1,720,984 research outputs found
Application for consent to release a GMO – organisms other than higher plants: Experimental challenge of the human nasopharynx with recombinant Neisseria lactamica expressing the meningococcal type V autotransporter protein, Neisseria Adhesin A (NadA).
No full textThe purpose of the genetic modification is to construct a strain of the exclusively human, nasopharyngeal commensal bacterium, Neisseria lactamica (Nlac) that expresses on its surface the outer membrane protein, Neisseria Adhesin A (NadA). NadA is an adhesin protein found in the close relative of Nlac, Neisseria meningitidis (Nmen), which is the causative agent of meningococcal disease. The genetically modified organism (GMO) will be used to investigate the role of NadA in the colonisation of the nasopharynx and associated immune responses in a controlled human bacterial challenge. The Experimental Human Challenge group, previously based at the University of Sheffield and now located at the University of Southampton, has conducted two previous human bacterial challenges in adult volunteers, using wild type Nlac strain, Y92-1009. The primary objective of the proposed study is to verify that nasopharyngeal challenge of humans with GM-Nlac is safe. Secondary objectives are determining the impact of NadA expression on the frequency of nasopharyngeal colonisation by GM-Nlac and the type(s) of immune responses generated locally and systemically to these bacteria. Ultimately this strategy may confer benefit as a bacterial medicine expressing genes with therapeutic or prophylactic potential within the human nasopharynx
Dataset for thesis Colonisation dynamics of Bordetella pertussis and Neisseria lactamica in the nasopharynx during experimental asymptomatic infection in humans
No full textDataset for the thesis Colonisation dynamics of Bordetella pertussis and Neisseria lactamica in the nasopharynx during experimental asymptomatic infection in humans. Data in Excel spreadsheets.</span
Neisserial molecular adaptations to the nasopharyngeal niche
No full textThe exclusive reservoir of the genus Neisseria is the human. Of the broad range of species that comprise the Neisseria, only two are frequently pathogenic, and only one of those is a resident of the nasopharynx. Although Neisseria meningitidis can cause severe disease if it invades the bloodstream, the vast majority of interactions between humans and Neisseria are benign, with the bacteria inhabiting its mucosal niche as a non-invasive commensal. Understandably, with the exception of Neisseria gonorrhoeae, which preferentially colonises the urogenital tract, the neisseriae are extremely well adapted to survival in the human nasopharynx, their sole biological niche. The purpose of this review is to provide an overview of the molecular mechanisms evolved by Neisseria to facilitate colonisation and survival within the nasopharynx, focussing on N. meningitidis. The organism has adapted to survive in aerosolised transmission and to attach to mucosal surfaces. It then has to replicate in a nutrition-poor environment and resist immune and competitive pressure within a polymicrobial complex. Temperature and relative gas concentrations (nitric oxide and oxygen) are likely to be potent initial signals of arrival within the nasopharyngeal environment, and this review will focus on how N. meningitidis responds to these to increase the likelihood of its survival.</p
Chemiluminescence quantification of NO and its derivatives in liquid samples
No full textNitric oxide (NO) is a ubiquitous gas with potent biological effects, including vasodilation, neuronal signaling, and antimicrobial activity. NO is a free radical and can readily react with other molecules, in particular, iron centers and oxygen. At physiological concentrations in aqueous solutions, even in the presence of oxygen, NO is reasonably stable. Under these conditions, NO is oxidized almost exclusively to nitrite (NO2-). In cell lysates and tissue extracts with iron-containing proteins, however, NO is postulated to have a very short half-life, with the major oxidation product being nitrate (NO3-). In mammalian cells, NO is generated via the action of the NO synthases (NOS), of which there are three known isotypes. NO can also be generated from the chemical decomposition of S-nitrosothiols, and there is some indication that naturally occurring S-nitrosothiols, such as S-nitrosoalbumin, may be natural reservoirs of NO in vivo. Here we describe a methodology to measure variations in NO in liquid samples using chemiluminescence. The protocols described allow us to distinguish between various products of NO chemistry, thus providing a sensitive method of measurement of NO concentration within a sample. They also allow us to distinguish between the various products that may be generated when NO reacts with molecules in complex biological samples such as cell lysates and supernatants
A putative amino acid ABC transporter substrate-binding protein, NMB1612, from Neisseria meningitidis, induces murine bactericidal antibodies against meningococci expressing heterologous NMB1612 proteins
