Brain morphological changes associated with exposure to HSV1 in first-episode schizophrenia

Shared interactions of six neurotropic viruses with 38 human proteins: a computational and literature-based exploration of viral interactions and hijacking of human proteins in neuropsychiatric disorders

INTRODUCTION

Viral infections may disrupt the structural and functional integrity of the nervous system, leading to acute conditions such as encephalitis, and neuropsychiatric conditions as mood disorders, schizophrenia, and neurodegenerative diseases. Investigating viral interactions of human proteins may reveal mechanisms underlying these effects and offer insights for therapeutic interventions. This study explores molecular interactions of virus and human proteins that may be related to neuropsychiatric disorders.

METHODS

Herpes Simplex Virus-1 (HSV-1), Cytomegalovirus (CMV), Epstein-Barr Virus (EBV), Influenza A virus (IAV) (H1N1, H5N1), and Human Immunodeficiency Virus (HIV1&2) were selected as key viruses. Protein structures for each virus were accessed from the Protein Data Bank and analyzed using the HMI-Pred web server to detect interface mimicry between viral and human proteins. The PANTHER classification system was used to categorize viral-human protein interactions based on function and cellular localization.

RESULTS

Energetically favorable viral-human protein interactions were identified for HSV-1 (467), CMV (514), EBV (495), H1N1 (3331), H5N1 (3533), and HIV 1&2 (62425). Besides immune and apoptosis-related pathways, key neurodegenerative pathways, including those associated with Parkinson's and Huntington's diseases, were frequently interacted. A total of 38 human proteins, including calmodulin 2, Ras-related botulinum toxin substrate 1 (Rac1), PDGF-β, and vimentin, were found to interact with all six viruses.

CONCLUSION

The study indicates a substantial number of energetically favorable interactions between human proteins and selected viral proteins, underscoring the complexity and breadth of viral strategies to hijack host cellular mechanisms. Further in vivo and in vitro validation is required to understand the implications of these interactions.

Indicators of HSV1 Infection, ECM-Receptor Interaction, and Chromatin Modulation in a Nuclear Family with Schizophrenia

Schizophrenia (SCZ) is a complex psychiatric disorder with high heritability; identifying risk genes is essential for deciphering the disorder's pathogenesis and developing novel treatments. Using whole-exome sequencing, we screened for mutations within protein-coding sequences in a single family of patients with SCZ. In a pathway enrichment analysis, we found multiple transmitted variant genes associated with two KEGG pathways: herpes simplex virus 1 (HSV1) infection and the extracellular matrix (ECM)-receptor interaction. When searching for rare variants, six variants, SLC6A19p.L541R, CYP2E1p.T376S, NAT10p.E811D, N4BP1p.L7V, CBX2p.S520C, and ZNF460p.K190E, segregated with SCZ. A bioinformatic analysis showed that three of these mutated genes were associated with chromatin modulation. We found that HSV1 infection, ECM-receptor interaction pathways, and epigenetic mechanisms may contribute to the pathogenesis of SCZ in certain families. The identified polygenetic risk factors from the sample family provide distinctive underlying biological mechanisms of the pathophysiology of SCZ and may be useful in clinical practice and patient care.

Therapeutic Implications of the Microbial Hypothesis of Mental Illness

There is increasingly compelling evidence that microorganisms may play an etiological role in the emergence of mental illness in a subset of the population. Historically, most work has focused on the neurotrophic herpesviruses, herpes simplex virus type 1 (HSV-1), cytomegalovirus (CMV), and Epstein-Barr virus (EBV) as well as the protozoan, Toxoplasma gondii. In this chapter, we provide an umbrella review of this literature and additionally highlight prospective studies that allow more mechanistic conclusions to be drawn. Next, we focus on clinical trials of anti-microbial medications for the treatment of psychiatric disorders. We critically evaluate six trials that tested the impact of anti-herpes medications on inflammatory outcomes in the context of a medical disorder, nine clinical trials utilizing anti-herpetic medications for the treatment of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) or schizophrenia, and four clinical trials utilizing anti-parasitic medications for the treatment of schizophrenia. We then turn our attention to evidence for a gut dysbiosis and altered microbiome in psychiatric disorders, and the potential therapeutic effects of probiotics, including an analysis of more than 10 randomized controlled trials of probiotics in the context of schizophrenia, bipolar disorder (BD), and major depressive disorder (MDD).

Schizophrenia, Human Leukocyte Antigen (HLA), and Herpes Viruses: Immunogenetic Associations at the Population Level

Several factors have been implicated in schizophrenia (SZ), including human herpes viruses (HHV) and the adaptive immunity Human Leukocyte Antigen (HLA) genes. Here we investigated these issues in 2 complementary ways. In one analysis, we evaluated SZ-HLA and HHV-HLA associations at the level of a single allele by computing (a) a SZ-HLA protection/susceptibility (P/S) score based on the covariance between SZ and 127 HLA allele prevalences in 14 European countries, (b) estimating in silico HHV-HLA best binding affinities for the 9 HHV strains, and (c) evaluating the dependence of P/S score on HHV-HLA binding affinities. These analyses yielded (a) a set of 127 SZ-HLA P/S scores, varying by >200× (maximum/minimum), which could not be accounted for by chance, (b) a set of 127 alleles × 9 HHV best-estimated affinities, varying by >600×, and (c) a set of correlations between SZ-HLA P/S scores and HHV-HLA binding which indicated a prominent role of HHV1. In a subsequent analysis, we extended these findings to the individual person by taking into account the fact that every individual carries 12 HLA alleles and computed (a) the average SZ-HLA P/S scores of 12 randomly chosen alleles (2 per gene), an indicator of HLA-based SZ P/S for an individual, and (b) the average of the corresponding HHV estimated affinities for those alleles, an indicator of overall effectiveness of HHV-HLA binding. We found (a) that HLA protection for SZ was significantly more prominent than susceptibility, and (b) that protective SZ-HLA scores were associated with higher HHV-HLA binding affinities, indicating that HLA binding and subsequent elimination of several HHV strains may confer protection against schizophrenia.

Herpes simplex virus 1 infection on grey matter and general intelligence in severe mental illness

Schizophrenia and bipolar disorder are severe mental illnesses (SMI) linked to both genetic and environmental factors. Herpes simplex virus 1 (HSV1) is a common neurotropic pathogen which after the primary infection establishes latency with periodic reactivations. We hypothesized that the latent HSV1 infection is associated with brain structural abnormalities and cognitive impairment, especially in SMI. We included 420 adult patients with SMI (schizophrenia or bipolar spectrum) and 481 healthy controls. Circulating HSV1 immunoglobulin G concentrations were measured with immunoassays. We measured the total grey matter volume (TGMV), cortical, subcortical, cerebellar and regional cortical volumes based on T1-weighted MRI scans processed in FreeSurfer v6.0.0. Intelligence quotient (IQ) was assessed with the Wechsler Abbreviated Scale of Intelligence. Seropositive patients had significantly smaller TGMV than seronegative patients (642 cm³ and 654 cm³, respectively; p = 0.019) and lower IQ (104 and 107, respectively; p = 0.018). No TGMV or IQ differences were found between seropositive and seronegative healthy controls. Post-hoc analysis showed that (a) in both schizophrenia and bipolar spectrum, seropositive patients had similarly smaller TGMV than seronegative patients, whereas the HSV1-IQ association was driven by the schizophrenia spectrum group, and (b) among all patients, seropositivity was associated with smaller total cortical (p = 0.016), but not subcortical or cerebellar grey matter volumes, and with smaller left caudal middle frontal, precentral, lingual, middle temporal and banks of superior temporal sulcus regional cortical grey matter volumes. The results of this cross-sectional study indicate that HSV1 may be an environmental factor associated with brain structural abnormalities and cognitive impairment in SMI.

Structural covariance networks in schizophrenia: A systematic review Part II

BACKGROUND

Examination of structural covariance network (SCN) is gaining prominence among the strategies to delineate dysconnectivity that case-control morphometric comparisons cannot address. Part II of this review extends on the part I of the review that included SCN studies using statistical approaches by examining SCN studies applying graph theoretic approaches to elucidate network properties in schizophrenia. This review also includes SCN studies using graph theoretic or statistical approaches on persons at-risk for schizophrenia.

