Hervé Lécuyer

Meningococcal type IV pili recruit the polarity complex to cross the brain endothelium.

Breaking the Barrier Being able to deliver drugs into the brain to treat degenerative diseases such as Alzheimers or Parkinsons requires the ability to traverse the blood-brain barrier (BBB). Understanding the formation of the very specific adherent junctions (AJ) and tight junctions present at the BBB cell junctions is a prerequisite to the design of such therapeutics. However, diminishing the expression of any one component involved in the formation of these intercellular junctions destroys them. Coureuil et al. (p. 83, published online 11 June) exploited the specific recruitment of AJ proteins by Neisseria meningitidis to dissect this process. Adhesion of the bacteria to human brain endothelial cells recruited the polarity complex Par3/Par6/PKCζ required for the establishment of eukaryotic cell polarity and the formation of intercellular junctions. The bacterial recruitment of the polarity complex depleted junctional proteins at the cell-cell interface opening the intercellular junctions at the brainendothelial interface. Adhesion of bacteria to cells lining blood vessels in the brain induces them to part and allows pathogen invasion. Type IV pili mediate the initial interaction of many bacterial pathogens with their host cells. In Neisseria meningitidis, the causative agent of cerebrospinal meningitis, type IV pili–mediated adhesion to brain endothelial cells is required for bacteria to cross the blood-brain barrier. Here, type IV pili–mediated adhesion of N. meningitidis to human brain endothelial cells was found to recruit the Par3/Par6/PKCζ polarity complex that plays a pivotal role in the establishment of eukaryotic cell polarity and the formation of intercellular junctions. This recruitment leads to the formation of ectopic intercellular junctional domains at the site of bacteria–host cell interaction and a subsequent depletion of junctional proteins at the cell-cell interface with opening of the intercellular junctions of the brain-endothelial interface.

Meningococcus Hijacks a β2-Adrenoceptor/β-Arrestin Pathway to Cross Brain Microvasculature Endothelium

Following pilus-mediated adhesion to human brain endothelial cells, meningococcus (N. meningitidis), the bacterium causing cerebrospinal meningitis, initiates signaling cascades, which eventually result in the opening of intercellular junctions, allowing meningeal colonization. The signaling receptor activated by the pathogen remained unknown. We report that N. meningitidis specifically stimulates a biased β2-adrenoceptor/β-arrestin signaling pathway in endothelial cells, which ultimately traps β-arrestin-interacting partners, such as the Src tyrosine kinase and junctional proteins, under bacterial colonies. Cytoskeletal reorganization mediated by β-arrestin-activated Src stabilizes bacterial adhesion to endothelial cells, whereas β-arrestin-dependent delocalization of junctional proteins results in anatomical gaps used by bacteria to penetrate into tissues. Activation of β-adrenoceptor endocytosis with specific agonists prevents signaling events downstream of N. meningitidis adhesion and inhibits bacterial crossing of the endothelial barrier. The identification of the mechanism used for hijacking host cell signaling machineries opens perspectives for treatment and prevention of meningococcal infection.

Evaluation of the Andromas Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry System for Identification of Aerobically Growing Gram-Positive Bacilli

ABSTRACT Matrix-associated laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) is a rapid and simple microbial identification method. Previous reports using the Biotyper system suggested that this technique requires a preliminary extraction step to identify Gram-positive rods (GPRs), a technical issue that may limit the routine use of this technique to identify pathogenic GPRs in the clinical setting. We tested the accuracy of the MALDI-TOF MS Andromas strategy to identify a set of 659 GPR isolates representing 16 bacterial genera and 72 species by the direct colony method. This bacterial collection included 40 C. diphtheriae, 13 C. pseudotuberculosis, 19 C. ulcerans, and 270 other Corynebacterium isolates, 32 L. monocytogenes and 24 other Listeria isolates, 46 Nocardia, 75 Actinomyces, 18 Actinobaculum, 11 Propionibacterium acnes, 18 Propionibacterium avidum, 30 Lactobacillus, 21 Bacillus, 2 Rhodococcus equi, 2 Erysipelothrix rhusiopathiae, and 38 other GPR isolates, all identified by reference techniques. Totals of 98.5% and 1.2% of non-Listeria GPR isolates were identified to the species or genus level, respectively. Except for L. grayi isolates that were identified to the species level, all other Listeria isolates were identified to the genus level because of highly similar spectra. These data demonstrate that rapid identification of pathogenic GPRs can be obtained without an extraction step by MALDI-TOF mass spectrometry.

