Invasion of brain microvascular endothelial cells by group B streptococci

Group B Streptococcus transcriptome when interacting with brain endothelial cells

Bacterial meningitis is a life-threatening infection of the central nervous system (CNS) that occurs when bacteria are able to cross the blood-brain barrier (BBB) or the meningeal-cerebrospinal fluid barrier (mBCSFB). The BBB and mBCSFB comprise highly specialized brain endothelial cells (BECs) that typically restrict pathogen entry. Group B Streptococcus (GBS or Streptococcus agalactiae) is the leading cause of neonatal meningitis. Until recently, identification of GBS virulence factors has relied on genetic screening approaches. Instead, we here conducted RNA-seq analysis on GBS when interacting with induced pluripotent stem cell-derived BECs (iBECs) to pinpoint virulence-associated genes. Of the 2,068 annotated protein-coding genes of GBS, 430 transcripts displayed significant changes in expression after interacting with BECs. Notably, we found that the majority of differentially expressed GBS transcripts were downregulated (360 genes) during infection of iBECs. Interestingly, codY, encoding a pleiotropic transcriptional repressor in low-G + C Gram-positive bacteria, was identified as being highly downregulated. We conducted qPCR to confirm the codY downregulation observed via RNA-seq during the GBS-iBEC interaction and obtained codY mutants in three different GBS background parental strains. As anticipated from the RNA-seq results, the [Formula: see text]codY strains were more adherent and invasive in two in vitro BEC models. Together, this demonstrates the utility of RNA-seq during the BEC interaction to identify GBS virulence modulators.

IMPORTANCE

Group B Streptococcus (GBS) meningitis remains the leading cause of neonatal meningitis. Research work has identified surface factors and two-component systems that contribute to GBS disruption of the blood-brain barrier (BBB). These discoveries often relied on genetic screening approaches. Here, we provide transcriptomic data describing how GBS changes its transcriptome when interacting with brain endothelial cells. Additionally, we have phenotypically validated these data by obtaining mutants of a select regulator that is highly down-regulated during infection and testing on our BBB model. This work provides the research field with a validated data set that can provide an insight into potential pathways that GBS requires to interact with the BBB and open the door to new discoveries.

Bacterial and host factors involved in zoonotic Streptococcal meningitis

Zoonotic streptococci cause several invasive diseases with high mortality rates, especially meningitis. Numerous studies elucidated the meningitis pathogenesis of zoonotic streptococci, some specific to certain bacterial species. In contrast, others are shared among different bacterial species, involving colonization and invasion of mucosal barriers, survival in the bloodstream, breaching the blood-brain and/or blood-cerebrospinal fluid barrier to access the central nervous system, and triggering inflammation of the meninges. This review focuses on the recent advancements in comprehending the molecular and cellular events of five major zoonotic streptococci responsible for causing meningitis in humans or animals, including Streptococcus agalactiae, Streptococcus equi subspecies zooepidemicus, Streptococcus suis, Streptococcus dysgalactiae, and Streptococcus iniae. The underlying mechanism was summarized into four themes, including 1) bacterial survival in blood, 2) brain microvascular endothelial cell adhesion and invasion, 3) penetration of the blood-brain barrier, and 4) activation of the immune system and inflammatory reaction within the brain. This review may contribute to developing therapeutics to prevent or mitigate injury of streptococcal meningitis and improve risk stratification.

An unusual imaging presentation of pediatric bacterial meningoencephalitis: a case-report study

Background

Bacterial meningoencephalitis is a serious infection affecting the brain and its surrounding membranes. While imaging studies play a crucial role in diagnosing this condition, the typical radiological findings are well-documented. However, this case report describes an unusual imaging presentation that deviates from the expected patterns, emphasizing the need for awareness of such variations.

Case presentation

A 7-year-old female with no prior medical history was referred to our hospital with fever, seizure, and loss of Consciousness. She had mild flu a week before admission. The duration of seizure episodes were 2-3 min, with tonic-clonic uncontrollable jerky movements. Brudzinski and Kernig signs were positive and plantar reflex was upward bilaterally in the physical examination. The computed tomography (CT) scan showed brain ventriculomegaly/hydrocephalus, and MRI findings indicated multiple foci located at cerebellum, basal ganglia, and thalamus alongside intensely restricted diffusion of the layering debris, suggesting pyogenic ventriculitis. Cerebrospinal fluid (CSF) analysis showed severe hypoglycorrhachia, despite non-significant increase of protein. The patient was undergone antibiotic therapy with ceftriaxone, vancomycin and rifampin, resulting in normalization of CSF values.

Conclusion

This case report highlights the importance of recognizing and interpreting unusual imaging presentations of bacterial meningoencephalitis in paediatric patients. It emphasizes the need for a comprehensive diagnostic approach, including clinical evaluation, laboratory tests, and imaging studies, to ensure accurate diagnosis and appropriate management of this potentially life-threatening condition. Further research and awareness of atypical imaging findings are warranted to enhance our understanding and improve patient outcomes.

Host-microbe interactions at the blood-brain barrier through the lens of induced pluripotent stem cell-derived brain-like endothelial cells

Microbe-induced meningoencephalitis/meningitis is a life-threatening infection of the central nervous system (CNS) that occurs when pathogens are able to cross the blood-brain barrier (BBB) and gain access to the CNS. The BBB consists of highly specialized brain endothelial cells that exhibit specific properties to allow tight regulation of CNS homeostasis and prevent pathogen crossing. However, during meningoencephalitis/meningitis, the BBB fails to protect the CNS. Modeling the BBB remains a challenge due to the specialized characteristics of these cells. In this review, we cover the induced pluripotent stem cell-derived, brain-like endothelial cell model during host-pathogen interaction, highlighting the strengths and recent work on various pathogens known to interact with the BBB. As stem cell technologies are becoming more prominent, the stem cell-derived, brain-like endothelial cell model has been able to reveal new insights in vitro, which remain challenging with other in vitro cell-based models consisting of primary human brain endothelial cells and immortalized human brain endothelial cell lines.

Spatial profiling of the placental chorioamniotic membranes reveals upregulation of immune checkpoint proteins during Group B Streptococcus infection in a nonhuman primate model

Background

Preterm birth is a leading cause of neonatal mortality, which is often complicated by intrauterine infection and inflammation. We have established a nonhuman primate model of Group B Streptococcus (GBS, Streptococcus agalactiae) infection-associated preterm birth. Immune checkpoints are modulators of the immune response by activating or suppressing leukocyte function and are understudied in preterm birth. The objective of this study was to spatially profile changes in immune protein expression at the maternal-fetal interface during a GBS infection with a focus on immune checkpoints.

Methods

Twelve nonhuman primates (pigtail macaques, Macaca nemestrina) received a choriodecidual inoculation of either: 1) 1-5 X 108 colony forming units (CFU) of hyperhemolytic/hypervirulent GBS (GBSΔcovR, N=4); 2) an isogenic/nonpigmented strain (GBS ΔcovRΔcylE, N=4); or, 3) saline (N=4). A Cesarean section was performed at preterm labor or 3 days after GBS infection or 7 days after saline inoculation. Nanostring GeoMx® Digital Spatial Profiling technology was used to segment protein expression within the amnion, chorion, and maternal decidua at the inoculation site using an immuno-oncology panel targeting 56 immunoproteins enriched in stimulatory and inhibitory immune checkpoint proteins or their protein ligands. Statistical analysis included R studio, Kruskal-Wallis, Pearson and Spearman tests.

Results

Both inhibitory and stimulatory immune checkpoint proteins were significantly upregulated within the chorioamniotic membranes and decidua (VISTA, LAG3, PD-1, CD40, GITR), as well as their ligands (PD-L1, PD-L2, CD40L; all p<0.05). Immunostaining for VISTA revealed positive (VISTA+) cells, predominantly in the chorion and decidua. There were strong correlations between VISTA and amniotic fluid concentrations of IL-1β, IL-6, IL-8, and TNF-α (all p<0.05), as well as maternal placental histopathology scores (p<0.05).

Conclusion

Differential regulation of multiple immune checkpoint proteins in the decidua at the site of a GBS infection indicates a major perturbation in immunologic homeostasis that could benefit the host by restricting immune-driven pathologies or the pathogen by limiting immune surveillance. Protein expression of VISTA, an inhibitory immune checkpoint, was upregulated in the chorion and decidua after GBS infection. Investigating the impact of innate immune cell expression of inhibitory immune checkpoints may reveal new insights into placental host-pathogen interactions at the maternal-fetal interface.