METHODS

A systematic literature search was conducted for peer-reviewed publications using different keywords and keyword combinations for schizophrenia and risk for schizophrenia. Thirteen studies on schizophrenia and five on persons at risk for schizophrenia met the criteria.

RESULTS

A variety of findings from over the last 1½ decades showing qualitative and quantitative differences in the global and local structural connectome in schizophrenia are described. These observations include altered hub patterns, disrupted network topology and hierarchical organization of the brain, and impaired connections that may be localized to default mode, executive control, and dorsal attention networks. Some of these connectomic alterations were observed in persons at-risk for schizophrenia before the onset of the illness.

CONCLUSIONS

Observed disruptions may reduce network efficiency and capacity to integrate information. Further, global connectomic changes were not schizophrenia-specific but local network changes were. Existing studies have used different atlases for brain parcellation, examined different morphometric features, and patients at different stages of illness making it difficult to conduct meta-analysis. Future studies should harmonize such methodological differences to facilitate meta-analysis and also elucidate causal underpinnings of dysconnectivity.

Herpes Simplex Virus Type-1 Infection: Associations with Inflammation and Cognitive Aging in Relation to Schizophrenia

Most persons experience cognitive decline as they grow older. The term "cognitive aging," coined to describe milder varieties of cognitive decline, is likely to be due to multiple causes. Persistent or repeated infections of the central nervous system (whether subclinical or diagnosable) can cause damage to neurons directly or indirectly through inflammation resulting in incremental neuronal damage, thus eroding cognitive reserve. This possibility has not been considered widely. We evaluated the data linking persistent infection with herpes simplex virus type 1 (HSV-1) and cognitive aging by applying the Bradford Hill criteria. Despite inherent problems in establishing causal relations for chronic disorders, our analyses suggest plausible links. These studies are pertinent for patients with schizophrenia, who are particularly vulnerable due to disorder-related cognitive impairment. Further investigations are warranted to test a causal hypothesis, particularly prospective studies and intervention studies.

Herpes Simplex Virus Type 1 infection is associated with suicidal behavior and first registered psychiatric diagnosis in a healthy population

Increasing evidence shows that latent infections and inflammation is associated with cognitive and behavioral changes in humans. This case-control study investigates the association between Herpes Simplex Virus Type 1 (HSV-1) infection and C-reactive Protein (CRP) levels, and psychiatric disorders and suicidal behavior. Public health register data from 81,912 participants in the Danish Blood Donor Study, were reviewed to identify individuals registered with an ICD-10 code of any psychiatric diagnosis, or who had attempted or committed suicide. We found 1,504 psychiatric cases and 353 suicidal cases; for all cases, controls were frequency-matched by age and sex, resulting in 5,336 participants. Plasma samples were analyzed for IgG-class antibodies against HSV-1 and CRP. HSV-1 infection was associated with suicidal behavior (odds-ratio, 1.40; 95% confidence interval [CI] 1.11-1.77). Accounting for temporality, HSV-1 infection was associated with having first psychiatric disorder after the date of blood collection (incidence rate ration, 1.44; 95% CI, 1.05-1.95). No association between CRP and psychiatric disorders or suicidal behavior was found. The finding that HSV-1 was associated with suicidal behavior and first psychiatric disorder indicates that infection may play a role in the etiology and pathogenesis of suicidal behavior and development of psychiatric disorders.

From Infection to the Microbiome: An Evolving Role of Microbes in Schizophrenia

The study of microorganisms such as bacteria, viruses, archaea, fungi, and protozoa in the context of psychiatric disorders may be surprising to some. This intersection of disciplines, however, has a rich history and is currently revitalized by newfound functions of the microbiome and the gut-brain axis in human diseases. Schizophrenia, in particular, fits this model as a disorder with gene and environmental roots that may be anchored in the immune system. In this context, the combination of a precisely timed pathogen exposure in a person with genetically encoded altered immunity may have especially destructive consequences for the central nervous system (CNS). Furthermore, significant components of immunity, such as the development of the immune response and the concept of immune tolerance, are largely dictated by the commensal residents of the microbiome. When this community of microbes is imbalanced, perhaps as the result of a pathogen invasion, stress, or immune gene deficiency, a pathological cycle of localized inflammation, endothelial barrier compromise, translocation of gut-derived products, and systemic inflammation may ensue. If these pathologies enable access of gut and microbial metabolites and immune molecules to the CNS across the blood-brain barrier (BBB), and studies of the gut-brain axis support this hypothesis, a worsening of cognitive deficits and psychiatric symptoms is predicted to occur in susceptible individuals with schizophrenia. In this chapter, we review the role of microbes in various stages of this model and how these organisms may contribute to documented phenotypes of schizophrenia. An increased understanding of the role of pathogens and the microbiome in psychiatric disorders will better guide the development of microbial and immune-based therapeutics for disease prevention and treatment.

Molecular Mechanisms for Herpes Simplex Virus Type 1 Pathogenesis in Alzheimer's Disease

This review focuses on research in the areas of epidemiology, neuropathology, molecular biology and genetics that implicates herpes simplex virus type 1 (HSV-1) as a causative agent in the pathogenesis of sporadic Alzheimer’s disease (AD). Molecular mechanisms whereby HSV-1 induces AD-related pathophysiology and pathology, including neuronal production and accumulation of amyloid beta (Aβ), hyperphosphorylation of tau proteins, dysregulation of calcium homeostasis, and impaired autophagy, are discussed. HSV-1 causes additional AD pathologies through mechanisms that promote neuroinflammation, oxidative stress, mitochondrial damage, synaptic dysfunction, and neuronal apoptosis. The AD susceptibility genes apolipoprotein E (APOE), phosphatidylinositol binding clathrin assembly protein (PICALM), complement receptor 1 (CR1) and clusterin (CLU) are involved in the HSV lifecycle. Polymorphisms in these genes may affect brain susceptibility to HSV-1 infection. APOE, for example, influences susceptibility to certain viral infections, HSV-1 viral load in the brain, and the innate immune response. The AD susceptibility gene cholesterol 25-hydroxylase (CH25H) is upregulated in the AD brain and is involved in the antiviral immune response. HSV-1 interacts with additional genes to affect cognition-related pathways and key enzymes involved in Aβ production, Aβ clearance, and hyperphosphorylation of tau proteins. Aβ itself functions as an antimicrobial peptide (AMP) against various pathogens including HSV-1. Evidence is presented supporting the hypothesis that Aβ is produced as an AMP in response to HSV-1 and other brain infections, leading to Aβ deposition and plaque formation in AD. Epidemiologic studies associating HSV-1 infection with AD and cognitive impairment are discussed. Studies are reviewed supporting subclinical chronic reactivation of latent HSV-1 in the brain as significant in the pathogenesis of AD. Finally, the rationale for and importance of clinical trials treating HSV-1-infected MCI and AD patients with antiviral medication is discussed.

Emotion discrimination in humans: Its association with HSV-1 infection and its improvement with antiviral treatment

BACKGROUND

Herpes simplex virus, type 1 (HSV-1) infects over 3.4 billion people, world-wide. Though it can cause encephalitis, in the vast majority it is asymptomatic, with lifelong latent infection in neurons. HSV-1 infected individuals have greater cognitive dysfunction than uninfected individuals, particularly persons with schizophrenia - even without encephalitis. We investigated whether HSV-1 related cognitive dysfunction is progressive or remediable.

METHODS

In a prospective naturalistic follow up sample (PNFU), temporal changes in cognitive functions were analyzed in relation to baseline HSV-1 infection in persons with/without schizophrenia (N=226). Independently, in a randomized controlled trial (RCT), HSV-1 infected, clinically stabilized SZ outpatients received Valacyclovir (VAL, an HSV-1 specific antiviral, 1.5G twice daily for 16weeks) or placebo (PLA) added to standard antipsychotic treatment, using a stratified randomization design, following placebo run-in (N=67). In both samples, HSV-1 infection (seropositivity) was estimated using serum IgG antibodies. Clinical evaluations were blinded to HSV-1 or treatment status. Standardized Z scores for accuracy on eight cognitive domains were analyzed for temporal trajectories using generalized linear models (PNFU) and VAL/PLA differences compared with intent to treat analyses (RCT).

