Oligodendrocyte dysfunction in schizophrenia and bipolar disorder

BACKGROUND

Results of array studies have suggested abnormalities in expression of lipid and myelin-related genes in schizophrenia. Here, we investigated oligodendrocyte-specific and myelination-associated gene expression in schizophrenia and bipolar affective disorder.

METHODS

We used samples from the Stanley brain collection, consisting of 15 schizophrenia, 15 bipolar affective disorder, and 15 control brains. Indexing-based differential display PCR was done to screen for differences in gene expression in schizophrenia patients versus controls. Results were cross-validated with quantitative PCR, which was also used to investigate expression profiles of 16 other oligodendrocyte and myelin genes in schizophrenia and bipolar disorder. These genes were further investigated with an ongoing microarray analysis.

FINDINGS

Results of differential display and quantitative PCR analysis showed a reduction of key oligodendrocyte-related and myelin-related genes in schizophrenia and bipolar patients; expression changes for both disorders showed a high degree of overlap. Microarray results of the same genes investigated by quantitative PCR correlated well overall.

INTERPRETATION

Schizophrenia and bipolar brains showed downregulation of key oligodendrocyte and myelination genes, including transcription factors that regulate these genes, compared with control brains. These results lend support to and extend observations from other microarray investigations. Our study also showed similar expression changes to the schizophrenia group in bipolar brains, which thus lends support to the notion that the disorders share common causative and pathophysiological pathways.

Feeding of Bifidobacterium bifidum and Streptococcus thermophilus to infants in hospital for prevention of diarrhoea and shedding of rotavirus

Acute diarrhoea is a serious cause of infant morbidity and mortality, and the development of preventive measures remains an important goal. Bifidobacteria (which constitute the predominant intestinal flora of breastfed infants), as well as other lactic-acid-producing organisms such as Streptococcus thermophilus, are thought to have a protective effect against acute diarrhoeal disease. However, their efficacy has not been assessed in controlled trials. In a double-blind, placebo-controlled trial, infants aged 5-24 months who were admitted to a chronic medical care hospital were randomised to receive a standard infant formula or the same formula supplemented with Bifidobacterium bifidum and S thermophilus. Patients were evaluated daily for occurrence of diarrhoea, and faecal samples, obtained weekly, were analysed for rotavirus antigen by enzyme immunoassay. Faecal samples were also obtained during an episode of diarrhoea for virological and bacteriological analyses. 55 subjects were evaluated for a total of 4447 patient-days during 17 months. 8 (31%) of the 26 patients who received the control formula and 2 (7%) of 29 who received the supplemented formula developed diarrhoea during the course of the study (p = 0.035, Fisher's exact test, two-tailed). 10 (39%) of the subjects who received the control formula and 3 (10%) of those who received the supplemented formula shed rotavirus at some time during the study (p = 0.025). The supplementation of infant formula with B bifidum and S thermophilus can reduce the incidence of acute diarrhoea and rotavirus shedding in infants admitted to hospital.

Mitochondrial dysfunction in schizophrenia: evidence for compromised brain metabolism and oxidative stress

The etiology and pathophysiology of schizophrenia remain unknown. A parallel transcriptomics, proteomics and metabolomics approach was employed on human brain tissue to explore the molecular disease signatures. Almost half the altered proteins identified by proteomics were associated with mitochondrial function and oxidative stress responses. This was mirrored by transcriptional and metabolite perturbations. Cluster analysis of transcriptional alterations showed that genes related to energy metabolism and oxidative stress differentiated almost 90% of schizophrenia patients from controls, while confounding drug effects could be ruled out. We propose that oxidative stress and the ensuing cellular adaptations are linked to the schizophrenia disease process and hope that this new disease concept may advance the approach to treatment, diagnosis and disease prevention of schizophrenia and related syndromes.

The stanley foundation brain collection and neuropathology consortium

The Stanley Foundation brain collection is an attempt to supplement existing brain collections for the purpose of promoting research on schizophrenia and bipolar disorder. Specimens are collected with the permission of the families in a standardized manner, with half of each specimen being frozen and half fixed in formalin. The Neuropathology Consortium is a subset of 60 specimens from the collection, well-matched groups of 15 each with diagnoses of schizophrenia, bipolar disorder, major depressive disorder without psychotic features, and normal controls. More than 75000 sections and blocks from the Consortium have been sent to over 50 research groups worldwide to carry out a wide variety of assessments. These data will be integrated to provide a more complete picture of the neuropathology of these disorders.

