC) (n = 185). The quantitative determination of serum kynurenine metabolites was performed using liquid chromatography-tandem mass spectrometry. Kynurenine levels were lower in all patients combined compared to HC while ANCOVA analyses did not reveal inter-diagnostic difference between SCZ and BD. Interestingly, hospitalized patients of both diagnostic groups combined displayed significantly lower kynurenine levels than stabilized outpatients. Psychotic symptoms were associated with lower quinaldic acid (F = 9.18, p=<.001), which is KAT-driven, whereas a longer duration of illness contributed to abnormalities in tryptophan (F = 5.41, p = .023), kynurenine (F = 16.93, p=<.001), xanthurenic acid (F = 9.34, p = .002), quinolinic acid (F = 9.18, p = .003) and picolinic acid (F = 4.15, p = .043), metabolized through the KMO-branch. These data confirm illness state rather than diagnosis to drive KP alterations in SCZ and BD. Lower levels of KP metabolites can thus be viewed as a transdiagnostic feature of SCZ and BD, independently associated with acute symptomatology and a longer duration of illness. Quinaldic acid has seldomly been investigated by previous studies and appears an important state marker in SCZ and BD. As serum samples are used in this study, it is not possible to extrapolate these findings to the brain.

GluN1 antibody causes behavioral deficits in prepulse inhibition and memory through CaMKIIβ signaling

Accumulating evidence suggests that some patients with schizophrenia have high production of autoantibodies against the N-methyl-d-aspartate receptor (NMDAR) subunit GluN1 and that these antibodies lead to cognitive impairment. However, the molecular mechanisms of the deficits seen in these patients are largely unknown. In the present study, we found that passive infusion of GluN1 antibody into the hippocampus of mice for 7 days led to decreased expression of GluN1, phosphor-Ser897-GluN1, and EphrinB2 receptor (EphB2R); deficits in long-term potentiation (LTP) and synaptic transmission in the hippocampal CA1 area; impairment in prepulse inhibition (PPI); and deterioration of recognition memory in novel object recognition test. We also found decreased expression of CaMKIIβ, ERK1/2, CREB, and NF-κB after 7 days of GluN1 antibody exposure, as was the phosphorylation of these signaling molecules. The decrease in GluN1 and phosphor-Ser897-GluN1 expression and the deficits in LTP, PPI, and recognition memory were ameliorated by CaMKIIβ overexpression. These results suggest that downregulation of CaMKIIβ-ERK1/2-CREB-NF-κB signaling is responsiable for GluN1 antibody-associated impairment in PPI and memory and that GluN1 antibody-induced NMDAR hypofunction is the underlying mechanism of this impairment. Our findings indicate possible strategies to ameliorate NMDAR antibody-associated cognitive impairment in neuropsychiatric disease. They also provide evidence that NMDAR hypofunction is an underlying mechanism for cognitive impairment in schizophrenia.

Gut microbiota alterations in stable outpatients with schizophrenia: findings from a case-control study

OBJECTIVE

The pathogenesis of schizophrenia is multidimensional and intensively studied. The gut-brain axis disturbances might play a significant role in the development of schizophrenia.

METHODS

We compared the gut microbiota of 53 individuals with schizophrenia and 58 healthy controls, using the 16S rRNA sequencing method. Individuals with schizophrenia were assessed using the following scales: the Positive and Negative Syndrome Scale, the Calgary Depression Scale for Schizophrenia, the Social and Occupational Functioning Assessment Scale and the Repeatable Battery for the Assessment of Neuropsychological Status.

RESULTS

No significant between-group differences in α-diversity measures were observed. Increased abundance of Lactobacillales (order level), Bacilli (class level) and Actinobacteriota (phylum level) were found in individuals with schizophrenia regardless of potential confounding factors, and using two independent analytical approaches (the distance-based redundancy analysis and the generalised linear model analysis). Additionally, significant correlations between various bacterial taxa (the Bacteroidia class, the Actinobacteriota phylum, the Bacteroidota phylum, the Coriobacteriales order and the Coriobacteria class) and clinical manifestation (the severity of negative symptoms, performance of language abilities, social and occupational functioning) were observed.

CONCLUSIONS

The present study indicates that gut microbiota alterations are present in European patients with schizophrenia. The abundance of certain bacterial taxa might be associated with the severity of negative symptoms, cognitive performance and general functioning. Nonetheless, additional studies are needed before the translation of our results into clinical practice.

Profiling antibody signature of schizophrenia by Escherichia coli proteome microarrays

Schizophrenia (SZ) is influenced by genetic and environmental factors, and associated with chronic neuroinflammation. If the symptoms express after adolescence, environmental impacts are more substantial, and the disease is defined as adult-onset schizophrenia (AOS). Effects of environmental factors on antibody responses such as Escherichia coli (E. coli) to immunoglobulin G (IgG) and immunoglobulin M (IgM) might increase the severity of symptoms in SZ via the gut-brain axis. The purpose of this study is to reveal antibody profiles of SZ against bacterial protein antigens. We analyzed the IgG and IgM antibodies using E. coli proteome microarrays from 80 SZ patients and 40 healthy controls (HC). Using support vector machine to select panels of proteins differentiating between groups and conducted enrichment analysis for those proteins. We identified that the groL, pldA, yjjU, livG, and ftsE can classify IgGs in AOS vs HC achieved accuracy of 0.7. The protein yjjU, livG and ftsE can form the best combination panel to classify IgG in AOS vs HC with accuracy of 0.8. The enrichment results are highly related to ABC (ATP binding cassette) transporter in the protein domain and cellular component. We further found that the human ATP binding cassette subfamily b member 1 (ABCB1) autoantibody level in AOS is significantly higher than in HC. The findings suggest that AOS had different immunoglobulin production compared to early-onset schizophrenia (EOS) and HC. We also identified potential antibody biomarkers of AOS and found their antigens are enriched in ABC transporter related domains, including human ABCB1 protein.

Immunologic profiling in schizophrenia and rheumatoid arthritis

The negative relationship between schizophrenia (SCZ) and rheumatoid arthritis (RA) has been observed for 85 years, but the mechanisms driving this association are unknown. This study analyzed differences in profiles of cytokines (IL-1β, IL-Ra, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p70, IFNγ, TNFα), selected genes (HLA-DRB1, IL1RN, HP2), and antibodies related to gluten sensitivity (AGA-IgG, AGA-IgA), celiac disease (tTG), and systemic autoimmunity (ANA, anti-CCP, RF) in 40 subjects with SCZ, 40 with RA, and 40 healthy controls (HC). HLA-DRB1*04:01 alleles were enriched in persons with SCZ and RA compared with HC, and the HP2/HP2 genotype was 2-fold more prevalent in AGA/tTG-positive versus negative SCZ patients. Patients with SCZ demonstrated 52.5% positivity for any of the antibodies tested, compared to 90% of RA patients and 30% of HC. Cluster analysis of the cytokines revealed three clusters: one associated with SCZ marked by high levels of IL-1Ra, one associated with HC, and one associated with both SCZ and RA marked by elevated levels of IFNγ, TNFα, and IL-6. These analyses suggest that stratification of SCZ patients by cytokine profile may identify unique SCZ subgroups and enable the use of currently available cytokine-targeted treatment strategies.

Limited association between infections, autoimmune disease and genetic risk and immune activation in severe mental disorders

BACKGROUND

Low-grade inflammation may be part of the underlying mechanism of schizophrenia and bipolar disorder. We investigated if genetic susceptibility, infections or autoimmunity could explain the immune activation.