RESULTS

PNFU: At baseline, HSV-1 infected participants had significantly lower accuracy scores for Emotion Identification and Discrimination (EMOD), Spatial memory and Spatial ability, regardless of SZ diagnosis (p=0.025, 0.029, 0.046, respectively). They also had significantly steeper temporal worsening for EMOD (p=0.03). RCT: EMOD improved in VAL-treated patients (p=0.048, Cohen's d=0.43).

CONCLUSIONS

A proportion of age related decline in EMOD is attributable to HSV-1 infection.

Association between structural and functional brain alterations in drug-free patients with schizophrenia: a multimodal meta-analysis

BACKGROUND

Neuroimaging studies have shown both structural and functional abnormalities in patients with schizophrenia. Recently, studies have begun to explore the association between structural and functional grey matter abnormalities. By conducting a meta-analysis on morphometric and functional imaging studies of grey matter alterations in drug-free patients, the present study aims to examine the degree of overlap between brain regions with anatomic and functional changes in patients with schizophrenia.

METHODS

We performed a systematic search of PubMed, Embase, Web of Science and the Cochrane Library to identify relevant publications. A multimodal analysis was then conducted using Seed-based d Mapping software. Exploratory analyses included jackknife, subgroup and meta-regression analyses.

RESULTS

We included 15 structural MRI studies comprising 486 drug-free patients and 485 healthy controls, and 16 functional MRI studies comprising 403 drug-free patients and 428 controls in our meta-analysis. Drug-free patients were examined to reduce pharmacological effects on the imaging data. Multimodal analysis showed considerable overlap between anatomic and functional changes, mainly in frontotemporal regions, bilateral medial posterior cingulate/paracingulate gyrus, bilateral insula, basal ganglia and left cerebellum. There were also brain regions showing only anatomic changes in the right superior frontal gyrus, left supramarginal gyrus, right lingual gyrus and functional alternations involving the right angular gyrus.

LIMITATIONS

The methodological aspects, patient characteristics and clinical variables of the included studies were heterogeneous, and we cannot exclude medication effects.

CONCLUSION

The present study showed overlapping anatomic and functional brain abnormalities mainly in the default mode (DMN) and auditory networks (AN) in drug-free patients with schizophrenia. However, the pattern of changes differed in these networks. Decreased grey matter was associated with decreased activation within the DMN, whereas it was associated with increased activation within the AN. These discrete patterns suggest different pathophysiological changes impacting structural and functional associations within different neural networks in patients with schizophrenia.

Association of cognitive function and liability to addiction with childhood herpesvirus infections: A prospective cohort study

Liability to substance use disorder (SUD) is largely nonspecific to particular drugs and is related to behavior dysregulation, including reduced cognitive control. Recent data suggest that cognitive mechanisms may be influenced by exposure to neurotropic infections, such as human herpesviruses. In this study, serological evidence of exposure to human herpesvirus Herpes simplex virus Type 1 (HSV-1), cytomegalovirus (CMV), and Epstein-Barr virus (EBV) as well as Toxoplasma gondii was determined in childhood (age ~11 years) in 395 sons and 174 daughters of fathers with or without SUD. Its relationships with a cognitive characteristic (IQ) in childhood and with risk for SUD in adulthood were examined using correlation, regression, survival, and path analyses. Exposure to HSV-1, EBV, and T. gondii in males and females, and CMV in males, was associated with lower IQ. Independent of that relationship, EBV in females and possibly in males, and CMV and possibly HSV-1 in females were associated with elevated risk for SUD. Therefore, childhood neurotropic infections may influence cognitive development and risk for behavior disorders such as SUD. The results may point to new avenues for alleviating cognitive impairment and SUD risk.

Common pattern of gray-matter abnormalities in drug-naive and medicated first-episode schizophrenia: a multimodal meta-analysis

Studies of schizophrenia at drug-naive state and on antipsychotic medication have reported a number of regions of gray-matter (GM) abnormalities but the reports have been inconsistent. The aim of this study was to conduct multimodal meta-analysis to compare the cross-sectional voxel-based morphometry studies of brain GM in antipsychotic-naive first-episode schizophrenia (AN-FES) and those with antipsychotic treatment within 1 year (AT-FES) to determine the similarities and differences in these groups. We conducted two separate meta-analyses containing 24 studies with a sample size of 801 patients and 957 healthy controls. A multimodal meta-analysis method was used to compare the findings between AN-FES and AT-FES. Meta-regression analyses were done to determine the influence of different variables including age, duration of illness, and positive and negative symptom scores. Finally, jack-knife analyses were done to test the robustness of the results. AN-FES and AT-FES showed common patterns of GM abnormalities in frontal (gyrus rectus), superior temporal, left hippocampal and insular cortex. GM in the left supramarginal gyrus and left middle temporal gyrus were found to be increased in AN-FES but decreased in AT-FES, whereas left median cingulate/paracingulate gyri and right hippocampus GM was decreased in AN-FES but increased in AT-FES. Findings suggest that both AN-FES and AT-FES share frontal, temporal and insular regions as common anatomical regions to be affected indicating these to be the primary regions of GM abnormalities in both groups.

The relationship of Chlamydophila pneumoniae with schizophrenia: The role of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) in this relationship

Several pathogens have been suspected of playing a role in the pathogenesis of schizophrenia. Chronic inflammation has been proposed to occur as a result of persistent infection caused by Chlamydophila pneumoniae cells that reside in brain endothelial cells for many years. It was recently hypothesized that brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) may play prominent roles in the development of schizophrenia. NT-3 and BDNF levels have been suggested to change in response to various manifestations of infection. Therefore, we aimed to elucidate the roles of BDNF and NT3 in the schizophrenia-C. pneumoniae infection relationship. RT-PCR, immunofluorescence and ELISA methods were used. Fifty patients suffering from schizophrenia and 35 healthy individuals were included as the patient group (PG) and the healthy control group (HCG), respectively. We detected persistent infection in 14 of the 50 individuals in the PG and in 1 of the 35 individuals in the HCG. A significant difference was found between the two groups (p<0.05). Twenty-two individuals in the PG and 13 in the HCG showed seropositivity for past C. pneumoniae infection, and no difference was observed between the groups (p>0.05). C. pneumoniae DNA was not detected in any group. A significant difference in NT-3 levels was observed between the groups, with very low levels in the PG (p<0.001). A significant difference in BDNF levels was also found, with lower levels in the PG (p<0.05). The mean serum NT-3 level was higher in the PG cases with C. pneumoniae seropositivity than in seronegative cases; however, this difference was not statistically significant (p>0.05). In conclusion, we suggest that NT-3 levels during persistent C. pneumoniae infection may play a role in this relationship.

Role of Immune and Autoimmune Dysfunction in Schizophrenia

In this chapter, we review data in support of the concept that immune system dysregulation is the most plausible explanation that reconciles gene by environmental interactions in schizophrenia. Early investigations of this topic demonstrated aspects of aberrant activation of humoral immunity, including autoimmunity, associated with schizophrenia, whereas current research efforts have expanded this theme to include elements of innate immunity. Advances in our understanding of inflammation and molecules of both the adaptive and innate immune system and their functional roles in standard brain physiology provide an important context by which schizophrenia might arise as the result of the coupling of immune and neurodevelopmental dysregulation.

Persistent infection by HSV-1 is associated with changes in functional architecture of iPSC-derived neurons and brain activation patterns underlying working memory performance

BACKGROUND

Herpes simplex virus, type 1 (HSV-1) commonly produces lytic mucosal lesions. It invariably initiates latent infection in sensory ganglia enabling persistent, lifelong infection. Acute HSV-1 encephalitis is rare and definitive evidence of latent infection in the brain is lacking. However, exposure untraceable to encephalitis has been repeatedly associated with impaired working memory and executive functions, particularly among schizophrenia patients.

