Maternal immune activation alters adult behavior, intestinal integrity, gut microbiota and the gut inflammation

Age-related changes in behavior profile in male offspring of rats treated with poly I:C-induced maternal immune activation in early gestation

BACKGROUND

Autism and schizophrenia are environmental risk factors associated with prenatal viral infection during pregnancy. It is still unclear whether behavior phenotypes change at different developmental stages in offspring following the activation of the maternal immune system.

METHODS

Sprague-Dawley rats received a single caudal vein injection of 10 mg/kg polyinosinic:polycytidylic acid (poly I:C) on gestational day 9 and the offspring were comprehensively tested for behaviors in adolescence and adulthood.

RESULTS

Maternal serum levels of interleukin (IL)-6, IL-1β and tumor necrosis factor-α were elevated in poly I:C-treated dams. The offspring of maternal poly I:C-induced rats showed increased anxiety, impaired social approach, and progressive impaired cognitive and sensorimotor gating function.

CONCLUSION

Maternal immune activation led to developmental specificity behavioral impairment in offspring.

Knockdown of Lhx6 during embryonic development results in neurophysiological alterations and behavioral deficits analogous to schizophrenia in adult rats

A decreased expression of specific interneuron subtypes, containing either the calcium binding protein parvalbumin (PV) or the neurotransmitter somatostatin (SST), are observed in the cortex and hippocampus of both patients with schizophrenia and rodent models used to study the disorder. Moreover, preclinical studies suggest that this loss of inhibitory function is a key pathological mechanism underlying the symptoms of schizophrenia. Interestingly, decreased expression of Lhx6, a key transcriptional regulator specific to the development and migration of PV and SST interneurons, is seen in human postmortem studies and following multiple developmental disruptions used to model schizophrenia preclinically. These results suggest that disruptions in interneuron development in utero may contribute to the pathology of the disorder. To recapitulate decreased Lhx6 expression during development, we used in utero electroporation to introduce an Lhx6 shRNA plasmid and knockdown Lhx6 expression in the brains of rats on gestational day 17. We then examined schizophrenia-like neurophysiological and behavioral alterations in the offspring once they reached adulthood. In utero Lhx6 knockdown resulted in increased ventral tegmental area (VTA) dopamine neuron population activity and a sex-specific increase in locomotor response to a psychotomimetic, consistent with positive symptomology of schizophrenia. However, Lhx6 knockdown had no effect on social interaction or spatial working memory, suggesting behaviors associated with negative and cognitive symptom domains were unaffected. These results suggest that knockdown of Lhx6 during development results in neurophysiological and behavioral alterations consistent with the positive symptom domain of schizophrenia in adult rats.

Maternal immune activation induces sex-dependent behavioral differences in a rat model of schizophrenia

Background

Maternal immune activation (MIA) is a mature means to construct a schizophrenia model. However, some preclinical studies have reported that a MIA-induced schizophrenia model seemed to have gender heterogeneity in behavioral phenotype. On the other hand, the MIA's paradigms were diverse in different studies, and many details could affect the effect of MIA. To some extent, it is not credible and scientific to directly compare the gender differences of different MIA programs. Therefore, it is necessary to study whether the sex of the exposed offspring leads to behavioral differences on the premise of maintaining a consistent MIA mode.

Methods

An animal model of schizophrenia was established by the administration of 10 mg/kg Poly (I: C) when dams were on day 9 of gestation. Then, a number of female and male offspring completed a series of behavioral tests during postnatal days 61-75.

Results

Compared with the female control group (n = 14), female MIA offspring (n = 12) showed a longer movement distance (d = 1.07, p < 0.05) and higher average speed (d = 1.08, p < 0.05) in the open field test (OFT). In the Y maze test, the percentage of entering the novel arm of female MIA offspring was lower (d = 0.92, p < 0.05). Compared with the male control group (n = 14), male MIA offspring (n = 13) displayed less movement distance (d = 0.93, p < 0.05) and a lower average speed (d = 0.94, p < 0.05) in the OFT. In the Y maze test, the proportion of exploration time in the novel arm of male MIA offspring was lower (d = 0.96, p < 0.05). In the EPM, male MIA offspring showed less time (d = 0.85, p < 0.05) and a lower percentage of time spent in the open arms (d = 0.85, p < 0.05). Male MIA offspring also had a lower PPI index (76 dB + 120 dB, d = 0.81, p < 0.05; 80 dB + 120 dB, d = 1.45, p < 0.01).

