Relationship between toxoplasmosis and autism: A systematic review and meta-analysis

The Potential Association Between Latent Toxoplasma Gondii Infection and Opioid Abuse: A Registry-Based Sero-Molecular Case-Control Study

Toxoplasma gondii is a ubiquitous parasitic protozoan that can cause neurological and psychiatric disorders, potentially impacting human emotional behavior. This study aimed to explore serological and molecular evidence of T. gondii infection in opioid abusers in northern Iran. In this case-control study, opioid abusers who were referred to substance abuse rehabilitation centers in Mazandaran Province, northern Iran, were enrolled. Blood samples were collected from the participants to perform a serological assay to detect T. gondii IgG and IgM antibodies. A polymerase chain reaction (PCR) test was also conducted on buffy coats of the blood samples. The study comprised a total of 474 participants, with 239 individuals being opioid abusers and 235 healthy individuals serving as the control group. The results indicated that 163 opioid abusers (68.2%) were positive for T. gondii IgG, whereas 76 (31.8%) were negative. Among the control group, 63 individuals (26.8%) tested positive for T. gondii IgG, whereas 172 (73.2%) tested negative. This difference was statistically significant according to p = 0.01, odds ratio (OR) = 2.67, and 95% confidence interval (CI) = 1.03-4.15. In addition, 7.1% (17/239) of the case and 2.1% (5/235) of the control groups were PCR positive for Toxoplasma DNA. This difference was statistically significant (p = 0.01; OR = 2.96; 95%; CI = 0.94-7.01). In contrast, all of the participants were negative for T. gondii IgM antibodies. Our findings demonstrated that the sero-molecular prevalence of latent T. gondii infection in opioid abusers is significantly higher than that in healthy individuals. This suggests a potential correlation between T. gondii IgG antibody positivity and PCR results with opioid abuse.

Effect of the flavonoid compound glabridin on tachyzoites and bradyzoites of Toxoplasma gondii

BACKGROUND

Toxoplasma gondii (T. gondii) is one of the most prevalent parasites worldwide. At present, the majority of drugs used for the treatment of toxoplasmosis target the tachyzoite stage of T. gondii and are largely ineffective against bradyzoites. Furthermore, these treatments are typically accompanied by adverse events. Consequently, there is an urgent need for the development of novel drugs that are both safe and effective against T. gondii.

METHODS

A total of 20 flavonoids were preliminarily screened for their anti-T. gondii activity using microscopy. Next, the cell counting kit (CCK)-8 method was employed to assess the toxicity of glabridin (GLA) to host cells, while the RH strain of T.0gondii, which expresses β-galactosidase, was utilized to evaluate the inhibitory, anti-invasive, and antiproliferative effects of GLA on T. gondii. In addition, the Prugniaud (PRU) strain was employed to investigate the impact of GLA on the bradyzoites of T. gondii. Subsequently, the effect of GLA on the ultrastructure of T. gondii was examined via transmission electron microscopy (TEM), followed by an assessment of the influence of GLA on the autophagy and mitochondria of T. gondii through monodansylcadaverine (MDC), MitoTracker™ red CMXRos, and CM-HDCFDA and MitoSOX Red staining.

RESULTS

Among the 20 flavonoids assessed, GLA exhibited the most potent anti-T. gondii activity. Indeed, it significantly inhibited both the invasive and proliferative abilities of T. gondii, thereby disrupting its lytic cycle. Moreover, GLA markedly reduced the number of bradyzoites and concurrently inhibited cyst growth. Meanwhile, ultrastructural analysis revealed that GLA induced mitochondrial swelling, membrane rupture, and autophagy in T. gondii. Finally, fluorescent probe staining provided further evidence that GLA triggers mitochondrial dysfunction and autophagy in this parasite.

CONCLUSIONS

Our findings collectively indicate that the flavonoid compound GLA exhibits significant activity against both T. gondii tachyzoites and bradyzoites. The underlying mechanism of action potentially involves the induction of autophagy and mitochondrial dysfunction and the disruption of the membrane of T. gondii, thereby offering new avenues for treating toxoplasmosis and establishing a theoretical reference for future research.