Blood-brain barrier dysfunction in intensive care unit

The central nervous system is characterized by a peculiar vascularization termed blood-brain barrier (BBB), which regulates the exchange of cells and molecules between the cerebral tissue and the whole body. BBB dysfunction is a life-threatening condition since its presence corresponds to a marker of severity in most diseases encountered in the intensive care unit (ICU). During critical illness, inflammatory response, cytokine release, and other phenomena activating the brain endothelium contribute to alterations in the BBB and increase its permeability to solutes, cells, nutrients, and xenobiotics. Moreover, patients in the ICU are often old, with underlying acute or chronic diseases, and overly medicated due to their critical condition; these factors could also contribute to the development of BBB dysfunction. An accurate diagnostic approach is critical for the identification of the mechanisms underlying BBB alterations, which should be rapidly managed by intensivists. Several methods were developed to investigate the BBB and assess its permeability. Nevertheless, in humans, exploration of the BBB requires the use of indirect methods. Imaging and biochemical methods can be used to study the abnormal passage of molecules through the BBB. In this review, we describe the structural and functional characteristics of the BBB, present tools and methods for probing this interface, and provide examples of the main diseases managed in the ICU that are related to BBB dysfunction.

Cholesterol dependent cytolysins and the brain: Revealing a potential therapeutic avenue for bacterial meningitis

Bacterial meningitis is a catastrophic nervous system disorder with high mortality and wide range of morbidities. Some of the meningitis-causing bacteria occupy cholesterol dependent cytolysins (CDCs) to increase their pathogenicity and arrange immune-evasion strategy. Studies have observed that the relationship between CDCs and pathogenicity in these meningitides is complex and involves interactions between CDC, blood-brain barrier (BBB), glial cells and neurons. In BBB, these CDCs acts on capillary endothelium, tight junction (TJ) proteins and neurovascular unit (NVU). CDCs also observed to elicit intriguing effects on brain inflammation which involves microglia and astrocyte activations, along with neuronal damage as the end-point of pathological pathways in bacterial meningitis. As some studies mentioned potential advantage of CDC-targeted therapeutic mechanisms to combat CNS infections, it might be a fruitful avenue to deepen our understanding of CDC as a candidate for adjuvant therapy to combat bacterial meningitis.

The Pathological Activation of Microglia Is Modulated by Sexually Dimorphic Pathways

Microglia are the primary immunocompetent cells of the central nervous system (CNS). Their ability to survey, assess and respond to perturbations in their local environment is critical in their role of maintaining CNS homeostasis in health and disease. Microglia also have the capability of functioning in a heterogeneous manner depending on the nature of their local cues, as they can become activated on a spectrum from pro-inflammatory neurotoxic responses to anti-inflammatory protective responses. This review seeks to define the developmental and environmental cues that support microglial polarization towards these phenotypes, as well as discuss sexually dimorphic factors that can influence this process. Further, we describe a variety of CNS disorders including autoimmune disease, infection, and cancer that demonstrate disparities in disease severity or diagnosis rates between males and females, and posit that microglial sexual dimorphism underlies these differences. Understanding the mechanism behind differential CNS disease outcomes between men and women is crucial in the development of more effective targeted therapies.

Exosome-Coated tPA/Catalase Nanoformulation for Thrombolytic Therapy

Current tissue plasminogen-based therapeutic strategies for stroke suffer from systemic side effects and poor efficacy. Hence, novel drug delivery methods are needed to overcome these shortcomings. Exosome-based drug formulations have been shown to have superior therapeutic outcomes compared to conventional systemic drug delivery approaches. In this paper, we report exosome surface-coated tissue plasminogen activator (tPA)/catalase nanoformulations with improved thrombolytic efficacy compared to free tPA, which also reduce side effects. The results showed that the tPA exosome formulations retained tPA activity, improved tPA stability, exhibited significant fibrinolysis, and showed no significant toxicity effects. Further, when combined with antioxidant enzyme catalase, the formulation was able to inhibit hydrogen peroxide-mediated oxidative stress and toxicity. Hence, exosome-based tPA/catalase nanoformulations could have the potential to offer a safer and effective thrombolytic therapy.

Pediatric neuropsychiatric disorders with motor and nonmotor phenomena

The concept of pediatric autoimmune neuropsychiatric disorders associated with group A beta-hemolytic streptococcus (PANDAS) has become seminal since first introduced more than two decades ago. At the time of this writing, most neurologists, pediatricians, psychiatrists, and general pediatricians will probably have heard of this association or treated an affected child with PANDAS. The concept of an acute-onset, and typically self-limited, postinfectious autoimmune neuropsychiatric disorder resembling PANDAS manifesting vocal and motor tics and obsessive-compulsive disorder has broadened to other putative microbes and related endogenous and exogenous disease triggers. These disorders with common features of hypometabolism in the medial temporal lobe and hippocampus in brain 18fluorodeoxyglucose positron emission tomography fused to magnetic resonance imaging (FDG PET-MRI), form a spectrum: with the neuropsychiatric disorder Tourette syndrome and PANDAS with its well-defined etiopathogenesis at one end, and pediatric abrupt-onset neuropsychiatric syndrome (PANS), alone or associated with specific bacterial and viral pathogens, at the other end. The designation of PANS in the absence of a specific trigger, as an exclusionary diagnosis, reflects the current problem in nosology.

Akt Inhibition Promotes Autophagy and Clearance of Group B Streptococcus from the Alveolar Epithelium

Group B Streptococcus (GBS) is a gram-positive bacterium that is harmless for healthy individuals but may provoke invasive disease in young infants and immunocompromised hosts. GBS invades the epithelial barriers to enter the bloodstream, and thus strategies that enhance epithelial cell responses may hamper GBS invasion. In the present study, we sought to investigate whether the inhibition of Akt, a kinase that regulates host inflammatory responses and autophagy via suppression of mTOR, can enhance the response of non-phagocytic alveolar epithelial cells against GBS. Treatment of the alveolar epithelial cell line A549 with the Akt inhibitor MK-2206 resulted in the enhanced production of reactive oxygen species and inflammatory mediators in response to GBS. Additionally, Akt inhibition via MK-2206 resulted in elevated LC3II/I ratios and increased autophagic flux in alveolar epithelial cells. Importantly, the inhibition of Akt promoted GBS clearance both in alveolar epithelial cells in vitro and in lung tissue in vivo in a murine model of GBS pneumonia. The induction of autophagy was essential for GBS clearance in MK-2206 treated cells, as knockdown of ATG5, a critical component of autophagy, abrogated the effect of Akt inhibition on GBS clearance. Our findings highlight the role of Akt kinase inhibition in promoting autophagy and GBS clearance in the alveolar epithelium. The inhibition of Akt may serve as a promising measure to strengthen epithelial barriers and prevent GBS invasion in susceptible hosts.

Nitric Oxide Production and Effects in Group B Streptococcus Chorioamnionitis

Intrauterine infection, or chorioamnionitis, due to group B Streptococcus (GBS) is a common cause of miscarriage and preterm birth. To cause chorioamnionitis, GBS must bypass maternal-fetal innate immune defenses including nitric oxide (NO), a microbicidal gas produced by nitric oxide synthases (NOS). This study examined placental NO production and its role in host-pathogen interactions in GBS chorioamnionitis. In a murine model of ascending GBS chorioamnionitis, placental NOS isoform expression quantified by RT-qPCR revealed a four-fold expression increase in inducible NOS, no significant change in expression of endothelial NOS, and decreased expression of neuronal NOS. These NOS expression results were recapitulated ex vivo in freshly collected human placental samples that were co-incubated with GBS. Immunohistochemistry of wild type C57BL/6 murine placentas with GBS chorioamnionitis demonstrated diffuse inducible NOS expression with high-expression foci in the junctional zone and areas of abscess. Pregnancy outcomes between wild type and inducible NOS-deficient mice did not differ significantly although wild type dams had a trend toward more frequent preterm delivery. We also identified possible molecular mechanisms that GBS uses to survive in a NO-rich environment. In vitro exposure of GBS to NO resulted in dose-dependent growth inhibition that varied by serovar. RNA-seq on two GBS strains with distinct NO resistance phenotypes revealed that both GBS strains shared several detoxification pathways that were differentially expressed during NO exposure. These results demonstrate that the placental immune response to GBS chorioamnionitis includes induced NO production and indicate that GBS activates conserved stress pathways in response to NO exposure.

Construction of Streptococcus agalactiae sialic acid mutant and evaluation of its potential as a live attenuated vaccine in Nile tilapia (Oreochromis niloticus)

AIMS

This study aimed to develop a live attenuated vaccine as an effective approach to prevent streptococcosis in tilapia (Oreochromis niloticus).

