SILAC and LC-MS/MS identification of Streptococcus equi ssp. zooepidemicus proteins that contribute to mouse brain microvascular endothelial cell infection

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.

Blood-Brain Barrier Integrity Damage in Bacterial Meningitis: The Underlying Link, Mechanisms, and Therapeutic Targets

Despite advances in supportive care and antimicrobial treatment, bacterial meningitis remains the most serious infection of the central nervous system (CNS) that poses a serious risk to life. This clinical dilemma is largely due to our insufficient knowledge of the pathology behind this disease. By controlling the entry of molecules into the CNS microenvironment, the blood-brain barrier (BBB), a highly selective cellular monolayer that is specific to the CNS's microvasculature, regulates communication between the CNS and the rest of the body. A defining feature of the pathogenesis of bacterial meningitis is the increase in BBB permeability. So far, several contributing factors for BBB disruption have been reported, including direct cellular damage brought on by bacterial virulence factors, as well as host-specific proteins or inflammatory pathways being activated. Recent studies have demonstrated that targeting pathological factors contributing to enhanced BBB permeability is an effective therapeutic complement to antimicrobial therapy for treating bacterial meningitis. Hence, understanding how these meningitis-causing pathogens affect the BBB permeability will provide novel perspectives for investigating bacterial meningitis's pathogenesis, prevention, and therapies. Here, we summarized the recent research progress on meningitis-causing pathogens disrupting the barrier function of BBB. This review provides handy information on BBB disruption by meningitis-causing pathogens, and helps design future research as well as develop potential combination therapies.

Streptococcus equi subspecies zooepidemicus Meningitis, Septicemia, and Brain Infarcts in a Costa Rican Infant

Streptococcus equi, an equine commensal bacterium, is a rare etiology of septicemia and meningoencephalitis in humans and is extremely infrequent in children. Scarce literature has been published about its clinical presentation, treatment and outcomes in infants. Here, we describe a case of S. equi subsp. zooepidemicus septicemia and meningoencephalitis in a five-month-old Costa Rican infant that was confirmed by peripheral blood and cerebrospinal fluid (CSF) cultures in a regional hospital of the Pacific coast of Costa Rica who developed multiple ischemic cerebral infarcts secondary to infectious vasculitis, a subdural empyema and serious neurological sequelae. We also reviewed the literature on S. equi meningitis in infants under one year of age. This is the first reported case in our country, the fourth reported in infants under one year of age and the second describing multiple cerebral infarcts and subdural empyema in an infant.

Meningitis due to Streptococcus equi in a 73 year old woman with an osteodural defect

Meningitis caused by Streptococcus equi (SE) is a rare disease associated with high rates of complications. Commonly identified risk factors are regular horse contact and consumption of unpasteurized dairy products. When diagnosed promptly, this infection can be cured.

We report the case of a 73 year old woman who presented to the hospital with a sudden holocranial headaches, fever, photophobia, sonophobia, vomiting and behavioural disorders.

She lived in a rural area and regularly consumed unpasteurized milk products. She had a medical history of osteodural defect, chronic otitis, high blood pressure and pulmonary fibrosis.

We suspected bacterial meningitis associated with an ear infection. A lumbar puncture was performed. Streptococcus equi zooepidemicus(SEZ) was discovered in the CSF’s culture. Initially, the patient was treated with ceftriaxone. She had a tonic-clonic seizure 2days later. On the cerebral enhanced MRI, we found a right temporal pored cavity adjacent to a tegmen tympani bone breach. The patient received 15 days of antibiotic therapy with a good outcome. However, she was readmitted 24 h after being discharged for the same initial symptomatology. She received a total of 25 days of antibiotics and 4 days of corticoids with good results.

Only a few cases of Streptococcus equi meningitis have been documented. We reported this case to insist on the importance of considering this diagnosis in patients with risk factors. We also point out that severe complications may occur despite the early initiation of adequate treatment.