Conclusions

Our results showed that the behavioral phenotypes induced by prenatal immune activation were highly dependent on the sex of the offspring.

Prenatal and postnatal neuroimmune interactions in neurodevelopmental disorders

The intricate relationship between immune dysregulation and neurodevelopmental disorders (NDDs) has been observed across the stages of both prenatal and postnatal development. In this Review, we provide a comprehensive overview of various maternal immune conditions, ranging from infections to chronic inflammatory conditions, that impact the neurodevelopment of the fetus during pregnancy. Furthermore, we examine the presence of immunological phenotypes, such as immune-related markers and coexisting immunological disorders, in individuals with NDDs. By delving into these findings, we shed light on the potential underlying mechanisms responsible for the high occurrence of immune dysregulation alongside NDDs. We also discuss current mouse models of NDDs and their contributions to our understanding of the immune mechanisms underlying these diseases. Additionally, we discuss how neuroimmune interactions contribute to shaping the manifestation of neurological phenotypes in individuals with NDDs while also exploring potential avenues for mitigating these effects.

Autism spectrum disorders and the gastrointestinal tract: insights into mechanisms and clinical relevance

Autism spectrum disorders (ASDs) are recognized as central neurodevelopmental disorders diagnosed by impairments in social interactions, communication and repetitive behaviours. The recognition of ASD as a central nervous system (CNS)-mediated neurobehavioural disorder has led most of the research in ASD to be focused on the CNS. However, gastrointestinal function is also likely to be affected owing to the neural mechanistic nature of ASD and the nervous system in the gastrointestinal tract (enteric nervous system). Thus, it is unsurprising that gastrointestinal disorders, particularly constipation, diarrhoea and abdominal pain, are highly comorbid in individuals with ASD. Gastrointestinal problems have also been repeatedly associated with increased severity of the core symptoms diagnostic of ASD and other centrally mediated comorbid conditions, including psychiatric issues, irritability, rigid-compulsive behaviours and aggression. Despite the high prevalence of gastrointestinal dysfunction in ASD and its associated behavioural comorbidities, the specific links between these two conditions have not been clearly delineated, and current data linking ASD to gastrointestinal dysfunction have not been extensively reviewed. This Review outlines the established and emerging clinical and preclinical evidence that emphasizes the gut as a novel mechanistic and potential therapeutic target for individuals with ASD.

Effects of a gut-selective integrin-targeted therapy in male mice exposed to early immune activation, a model for the study of autism spectrum disorder

To clarify the role of gut mucosal immunity in ASD, we evaluated, in the early-life immune activation (EIA) mouse model, the effects of administration of a monoclonal antibody directed against the integrin alpha4 beta7 (α4β7 mAb), blocking the leukocyte homing into the gut mucosa. EIA is a double-hit variant of the maternal immune-activation (MIA) model, including both prenatal (Poly I:C) and postnatal (LPS) immune challenges. In C57BL6/J EIA male adult offspring mice, IL-1β and IL-17A mRNA colonic tissue content increased when compared with controls. Cytofluorimetric analyses of lymphocytes isolated from mesenteric lymph-nodes (MLN) and spleens of EIA mice show increased percentage of total and CD4+α4β7+, unstimulated and stimulated IL-17A+ and stimulated IFN-γ+ lymphocytes in MLN and CD4+α4β7+ unstimulated and stimulated IL-17A+ and stimulated IFN-γ+ lymphocytes in the spleen. Treatment with anti-α4β7 mAb in EIA male mice was associated with colonic tissue IL-1β, and IL-17A mRNA content and percentage of CD4+ IL-17A+ and IFN-γ+ lymphocytes in MLN and spleens comparable to control mice. The anti-α4β7 mAb treatment rescue social novelty deficit showed in the three-chamber test by EIA male mice. Increased levels of IL-6 and IL-1β and decreased CD68 and TGF-β mRNAs were also observed in hippocampus and prefrontal cortex of EIA male mice together with a reduction of BDNF mRNA levels in all brain regions examined. Anti-α4β7 mAb treatment restored the expression of BDNF, TGF-β and CD68 in hippocampus and prefrontal cortex. Improvement of the gut inflammatory status, obtained by a pharmacological agent acting exclusively at gut level, ameliorates some ASD behavioral features and the neuroinflammatory status. Data provide the first preclinical indication for a therapeutic strategy against gut-immune activation in ASD subjects with peripheral increase of gut-derived (α4β7+) lymphocytes expressing IL-17A.