METHODS

Patterns of HSV-1 infection and gene expression changes were examined in human induced pluripotent stem cell (iPSC)-derived neurons. Separately, differences in blood oxygenation level-dependent (BOLD) responses to working memory challenges using letter n-back tests were investigated using functional magnetic resonance imaging (fMRI) among schizophrenia cases/controls.

RESULTS

HSV-1 induced lytic changes in iPSC-derived glutamatergic neurons and neuroprogenitor cells. In neurons, HSV-1 also entered a quiescent state following coincubation with antiviral drugs, with distinctive changes in gene expression related to functions such as glutamatergic signaling. In the fMRI studies, main effects of schizophrenia (P = .001) and HSV-1 exposure (1-back, P = 1.76 × 10(-4); 2-back, P = 1.39 × 10(-5)) on BOLD responses were observed. We also noted increased BOLD responses in the frontoparietal, thalamus, and midbrain regions among HSV-1 exposed schizophrenia cases and controls, compared with unexposed persons.

CONCLUSIONS

The lytic/quiescent cycles in iPSC-derived neurons indicate that persistent neuronal infection can occur, altering cellular function. The fMRI studies affirm the associations between nonencephalitic HSV-1 infection and functional brain changes linked with working memory impairment. The fMRI and iPSC studies together provide putative mechanisms for the cognitive impairments linked to HSV-1 exposure.

Different presence of Chlamydia pneumoniae, herpes simplex virus type 1, human herpes virus 6, and Toxoplasma gondii in schizophrenia: meta-analysis and analytical study

In the present study we have performed both a meta-analysis and an analytical study exploring the presence of Chlamydia pneumoniae, herpes simplex virus type 1, human herpes virus 6, and Toxoplasma gondii antibodies in a sample of 143 schizophrenic patients and 143 control subjects. The meta-analysis was performed on papers published up to April 2014. The presence of serum immunoglobulin G and immunoglobulin A was performed by enzyme-linked immunosorbent assay test. The detection of microbial DNA in total peripheral blood was performed by nested polymerase chain reaction. The meta-analysis showed that: 1) C. pneumoniae DNA in blood and brain are more common in schizophrenic patients; 2) there is association with parasitism by T. gondii, despite the existence of publication bias; and 3) herpes viruses were not more common in schizophrenic patients. In our sample only anti-Toxoplasma immunoglobulin G was more prevalent and may be a risk factor related to schizophrenia, with potential value for prevention.

Neuroanatomical markers of genetic liability to psychosis and first episode psychosis: a voxelwise meta-analytical comparison

OBJECTIVES

To address at a meta-analytical level the neuroanatomical markers of genetic liability to psychosis and a of first episode of psychosis.

METHODS

Fifteen voxel-based morphometry (VBM) studies of antipsychotic-naive subjects at genetic high-risk (HR) for psychosis or with a first-episode psychosis (FEP) were included in a Signed Differential Mapping (SDM) meta-analysis. Publication bias was assessed with funnel plots and Egger's intercept. Heterogeneity was assessed with Q statistics and I (2) index.

RESULTS

The database comprised 458 HR and 206 antipsychotic-naïve FEP subjects, matched with controls. Gray matter (GM) reductions as compared to controls, were observed in the left parahippocampal gyrus and in the bilateral anterior cingulate gyrus in the HR group, and in the right superior temporal gyrus, in the left insula and in the left cerebellum in the FEP group. Further GM decreases were observed in the FEP group as compared to the HR group in the left anterior cingulate, in the right precuneus, in the left cerebellum and in the right superior temporal gyrus. Limitations. The cross-sectional nature of the included studies prevented the comparison of high risk subjects who later did or did not develop a psychotic episode. Other caveats are based on the methodological heterogeneity across individual imaging studies.

CONCLUSIONS

GM reductions in the anterior cingulate are markers of genetic liability to psychosis while reductions in the superior temporal gyrus and cerebellum can be interpreted as markers of a first onset of the illness.

Persistent viral pathogens and cognitive impairment across the life course in the third national health and nutrition examination survey

BACKGROUND

Herpesviruses have been linked to cognitive impairment in older individuals but little is known about the association in the general US population.

METHODS

We determined whether cytomegalovirus (CMV) and herpes simplex virus 1 (HSV-1) seropositivity were associated with cognitive impairment among children (aged 6-16 years) and adults aged 20-59 or ≥60 years, using data from the National Health and Nutrition Examination Survey (NHANES) III. Linear and logistic regression models were used to examine the associations between pathogen seropositivity and cognitive impairment.

RESULTS

Among children, HSV-1 seropositivity was associated with lower reading and spatial reasoning test scores (β, -0.69; 95% confidence interval [CI], -1.18 to -.21 and β, -0.82; 95% CI, -1.29 to -.36, respectively). Among middle-aged adults, HSV-1 and CMV seropositivity were associated with impaired coding speed (odds ratio [OR], 1.54; 95% CI, 1.13-2.11, and OR, 1.41; 95% CI, 1.09-1.82, respectively). CMV seropositivity was also associated with impaired learning and recall (OR, 1.43; 95% CI, 1.14-1.80). Among older adults, HSV-1 seropositivity was associated with immediate memory impairment (OR, 3.26; 95% CI, 1.68-6.32).

CONCLUSIONS

Future studies examining the biological pathways by which herpesviruses influence cognitive impairment across the life course are warranted.

Inflammation and the two-hit hypothesis of schizophrenia

The high societal and individual cost of schizophrenia necessitates finding better, more effective treatment, diagnosis, and prevention strategies. One of the obstacles in this endeavor is the diverse set of etiologies that comprises schizophrenia. A substantial body of evidence has grown over the last few decades to suggest that schizophrenia is a heterogeneous syndrome with overlapping symptoms and etiologies. At the same time, an increasing number of clinical, epidemiological, and experimental studies have shown links between schizophrenia and inflammatory conditions. In this review, we analyze the literature on inflammation and schizophrenia, with a particular focus on comorbidity, biomarkers, and environmental insults. We then identify several mechanisms by which inflammation could influence the development of schizophrenia via the two-hit hypothesis. Lastly, we note the relevance of these findings to clinical applications in the diagnosis, prevention, and treatment of schizophrenia.

The neuroimmunology of schizophrenia

Schizophrenia (SCZ) is a polygenic, multi-factorial disorder and a definitive understanding of its pathophysiology has been lacking since it was first described more than a century ago. The predominant pharmacological approach used to treat SCZ is the use of dopamine receptor antagonists. The fact that many patients remain symptomatic, despite complying with medication regimens, emphasises the need for a more encompassing explanation for both the causes and treatment of SCZ. Recent neuroanatomical, neurobiological, environmental and genetic studies have revived the idea that inflammatory pathways are involved in the pathogenesis of SCZ. These new insights have emerged from multiple lines of evidence, including the levels of inflammatory proteins in the central nervous system of patients with SCZ and animal models. This review focuses on aberrant inflammatory mechanisms present both before and during the onset of the psychotic symptoms that characterise SCZ and discusses recent research into adjunctive immune system modulating therapies for its more effective treatment.

Exposure to herpes simplex virus, type 1 and reduced cognitive function

Herpes simplex virus, type 1 (HSV-1) causes cold sores, keratitis and rarely, fatal encephalitis. The infection is lifelong, with sensory ganglia serving as reservoirs of latent infection. Recently, exposure to HSV-1 has also been repeatedly associated with reduced cognitive function among healthy individuals without prior encephalitis. Though HSV-1 does not elevate risk for schizophrenia (SZ) per se, exposure is likewise associated with impaired cognitive functions among SZ patients. The range of cognitive changes observed in HSV-1 exposed persons has not been investigated systematically, nor is it known whether interaction between HSV-1 exposure and SZ related factors contributes to the impairment among SZ patients. Persons with or without schizophrenia/schizophreniform disorder (N = 298 total, DSM IV criteria) were assessed for HSV-1 exposure using serum HSV-1 antibody titers. The Penn Computerized Neurocognitive battery was used to assess eight cognitive domains with respect to accuracy and speed. There were no significant case-control differences in HSV-1 exposure. The SZ/schizophreniform disorder cases were significantly impaired in all cognitive domains compared with the controls. HSV-1 exposure was also associated with reduced cognitive function in the entire sample, but the magnitude of the effects and their patterns differed from the SZ related changes. Further, statistically significant interactions between HSV-1 exposure and SZ case status were not detected. HSV-1 exposure does not elevate risk for SZ, but it is associated with reduced function in specific cognitive domains regardless of SZ diagnostic status. An 'epidiagnostic' model for the association is proposed to explain the results.