Seasonality of births in schizophrenia and bipolar disorder: a review of the literature

More than 250 studies, covering 29 Northern and five Southern Hemisphere countries, have been published on the birth seasonality of individuals who develop schizophrenia and/or bipolar disorder. Despite methodological problems, the studies are remarkably consistent in showing a 5-8% winter-spring excess of births for both schizophrenia and mania/bipolar disorder. This seasonal birth excess is also found in schizoaffective disorder (December-March), major depression (March-May), and autism (March) but not in other psychiatric conditions with the possible exceptions of eating disorders and antisocial personality disorder. The seasonal birth pattern also may shift over time. Attempts to correlate the seasonal birth excess with specific features of schizophrenia suggest that winter-spring births are probably related to urban births and to a negative family history. Possible correlations include lesser severity of illness and neurophysiological measures. There appears to be no correlation with gender, social class, race, measurable pregnancy and birth complications, clinical subtypes, or neurological, neuropsychological, or neuroimaging measures. Virtually no correlation studies have been done for bipolar disorder. Regarding the cause of the birth seasonality, statistical artifact and parental procreational habits are unlikely explanations. Seasonal effects of genes, subtle pregnancy and birth complications, light and internal chemistry, toxins, nutrition, temperature/weather, and infectious agents or a combination of these are all viable possibilities.

Disease-specific alterations in frontal cortex brain proteins in schizophrenia, bipolar disorder, and major depressive disorder. The Stanley Neuropathology Consortium

Severe psychiatric disorders such as schizophrenia, bipolar disorder and major depressive disorder are brain diseases of unknown origin. No biological marker has been documented at the pathological, cellular, or molecular level, suggesting that a number of complex but subtle changes underlie these illnesses. We have used proteomic technology to survey postmortem tissue to identify changes linked to the various diseases. Proteomics uses two-dimensional gel electrophoresis and mass spectrometric sequencing of proteins to allow the comparison of subsets of expressed proteins among a large number of samples. This form of analysis was combined with a multivariate statistical model to study changes in protein levels in 89 frontal cortices obtained postmortem from individuals with schizophrenia, bipolar disorder, major depressive disorder, and non-psychiatric controls. We identified eight protein species that display disease-specific alterations in level in the frontal cortex. Six show decreases compared with the non-psychiatric controls for one or more diseases. Four of these are forms of glial fibrillary acidic protein (GFAP), one is dihydropyrimidinase-related protein 2, and the sixth is ubiquinone cytochrome c reductase core protein 1. Two spots, carbonic anhydrase 1 and fructose biphosphate aldolase C, show increase in one or more diseases compared to controls. Proteomic analysis may identify novel pathogenic mechanisms of human neuropsychiatric diseases.

Maternal infections and subsequent psychosis among offspring

BACKGROUND

We tested the hypothesis that maternal infections during pregnancy are associated with the subsequent development of schizophrenia and other psychoses in adulthood.

METHODS

We conducted a nested case-control study of 27 adults with schizophrenia and other psychotic illnesses and 54 matched unaffected control subjects (matched for sex, ethnicity, and date of birth) from the Providence, RI, cohort of the Collaborative Perinatal Project. We retrieved stored blood samples that had been obtained from these mothers at the end of pregnancy. These samples were analyzed for total class-specific immunoglobulins and for specific antibodies directed at recognized perinatal pathogens capable of affecting brain development.

RESULTS

Maternal levels of IgG and IgM class immunoglobulins before the mothers were delivered of their neonates were significantly elevated among the case series (t = 3.06, P =.003; t = 2.93, P =.004, respectively, for IgG and IgM immunoglobulin-albumin ratios). Secondary analyses indicated a significant association between maternal antibodies to herpes simplex virus type 2 glycoprotein gG2 and subsequent psychotic illness (matched t test = 2.43, P =.02). We did not find significant differences between case and control mothers in the serum levels of IgA class immunoglobulins, or in specific IgG antibodies to herpes simplex virus type 1, cytomegalovirus, Toxoplasma gondii, rubella virus, human parvovirus B19, Chlamydia trachomatis, or human papillomavirus type 16.

