ORCID Profile
0000-0002-7094-3528
Current Organisation
Griffith University - Gold Coast Campus
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Microbial genetics | Epigenetics (incl. genome methylation and epigenomics) | Genetics | Genomics
Publisher: American Society for Microbiology
Date: 06-2006
Abstract: Neisseria gonorrhoeae is a host-adapted pathogen that colonizes primarily the human genitourinary tract. This bacterium encounters reactive oxygen and reactive nitrogen species as a consequence of localized inflammatory responses in the urethra of males and endocervix of females and also of the activity of commensal lactobacilli in the vaginal flora. This review describes recent advances in the understanding of defense systems against oxidative stress in N. gonorrhoeae and shows that while some of its defenses have similarities to the paradigm established with Escherichia coli , there are also some key differences. These differences include the presence of a defense system against superoxide based on manganese ions and a glutathione-dependent system for defense against nitric oxide which is under the control of a novel MerR-like transcriptional regulator. An understanding of the defenses against oxidative stress in N. gonorrhoeae and their regulation may provide new insights into the ways in which this bacterium survives challenges from polymorphonuclear leukocytes and urogenital epithelial cells.
Publisher: Elsevier BV
Date: 06-2020
Publisher: Springer Science and Business Media LLC
Date: 18-07-2017
DOI: 10.1038/S41598-017-05894-W
Abstract: Neisseria meningitidis express numerous virulence factors that enable it to interact with erse microenvironments within the host, during both asymptomatic nasopharyngeal colonization and invasive disease. Many of these interactions involve bacterial or host glycans. In order to characterise the meningococcal glycointeractome, glycan arrays representative of structures found on human cells, were used as a screening tool to investigate host glycans bound by N. meningitidis . Arrays probed with fluorescently labelled wild-type MC58 revealed binding to 223 glycans, including blood group antigens, mucins, gangliosides and glycosaminoglycans. Mutant strains lacking surface components, including capsule, lipooligosaccharide (LOS), Opc and pili, were investigated to identify the factors responsible for glycan binding. Surface plasmon resonance and isothermal calorimetry were used to confirm binding and determine affinities between surface components and host glycans. We observed that the L3 LOS immunotype (whole cells and purified LOS) bound 26 structures, while L8 only bound 5 structures. We further demonstrated a direct glycan-glycan interaction between purified L3 LOS and Thomsen–Friedenreich (TF) antigen, with a K D of 13 nM. This is the highest affinity glycan-glycan interaction reported to date. These findings highlight the erse glycointeractions that may occur during different stages of meningococcal disease, which could be exploited for development of novel preventative and therapeutic strategies.
Publisher: Elsevier BV
Date: 10-2012
Publisher: Oxford University Press (OUP)
Date: 02-2019
Abstract: The bacterial species Neisseria gonorrhoeae (NG) has evolved to replicate effectively and exclusively in human epithelia, with its survival dependent on complex interactions between bacteria, host cells and antimicrobial agents. A better understanding of these interactions is needed to inform development of new approaches to gonorrhoea treatment and prevention but empirical studies have proven difficult, suggesting a role for mathematical modelling. Here, we describe an in-host model of progression of untreated male symptomatic urethral infection, including NG growth and interactions with epithelial cells and neutrophils, informed by in vivo and in vitro studies. The model reproduces key observations on bacterial load and clearance and we use multivariate sensitivity analysis to refine plausible ranges for model parameters. Model variants are also shown to describe mouse infection dynamics with altered parameter ranges that correspond to observed differences between human and mouse infection. Our results highlight the importance of NG internalisation, particularly within neutrophils, in sustaining infection in the human model, with ∼80% of the total NG population internalised from day 25 on. This new mechanistic model of in-host NG infection dynamics should also provide a platform for future studies relating to antimicrobial treatment and resistance and infection at other anatomical sites.
Publisher: American Society for Microbiology
Date: 19-03-2020
DOI: 10.1128/MRA.00064-20
Abstract: Moraxella catarrhalis is a leading cause of otitis media and exacerbations of chronic obstructive pulmonary disease however, its response to iron starvation during infection is not completely understood. Here, we announce a sequential window acquisition of all theoretical fragment ion spectra mass spectrometry (SWATH-MS) data set describing the differential expression of the M. catarrhalis CCRI-195ME proteome under iron-restricted versus iron-replete conditions.
Publisher: Frontiers Media SA
Date: 12-12-2016
Publisher: Oxford University Press (OUP)
Date: 13-06-2017
Publisher: Wiley
Date: 14-06-2003
DOI: 10.1016/S0014-5793(03)00632-X
Abstract: Sco proteins are found in mitochondria and in a variety of oxidase positive bacteria. Although Sco is required for the formation of the Cu(A) centre in a cytochrome oxidase of the aa(3) type, it was observed that oxidases with a Cu(A) centre are not present in many bacteria that contain a Sco homologue. Two bacteria of this type are the pathogens Neisseria meningitidis and Neisseria gonorrhoeae. The sco genes of N. gonorrhoeae strain 1291 and N. meningitidis strain MC58 were cloned, inactivated by inserting a kanamycin resistance cassette and used to make knockout mutants by allelic exchange. Both N. gonorrhoeae and N. meningitidis sco mutants were highly sensitive to oxidative killing by paraquat, indicating that Sco is involved in protection against oxidative stress in these bacteria.
