Two centuries of meningococcal infection: from Vieusseux to the cellular and molecular basis of disease

Peptidoglycan-binding protein TsaP functions in surface assembly of type IV pili

Type IV pili (T4P) are ubiquitous and versatile bacterial cell surface structures involved in adhesion to host cells, biofilm formation, motility, and DNA uptake. In Gram-negative bacteria, T4P pass the outer membrane (OM) through the large, oligomeric, ring-shaped secretin complex. In the β-proteobacterium Neisseria gonorrhoeae, the native PilQ secretin ring embedded in OM sheets is surrounded by an additional peripheral structure, consisting of a peripheral ring and seven extending spikes. To unravel proteins important for formation of this additional structure, we identified proteins that are present with PilQ in the OM. One such protein, which we name T4P secretin-associated protein (TsaP), was identified as a phylogenetically widely conserved component of the secretin complex that co-occurs with genes for T4P in Gram-negative bacteria. TsaP contains an N-terminal carbohydrate-binding lysin motif (LysM) domain and a C-terminal domain of unknown function. In N. gonorrhoeae, lack of TsaP results in the formation of membrane protrusions containing multiple T4P, concomitant with reduced formation of surface-exposed T4P. Lack of TsaP did not affect the oligomeric state of PilQ, but resulted in loss of the peripheral structure around the PilQ secretin. TsaP binds peptidoglycan and associates strongly with the OM in a PilQ-dependent manner. In the δ-proteobacterium Myxococcus xanthus, TsaP is also important for surface assembly of T4P, and it accumulates and localizes in a PilQ-dependent manner to the cell poles. Our results show that TsaP is a novel protein associated with T4P function and suggest that TsaP functions to anchor the secretin complex to the peptidoglycan.

Is there a place for cerebral preconditioning in the clinic?

Preconditioning (PC) describes a phenomenon whereby a sub-injury inducing stress can protect against a later injurious stress. Great strides have been made in identifying the mechanisms of PC-induced protection in animal models of brain injury. While these may help elucidate potential therapeutic targets, there are questions over the clinical utility of cerebral PC, primarily because of questions over the need to give the PC stimulus prior to the injury, narrow therapeutic windows and safety. The object of this review is to address the question of whether there may indeed be a clinical use for cerebral PC and to discuss the deficiencies in our knowledge of PC that may hamper such clinical translation.

Vaccines against meningococcal serogroup B disease containing outer membrane vesicles (OMV): lessons from past programs and implications for the future

The utility of wild-type outer membrane vesicle (wtOMV) vaccines against serogroup B (MenB) meningococcal disease has been explored since the 1970s. Public health interventions in Cuba, Norway and New Zealand have demonstrated that these protein-based vaccines can prevent MenB disease. Data from large clinical studies and retrospective statistical analyses in New Zealand give effectiveness estimates of at least 70%. A consistent pattern of moderately reactogenic and safe vaccines has been seen with the use of approximately 60 million doses of three different wtOMV vaccine formulations. The key limitation of conventional wtOMV vaccines is their lack of broad protective activity against the large diversity of MenB strains circulating globally. The public health intervention in New Zealand (between 2004–2008) when MeNZB was used to control a clonal MenB epidemic, provided a number of new insights regarding international and public-private collaboration, vaccine safety surveillance, vaccine effectiveness estimates and communication to the public. The experience with wtOMV vaccines also provide important information for the next generation of MenB vaccines designed to give more comprehensive protection against multiple strains.

Post-genomics of Neisseria meningitidis: an update

Neisseria meningitidis infection still remains a major life-threatening bacterial disease worldwide. The availability of bacterial genomic sequences generated a paradigm shift in microbiological and vaccines sciences, and post-genomics (comparative genomics, functional genomics, proteomics and a combination/evolution of these techniques) played important roles in elucidating bacterial biological complexity and pathogenic traits, at the same time accelerating the development of therapeutic drugs and vaccines. This article summarizes the most recent technological and scientific advances in meningococcal biology and pathogenesis aimed at the development and characterization of vaccines against the pathogenic meningococci.

Genome sequence of Neisseria meningitidis serogroup B strain H44/76

Neisseria meningitidis is an obligate human pathogen. While it is a frequent commensal of the upper respiratory tract, in some individuals the bacterium spreads to the bloodstream, causing meningitis and/or sepsis, which are serious conditions with high morbidity and mortality. Here we report the availability of the genome sequence of the widely used serogroup B laboratory strain H44/76.