CONCLUSIONS

The offspring of mothers with elevated levels of total IgG and IgM immunoglobulins and antibodies to herpes simplex virus type 2 are at increased risk for the development of schizophrenia and other psychotic illnesses in adulthood.

Antibodies to Toxoplasma gondii in patients with schizophrenia: a meta-analysis

Recent studies have linked infectious agents to schizophrenia. The largest number of studies has involved the analysis of Toxoplasma gondii; these studies were subjected to a meta-analysis. Published articles and abstracts were identified by searches of MEDLINE, Ovid, and Google Scholar; by a search of Chinese publications; through letters to researchers; and by visiting China. Published and unpublished controlled studies that used serological methods for measuring T. gondii antibodies to assess inpatients and/or outpatients diagnosed with schizophrenia were selected for analysis, and source documents were translated as needed. Forty-two studies carried out in 17 countries over 5 decades were identified; 23 of these (6 unpublished) met selection criteria. The combined odds ratio (OR) was 2.73 (95% confidence interval, 2.10 to 3.60; chi-square with 1 df 263; P < .000001). Seven studies that included only patients with first-episode schizophrenia (OR 2.54) did not differ significantly from 16 studies that included patients in all clinical phases (OR 2.79). The results suggest that individuals with schizophrenia have an increased prevalence of antibodies to T. gondii. This association is consistent with other epidemiological studies as well as with animal studies. Although the OR of 2.73 is modest, it exceeds that for genetic or other environmental factors identified to date and suggests that Toxoplasma is in some way associated with a large number of cases of schizophrenia. If an etiological association can be proven, it would have implications for the design of measures for the prevention and treatment of this disease.

Toxoplasma gondii and other risk factors for schizophrenia: an update

The failure to find genes of major effect in schizophrenia has refocused attention on nongenetic, including infectious factors. In a previous study, antibodies to Toxoplasma gondii were found to be elevated in 23 studies of schizophrenia (OR 2.73; 95% CI 2.10-3.60). The current study replicates this finding with 15 additional studies (OR 2.71; 95% CI 1.93-3.80) and compares this with other identified schizophrenia risk factors. The highest risk factors are having an affected mother (relative risks [RR] 9.31; 95% CI 7.24-11.96), father (RR 7.20; 95% CI 5.10-10.16), or sibling (RR 6.99; 95% CI 5.38-9.08) or being the offspring of immigrants from selected countries (RR 4.5; 95% CI 1.5-13.1). Intermediate risk factors, in addition to infection with T. gondii, include being an immigrant from and to selected countries (RR 2.7; 95% CI 2.3-3.2), being born in (RR 2.24; 95% CI 1.92-2.61) or raised in (RR 2.75; 95% CI 2.31-3.28) an urban area, cannabis use (OR 2.10-2.93; 95% CI 1.08-6.13), having minor physical anomalies (OR 2.23; 95% CI 1.42-3.58), or having a father 55 or older (OR 2.21-5.92; 95% CI 1.46-17.02). Low-risk factors include a history of traumatic brain injury (OR 1.65; 95% CI 1.17-2.32), sex abuse in childhood (OR 1.46; 95% CI 0.84-2.52), obstetrical complications (OR 1.29-1.38; 95% CI 1.00-1.84), having a father 45 or older (OR 1.21-1.66; 95% CI 1.09-2.01), specific genetic polymorphisms (OR 1.09-1.24; 95% CI 1.06-1.45), birth seasonality (OR 1.07-1.95; 95% CI 1.05-2.91), maternal exposure to influenza (RR 1.05; 95% CI 0.98-1.12), or prenatal stress (RR 0.98-1.00; 95% CI 0.85-1.16).

Enzyme-linked immunosorbent assay (ELISA) for detection of human reovirus-like agent of infantile gastroenteritis

An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of the human reovirus-like agent of infantile gastroenteritis in human stools. The results of the assay can be read either with a simple colorimeter or the naked eye. Investigations with 143 samples from children with gastroenteritis and 75 samples from children with other illnesses showed that the ELISA was as sensitive as electron microscopy or radioimmunoassay for detection of this agent. In addition, the ELISA was simple to perform and, when read visually, did not require sophisticated technical equipment. These advantages make it suitable for field work.