A streptococcal Fic domain-containing protein disrupts blood-brain barrier integrity by activating moesin in endothelial cells

Streptococcus equi subsp. zooepidemicus (SEZ) is a zoonotic pathogen capable of causing meningitis in humans. The mechanisms that enable pathogens to traverse the blood-brain barrier (BBB) are incompletely understood. Here, we investigated the role of a newly identified Fic domain-containing protein, BifA, in SEZ virulence. BifA was required for SEZ to cross the BBB and to cause meningitis in mice. BifA also enhanced SEZ translocation across human Brain Microvascular Endothelial Cell (hBMEC) monolayers. Purified BifA or its Fic domain-containing C-terminus alone were able to enter into hBMECs, leading to disruption of monolayer barrier integrity. A SILAC-based proteomic screen revealed that BifA binds moesin. BifA’s Fic domain was required for its binding to this regulator of host cell cytoskeletal processes. BifA treatment of hBMECs led to moesin phosphorylation and downstream RhoA activation. Inhibition of moesin activation or moesin depletion in hBMEC monolayers abrogated BifA-mediated increases in barrier permeability and SEZ’s capacity to translocate across monolayers. Thus, BifA activation of moesin appears to constitute a key mechanism by which SEZ disrupts endothelial monolayer integrity to penetrate the BBB.

Streptococcus equi subsp. zooepidemicus (SEZ) is an important animal pathogen and can cause meningitis in humans. Little is known about how this Group C streptococcal species penetrates the blood-brain barrier (BBB). We identified bifA, a gene that is critical for SEZ to cause meningitis in mice and to penetrate a human brain endothelial monolayer in a tissue culture model. BifA’s Fic domain enables the protein to enter into endothelial monolayers and to bind to moesin, a cytoskeletal regulatory protein, leading to its activation. Preventing moesin activation abolished BifA-induced barrier leakiness and SEZ’s capacity to penetrate a monolayer barrier. Together, our findings suggest that SEZ meningitis depends on BifA, a Fic-domain protein that manipulates moesin-dependent signaling to modulate BBB permeability.

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.

Brachyspira hyodysenteriae and B. pilosicoli Proteins Recognized by Sera of Challenged Pigs

The spirochetes Brachyspira hyodysenteriae and B. pilosicoli are pig intestinal pathogens that are the causative agents of swine dysentery (SD) and porcine intestinal spirochaetosis (PIS), respectively. Although some inactivated bacterin and recombinant vaccines have been explored as prophylactic treatments against these species, no effective vaccine is yet available. Immunoproteomics approaches hold the potential for the identification of new, suitable candidates for subunit vaccines against SD and PIS. These strategies take into account the gene products actually expressed and present in the cells, and thus susceptible of being targets of immune recognition. In this context, we have analyzed the immunogenic pattern of two B. pilosicoli porcine isolates (the Spanish farm isolate OLA9 and the commercial P43/6/78 strain) and one B. hyodysenteriae isolate (the Spanish farm V1). The proteins from the Brachyspira lysates were fractionated by preparative isoelectric focusing, and the fractions were analyzed by Western blot with hyperimmune sera from challenged pigs. Of the 28 challenge-specific immunoreactive bands detected, 21 were identified as single proteins by MS, while the other 7 were shown to contain several major proteins. None of these proteins were detected in the control immunoreactive bands. The proteins identified included 11 from B. hyodysenteriae and 28 from the two B. pilosicoli strains. Eight proteins were common to the B. pilosicoli strains (i.e., elongation factor G, aspartyl-tRNA synthase, biotin lipoyl, TmpB outer membrane protein, flagellar protein FlaA, enolase, PEPCK, and VspD), and enolase and PEPCK were common to both species. Many of the identified proteins were flagellar proteins or predicted to be located on the cell surface and some of them had been previously described as antigenic or as bacterial virulence factors. Here we report on the identification and semiquantitative data of these immunoreactive proteins which constitute a unique antigen collection from these bacteria.