Expression of Toll-like receptor 4 on peripheral blood mononuclear cells and its effects on patients with acute myocardial infarction treated with thrombolysis

BACKGROUND AND AIMS

TLR4 has been shown to mediate inflammation in animal models of myocardial ischemia/reperfusion injury (MI/RI). Here we hypothesized that TLR4 on peripheral blood mononuclear cells (PBMCs) may be involved in the inflammatory response in this type of clinical event.

METHODS

Seventy two patients with acute myocardial infarction (AMI) who underwent thrombolysis were assigned into reperfusion group (n = 43) and non-reperfusion group (n = 29) according to recanalization of infarct-related artery (IRA) and 40 healthy volunteers were enrolled in this experiment. Eight mL of venous blood was taken from all patients 0 h before and 2, 6, 12, and 24 h after thrombolysis. Flow cytometry (FCM) was used to detect TLR4 protein expression and real-time quantitative RT-PCR was performed to determine TLR4 mRNA and myeloid differentiation protein-88 (Myd88) mRNA expression. The concentration of tumor necrosis factor-α (TNF-α) in plasma was evaluated using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Compared with controls, all detected indicators in AMI patients were upregulated before thrombolysis (p <0.01). After thrombolysis, they were further increased. In reperfusion group, all attained their peaks in earlier hours and the peak values were lower compared with non-reperfusion group. In both cases, either reperfusion or non-perfusion, TLR4 mRNA expression was positively correlated with the levels of Myd88 mRNA (r = 0.886 and 0.694, p <0.01), respectively.

CONCLUSIONS

TLR4 expression on PBMCs was markedly elevated in AMI patients either reperfused or non-reperfused. Inflammatory reaction by activated TLR4 in MI/RI in patients may be through TLR4-Myd88-dependent signal pathway.

Mapping of the Neisseria meningitidis NadA cell-binding site: relevance of predicted {alpha}-helices in the NH2-terminal and dimeric coiled-coil regions

NadA is a trimeric autotransporter protein of Neisseria meningitidis belonging to the group of oligomeric coiled-coil adhesins. It is implicated in the colonization of the human upper respiratory tract by hypervirulent serogroup B N. meningitidis strains and is part of a multiantigen anti-serogroup B vaccine. Structure prediction indicates that NadA is made by a COOH-terminal membrane anchor (also necessary for autotranslocation to the bacterial surface), an intermediate elongated coiled-coil-rich stalk, and an NH(2)-terminal region involved in cell interaction. Electron microscopy analysis and structure prediction suggest that the apical region of NadA forms a compact and globular domain. Deletion studies proved that the NH(2)-terminal sequence (residues 24 to 87) is necessary for cell adhesion. In this study, to better define the NadA cell binding site, we exploited (i) a panel of NadA mutants lacking sequences along the coiled-coil stalk and (ii) several oligoclonal rabbit antibodies, and their relative Fab fragments, directed to linear epitopes distributed along the NadA ectodomain. We identified two critical regions for the NadA-cell receptor interaction with Chang cells: the NH(2) globular head domain and the NH(2) dimeric intrachain coiled-coil α-helices stemming from the stalk. This raises the importance of different modules within the predicted NadA structure. The identification of linear epitopes involved in receptor binding that are able to induce interfering antibodies reinforces the importance of NadA as a vaccine antigen.

Identification of a novel anti-sigmaE factor in Neisseria meningitidis

Background

Fine tuning expression of genes is a prerequisite for the strictly human pathogen Neisseria meningitidis to survive hostile growth conditions and establish disease. Many bacterial species respond to stress by using alternative σ factors which, in complex with RNA polymerase holoenzyme, recognize specific promoter determinants. σ^E, encoded by rpoE (NMB2144) in meningococci, is known to be essential in mounting responses to environmental challenges in many pathogens. Here we identified genes belonging to the σ^E regulon of meningococci.

Results

We show that meningococcal σ^E is part of the polycistronic operon NMB2140-NMB2145 and autoregulated. In addition we demonstrate that σ^E controls expression of methionine sulfoxide reductase (MsrA/MsrB). Moreover, we provide evidence that the activity of σ^E is under control of NMB2145, directly downstream of rpoE. The protein encoded by NMB2145 is structurally related to anti-sigma domain (ASD) proteins and characterized by a zinc containing anti-σ factor (ZAS) motif, a hall mark of a specific class of Zn^2+-binding ASD proteins acting as anti-σ factors. We demonstrate that Cys residues in ZAS, as well as the Cys residue on position 4, are essential for anti-σ^E activity of NMB2145, as found for a minority of members of the ZAS family that are predicted to act in the cytoplasm and responding to oxidative stimuli. However, exposure of cells to oxidative stimuli did not result in altered expression of σ^E.