Publisher: Springer Science and Business Media LLC
Date: 12-02-2016
DOI: 10.1038/SREP21015
Abstract: Neisseria meningitidis is a human-specific bacterium that varies in invasive potential. All meningococci are carried in the nasopharynx, and most genotypes are very infrequently associated with invasive meningococcal disease however, those belonging to the ‘hyperinvasive lineages’ are more frequently associated with sepsis or meningitis. Genome content is highly conserved between carriage and disease isolates, and differential gene expression has been proposed as a major determinant of the hyperinvasive phenotype. Three phase variable DNA methyltransferases (ModA, ModB and ModD), which mediate epigenetic regulation of distinct phase vari able regul ons (phasevarions), have been identified in N. meningitidis . Each mod gene has distinct alleles, defined by their Mod DNA recognition domain, and these target and methylate different DNA sequences, thereby regulating distinct gene sets. Here 211 meningococcal carriage and ,400 disease isolates were surveyed for the distribution of meningococcal mod alleles. While modA11 - 12 and modB1-2 were found in most isolates, rarer alleles ( e.g., modA15, modB4, modD1-6) were specific to particular genotypes as defined by clonal complex. This suggests that phase variable Mod proteins may be associated with distinct phenotypes and hence invasive potential of N. meningitidis strains.
Publisher: Oxford University Press (OUP)
Date: 18-10-2018
DOI: 10.1093/GBE/EVY226
Publisher: American Society for Microbiology
Date: 18-01-2021
DOI: 10.1128/AAC.01542-21
Abstract: Neisseria gonorrhoeae is an increasing public health threat due to its rapidly rising incidence and antibiotic resistance. There are an estimated 106 million cases per year worldwide, there is no vaccine available to prevent infection, and N. gonorrhoeae strains that are resistant to all antibiotics routinely used to treat the infection have emerged.
Publisher: Informa UK Limited
Date: 23-01-2016
Publisher: Springer Science and Business Media LLC
Date: 17-08-2022
DOI: 10.1038/S41467-022-29931-Z
Abstract: Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disorder affecting 0.5–2% of pregnancies. The majority of cases present in the third trimester with pruritus, elevated serum bile acids and abnormal serum liver tests. ICP is associated with an increased risk of adverse outcomes, including spontaneous preterm birth and stillbirth. Whilst rare mutations affecting hepatobiliary transporters contribute to the aetiology of ICP, the role of common genetic variation in ICP has not been systematically characterised to date. Here, we perform genome-wide association studies (GWAS) and meta-analyses for ICP across three studies including 1138 cases and 153,642 controls. Eleven loci achieve genome-wide significance and have been further investigated and fine-mapped using functional genomics approaches. Our results pinpoint common sequence variation in liver-enriched genes and liver-specific cis -regulatory elements as contributing mechanisms to ICP susceptibility.
Publisher: Elsevier BV
Date: 08-2023
Publisher: Elsevier BV
Date: 02-2022
Publisher: Springer Science and Business Media LLC
Date: 12-2019
DOI: 10.1186/S12866-019-1660-Y
Abstract: Moraxella catarrhalis is a leading cause of otitis media (OM) and chronic obstructive pulmonary disease (COPD). M. catarrhalis contains a Type III DNA adenine methyltransferase (ModM) that is phase-variably expressed (i.e., its expression is subject to random, reversible ON/OFF switching). ModM has six target recognition domain alleles ( modM1–6 ), and we have previously shown that modM2 is the predominant allele, while modM3 is associated with OM. Phase-variable DNA methyltransferases mediate epigenetic regulation and modulate pathogenesis in several bacteria. ModM2 of M. catarrhalis regulates the expression of a phasevarion containing genes important for colonization and infection. Here we describe the phase-variable expression of modM3 , the ModM3 methylation site and the suite of genes regulated within the ModM3 phasevarion. Phase-variable expression of modM3 , mediated by variation in length of a 5′-(CAAC) n -3′ tetranucleotide repeat tract in the open reading frame was demonstrated in M. catarrhalis strain CCRI-195ME with GeneScan fragment length analysis and western immunoblot. We determined that ModM3 is an active N6-adenine methyltransferase that methylates the sequence 5′-AC m6 ATC-3′. Methylation was detected at all 4446 5′-ACATC-3′ sites in the genome when ModM3 is expressed. RNASeq analysis identified 31 genes that are differentially expressed between modM3 ON and OFF variants, including five genes that are involved in the response to oxidative and nitrosative stress, with potential roles in biofilm formation and survival in anaerobic environments. An in vivo chinchilla ( Chinchilla lanigera) model of otitis media demonstrated that transbullar challenge with the modM3 OFF variant resulted in an increased middle ear bacterial load compared to a modM3 ON variant. In addition, co-infection experiments with NTHi and M. catarrhalis modM3 ON or modM3 OFF variants revealed that phase variation of modM3 altered survival of NTHi in the middle ear during early and late stage infection. Phase variation of ModM3 epigenetically regulates the expression of a phasevarion containing multiple genes that are potentially important in the progression of otitis media.