Microglia and microbiome in schizophrenia: can immunomodulation improve symptoms?

In this overview, influences of microglia activation and disturbances of the microbiome in the devastating disorder schizophrenia are discussed. Despite previous assumptions of a primary neurodegenerative character of this disorder, current research underlines the important autoimmunological and inflammatory processes here. Early disturbances of microglial cells as well as cytokines could lead to weakness of the immunological system in the prodromal phase and then fully manifest in patients with schizophrenia. Measurements of microbiome features might allow identifying the prodromal phase. In conclusion, such thinking would imply several new therapeutic options regulating immune processes by old or new anti-inflammatory agents in patients.

Emerging Role of Kinin B1 Receptor in Persistent Neuroinflammation and Neuropsychiatric Symptoms in Mice Following Recovery from SARS-CoV-2 Infection

Evidence suggests that patients with long COVID can experience neuropsychiatric, neurologic, and cognitive symptoms. However, these clinical data are mostly associational studies complicated by confounding variables, thus the mechanisms responsible for persistent symptoms are unknown. Here we establish an animal model of long-lasting effects on the brain by eliciting mild disease in K18-hACE2 mice. Male and female K18-hACE2 mice were infected with 4 × 103 TCID50 of SARS-CoV-2 and, following recovery from acute infection, were tested in the open field, zero maze, and Y maze, starting 30 days post infection. Following recovery from SARS-CoV-2 infection, K18-hACE2 mice showed the characteristic lung fibrosis associated with SARS-CoV-2 infection, which correlates with increased expression of the pro-inflammatory kinin B1 receptor (B1R). These mice also had elevated expression of B1R and inflammatory markers in the brain and exhibited behavioral alterations such as elevated anxiety and attenuated exploratory behavior. Our data demonstrate that K18-hACE2 mice exhibit persistent effects of SARS-CoV-2 infection on brain tissue, revealing the potential for using this model of high sensitivity to SARS-CoV-2 to investigate mechanisms contributing to long COVID symptoms in at-risk populations. These results further suggest that elevated B1R expression may drive the long-lasting inflammatory response associated with SARS-CoV-2 infection.

Comparison of gut microbiome profile in patients with schizophrenia and healthy controls - A plausible non-invasive biomarker?

The human gut microbiome regulates brain function through the microbiome-gut-brain axis and is implicated in several neuropsychiatric disorders. However, the relationship between the gut microbiome and the pathogenesis of schizophrenia (SCZ) is poorly defined, and very few studies have examined the effect of antipsychotic treatment response. We aim to study the differences in the gut microbiota among drug-naïve (DN SCZ) and risperidone-treated SCZ patients (RISP SCZ), compared to healthy controls (HCs). We recruited a total of 60 participants, from the clinical services of a large neuropsychiatric hospital, which included DN SCZ, RISP SCZ and HCs (n = 20 each). Fecal samples were analyzed using 16s rRNA sequencing in this cross-sectional study. No significant differences were found in taxa richness (alpha diversity) but microbial composition differed between SCZ patients (both DN and RISP) and HCs (PERMANOVA, p = 0.02). Linear Discriminant Analysis Effect Size (LEfSe) and Random Forest model identified the top six genera, which significantly differed in abundance between the study groups. A specific genus-level microbial panel of Ruminococcus, UCG005, Clostridium_sensu_stricto_1 and Bifidobacterium could discriminate SCZ patients from HCs with an area under the curve (AUC) of 0.79, HCs vs DN SCZ (AUC: 0.68), HCs vs RISP SCZ (AUC: 0.93) and DN SCZ vs RISP SCZ (AUC: 0.87). Our study identified distinct microbial signatures that could aid in the differentiation of DN SCZ, RISP SCZ, and HCs. Our findings contribute to a better understanding of the role of the gut microbiome in SCZ pathophysiology and suggest potential targeted interventions.