Antiherpes virus-specific treatment and cognition in schizophrenia: a test-of-concept randomized double-blind placebo-controlled trial

OBJECTIVE

To test our hypothesis that valacyclovir, an antiherpes virus-specific medication, added to antipsychotics (APs) would improve cognitive performance and psychopathology among schizophrenia subjects exposed to neurotropic herpes simplex virus, type 1 (HSV1).

METHODS

Using a double-blind placebo-controlled design, we randomized 24 HSV1-seropositive schizophrenia subjects to receive either valacyclovir (n = 12) or placebo (n = 12) for 18 weeks in addition to stable doses of APs. Valacyclovir dose was stabilized at 1.5 g twice daily orally. At each visit, subjects were evaluated for severity of psychopathology and side effects using standardized scales and a study-specific semistructured checklist. A computerized neurocognitive battery validated on both schizophrenia and healthy subjects was administered at baseline and follow-up. Intent-to-treat analysis, using linear regression models that included all randomized subjects, were used to examine differential changes in cognition and psychopathology scores over 18 weeks between valacyclovir and placebo, accounting for placebo response.

RESULTS

Valacyclovir group improved in verbal memory, working memory, and visual object learning compared with placebo group. The effect sizes (Cohen's d) were 0.79 for working memory, 1.14 for immediate verbal memory, and 0.97 for the visual object learning. Psychotic symptom severity did not improve.

CONCLUSIONS

Supplemental valacyclovir may alleviate impairments in cognitive domains that are often observed in schizophrenia but not psychotic symptoms in those exposed to HSV1. If replicated, this approach could provide a novel strategy to treat cognitive impairments in a subgroup of schizophrenia subjects who can be reliably identified using a blood test.

Persistent infection with neurotropic herpes viruses and cognitive impairment

BACKGROUND

Herpes virus infections can cause cognitive impairment during and after acute encephalitis. Although chronic, latent/persistent infection is considered to be relatively benign, some studies have documented cognitive impairment in exposed persons that is untraceable to encephalitis. These studies were conducted among schizophrenia (SZ) patients or older community dwellers, among whom it is difficult to control for the effects of co-morbid illness and medications. To determine whether the associations can be generalized to other groups, we examined a large sample of younger control individuals, SZ patients and their non-psychotic relatives (n=1852). Method Using multivariate models, cognitive performance was evaluated in relation to exposures to herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2) and cytomegalovirus (CMV), controlling for familial and diagnostic status and sociodemographic variables, including occupation and educational status. Composite cognitive measures were derived from nine cognitive domains using principal components of heritability (PCH). Exposure was indexed by antibodies to viral antigens.

RESULTS

PCH1, the most heritable component of cognitive performance, declines with exposure to CMV or HSV-1 regardless of case/relative/control group status (p = 1.09 × 10-5 and 0.01 respectively), with stronger association with exposure to multiple herpes viruses (β = -0.25, p = 7.28 × 10-10). There were no significant interactions between exposure and group status.

CONCLUSIONS

Latent/persistent herpes virus infections can be associated with cognitive impairments regardless of other health status.

Exposure to herpes simplex virus type 1 and cognitive impairments in individuals with schizophrenia

Latent infection with neurotropic herpes viruses, such as herpes simplex virus, type 1 (HSV1), has been generally considered benign in most immunocompetent individuals except for rare cases of encephalitis. However, several recent studies have shown impaired cognitive functions among individuals with schizophrenia exposed to HSV1 compared with schizophrenia patients not exposed to HSV1. Such impairments are robust and are prominently observed in working memory, verbal memory, and executive functions. Brain regions that play a key role in the regulation of these domains have shown smaller volumes, along with correlation between these morphometric changes and cognitive impairments in schizophrenia. One study noted temporal decline in executive function and gray matter loss among HSV1-exposed first-episode antipsychotic-naïve schizophrenia patients. Furthermore, a proof-of-concept double-blind placebo-controlled trial indicated improvement in cognitive performance following supplemental anti-herpes-specific medication among HSV1 seropositive schizophrenia patients. Cross-sectional studies have also identified an association between HSV1 exposure and lesser degrees of cognitive impairment among healthy control individuals and patients with bipolar disorder. These studies fulfill several Bradford-Hill criteria, suggesting etiological links between HSV1 exposure and cognitive impairment. Exposure to other human herpes viruses such as cytomegalovirus and herpes simplex virus type 2 (HSV2) may also be associated with cognitive impairment, but the data are less consistent. These studies are reviewed critically and further lines of enquiry recommended. The results are important from a public health perspective, as HSV1 exposure is highly prevalent in many populations.

Infectious agents associated with schizophrenia: a meta-analysis

Schizophrenia is a highly disabling and limiting disorder for patients and the possibility that infections by some microorganisms may be associated to its development may allow prevention and recovery. In the current study we have done a meta-analysis of studies that have assessed the possible association between detection of different infectious agents and schizophrenia. We report results that support the idea that there is a statistically significant association between schizophrenia and infection by Human Herpesvirus 2 (OR=1.34; CI 95%: 1.09-1.70; p=0.05), Borna Disease Virus (OR=2.03; CI 95%: 1.35-3.06; p<0.01), Human Endogenous Retrovirus W (OR=19.31; CI 95%: 6.74-55.29; p<0.001), Chlamydophila pneumoniae (OR=6.34; CI 95%: 2.83-14.19; p<0.001), Chlamydophila psittaci (OR=29.05; CI 95%: 8.91-94.70; p<0.001) and Toxoplasma gondii (OR=2.70; CI 95%: 1.34-4.42; p=0.005). The implications of these findings are discussed and further research options are also explicated.

Structural abnormalities in the cuneus associated with Herpes Simplex Virus (type 1) infection in people at ultra high risk of developing psychosis

It has been suggested that some cases of schizophrenia may be caused by an interaction between physiological risk factors and exposure to certain neurotropic infectious agents such as Herpes Simplex Virus type 1 (HSV1). This study investigated whether HSV1 exposure was associated with structural brain abnormalities in individuals who, because of genetic or other factors, were deemed at ultra high risk (UHR) of developing psychosis. Twenty-five UHR individuals with a history of HSV1 exposure (HSV1+), 33 UHR participants without a history of HSV1 exposure (HSV1-) and 19 healthy controls participated in the study. All participants underwent a T1-weighted structural MRI scan, and HSV1 exposure was determined based on the presence of IgG class antibodies in the blood serum. Voxel based morphometry revealed that the HSV1+ participants exhibited volumetric gray matter reductions in the cuneus, relative to both the HSV1--and healthy control participants (p<0.05, small volume corrected for familywise error). The results of the study suggest that a history of HSV1 infection is associated with volumetric gray matter reductions in individuals at ultra-high risk for developing psychosis, and are consistent with previous studies that have identified structural gray matter abnormalities in HSV1-infected patients with established schizophrenia.