Human milk mucin inhibits rotavirus replication and prevents experimental gastroenteritis

Acute gastrointestinal infections due to rotaviruses and other enteric pathogens are major causes of morbidity and mortality in infants and young children throughout the world. Breast-feeding can reduce the rate of serious gastroenteritis in infants; however, the degrees of protection offered against rotavirus infection vary in different populations. The mechanisms associated with milk-mediated protection against viral gastroenteritis have not been fully elucidated. We have isolated a macromolecular component of human milk that inhibits the replication of rotaviruses in tissue culture and prevents the development of gastroenteritis in an animal model system. Purification of the component indicates that the antiviral activity is associated with an acidic fraction (pI = 4.0-4.6), which is free of detectable immunoglobulins. Furthermore, high levels of antiviral activity are associated with an affinity-purified complex of human milk mucin. Deglycosylation of the mucin complex results in the loss of antiviral activity. Further purification indicated that rotavirus specifically binds to the milk mucin complex as well as to the 46-kD glycoprotein component of the complex. Binding to the 46-kD component was substantially reduced after chemical hydrolysis of sialic acid. We have documented that human milk mucin can bind to rotavirus and inhibit viral replication in vitro and in vivo. Variations in milk mucin glycoproteins may be associated with different levels of protection against infection with gastrointestinal pathogens.

Retroviral RNA identified in the cerebrospinal fluids and brains of individuals with schizophrenia

Schizophrenia is a serious brain disease of uncertain etiology. A role for retroviruses in the etiopathogenesis of some cases of schizophrenia has been postulated on the basis of clinical and epidemiological observations. We found sequences homologous to retroviral pol genes in the cell-free cerebrospinal fluids (CSFs) of 10 of 35 (29%) individuals with recent-onset schizophrenia or schizoaffective disorder. Retroviral sequences also were identified in the CSFs of 1 of 20 individuals with chronic schizophrenia. However, retroviral sequences were not identified in any of the CSFs obtained from 22 individuals with noninflammatory neurological diseases or from 30 individuals without evidence of neurological or psychiatric diseases (chi(2) = 19.25, P < 0.001). The nucleotide sequences identified in the CSFs of the individuals with schizophrenia or schizoaffective disorder were related to those of the human endogenous retroviral (HERV)-W family of endogenous retroviruses and to other retroviruses in the murine leukemia virus genus. Transcription of RNA homologous to members of the HERV-W family of retroviruses also was found to be up-regulated differentially in the frontal cortex regions of brains obtained postmortem from individuals with schizophrenia, as compared with corresponding tissue from individuals without psychiatric diseases. The transcriptional activation of certain retroviral elements within the central nervous system may be associated with the development of schizophrenia in at least some individuals. The further characterization of retroviral elements within the central nervous system of individuals with schizophrenia might lead to improved methods for the diagnosis and management of this disorder.

Viruses, schizophrenia, and bipolar disorder

The hypothesis that viruses or other infectious agents may cause schizophrenia or bipolar disorder dates to the 19th century but has recently been revived. It could explain many clinical, genetic, and epidemiologic aspects of these diseases, including the winter-spring birth seasonality, regional differences, urban birth, household crowding, having an older sibling, and prenatal exposure to influenza as risk factors. It could also explain observed immunological changes such as abnormalities of lymphocytes, proteins, autoantibodies, and cytokines. However, direct studies of viral infections in individuals with these psychiatric diseases have been predominantly negative. Most studies have examined antibodies in blood or cerebrospinal fluid, and relatively few studies have been done on viral antigens, genomes, cytopathic effect on cell culture, and animal transmission experiments. Viral research on schizophrenia and bipolar disorder is thus comparable to viral research on multiple sclerosis and Parkinson's disease: an attractive hypothesis with scattered interesting findings but no clear proof. The application of molecular biological techniques may allow the identification of novel infectious agents and the associations of these novel agents with serious mental diseases.

