Hyperactive behavior in female rats in utero-exposed to group B Streptococcus-induced inflammation

Neurodevelopmental impairment associated with neonatal invasive group B Streptococcus disease: Are animal models on track in understanding the mechanisms at play?

Invasive Group B Streptococcus (iGBS) disease is a prominent cause of neurodevelopmental impairment (NDI) in neonates. While the clinical manifestation of iGBS disease in neonates may include pneumonia and meningitis, generalised sepsis without focus is the most frequent manifestation of iGBS disease in neonates. Though recent human based studies highlighted meningitis as an important manifestation in infants with NDI following iGBS disease, they also noted that ∼18% of neonates present with NDI following iGBS related sepsis. Thus, it is important to not only understand the long-term pathophysiological changes associated with NDI in iGBS meningitis survivors, but so too for iGBS sepsis survivors. Since the late 1970's animal models have been used to unravel the pathophysiology of neonatal iGBS disease. These studies have inoculated neonatal or pregnant animals with GBS via various peripheral or central routes. The greatest challenge with using animal models to study NDI associated with neonatal iGBS disease, is effectively mimicking the clinical presentations of pneumonia, sepsis, and meningitis, while inducing relevant pathophysiological changes and ensuring animals survival, so as to test the neurodevelopment of the animals. This review aims to evaluate the validity of neonatal rodent models, specifically in studying NDI associated with neonatal iGBS disease and explore possible future avenues of research in addressing long-term NDI in the clinical setting.

Sex-Specific Dysconnective Brain Injuries and Neuropsychiatric Conditions such as Autism Spectrum Disorder Caused by Group B Streptococcus-Induced Chorioamnionitis

Global health efforts have increased against infectious diseases, but issues persist with pathogens like Group B Streptococcus (GBS). Preclinical studies have elaborated on the mechanistic process of GBS-induced chorioamnionitis and its impact on the fetal programming of chronic neuropsychiatric diseases. GBS inoculation in rodents demonstrated the following: (i) silent and self-limited placental infection, similar to human chorioamnionitis; (ii) placental expression of chemokines attracting polymorphonuclear (PMN) cells; (iii) in vitro cytokine production; (iv) PMN infiltration in the placenta (histologic hallmark of human chorioamnionitis), linked to neurobehavioral impairments like cerebral palsy and autism spectrum disorders (ASD); (v) upregulation of interleukin-1β (IL-1β) in the placenta and fetal blood, associated with higher ASD risk in humans; (vi) sex-specific effects, with higher IL-1β release and PMN recruitment in male placenta; (vii) male offspring exhibiting ASD-like traits, while female offspring displayed attention deficit and hyperactivity disorder (ADHD)-like traits; (viii) IL-1 and/or NF-kB blockade alleviate placental and fetal inflammation, as well as subsequent neurobehavioral impairments. These findings offer potential therapeutic avenues, including sex-adapted anti-inflammatory treatment (e.g., blocking IL-1; repurposing of FDA-approved IL-1 receptor antagonist (IL-1Ra) treatment). Blocking the IL-1 pathway offers therapeutic potential to alleviate chorioamnionitis-related disabilities, presenting an opportunity for a human phase II RCT that uses IL-1 blockade added to the classic antibiotic treatment of chorioamnionitis.

Bacterial and Host Determinants of Group B Streptococcal Infection of the Neonate and Infant

Group B streptococci (GBS) are Gram-positive β-hemolytic bacteria that can cause serious and life-threatening infections in neonates manifesting as sepsis, pneumonia, meningitis, osteomyelitis, and/or septic arthritis. Invasive GBS infections in neonates in the first week of life are referred to as early-onset disease (EOD) and thought to be acquired by the fetus through exposure to GBS in utero or to vaginal fluids during birth. Late-onset disease (LOD) refers to invasive GBS infections between 7 and 89 days of life. LOD transmission routes are incompletely understood, but may include breast milk, household contacts, nosocomial, or community sources. Invasive GBS infections and particularly meningitis may result in significant neurodevelopmental injury and long-term disability that persists into childhood and adulthood. Globally, EOD and LOD occur in more than 300,000 neonates and infants annually, resulting in 90,000 infant deaths and leaving more than 10,000 infants with a lifelong disability. In this review, we discuss the clinical impact of invasive GBS neonatal infections and then summarize virulence and host factors that allow the bacteria to exploit the developing neonatal immune system and target organs. Specifically, we consider the mechanisms known to enable GBS invasion into the neonatal lung, blood vessels and brain. Understanding mechanisms of GBS invasion and pathogenesis relevant to infections in the neonate and infant may inform the development of therapeutics to prevent or mitigate injury, as well as improve risk stratification.