Classification of schizophrenia using feature-based morphometry

The objective of this study was to use a combined local descriptor, namely scale invariance feature transform (SIFT), and a non linear support vector machine (SVM) technique to automatically classify patients with schizophrenia. The dorsolateral prefrontal cortex (DLPFC), considered a reliable neuroanatomical marker of the disease, was chosen as region of interest (ROI). Fifty-four schizophrenia patients and 54 age- and gender-matched normal controls were studied with a 1.5T MRI (slice thickness 1.25 mm). Three steps were conducted: (1) landmark detection and description of the DLPFC, (2) feature vocabulary construction and Bag-of-Words (BoW) computation for brain representation, (3) SVM classification which adopted the local kernel to implicitly implement the feature matching. Moreover, a new weighting approach was proposed to take into account the discriminant relevance of the detected groups of features. Substantial results were obtained for the classification of the whole dataset (left side 75%, right side 66.38%). The performances were higher when females (left side 84.09%, right side 77.27%) and seniors (left side 81.25%, right side 70.83%) were considered separately. In general, the supervised weighed functions increased the efficacy in all the analyses. No effects of age, gender, antipsychotic treatment and chronicity were shown on DLPFC volumes. This integrated innovative ROI-SVM approach allows to reliably detect subjects with schizophrenia, based on a structural brain marker for the disease such as the DLPFC. Such classification should be performed in first-episode patients in future studies, by considering males and females separately.

Progressive gray matter loss and changes in cognitive functioning associated with exposure to herpes simplex virus 1 in schizophrenia: a longitudinal study

OBJECTIVE

Longitudinal changes in gray matter volume and cognitive performance were evaluated among individuals exposed to neurotropic herpes simplex virus subtype 1 (HSV1). There is a replicable association of HSV1 exposure with smaller prefrontal volumes and cognitive impairments in schizophrenia.

METHOD

The authors concurrently examined the whole-brain longitudinal trajectory over 1 year of gray matter volumes and executive functioning measured with the Wisconsin Card Sorting Test among 26 first-episode antipsychotic-naive subjects with schizophrenia and 38 healthy subjects. Age, gender, socioeconomic status, and exposure to cytomegalovirus (another virus of the herpes family that was previously associated with cognitive impairments) were the covariates.

RESULTS

Significant gray matter loss in the posterior cingulate gyrus was noted among the HSV1-seropositive schizophrenia subjects over 1 year but not among other groups. Prefrontal gray matter volumes did not show longitudinal changes. Binomial mixed-effects models indicated that improvement over 1 year in Wisconsin Card Sorting Test categories completed and perseverative errors occurred in significantly fewer HSV1-seropositive schizophrenia subjects than in the HSV1-seronegative schizophrenia subjects or the healthy subjects regardless of serological status. Three-way interactions of diagnosis, HSV1 status, and time were significant for both categories completed and perseverative errors. An increase in perseverative errors over 1 year, but not the change in the number of categories completed, correlated with longitudinal volume loss of the posterior cingulate gyrus.

CONCLUSIONS

These observations suggest that HSV1 exposure may be associated with longitudinal gray matter loss in the posterior cingulate gyrus and decline in executive functioning among subjects with schizophrenia.

Serological evidence of exposure to Herpes Simplex Virus type 1 is associated with cognitive deficits in the CATIE schizophrenia sample

Cognitive impairment is a core feature of schizophrenia. Previous studies have indicated that exposure to neurotropic infectious agents such as Herpes Simplex Virus type 1 may contribute to cognitive deficits and neuroanatomical abnormalities in individuals with schizophrenia. We examined the association between exposure to neurotropic infectious agents and cognitive function in 1308 participants in the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) trial. This sample included all of the individuals in the CATIE trial for whom baseline blood samples were available. Cognition was evaluated at baseline by a test battery which yielded composite scores in the domains of processing speed, verbal memory, vigilance, reasoning, and working memory as well as a summary neurocognitive score. Solid phase immunoassay techniques were used to measure IgG class antibodies to Herpes Simplex Virus type 1 (HSV-1), Herpes Simplex Virus type 2 (HSV-2), Cytomegalovirus (CMV), and to Toxoplasma gondii (T gondii) in the sera of the study individuals. We found a significant association between the neurocognitive summary score and antibodies to HSV-1 but not to HSV-2, CMV, or T. gondii. There was also a significant association between HSV-1 exposure and the Verbal Memory, Vigilance, and Processing Speed composite scores. HSV-1 may modulate the neurocognitive function of individuals with schizophrenia through its ability to establish latency in the central nervous system and undergo periodic reactivation. A better understanding of the role of HSV-1 may lead to better methods of treatment for the cognitive impairments associated with schizophrenia.

Brain anatomical abnormalities in high-risk individuals, first-episode, and chronic schizophrenia: an activation likelihood estimation meta-analysis of illness progression

OBJECTIVE

The present study reviewed voxel-based morphometry (VBM) studies on high-risk individuals with schizophrenia, patients experiencing their first-episode schizophrenia (FES), and those with chronic schizophrenia. We predicted that gray matter abnormalities would show progressive changes, with most extensive abnormalities in the chronic group relative to FES and least in the high-risk group.

METHOD

Forty-one VBM studies were reviewed. Eight high-risk studies, 14 FES studies, and 19 chronic studies were analyzed using anatomical likelihood estimation meta-analysis.

RESULTS

Less gray matter in the high-risk group relative to controls was observed in anterior cingulate regions, left amygdala, and right insula. Lower gray matter volumes in FES compared with controls were also found in the anterior cingulate and right insula but not the amygdala. Lower gray matter volumes in the chronic group were most extensive, incorporating similar regions to those found in FES and high-risk groups but extending to superior temporal gyri, thalamus, posterior cingulate, and parahippocampal gryus. Subtraction analysis revealed less frontotemporal, striatal, and cerebellar gray matter in FES than the high-risk group; the high-risk group had less gray matter in left subcallosal gyrus, left amygdala, and left inferior frontal gyrus compared with FES. Subtraction analysis confirmed lower gray matter volumes through ventral-dorsal anterior cingulate, right insula, left amygdala and thalamus in chronic schizophrenia relative to FES.

CONCLUSIONS

Frontotemporal brain structural abnormalities are evident in nonpsychotic individuals at high risk of developing schizophrenia. The present meta-analysis indicates that these gray matter abnormalities become more extensive through first-episode and chronic illness. Thus, schizophrenia appears to be a progressive cortico-striato-thalamic loop disorder.

Gray matter in first-episode schizophrenia before and after antipsychotic drug treatment. Anatomical likelihood estimation meta-analyses with sample size weighting

BACKGROUND

Cerebral morphological abnormalities in schizophrenia may be modulated by treatment, chronicity, and duration of illness. Comparing brain imaging studies of individuals with first-episode schizophrenia and neuroleptic naive (NN-FES) with that of their neuroleptic-treated counterparts (NT-FES) can help to dissect out the effect of these potential confounders.

METHODS

We used the anatomical likelihood estimation method to compare voxel-based morphometric studies of NN-FES (n = 162 patients) and NT-FES (n = 336 patients) studies. The analysis included a sample size weighting step based on the Liptak-Stouffer method to reflect the greater power of larger studies.

RESULTS

Patient samples were matched for age, gender, and duration of illness. An extensive network of gray matter deficits in frontal, temporal, insular, striatal, posterior cingulate, and cerebellar regions was detected in the NN-FES samples as compared with healthy controls. Major deficits were detected in the frontal, superior temporal, insular, and parahippocampal regions for the NT-FES group compared with the NN-FES group. In addition, the NT-FES group showed minor deficits in the caudate, cingulate, and inferior temporal regions compared with the NN-FES group. There were no regions with gray matter volumetric excess in the NT-FES group.

CONCLUSION

Frontal, striato-limbic, and temporal morphological abnormalities are present in the early stage of schizophrenia and are unrelated to the effects of neuroleptic treatment, chronicity, and duration of illness. There may be dynamic effects of treatment on striato-limbic and temporal, but not frontal, regional gray matter volumes of the brain.