Association between latent toxoplasmosis and bipolar disorder: a case-control seroprevalence study

BACKGROUND

Toxoplasma gondii (T. gondii) is the most successful obligate protozoan that can infect warm-blooded vertebrate hosts. Some researchers suggest that the presence of Toxoplasma cysts in the brain can lead to mental disorders. Bipolar disorder (BD) is one of the serious neuropsychiatric disorders. Several studies have shown a high seroprevalence of T. gondii in bipolar patients. Therefore, this study aims to determine the prevalence of this infection in patients with BD.

METHODS

In this case-control study, anti-Toxoplasma immunoglobulin (Ig) G and IgM antibodies were measured in serum samples from 115 patients with BD and 115 subjects without this disorder from the general population using commercially available enzyme-linked immunosorbent assay. Demographic characteristics of the patient and control groups, information about T. gondii infection and BD, and their potential risk factors were analyzed. We utilized the Mann-Whitney U test for continuous variables, the chi-square test for categorical data, and multivariate logistic regression to assess T. gondii infection and BD, with significance set at P < 0.05.

RESULTS

Twenty-eight (24.34%) of 115 patients with BD and 10 (8.7%) of 115 controls had anti-T. gondii IgG antibodies. IgM antibodies against T. gondii were not reported to be positive in any participants. Furthermore, there was a statistically significant difference in the results [odds ratio (OR) = 2.89: 95% confidence interval (CI) = 1.08-7.73. P = 0.03]. Within the study population, various factors were identified as significant risk factors for BD: sex (OR 8.10, 95% CI 3.16-20.75), age 20-50 (OR 5.11, 95% CI 1.81-14.45), age over 50 (OR 19.54, 95% CI 4.02-94.89), education level (OR 0.24, 95% CI 0.09-0.60), working status (non-employment, OR 4.12, 95% CI 1.65-10.30), and income (middle, OR 0.29, 95% CI 0.10-0.89; high, OR 0.12, 95% CI 0.01-0.77), all with P-values less than 0.05. In addition, in the group of patients, there was no statistically significant relationship between T. gondii infection with the type of bipolar disease (P = 0.93), the severity of the disease (P = 0.61), and the history of suicide attempts (P = 0.63).

CONCLUSION

This study showed that toxoplasmosis is a risk factor for BD and increases the chance of developing BD. However, more studies with a larger sample size are recommended to clarify the development pathways of this disorder and provide new strategies for the prevention and treatment of this disease.

CLINICAL TRIAL

Not applicable.

Impact of chronic toxoplasmosis in pregnancy: Association between maternal IgG antibodies against T. gondii and neurocognitive development effects

Toxoplasmosis presents notable hazards in the context of pregnancy, impacting the health of the mother and the neurodevelopment of the fetus via immune reactions and possible vertical transmission. The maternal immune response from chronic Toxoplasma gondii (T. gondii) infection may negatively influence fetal neurodevelopment. This research evaluated the association between the seroprevalence of chronic T. gondii and cytomegalovirus infection in pregnant women and the neuropsychological development of their children at 12 months of age. A follow-up study evaluated women during the gestational period and their respective infants. The pregnant women were tested for the presence of antibodies to infectious agents: T. gondii, cytomegalovirus (CMV), syphilis, human immunodeficiency virus (HIV), hepatitis B and C. Detailed information about the newborns was extracted from medical records. At 12 ± 3 months of age, the infant's neurodevelopment was assessed using the Bayley-III Scales of Infant and Toddler Development by a trained specialist under the supervision of a neuropsychologist. A statistically significant association was found between maternal IgG anti-T. gondii levels and lower scores on the Bayley-III cognition scale, with a non-standardized β-coefficient of -0.078 (95 %-CI: -0.144 to -0.013), accounting for 35.1 % of the variation in this outcome. These results suggest that chronic maternal T. gondii infection, even without vertical transmission, may be associated with subtle changes in the child's cognitive development. Therefore, monitoring and early intervention are essential to identify and address possible delays in childhood neurodevelopment related to chronic maternal toxoplasmosis.