METHODS AND RESULTS

We eliminated the virulence factor, sialic acid (Sia) encoded by the neuA-D gene cluster from the Group B Streptococcus (Streptococcus agalactiae, GBS) strain WC1535, to construct Sia-deficient S. agalactiae (ΔSia) mutant by homologous recombination. Results showed that the ΔSia mutant had higher adherence to HEp-2 cells and lower resistance to RAW264.7 cell phagocytosis than the wild-type S. agalactiae. The virulence of the ΔSia mutant to tilapia dramatically decreased with no virulence recovery. The relative percent survivals (RPSs) were 50.00% and 54.50% at 30 days when challenged at the wild-type WC1535 doses of 1.0 × 10⁷ and 5.0 × 10⁷ CFU fish^-1 , respectively, via intraperitoneal (IP) injection. The tilapia vaccinated via IP injection with the ΔSia mutant induced strong antibody agglutination titers. The expression of IL-1β, TNF-α, MHC-Iα, and MHC-IIβ could be enhanced in the intestine, spleen, and head kidney for tilapia administered with the ΔSia mutant.

CONCLUSIONS

GBS Sia plays a critical role in adherence to HEp-2 cells and resistance to the immune clearance of RAW264.7 cells. Moreover, the ΔSia mutant is a safe, stable, and immunogenic live attenuated vaccine candidate to protect tilapia against GBS infection.

SIGNIFICANCE AND IMPACT OF STUDY

The results offer more evidence of the importance of Sia in GBS and may be instructive in the control of tilapia streptococcosis.

Group B Streptococcal Neonatal Meningitis

Neonatal bacterial meningitis is a devastating disease, associated with high mortality and neurological disability, in both developed and developing countries. Streptococcus agalactiae, commonly referred to as group B Streptococcus (GBS), remains the most common bacterial cause of meningitis among infants younger than 90 days. Maternal colonization with GBS in the gastrointestinal and/or genitourinary tracts is the primary risk factor for neonatal invasive disease. Despite prophylactic intrapartum antibiotic administration to colonized women and improved neonatal intensive care, the incidence and morbidity associated with GBS meningitis have not declined since the 1970s. Among meningitis survivors, a significant number suffer from complex neurological or neuropsychiatric sequelae, implying that the pathophysiology and pathogenic mechanisms leading to brain injury and devastating outcomes are not yet fully understood. It is imperative to develop new therapeutic and neuroprotective approaches aiming at protecting the developing brain. In this review, we provide updated clinical information regarding the understanding of neonatal GBS meningitis, including epidemiology, diagnosis, management, and human evidence of the disease's underlying mechanisms. Finally, we explore the experimental models used to study GBS meningitis and discuss their clinical and physiologic relevance to the complexities of human disease.

Group B Streptococcus-Induced Macropinocytosis Contributes to Bacterial Invasion of Brain Endothelial Cells

Bacterial meningitis is defined as serious inflammation of the central nervous system (CNS) in which bacteria infect the blood–brain barrier (BBB), a network of highly specialized brain endothelial cells (BECs). Dysfunction of the BBB is a hallmark of bacterial meningitis. Group B Streptococcus (GBS) is one of the leading organisms that cause bacterial meningitis, especially in neonates. Macropinocytosis is an actin-dependent form of endocytosis that is also tightly regulated at the BBB. Previous studies have shown that inhibition of actin-dependent processes decreases bacterial invasion, suggesting that pathogens can utilize macropinocytotic pathways for invasion. The purpose of this project is to study the factors that lead to dysfunction of the BBB. We demonstrate that infection with GBS increases rates of endocytosis in BECs. We identified a potential pathway, PLC-PKC-Nox2, in BECs that contributes to macropinocytosis regulation. Here we demonstrate that downstream inhibition of PLC, PKC, or Nox2 significantly blocks GBS invasion of BECs. Additionally, we show that pharmacological activation of PKC can turn on macropinocytosis and increase bacterial invasion of nonpathogenic yet genetically similar Lactococcus lactis. Our results suggest that GBS activates BEC signaling pathways that increase rates of macropinocytosis and subsequently the invasion of GBS.

Endothelial Transcytosis in Acute Lung Injury: Emerging Mechanisms and Therapeutic Approaches

Acute Lung Injury (ALI) is characterized by widespread inflammation which in its severe form, Acute Respiratory Distress Syndrome (ARDS), leads to compromise in respiration causing hypoxemia and death in a substantial number of affected individuals. Loss of endothelial barrier integrity, pneumocyte necrosis, and circulating leukocyte recruitment into the injured lung are recognized mechanisms that contribute to the progression of ALI/ARDS. Additionally, damage to the pulmonary microvasculature by Gram-negative and positive bacteria or viruses (e.g., Escherichia coli, SARS-Cov-2) leads to increased protein and fluid permeability and interstitial edema, further impairing lung function. While most of the vascular leakage is attributed to loss of inter-endothelial junctional integrity, studies in animal models suggest that transendothelial transport of protein through caveolar vesicles, known as transcytosis, occurs in the early phase of ALI/ARDS. Here, we discuss the role of transcytosis in healthy and injured endothelium and highlight recent studies that have contributed to our understanding of the process during ALI/ARDS. We also cover potential approaches that utilize caveolar transport to deliver therapeutics to the lungs which may prevent further injury or improve recovery.

A group B Streptococcus alpha-like protein subunit vaccine induces functionally active antibodies in humans targeting homotypic and heterotypic strains

Maternal vaccination is a promising strategy for preventing neonatal disease caused by group B Streptococcus. The safety and immunogenicity of the prototype vaccine GBS-NN, a fusion protein consisting of the N-terminal domains of the alpha-like proteins (Alp) αC and Rib, were recently evaluated favorably in healthy adult women in a phase 1 trial. Here we demonstrate robust immunoglobulin G (IgG) and immunoglobulin A (IgA) responses against αC and Rib, as well as against the heterotypic Alp family members Alp1–Alp3. IgA and heterotypic IgG responses are more variable between subjects and correlate with pre-existing immunity. Vaccine-induced IgG mediates opsonophagocytic killing and prevents bacterial invasion of epithelial cells. Like the vaccine-induced response, naturally acquired IgG against the vaccine domains is dominated by IgG1. Consistent with the high IgG1 cross-placental transfer rate, naturally acquired IgG against both domains reaches higher concentrations in neonatal than maternal blood, as assessed in a separate group of non-vaccinated pregnant women and their babies.

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GBS-NN subunit vaccine broadly elicits IgG1 to homotypic αC and Rib N-terminal domains

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IgA and heterotypic IgG responses occur in vaccinees with pre-existing immunity

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Abs mediate opsonophagocytic killing and prevent bacterial epithelial cell invasion

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IgG against αC-N and Rib-N is transferred efficiently across the placenta

Induced Pluripotent Stem Cell (iPSC)-Derived Endothelial Cells to Study Bacterial-Brain Endothelial Cell Interactions

Bacterial meningitis is a serious infection of the central nervous system (CNS) that occurs when blood-borne bacteria are able to exit the cerebral vasculature and cause inflammation. The blood-brain barrier (BBB) and the meningeal blood-CSF barrier (mBCSFB) are composed of highly specialized brain endothelial cells (BECs) that possess unique phenotypes when compared to their peripheral endothelial counterparts. To cause meningitis, bacterial pathogens must be able to interact and penetrate these specialized BECs to gain access to the CNS. In vitro models have been employed to study bacterial-BEC interactions; however, many lack BEC phenotypes. Induced pluripotent stem cell (iPSC) technologies have enabled the derivation of brain endothelial-like cells that phenocopy BECs in culture. Recently, these iPSC-BECs have been employed to examine the host-pathogen interaction at the endothelial brain barriers. Using two clinically relevant human meningeal pathogens, this chapter describes the use of iPSC-BECs to study various aspects of BEC-bacterial interaction.

CC17 group B Streptococcus exploits integrins for neonatal meningitis development

Group B Streptococcus (GBS) is the major cause of human neonatal infections. A single clone, designated CC17-GBS, accounts for more than 80% of meningitis cases, the most severe form of the infection. However, the events allowing blood-borne GBS to penetrate the brain remain largely elusive. In this study, we identified the host transmembrane receptors α5β1 and αvβ3 integrins as the ligands of Srr2, a major CC17-GBS-specific adhesin. Two motifs located in the binding region of Srr2 were responsible for the interaction between CC17-GBS and these integrins. We demonstrated in a blood-brain-barrier cellular model that both integrins contributed to the adhesion and internalization of CC17-GBS. Strikingly, both integrins were overexpressed during the postnatal period in the brain vessels of the blood-brain barrier and blood-cerebrospinal fluid barrier and contributed to juvenile susceptibility to CC17 meningitis. Finally, blocking these integrins decreased the ability of CC17-GBS to cross into the CNS of juvenile mice in an in vivo model of meningitis. Our study demonstrated that CC17-GBS exploits integrins in order to cross the brain vessels, leading to meningitis. Importantly, it provides host molecular insights into neonate's susceptibility to CC17-GBS meningitis, thereby opening new perspectives for therapeutic and prevention strategies of GBS-elicited meningitis.