Protective Effects of Interleukin-1 Blockade on Group B Streptococcus-Induced Chorioamnionitis and Subsequent Neurobehavioral Impairments of the Offspring

Group B Streptococcus (GBS) is one of the most common bacteria isolated in human chorioamnionitis. Placental infection due to GBS is a major risk factor for fetal organ injuries, preterm birth, perinatal morbidity and mortality, and life-long multiorgan morbidities. Preclinical and clinical studies have shown that GBS-induced infection drives polymorphonuclear (PMN) cell infiltration within the placenta, the hallmark of human chorioamnionitis. In preclinical and clinical studies, the upregulation of interleukin(IL)-1β in the placenta and maternal/fetal blood was associated with a high risk of neurodevelopmental impairments in the progeny. We hypothesized that targeted IL-1 blockade administered to the dam alleviates GBS-induced chorioamnionitis and the downstream fetal inflammatory response syndrome (FIRS). IL-1 receptor antagonist (IL-1Ra) improved the gestational weight gain of GBS-infected dams and did not worsen the infectious manifestations. IL-1Ra reduced the IL-1β titer in the maternal sera of GBS-infected dams. IL-1Ra decreased the levels of IL-1β, IL-6, chemokine (C-X-C motif) ligand 1 (CXCL1), and polymorphonuclear (PMN) infiltration in GBS-infected placenta. IL-1Ra treatment reduced the IL-1β titer in the fetal sera of GBS-exposed fetuses. IL-1 blockade also alleviated GBS-induced FIRS and subsequent neurobehavioral impairments of the offspring without worsening the outcome of GBS infection. Altogether, these results showed that IL-1 plays a key role in the physiopathology of live GBS-induced chorioamnionitis and consequent neurobehavioral impairments.

Uvaol Prevents Group B Streptococcus-Induced Trophoblast Cells Inflammation and Possible Endothelial Dysfunction

Group B Streptococcus (GBS) infection during pregnancy is involved in maternal sepsis, chorioamnionitis, prematurity, fetal infection, neonatal sepsis, and neurodevelopmental alterations. The GBS-induced chorioamnionitis leads to a plethora of immune and trophoblast cells alterations that could influence endothelial cells to respond differently to angiogenic mediators and alter placental vascular structure and function in pregnant women. In this context, preventive measures are needed to reduce such dysfunctions. As such, we evaluated the effects of a non-lethal exposure to inactivated GBS on trophoblast cells and chorionic villi explants, and if the treatment with uvaol would mitigate these effects. The concentration of 10⁶ CFU of GBS was chosen since it was unable to reduce the HTR-8/SVneo cell line nor term chorionic villi explant viability. Raman spectroscopy of trophoblast cells showed significant alterations in their biochemical signature, mostly reverted by uvaol. GBS exposure increased HTR-8/SVneo cells IL-1β and IFN-γ production, phagocytosis, oxidative stress, and decreased trophoblast cell migration. The Ea.hy926 endothelial cell line produced angiopoietin-2, CXCL-8, EGF, FGF-b, IL-6, PlGF, sPECAM-1, and VEGF in culture. When co-cultured in invasion assay with HTR-8/SVneo trophoblast cells, the co-culture had increased production of angiopoietin-2, CXCL-8, FGF-b, and VEGF, while reduced sPECAM-1 and IL-6. GBS exposure led to increased CXCL-8 and IL-6 production, both prevented by uvaol. Chorionic villi explants followed the same patterns of production when exposed to GBS and response to uvaol treatment as well. These findings demonstrate that, even a non-lethal concentration of GBS causes placental inflammation and oxidative stress, reduces trophoblast invasion of endothelial cells, and increases CXCL-8 and IL-6, key factors that participate in vascular dysregulation observed in several diseases. Furthermore, uvaol treatment prevented most of the GBS-provoked changes. Hence, uvaol could prevent the harmful effects of GBS infection for both the mother and the fetus.

What Does Immunology Have to Do With Normal Brain Development and the Pathophysiology Underlying Tourette Syndrome and Related Neuropsychiatric Disorders?