Maternal Supplementation with N-Acetylcysteine Modulates the Microbiota-Gut-Brain Axis in Offspring of the Poly I:C Rat Model of Schizophrenia

The microbiota-gut-brain axis is a complex interconnected system altered in schizophrenia. The antioxidant N-acetylcysteine (NAC) has been proposed as an adjunctive therapy to antipsychotics in clinical trials, but its role in the microbiota-gut-brain axis has not been sufficiently explored. We aimed to describe the effect of NAC administration during pregnancy on the gut-brain axis in the offspring from the maternal immune stimulation (MIS) animal model of schizophrenia. Pregnant Wistar rats were treated with PolyI:C/Saline. Six groups of animals were studied according to the study factors: phenotype (Saline, MIS) and treatment (no NAC, NAC 7 days, NAC 21 days). Offspring were subjected to the novel object recognition test and were scanned using MRI. Caecum contents were used for metagenomics 16S rRNA sequencing. NAC treatment prevented hippocampal volume reduction and long-term memory deficits in MIS-offspring. In addition, MIS-animals showed lower bacterial richness, which was prevented by NAC. Moreover, NAC7/NAC21 treatments resulted in a reduction of proinflammatory taxons in MIS-animals and an increase in taxa known to produce anti-inflammatory metabolites. Early approaches, like this one, with anti-inflammatory/anti-oxidative compounds, especially in neurodevelopmental disorders with an inflammatory/oxidative basis, may be useful in modulating bacterial microbiota, hippocampal size, as well as hippocampal-based memory impairments.

Exposure to Antibiotics and Neurodevelopmental Disorders: Could Probiotics Modulate the Gut-Brain Axis?

In order to develop properly, the brain requires the intricate interconnection of genetic factors and pre-and postnatal environmental events. The gut-brain axis has recently raised considerable interest for its involvement in regulating the development and functioning of the brain. Consequently, alterations in the gut microbiota composition, due to antibiotic administration, could favor the onset of neurodevelopmental disorders. Literature data suggest that the modulation of gut microbiota is often altered in individuals affected by neurodevelopmental disorders. It has been shown in animal studies that metabolites released by an imbalanced gut-brain axis, leads to alterations in brain function and deficits in social behavior. Here, we report the potential effects of antibiotic administration, before and after birth, in relation to the risk of developing neurodevelopmental disorders. We also review the potential role of probiotics in treating gastrointestinal disorders associated with gut dysbiosis after antibiotic administration, and their possible effect in ameliorating neurodevelopmental disorder symptoms.

Amelioration of Maternal Immune Activation-Induced Autism Relevant Behaviors by Gut Commensal Parabacteroides goldsteinii

Autism spectrum disorder (ASD) is characterized by cognitive inflexibility and social deficits. Probiotics have been demonstrated to play a promising role in managing the severity of ASD. However, there are no effective probiotics for clinical use. Identifying new probiotic strains for ameliorating ASD is therefore essential. Using the maternal immune activation (MIA)-based offspring ASD-like mouse model, a probiotic-based intervention strategy was examined in female mice. The gut commensal microbe Parabacteroides goldsteinii MTS01, which was previously demonstrated to exert multiple beneficial effects on chronic inflammation-related-diseases, was evaluated. Prenatal lipopolysaccharide (LPS) exposure induced leaky gut-related inflammatory phenotypes in the colon, increased LPS activity in sera, and induced autistic-like behaviors in offspring mice. By contrast, P. goldsteinii MTS01 treatment significantly reduced intestinal and systemic inflammation and ameliorated disease development. Transcriptomic analyses of MIA offspring indicated that in the intestine, P. goldsteinii MTS01 enhanced neuropeptide-related signaling and suppressed aberrant cell proliferation and inflammatory responses. In the hippocampus, P. goldsteinii MTS01 increased ribosomal/mitochondrial and antioxidant activities and decreased glutamate receptor signaling. Together, significant ameliorative effects of P. goldsteinii MTS01 on ASD relevant behaviors in MIA offspring were identified. Therefore, P. goldsteinii MTS01 could be developed as a next-generation probiotic for ameliorating ASD.