Publisher: Informa UK Limited
Date: 23-02-2015
DOI: 10.1586/14760584.2015.1016915
Abstract: Neisseria meningitidis is a leading cause of meningitis and sepsis worldwide. The first broad-spectrum multicomponent vaccine against serogroup B meningococcus (MenB), 4CMenB (Bexsero(®)), was approved by the EMA in 2013, for prevention of MenB disease in all age groups, and by the US FDA in January 2015 for use in adolescents. A second protein-based MenB vaccine has also been approved in the USA for adolescents (rLP2086, Trumenba(®)). Both vaccines contain the lipoprotein factor H-binding protein (fHbp). Preclinical studies demonstrated that fHbp elicits a robust bactericidal antibody response that correlates with the amount of fHbp expressed on the bacterial surface. fHbp is able to selectively bind human factor H, the key regulator of the alternative complement pathway, and this has important implications both for meningococcal pathogenesis and for vaccine design. Here, we review the functional and structural properties of fHbp, the strategies that led to the design of the two fHbp-based vaccines and the data generated during clinical studies.
Publisher: Springer Science and Business Media LLC
Date: 22-02-2019
DOI: 10.1038/S41598-019-39374-0
Abstract: Moraxella catarrhalis is a host-adapted bacterial pathogen that causes otitis media and exacerbations of chronic obstructive pulmonary disease. This study characterises the conserved M . catarrhalis extracellular nuclease, a member of the ββα metal finger family of nucleases, that we have named NucM. NucM shares conserved sequence motifs from the ββα nuclease family, including the DRGH catalytic core and Mg 2+ co-ordination site, but otherwise shares little primary sequence identity with other family members, such as the Serratia Nuc and pneumococcal EndA nucleases. NucM is secreted from the cell and digests linear and circular nucleic acid. However, it appears that a proportion of NucM is also associated with the cell membrane and acts as an entry nuclease, facilitating transformation of M . catarrhalis cells. This is the first ex le of a ββα nuclease in a Gram negative bacteria that acts as an entry nuclease. In addition to its role in competence, NucM affects cell aggregation and biofilm formation by M . catarrhalis , with Δ nucM mutants having increased biofilm biomass. NucM is likely to increase the ability of cells to survive and persist in vivo , increasing the virulence of M . catarrhalis and potentially affecting the behaviour of other pathogens that co-colonise the otorhinolaryngological niche.
Publisher: Oxford University Press (OUP)
Date: 2002
Publisher: Oxford University Press (OUP)
Date: 15-03-2018
DOI: 10.1093/NAR/GKY192
Publisher: Elsevier
Date: 2021
Publisher: BMJ Publishing Group Ltd
Date: 07-2019
Publisher: Springer Netherlands
Date: 2012
Publisher: Microbiology Society
Date: 10-2017
DOI: 10.1099/MIC.0.000523
Abstract: Moraxella catarrhalis is a human-restricted opportunistic bacterial pathogen of the respiratory mucosa. It frequently colonizes the nasopharynx asymptomatically, but is also an important causative agent of otitis media (OM) in children, and plays a significant role in acute exacerbations of chronic obstructive pulmonary disease (COPD) in adults. As the current treatment options for M. catarrhalis infection in OM and exacerbations of COPD are often ineffective, the development of an efficacious vaccine is warranted. However, no vaccine candidates for M. catarrhalis have progressed to clinical trials, and information regarding the distribution of M. catarrhalis virulence factors and vaccine candidates is inconsistent in the literature. It is largely unknown if virulence is associated with particular strains or subpopulations of M. catarrhalis, or if differences in clinical manifestation can be attributed to the heterogeneous expression of specific M. catarrhalis virulence factors in the circulating population. Further investigation of the distribution of M. catarrhalis virulence factors in the context of carriage and disease is required so that vaccine development may be targeted at relevant antigens that are conserved among disease-causing strains. The challenge of determining which of the proposed M. catarrhalis virulence factors are relevant to human disease is lified by the lack of a standardized M. catarrhalis typing system to facilitate direct comparisons of worldwide isolates. Here we summarize and evaluate proposed relationships between M. catarrhalis subpopulations and specific virulence factors in the context of colonization and disease, as well as the current methods used to infer these associations.
Publisher: Springer Science and Business Media LLC
Date: 04-11-2019
DOI: 10.1038/S41598-019-52429-6
Abstract: Phasevarions (phase-variable regulons) are emerging as an important area of bacterial gene regulation. Many bacterial pathogens contain phasevarions, with gene expression controlled by the phase-variable expression of DNA methyltransferases via epigenetic mechanisms. Non-typeable Haemophilus influenzae (NTHi) contains the phase-variable methyltransferase modA , of which multiple allelic variants exist ( modA1-21 ). We have previously demonstrated 5 of 21 these modA alleles are overrepresented in NTHi strains isolated from children with middle ear infections. In this study we investigated the modA allele distribution in NTHi strains isolated from patients with chronic obstructive pulmonary disease, COPD. We demonstrate that the distribution of modA alleles in a large panel of COPD isolates is different to the distribution seen in middle ear infections, suggesting different modA alleles may provide distinct advantages in the differing niches of the middle ear and COPD airways. We also identified two new phase-variable modA alleles – modA15 and modA18 – and demonstrate that these alleles methylate distinct DNA sequences and control unique phasevarions. The modA15 and modA18 alleles have only been observed in COPD isolates, indicating that these two alleles may be markers for isolates likely to cause exacerbations of COPD.