Vaginal Microbiota of the Sexually Transmitted Infections Caused by Chlamydia trachomatis and Trichomonas vaginalis in Women with Vaginitis in Taiwan

The three most common sexually transmitted infections (STIs) are Chlamydia trachomatis (CT), Neisseria gonorrhoeae (GC) and Trichomonas vaginalis (TV). The prevalence of these STIs in Taiwan remains largely unknown and the risk of STI acquisition affected by the vaginal microbiota is also elusive. In this study, a total of 327 vaginal swabs collected from women with vaginitis were analyzed to determine the presence of STIs and the associated microorganisms by using the BD Max CT/GC/TV molecular assay, microbial cultures, and 16S rRNA sequencing. The prevalence of CT, TV, and GC was 10.8%, 2.2% and 0.6%, respectively. A culture-dependent method identified that Escherichia coli and Streptococcus agalactiae (GBS) were more likely to be associated with CT and TV infections. In CT-positive patients, the vaginal microbiota was dominated by L. iners, and the relative abundance of Gardnerella vaginalis (12.46%) was also higher than that in TV-positive patients and the non-STIs group. However, Lactobacillus spp. was significantly lower in TV-positive patients, while GBS (10.11%), Prevotella bivia (6.19%), Sneathia sanguinegens (12.75%), and Gemella asaccharolytica (5.31%) were significantly enriched. Using an in vitro co-culture assay, we demonstrated that the growth of L. iners was suppressed in the initial interaction with TV, but it may adapt and survive after longer exposure to TV. Additionally, it is noteworthy that TV was able to promote GBS growth. Our study highlights the vaginal microbiota composition associated with the common STIs and the crosstalk between TV and the associated bacteria, paving the way for future development of health interventions targeting the specific vaginal bacterial taxa to reduce the risk of common STIs.

Bacteria elevate extracellular adenosine to exploit host signaling for blood-brain barrier disruption

Bacterial meningitis remains a substantial cause of mortality worldwide and survivors may have severe lifelong disability. Although we know that meningeal bacterial pathogens must cross blood-central nervous system (CNS) barriers, the mechanisms which facilitate the virulence of these pathogens are poorly understood. Here, we show that adenosine from a surface enzyme (Ssads) of Streptococcus suis facilitates this pathogen’s entry into mouse brains. Monolayer translocation assays (from the human cerebrovascular endothelium) and experiments using diverse inhibitors and agonists together demonstrate that activation of the A1 adenosine receptor signaling cascade in hosts, as well as attendant cytoskeleton remodeling, promote S. suis penetration across blood-CNS barriers. Importantly, our additional findings showing that Ssads orthologs from other bacterial species also promote their translocation across barriers suggest that exploitation of A1 AR signaling may be a general mechanism of bacterial virulence.

Research Advances on Tilapia Streptococcosis

Streptococcus agalactiae, often referred to as group B streptococci (GBS), is a severe pathogen that can infect humans as well as other animals, including tilapia, which is extremely popular in commercial aquaculture. This pathogen causes enormous pecuniary loss, and typical symptoms of streptococcosis—the disease caused by S. agalactiae—include abnormal behavior, exophthalmos, and meningitis, among others. Multiple studies have examined virulence factors associated with S. agalactiae infection, and vaccines were explored, including studies of subunit vaccines. Known virulence factors include capsular polysaccharide (CPS), hemolysin, Christie-Atkins-Munch-Peterson (CAMP) factor, hyaluronidase (HAase), superoxide dismutase (SOD), and serine-threonine protein kinase (STPK), and effective vaccine antigens reported to date include GapA, Sip, OCT, PGK, FbsA, and EF-Tu. In this review, I summarize findings from several studies about the etiology, pathology, virulence factors, and vaccine prospects for S. agalactiae. I end by considering which research areas are likely to yield success in the prevention and treatment of tilapia streptococcosis.

Therapeutic development of group B Streptococcus meningitis by targeting a host cell signaling network involving EGFR

Group B Streptococcus (GBS) remains the most common Gram-positive bacterium causing neonatal meningitis and GBS meningitis continues to be an important cause of mortality and morbidity. In this study, we showed that GBS penetration into the brain occurred initially in the meningeal and cortex capillaries, and exploits a defined host cell signaling network comprised of S1P2 , EGFR, and CysLT1. GBS exploitation of such network in penetration of the blood-brain barrier was demonstrated by targeting S1P2 , EGFR, and CysLT1 using pharmacological inhibition, gene knockout and knockdown cells, and gene knockout animals, as well as interrogation of the network (up- and downstream of each other). More importantly, counteracting such targets as a therapeutic adjunct to antibiotic therapy was beneficial in improving the outcome of animals with GBS meningitis. These findings indicate that investigating GBS penetration of the blood-brain barrier provides a novel approach for therapeutic development of GBS meningitis.

Proteomic analysis of bEnd.3 cells infected with wild-type and stk-deficient strains of Streptococcus suis serotype 2 reveals protein and pathway regulation

Streptococcus suis serotype 2 (SS2) is a zoonotic pathogen causing meningitis in humans and pigs. However, information on the comparative protein expression of the blood-brain barrier (BBB) following SS2 infection is limited. Deletion of the serine/threonine kinase (stk) gene can decrease the ability of SS2 to invade the BBB. In the present study, bEnd.3 cells were used as the BBB model, and a SILAC comparative quantitative proteomic study of bEnd.3 cells infected with the SS2 ZY05719 or Δstk strain was performed to determine the differences between these strains infections. Compared with ZY05719-infected cells, 241 proteins were highly upregulated, and 81 were significantly downregulated in Δstk-infected cells. The obtained data revealed major changes in the proteins involved in RNA process, host cytoskeleton, tight junction disruption and immune response. Some differentially expressed proteins were screened by quantitative real-time PCR to examine their regulation at the transcriptional level, and western blot analysis was used to validate the changes of some selected proteins at the translational level. The results obtained in this study may be useful to understand the host response to SS2 infection and provide crucial clues to decipher how STK expression in SS2 helps the bacteria penetrate the BBB. SIGNIFICANCE: A SILAC comparative quantitative proteomic assay was performed in bEnd.3 cells infected with the SS2 ZY05719 or Δstk strain. 241 upregulated and 81 downregulated differentially expressed proteins (DEPs) were identified. DEPs are involved in RNA process, host cytoskeleton, tight junction disruption and immune response. Some DEPs were examined by qPCR and western blot assays, which were similar to those of their corresponding proteins in the quantitative proteomics analysis.

Brucella abortus-Stimulated Platelets Activate Brain Microvascular Endothelial Cells Increasing Cell Transmigration through the Erk1/2 Pathway

Central nervous system invasion by bacteria of the genus Brucella results in an inflammatory disorder called neurobrucellosis. A common feature associated with this pathology is blood-brain barrier (BBB) activation. However, the underlying mechanisms involved with such BBB activation remain unknown. The aim of this work was to investigate the role of Brucella abortus-stimulated platelets on human brain microvascular endothelial cell (HBMEC) activation. Platelets enhanced HBMEC activation in response to B. abortus infection. Furthermore, supernatants from B. abortus-stimulated platelets also activated brain endothelial cells, inducing increased secretion of IL-6, IL-8, CCL-2 as well as ICAM-1 and CD40 upregulation on HBMEC compared with supernatants from unstimulated platelets. Outer membrane protein 19, a B. abortus lipoprotein, recapitulated B. abortus-mediated activation of HBMECs by platelets. In addition, supernatants from B. abortus-activated platelets promoted transendothelial migration of neutrophils and monocytes. Finally, using a pharmacological inhibitor, we demonstrated that the Erk1/2 pathway is involved in the endothelial activation induced by B. abortus-stimulated platelets and also in transendothelial migration of neutrophils. These results describe a mechanism whereby B. abortus-stimulated platelets induce endothelial cell activation, promoting neutrophils and monocytes to traverse the BBB probably contributing to the inflammatory pathology of neurobrucellosis.