METHODS

Seven immune markers were selected based on indicated associations to severe mental disorders (IL-1Ra, sIL-2R, IL-18, sgp130, sTNFR-1, APRIL, ICAM-1) and measured in plasma of patients with schizophrenia (SCZ, N = 732) and bipolar spectrum disorders (BD, N = 460) and healthy controls (HC, N = 938). Information on rate of infections and autoimmune diseases were obtained from Norwegian national health registries for a twelve-year period. Polygenic risk scores (PRS) of SCZ and BD were calculated from genome-wide association studies. Analysis of covariance were used to test effects of infection rate, autoimmune disease and PRS on differences in immune markers between patients and HC.

RESULTS

Infection rate differed between all groups (BD > HC > SCZ, all p < 0.001) whereas autoimmune disease was more frequent in BD compared to SCZ (p = 0.004) and HC (p = 0.003). sIL-2R was positively associated with autoimmune disease (p = 0.001) and negatively associated with PRS of SCZ (p = 0.006) across SCZ and HC; however, associations represented only small changes in the difference of sIL-2R levels between SCZ and HC.

CONCLUSION

There were few significant associations between rate of infections, autoimmune disease or PRS and altered immune markers in SCZ and BD, and the detected associations represented only small changes in the immune aberrations. The findings suggest that most of the low-grade inflammation in SCZ and BD is explained by other factors than the underlying PRS, autoimmunity and infection rates.

Antibodies against N-Methyl D-Aspartate Receptor in Psychotic Disorders: A Systematic Review

OBJECTIVE

The objective of this study was to provide comprehensive evidence synthesis including all available up-to-date data about the prevalence of N-methyl D-aspartate receptor (NMDAR) antibodies (ABs) in psychotic patients in order to evaluate the clinical relevance of ABs as well as to specify potential explanations of the heterogeneity of the findings and determine areas for further research.

METHODS

A literature search was conducted using the PubMed/Medline, Web of Knowledge, and Scopus databases.

RESULTS

Forty-seven studies and 4 systematic reviews (including 2 meta-analyses) were included in the present review. Studies that used cell-based assays (CBAs) provided heterogeneous results on AB prevalence, obviously depending on the type of detection assay and sample characteristics. Improvement of AB detection methods is necessary to determine the real prevalence of ABs across different groups of patients and healthy people. Live CBAs seem to have better sensitivity but probably poorer specificity than fixed CBAs. Moreover, some links between AB-positive status and acute symptoms are possible. A small amount of data on immunotherapy in AB-positive patients raises the possibility of its effectiveness but obviously require further research.

CONCLUSIONS

NMDAR ABs are definitely present in a subset of psychotic patients. NMDAR ABs might shape psychosis and underlie some symptoms, and immunotherapy might be regarded as a treatment option for patients failing to respond to other therapies.

Skewing of the Antibody Repertoire in Cerebrospinal Fluid B Cells from Healthy Controls and Patients with Schizophrenia

Autoantibodies play a role in the etiology of some neuropsychiatric disorders. To address the possibility that B cells and their antibodies may be involved in the pathophysiology of schizophrenia, we examined B cells in cerebrospinal fluid (CSF) and peripheral blood (PB) of 4 schizophrenic patients (SP) and 4 healthy control (HC) volunteers by analyzing immunoglobulin VH gene usage. All CSF samples contained measurable levels of B cells. We found for both SP and HC, CSF B cells represented a select subset of, and were not the same as, B cells in PB. Moreover, we found statistically significant differences in antibodies generated by CSF B cells in SP compared to CSF B cells in HC. Although binding characteristics of CSF SP-associated B cell antibodies is unknown, the study number is small, and pathophysiology has not been established, these results suggest the value of focusing further study on the distinctly separate population of CSF B cells in SP.

Immune System Abnormalities in Schizophrenia: An Integrative View and Translational Perspectives

The immune system is generally known to be the primary defense mechanism against pathogens. Any pathological conditions are reflected in anomalies in the immune system parameters. Increasing evidence suggests the involvement of immune dysregulation and neuroinflammation in the pathogenesis of schizophrenia. In this systematic review, we summarized the available evidence of abnormalities in the immune system in schizophrenia. We analyzed impairments in all immune system components and assessed the level of bias in the available evidence. It has been shown that schizophrenia is associated with abnormalities in all immune system components: from innate to adaptive immunity and from humoral to cellular immunity. Abnormalities in the immune organs have also been observed in schizophrenia. Evidence of increased C-reactive protein, dysregulation of cytokines and chemokines, elevated levels of neutrophils and autoantibodies, and microbiota dysregulation in schizophrenia have the lowest risk of bias. Peripheral immune abnormalities contribute to neuroinflammation, which is associated with cognitive and neuroanatomical alterations and contributes to the pathogenesis of schizophrenia. However, signs of severe inflammation are observed in only about 1/3 of patients with schizophrenia. Immunological parameters may help identify subgroups of individuals with signs of inflammation who well respond to anti-inflammatory therapy. Our integrative approach also identified gaps in knowledge about immune abnormalities in schizophrenia, and new horizons for the research are proposed.

Anti-Neuronal Autoantibodies (Cell Surface and Onconeural) and Their Association With Natural Autoantibodies in Synthetic Cannabinoid-Induced Psychosis

Patients suffering from encephalitis may present psychiatric symptoms; however, the clinical relevance of anti-neuronal antibodies in patients experiencing a psychotic episode without encephalitis is still unclear. In this study, we examined the presence of anti-neuronal cell surface autoantibodies and onconeural autoantibodies in serum samples of 22 synthetic cannabinoid users presenting with psychosis. We found only two positive cases; however, seven patients had borderline results. Nonetheless, we found no significant correlation between anti-neuronal autoantibodies and the intensity of psychosis indicated by the Positive and Negative Syndrome Scale (PANSS) scores. The length of drug use and the combination of other drugs with synthetic cannabinoids have no significant effect on anti-neuronal autoantibody positivity. Nonetheless, the ratio of anti-citrate synthase (anti-CS) IgM and IgG natural autoantibodies was significantly lower (p = 0.036) in the anti-neuronal autoantibody-positive/borderline samples, than in the negative group. Interestingly, anti-CS IgM/IgG showed a significant negative correlation with PANSS-positive score (p = 0.04, r = -0.464). Our results demonstrated that anti-neuronal autoantibody positivity occurs in synthetic cannabinoid users, and the alteration of anti-CS IgM/IgG natural autoantibody levels points to immunological dysfunctions in these cases.

Brick by Brick: Building a Transdiagnostic Understanding of Inflammation in Psychiatry

ABSTRACT

Inflammatory phenomena are found in many psychiatric disorders-notably, depression, schizophrenia, and posttraumatic stress disorder. Inflammation has been linked to severity and treatment resistance, and may both contribute to, and result from, the pathophysiology of some psychiatric illnesses. Emerging research suggests that inflammation may contribute to symptom domains of reward, motor processing, and threat reactivity across different psychiatric diagnoses. Reward-processing deficits contribute to motivational impairments in depression and schizophrenia, and motor-processing deficits contribute to psychomotor slowing in both depression and schizophrenia. A number of experimental models and clinical trials suggest that inflammation produces deficits in reward and motor processing through common pathways connecting the cortex and the striatum, which includes the nucleus accumbens, caudate nucleus, and putamen.The observed effects of inflammation on psychiatric disorders may cut across traditional conceptualizations of psychiatric diagnoses. Further study may lead to targeted immunomodulating treatments that address difficult-to-treat symptoms in a number of psychiatric disorders. In this review, we use a Research Domain Criteria framework to discuss proposed mechanisms for inflammation and its effects on the domains of reward processing, psychomotor slowing, and threat reactivity. We also discuss data that support contributing roles of metabolic dysregulation and sex differences on the behavioral outcomes of inflammation. Finally, we discuss ways that future studies can help disentangle this complex topic to yield fruitful results that will help advance the field of psychoneuroimmunology.