Publisher: American Society for Microbiology
Date: 2009
DOI: 10.1128/IAI.01071-08
Abstract: Factor H-binding protein (fHBP GNA1870) is one of the antigens of the recombinant vaccine against serogroup B Neisseria meningitidis , which has been developed using reverse vaccinology and is the basis of a meningococcal B vaccine entering phase III clinical trials. Binding of factor H (fH), an inhibitor of the complement alternative pathway, to fHBP enables N. meningitidis to evade killing by the innate immune system. All fHBP null mutant strains analyzed were sensitive to killing in ex vivo human whole blood and serum models of meningococcal bacteremia with respect to the isogenic wild-type strains. The fHBP mutant strains of MC58 and BZ83 (high fHBP expressors) survived in human blood and serum for less than 60 min (decrease of log 10 CFU), while NZ98/254 (intermediate fHBP expressor) and 67/00 (low fHBP expressor) showed decreases of log 10 CFU after 60 to 120 min of incubation. In addition, fHBP is important for survival in the presence of the antimicrobial peptide LL-37 (decrease of log 10 CFU after 2 h of incubation), most likely due to electrostatic interactions between fHBP and the cationic LL-37 molecule. Hence, the expression of fHBP by N. meningitidis strains is important for survival in human blood and human serum and in the presence of LL-37, even at low levels. The functional significance of fHBP in mediating resistance to the human immune response, in addition to its widespread distribution and its ability to induce bactericidal antibodies, indicates that it is an important component of the serogroup B meningococcal vaccine.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2018
Publisher: American Society for Microbiology
Date: 05-2009
DOI: 10.1128/IAI.01216-08
Abstract: The well-conserved protein Hfq has emerged as the key modulator of riboregulation in bacteria. This protein is thought to function as an RNA chaperone and to facilitate base pairing between small regulatory RNA (sRNA) and mRNA targets, and many sRNAs are dependent on the Hfq protein for their regulatory functions. To address the possible role of Hfq in riboregulated circuits in Neisseria meningitidis , we generated an Hfq mutant of the MC58 strain, and the knockout mutant has pleiotropic phenotypes it has a general growth phenotype in vitro in culture media, and it is sensitive to a wide range of stresses, including those that it may encounter in the host. Furthermore, the expression profile of a vast number of proteins is clearly altered in the mutant, and we have identified 27 proteins by proteomics. All of the phenotypes tested to date are also restored by complementation of Hfq expression in the mutant strain. Importantly, in ex vivo and in vivo models of infection the Hfq mutant is attenuated. These data indicate that Hfq plays a key role in stress response and virulence, and we propose a major role for Hfq in regulation of gene expression. Moreover, this study suggests that in meningococcus there is a large Hfq-mediated sRNA network which so far is largely unexplored.
Publisher: American Society for Microbiology
Date: 27-08-2019
Abstract: Multidrug-resistant strains of Neisseria gonorrhoeae are emerging worldwide, and novel treatment and prevention strategies are needed. Glycans are ubiquitously expressed by all human cells and can be specifically targeted by pathogens to facilitate association with host cells. Here we identify and characterize the N. gonorrhoeae host-glycan binding profile (glycointeractome), which revealed numerous interactions, including high-affinity binding to mannosyl glycans. We identify gonococcal potential mannose-binding proteins and show that N. gonorrhoeae uses mannosyl glycans expressed on the surface of cervical and urethral epithelia to facilitate adherence. Furthermore, a mannose-binding lectin or a mannoside compound was able to reduce this adherence. By characterizing the glycointeractome of N. gonorrhoeae, we were able to elucidate a novel mechanism used by this important pathogen to interact with human cells, and this interaction could be exploited to develop novel therapeutics to treat antibiotic-resistant gonorrhea.
Publisher: Elsevier
Date: 2016
Publisher: Elsevier BV
Date: 03-2010
Publisher: American Society for Microbiology
Date: 02-2017
DOI: 10.1128/IAI.00898-16
Abstract: Neisseria gonorrhoeae , the causative agent of the sexually transmitted infection (STI) gonorrhea, is a growing public health threat for which a vaccine is urgently needed. We characterized the functional role of the gonococcal MetQ protein, which is the methionine binding component of an ABC transporter system, and assessed its potential as a candidate antigen for inclusion in a gonococcal vaccine. MetQ has been found to be highly conserved in all strains investigated to date, it is localized on the bacterial surface, and it binds l -methionine with a high affinity. MetQ is also involved in gonococcal adherence to cervical epithelial cells. Mutants lacking MetQ have impaired survival in human monocytes, macrophages, and serum. Furthermore, antibodies raised against MetQ are bactericidal and are able to block gonococcal adherence to epithelial cells. These data suggest that MetQ elicits both bactericidal and functional blocking antibodies and is a valid candidate antigen for additional investigation and possible inclusion in a vaccine for prevention of gonorrhea.