Conclusions

Together, our results demonstrate that meningococci express a functional transcriptionally autoregulated σ^E factor, the activity of which is controlled by a novel meningococcal anti-σ factor belonging to the ZAS family.

The 1932 Macau epidemic of cerebrospinal meningitis: a historical perspective and critical review of the data

Since the first clinical description by Vieusseux (1805) of the epidemic form of meningitis known today as cerebrospinal meningitis, numerous epidemic outbreaks of the disease were reported globally during the nineteenth and early twentieth century. Historical medical data confirmed that clinical disease may occur either sporadically or in an epidemic form. Moreover, it may afflict children, young military recruits and/or populations living under crowded conditions. In 1932, an epidemic of meningitis occurred in Macau. The disease was sufficiently unusual to justify the publication of a special report by the Portuguese physician in charge of the control services of the epidemic. Here we present a critical review of the Macau epidemic data.

Modulation of immune responses through direct activation of Toll-like receptors to T cells

Toll-like receptors (TLRs), which are a family of pattern recognition receptors (PRRs), are involved critically in the generation and regulation of innate immunity as well as initiation of subsequent adaptive immune responses. However, recent research results showed that different subsets of T cells express certain types of TLRs during development and activation stages. Importantly, TLRs participate in the direct regulation of adaptive immune response, possibly as co-stimulatory molecules. In this review we summarize recent studies about the novel regulation of TLRs on the homeostasis and immunity of different T cell subtypes including CD4+CD25+T regulatory cells (Treg) and interleukin (IL)-17-producing CD4+T cells (T helper type 17). The direct involvement of TLRs in T cell-mediated immunity prompted us to reconsider the role of TLRs in the occurrence of autoimmune diseases, infectious diseases and graft rejection. The important effects of TLRs in T cell-intrinsic components also prompt us to explore novel vaccine adjuvants for modifying desired immune responses in an efficient way.

Postgenomics of Neisseria meningitidis: an update

Neisseria meningitidis infection represents a major life-threatening bacterial disease worldwide. Genomics has revolutionized every aspect of the field of microbiology. As a consequence of genome sequencing, the postgenomic era commenced 15 years ago. Comparative genomics, functional genomics and proteomics, as well as a combination of these techniques, will play important roles in providing vital information regarding bacterial biological complexity and pathogenic traits, and accelerate the development of therapeutic drugs and vaccines for combating infections. This review summarizes the current knowledge regarding different approaches aimed to shed light on meningococcal biology and pathogenesis, and to accelerate the development and characterization of vaccines against pathogenic meningococci.

Molecular characterization and identification of proteins regulated by Hfq in Neisseria meningitidis

Hfq is a highly conserved pleiotropically acting prokaryotic RNA-binding protein involved in the post-transcriptional regulation of many stress-responsive genes by small RNAs. In this study, we show that Hfq of the strictly human pathogen Neisseria meningitidis is involved in the regulation of expression of components involved in general metabolic pathways, iron metabolism and virulence. A meningococcal hfq deletion strain (H44/76Deltahfq) is impaired in growth in nutrient-rich media and does not grow at all in nutrient-limiting medium. The growth defect was complemented by expression of hfq in trans. Using proteomics, the expression of 28 proteins was found to be significantly affected upon deletion of hfq. Of these, 20 proteins are involved in general metabolism, among them seven iron-responsive genes. Two proteins (PilE, TspA) are involved in adherence to human cells, a step crucial for the onset of disease. One of the differentially expressed proteins, GdhA, was identified as an essential virulence factor for establishment of sepsis in an animal model, studied earlier. These results show that in N. meningitidis Hfq is involved in the regulation of a variety of components contributing to the survival and establishment of meningococcal disease.

Cloning and characterisation of dihydrodipicolinate synthase from the pathogen Neisseria meningitidis

Neisseria meningitidis is an obligate commensal bacterium of humans, and also an important human pathogen. To facilitate future drug studies, we report here the biochemical and structural characterisation of a key enzyme in (S)-lysine biosynthesis, dihydrodipicolinate synthase (DHDPS), from N. meningitidis (NmeDHDPS). X-ray crystallography revealed only minor structural differences between NmeDHDPS and the enzyme from E. coli at the active and allosteric effector sites. The catalytic capabilities of NmeDHDPS are similar to those of the enzyme from E. coli, but intriguingly NmeDHDPS is subject to substrate inhibition by high concentrations of the second substrate, (S)-aspartate semialdehyde, and is also significantly more sensitive to feedback inhibition by (S)-lysine. This heightened sensitivity to inhibition at both active and allosteric sites suggests that it may be possible to target DHDPS from N. meningitidis for antibiotic development.