Prevalence of Anti-Nuclear Antibodies and Anti-Phospholipid Antibodies in an Egyptian Cohort with Schizophrenia: A Case-Control Study

BACKGROUND

Psychiatric disorders, including schizophrenia could herald other manifestation(s) of systemic lupus erythematosus (SLE) potentially hindering timely and optimal management. Moreover, schizophrenia is among the described 'extra-criteria' manifestations of anti-phospholipid syndrome (APS). Hence, screening schizophrenia patients for SLE and APS may pose diagnostic and therapeutic implications.

OBJECTIVES

Examine schizophrenia patients with no overt connective tissue disease(s) manifestation(s) for clinical and/or serologic evidence of SLE and/or APS.

METHODS

The study included 92 schizophrenia patients [61 (66.3%) males] and 100 age- and gender-matched healthy controls. Both groups were tested for anti-nuclear antibodies (ANAs), anti-double stranded deoxyribonucleic acid (anti-dsDNA) antibodies, complement 3 (C3) and C4, and criteria anti-phospholipid antibodies (aPL) [anticardiolipin Immunoglobulin (Ig) G and IgM, anti-beta-2-glycoprotein I IgG and IgM, and lupus anticoagulant (LAC)].

RESULTS

The patients' mean age and disease duration were 28.8 ± 8.1 and 5.7 ± 2.2 years, respectively. The prevalence of ANA positivity, height of titre, and pattern was comparable between patients and controls (p = 0.9, p = 0.8 and p = 0.1, respectively). Anti-dsDNA antibodies and hypocomplementemia were absent in both groups. A significantly higher frequency of positive LAC was observed among patients compared with controls (7.6 % vs. 1 %, p = 0.02), whereas other aPL were comparable between both groups. None of the patients or controls demonstrated clinically meaningful (medium or high) aPL titres.

CONCLUSION

In our study, schizophrenia was solely associated with LAC. Thus, in the absence of findings suggestive of SLE or APS, routine screening for both diseases is questionable.

Peripheral Blood-Based Gene Expression Studies in Schizophrenia: A Systematic Review

Schizophrenia is a disorder that is characterized by delusions, hallucinations, disorganized speech or behavior, and socio-occupational impairment. The duration of observation and variability in symptoms can make the accurate diagnosis difficult. Identification of biomarkers for schizophrenia (SCZ) can help in early diagnosis, ascertaining the diagnosis, and development of effective treatment strategies. Here we review peripheral blood-based gene expression studies for identification of gene expression biomarkers for SCZ. A literature search was carried out in PubMed and Web of Science databases for blood-based gene expression studies in SCZ. A list of differentially expressed genes (DEGs) was compiled and analyzed for overlap with genetic markers, differences based on drug status of the participants, functional enrichment, and for effect of antipsychotics. This literature survey identified 61 gene expression studies. Seventeen out of these studies were based on expression microarrays. A comparative analysis of the DEGs (n = 227) from microarray studies revealed differences between drug-naive and drug-treated SCZ participants. We found that of the 227 DEGs, 11 genes (ACOT7, AGO2, DISC1, LDB1, RUNX3, SIGIRR, SLC18A1, NRG1, CHRNB2, PRKAB2, and ZNF74) also showed genetic and epigenetic changes associated with SCZ. Functional enrichment analysis of the DEGs revealed dysregulation of proline and 4-hydroxyproline metabolism. Also, arginine and proline metabolism was the most functionally enriched pathway for SCZ in our analysis. Follow-up studies identified effect of antipsychotic treatment on peripheral blood gene expression. Of the 27 genes compiled from the follow-up studies AKT1, DISC1, HP, and EIF2D had no effect on their expression status as a result of antipsychotic treatment. Despite the differences in the nature of the study, ethnicity of the population, and the gene expression analysis method used, we identified several coherent observations. An overlap, though limited, of genetic, epigenetic and gene expression changes supports interplay of genetic and environmental factors in SCZ. The studies validate the use of blood as a surrogate tissue for biomarker analysis. We conclude that well-designed cohort studies across diverse populations, use of high-throughput sequencing technology, and use of artificial intelligence (AI) based computational analysis will significantly improve our understanding and diagnostic capabilities for this complex disorder.

Systemic lupus erythematosus and autoimmune features in chronic hospitalized patients with schizophrenia

OBJECTIVES

Recent studies highlighted the link of schizophrenia risk with genetic variations in complement, which share the same pathogenesis with systemic lupus erythematosus (SLE). However, the coexistence of SLE and schizophrenia were rarely reported. We aimed to explore the autoantibody profiles, complement levels and prevalence of SLE in chronic schizophrenia patients.

METHODS

A prospective, cross-sectional study was conducted to recruit 481 long-term hospitalized schizophrenia spectrum disorder patients in Yuli hospital, Taiwan. Severity of schizophrenia was assessed by Positive and Negative Syndrome Scale (PANSS). Immunologic tests of autoantibodies and complement levels were measured. Genome-wide association analysis was conducted to compare genetic variants between schizophrenia with SLE and non-SLE schizophrenia.

RESULTS

In total, 47 (9.8%) and 31 (6.4%) participants had positive anti-nuclear antibody (ANA) and anti-double stranded DNA (anti-dsDNA) antibodies, respectively. After rheumatologic exams, 30 (6.2%) patients were diagnosed schizophrenia with SLE, while 32 (6.7%) subjects were classified as schizophrenia with autoimmune features. Schizophrenia patients with SLE had more arthritis, serositis, homogenous ANA pattern, conceptual disorganization in PANSS and increased salivation due to psychotropics compared with their counterparts. ANA titers and complement levels were significantly correlated with PANSS scores and side effect of psychotropics. No significant genetic variation between schizophrenia with SLE and non-SLE schizophrenia were identified.

CONCLUSION

SLE may coexist in chronic hospitalized schizophrenia. Complement levels could be a potential biomarker in schizophrenia patients. Considering the possible reversibility of psychotic features and adverse effects of antipsychotics, SLE with psychosis should be identified in patients with chronic hospitalized schizophrenia.

Pharmacotherapy of schizophrenia: immunological aspects and potential role of immunotherapy

INTRODUCTION

Schizophrenia is a complex disorder owing to diversity in clinical phenotypes, overlapping symptoms, and heterogeneous clinical presentation. Even after decades of research, the exact causative mechanisms of schizophrenia are not completely known. Recent evidence indicates the role of immune dysfunction in schizophrenia pathogenesis as observed from alteration in immune cells, increased activity of complement cascade, and development of autoantibodies against neurotransmitter receptors. Immunotherapy involving immunosuppressants and cytokine-targeting drugs, have shown promising results in several clinical studies and it demands further research in this area.

AREAS COVERED

Here, the authors review the immunopathogenesis of schizophrenia, limitations of conventional, and atypical antipsychotic drugs and the potential role and limitations of immunotherapeutic drugs in schizophrenia management.