Multidimensional Proteome Profiling of Blood-Brain Barrier Perturbation by Group B Streptococcus

Group B Streptococcus (GBS) remains the leading cause of neonatal meningitis, a disease associated with high rates of adverse neurological sequelae. The in vivo relationship between GBS and brain tissues remains poorly characterized, partly because past studies had focused on microbial rather than host processes. Additionally, the field has not capitalized on systems-level technologies to probe the host-pathogen relationship. Here, we use multiplexed quantitative proteomics to investigate the effect of GBS infection in the murine brain at various levels of tissue complexity, beginning with the whole organ and moving to brain vascular substructures. Infected whole brains showed classical signatures associated with the acute-phase response. In isolated brain microvessels, classical blood-brain barrier proteins were unaltered, but interferon signaling and leukocyte recruitment proteins were upregulated. The choroid plexus showed increases in peripheral immune cell proteins. Proteins that increased in abundance in the vasculature during GBS invasion were associated with major histocompatibility complex (MHC) class I antigen processing and endoplasmic reticulum dysfunction, a finding which correlated with altered host protein glycosylation profiles. Globally, there was low concordance between the infection proteome of whole brains and isolated vascular tissues. This report underscores the utility of unbiased, systems-scale analyses of functional tissue substructures for understanding disease.IMPORTANCE Group B Streptococcus (GBS) meningitis remains a major cause of poor health outcomes very early in life. Both the host-pathogen relationship leading to disease and the massive host response to infection contributing to these poor outcomes are orchestrated at the tissue and cell type levels. GBS meningitis is thought to result when bacteria present in the blood circumvent the selectively permeable vascular barriers that feed the brain. Additionally, tissue damage subsequent to bacterial invasion is mediated by inflammation and by immune cells from the periphery crossing the blood-brain barrier. Indeed, the vasculature plays a central role in disease processes occurring during GBS infection of the brain. Here, we employed quantitative proteomic analysis of brain vascular substructures during invasive GBS disease. We used the generated data to map molecular alterations associated with tissue perturbation, finding widespread intracellular dysfunction and punctuating the importance of investigations relegated to tissue type over the whole organ.

Polymorphonuclear Leukocyte Transendothelial Migration Proceeds at Blood-Brain Barrier in Neonatal Meningitis

Neonatal bacterial meningitis remains a life-threatening and causative sequelae disease in newborns, despite the effective usage of antibiotics and improved critical medical care. Polymorphonuclear leukocyte (PMN) transendothelial migration across the blood-brain barrier, one of the three hallmarks of bacterial meningitis, now is considered as a “double-edge sword”. When participating in host immune system defending against virulent pathogens, it results in tissue inflammation and following severe damage of central nervous system at the same time, which contributes to a disastrous consequence. Recently, several researches have focused on this multi-step process and the mechanism of how the virulent factors of different pathogens influence PMN migration. The great progression they made has enlightened a new research hotspot and a novel therapeutic strategy. This mini review outlines the determinants and progression of PMN transmigration in neonatal meningitis caused by different predominant pathogens.

Investigating Bacterial Penetration of the Blood-Brain Barrier for the Pathogenesis, Prevention, and Therapy of Bacterial Meningitis

The most distressing aspect of bacterial meningitis is limited improvement in the mortality and morbidity despite attributable advances in antimicrobial chemotherapy and supportive care. A major contributing factor to such mortality and morbidity is our incomplete understanding of the pathogenesis of this disease. Microbial penetration of the blood-brain barrier, a prerequisite for the development of bacterial meningitis, exploits specific host and bacterial factors as well as host cell signaling molecules. Determination and characterization of such host and bacterial factors have been instrumental for developing our current knowledge on the pathogenesis of bacterial meningitis. In addition, counteracting such host and microbial factors has been shown to be efficacious in the prevention of bacterial meningitis. Antimicrobial therapy alone has limited efficacy in improving the outcome of bacterial meningitis. Recent studies suggest that counteracting targets contributing to bacterial penetration of the blood-brain barrier are a beneficial therapeutic adjunct to antimicrobial therapy in improving the outcome of bacterial meningitis. Taken together, these findings indicate that the elucidation of host and bacterial factors contributing to microbial penetration of the blood-brain barrier provides a novel strategy for investigating the pathogenesis, prevention, and therapy of bacterial meningitis.

Virulence Factors of Meningitis-Causing Bacteria: Enabling Brain Entry across the Blood-Brain Barrier

Infections of the central nervous system (CNS) are still a major cause of morbidity and mortality worldwide. Traversal of the barriers protecting the brain by pathogens is a prerequisite for the development of meningitis. Bacteria have developed a variety of different strategies to cross these barriers and reach the CNS. To this end, they use a variety of different virulence factors that enable them to attach to and traverse these barriers. These virulence factors mediate adhesion to and invasion into host cells, intracellular survival, induction of host cell signaling and inflammatory response, and affect barrier function. While some of these mechanisms differ, others are shared by multiple pathogens. Further understanding of these processes, with special emphasis on the difference between the blood-brain barrier and the blood-cerebrospinal fluid barrier, as well as virulence factors used by the pathogens, is still needed.

Diminished Capsule Exacerbates Virulence, Blood-Brain Barrier Penetration, Intracellular Persistence, and Antibiotic Evasion of Hyperhemolytic Group B Streptococci

Group B streptococci (GBS) are encapsulated, β-hemolytic bacteria that are a common cause of infections in human newborns and certain adults. Two factors important for GBS virulence are the sialic acid capsular polysaccharide that promotes immune evasion and the hemolytic pigment that induces host cell cytotoxcity. These virulence factors are often oppositely regulated by the CovR/CovS two-component system. Clinical GBS strains exhibiting hyperhemolysis and low capsule due to pathoadaptive covR/S mutations have been isolated from patients. Given the importance of capsule to GBS virulence, we predicted that a decrease or loss of capsule would attenuate the virulence of covR/S mutants. Surprisingly, hyperhemolytic GBS with low or no capsule exhibit increased virulence, intracellular persistence, and blood-brain barrier penetration, which was independent of a Trojan horse mechanism of barrier penetration. Additionally, intracellular persistence enabled both hemolytic and hyperhemolytic GBS to evade antibiotics routinely used to treat these infections. The finding that diminished capsule expression promotes GBS virulence, intracellular persistence, and antibiotic evasion has important implications for sustained antibiotic therapy and efficacy of capsule-based vaccines.

Past and Current Perspectives in Modeling Bacteria and Blood-Brain Barrier Interactions

The central nervous system (CNS) barriers are highly specialized cellular barriers that promote brain homeostasis while restricting pathogen and toxin entry. The primary cellular constituent regulating pathogen entry in most of these brain barriers is the brain endothelial cell (BEC) that exhibits properties that allow for tight regulation of CNS entry. Bacterial meningoencephalitis is a serious infection of the CNS and occurs when bacteria can cross specialized brain barriers and cause inflammation. Models have been developed to understand the bacterial - BEC interaction that lead to pathogen crossing into the CNS, however, these have been met with challenges due to these highly specialized BEC phenotypes. This perspective provides a brief overview and outlook of the in vivo and in vitro models currently being used to study bacterial brain penetration, and opinion on improved models for the future.

The Group B Streptococcal surface antigen I/II protein, BspC, interacts with host vimentin to promote adherence to brain endothelium and inflammation during the pathogenesis of meningitis

Streptococcus agalactiae (Group B Streptococcus, GBS) normally colonizes healthy adults but can cause invasive disease, such as meningitis, in the newborn. To gain access to the central nervous system, GBS must interact with and penetrate brain or meningeal blood vessels; however, the exact mechanisms are still being elucidated. Here, we investigate the contribution of BspC, an antigen I/II family adhesin, to the pathogenesis of GBS meningitis. Disruption of the bspC gene reduced GBS adherence to human cerebral microvascular endothelial cells (hCMEC), while heterologous expression of BspC in non-adherent Lactococcus lactis conferred bacterial attachment. In a murine model of hematogenous meningitis, mice infected with ΔbspC mutants exhibited lower mortality as well as decreased brain bacterial counts and inflammatory infiltrate compared to mice infected with WT GBS strains. Further, BspC was both necessary and sufficient to induce neutrophil chemokine expression. We determined that BspC interacts with the host cytoskeleton component vimentin and confirmed this interaction using a bacterial two-hybrid assay, microscale thermophoresis, immunofluorescent staining, and imaging flow cytometry. Vimentin null mice were protected from WT GBS infection and also exhibited less inflammatory cytokine production in brain tissue. These results suggest that BspC and the vimentin interaction is critical for the pathogenesis of GBS meningitis.