Are Bipolar Disorder and Schizophrenia Neuroanatomically Distinct? An Anatomical Likelihood Meta-analysis

Objective: There is renewed debate on whether modern diagnostic classification should adopt a dichotomous or dimensional approach to schizophrenia and bipolar disorder. This study synthesizes data from voxel-based studies of schizophrenia and bipolar disorder to estimate the extent to which these conditions have a common neuroanatomical phenotype. Methods: A post-hoc meta-analytic estimation of the extent to which bipolar disorder, schizophrenia, or both conditions contribute to brain gray matter differences compared to controls was achieved using a novel application of the conventional anatomical likelihood estimation (ALE) method. 19 schizophrenia studies (651 patients and 693 controls) were matched as closely as possible to 19 bipolar studies (540 patients and 745 controls). Result: Substantial overlaps in the regions affected by schizophrenia and bipolar disorder included regions in prefrontal cortex, thalamus, left caudate, left medial temporal lobe, and right insula. Bipolar disorder and schizophrenia jointly contributed to clusters in the right hemisphere, but schizophrenia was almost exclusively associated with additional gray matter deficits (left insula and amygdala) in the left hemisphere. Limitation: The current meta-analytic method has a number of constraints. Importantly, only studies identifying differences between controls and patient groups could be included in this analysis. Conclusion: Bipolar disorder shares many of the same brain regions as schizophrenia. However, relative to neurotypical controls, lower gray matter volume in schizophrenia is more extensive and includes the amygdala. This fresh application of ALE accommodates multiple studies in a relatively unbiased comparison. Common biological mechanisms may explain the neuroanatomical overlap between these major disorders, but explaining why brain differences are more extensive in schizophrenia remains challenging.

Grey matter changes associated with host genetic variation and exposure to Herpes Simplex Virus 1 (HSV1) in first episode schizophrenia

BACKGROUND

We previously reported reduced prefrontal cortex (PFC) grey matter volume among first episode, antipsychotic-naïve schizophrenia subjects (SZ) exposed to HSV1 but not among healthy subjects (HS) (Prasad et al., 2007). Independently, rs1051788, an exonic polymorphism of the MHC Class I polypeptide-related sequence B (MICB) gene was associated with HSV1 seropositivity, as well as SZ risk. In this study, we examined whether PFC grey matter changes associated with HSV1 exposure varied against the background of MICB genotypes.

METHODS

We examined Caucasian individuals from the sample we studied in our previous report (Prasad et al., 2007) (SZ, n=21 and HS, n=19). Whole brain voxelwise analysis of structural MRI scans was conducted using Statistical Parametric Mapping, ver 5 (SPM5). The impact of rs1051788 variation and HSV1 seropositivity on grey matter volumes was examined using regression models on the combined sample of cases and controls, and then within each diagnostic group.

RESULTS

In the combined sample of cases and controls, we observed the main effects of HSV1 seropositivity and genotypes, and a significant joint effect of HSV1 seropositivity and genotype mainly in the PFC. The joint effect was more prominent among cases than among controls.

DISCUSSION

Our observations suggest that rs1051788 and HSV1 seropositivity are associated individually and jointly with reduced PFC grey matter volume. The patterns of these associations differ by diagnostic status, and these factors explain only a "small" portion of the variance in the grey matter volume reductions.

Neuroanatomic and cognitive abnormalities related to herpes simplex virus type 1 in schizophrenia

Herpes simplex virus 1 (HSV-1) tends to replicate in the temporal cortex and can damage the limbic system. The presence of serum antibodies to HSV-1 is associated with cognitive impairment in adults with schizophrenia, suggesting that cerebral gray matter abnormalities might distinguish patient subgroups defined by HSV-1 exposure. We assessed 43 adult outpatients with schizophrenia. The assessment included clinical interviews, neurocognitive testing, anatomic brain magnetic resonance imaging and measures of serum IgG antibodies specific to herpes simplex viruses 1 and 2. We then compared 25 patients who tested positive for antibodies to HSV-1 with 15 who were seronegative for both HSV-1 and HSV-2. The seropositive patients performed significantly worse than the seronegative patients on four neuropsychological measures of psychomotor speed, executive functioning, and explicit verbal memory. Voxel-based morphometric analyses revealed that the same patients showed reduced gray matter volume in the anterior cingulate and areas of the cerebellum. Finally, performance on the test of psychomotor speed and executive functioning that showed the largest between- group effect size correlated with reduced gray matter volume in some of the same brain regions (cingulate and cerebellum) that distinguished the two HSV-1 subgroups. In these outpatients with schizophrenia, HSV-1 seropositivity and performance on a cognitive test that is highly sensitive to it co-localize to closely overlapping brain regions.

Schizophrenia susceptibility genes directly implicated in the life cycles of pathogens: cytomegalovirus, influenza, herpes simplex, rubella, and Toxoplasma gondii

Many genes implicated in schizophrenia can be related to glutamatergic transmission and neuroplasticity, oligodendrocyte function, and other families clearly related to neurobiology and schizophrenia phenotypes. Others appear rather to be involved in the life cycles of the pathogens implicated in the disease. For example, aspartylglucosaminidase (AGA), PLA2, SIAT8B, GALNT7, or B3GAT1 metabolize chemical ligands to which the influenza virus, herpes simplex, cytomegalovirus (CMV), rubella, or Toxoplasma gondii bind. The epidermal growth factor receptor (EGR/EGFR) is used by the CMV to gain entry to cells, and a CMV gene codes for an interleukin (IL-10) mimic that binds the host cognate receptor, IL10R. The fibroblast growth factor receptor (FGFR1) is used by herpes simplex. KPNA3 and RANBP5 control the nuclear import of the influenza virus. Disrupted in schizophrenia 1 (DISC1) controls the microtubule network that is used by viruses as a route to the nucleus, while DTNBP1, MUTED, and BLOC1S3 regulate endosomal to lysosomal routing that is also important in viral traffic. Neuregulin 1 activates ERBB receptors releasing a factor, EBP1, known to inhibit the influenza virus transcriptase. Other viral or bacterial components bind to genes or proteins encoded by CALR, FEZ1, FYN, HSPA1B, IL2, HTR2A, KPNA3, MED12, MED15, MICB, NQO2, PAX6, PIK3C3, RANBP5, or TP53, while the cerebral infectivity of the herpes simplex virus is modified by Apolipoprotein E (APOE). Genes encoding for proteins related to the innate immune response, including cytokine related (CCR5, CSF2RA, CSF2RB, IL1B, IL1RN, IL2, IL3, IL3RA, IL4, IL10, IL10RA, IL18RAP, lymphotoxin-alpha, tumor necrosis factor alpha [TNF]), human leukocyte antigen (HLA) antigens (HLA-A10, HLA-B, HLA-DRB1), and genes involved in antigen processing (angiotensin-converting enzyme and tripeptidyl peptidase 2) are all concerned with defense against invading pathogens. Human microRNAs (Hsa-mir-198 and Hsa-mir-206) are predicted to bind to influenza, rubella, or poliovirus genes. Certain genes associated with schizophrenia, including those also concerned with neurophysiology, are intimately related to the life cycles of the pathogens implicated in the disease. Several genes may affect pathogen virulence, while the pathogens in turn may affect genes and processes relevant to the neurophysiology of schizophrenia. For such genes, the strength of association in genetic studies is likely to be conditioned by the presence of the pathogen, which varies in different populations at different times, a factor that may explain the heterogeneity that plagues such studies. This scenario also suggests that drugs or vaccines designed to eliminate the pathogens that so clearly interact with schizophrenia susceptibility genes could have a dramatic effect on the incidence of the disease.

A possible relationship between Toxoplasma gondii and schizophrenia: A seroprevalence study

Objective. Schizophrenia is a pervasive neuropsychiatric disease of uncertain etiology. We aimed to investigate a possible association between Toxoplasma gondii infection and schizophrenia in this study. Method. We selected individuals with schizophrenia (n=88) and tested them with commercially available enzyme-linked immunosorbent assay (ELISA) for anti-Toxoplasma IgG and IgM antibodies and compared these seropositivity rate to those of controls without psychiatric disease (n=88). Results. The rate of IgG antibody in the schizophrenia patients (47.7%) was higher than the control groups (20.4%) (P<0.001). We did not find any anti-Toxoplasma IgM seropositivity in both schizophrenia patients and control group. In schizophrenic patients with and without anti-Toxoplasma IgG groups statistical analysis did not reveal any correlation between demographic variables and Toxoplasma infection. Conclusion. Our findings supported previous studies indicate that T.gondii may play a role in etiopathogenesis in some cases of schizophrenia.