EXPERT OPINION

Schizophrenia is a complex disorder and poses a challenge to the currently available treatment approaches. Nearly 30% schizophrenia patients exhibit minimal response toward conventional and atypical antipsychotic drugs. Immune system dysfunction plays an important part of schizophrenia pathophysiology and existing monoclonal antibody (mAb) drugs targeting specific components of the immune system are being repositioned in schizophrenia. The authors call upon public and private funders to facilitate urgent and rigorous research efforts in exploring potential role of immunotherapy in schizophrenia.

Autoantibody profiles associated with clinical features in psychotic disorders

Autoimmune processes are suspected to play a role in the pathophysiology of psychotic disorders. Better understanding of the associations between auto-immunoglobulin G (IgG) repertoires and clinical features of mental illness could yield novel models of the pathophysiology of psychosis, and markers for biological patient stratification. We undertook cross-sectional detection and quantification of auto-IgGs in peripheral blood plasma of 461 people (39% females) with established psychotic disorder diagnoses. Broad screening of 24 individuals was carried out on group level in eight clinically defined groups using planar protein microarrays containing 42,100 human antigens representing 18,914 proteins. Autoantibodies indicated by broad screening and in the previous literature were measured using a 380-plex bead-based array for autoantibody profiling of all 461 individuals. Associations between autoantibody profiles and dichotomized clinical characteristics were assessed using a stepwise selection procedure. Broad screening and follow-up targeted analyses revealed highly individual autoantibody profiles. Females, and people with family histories of obesity or of psychiatric disorders other than schizophrenia had the highest overall autoantibody counts. People who had experienced subjective thought disorder and/or were treated with clozapine (trend) had the lowest overall counts. Furthermore, six autoantibodies were associated with specific psychopathology symptoms: anti-AP3B2 (persecutory delusions), anti-TDO2 (hallucinations), anti-CRYGN (initial insomnia); anti-APMAP (poor appetite), anti-OLFM1 (above-median cognitive function), and anti-WHAMMP3 (anhedonia and dysphoria). Future studies should clarify whether there are causal biological relationships, and whether autoantibodies could be used as clinical markers to inform diagnostic patient stratification and choice of treatment.

Challenges in Prescribing Clozapine in the Era of COVID-19: A Review Focused on Immunological Implications

The global COVID-19 pandemic has disrupted every aspect of the healthcare system. Apart from the issues surrounding COVID-19 itself, care for existing patients has met many challenges. One such challenge is caring for patients who are on clozapine treatment and have been confirmed positive for COVID-19. Schizophrenia has been considered to have a deep connection with the immune system, and clozapine can induce further changes in this system. COVID-19 can ravage the compromised immune system and aggravate tissue damage. The intricate relations between schizophrenia, clozapine, and COVID-19 make it difficult to predict the clinical course of COVID-19 in clozapine-treated patients. However, the rigid prohibition on using clozapine if COVID-19 is confirmed may harm patients. Patients who have to use clozapine are often refractory cases with no alternatives. Therefore, the decision to maintain or stop clozapine must be made after a comprehensive review of the patient’s unique situation. To do this, theoretical and practical issues surrounding the use of clozapine in COVID-19 should be reviewed and discussed. In this review, we gather useful information surrounding this issue and present an overview. Focusing on the immune system, various theoretical possibilities that could arise from schizophrenia, clozapine, and COVID-19 were carefully examined, and practical checklists for the care of these patients were explored. It is hoped that this review will convince many clinicians to pay attention to this momentous issue and facilitate more active sharing of clinical experiences.

Novel approaches in schizophrenia-from risk factors and hypotheses to novel drug targets

Schizophrenia is a severe psychiatric disorder characterized by emotional, behavioral and cognitive disturbances, and the treatment of schizophrenia is often complicated by noncompliance and pharmacoresistance. The search for the pathophysiological mechanisms underlying schizophrenia has resulted in the proposal of several hypotheses to explain the impacts of environmental, genetic, neurodevelopmental, immune and inflammatory factors on disease onset and progression. This review discusses the newest insights into the pathophysiology of and risk factors for schizophrenia and notes novel approaches in antipsychotic treatment and potential diagnostic and theranostic biomarkers. The current hypotheses focusing on neuromediators (dopamine, glutamate, and serotonin), neuroinflammation, the cannabinoid hypothesis, the gut-brain axis model, and oxidative stress are summarized. Key genetic features, including small nucleotide polymorphisms, copy number variations, microdeletions, mutations and epigenetic changes, are highlighted. Current pharmacotherapy of schizophrenia relies mostly on dopaminergic and serotonergic antagonists/partial agonists, but new findings in the pathophysiology of schizophrenia have allowed the expansion of novel approaches in pharmacotherapy and the establishment of more reliable biomarkers. Substances with promising results in preclinical and clinical studies include lumateperone, pimavanserin, xanomeline, roluperidone, agonists of trace amine-associated receptor 1, inhibitors of glycine transporters, AMPA allosteric modulators, mGLUR_2-3 agonists, D-amino acid oxidase inhibitors and cannabidiol. The use of anti-inflammatory agents as an add-on therapy is mentioned.

Immune-inflammatory markers and psychosis risk: A systematic review and meta-analysis

Subclinical inflammation has been associated with psychosis; however, it remains unknown whether this phenomenon appears also in the premorbid phase. Therefore, we performed a systematic review and meta-analysis of studies comparing peripheral blood levels of C-reactive protein (CRP) and cytokines between individuals at risk of psychosis and controls. Moreover, we tested the hypothesis that the levels of these markers may be different in high-risk converters versus non-converters. Two independent reviewers searched electronic databases until Dec 16th, 2020. After reviewing publication records, 16 studies (548 high-risk individuals and 559 controls) were included. Random-effects meta-analyses with Hedges' g as the effect size estimate were performed. Individuals at clinical risk of psychosis had significantly higher levels of interleukin-6 (IL-6) compared to controls (g = 0.33, 95%CI: 0.06-0.60, p = 0.018). Heterogeneity was not significant in this subgroup analysis. Changes in the levels of IL-6 in subjects at familial risk of psychosis were not significant (g = 0.04, 95%CI: -0.24 to 0.31, p = 0.798). The use of antidepressants was associated with significantly higher levels of IL-6 in high-risk individuals (Beta = 1.56, 95%CI: 0.60-2.53, p = 0.001). No significant differences in the levels of immune-inflammatory markers were found between high-risk converters and non-converters. Our findings suggest that individuals at clinical risk of psychosis show subclinical inflammation in terms of elevated IL-6 levels. This phenomenon might be related to the use of antidepressants. The present meta-analysis does not support the usefulness of single immune-inflammatory markers in predicting transition to psychosis.

Evaluating the Hypothesis That Schizophrenia Is an Inflammatory Disorder

The investigation of immune system abnormalities in schizophrenia, although ongoing for decades, has become a popular area of research. The authors present a selected review of studies informing on schizophrenia as a potential inflammatory disorder, emphasizing replicated findings. The authors summarize evidence for inflammation over the illness course, discuss relationships between inflammation and psychopathology, present studies of imaging of neuroinflammation, consider inflammation as a marker of treatment response and treatment target, and review potential mechanisms for the effects of inflammation on the brain in schizophrenia. Although there is not clear and convincing evidence to support the assertion that schizophrenia is an inflammatory disorder, this area of study shows promise toward a greater understanding of the etiopathophysiology of this heterogeneous disorder.

Meta-analysis of total and differential white blood cell counts in schizophrenia

OBJECTIVE

Schizophrenia is associated with alterations in blood inflammatory markers, including cytokines. Total white blood cell (WBC) count is a marker of low-grade inflammation. We conducted a meta-analysis of total and differential WBC counts in patients with schizophrenia.