In vitro and in vivo activity evaluation and mode of action of broxaldine on Toxoplasma gondii

Toxoplasma gondii (T. gondii) is a highly successful global parasite, infecting about one-third of the world's population and significantly affecting human life and the economy. However, current drugs for toxoplasmosis treatment have considerable side effects, and there is no specific drug to meet current needs. This study aims to evaluate the anti-T. gondii activity of broxaldine (BRO) in vitro and in vivo and explore its mechanism of action. Our results showed that compared to the control group, the invasion rate of tachyzoites in the 4 μg/mL BRO group was only 14.31%, and the proliferation rate of tachyzoites in host cells was only 1.23%. Furthermore, BRO disrupted the lytic cycle of T. gondii and reduced the size and number of cysts in vitro. A mouse model of acute toxoplasmosis reported a 41.5% survival rate after BRO treatment, with reduced parasite load in tissues and blood. The subcellular structure of T. gondii was observed, including disintegration of T. gondii, mitochondrial swelling, increased liposomes, and the presence of autophagic lysosomes. Further investigation revealed enhanced autophagy, increased neutral lipids, and decreased mitochondrial membrane potential in T. gondii treated with BRO. The results also showed a significant decrease in ATP levels. Overall, BRO demonstrates good anti-T. gondii activity in vitro and in vivo; therefore, it has the potential to be used as a lead compound for anti-T. gondii treatment.

Joint exome and metabolome analysis in individuals with dyslexia: Evidence for associated dysregulations of olfactory perception and autoimmune functions

Dyslexia is a learning disability that negatively affects reading, writing, and spelling development at the word level in 5%-9% of children. The phenotype is variable and complex, involving several potential cognitive and physical concomitants such as sensory dysregulation and immunodeficiencies. The biological pathogenesis is not well-understood. Toward a better understanding of the biological drivers of dyslexia, we conducted the first joint exome and metabolome investigation in a pilot sample of 30 participants with dyslexia and 13 controls. In this analysis, eight metabolites of interest emerged (pyridoxine, kynurenic acid, citraconic acid, phosphocreatine, hippuric acid, xylitol, 2-deoxyuridine, and acetylcysteine). A metabolite-metabolite interaction analysis identified Krebs cycle intermediates that may be implicated in the development of dyslexia. Gene ontology analysis based on exome variants resulted in several pathways of interest, including the sensory perception of smell (olfactory) and immune system-related responses. In the joint exome and metabolite analysis, the olfactory transduction pathway emerged as the primary pathway of interest. Although the olfactory transduction and Krebs cycle pathways have not previously been described in dyslexia literature, these pathways have been implicated in other neurodevelopmental disorders including autism spectrum disorder and obsessive-compulsive disorder, suggesting the possibility of these pathways playing a role in dyslexia as well. Immune system response pathways, on the other hand, have been implicated in both dyslexia and other neurodevelopmental disorders.

Effective factors in the pathogenesis of Toxoplasmagondii

Toxoplasma gondii (T. gondii) is a cosmopolitan protozoan parasite in humans and animals. It infects about 30 % of the human population worldwide and causes potentially fatal diseases in immunocompromised hosts and neonates. For this study, five English-language databases (ScienceDirect, ProQuest, Web of Science, PubMed, and Scopus) and the internet search engine Google Scholar were searched. This review was accomplished to draw a global perspective of what is known about the pathogenesis of T. gondii and various factors affecting it. Virulence and immune responses can influence the mechanisms of parasite pathogenesis and these factors are in turn influenced by other factors. In addition to the host's genetic background, the type of Toxoplasma strain, the routes of transmission of infection, the number of passages, and different phases of parasite life affect virulence. The identification of virulence factors of the parasite could provide promising insights into the pathogenesis of this parasite. The results of this study can be an incentive to conduct more intensive research to design and develop new anti-Toxoplasma agents (drugs and vaccines) to treat or prevent this infection. In addition, further studies are needed to better understand the key agents in the pathogenesis of T. gondii.

The assessment of microbial infection in children with autism spectrum disorders and genetic folate cycle deficiency

BACKGROUND

The results of disparate clinical studies indicate abnormally frequent cases of certain microorganisms in children with autism spectrum disorders (ASD). However, these data require clarification and systematization. The study aims to study the structure of the microbial profile in children with ASD and genetic folate cycle deficiency (GFCD) and consider differences in diagnostic approaches for identifying microorganisms of different types.