Publisher: Wiley
Date: 23-08-2019
Publisher: Elsevier BV
Date: 09-2006
DOI: 10.1016/J.BBRC.2006.06.182
Abstract: Pili (type IV fimbriae) of Neisseria meningitidis are glycosylated by the addition of O-linked sugars. Recent work has shown that PglF, a protein with homology to O-antigen 'flippases', is required for the biosynthesis of the pilin-linked glycan and suggests pilin glycosylation occurs in a manner analogous to the wzy-dependent addition of O-antigen to the core-LPS. O-Antigen ligases are crucial in this pathway for the transfer of undecraprenol-linked sugars to the LPS-core in Gram-negative bacteria. An O-antigen ligase homologue, pglL, was identified in N. meningitidis. PglL mutants showed no change in LPS phenotypes but did show loss of pilin glycosylation, confirming PglL is essential for pilin O-linked glycosylation in N. meningitidis.
Publisher: American Chemical Society (ACS)
Date: 12-11-2012
DOI: 10.1021/BI301161W
Abstract: The factor H binding protein (fHbp) is a key virulence factor of Neisseria meningitidis that confers to the bacterium the ability to resist killing by human serum. The determination of its three-dimensional structure revealed that the carboxyl terminus of the protein folds into an eight-stranded β barrel. The structural similarity of this part of the protein to lipocalins provided the rationale for exploring the ability of fHbp to bind siderophores. We found that fHbp was able to bind in vitro siderophores belonging to the cathecolate family and mapped the interaction site by nuclear magnetic resonance. Our results indicated that the enterobactin binding site was distinct from the site involved in binding to human factor H and stimulates new hypotheses about possible multiple activities of fHbp.
Publisher: Microbiology Society
Date: 09-2019
DOI: 10.1099/MIC.0.000805
Abstract: Phase-variable DNA methyltransferases control the expression of multiple genes via epigenetic mechanisms in a wide variety of bacterial species. These systems are called phasevarions, for phase-variable regulons. Phasevarions regulate genes involved in pathogenesis, host adaptation and antibiotic resistance. Many human-adapted bacterial pathogens contain phasevarions. These include leading causes of morbidity and mortality worldwide, such as non-typeable
Publisher: American Society for Microbiology
Date: 12-2005
DOI: 10.1128/IAI.73.12.8444-8448.2005
Abstract: Laz, a lipid-modified azurin of the human pathogens Neisseria gonorrhoeae and Neisseria meningitidis , is involved in defense against oxidative stress and copper toxicity laz mutant strains are hypersensitive to hydrogen peroxide and copper. The N. gonorrhoeae laz mutant also has decreased survival in an ex vivo primary human ectocervical epithelial assay.
Publisher: Springer New York
Date: 2019
DOI: 10.1007/978-1-4939-9202-7_8
Abstract: A growing body of evidence suggests that glycans are important for meningococcal host-pathogen interactions and virulence. The development of glycobiology techniques such as glycan array analysis and surface plasmon resonance (SPR) has increased awareness of the importance of glycans in biological processes and has increased the interest of their study. While these techniques are more routinely used with purified proteins, there is growing interest in their applicability to cell-based studies, to better emulate host-pathogen interactions in vivo. Here we describe the use of glycan array analysis and SPR for the investigation of glycan binding by Neisseria meningitidis cells. Used together, these methods can help identify and characterize N. meningitidis glycointeractions.
Publisher: Springer Science and Business Media LLC
Date: 29-10-2021
DOI: 10.1038/S41541-021-00388-3
Abstract: Infections with Neisseria meningitidis and Neisseria gonorrhoeae have different clinical manifestations, but the bacteria share up to 80–90% genome sequence identity. The recombinant meningococcal serogroup B (MenB) vaccine 4CMenB consists of four antigenic components that can be present in non-B meningococcal and gonococcal strains. This comprehensive review summarizes scientific evidence on the genotypic and phenotypic similarities between vaccine antigens and their homologs expressed by non-B meningococcal and gonococcal strains. It also includes immune responses of 4CMenB-vaccinated in iduals and effectiveness and impact of 4CMenB against these strains. Varying degrees of strain coverage were estimated depending on the non-B meningococcal serogroup and antigenic repertoire. 4CMenB elicits immune responses against non-B meningococcal serogroups and N. gonorrhoeae . Real-world evidence showed risk reductions of 69% for meningococcal serogroup W clonal complex 11 disease and 40% for gonorrhea after 4CMenB immunization. In conclusion, functional antibody activity and real-world evidence indicate that 4CMenB has the potential to provide some protection beyond MenB disease.