Group B Streptococcus (GBS) typically colonizes healthy adults but can cause severe disease in immune-compromised individuals, including newborns. Despite wide-spread intrapartum antibiotic prophylaxis given to pregnant women, GBS remains a leading cause of neonatal meningitis. To cause meningitis, GBS must interact with and penetrate the blood-brain barrier (BBB), which separates bacteria and immune cells in the blood from the brain. In order to develop targeted therapies to treat GBS meningitis, it is important to understand the mechanisms of BBB crossing. Here, we describe the role of the GBS surface factor, BspC, in promoting meningitis and discover the host ligand for BspC, vimentin, which is an intermediate filament protein that is constitutively expressed by endothelial cells. We determined that BspC interacts with the C-terminal domain of cell-surface vimentin to promote bacterial attachment to brain endothelial cells and that purified BspC protein can induce immune signaling pathways. In a mouse model of hematogenous meningitis, we observed that a GBS mutant lacking BspC was less virulent compared to WT GBS and resulted in less inflammatory disease. We also observed that mice lacking vimentin were protected from GBS infection. These results reveal the importance of the BspC-vimentin interaction in the progression of GBS meningitis disease.

Fatty acids and selected endocannabinoids content in cerebrospinal fluids from patients with neuroinfections

Neuroinfections are a significant medical problem and can have serious health consequences for patients. Their outcome, if not fatal, can be associated with permanent residual deficits. Cerebrospinal fluid (CSF) examination is commonly used for meningitis confirmation. Fatty acids (FA) are precursors of lipid mediators with pharmacological activity. They actively modulate inflammation as well as contribute to its resolution. Therefore the aim of this study was to determine the FA and selected endocannabinoids (ECB) content in the CSF obtained from patients with bacterial (BM) and viral meningitis (VM) using chromatographic techniques. A significantly lower level of saturated FA was found in patients with BM and VM as compared to controls. There was a significantly higher concentration of long-chain monounsaturated FA and polyunsaturated n-6 FA in the CSF obtained from patients with neuroinfection. Moreover, a significant reduction of n-3 FA in CSF obtained from patients with BM and VM was demonstrated. The highest amount of ECB was detected in the CSF of patients with VM: eicosapentaenoyl ethanolamide (1.65 pg/mL), docosahexaenoyl ethanolamide (655.5 pg/mL) and nervonoyl ethanolamide (3.09 ng/mL). Results indicate the participation of long-chain monounsaturated and polyunsaturated FA and their derivatives in the inflammatory process and likely in the process of resolution of inflammation during neuroinfection. It seems that the determination of the FA and ECB profile in CSF may be a valuable biomarker of health and may allow the development of new pharmacological strategies, therapeutic goals and fatty acids supplementation necessary in the fight against inflammation of the central nervous system.

The Double Life of Group B Streptococcus: Asymptomatic Colonizer and Potent Pathogen

Group B streptococcus (GBS) is a β-hemolytic gram-positive bacterium that colonizes the lower genital tract of approximately 18% of women globally as an asymptomatic member of the gastrointestinal and/or vaginal flora. If established in other host niches, however, GBS is highly pathogenic. During pregnancy, ascending GBS infection from the vagina to the intrauterine space is associated with preterm birth, stillbirth, and fetal injury. In addition, vertical transmission of GBS during or after birth results in life-threatening neonatal infections, including pneumonia, sepsis, and meningitis. Although the mechanisms by which GBS traffics from the lower genital tract to vulnerable host niches are not well understood, recent advances have revealed that many of the same bacterial factors that promote asymptomatic vaginal carriage also facilitate dissemination and virulence. Furthermore, highly pathogenic GBS strains have acquired unique factors that enhance survival in invasive niches. Several host factors also exist that either subdue GBS upon vaginal colonization or alternatively permit invasive infection. This review summarizes the GBS and host factors involved in GBS's state as both an asymptomatic colonizer and an invasive pathogen. Gaining a better understanding of these mechanisms is key to overcoming the challenges associated with vaccine development and identification of novel strategies to mitigate GBS virulence.

Neurovascular dysfunction in vascular dementia, Alzheimer's and atherosclerosis

Efficient blood supply to the brain is of paramount importance to its normal functioning and improper blood flow can result in potentially devastating neurological consequences. Cerebral blood flow in response to neural activity is intrinsically regulated by a complex interplay between various cell types within the brain in a relationship termed neurovascular coupling. The breakdown of neurovascular coupling is evident across a wide variety of both neurological and psychiatric disorders including Alzheimer’s disease. Atherosclerosis is a chronic syndrome affecting the integrity and function of major blood vessels including those that supply the brain, and it is therefore hypothesised that atherosclerosis impairs cerebral blood flow and neurovascular coupling leading to cerebrovascular dysfunction. This review will discuss the mechanisms of neurovascular coupling in health and disease and how atherosclerosis can potentially cause cerebrovascular dysfunction that may lead to cognitive decline as well as stroke. Understanding the mechanisms of neurovascular coupling in health and disease may enable us to develop potential therapies to prevent the breakdown of neurovascular coupling in the treatment of vascular brain diseases including vascular dementia, Alzheimer’s disease and stroke.

CSF leukocyte, polykaryocyte, protein and glucose: Their cut-offs of judging whether post-neurosurgical bacterial meningitis has been cured

OBJECT

This paper is aimed to explore a reasonable guideline for distinguishing whether post-neurosurgical bacterial meningitis has completely been cured, so as to avoid the deficient or excessive treatment for post-neurosurgical bacterial meningitis.

PATIENTS AND METHODS

We conducted a retrospective analysis of 46 patients who attended General Hospital of Chinese People's Armed Police Force in Beijing, China, from January 1, 2014 to April 30, 2016. The CSF leukocyte, polykaryocyte, protein and glucose had been tested when their antibiotic treatments were empirically stopped. Between the non-relapse and relapse groups, Wilcoxon Rank Sum test was used to compare the differences of CSF leukocyte and polykaryocyte, and t-test was applied to contrast the distinctions of CSF protein and glucose, then, the thresholds of significant items were estimated by ROC curve.

RESULTS

The CSF leukocyte counts in non-relapse group are 23.72 ± 14.12/mm³, which are statistically less than the relapse group's (47.00 ± 1.00/mm³, P = 0.014), so does the CSF polykaryocyte counts (1.74 ± 4.84/mm³ &4.67 ± 1.15/mm³, P = 0.012). Between the two groups, the AUCs of leucocyte and polykaryocyte are 0.926 (95% CI = 0.845-1.0, P = 0.014) and 0.884 (95%CI = 0.786-0.982, P = 0.028), respectively. Their critical values are 44/mm³ (sensitivity = 1, specificity = 0.907) and 3/mm³ (sensitivity = 1, specificity = 0.837). Conversely, CSF protein and glucose have no statistic differences between the two groups.

CONCLUSION

Both CSF leukocyte and polykaryocyte can satisfactorily indicate whether the post-neurosurgical bacterial meningitis has completely been cured, 0-44/mm³ is recommended as the reference range of CSF leukocyte, and the CSF polykaryocyte' s is 0-3/mm³.

The plasminogen binding protein PbsP is required for brain invasion by hypervirulent CC17 Group B streptococci

Streptococcus agalactiae (Group B Streptococcus or GBS) is a frequent cause of serious disease in newborns and adults. Epidemiological evidence indicates a strong association between GBS strains belonging to the hypervirulent CC17 clonal complex and the occurrence of meningitis in neonates. We investigate here the role of PbsP, a cell wall plasminogen binding protein, in colonization of the central nervous system by CC17 GBS. Deletion of pbsP selectively impaired the ability of the CC17 strain BM110 to colonize the mouse brain after intravenous challenge, despite its unchanged capacity to persist at high levels in the blood and to invade the kidneys. Moreover, immunization with a recombinant form of PbsP considerably reduced brain infection and lethality. In vitro, pbsP deletion markedly decreased plasmin-dependent transmigration of BM110 through brain microvascular endothelial cells. Although PbsP was modestly expressed in bacteria grown under standard laboratory conditions, pbsP expression was markedly upregulated during in vivo infection or upon contact with cultured brain endothelial cells. Collectively, our studies indicate that PbsP is a highly conserved Plg binding adhesin, which is functionally important for invasion of the central nervous system by the hypervirulent CC17 GBS. Moreover, this antigen is a promising candidate for inclusion in a universal GBS vaccine.