METHODS

The study analyzed medical data from 240 children (187 boys and 63 girls) with GFCD aged 2 to 9 years. The children had clinical manifestations of ASD (the study group, SG). The control group (CG) included 53 clinically healthy children (37 boys and 16 girls) of the same age but without GFCD. Both groups of children were tested on active herpetic infections (HSV-1/2, VZV, EBV, CMV, HHV-6, HHV-7, HHV-8), ТТV, Streptococcus pyogenes, Candida albicans, Borrelia burgdorferi, Mycoplasma pneumoniae, Chlamydia pneumoniae, Yersinia enterocolitica, Toxoplasma gondii, congenital CMV neuroinfection and postnatal HSV-1/2 encephalitis. The testing used diagnostic methods specified in PubMed-indexed studies.

RESULTS

In the SG, TTV was found in 196 children (82%), HHV-7 - in 172 (72%), HHV-6 - in 162 (68%), EBV - in 153 (64%), Streptococcus pyogenes - in 127 (53%), Candida albicans - in 116 (48%), Borrelia - in 107 (45%), Mycoplasma pneumoniae - in 94 (39%), Chlamydia pneumoniae - in 85 (35%), Yersinia entеrocolitica - in 71 (30%), Toxoplasma gondii - in 54 (23%), congenital CMV neuroinfection - in 26 (11%), and postnatal HSV-1/2 encephalitis - in 11 children (5% of cases) (p < p0.05; Z < Z0.05). In the SG, there was a higher microbial load in older children (p < p0.05; Z < Z0.05). No gender differences were found.

CONCLUSIONS

The study described and characterized a specific abnormal microbial spectrum with a predominance of viral opportunistic agents in children with ASD associated with GFCD.

Genetic disruption of dopamine β-hydroxylase dysregulates innate responses to predator odor in mice

In rodents, exposure to predator odors such as cat urine acts as a severe stressor that engages innate defensive behaviors critical for survival in the wild. The neurotransmitters norepinephrine (NE) and dopamine (DA) modulate anxiety and predator odor responses, and we have shown previously that dopamine β-hydroxylase knockout (Dbh -/-), which reduces NE and increases DA in mouse noradrenergic neurons, disrupts innate behaviors in response to mild stressors such as novelty. We examined the consequences of Dbh knockout on responses to predator odor (bobcat urine) and compared them to Dbh-competent littermate controls. Over the first 10 min of predator odor exposure, controls exhibited robust defensive burying behavior, whereas Dbh -/- mice showed high levels of grooming. Defensive burying was potently suppressed in controls by drugs that reduce NE transmission, while excessive grooming in Dbh -/- mice was blocked by DA receptor antagonism. In response to a cotton square scented with a novel "neutral" odor (lavender), most control mice shredded the material, built a nest, and fell asleep within 90 min. Dbh -/- mice failed to shred the lavender-scented nestlet, but still fell asleep. In contrast, controls sustained high levels of arousal throughout the predator odor test and did not build nests, while Dbh -/- mice were asleep by the 90-min time point, often in shredded bobcat urine-soaked nesting material. Compared with controls exposed to predator odor, Dbh -/- mice demonstrated decreased c-fos induction in the anterior cingulate cortex, lateral septum, periaqueductal gray, and bed nucleus of the stria terminalis, but increased c-fos in the locus coeruleus and medial amygdala. These data indicate that relative ratios of central NE and DA signaling coordinate the type and valence of responses to predator odor.

Genetic disruption of dopamine β-hydroxylase dysregulates innate responses to predator odor in mice