METHOD

Articles were identified through a systematic search of PsycINFO, Pub Med, Web of Science, and the associated references. Data were analyzed using a random effects approach.

RESULTS

Twenty-four studies met the inclusion criteria. Blood total WBC, monocytes, and neutrophils were significantly higher in schizophrenia vs. controls with small-to-medium effect sizes (standardized mean difference [SMD] = 0.39-0.53, P < 0.01 for each). In first-episode psychosis compared with controls, neutrophils and monocytes were significantly increased with similar effect sizes (SMD = 0.40-0.41, P ≤ 0.01 for each), and there was a trend for higher total WBC (SMD = 0.46, P = 0.05).

CONCLUSIONS

Consistent with studies of other inflammatory markers, we found evidence for increased total and differential WBC counts in schizophrenia. Our results complement other studies of WBC counts in schizophrenia. These findings are relevant to the pathophysiology and potentially the treatment of schizophrenia.

[Mental disorders and cognitive impairment in patients with antiphospholipid syndrome]

Mental disorders (mainly anxiety and depressive disorders) and cognitive impairment are often found in patients with antiphospholipid syndrome (APS), but their prevalence, structure, and mechanisms of occurrence are not well researched. The review provides literature data on the frequency, spectrum and possible causes of mental disorders and cognitive impairment in patients with APS, the pathogenetic mechanisms of these disorders (in particular, the important role of antiphospholipid antibodies, stress factors, chronic inflammation), the relationship between APS, mental disorders and as well as cognitive impairment is examined. Special attention is paid to the influence of mental disorders and cognitive impairment on patients adherence to treatment, their quality of life, as well as the particularities of psychopharmacotherapy of mental disorders in patients with APS. The aim of the review is to actualize the interdisciplinary problem of mental disorders and cognitive impairment in patients with APS and the need to introduce a partnership model of care.

Autoimmune encephalitis with psychosis: Warning signs, step-by-step diagnostics and treatment

Objectives: Despite intensive research, schizophrenia and schizoaffective disorders continue to be theoretical constructs that describe clinical syndromes and no pathophysiologically defined diseases. Moreover, there are no clear biomarkers at hand. Therefore, these diagnoses are still set up based on clinical ICD-10/DSM-5 criteria and the exclusion of alcohol-/drug-associated, systemic or other brain organic causes.Methods: Recently, autoimmune encephalitis with psychotic symptoms caused by specific antineuronal antibodies has been identified as a rare, but potentially treatable differential diagnosis. However, these inflammatory brain diseases are not reliably detected by our current routine diagnostic workup in psychiatry. This qualitative review provides structured diagnostic and therapeutic support for clinical practice.Results: Disturbances of consciousness and orientation, catatonia, speech dysfunction, focal neurological signs, epileptic seizures/EEG abnormalities or autonomic dysfunction are warning signs in psychiatric patients which should always induce cerebrospinal fluid analysis with determination of antineuronal autoantibodies. Currently established immunotherapy strategies are summarised, taking into account international expert advice.Conclusions: Guided by clinical warning signs, our qualitative review enables rapid and reliable diagnosis of definite autoimmune encephalitis. This is of high relevance for the affected individuals, since early and sufficiently intense immunotherapy often leads to a good prognosis despite severe illness.

Biomarkers of Autoimmunity in Acute Psychiatric Disorders

OBJECTIVE

Previous studies have suggested that autoantibodies associated with systemic autoimmune disorders are more prevalent in patients with psychotic and affective disorders compared with healthy control subjects. However, most positive studies addressing this issue have been limited by small sample sizes and lack of correction for confounding factors. The authors aimed to assess the prevalence of several autoantibodies in patients admitted to acute psychiatric inpatient care and investigate whether patients with psychotic and affective disorders have an increased prevalence of autoantibodies compared with psychiatric patients admitted for other reasons.

METHODS

Five hundred eighty-five patients were screened for the presence of antinuclear antibodies (ANA), anticardiolipin and antibeta2-glycoprotein, antithyroid peroxidase (anti-TPO), antitissue transglutaminase IgA, antigliadin deamidated peptide IgG, and rheumatoid factor IgM (RF). Differences in prevalence between patients with nonaffective psychoses (N=105), bipolar disorders (N=78), unipolar depressive disorders (N=146), and other reasons for admission (N=256) were assessed using chi-square tests and logistic regression models.

RESULTS

One or more autoantibodies were present in 26.2% of the patients, including ANA (9.4%), RF (9.2%), and anti-TPO (5.6%). Autoantibody prevalence increased with age (odds ratio=1.21, 95% CI=1.09-1.35) and smoking status (odds ratio=1.99, 95% CI=1.04-3.82) but was not associated with a diagnosis of a psychotic or affective disorder.

CONCLUSIONS

Autoimmune autoantibodies seem to be equally prevalent in patients with acute psychiatric conditions with and without psychotic and affective disorders. This result challenges the idea that these autoantibodies have specificity for certain psychiatric disorders.

Autoimmune psychosis: an international consensus on an approach to the diagnosis and management of psychosis of suspected autoimmune origin

There is increasing recognition in the neurological and psychiatric literature of patients with so-called isolated psychotic presentations (ie, with no, or minimal, neurological features) who have tested positive for neuronal autoantibodies (principally N-methyl-D-aspartate receptor antibodies) and who have responded to immunotherapies. Although these individuals are sometimes described as having atypical, mild, or attenuated forms of autoimmune encephalitis, some authors feel that that these cases are sufficiently different from typical autoimmune encephalitis to establish a new category of so-called autoimmune psychosis. We briefly review the background, discuss the existing evidence for a form of autoimmune psychosis, and propose a novel, conservative approach to the recognition of possible, probable, and definite autoimmune psychoses for use in psychiatric practice. We also outline the investigations required and the appropriate therapeutic approaches, both psychiatric and immunological, for probable and definite cases of autoimmune psychoses, and discuss the ethical issues posed by this challenging diagnostic category.

Clinically Relevant Anti-Neuronal Cell Surface Antibodies in Schizophrenia Spectrum Disorders

Schizophrenia is a phenotypically heterogeneous and poorly understood disorder. While its etiology is likely multifactorial, immune system dysfunction has increasingly been implicated in its development. As hallucinations and delusions occur frequently and prominently in autoimmune encephalitis (AE), numerous studies have sought to determine whether a small subset of individuals diagnosed with schizophrenia possess anti-neuronal antibodies implicated in AE. Exploring this possibility is of clinical relevance, as identifying individuals with AE who have been misdiagnosed as having a primary psychotic disorder may allow for the implementation of appropriate immune-related therapies as early as possible in the course of the illness, in order to optimize outcomes, reduce illness chronicity, and minimize adverse events. This qualitative review serves to provide an overview of the existing literature on this topic, as well as to update previously published reviews. Although there is some evidence to suggest that in rare cases AE may be misdiagnosed as a primary psychotic disorder, particularly early in the course of the illness, numerous methodological differences between studies likely account for the highly variable findings, and interpretation of the results is particularly limited by a paucity of cerebrospinal fluid data. Moreover, the prevalence of misdiagnosis in chronic and treatment-resistant populations remains understudied. This is particularly problematic, as treatment resistance may represent an enriched population with respect to the presence of anti-neuronal antibodies, and given that such patients have few evidence-based treatment options available to them beyond clozapine.