Stable Expression of Modified Green Fluorescent Protein in Group B Streptococci To Enable Visualization in Experimental Systems

Group B streptococcus (GBS) is a Gram-positive bacterium associated with various diseases in humans and animals. Many studies have examined GBS physiology, virulence, and microbe-host interactions using diverse imaging approaches, including fluorescence microscopy. Strategies to label and visualize GBS using fluorescence biomarkers have been limited to antibody-based methods or nonspecific stains that bind DNA or protein; an effective plasmid-based system to label GBS with a fluorescence biomarker would represent a useful visualization tool. In this study, we developed and validated a green fluorescent protein (GFP)-variant-expressing plasmid, pGU2664, which can be applied as a marker to visualize GBS in experimental studies. The synthetic constitutively active CP25 promoter drives strong and stable expression of the GFPmut3 biomarker in GBS strains carrying pGU2664. GBS maintains GFPmut3 activity at different phases of growth. The application of fluorescence polarization enables easy discrimination of GBS GFPmut3 activity from the autofluorescence of culture media commonly used to grow GBS. Differential interference contrast microscopy, in combination with epifluorescence microscopy to detect GFPmut3 in GBS, enabled visualization of bacterial attachment to live human epithelial cells in real time. Plasmid pGU2664 was also used to visualize phenotypic differences in the adherence of wild-type GBS and an isogenic gene-deficient mutant strain lacking CovR (the control of virulence regulator) in adhesion assays. The system for GFPmut3 expression in GBS described in this study provides a new tool for the visualization of this organism in diverse research applications. We discuss the advantages and consider the limitations of this fluorescent biomarker system developed for GBS.IMPORTANCE Group B streptococcus (GBS) is a bacterium associated with various diseases in humans and animals. This study describes the development of a strategy to label and visualize GBS using a fluorescence biomarker, termed GFPmut3. We show that this biomarker can be successfully applied to track the growth of bacteria in liquid medium, and it enables the detailed visualization of GBS in the context of live human cells in real-time microscopic analysis. The system for GFPmut3 expression in GBS described in this study provides a new tool for the visualization of this organism in diverse research applications.

Mechanisms of Blood Brain Barrier Disruption by Different Types of Bacteria, and Bacterial-Host Interactions Facilitate the Bacterial Pathogen Invading the Brain

This review aims to elucidate the different mechanisms of blood brain barrier (BBB) disruption that may occur due to invasion by different types of bacteria, as well as to show the bacteria-host interactions that assist the bacterial pathogen in invading the brain. For example, platelet-activating factor receptor (PAFR) is responsible for brain invasion during the adhesion of pneumococci to brain endothelial cells, which might lead to brain invasion. Additionally, the major adhesin of the pneumococcal pilus-1, RrgA is able to bind the BBB endothelial receptors: polymeric immunoglobulin receptor (pIgR) and platelet endothelial cell adhesion molecule (PECAM-1), thus leading to invasion of the brain. Moreover, Streptococcus pneumoniae choline binding protein A (CbpA) targets the common carboxy-terminal domain of the laminin receptor (LR) establishing initial contact with brain endothelium that might result in BBB invasion. Furthermore, BBB disruption may occur by S. pneumoniae penetration through increasing in pro-inflammatory markers and endothelial permeability. In contrast, adhesion, invasion, and translocation through or between endothelial cells can be done by S. pneumoniae without any disruption to the vascular endothelium, upon BBB penetration. Internalins (InlA and InlB) of Listeria monocytogenes interact with its cellular receptors E-cadherin and mesenchymal-epithelial transition (MET) to facilitate invading the brain. L. monocytogenes species activate NF-κB in endothelial cells, encouraging the expression of P- and E-selectin, intercellular adhesion molecule 1 (ICAM-1), and Vascular cell adhesion protein 1 (VCAM-1), as well as IL-6 and IL-8 and monocyte chemoattractant protein-1 (MCP-1), all these markers assist in BBB disruption. Bacillus anthracis species interrupt both adherens junctions (AJs) and tight junctions (TJs), leading to BBB disruption. Brain microvascular endothelial cells (BMECs) permeability and BBB disruption are induced via interendothelial junction proteins reduction as well as up-regulation of IL-1α, IL-1β, IL-6, TNF-α, MCP-1, macrophage inflammatory proteins-1 alpha (MIP1α) markers in Staphylococcus aureus species. Streptococcus agalactiae or Group B Streptococcus toxins (GBS) enhance IL-8 and ICAM-1 as well as nitric oxide (NO) production from endothelial cells via the expression of inducible nitric oxide synthase (iNOS) enhancement, resulting in BBB disruption. While Gram-negative bacteria, Haemophilus influenza OmpP2 is able to target the common carboxy-terminal domain of LR to start initial interaction with brain endothelium, then invade the brain. H. influenza type b (HiB), can induce BBB permeability through TJ disruption. LR and PAFR binding sites have been recognized as common routes of CNS entrance by Neisseria meningitidis. N. meningitidis species also initiate binding to BMECs and induces AJs deformation, as well as inducing specific cleavage of the TJ component occludin through the release of host MMP-8. Escherichia coli bind to BMECs through LR, resulting in IL-6 and IL-8 release and iNOS production, as well as resulting in disassembly of TJs between endothelial cells, facilitating BBB disruption. Therefore, obtaining knowledge of BBB disruption by different types of bacterial species will provide a picture of how the bacteria enter the central nervous system (CNS) which might support the discovery of therapeutic strategies for each bacteria to control and manage infection.

Gold nanoparticles: A plausible tool to combat neurological bacterial infections in humans

Management of bacterial infections of central nervous system is a major challenge for the scientists all over the world. Despite the development of various potential drugs, the issue of central nervous system infections persists in the society. The main constraint is the delivery of drugs across the blood brain barrier and only a few drugs after meeting the stringent criteria could cross the blood brain barrier. On the other hand, certain bacterial pathogens could easily enter the brain by using several factors and mechanisms by crossing the blood brain barriers. Interestingly, in the recent past, gold nanoparticles have shown immense potential to overcome the issues associated with the treatment of central nervous system infections, especially due to their inherent ability to cross the blood brain barrier. Initially, the present review summarized the recent updates on the pathogenesis and factors involved in neurological bacterial infections, including the mechanism used by bacterial pathogens to cross the blood brain barriers. Thereafter, the emphasis of the review was on providing current information on gold nanoparticles pertinent to their applicability for the treatment of neurological infections. After discussing the background of neurological bacterial infections, the characteristic features, antibacterial properties, mechanisms of antibacterial action and ability to cross the blood brain barrier of gold nanoparticles have been summarized. Some of the features of gold nanoparticles that make them an ideal candidate for brain delivery are biocompatibity, stability, ability to get synthesized in different sizes with facile methods, surface affinity towards various functional groups, spontaneous crossing of blood brain barrier without applying any external field and most importantly, easy non-invasive tracing by CT imaging. The current updates on the development of gold nanoparticles based therapeutic strategies for the prevention and treatment of central nervous system infections have been discussed in the present study. However, further investigation would be required to translate these preclinical outcomes into clinical applications. Nevertheless, we could safely state that the information gathered and discussed in the present review would benefit the scientists working in the field of neuro-nanotechnology.

Brucella abortus Traverses Brain Microvascular Endothelial Cells Using Infected Monocytes as a Trojan Horse

Neurobrucellosis is an inflammatory disease caused by the invasion of Brucella spp. to the central nervous system (CNS). The pathogenesis of the disease is not well characterized; however, for Brucella to gain access to the brain parenchyma, traversing of the blood-brain barrier (BBB) must take place. To understand the CNS determinants of the pathogenesis of B. abortus, we have used the in vitro BBB model of human brain microvascular endothelial cells (HBMEC) to study the interactions between B. abortus and brain endothelial cells. In this study, we showed that B. abortus is able to adhere and invade HBMEC which was dependent on microtubules, microfilaments, endosome acidification and de novo protein synthesis. After infection, B. abortus rapidly escapes the endosomal compartment of HBMEC and forms a replicative Brucella-containing vacuole that involves interactions with the endoplasmic reticulum. Despite the ability of B. abortus to invade and replicate in HBMEC, the bacterium was unable by itself to traverse HBMEC, but could traverse polarized HBMEC monolayers within infected monocytes. Importantly, infected monocytes that traversed the HBMEC monolayer were a bacterial source for de novo infection of glial cells. This is the first demonstration of the mechanism whereby B. abortus is able to traverse the BBB and infect cells of the CNS. These results may have important implications in our understanding of the pathogenesis of neurobrucellosis.

Crossing the Blood-Brain Barrier by Neuroinvasive Pathogens

The penetration of the blood-brain barrier (BBB) and invasion of the central nervous system (CNS) are important steps for all neuroinvasive pathogens. All of the ways of pathogens passing through the BBB are still unclear. Among known pathways, pathogen traversal can occur paracellularly, transcellularly or using a “Trojan horse” mechanism. The first step of translocation across the BBB is the interactions of the pathogen’s ligands with the receptors of the host brain cells. Lyme disease, the most common vector-borne disease in the temperate zones of Europe and North America, are caused by Borreliella species (former Borrelia burgdorferi sensu lato) that affects the peripheral and the CNS. In this review, we have presented various pathogen interactions with endothelial cells, which allow the disruption of the BBB so that the pathogens can pass across the BBB.