Prenatal exposure to inflammation increases anxiety-like behaviors in F1 and F2 generations: possible links to decreased FABP7 in hippocampus

Anxiety disorder has a high prevalence, and the risk of anxiety increases with age. Prenatal inflammation during key developmental timepoints can result in long-term changes in anxiety phenotype, even over a lifetime and across generations. However, whether maternal inflammation exposure during late gestation has intergenerational transmission effects on age-related anxiety-like behaviors and the possible underlying mechanisms are largely unknown. Fatty acid binding protein 7 (FABP7) is critical in hippocampal neurogenesis and is closely related to neuropsychiatric diseases, including anxiety disorder. The current study investigated the effects of maternal (F0 generation) lipopolysaccharide administration (50 μg/kg, i.p.) during late gestation on anxiety-like behaviors and FABP7 expression in F1 and F2 offspring, as well as the potential sex-specificity of intergenerational effects. Anxiety-like behaviors were evaluated using open field (OF), elevated plus maze, and black–white alley (BWA) tests at 3 and 13 months of age. The protein and messenger RNA levels of FABP7 in the hippocampus were measured using Western blot and real-time quantitative polymerase chain reaction (PCR), respectively. Overall, gestational LPS exposure in the F0 generation increased anxiety levels and decreased FABP7 expression levels in the F1 generation, which carried over to the F2 generation, and the intergenerational effects were mainly transferred via the maternal lineage. Moreover, hippocampal FABP7 expression was significantly correlated with performance in the battery of anxiety tests. The present study suggested that prenatal inflammation could increase age-related anxiety-like behaviors both in F1 and F2 offspring, and these effects possibly link to the FABP7 expression.

Impact of Maternal Immune Activation on Nonhuman Primate Prefrontal Cortex Development: Insights for Schizophrenia

Late adolescence is a period of dynamic change in the brain as humans learn to navigate increasingly complex environments. In particular, prefrontal cortical (PFC) regions undergo extensive remodeling as the brain is fine-tuned to orchestrate cognitive control over attention, reasoning, and emotions. Late adolescence also presents a uniquely vulnerable period as neurodevelopmental illnesses, such as schizophrenia, become evident and worsen into young adulthood. Challenges in early development, including prenatal exposure to infection, may set the stage for a cascade of maladaptive events that ultimately result in aberrant PFC connectivity and function before symptoms emerge. A growing body of research suggests that activation of the mother's immune system during pregnancy may act as a disease primer, in combination with other environmental and genetic factors, contributing to an increased risk of neurodevelopmental disorders, including schizophrenia. Animal models provide an invaluable opportunity to examine the course of brain and behavioral changes in offspring exposed to maternal immune activation (MIA). Although the vast majority of MIA research has been carried out in rodents, here we highlight the translational utility of the nonhuman primate (NHP) as a model species more closely related to humans in PFC structure and function. In this review, we consider the protracted period of brain and behavioral maturation in the NHP, describe emerging findings from MIA NHP offspring in the context of rodent preclinical models, and lastly explore the translational relevance of the NHP MIA model to expand understanding of the etiology and developmental course of PFC pathology in schizophrenia.

KI Essence extract (a spleen-tonifying formula) promotes neurite outgrowth, alleviates oxidative stress and hypomyelination, and modulates microbiome in maternal immune activation offspring

Mushrooms and Chinese traditional herbs have bioactive nutraceuticals with multiple therapeutic functions, including antioxidant and antibacterial activities and microbiome modulation properties. Mushroom-derived bioactive compounds are used in medicines for the treatment of neurological disorders with abnormal brain–gut–microbiome axis. This study examined the effects of KI Essence extract, a spleen-tonifying formula, on neurite growth, antioxidant activity, hypomyelination modulation, and the microbiome profile in lipopolysaccharide (LPS)-induced maternal immune activation (MIA) offspring. The KI Essence extract induced PC12 cell neurite growth by increasing extracellular signal–regulated kinase (ERK) phosphorylation, promoting 2,2′-diphenyl-1-picrylhydrazyl radical scavenging activity, reducing the level of tert-butylhydroperoxide–induced lipid peroxidation in brain homogenates, protecting PC12 cells from H2O2-induced cell death (through the inhibition of ERK phosphorylation), alleviating hypomyelination, and downregulating interleukin‐1β through LPS-activated microglia production; moreover, the numbers of Enterobacteriaceae, Actinobacteria, Peptostreptococcaceae, Erysipelotrichaceae, and Bifidobacterium bacteria in MIA offspring increased. In summary, the KI Essence extract promotes neurite outgrowth, alleviates oxidative stress and hypomyelination, and modulates microbiota dysbiosis in MIA offspring.