Carbapenem-Hydrolyzing GES-Type Extended-Spectrum β-Lactamase in Acinetobacter baumannii

ABSTRACT Acinetobacter baumannii isolate AP was recovered from a bronchial lavage of a patient hospitalized in Paris, France. A. baumannii AP was resistant to all β-lactams, including carbapenems, and produced the extended-spectrum β-lactamase (ESBL) GES-14, which differs from GES-1 by two substitutions, Gly170Ser and Gly243Ala. Cloning of the bla GES-14 gene followed by its expression in Escherichia coli showed that GES-14 compromised significantly the efficacy of all β-lactams, including cephalosporins, aztreonam, and carbapenems. The carbapenemase activity of purified GES-14 was confirmed by kinetic studies. The bla GES-14 gene was located into a class 1 integron structure and located onto a ca. 95-kb self-transferable plasmid. This study identified a very broad-spectrum β-lactamase in A. baumannii.

PER-7, an Extended-Spectrum β-Lactamase with Increased Activity toward Broad-Spectrum Cephalosporins in Acinetobacter baumannii

ABSTRACT Acinetobacter baumannii isolate AP2 was recovered from a bronchial lavage sample of a patient hospitalized in Paris, France. A. baumannii AP2 was resistant to all β-lactams, including carbapenems, and expressed the extended-spectrum β-lactamase (ESBL) PER-7, which differs from PER-1 by 4 amino acid substitutions. Compared to PER-1, PER-7 possessed higher-level hydrolytic activities against cephalosporins and aztreonam. The blaPER-7 gene was chromosomally located and associated with a mosaic class 1 integron structure. Additionally, isolate AP2 expressed the carbapenem-hydrolyzing oxacillinase OXA-23 and the 16S RNA methylase ArmA, conferring high-level resistance to aminoglycosides.

Two Strikingly Different Signaling Pathways Are Induced by Meningococcal Type IV Pili on Endothelial and Epithelial Cells

ABSTRACT Following adhesion on brain microvasculature, Neisseria meningitidis is able to cross the blood-brain barrier (BBB) by recruiting the polarity complex and the cell junction proteins, thus allowing the opening of the paracellular route. This feature is the consequence of the activation by the type IV pili of the β2-adrenergic receptor/β-arrestin signaling pathway. Here, we have extended this observation to primary peripheral endothelial cells, and we report that the interaction of N. meningitidis with the epithelium is strikingly different. The recruitment of the junctional components by N. meningitidis is indeed restricted to endothelial cell lines, and no alteration of the cell-cell junctions can be seen in epithelial monolayers following meningococcal type IV pilus-mediated colonization. Consistently, the β2-adrenergic receptor/β-arrestin pathway was not hijacked by bacteria adhering on epithelial cells. In addition, we showed that the consequences of the bacterial signaling on epithelial cells is different from that of endothelial cells, since N. meningitidis-induced signaling which protects the microcolonies from shear stress on endothelial cells is unable to do so on epithelial cells. Finally, we report that the minor pilin PilV, which has been shown to be essential for endothelial cell response, is not a required bacterial determinant to induce an epithelial cell response. These data demonstrate that even though pilus-mediated signaling induces an apparently similar cortical plaque, in epithelial and endothelial cell lineages, the signaling pathways are strikingly different in both models.