Objective: The goal of this article is to review the past decade's literature and provide a critical commentary on the involvement of immunological mechanisms in normal brain development, as well as its role in the pathophysiology of Tourette syndrome, other Chronic tic disorders (CTD), and related neuropsychiatric disorders including Obsessive-compulsive disorder (OCD) and Attention deficit hyperactivity disorder (ADHD). Methods: We conducted a literature search using the Medline/PubMed and EMBASE electronic databases to locate relevant articles and abstracts published between 2009 and 2020, using a comprehensive list of search terms related to immune mechanisms and the diseases of interest, including both clinical and animal model studies. Results: The cellular and molecular processes that constitute our "immune system" are crucial to normal brain development and the formation and maintenance of neural circuits. It is also increasingly evident that innate and adaptive systemic immune pathways, as well as neuroinflammatory mechanisms, play an important role in the pathobiology of at least a subset of individuals with Tourette syndrome and related neuropsychiatric disorders In the conceptual framework of the holobiont theory, emerging evidence points also to the importance of the "microbiota-gut-brain axis" in the pathobiology of these neurodevelopmental disorders. Conclusions: Neural development is an enormously complex and dynamic process. Immunological pathways are implicated in several early neurodevelopmental processes including the formation and refinement of neural circuits. Hyper-reactivity of systemic immune pathways and neuroinflammation may contribute to the natural fluctuations of the core behavioral features of CTD, OCD, and ADHD. There is still limited knowledge of the efficacy of direct and indirect (i.e., through environmental modifications) immune-modulatory interventions in the treatment of these disorders. Future research also needs to focus on the key molecular pathways through which dysbiosis of different tissue microbiota influence neuroimmune interactions in these disorders, and how microbiota modification could modify their natural history. It is also possible that valid biomarkers will emerge that will guide a more personalized approach to the treatment of these disorders.

Prenatal risk factors for internalizing and externalizing problems in childhood

BACKGROUND

A growing body of research has documented the effects of prenatal risk factors on a wide spectrum of adverse offspring health outcomes. Childhood behavior problems, such as externalizing and internalizing problems, are no exception. This comprehensive literature review aims to summarize and synthesize current research about commonly experienced prenatal risk factors associated with internalizing and externalizing problems, with a focus on their impact during childhood and adolescence. Potential mechanisms as well as implications are also outlined.

DATA SOURCES

The EBSCO, Web of Science, PubMed, Google Scholar, and Scopus databases were searched for studies examining the association between prenatal risk factors and offspring internalizing/externalizing problems, using keywords "prenatal" or "perinatal" or "birth complications" in combination with "internalizing" or "externalizing". Relevant articles, including experimental research, systematic reviews, meta-analyses, cross-sectional and longitudinal cohort studies, and theoretical literature, were reviewed and synthesized to form the basis of this integrative review.

RESULTS

Prenatal risk factors that have been widely investigated with regards to offspring internalizing and externalizing problems encompass health-related risk factors, including maternal overweight/obesity, substance use/abuse, environmental toxicant exposure, maternal infection/inflammation, as well as psychosocial risk factors, including intimate partner violence, and anxiety/depression. Collectively, both epidemiological and experimental studies support the adverse associations between these prenatal factors and increased risk of emotional/behavioral problem development during childhood and beyond. Potential mechanisms of action underlying these associations include hormonal and immune system alterations. Implications include prenatal education, screening, and intervention strategies.

CONCLUSIONS

Prenatal risk factors are associated with a constellation of offspring internalizing and externalizing problems. Identifying these risk factors and understanding potential mechanisms will help to develop effective, evidence-based prevention, and intervention strategies.

Neuroinflammation as a risk factor for attention deficit hyperactivity disorder

Attention Deficit Hyperactivity Disorder (ADHD) is a persistent, and impairing pediatric-onset neurodevelopmental condition. Its high prevalence, and recurrent controversy over its widespread identification and treatment, drive strong interest in its etiology and mechanisms. Emerging evidence for a role for neuroinflammation in ADHD pathophysiology is of great interest. This evidence includes 1) the above-chance comorbidity of ADHD with inflammatory and autoimmune disorders, 2) initial studies indicating an association with ADHD and increased serum cytokines, 3) preliminary evidence from genetic studies demonstrating associations between polymorphisms in genes associated with inflammatory pathways and ADHD, 4) emerging evidence that early life exposure to environmental factors may increase risk for ADHD via an inflammatory mechanism, and 5) mechanistic evidence from animal models of maternal immune activation documenting behavioral and neural outcomes consistent with ADHD. Prenatal exposure to inflammation is associated with changes in offspring brain development including reductions in cortical gray matter volume and the volume of certain cortical areas -parallel to observations associated with ADHD. Alterations in neurotransmitter systems, including the dopaminergic, serotonergic and glutamatergic systems, are observed in ADHD populations. Animal models provide strong evidence that development and function of these neurotransmitters systems are sensitive to exposure to in utero inflammation. In summary, accumulating evidence from human studies and animal models, while still incomplete, support a potential role for neuroinflammation in the pathophysiology of ADHD. Confirmation of this association and the underlying mechanisms have become valuable targets for research. If confirmed, such a picture may be important in opening new intervention routes.