In rodents, exposure to predator odors such as cat urine acts as a severe stressor that engages innate defensive behaviors critical for survival in the wild. The neurotransmitters norepinephrine (NE) and dopamine (DA) modulate anxiety and predator odor responses, and we have shown previously that dopamine β-hydroxylase knockout (Dbh -/-), which reduces NE and increases DA in mouse noradrenergic neurons, disrupts innate behaviors in response to mild stressors such as novelty. We examined the consequences of Dbh knockout (Dbh -/-) on responses to predator odor (bobcat urine) and compared them to Dbh-competent littermate controls. Over the first 10 min of predator odor exposure, controls exhibited robust defensive burying behavior, whereas Dbh -/- mice showed high levels of grooming. Defensive burying was potently suppressed in controls by drugs that reduce NE transmission, while excessive grooming in Dbh -/- mice was blocked by DA receptor antagonism. In response to a cotton square scented with a novel "neutral" odor (lavender), most control mice shredded the material, built a nest, and fell asleep within 90 min. Dbh -/- mice failed to shred the lavender-scented nestlet, but still fell asleep. In contrast, controls sustained high levels of arousal throughout the predator odor test and did not build nests, while Dbh -/- mice were asleep by the 90-min time point, often in shredded bobcat urine-soaked nesting material. Compared with controls exposed to predator odor, Dbh -/- mice demonstrated decreased c-fos induction in the anterior cingulate cortex, lateral septum, periaqueductal gray, and bed nucleus of the stria terminalis, but increased c-fos in the locus coeruleus and medial amygdala. These data indicate that relative ratios of central NE and DA signaling coordinate the type and valence of responses to predator odor.

Toxoplasma infection and Rhesus blood group system: A systematic review and meta-analysis

BACKGROUND

Toxoplasmosis is one of the most common infections in humans and animals, which is caused by an obligate intracellular opportunistic parasite known as Toxoplasma gondii (T. gondii). Some data have shown that both Rhesus (Rh)-positive and Rh-negative individuals differ in response to biological factors, including Toxoplasma infection. Therefore, this systematic review and meta-analysis was conducted to investigate the scientific evidence regarding the possible association between the Rh blood group and Toxoplasma infection and to determine the seroprevalence of T. gondii in the Rh blood group system.

METHODS

The research was conducted on PubMed, ScienceDirect, ProQuest, and Google Scholar databases until January 2023. Twenty-one cross-sectional studies were included with a total of 10910 people. The data were synthesized using a random effect model with 95% confidence intervals (CIs).

RESULTS

The overall prevalence of T. gondii was calculated at 32.34% (CI 95%: 28.23-36.45%) and 33.35% (CI 95%: 19.73-46.96%) in Rh-positive and Rh-negative blood groups. In addition, the pooled OR for the relationship between the Rh blood group and the seroprevalence of T. gondii was 0.96 (95% CI: 0.72-1.28).

CONCLUSIONS

This meta-analysis showed a high prevalence of Toxoplasma infection in both Rh-negative and positive blood groups. This systematic review and meta-analysis revealed that no significant association was found between toxoplasmosis and Rh factor. Because of the limited number of studies in this field, more research is recommended to determine the exact relationship between toxoplasmosis and the Rh factor.

Toxoplasmosis and cytomegalovirus infection and their role in Egyptian autistic children

Autism is a neurodevelopmental disorder with a significantly increased incidence rate across the world over the past few years. Toxoplasmosis and cytomegalovirus (CMV) infection are globally prevalent and have been associated with diverse neurological and psychiatric disorders. A few studies have demonstrated the role of toxoplasmosis and CMV as potential etiological factors for autism. Accordingly, this study was performed to estimate the relationship between toxoplasmosis and CMV infection in children with autism as well as to assess their impact on the Childhood Autism Rating Scale (CARS) score. A total of 45 autistic children (6 girls, 39 boys) and 45 (21 girls, 24 boys) healthy control children were enrolled in our study. Their blood samples were collected and tested for the presence of Toxoplasma and CMV (IgG and IgM) antibodies and DNA by ELISA and real-time PCR (RT-PCR), respectively. Toxoplasmosis was detected in 11 (24.4%) autistic children through the ELISA [10 (22.2%) IgG + /IgM - and 1 (2.2%) IgG + /IgM +]; however, RT-PCR assay recorded only 1 positive case (2.2%), while it was detected in 10 (22.2%) control children through ELISA [9 (20%) IgG + /IgM - and 1 (2.2%) IgG + /IgM +] and 1 (2.2%) by RT-PCR. On the other hand, CMV infection was detected in all autistic children with 44 (97.8%) testing positive by ELISA [24 (53.3%) IgG + /IgM - , 18 (40%) IgG + /IgM + and 2 (4.4%) IgG - /IgM +] and 25 (55.6%) testing positive by RT-PCR assay. In addition, ELISA assay recorded 43 (95.6%) [19 (42.2%) IgG + /IgM + and 22 (48.9%) IgG + /IgM - and 2 (4.4%) IgG-/IgM +] and RT-PCR recorded 21 (46.7%) positive samples in control children with CMV. No significant difference was noted between autistic and control children for the overall prevalence of Toxoplasma or/and CMV infection. Similarly, the CARS score indicated a non-significant difference with Toxoplasma or/and CMV infection. Our data does not show an association between autism and toxoplasmosis or/and CMV infection. Nevertheless, considering that autistic children are at a high risk of contracting these infections, further studies with a larger sample size are recommended.