Rates of hepatitis B and C in patients with schizophrenia: A meta-analysis

OBJECTIVE

Schizophrenia is associated with increased infectious disease comorbidity and mortality. Individuals with schizophrenia have increased risk of infectious hepatitis, potentially due to substance use comorbidity, sexual behaviors, and immunologic factors. We performed a systematic review and meta-analysis of the association between schizophrenia and hepatitis B and C.

METHOD

We searched major electronic databases from inception until January 2019 for prevalence and case-control studies of infectious hepatitis in patients with schizophrenia. Random effects meta-analyses calculating odds ratios (ORs) and 95% confidence intervals (CIs) for case-controls studies, prevalence and 95% CIs, and meta-regression analyses were performed.

RESULTS

Twenty-one studies met the inclusion criteria. In case-control studies, there was an over 3-fold increased odds of hepatitis C in patients with schizophrenia (OR = 3.29, 95% CI 1.50-7.23, p = 0.003), and a prevalence of 6% (ES = 0.06, 95% CI 0.04-0.08). In case-control studies, there was an over 2-fold increased odds of hepatitis B in patients with schizophrenia (OR = 2.36, 95% CI 1.61-3.47, p < 0.001) and a prevalence of 7% (ES = 0.07, 95% CI 0.03-0.11).

CONCLUSION

We found an approximately 3-fold increased odds of hepatitis B and C in patients with schizophrenia. This association may be due to an increased prevalence of environmental risk factors, increased susceptibility to infections, or both. Findings suggest that screening for infectious hepatitis may be germane to the clinical care of patients with schizophrenia and relevant risk factors.

Th17 and MAIT cell mediated inflammation in antipsychotic free schizophrenia patients

The immune hypothesis of schizophrenia has gained significant popularity in recent years in schizophrenia research. Evidence suggests that the peripheral immune system communicates with central nervous system and the effect propagates through microglial and lymphocyte crosstalk, especially during neuro-inflammation. Although, there is previous literature indicating changes in lymphocyte population in schizophrenia, detailed studies with respect to T and B cells are scarce. Mucosal associated invariant T (MAIT) cells are functionally associated with the gut microbiome. The gut microbiome has been implicated in the pathogenesis of schizophrenia. However, there is no information on the frequency of MAIT cells in schizophrenia. Hence, we investigated changes in proportions of T cells, B cells and MAIT cells in peripheral blood mononuclear cells derived from antipsychotic-free patients with schizophrenia in comparison to healthy controls. In line with earlier reports, we noted perturbations in T_h17 cells. This study for the first time reports changes in frequencies of MAIT cells in a homogenous population of antipsychotic-free patients with schizophrenia. These changes, though not common across all patients nevertheless point to the fact that inflammation is prevalent in a significant subset of schizophrenia cases.

B-cells and schizophrenia: A promising link or a finding lost in translation?

Recent genetic studies have suggested a potential role for B-cells in the pathogenesis of schizophrenia. Greater insight in the functioning of B-cells in patients with schizophrenia is therefore of importance. In this narrative review we aim to give an overview of the current literature on B-cells and schizophrenia. We found no evidence for altered numbers of these cells in blood. We did find support for increased levels of B-cell related cytokines and certain autoantibodies. Studies on B-cell development and function, or their numbers in cerebrospinal fluid or brain tissue are very limited. Based on the available data we appraise whether various B-cell mediated pathological mechanisms are likely to play a role in schizophrenia and provide directions for future research.

[Update on anti-N-methyl-D-aspartate receptor encephalitis]

Autoimmune encephalitis is a group of autoimmune inflammatory disorders affecting both grey and white matter of the central nervous system. Encephalitis with autoantibodies against the N‑methyl-D-aspartate receptor (NMDA-R) is the most frequent autoimmune encephalitis syndrome presenting with a characteristic sequence of psychiatric and neurological symptoms. Treatment necessitates a close interdisciplinary cooperation. This article provides an update on the current knowledge on diagnostic standards, pathogenesis, and treatment strategies for anti-NMDA-R encephalitis from psychiatric and neurological perspectives.

A study of anti-gliadin antibodies in first-episode patients with schizophrenia among a Chinese population

A recent study suggested that digestion-resistant peptides derived from wheat gluten (mainly gliadin) could induce the secretion of anti-gliadin IgG antibodies in patients with schizophrenia. This research was then designed to replicate this initial finding in 134 drug-naïve patients with first-episode schizophrenia and 160 healthy controls. An enzyme-linked immunosorbent assay was developed in-house with 8 gliadin-derived peptide antigens to test anti-gliadin IgG antibodies in the circulation. The results showed that schizophrenia patients had significantly higher levels of plasma anti-AL2G2 IgG and anti-ABO3a IgG than healthy controls. Based on the specificity of 95%, anti-AL2G2 IgG assay had a sensitivity of 12.7% and anti-ABO3a IgG assay had a sensitivity of 17.2% for anti-ABO3a IgG assay. Increased levels of anti-AL2G2 and anti-ABC3a IgG antibodies were not correlated with total IgG levels in either the patient group or the control group. In conclusion, circulating IgG against AL2G2 and ABO3a may be useful biomarkers for identification of a gluten-sensitive subgroup of schizophrenia in the Chinese population although the present results are rather different from the work performed in a British population.

Antibodies in the Diagnosis, Prognosis, and Prediction of Psychotic Disorders

Blood-based biomarker discovery for psychotic disorders has yet to impact upon routine clinical practice. In physical disorders antibodies have established roles as diagnostic, prognostic and predictive (theranostic) biomarkers, particularly in disorders thought to have a substantial autoimmune or infective aetiology. Two approaches to antibody biomarker identification are distinguished: a "top-down" approach, in which antibodies to specific antigens are sought based on the known function of the antigen and its putative role in the disorder, and emerging "bottom-up" or "omics" approaches that are agnostic as to the significance of any one antigen, using high-throughput arrays to identify distinctive components of the antibody repertoire. Here we review the evidence for antibodies (to self-antigens as well as infectious organism and dietary antigens) as biomarkers of diagnosis, prognosis, and treatment response in psychotic disorders. Neuronal autoantibodies have current, and increasing, clinical utility in the diagnosis of organic or atypical psychosis syndromes. Antibodies to selected infectious agents show some promise in predicting cognitive impairment and possibly other symptom domains (eg, suicidality) within psychotic disorders. Finally, infectious antibodies and neuronal and other autoantibodies have recently emerged as potential biomarkers of response to anti-infective therapies, immunotherapies, or other novel therapeutic strategies in psychotic disorders, and have a clear role in stratifying patients for future clinical trials. As in nonpsychiatric disorders, combining biomarkers and large-scale use of "bottom-up" approaches to biomarker identification are likely to maximize the eventual clinical utility of antibody biomarkers in psychotic disorders.

Low plasma concentrations of N-methyl-d-aspartate receptor subunits as a possible biomarker for psychosis

BACKGROUND

N-methyl-d-aspartate receptor (NMDAR) has been largely implicated in the neurobiology of schizophrenia and other psychosis. Aiming to evaluate their potential as peripheral biomarkers for psychosis, we quantified the plasma concentrations of NR1 and NR2 NMDAR subunits of first-episode psychosis patients in their first contact with mental health services due to psychotic symptoms, compared with siblings and matched community-based controls.

METHODS

The quantifications of NR1 and NR2 plasma concentrations were performed by ELISA. Data were analysed by nonparametric tests and Receiver Operating Curve (ROC) analysis.