Maternal immune activation and adolescent alcohol exposure increase alcohol drinking and disrupt cortical-striatal-hippocampal oscillations in adult offspring

Maternal immune activation (MIA) is strongly associated with an increased risk of developing mental illness in adulthood, which often co-occurs with alcohol misuse. The current study aimed to begin to determine whether MIA, combined with adolescent alcohol exposure (AE), could be used as a model with which we could study the neurobiological mechanisms behind such co-occurring disorders. Pregnant Sprague-Dawley rats were treated with polyI:C or saline on gestational day 15. Half of the offspring were given continuous access to alcohol during adolescence, leading to four experimental groups: controls, MIA, AE, and Dual (MIA + AE). We then evaluated whether MIA and/or AE alter: (1) alcohol consumption; (2) locomotor behavior; and (3) cortical-striatal-hippocampal local field potentials (LFPs) in adult offspring. Dual rats, particularly females, drank significantly more alcohol in adulthood compared to all other groups. MIA led to reduced locomotor behavior in males only. Using machine learning to build predictive models from LFPs, we were able to differentiate Dual rats from control rats and AE rats in both sexes, and Dual rats from MIA rats in females. These data suggest that Dual "hits" (MIA + AE) increases substance use behavior and disrupts activity in reward-related circuits, and that this may be a valuable heuristic model we can use to study the neurobiological underpinnings of co-occurring disorders. Our future work aims to extend these findings to other addictive substances to enhance the translational relevance of this model, as well as determine whether amelioration of these circuit disruptions can reduce substance use behavior.

Understanding the Role of the Gut Microbiome in Brain Development and Its Association With Neurodevelopmental Psychiatric Disorders

The gut microbiome has a tremendous influence on human physiology, including the nervous system. During fetal development, the initial colonization of the microbiome coincides with the development of the nervous system in a timely, coordinated manner. Emerging studies suggest an active involvement of the microbiome and its metabolic by-products in regulating early brain development. However, any disruption during this early developmental process can negatively impact brain functionality, leading to a range of neurodevelopment and neuropsychiatric disorders (NPD). In this review, we summarize recent evidence as to how the gut microbiome can influence the process of early human brain development and its association with major neurodevelopmental psychiatric disorders such as autism spectrum disorders, attention-deficit hyperactivity disorder, and schizophrenia. Further, we discuss how gut microbiome alterations can also play a role in inducing drug resistance in the affected individuals. We propose a model that establishes a direct link of microbiome dysbiosis with the exacerbated inflammatory state, leading to functional brain deficits associated with NPD. Based on the existing research, we discuss a framework whereby early diet intervention can boost mental wellness in the affected subjects and call for further research for a better understanding of mechanisms that govern the gut-brain axis may lead to novel approaches to the study of the pathophysiology and treatment of neuropsychiatric disorders.

Maternal gut bacteria drive intestinal inflammation in offspring with neurodevelopmental disorders by altering the chromatin landscape of CD4+ T cells

Children with autism spectrum disorders often display dysregulated immune responses and related gastrointestinal symptoms. However, the underlying mechanisms leading to the development of both phenotypes have not been elucidated. Here, we show that mouse offspring exhibiting autism-like phenotypes due to prenatal exposure to maternal inflammation were more susceptible to developing intestinal inflammation following challenges later in life. In contrast to its prenatal role in neurodevelopmental phenotypes, interleukin-17A (IL-17A) generated immune-primed phenotypes in offspring through changes in the maternal gut microbiota that led to postnatal alterations in the chromatin landscape of naive CD4+ T cells. The transfer of stool samples from pregnant mice with enhanced IL-17A responses into germ-free dams produced immune-primed phenotypes in offspring. Our study provides mechanistic insights into why children exposed to heightened inflammation in the womb might have an increased risk of developing inflammatory diseases in addition to neurodevelopmental disorders.