Концепція імунопатогенезу енцефалопатії у дітей з розладами спектра аутизму, асоційованими з генетичним дефіцитом фолатного циклу, та потенційні терапевтичні напрямки

Аналітичний огляд підсумовує результати власних досліджень у поєднанні із прогресивними поглядами сучасних наукових шкіл щодо актуальної проблеми у світі — діагностики і лікування дітей із розладами спектра аутизму. Отримані дані дозволили сформулювати наукову концепцію імунопатогенезу енцефалопатії у дітей, яка описує найбільш ймовірний сценарій патологічних подій, починаючи з появи патогенних поліморфних замін нуклеотидів у геномі плода і закінчуючи розвитком клінічних симптомів нейропсихіатричних порушень у дитини. Висунення такої концепції відкриває шлях до розробки алгоритму лікування дітей з розладами спектра аутизму, який раніше не був доступним.

Epigenetic Manipulation of Psychiatric Behavioral Disorders Induced by Toxoplasma gondii

Toxoplasma gondii is known to have a complex life cycle and infect almost all kinds of warm-blooded animals around the world. The brain of the host could be persistently infected by cerebral cysts, and a variety of psychiatric disorders such as schizophrenia and suicide have been reported to be related with latent toxoplasmosis. The infected animals showed fear reduction and a tendency to be preyed upon. However, the mechanism of this “parasites manipulation” effects have not been elucidated. Here, we reviewed the recent infection prevalence of toxoplasmosis and the evidence of mental and behavioral disorders induced by T. gondii and discussed the related physiological basis including dopamine dysregulation and gamma-aminobutyric acid (GABA) pathway and the controversial opinion of the necessity for cerebral cysts existence. Based on the recent advances, we speculated that the neuroendocrine programs and neurotransmitter imbalance may play a key role in this process. Simultaneously, studies in the evaluation of the expression pattern of related genes, long noncoding RNAs (lncRNAs), and mRNAs of the host provides a new point for understanding the mechanism of neurotransmitter dysfunction induced by parasite manipulation. Therefore, we summarized the animal models, T. gondii strains, and behavioral tests used in the related epigenetic studies and the responsible epigenetic processes; pinpointed opportunities and challenges in future research including the causality evidence of human psychiatric disorders, the statistical analysis for rodent-infected host to be more vulnerable preyed upon; and identified responsible genes and drug targets through epigenetics.

Sero-molecular survey on Toxoplasma gondii infection among drug addicted and non-addicted individuals: a case-control study

Background

Up to now, epidemiological studies on the prevalence of Toxoplasma gondii infection among drug addicted individuals have been rarely performed. By designing an age and sex matched case–control study, we sought to determine the prevalence and associated factors with T. gondii infection in these population using serological and molecular techniques.

Methods

One hundred and thirty-seven drug addicted individuals and 141 healthy subjects were enrolled in this study. Informed consent as well as a standard questionnaire were obtained from all subjects participating. Blood samples were collected from each participant and the serum was screened for anti-Toxoplasma antibodies (IgG and IgM). PCR assay was performed using the primer pair targeting the RE and GRA6 genes of T. gondii. Then, PCR products were sequenced to determine genotype.