Publisher: Springer New York
Date: 2019
DOI: 10.1007/978-1-4939-9202-7_6
Abstract: Fragment analysis (or fragment length analysis) is a PCR-based method which allows quantification of the size and proportion of a DNA repeat tract length of a phase-variable region. Primers are labeled with a fluorescent dye, the resulting licons are processed by capillary electrophoresis, and results are analyzed for licon size and proportion by associated software (such as Peakscanner). Here we describe the process of designing primers and controls to screen for the number of repeats in a polymeric tract of a phase-variable gene in Neisseria meningitidis (the DNA methyltransferase ModA is used as an ex le, but this method can be applied to other phase-variable genes).
Publisher: CSIRO Publishing
Date: 20-10-2020
DOI: 10.1071/MA20055
Abstract: The sexually transmitted infection (STI) gonorrhoea is an ancient human disease caused by the Gram-negative bacterial pathogen Neisseria gonorrhoeae. Despite decades of research focused on preventing, diagnosing, and treating gonorrhoea, it remains a major global health concern due to its high prevalence, high rates of asymptomatic cases, the severe sequelae that can result from untreated infections, and the increasing difficulty in treating infections caused by multi-drug resistant strains of N. gonorrhoeae. It is estimated that there are more than 87 million cases of gonorrhoea worldwide each year, and the WHO, CDC and Australian National Antimicrobial Resistance (AMR) Strategy have prioritised N. gonorrhoeae as an urgent public health threat for which new therapeutics and a vaccine are needed.
Publisher: Springer Science and Business Media LLC
Date: 30-03-2023
DOI: 10.1186/S12889-023-15516-Y
Abstract: Gonorrhoea is an ongoing public health concern due to its rising incidence and the emergence of antibiotic resistance. There are an estimated 82 million new Neisseria gonorrhoeae infections each year, with several populations at higher risk for gonococcal infection, including gay and bisexual men (GBM). If left untreated, infection can lead to serious morbidity including infertility, sepsis and increased risk of HIV acquisition. Development of a gonorrhoea vaccine has been challenging, however there is observational evidence that serogroup B meningococcal vaccines, used to protect against the closely related bacteria Neisseria meningitidis , could provide cross-protection against N. gonorrhoeae. The MenGO (Meningococcal vaccine efficacy against Gonorrhoea) study is a phase III open-label randomised control trial in GBM to evaluate the efficacy of the four-component meningococcal serogroup B vaccine, 4CMenB, against gonorrhoea. A total of 130 GBM will be recruited at the Gold Coast Sexual Health Clinic, Australia, and randomised to either receive 2 doses of 4CMenB or no intervention. Participants will be followed up for 24 months with testing for N. gonorrhoeae and other sexually transmissible infections every three months. Demographics, sexual behaviour risk, antibiotic use, and blood s les for analysis of N. gonorrhoeae- specific immune responses, will be collected during the study. The primary outcome is the number of N . gonorrhoeae infections in participants over 2 years measured by nucleic acid lification test (NAAT). Secondary outcomes are vaccine-induced N. gonorrhoeae- specific immune responses, and adverse events in trial participants. This trial will determine if the 4CMenB vaccine is able to reduce N. gonorrhoeae infection. If shown to be effective, 4CMenB could be used in gonococcal prevention. Analysis of 4CMenB-induced immune responses will increase understanding of the type of immune response needed to prevent N. gonorrhoeae , which may enable identification of a potential correlate of protection to aid future gonorrhoea vaccine development. The trial has been registered on the Australian and New Zealand Clinical Trials Registry (ACTRN12619001478101) on 25 October 2019.
Publisher: Public Library of Science (PLoS)
Date: 18-06-2020
Publisher: Public Library of Science (PLoS)
Date: 08-05-2014
Publisher: American Society for Microbiology
Date: 07-2014
DOI: 10.1128/AAC.00004-14
Abstract: Phase variation is a common feature of host-adapted bacterial pathogens such as Neisseria meningitidis . Recently, we reported that this rapid on/off switching of gene expression occurs in DNA methyltransferases, altering expression in multiple genes via changes in global methylation. In the current study, we compared MIC values of strains with ModA11, ModA12, and ModD1 phasevarions, revealing MIC differences due to ModA11 and ModA12 switching, with a ModA11_OFF strain showing 4-fold reduced susceptibilities to ceftazidime and ciprofloxacin.
Publisher: American Society for Microbiology
Date: 27-04-2021
Abstract: The emergence of multidrug-resistant N. gonorrhoeae strains that are resistant to available antimicrobials is a current health emergency, and no vaccine is available to prevent gonococcal infection. Lipooligosaccharide (LOS) is one of the major virulence factors of N. gonorrhoeae .
Publisher: Elsevier BV
Date: 05-2019
DOI: 10.1016/J.BBRC.2019.03.092
Abstract: Pseudomonas aeruginosa is an opportunistic pathogen that causes nosocomial infections most commonly in immunocompromised, cystic fibrosis (CF) and burns patients. The pilin and Pseudomonas lectins 1 (PA-IL) and 2 (PA-IIL) are known glycan-binding proteins of P. aeruginosa that are involved in adherence to host cells, particularly CF host airways. Recently, new P. aeruginosa surface proteins were identified by reverse vaccinology and tested in vivo as potential vaccine antigens. Three of these, namely PSE17-1, PSE41-5 and PSE54, were screened for glycan binding using glycan arrays displaying glycan structures representative of those found on human cells. Surface plasmon resonance was used to confirm the lectin activity of these proteins, and determined affinities with several host glycans to be in the nanomolar range. PSE17-1 binds hyaluronic acid and sialyl Lewis A and X. PSE41-5 binds terminal β-linked galactose structures, Lewis and ABO blood group antigens. PSE54 binds to ABO blood group antigens and some terminal β-linked galactose. All three proteins are novel lectins of P. aeruginosa with potential roles in infection of host cells.