Mechanism of meningeal invasion by Neisseria meningitidis

The blood-cerebrospinal fluid barrier physiologically protects the meningeal spaces from blood-borne bacterial pathogens, due to the existence of specialized junctional interendothelial complexes. Few bacterial pathogens are able to reach the subarachnoidal space and among those, Neisseria meningitidis is the one that achieves this task the most constantly when present in the bloodstream. Meningeal invasion is a consequence of a tight interaction of meningococci with brain endothelial cells. This interaction, mediated by the type IV pili, is responsible for the formation of microcolonies on the apical surface of the cells. This interaction is followed by the activation of signaling pathways in the host cells leading to the formation of endothelial docking structures resembling those elicited by the interaction of leukocytes with endothelial cells during extravasation. The consequence of these bacterial-induced signaling events is the recruitment of intercellular junction components in the docking structure and the subsequent opening of the intercellular junctions.

HIV-1 DNA Levels in Peripheral Blood Mononuclear Cells and Cannabis Use are Associated With Intermittent HIV Shedding in Semen of Men Who Have Sex With Men on Successful Antiretroviral Regimens

BACKGROUND Few data exist on the efficacy of combined antiretroviral therapy (cART) in semen of human immunodeficiency virus type 1 (HIV-1) infected men who have sex with men (MSM) with sustained control of HIV replication in blood. METHODS HIV-1 infected MSM on successful cART for >6 months were enrolled. HIV-RNA was quantified in seminal plasma (spVL) and in blood plasma (bpVL) from 2 paired samples collected 4 weeks apart. Relationship between spVL and bpVL (measured by an ultrasensitive assay, LOQ 10 copies/mL), total peripheral blood mononuclear cells (PBMC)-associated HIV-DNA, sexually transmitted infections (STIs), and self-reported socio-behavioral characteristics was assessed using GEE logistic regression. RESULTS In total, 157 patients were included. Median time with bpVL <50 copies/mL was 3.3 years. spVL was detectable in 23/304 samples (prevalence 7.6%). Median spVL was 145 cp/mL (100-1475). spVL was detectable on the first, on the second, and on both samples in 5, 14, and 2 men, respectively. In sum, 33 individuals (21%) had STIs (asymptomatic in 24/33). Residual bpVL was undetectable by ultrasensitive assay in 225/300 samples (75%). After multivariable adjustments, PBMC-associated HIV-DNA (OR 2.6[1.2; 6.0], for HIV-DNA > 2.5 log10 cp/10(6) PBMC, P = .02), and cannabis use during sexual intercourse (OR 2.8[1.2; 6.7], P = .02) were the only factors associated significantly with spVL. CONCLUSION We show that HIV-RNA can be detected intermittently in semen of HIV-1 infected MSM despite successful cART. The size of blood HIV-1 reservoir predicted spVL detection. Our results indicated also that the possible effect of cannabis should be taken into account when developing prevention interventions targeted toward HIV-infected MSM on successful cART.

A journey into the brain: insight into how bacterial pathogens cross blood–brain barriers

The blood–brain barrier, which is one of the tightest barriers in the body, protects the brain from insults, such as infections. Indeed, only a few of the numerous blood-borne bacteria can cross the blood–brain barrier to cause meningitis. In this Review, we focus on invasive extracellular pathogens, such as Neisseria meningitidis, Streptococcus pneumoniae, group B Streptococcus and Escherichia coli, to review the obstacles that bacteria have to overcome in order to invade the meninges from the bloodstream, and the specific skills they have developed to bypass the blood–brain barrier. The medical importance of understanding how these barriers can be circumvented is underlined by the fact that we need to improve drug delivery into the brain.

Chronic Meningococcemia Cutaneous Lesions Involve Meningococcal Perivascular Invasion Through the Remodeling of Endothelial Barriers

Chronic meningococcemia is a form of sepsis with frequent polymorphous skin lesions. Both in vivo and in vitro data suggest that, in these lesions, meningococci gain access from the capillary lumen to the peripheral extravascular compartment, in the absence of vascular dislocation, through a paraendothelial route.