Results

The seroprevalence of T. gondii infection based on IgG titer was 34.3% in case and 9.9% in the control groups, revealing a statistically significant difference (OR = 4.37; 95% CI = 2.46–9.12; P = 0.001). After analyzing the variables studied through the questionnaire, age was the only significantly factor associated with the anti-T. gondii IgG antibody in case group. Considering PCR assays with RE genomic target, the prevalence of T. gondii infection was 5.1% in the case and 3.5% in control groups which the difference was no statistically significant (OR = 1.46; 95% CI = 0.45–4.73; P = 0.521). Subsequently, all sequenced samples were genotype #1 using the GRA6 genomic target.

Conclusions

T. gondii exposure is relatively high among drug addicted individuals in Iran, and there is a need for health policymakers and researchers to establish enlightenment and prevention programs for these population at risk of infection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06979-8.

Toxoplasmosis: Targeting neurotransmitter systems in psychiatric disorders

The most common form of the disease caused by Toxoplasma gondii (T. gondii) is latent toxoplasmosis due to the formation of tissue cysts in various organs, such as the brain. Latent toxoplasmosis is probably a risk factor in the development of some neuropsychiatric disorders. Behavioral changes after infection are caused by the host immune response, manipulation by the parasite, central nervous system (CNS) inflammation, as well as changes in hormonal and neuromodulator relationships. The present review focused on the exact mechanisms of T. gondii effect on the alteration of behavior and neurotransmitter levels, their catabolites and metabolites, as well as the interaction between immune responses and this parasite in the etiopathogenesis of psychiatric disorders. The dysfunction of neurotransmitters in the neural transmission is associated with several neuropsychiatric disorders. However, further intensive studies are required to determine the effect of this parasite on altering the level of neurotransmitters and the role of neurotransmitters in the etiology of host behavioral changes.

Microbiota and Microglia Interactions in ASD

Autism spectrum disorders (ASD) are serious, highly variable neurodevelopmental disorders, commonly characterized by the manifestation of specific behavioral abnormalities, such as stereotypic behaviors and deficits in social skills, including communication. Although the neurobiological basis for ASD has attracted attention in recent decades, the role of microglial cells, which are the main resident myeloid cell population in the brain, is still controversial and underexplored. Microglia play several fundamental roles in orchestrating brain development and homeostasis. As such, alterations in the intrinsic functions of these cells could be one of the driving forces responsible for the development of various neurodevelopmental disorders, including ASD. Microglia are highly sensitive to environmental cues. Amongst the environmental factors known to influence their intrinsic functions, the gut microbiota has emerged as a central player, controlling both microglial maturation and activation. Strikingly, there is now compelling data suggesting that the intestinal microbiota can play a causative role in driving the behavioural changes associated with ASD. Not only is intestinal dysbiosis commonly reported in ASD patients, but therapies targeting the microbiome can markedly alleviate behavioral symptoms. Here we explore the emerging mechanisms by which altered microglial functions could contribute to several major etiological factors of ASD. We then demonstrate how pre- and postnatal environmental stimuli can modulate microglial cell phenotype and function, underpinning the notion that reciprocal interactions between microglia and intestinal microbes could play a crucial role in ASD aetiology.

Neurological Findings in Children without Congenital Microcephaly Exposed to Zika Virus in Utero: A Case Series Study

The Zika virus can induce a disruptive sequence in the fetal brain and is manifested mainly by microcephaly. Knowledge gaps still exist as to whether the virus can cause minor disorders that are perceived later on during the first years of life in children who are exposed but are asymptomatic at birth. In this case series, we describe the outcomes related to neurodevelopment through the neurological assessment of 26 non-microcephalic children who had intrauterine exposure to Zika virus. Children were submitted for neurological examinations and Bayley Scales-III (cognition, language, and motor performance). The majority (65.4%) obtained satisfactory performance in neurodevelopment. The most impaired domain was language, with 30.7% impairment. Severe neurological disorders occurred in five children (19.2%) and these were spastic hemiparesis, epilepsy associated with congenital macrocephaly (Zika and human immunodeficiency virus), two cases of autism (one exposed to Zika and Toxoplasma gondii) and progressive sensorineural hearing loss (GJB2 mutation). We concluded that non-microcephalic children with intrauterine exposure to Zika virus, in their majority, had achieved satisfactory performance in all neurodevelopmental domains. One third of the cases had some impairment, but the predominant group had mild alterations, with low occurrence of moderate to severe disorders, similar to other studies in Brazil.