Are some cases of psychosis caused by microbial agents? A review of the evidence

The infectious theory of psychosis, prominent early in the twentieth century, has recently received renewed scientific support. Evidence has accumulated that schizophrenia and bipolar disorder are complex diseases in which many predisposing genes interact with one or more environmental agents to cause symptoms. The protozoan Toxoplasma gondii and cytomegalovirus are discussed as examples of infectious agents that have been linked to schizophrenia and in which genes and infectious agents interact. Such infections may occur early in life and are thus consistent with neurodevelopmental as well as genetic theories of psychosis. The outstanding questions regarding infectious theories concern timing and causality. Attempts are underway to address the former by examining sera of individuals prior to the onset of illness and to address the latter by using antiinfective medications to treat individuals with psychosis. The identification of infectious agents associated with the etiopathogenesis of schizophrenia might lead to new methods for the diagnosis, treatment and prevention of this disorder.

Maternal cytokine levels during pregnancy and adult psychosis

We investigated levels of maternal cytokines in late pregnancy in relation to the subsequent development of adult schizophrenia and other psychoses in their offspring. The sample included the mothers of 27 adults with schizophrenia and other psychotic illnesses and 50 matched unaffected controls from the Providence cohort of the Collaborative Perinatal Project. Serum samples were analyzed for interleukin 1 beta (IL-1-beta), interleukin 2 (IL-2), interleukin 6 (IL-6), interleukin 8 (IL-8), and tumor necrosis factor alpha (TNF-alpha) by enzyme immunoassay. Maternal levels of TNF-alpha were significantly elevated among the case series (t = 2.22, p =.04), with evidence of increasing odds of psychosis in relation to higher cytokine levels. We did not find significant differences between case and control mothers in the serum levels of IL-1, IL-2, IL-6, or IL-8. These data support previous clinical investigations reporting maternal infections during pregnancy as a potential risk factor for psychotic illness among offspring.

Toxoplasma gondii and schizophrenia

Recent epidemiologic studies indicate that infectious agents may contribute to some cases of schizophrenia. In animals, infection with Toxoplasma gondii can alter behavior and neurotransmitter function. In humans, acute infection with T. gondii can produce psychotic symptoms similar to those displayed by persons with schizophrenia. Since 1953, a total of 19 studies of T. gondii antibodies in persons with schizophrenia and other severe psychiatric disorders and in controls have been reported; 18 reported a higher percentage of antibodies in the affected persons; in 11 studies the difference was statistically significant. Two other studies found that exposure to cats in childhood was a risk factor for the development of schizophrenia. Some medications used to treat schizophrenia inhibit the replication of T. gondii in cell culture. Establishing the role of T. gondii in the etiopathogenesis of schizophrenia might lead to new medications for its prevention and treatment.

Chronic rotavirus infection in immunodeficiency

The characteristics of rotavirus infection in 23 children with a variety of primary immunodeficiency diseases were studied. Stools and sera were tested for rotavirus by means of the enzyme-linked immunosorbent assay and the enzyme-linked fluorescent assay, respectively. Four immunodeficient patients had diarrhea during the study period and all had rotavirus infection; rotavirus was not detected in the stools of the 19 asymptomatic immunodeficient patients. Forty-six control children with diarrhea were tested and 22 had rotavirus infection; rotavirus was not detected in 39 asymptomatic control children. One immunodeficient patient with X-linked agammaglobulinemia and one with severe combined immunodeficiency had chronic, symptomatic rotavirus infection with rotavirus excretion lasting more than six weeks. The other two immunodeficient patients and eight control children eliminated the rotavirus from their stools in periods ranging from two to 12 days. Rotavirus antigen was detected in the sera of three of the four immunodeficient patients; none of the 14 control infants tested had rotavirus antigen detected in their sera. This study indicates that rotavirus may produce a chronic infection in immunodeficient children.