A cytosol derived factor of Group B streptococcus prevent its invasion into human epithelial cells

Group B streptococcus (GBS) or Streptococcus agalactiae, is an opportunistic pathogen causing a wide range of infections like pneumonia, sepsis, and meningitis in newborn, pregnant women and adults. While this bacterium has adapted well to asymptomatic colonization of adult humans, it still remains a potentially devastating pathogen to susceptible infants. Advances in molecular techniques and refinement of in vitro and in vivo model systems have elucidated key elements of the pathogenic process, from initial attachment to the maternal vaginal epithelium to penetration of the newborn blood-brain barrier. Still, the formidable array of GBS virulence factors makes this bacterium at the forefront of neonatal pathogens. The involvement of bacterial components in the host-pathogen interaction of GBS pathogenesis and its related diseases is not clearly understood. In this study we demonstrated the role of a 39 kDa factor from GBS which plays an important role in the process of its invasion. We found a homogeneous 39 kDa factor from the cytosol of GBS after following a combination of sequential purification steps involving molecular sieving and ion exchange chromatography using ACTA-FPLC system. Its N-terminal sequence showed a homology with xenobiotic response element type transcriptional regulator protein, a 40 kDa protein of Streptococcus. This factor leads to inhibition of GBS invasion in HeLa and A549 cells. This protein also showed sensitivity and specific cross reactivity with the antibodies raised against it in New Zealand white rabbits by western immunoblotting. This inhibitory factor was further confirmed tolerant for its cytotoxicity. These results add a novel aspect to bacterial pathogenesis where bacteria's own intracellular protein component can act as a potential therapeutic candidate by decreasing the severity of disease thus promoting its invasion inhibition.

Streptococcus agalactiae meningoencephalitis associated with gastroesophageal reflux disease and chronic proton pump inhibitors use, in a 9 month-old infant: a case report

Background

Streptococcus agalactiae (Group B Streptococcus) is recognized as the etiologic agent of newborn and infant meningitis, aged up to 90 days, starting from the colonization of the maternal genital or gastrointestinal tract, but it is rarely responsible for meningitis in old infants.

Case presentation

We present the case of a 9 month-old infant diagnosed with S. agalactiae meningoencephalitis associated with chronic gastroesophageal reflux disease treated with a proton pump inhibitor (PPI).

Conclusion

The use of a PPI is a risk factor for ultra-late onset of Group B Streptococcus meningitis. The use of PPI in infants should be closely monitored in the light of changes in the gut microbiota, in the oropharyngeal and of the respiratory tract colonization, potentially with pathogenic flora.

Electronic supplementary material

The online version of this article (10.1186/s12887-018-0995-0) contains supplementary material, which is available to authorized users.

The Streptococcus agalactiae Stringent Response Enhances Virulence and Persistence in Human Blood

Streptococcus agalactiae (group B Streptococcus [GBS]) causes serious infections in neonates. We previously reported a transposon sequencing (Tn-seq) system for performing genomewide assessment of gene fitness in GBS. In order to identify molecular mechanisms required for GBS to transition from a mucosal commensal lifestyle to bloodstream invasion, we performed Tn-seq on GBS strain A909 with human whole blood. Our analysis identified 16 genes conditionally essential for GBS survival in blood, of which 75% were members of the capsular polysaccharide (cps) operon. Among the non-cps genes identified as conditionally essential was relA, which encodes an enzyme whose activity is central to the bacterial stringent response—a conserved adaptation to environmental stress. We used blood coincubation studies of targeted knockout strains to confirm the expected growth defects of GBS deficient in capsule or stringent response activation. Unexpectedly, we found that the relA knockout strains demonstrated decreased expression of β-hemolysin/cytolysin, an important cytotoxin implicated in facilitating GBS invasion. Furthermore, chemical activation of the stringent response with serine hydroxamate increased β-hemolysin/cytolysin expression. To establish a mechanism by which the stringent response leads to increased cytotoxicity, we performed transcriptome sequencing (RNA-seq) on two GBS strains grown under stringent response or control conditions. This revealed a conserved decrease in the expression of genes in the arginine deiminase pathway during stringent response activation. Through coincubation with supplemental arginine and the arginine antagonist canavanine, we show that arginine availability is a determinant of GBS cytotoxicity and that the pathway between stringent response activation and increased virulence is arginine dependent.

Modeling Group B Streptococcus and Blood-Brain Barrier Interaction by Using Induced Pluripotent Stem Cell-Derived Brain Endothelial Cells

Bacterial meningitis is a serious infection of the central nervous system (CNS) that occurs after bacteria interact with and penetrate the blood-brain barrier (BBB). The BBB is comprised of highly specialized brain microvascular endothelial cells (BMECs) that function to separate the circulation from the CNS and act as a formidable barrier for toxins and pathogens. Certain bacteria, such as Streptococcus agalactiae (group B Streptococcus [GBS]), possess the ability to interact with and penetrate the BBB to cause meningitis. Modeling bacterial interaction with the BBB in vitro has been limited to primary and immortalized BMEC culture. While useful, these cells often do not retain BBB-like properties, and human primary cells have limited availability. Recently, a human induced pluripotent stem cell (iPSC)-derived BMEC model has been established that is readily renewable and retains key BBB phenotypes. Here, we sought to evaluate whether the iPSC-derived BMECs were appropriate for modeling bacterial interaction with the BBB. Using GBS as a model meningeal pathogen, we demonstrate that wild-type GBS adhered to, invaded, and activated the iPSC-derived BMECs, while GBS mutants known to have diminished BBB interaction were attenuated in the iPSC-derived model. Furthermore, bacterial infection resulted in the disruption of tight junction components ZO-1, occludin, and claudin-5. Thus, we show for the first time that the iPSC-derived BBB model can be utilized to study BBB interaction with a bacterial CNS pathogen. IMPORTANCE Here for the first time, human iPSC-derived BMECs were used to model bacterial interaction with the BBB. Unlike models previously used to study these interactions, iPSC-derived BMECs possess robust BBB properties, such as the expression of complex tight junctions that are key components for the investigation of bacterial effects on the BBB. Here, we demonstrated that GBS interacts with the iPSC-derived BMECs and specifically disrupts these tight junctions. Thus, using this BBB model may allow researchers to uncover novel mechanisms of BBB disruption during meningitis that are inaccessible to immortalized or primary cell models that lack substantial tight junctions.

The first report of CD2 associated protein gene, in a teleost (Rock bream, Oplegnathus fasciatus): An investigation of the immune response upon infection with several pathogens

CD2 is expressed on the surfaces of virtually all T cells and natural killer (NK) cells. In mammals, the CD2 molecule is 50 kDa. The cytoplasmic tail of CD2 interacts with CD2-associated protein (CD2AP), which plays an important role in mediating the trigger signal in outer magnetic pole cells. In this study, we identified CD2AP from rock bream and investigated its gene expression. The ORF of CD2AP (1950 bp) encodes 650 amino acids (aa). CD2AP has a Src homology 3 (SH3) domain. Quantitative real-time PCR analysis revealed that CD2AP shows higher expression in the gills and skin. Under experimental challenge, CD2AP gene expression was increased as relative to the control after 7 days. This result will improve our understanding of blood vessels in teleost fish, and will provide a basis for the study of CD2-related genes.

Guidance on the risk assessment of substances present in food intended for infants below 16 weeks of age

Following a request from the European Commission to EFSA, the EFSA Scientific Committee (SC) prepared a guidance for the risk assessment of substances present in food intended for infants below 16 weeks of age. In its approach to develop this guidance, the EFSA SC took into account, among others, (i) an exposure assessment based on infant formula as the only source of nutrition; (ii) knowledge of organ development in human infants, including the development of the gut, metabolic and excretory capacities, the brain and brain barriers, the immune system, the endocrine and reproductive systems; (iii) the overall toxicological profile of the substance identified through the standard toxicological tests, including critical effects; (iv) the relevance for the human infant of the neonatal experimental animal models used. The EFSA SC notes that during the period from birth up to 16 weeks, infants are expected to be exclusively fed on breast milk and/or infant formula. The EFSA SC views this period as the time where health-based guidance values for the general population do not apply without further considerations. High infant formula consumption per body weight is derived from 95th percentile consumption. The first weeks of life is the time of the highest relative consumption on a body weight basis. Therefore, when performing an exposure assessment, the EFSA SC proposes to use the high consumption value of 260 mL/kg bw per day. A decision tree approach is proposed that enables a risk assessment of substances present in food intended for infants below 16 weeks of age. The additional information needed when testing substances present in food for infants below 16 weeks of age and the approach to be taken for the risk assessment are on a case-by-case basis, depending on whether the substance is added intentionally to food and is systemically available.