Publisher: Public Library of Science (PLoS)
Date: 25-10-2016
Publisher: Public Library of Science (PLoS)
Date: 26-10-2009
Publisher: Cold Spring Harbor Laboratory
Date: 05-2013
Publisher: Informa UK Limited
Date: 30-03-2023
Publisher: Elsevier BV
Date: 09-2017
Publisher: Wiley
Date: 04-01-2019
DOI: 10.1002/PPUL.24231
Publisher: Oxford University Press (OUP)
Date: 06-04-2015
DOI: 10.1093/NAR/GKV219
Publisher: BMJ Publishing Group Ltd
Date: 07-2017
Publisher: Proceedings of the National Academy of Sciences
Date: 23-02-2010
Abstract: GNA2132 is a Neisseria meningitidis antigen of unknown function, discovered by reverse vaccinology, which has been shown to induce bactericidal antibodies in animal models. Here we show that this antigen induces protective immunity in humans and it is recognized by sera of patients after meningococcal disease. The protein binds heparin in vitro through an Arg-rich region and this property correlates with increased survival of the unencapsulated bacterium in human serum. Furthermore, two proteases, the meningococcal NalP and human lactoferrin, cleave the protein upstream and downstream from the Arg-rich region, respectively. We conclude that GNA2132 is an important protective antigen of N. meningitidis and we propose to rename it, N eisserial H eparin B inding A ntigen (NHBA).
Publisher: Springer Science and Business Media LLC
Date: 19-12-2017
DOI: 10.1038/S41598-017-17850-9
Abstract: Streptococcus pneumoniae is a leading cause of morbidity and mortality globally. The Pilus-1 proteins, RrgA, RrgB and RrgC of S. pneumoniae have been previously assessed for their role in infection, invasive disease and as possible vaccine candidates. In this study we have investigated the glycan binding repertoire of all three Pilus-1 proteins, identifying that the tip adhesin RrgA has the broadest glycan recognition of the three proteins, binding to maltose/cellobiose, α/β linked galactose and blood group A and H antigens. RrgB only bound mannose, while RrgC bound a subset of glycans also recognized by RrgA. Adherence of S. pneumoniae TIGR4 to epithelial cells was tested using four of the oligosaccharides identified through the glycan array analysis as competitive inhibitors. The blood group H trisaccharide provided the best blocking of S. pneumoniae TIGR4 adherence. Adherence is the first step in disease, and host glycoconjugates are a common target for many adhesins. This study has identified Pilus-1 proteins as new lectins involved in the targeting of host glycosylation by S. pneumoniae .
Publisher: Springer US
Date: 17-11-2022
DOI: 10.1007/978-1-0716-1900-1_19
Abstract: There is no vaccine available to prevent Neisseria gonorrhoeae infection, however there is currently a high level of interest in developing gonococcal vaccines due to the increasing number of cases and continuing emergence of antimicrobial resistance worldwide. A key aspect of vaccine development is the investigation of the functional immune response raised to the vaccine targets under investigation. Here, we describe two assays used to assess the functional immune response raised against gonococcal vaccine targets: the serum bactericidal assay (SBA) and the opsonophagocytic assay (OPA).
Publisher: Elsevier BV
Date: 08-2018
Publisher: Wiley
Date: 27-09-2019
Publisher: Elsevier BV
Date: 03-2010
DOI: 10.1016/J.VACCINE.2009.12.082
Abstract: A novel vaccine against serogroup B meningococcal disease - containing a combination of protein antigens identified by reverse vaccinology: fHBP fused to GNA2091, GNA2132 fused to GNA1030, and NadA - is currently in Phase III clinical trials. In order to determine the role of these antigens in the growth, survival and fitness of the meningococcus, we generated a mutant lacking the expression of all five protein antigens (5KO), a mutant lacking the three main antigens (fHBP, GNA2132 and NadA 3KO), as well as strains lacking the single antigens. Our results show that abrogation of expression of these antigens in Neisseria meningitidis results in reduced growth in vitro, increased sensitivity of the bacterium to stresses it may encounter in the host, as well as reduced fitness in ex vivo models of infection and in an in vivo infant rat competitive index assay. These results support a multivalent vaccine approach, which was undertaken to strengthen the protective activity of the vaccine antigens, increase the breadth of MenB strains targeted by the vaccine, and limit the potential for selection of vaccine escape mutants.