RESULTS

We included 166 first-episode psychosis patients (mean age = 30.3 ± 12.2 years; 64% men), with the diagnosis of schizophrenia spectrum (n = 84), bipolar disorder (n = 51) and psychotic depression (n = 31), 76 siblings (mean age = 31.5 ± 11.0 years; 30.3% men) and 166 healthy community-based controls (mean age = 31.4 ± 12.0 years; 63.9% men). NMDAR subunits were significantly lower in patients compared with siblings and controls (p < 0.001), except by NR1 plasma concentrations of bipolar patients compared with siblings and controls. NR1 plasma concentrations lower than 17.65 pg/ml (AUC = 0.621) showed sensitivity of 42.8%, specificity of 84.3%, positive predictive value (PPV) of 73.2% and negative predictive value (NPV) of 59.6%. Individuals with NR2 plasma concentrations lower than 2.92 ng/ml (AUC = 0.801) presented a 10.61-fold increased risk of psychosis, with a sensibility of 71.9%, specificity of 80.6%, PPV of 79.0% and NPV of 73.9%.

CONCLUSIONS

This is the first study reporting the measurement and the reduction of NR1 and NR2 NMDAR subunits plasma concentrations in psychiatric disorders. In particular, the NR2 subunit may be a possible plasma biomarker for psychosis.

Study of Novel Autoantibodies in Schizophrenia

A recent genome-wide association (GWA) study confirmed 108 genetic loci that were strongly associated with schizophrenia. Fifteen schizophrenia-associated genes were selected for this study based on a number of selection criteria including their high expression in both brain tissues and B-lymphocyte cells. We aimed to investigate whether individuals with schizophrenia showed different levels of plasma IgG antibodies against protein-derived fragments encoded by these 15 genes. A total of 356 plasma samples were used to analyze circulating IgG antibodies against 18 target peptide antigens using an in-house enzyme-linked immunosorbent assay. Of 18 antigens tested, 6 (derived from DPYD, MAD1L1, ZNF804A, DRD2, TRANK1, and MMP16, respectively) showed increased IgG levels and 3 (derived from TSNARE1, TCF4, and VRK2, respectively) showed decreased IgG levels in patients with schizophrenia compared with control subjects. Receiver operating characteristic (ROC) curve analysis revealed that the anti-TRANK1 IgG assay had the area under the ROC curve of 0.68 (95% CI = 0.62-0.73), with the highest sensitivity of 20.7% against specificity of 95.2% among all 18 tests. There was no difference in positivity of anti-double strand DNA IgG between the patient group and the control group and no correlation between total IgG levels and each individual IgG level tested. Although risperidone treatment showed confounding effects on overall IgG levels in the circulation (combined P = .005), anti-TRANK1 IgG levels did not appear to be significantly affected (t = 1.358, P = .176). In conclusion, this study suggests that circulating anti-TRANK1 IgG is likely to serve as a biomarker for identification of a subgroup of schizophrenia.

Autoimmune phenotypes in schizophrenia reveal novel treatment targets

Typical and atypical antipsychotics are the first-line treatments for schizophrenia, but these classes of drugs are not universally effective, and they can have serious side effects that impact compliance. Antipsychotic drugs generally target the dopamine pathways with some variation. As research of schizophrenia pathophysiology has shifted away from a strictly dopamine-centric focus, the development of new pharmacotherapies has waned. A field of inquiry with centuries-old roots is gaining traction in psychiatric research circles and may represent a new frontier for drug discovery in schizophrenia. At the forefront of this investigative effort is the immune system and its many components, pathways and phenotypes, which are now known to actively engage the brain. Studies in schizophrenia reveal an intricate association of environmentally-driven immune activation in concert with a disrupted genetic template. A consistent conduit through this gene-environmental milieu is the gut-brain axis, which when dysregulated can generate pathological autoimmunity. In this review, we present epidemiological and biochemical evidence in support of an autoimmune component in schizophrenia and depict gut processes and a dysbiotic microbiome as a source and perpetuator of autoimmune dysfunction in the brain. Within this framework, we review the role of infectious agents, inflammation, gut dysbioses and autoantibody propagation on CNS pathologies such as neurotransmitter receptor hypofunction and complement pathway-mediated synaptic pruning. We then review the new pharmacotherapeutic horizon and novel agents directed to impact these pathological conditions. At the core of this discourse is the understanding that schizophrenia is etiologically and pathophysiologically heterogeneous and thus its treatment requires individualized attention with disease state variants diagnosed with objective biomarkers.

Tracking single membrane targets of human autoantibodies using single nanoparticle imaging

BACKGROUND

Over the past decade, an increasing number of neurological and neuropsychiatric diseases have been associated with the expression of autoantibodies directed against neuronal targets, including neurotransmitter receptors. Although cell-based assays are routinely used in clinics to detect the presence of immunoglobulins, such tests often provide heterogeneous outcomes due to their limited sensitivity, especially at low titers. Thus, there is an urging need for new methods allowing the detection of autoantibodies in seropositive patients that cannot always be clinically distinguished from seronegative ones.

NEW METHOD

Here we make a case for single nanoparticle imaging approaches as a highly sensitive antibody detection assay. Through high-affinity interactions between functionalized nanoparticles and autoantibodies that recognize extracellular domains of membrane neuronal targets, single nanoparticle imaging allows a live surface staining of transmembrane proteins and gives access to their surface dynamics.

RESULTS AND COMPARISON WITH EXISTING METHOD(S)

We show here that this method is well-suited to detect low titers of purified immunoglobulin G (IgG) from first-episode psychotic patients and demonstrate that these IgG target glutamatergic N-Methyl-d-Aspartate receptors (NMDAR) in live hippocampal neurons. The molecular behaviors of targeted membrane receptors were indistinguishable from those of endogenous GluN1 NMDAR subunit and were virtually independent of the IgG concentration present in the sample contrary to classical cell-based assays.

CONCLUSIONS

Single nanoparticle imaging emerges as a real-time sensitive method to detect IgG directed against neuronal surface proteins, which could be used as an additional step to rule out ambiguous seropositivity diagnoses.

Brain-relevant antibodies in first-episode psychosis: a matched case-control study

BACKGROUND

There has been much recent excitement about the possibility that some cases of psychosis may be wholly due to brain-reactive antibodies, with antibodies to N-methyl-D-aspartate receptor (NMDAR) and the voltage-gated potassium channel (VGKC)-complex reported in a few patients with first-episode psychosis (FEP).

METHODS

Participants were recruited from psychiatric services in South London, UK, from 2009 to 2011 as part of the Genetics and Psychosis study. We conducted a case-control study to examine NMDAR and VGKC-complex antibody levels and rates of antibody positivity in 96 patients presenting with FEP and 98 controls matched for age and sex. Leucine-rich glioma inactiviated-1 (LGI1) and contactin-associated protein (CASPR) antibodies were also measured. Notably, patients with suspicion of organic disease were excluded.

RESULTS

VGKC-complex antibodies were found in both cases (n = 3) and controls (n = 2). NMDAR antibody positivity was seen in one case and one control. Either LGI1-Abs or CASPR2-Abs were found in three cases and three controls. Neuronal antibody staining, consistent with the above results or indicating potential novel antigens, was overall positive in four patients but also in six controls. Overall, antibody positivity was at low levels only and not higher in cases than in controls.

CONCLUSIONS

This case-control study of the prevalence of antibodies in FEP does not provide evidence to support the hypothesis that FEP is associated with an immune-mediated process in a subgroup of patients. Nevertheless, as other bio-clinical factors may influence the effect of such antibodies in a given individual, and patients with organic neurological disease may be misdiagnosed as FEP, the field requires more research to put these findings in context.