Antibodies to cytomegalovirus and Herpes Simplex Virus 1 associated with cognitive function in schizophrenia

BACKGROUND

Cognitive impairment in the form of decreased working memory and executive functions has been recognized as a key deficit in schizophrenia. Neurotropic viruses have been associated with focal gray matter deficits in patients with schizophrenia. We evaluated whether such agents alter cognitive function in schizophrenia.

METHODS

The sample consisted of 329 patients diagnosed with schizophrenia or schizoaffective disorder. We evaluated associations between exposure to selected agents (Herpes Simplex Viruses 1 and 2 (HSV1, HSV2 respectively) cytomegalovirus (CMV) and Toxoplasma gondii) and scores on the Trail Making Test (TMT), controlling for relevant variables.

RESULTS

Serological evidence of exposure to CMV was associated with impaired performance on TMT part A time to completion (p=0.044), a measure of visual search, working memory, and psychomotor speed. Both CMV and HSV1 were significantly associated with increased errors on TMT part B (p<0.001 for both viruses). HSV2 and T. gondii exposure measures were not associated with any of the cognitive functions evaluated using TMT.

CONCLUSIONS

Both CMV and HSV1 are associated with impaired cognitive function in schizophrenia as measured by the TMT. Further analyses to evaluate the impact of other illness related variables including genetic variants are warranted.

Results from a hypothesis generating case-control study: herpes family viruses and schizophrenia among military personnel

BACKGROUND

Herpes family viruses can cause central nervous system inflammatory changes that can present with symptoms indistinguishable from schizophrenia and therefore are of interest in schizophrenia research. Most existing studies of herpes viruses have used small populations and postdiagnosis specimens. As part of a larger research program, we conducted a hypothesis-generating case-control study of selected herpes virus antibodies among individuals discharged from the US military with schizophrenia and pre- and postdiagnosis sera.

METHODS

Cases (n = 180) were servicemembers hospitalized and discharged from military service with schizophrenia. Controls, 3:1 matched on several factors, were members not discharged. The military routinely collects and stores members' serum specimens. We used microplate enzyme immunoassay to measure immunoglobulin G (IgG) antibody levels to 6 herpes viruses in pre- and postdiagnosis specimens. Conditional logistic regression was used, and the measure of association was the hazard ratio (HR).

RESULTS

Overall, we found a significant association between human herpes virus type 6 and schizophrenia, with an HR of 1.17 (95% confidence interval [CI] = 1.04, 1.32). Women and blacks had significant negative associations with herpes simplex virus type 2 and cytomegalovirus; among blacks, there was a significant positive association with herpes simplex virus type 1. Among men, there was a HHV-6 temporal effect with an HR of 1.41 (95% CI = 1.02, 1.96) for sera drawn 6-12 months before diagnosis.

DISCUSSION

Findings from previous studies of herpes family viruses and schizophrenia have been inconsistent. Our study is based on a larger population than most previous studies and used serum specimens collected before onset of illness. This study adds to the body of knowledge and provides testable hypotheses for follow-on studies.

Problems and promise of immunological factors as biomarkers for schizophrenia

The complex and multifactorial etiology of psychiatric disorders, and in particular that of schizophrenia, has made it difficult to identify biomarkers suitable for clinical diagnosis. In schizophrenia research, the investigation of immune-related factors has been of central importance in the quest to unravel the disease etiology. However, immunological findings have been controversial, and the importance of an underlying immunopathology in schizophrenia remains to be irrevocably established. Here we review those findings that have been most consistently reported. We further address their potential utility for clinical diagnosis and drug development. We also discuss problems connected to sample collection and preparation, with special focus on their effects on immune-derived parameters. In light of recent findings, we highlight the potential of combining functional cell-based assays with high-throughput multiomics experiments for the discovery of novel biomarkers.

Structural cerebral variations as useful endophenotypes in schizophrenia: do they help construct "extended endophenotypes"?

Endophenotypes represent intermediate phenotypes on the putative causal pathway from the genotype to the phenotype. They offer a potentially valuable strategy to examine the molecular etiopathology of complex behavioral phenotypes such as schizophrenia. Neurocognitive and neurophysiological impairments that suggest functional impairments associated with schizophrenia have been proposed as endophenotypes. However, few studies have examined the structural variations in the brain that might underlie the functional impairments as useful endophenotypes for schizophrenia. Over the past three decades, there has been an impressive body of literature supporting brain structural alterations in schizophrenia. We critically reviewed the extant literature on the neuroanatomical variations in schizophrenia in this paper to evaluate their candidacy as endophenotypes and how useful they are in furthering the understanding of etiology and pathophysiology of schizophrenia. Brain morphometric measures meet many of the criteria set by different investigators, such as being robustly associated with schizophrenia, heritable, quantifiable, and present in unaffected family members more frequently than in the general population. We conclude that the brain morphometric alterations appear largely to meet the criteria for endophenotypes in psychotic disorders. Some caveats for the utility of endophenotypes are discussed. A proposal to combine more than one endophenotype ("extended endophenotype") is suggested. Further work is needed to examine how specific genes and their interactions with the environment may produce alterations in brain structure and function that accompany psychotic disorders.

Systematic association studies of mitochondrial DNA variations in schizophrenia: focus on the ND5 gene

Postmortem studies, as well as genetic association studies, have implicated mitochondrial dysfunction in schizophrenia (SZ). We conducted multistaged analysis to assess the involvement of mitochondrial DNA (mtDNA) variations in SZ. Initially, the entire mtDNA genome was sequenced in pools of DNA from SZ cases and controls (n = 180 in each group, set 1). Two polymorphisms localized to the NADH dehydrogenase subunit 5 (ND5) gene demonstrated suggestive case control allele frequency differences (mtDNA 13368 G/A, p = .019 and mtDNA 13708G/A, p = .043). Hence, the ND5 gene was sequenced in individual samples from the initial panel of cases and controls. Additional subjects from another independent set of cases and controls (set 2, cases, n = 244, controls n = 508) were also sequenced individually. No significant differences in allele frequencies for mtDNA 13368 G/A, and mtDNA 13708G/A were observed. However, we identified 216 other rare variants, 53 of which were reported earlier in association studies of other mitochondrial disorders. We compared the distribution of polymorphisms in both sets of cases and controls. No significant case-control differences were observed in the smaller, first set. In the second set, cases had more variants overall (p = 0.014), as well as synonymous variants (p = 0.02), but the difference for nonsynonymous variants was not significant (p = 0.19). Screening available first-degree relatives (n = 10) revealed 10 maternally inherited variations, suggesting that not all the variants are somatic mutations. Further investigations are warranted.

Polymorphisms in MICB are associated with human herpes virus seropositivity and schizophrenia risk

Viral infection may be a risk factor for schizophrenia and has been associated with decreased cognitive functioning in patients. We report associations of SNPs at MICB (MHC class I polypeptide-related sequence B, chromosome 6p21) with cytomegalovirus and herpes simplex virus 1 seropositivity. We previously found associations with schizophrenia on chromosome 6p21 among patients seropositive for cytomegalovirus (CMV) and herpes simplex virus 1 (HSV1). To localize the associations further, we genotyped 26 SNPs spanning 100 kb in a sample of 236 Caucasian schizophrenia patients and 240 controls. Based on suggestive associations, we selected five SNPs at MICB to assay among two additional Caucasian samples that had been serotyped for CMV and HSV1: a case-control sample recruited in Baltimore (n=272 cases, 108 controls), and a case-parent trio sample recruited in Pittsburgh (n=221). Among Baltimore control individuals there were significant associations with antibody status for infectious agents: rs1051788 with HSV1 seropositivity (p=0.006) and rs2523651 with cytomegalovirus seropositivity (p=0.001). The former association was also detectable among the parents of cases recruited in Pittsburgh (p=0.024). Neither viral association was noted among the schizophrenia cases. With respect to schizophrenia risk, significant transmission distortion was noted at rs1051788 and rs1055569 among the case-parent trios regardless of antibody status (p=0.014 and 0.036 respectively). A similar trend for association with schizophrenia liability at rs1051788 in the Baltimore sample did not attain statistical significance. There are a number of explanations for the associations, including chance variation, as well as gene-virus interactions. Further replicate studies are warranted, as are functional studies of these polymorphisms.