DNA methylation signatures within the human brain

DNA methylation is a heritable modification of genomic DNA central to development, imprinting, transcriptional regulation, chromatin structure, and overall genomic stability. Aberrant DNA methylation of individual genes is a hallmark of cancer and has been shown to play an important role in neurological disorders such as Rett syndrome. Here, we asked whether normal DNA methylation might distinguish individual brain regions. We determined the quantitative DNA methylation levels of 1,505 CpG sites representing 807 genes with diverse functions, including proliferation and differentiation, previously shown to be implicated in human cancer. We initially analyzed 76 brain samples representing cerebral cortex (n=35), cerebellum (n=34), and pons (n=7), along with liver samples (n=3) from 43 individuals. Unsupervised hierarchical analysis showed clustering of 33 of 35 cerebra distinct from the clustering of 33 of 34 cerebella, 7 of 7 pons, and all 3 livers. By use of comparative marker selection and permutation testing, 156 loci representing 118 genes showed statistically significant differences--a >or=17% absolute change in DNA methylation (P<.004)--among brain regions. These results were validated for all six genes tested in a replicate set of 57 samples. Our data suggest that DNA methylation signatures distinguish brain regions and may help account for region-specific functional specialization.

Neuropsychological functioning in bipolar disorder and schizophrenia

BACKGROUND

Some patients with bipolar disorder (BD) demonstrate neuropsychological deficits even when stable. However, it remains unclear whether these differ qualitatively from those seen in schizophrenia (SZ).

METHODS

We compared the nature and severity of cognitive deficits shown by 106 patients with SZ and 66 patients with BD to 316 healthy adults (NC). All participants completed a cognitive battery with 19 individual measures. After adjusting their test performance for age, sex, race, education, and estimated premorbid IQ, we derived regression-based T-scores for each measure and the six cognitive domains.

RESULTS

Both patient groups performed significantly worse than NCs on most (BD) or all (SZ) cognitive tests and domains. The resulting effect sizes ranged from .37 to 1.32 (mean=.97) across tests for SZ patients and from .23 to .87 (mean=.59) for BD patients. The Pearson correlation of these effect sizes was .71 (p<.001).

CONCLUSIONS

Patients with bipolar disorder suffer from cognitive deficits that are milder but qualitatively similar to those of patients with schizophrenia. These findings support the notion that schizophrenia and bipolar disorder show greater phenotypic similarity in terms of the nature than severity of their neuropsychological deficits.

A two-year study of bacterial, viral, and parasitic agents associated with diarrhea in rural Bangladesh

Enteric pathogens associated with diarrhea were studied for two years at a diarrhea treatment center in rural Bangladesh. Enterotoxigenic Escherichia coli (ETEC) was the most frequently identified pathogen for patients of all ages. Rotavirus and ETEC were isolated from approximately 50% and approximately 25%, respectively, of patients less than two years of age. A bacterial or viral pathogen was identified for 70% of these young children and for 56% of all patients with diarrhea. Most ETEC isolates were obtained in the hot dry months of March and April and the hot wet months of August and September. Rotavirus identification peaked in the cool dry months of December and January, but infected patients were found year-round. The low case-fatality rates for patients with watery diarrhea and substantial dehydration further document the usefulness of treating patients with diarrhea with either a glucose- or sucrose-base electrolyte solution such as those used in this treatment center.

Epidemiology of human rotavirus Types 1 and 2 as studied by enzyme-linked immunosorbent assay

To determine the relative importance of two known serotypes of human rotavirus, we developed an enzyme-linked immunosorbent assay to differentiate serotype-specific rotavirus antigen and antibody. Using this technic, we studied the epidemiology of the two serotypes in acute gastroenteritis. Seventy-seven per cent of 414 rotavirus isolates were Type 2, and the remainder were Type 1. The serotype distribution was similar in specimens from children in Washington, D.C., and other parts of the world. Sero-epidemiologic studies revealed that most children living in the Washington, D.C., area acquired antibody to both types by the age of two years. An analysis of children who were reinfected indicated that sequential infections usually involved different serotypes and that illness caused by one serotype did not provide resistance to illness caused by the other serotype. These results suggest that, to be completely effective, a vaccine must provide resistance to both serotypes.