Procalcitonin and C - reactive protein as peripheral inflammatory markers in antipsychotic drug-free schizophrenia patients

Inflammation is considered to be relevant in pathophysiology of schizophrenia. Existing literature indicates that controlling inflammation may be helpful in patient management. Procalcitonin (PCT) is an established marker of inflammation which has not been well studied in context with schizophrenia. The study recruited 34 schizophrenia patients free of antipsychotic treatment and 24 healthy controls without any signs of inflammation. Plasma C reactive protein was quantified using a high sensitivity turbidimetric assay. Plasma PCT levels was estimated by sandwich ELISA. The study ruled out autoimmune antibodies by ANA and RF tests which exclude confounding factors contributing to inflammation. The data shows a subgroup of patients 17/34 (50%) have either elevated PCT or CRP levels. This study is the first to report PCT values in antipsychotic drug-free patients with schizophrenia.

Pathogenicity of Antibodies against NMDA Receptor: Molecular Insights into Autoimmune Psychosis

Recent years have seen a flourishing literature on detection of circulating autoantibodies against neurotransmitter receptors in patients with neuropsychiatric disorders. These studies have generated hope for a better understanding of the underlying molecular dysfunctions and for appropriate therapeutic strategies. However, the detection of these autoantibodies in healthy subjects, and the lack of mechanistic insights have fostered debate about the pathogenic role of such autoantibodies. Here, we specifically discuss the biological evidence linking autoantibodies directed against the glutamatergic N-methyl-d-aspartate (NMDA) receptor (NMDAR-Abs) and psychosis, emphasising recent single-molecule imaging investigations that unveiled the impaired surface trafficking of NMDAR in the presence of NMDAR-Abs from psychotic patients. Although still in its infancy, the hypothesis that NMDAR-Abs from patients with psychosis play a pathogenic role is thus gaining support, opening avenues of fundamental and translational investigations.

Interleukin-3, symptoms and cognitive deficits in first-episode drug-naïve and chronic medicated schizophrenia

Previous studies consistently showed that IL-3 signaling may be involved in the pathophysiology of schizophrenia. However, investigations of associations between IL-3 and the neurocognitive impairments are lacking, including the study of how this may vary with stage of illness. We recruited 45 first-episode drug-naïve (FE-Sz), 35 chronic medicated schizophrenia (Ch-Sz) and 40 healthy controls (HC) and examined the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and serum IL-3. Altered serum IL-3 levels were found in both patient groups compared with HC group (both p < 0.001). There were significantly lower neurocognitive scores on the RBANS and nearly all of its five subscales, except for Visuospatial/Constructional index in both FE-Sz and Ch-Sz patients vs healthy controls. Moreover, a significant reduction in Immediate memory index (p = 0.021) and a trend-level reduction in RBANS total score (p = 0.094) in Ch-Sz than FE-Sz patients. Interestingly, there was a significant negative correlation between IL-3 and the Immediate memory index only in Ch-Sz patients (p = 0.03). Our findings showed that neurocognitive impairments present in schizophrenia emerge during the first episode with further diminished functioning with disease progression, and IL-3 may be involved in the immediate memory deficits in the chronic phase of schizophrenia.

Cytokines and C-reactive protein alterations with respect to cognitive impairment in schizophrenia and bipolar disorder: A systematic review

BACKGROUND

The aim of this article was to perform a systematic review of studies investigating the association between peripheral levels of cytokines and C-reactive protein (CRP), cytokine gene polymorphisms and cognition in patients with schizophrenia and bipolar disorder (BD).

METHODS

The following databases: PubMed, CINAHL Complete, Academic Search Complete, ERIC and Health Source: Nursing/Academic Edition databases were searched according to the PRISMA guidelines. We included studies that investigated the association between peripheral levels of CRP and cytokines, cytokine gene polymorphisms and cognitive performance in schizophrenia and/or BD patients. Subsequently, quality assessment of eligible publications was performed. Results were synthesized by discussing main findings around correlations between inflammatory markers and cognition.

RESULTS

Most consistent results indicate worse cognitive performance in schizophrenia patients with higher CRP levels. Less consistent evidence suggests better cognitive functioning of schizophrenia patients with higher levels of tumour necrosis factor-α (TNF-α). Evidence for the involvement of other cytokines in cognitive impairment in patients with schizophrenia is less convincing due to discordant results or scarcity of studies. Due to low number of studies, it is difficult to draw conclusions on the involvement of CRP and cytokine alterations in the development of cognitive deficits in BD. Single studies suggest the role of CRP, interleukin(IL)-1 receptor antagonist, IL-6 and TNF-α with its receptors in the development of cognitive impairment in BD.

CONCLUSIONS

Peripheral inflammation might be related to cognitive deficits in schizophrenia and BD. Unequivocal conclusions cannot be made due to methodological heterogeneity and low number of studies investigating particular cytokines.

Meta-analysis of Cerebrospinal Fluid Cytokine and Tryptophan Catabolite Alterations in Psychiatric Patients: Comparisons Between Schizophrenia, Bipolar Disorder, and Depression

INTRODUCTION

Schizophrenia, bipolar disorder, and major depressive disorder (MDD) have all been associated with immune system dysfunction, including aberrant cerebrospinal fluid (CSF) levels of cytokines and tryptophan catabolites; however, the pattern of alterations has not been compared across disorders. We performed a meta-analysis of CSF cytokine and tryptophan catabolites in patients with these major psychiatric disorders.

METHODS

Articles were identified by searching Pub Med, PsycInfo, and Web of Science, and the reference lists of these studies.

RESULTS

Twenty-eight studies met the inclusion criteria (16 schizophrenia, 4 bipolar disorder, and 9 MDD). CSF levels of IL-1β and kynurenic acid were significantly increased in patients with schizophrenia and bipolar disorder compared to healthy controls (P < .001). CSF levels of IL-6 and IL-8 were significantly increased in patients with schizophrenia and MDD compared to healthy controls (P ≤ .013).

DISCUSSION

There is preliminary evidence for similarities in the pattern of CSF cytokine and tryptophan catabolite alterations across major psychiatric disorders, although findings must be interpreted with caution in light of small numbers of studies/subjects. Many CSF alterations are also concordant with those in the peripheral blood, particularly for schizophrenia. Findings have important implications for our understanding of the pathophysiology and treatment of major psychiatric disorders.

"Immune Gate" of Psychopathology-The Role of Gut Derived Immune Activation in Major Psychiatric Disorders

Interaction between the gastrointestinal tract (GI) and brain functions has recently become a topic of growing interest in psychiatric research. These multidirectional interactions take place in the so-called gut-brain axis or more precisely, the microbiota-gut-brain axis. The GI tract is the largest immune organ in the human body and is also the largest surface of contact with the external environment. Its functions and permeability are highly influenced by psychological stress, which are often a precipitating factor in the first episode, reoccurrence and/or deterioration of symptoms of psychiatric disorders. In recent literature there is growing evidence that increased intestinal permeability with subsequent immune activation has a major role in the pathophysiology of various psychiatric disorders. Numerous parameters measured in this context seem to be aftermaths of those mechanisms, yet at the same time they may be contributing factors for immune mediated psychopathology. For example, immune activation related to gut-derived bacterial lipopolysaccharides (LPS) or various food antigens and exorphins were reported in major depression, schizophrenia, bipolar disorder, alcoholism and autism. In this review the authors will summarize the evidence and roles of such parameters and their assessment in major psychiatric disorders.