Microglia along sex lines: From brain colonization, maturation and function, to implication in neurodevelopmental disorders

In addition to their traditional role as immune sentinels, recent discoveries over the last decade have shown that microglial functions now include regulation of neuronal/glial cell migration, differentiation and maturation, as well as neuronal network formation. It was thus proposed that disruption of these microglial roles, during critical periods of brain development, could lead to the pathological onset of several neurodevelopmental disorders, including autism spectrum disorder, attention deficit hyperactivity disorder, epilepsy, schizophrenia, and major depressive disorder. The prevalence of these disorders exhibits a clear distinction along sex lines with very little known about the mechanisms underlying this difference. One of the fundamental discoveries that arose from recent research into the physiological roles of microglia in neurodevelopment is their sexual dimorphism, raising the intriguing possibility that sex differences in microglial colonization, maturation and/or function in the developing brain could underlie the emergence of various neurodevelopmental disorders. This review discusses the physiological roles of microglia across neurodevelopment, these roles in the two sexes, and the recent evidence that microglial sexually dimorphic nature may contribute, at least partially, to neurodevelopmental disorders.

Sex-specific maternofetal innate immune responses triggered by group B Streptococci

Group B Streptococcus (GBS) is one of the most common bacteria isolated in human chorioamnionitis, which is a major risk factor for premature birth and brain injuries. Males are at greater risk than females for developing lifelong neurobehavioural disorders, although the origins of this sex bias remain poorly understood. We previously showed that end-gestational inflammation triggered by GBS led to early neurodevelopmental impairments mainly in the male rat progeny. Identifying key inflammatory players involved in maternofetal immune activation by specific pathogens is critical to develop appropriate novel therapeutic interventions. We aimed to map out the GBS-induced profile of innate immune biomarkers in the maternal-placental-fetal axis, and to compare this immune profile between male and female tissues. We describe here that the GBS-induced immune signalling involved significantly higher levels of interleukin (IL)-1β, cytokine-induced neutrophil chemoattractant-1 (CINC-1/CXCL1) and polymorphonuclear cells (PMNs) infiltration in male compared to female maternofetal tissues. Although male - but not female - fetuses presented increased levels of IL-1β, fetuses from both sexes in-utero exposed to GBS had increased levels of TNF-α in their circulation. Levels of IL-1β detected in fetal sera correlated positively with the levels found in maternal circulation. Here, we report for the first time that the maternofetal innate immune signalling induced by GBS presents a sexually dichotomous profile, with more prominent inflammation in males than females. These sex-specific placental and fetal pro-inflammatory responses are in keeping with the higher susceptibility of the male population for preterm birth, brain injuries and neurodevelopmental disorders such as cerebral palsy and autism spectrum disorders.

Sex-Dependent Effects of Perinatal Inflammation on the Brain: Implication for Neuro-Psychiatric Disorders

Individuals born preterm have higher rates of neurodevelopmental disorders such as schizophrenia, autistic spectrum, and attention deficit/hyperactivity disorders. These conditions are often sexually dimorphic and with different developmental trajectories. The etiology is likely multifactorial, however, infections both during pregnancy and in childhood have emerged as important risk factors. The association between sex- and age-dependent vulnerability to neuropsychiatric disorders has been suggested to relate to immune activation in the brain, including complex interactions between sex hormones, brain transcriptome, activation of glia cells, and cytokine production. Here, we will review sex-dependent effects on brain development, including glia cells, both under normal physiological conditions and following perinatal inflammation. Emphasis will be given to sex-dependent effects on brain regions which play a role in neuropsychiatric disorders and inflammatory reactions that may underlie early-life programming of neurobehavioral disturbances later in life.

Histological Chorioamnionitis Induces Differential Gene Expression in Human Cord Blood Mononuclear Leukocytes from Term Neonates

Histological chorioamnionitis (HCA) is an infection of fetal membranes and complicates 5.2% to 28.5% of all live births. HCA is associated with increased mortality and morbidity in both premature and term neonates. Exposure to HCA may have long-term consequences, including an increased risk for allergic disorders and asthma later in childhood, the mechanism(s) of which are still not yet well understood. The objective of this study was to determine the mRNA transcriptome of cord blood mononuclear leukocytes from term neonates to identify key genes and pathways involved in HCA. We found 366 differentially expressed probe IDs with exposure to HCA (198 upregulated, 168 downregulated). These transcriptomes included novel genes and pathways associated with exposure to HCA. The differential gene expression included key genes regulating inflammatory, immune, respiratory and neurological pathways, which may contribute to disorders in those pathways in neonates exposed to HCA. Our data may lead to understanding of the role of key genes and pathways identified on the long-term sequelae related to exposure to HCA, as well as to identifying potential markers and therapies to prevent HCA-associated complications.