Infectious gastroenteritis in bone-marrow-transplant recipients

We prospectively evaluated infections with several gastrointestinal pathogens in patients undergoing bone-marrow transplantation, in an attempt to correlate infection with morbidity and mortality. Thirty-one of 78 patients (40 per cent) were infected with one or more of the following enteric pathogens during the study: adenovirus (12 infections), rotavirus (nine), coxsackievirus (four), or Clostridium difficile (12). Several patients were infected with more than one pathogen. Infection correlated with the occurrence of diarrhea and abdominal cramps. The mortality rate among the infected patients was 55 per cent--significantly higher than the rate (13 per cent) among the noninfected patients (P less than 0.001). This study indicates that enteric pathogens that often cause mild diarrhea in normal populations can cause serious infections in marrow-transplant recipients. Measures aimed at preventing or treating such infections might reduce the morbidity and mortality associated with marrow transplantation.

Enzyme immunoassays for the detection of infectious antigens in body fluids: current limitations and future prospects

Enzyme immunoassays are attaining increased usage for the direct detection of microbial antigens in body fluids. Advantages of enzyme immunoassays include a high degree of sensitivity resulting from the inherent magnification of the enzyme-substrate reaction and the use of objective end points without the need for radioactivity. Enzyme immunoassays have been developed for the reliable detection of several important microbial antigens in body fluids, including antigens of rotavirus, hepatitis B virus, and Haemophilus influenzae type b. However, standard enzyme immunoassay techniques are not sufficiently sensitive for the measurement of some antigens from other viruses, bacteria, and parasites in concentrations that commonly occur in body fluids during the course of infectious diseases. This review examines some of the limitations of currently available enzyme immunoassay technology and discusses approaches to increasing the sensitivity and specificity of enzyme immunoassay systems. Methods for improving these assay systems include the use of monoclonal antibodies, improved methods of enzyme-immunoreactant conjugation, more sensitive substrate systems, improved methods of antigen-antibody access, and the direct measurement of microbial enzymes. The use of such techniques should lead to the development of efficient enzyme immunoassay systems for the direct detection of a wide range of bacterial, viral, and parasitic infections.

Toxoplasma gondii as a risk factor for early-onset schizophrenia: analysis of filter paper blood samples obtained at birth

BACKGROUND

Infections during fetal life or neonatal period, including infections with Toxoplasma gondii, may be associated with a risk for schizophrenia and other mental disorders. The objectives of this study were to study the association between serological markers for maternal and neonatal infection and the risk for schizophrenia, related psychoses, and affective disorders in a national cohort of newborns.

METHODS

This study was a cohort-based, case-control study combining data from national population registers and patient registers and a national neonatal screening biobank in Denmark. Patients included persons born in Denmark in 1981 or later followed up through 1999 with respect to inpatient or outpatient treatment for schizophrenia or related disorders (ICD-10 F2) or affective disorders (ICD-10 F3).

RESULTS

Toxoplasma gondii immunoglobulin G (IgG) levels corresponding to the upper quartile among control subjects were significantly associated with schizophrenia risk (odds ratio [OR] = 1.79, p = .045) after adjustment for urbanicity of place of birth, year of birth, gender, and psychiatric diagnoses among first-degree relatives. There was no significant association between any marker of infection and other schizophrenia-like disorders or affective disorders.

CONCLUSIONS

Our study supports an association between Toxoplasma gondii and early-onset schizophrenia. Further studies are needed to establish if the association is causal and if it generalizes to cases with onset after age 18.

Expression of the kynurenine pathway enzyme tryptophan 2,3-dioxygenase is increased in the frontal cortex of individuals with schizophrenia

Markers of the kynurenine pathway were studied in postmortem frontal cortex obtained from individuals with schizophrenia and controls. Quantitative endpoint RT-PCR was used to measure mRNA transcripts. Of the two enzymes capable of catalyzing the first step in the pathway, tryptophan 2,3-dioxygenase (TDO2) and indoleamine dioxygenase (IDO), the concentration of mRNA for TDO2 was found to be elevated 1.6-fold in the schizophrenia group (P = 0.03), whereas the concentration of the mRNA for IDO was not significantly different between the schizophrenia and control groups. Immunohistochemistry showed an increased density of TDO2-immunopositive astroglial cells in the white matter of patients with schizophrenia (P = 0.04). Neurons and vessels were also immunopositive for TDO2, but there were no significant differences in labeling of these structures between the two groups. These results add to the evidence that kynurenine pathway changes might be involved in the pathogenesis of schizophrenia and the schizophrenia-like psychoses of other disorders.