No full textThe nmb1612 (NEIS1533) gene encoding the ~27-kDa putative amino acid ATP-binding cassette (ABC) transporter, periplasmic substrate-binding protein from Neisseria meningitidis serogroup B (MenB) strain MC58 was cloned and expressed in Escherichia coli, and the purified recombinant (r)NMB1612 was used for animal immunization studies. Immunization of mice with rNMB1612 adsorbed to Al(OH)3 and in liposomes with and without MPLA, induced antiserum with bactericidal activity in an assay using baby rabbit complement, against the homologous strain MC58 (encoding protein representative of Allele 62) and killed heterologous strains encoding proteins of three other alleles (representative of Alleles 1, 64 and 68), with similar SBA titres. However, strain MC58 was not killed (titre <4) in a human serum bactericidal assay (hSBA) using anti-rNMB1612 sera, although another strain (MC168) expressing the same protein was killed (median titres of 16-64 in the hSBA). Analysis of the NMB1612 amino acid sequences from 4351 meningococcal strains in the pubmlst.org/Neisseria database and a collection of 13 isolates from colonized individuals and from patients, showed that antibodies raised against rNMB1612 could potentially kill at least 72% of the MenB strains in the complete sequence database. For MenB disease occurring specifically in the UK from 2013 to 2015, >91% of the isolates causing disease in this recent period expressed NMB1612 protein encoded by Allele 1 and could be potentially killed by sera raised to the recombinant antigen in the current study. The NMB1612 protein was surface-accessible and expressed by different meningococcal strains. In summary, the properties of (i) NMB1612 protein conservation and expression, (ii) limited amino acid sequence variation between proteins encoded by different alleles, and (iii) the ability of a recombinant protein to induce cross-strain bactericidal antibodies, would all suggest a promising antigen for consideration for inclusion in new meningococcal vaccines
Metabolism of nitric oxide by Neisseria meningitidis modifies release of NO-regulated cytokines and chemokines by human macrophages
No full textMacrophages produce nitric oxide (NO) via the inducible nitric oxide synthase as part of a successful response to infection. The gene norB of Neisseria meningitidis encodes a NO reductase which enables utilization and consumption of NO during microaerobic respiration and confers resistance to nitrosative stress-related killing by human monocyte-derived macrophages (MDM). In this study we confirmed that NO regulates cytokine and chemokine release by resting MDM: accumulation of TNF-alpha, IL-12, IL-10, CCL5 (RANTES) and CXCL8 (IL-8) in MDM supernatants was significantly modified by the NO-donor S-nitroso-N-penicillamine (SNAP). Using a protein array, infection of MDM with N. meningitidis was shown to be associated with secretion of a wide range of cytokines and chemokines. To test whether NO metabolism by N. meningitidis modifies release of NO-regulated cytokines, we infected MDM with wild-type organisms and an isogenic norB strain. Resulting expression of the cytokines TNF-alpha and IL-12, and the chemokine CXCL8 was increased and production of the cytokine IL-10 and the chemokine CCL5 was decreased in norB-infected MDM, in comparison to wild-type. Addition of SNAP to cultures infected with wild-type mimicked the effect observed in cultures infected with the norB mutant. In conclusion, NorB-catalysed removal of NO modifies cellular release of NO-regulated cytokines and chemokines.</p
Nitric oxide releases intracellular zinc from prokaryotic metallothionein in Escherichia coli
No full textNitric oxide (NO) has a broad spectrum of signalling and regulatory functions and multiple molecular targets. Recently, the intrabacterial toxicity of NO and mechanisms for NO resistance have been intensively investigated. Here we report for the first time that NO elicits release of zinc from a bacterial protein. Using the zinc-responsive expression of zntA (encoding a Zn-exporting P-type ATPase) fused to lacZ, i.e. Phi(zntA-lacZ), to monitor intracellular zinc, and SmtA (the Synechococcus metallothionein) as zinc store, we have shown that the NO donors NOC-5 and NOC-7 elicit zinc ejection. No increase in Phi(zntA-lacZ) activity was observed in a zntR mutant, indicating the specificity of the zntA promoter response to zinc ions.</p
Manipulating the infant respiratory microbiomes to improve clinical outcomes: A review of the literature
Full text linkBACKGROUND: The association between infant respiratory microbiota and disease (including respiratory tract infections and asthma) is increasingly recognised, although the mechanism remains unclear. Respiratory infections and asthma account for a large proportion of infant morbidity and mortality, so the possibility of preventing disease or modifying clinical outcomes by manipulating microbiome development warrants investigation.OBJECTIVES AND METHODS: We identified studies that investigated the efficacy of live bacteria (probiotics or human challenge) or their substrates to modify respiratory colonisation or clinical outcomes in infants.ELIGIBILITY CRITERIA: Interventional studies involving infants under one year of age, administration of live bacteria or their substrates, and outcome measures including bacterial colonisation, microbiome profile, or respiratory disease phenotypes.RESULTS AND LIMITATIONS: Some bacterial interventions can reduce infant respiratory infections, although none have been shown to reduce asthma incidence. The literature is heterogeneous in design and quality, precluding meaningful meta-analysis.CONCLUSIONS: Upper respiratory tract infant microbiome manipulation may alter outcomes in respiratory tract infection, but further well-conducted research is needed to confirm this. Improved regulation of proprietary bacterial products is essential for further progress.</p
Lactamica 9: Clinical study protocol. Defining upper respiratory colonisation and microbiome evolution in mother-infant pairs following Neisseria lactamica inoculation in late pregnancy
No full text
- …