LPS vs. Poly I:C Model: Comparison of Long-Term Effects of Bacterial and Viral Maternal Immune Activation (MIA) on the Offspring

A prominent health issue nowadays is the COVID-19 pandemic, which poses acute risks to human health. However, the long-term health consequences are largely unknown and cannot be neglected. An especially vulnerable period for infection is pregnancy, when infections could have long-term health effect on the child. Evidence suggests that maternal immune activation (MIA) induced by either bacteria or viruses presents various effects on the offspring, leading to adverse phenotypes in many organ systems. This review compares the mechanisms of bacterial and viral MIA and the possible long-term outcomes for the offspring by summarizing the outcome in animal LPS and Poly I:C models. Both models are activated immune responses mediated by Toll-like receptors. The outcomes for MIA offspring include neurodevelopment, immune response, circulation, metabolism, and reproduction. Some of these changes continue to exist until later life. Besides different doses and batches of LPS and Poly I:C, the injection day, administration route, and also different animal species influence the outcomes. Here, we specifically aim to support colleagues when choosing their animal models for future studies.

Maternal Immune Activation Causes Social Behavior Deficits and Hypomyelination in Male Rat Offspring with an Autism-Like Microbiota Profile

Maternal immune activation (MIA) increases the risk of autism spectrum disorder (ASD) in offspring. Microbial dysbiosis is associated with ASD symptoms. However, the alterations in the brain-gut-microbiota axis in lipopolysaccharide (LPS)-induced MIA offspring remain unclear. Here, we examined the social behavior, anxiety-like and repetitive behavior, microbiota profile, and myelination levels in LPS-induced MIA rat offspring. Compared with control offspring, MIA male rat offspring spent less time in an active social interaction with stranger rats, displayed more anxiety-like and repetitive behavior, and had more hypomyelination in the prefrontal cortex and thalamic nucleus. A fecal microbiota analysis revealed that MIA offspring had a higher abundance of Alistipes, Fusobacterium, and Ruminococcus and a lower abundance of Coprococcus, Erysipelotrichaies, and Actinobacteria than control offspring, which is consistent with that of humans with ASD. The least absolute shrinkage and selection operator (LASSO) method was applied to determine the relative importance of the microbiota, which indicated that the abundance of Alistipes and Actinobacteria was the most relevant for the profile of defective social behavior, whereas Fusobacterium and Coprococcus was associated with anxiety-like and repetitive behavior. In summary, LPS-induced MIA offspring showed an abnormal brain-gut-microbiota axis with social behavior deficits, anxiety-like and repetitive behavior, hypomyelination, and an ASD-like microbiota profile.

Maternal immune activation alters adult behavior, intestinal integrity, gut microbiota and the gut inflammation

BACKGROUND

Schizophrenia is characterized by several core behavioral features, in which the gastrointestinal symptoms are frequently reported. Maternal immune activation (MIA) has been developed in a rodent model to study neurodevelopmental disorders such as schizophrenia. However, the changes in the gut environment of MIA rats remain largely unknown.

METHODS

10 mg/kg of polyinosinic:polycytidylic acid (Poly I:C) on gestational day 9 was intravenously administered to rats to induce MIA in order to assess changes in behavior, the intestinal barrier and microbiota in offspring.

RESULTS

Maternal immune activation offspring shown increased anxiety as indicated by reduced exploration of central area in open field test and decreased exploration of open arms in elevated plus test. Cognitive impairment of MIA offspring was confirmed by reduced exploration of novel arm in Y maze test and deficiency of PPI. Intestinal muscle thickness became thinner and some specific microbial anomalies previously identified clinically were observed in MIA offspring. In addition, an increase of inflammatory responses was found in the gut of MIA offspring.

CONCLUSIONS

Maternal immune activation alters behavior, intestinal integrity, gut microbiota and the gut inflammation in adult offspring.