Publisher: Wiley
Date: 03-03-2006
DOI: 10.1111/J.1365-2958.2006.05079.X
Abstract: In previous studies it has been established that resistance to superoxide by Neisseria gonorrhoeae is dependent on the accumulation of Mn(II) ions involving the ABC transporter, MntABC. A mutant strain lacking the periplasmic binding protein component (MntC) of this transport system is hypersensitive to killing by superoxide anion. In this study the mntC mutant was found to be more sensitive to H2O2 killing than the wild-type. Analysis of regulation of MntC expression revealed that it was de-repressed under low Mn(II) conditions. The N. gonorrhoeae mntABC locus lacks the mntR repressor typically found associated with this locus in other organisms. A search for a candidate regulator of mntABC expression revealed a homologue of PerR, a Mn-dependent peroxide-responsive regulator found in Gram-positive organisms. A perR mutant expressed more MntC protein than wild-type, and expression was independent of Mn(II), consistent with a role for PerR as a repressor of mntABC expression. The PerR regulon of N. gonorrhoeae was defined by microarray analysis and includes ribosomal proteins, TonB-dependent receptors and an alcohol dehydrogenase. Both the mntC and perR mutants had reduced intracellular survival in a human cervical epithelial cell model.
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/MA15048
Publisher: Wiley
Date: 04-11-2008
DOI: 10.1111/J.1365-2958.2008.06468.X
Abstract: Mechanisms for coping with oxidative stress (OS) are crucial for the survival of pathogenic Neisseria spp. in the human host. In this study we investigate the mechanism by which OxyR finely regulates the catalase gene (kat) in Neisseria meningitidis. Detailed transcriptional analyses show that catalase is transcribed from a single promoter that is induced by H(2)O(2) in an OxyR-dependent manner and two key cysteine residues are essential for this. OxyR also represses the kat promoter: kat expression in the null mutant is at a constitutive intermediary level higher than uninduced, but lower than H(2)O(2)-induced levels in the wild type. Our data are consistent with a model in which OxyR binds to the kat promoter and exerts: (i) repression of transcription in the absence of OS signal and (ii) activation of the promoter in response to OS signal. This direct double-edged mechanism may ensure tight regulatory control of kat expression ensuring catalase is synthesized only when needed. In addition, our results provide an explanation for the altered OS resistance phenotypes seen in Neisseria mutant strains where, paradoxically, the oxyR mutants are more resistant than the wild type in oxidative killing assays.
Publisher: Wiley
Date: 20-10-2007
DOI: 10.1111/J.1365-2958.2006.05478.X
Abstract: OxyR regulates the expression of the majority of H(2)O(2) responses in Gram-negative organisms. In a previous study we reported the OxyR-dependent derepression of catalase expression in the human pathogen Neisseria gonorrhoeae. In the present study we used microarray expression profiling of N. gonorrhoeae wild-type strain 1291 and an oxyR mutant strain to define the OxyR regulon. In addition to katA (encoding catalase), only one other locus displayed a greater than two-fold difference in expression in the wild type : oxyR comparison. This locus encodes an operon of two genes, a putative peroxiredoxin/glutaredoxin (Prx) and a putative glutathione oxidoreductase (Gor). Mutant strains were constructed in which each of these genes was inactivated. A previous biochemical study in Neisseria meningitidis had confirmed function of the glutaredoxin eroxiredoxin. Assay of the wild-type 1291 cell free extract confirmed Gor activity, which was lost in the gor mutant strain. Phenotypic analysis of the prx mutant strain in H(2)O(2) killing assays revealed increased resistance, presumably due to upregulation of alternative defence mechanisms. The oxyR, prx and gor mutant strains were deficient in biofilm formation, and the oxyR and prx strains had decreased survival in cervical epithelial cells, indicating a key role for the OxyR regulon in these processes.
Publisher: Wiley
Date: 02-09-2014
DOI: 10.1096/FJ.14-256578
Abstract: Moraxella catarrhalis is a significant cause of otitis media and exacerbations of chronic obstructive pulmonary disease. Here, we characterize a phase-variable DNA methyltransferase (ModM), which contains 5'-CAAC-3' repeats in its open reading frame that mediate high-frequency mutation resulting in reversible on/off switching of ModM expression. Three modM alleles have been identified (modM1-3), with modM2 being the most commonly found allele. Using single-molecule, real-time (SMRT) genome sequencing and methylome analysis, we have determined that the ModM2 methylation target is 5'-GAR(m6)AC-3', and 100% of these sites are methylated in the genome of the M. catarrhalis 25239 ModM2 on strain. Proteomic analysis of ModM2 on and off variants revealed that ModM2 regulates expression of multiple genes that have potential roles in colonization, infection, and protection against host defenses. Investigation of the distribution of modM alleles in a panel of M. catarrhalis strains, isolated from the nasopharynx of healthy children or middle ear effusions from patients with otitis media, revealed a statistically significant association of modM3 with otitis media isolates. The modulation of gene expression via the ModM phase-variable regulon (phasevarion), and the significant association of the modM3 allele with otitis media, suggests a key role for ModM phasevarions in the pathogenesis of this organism.
Publisher: Annual Reviews
Date: 08-09-2020
DOI: 10.1146/ANNUREV-MICRO-090817-062346
Abstract: Human-adapted bacterial pathogens use a mechanism called phase variation to randomly switch the expression of in idual genes to generate a phenotypically erse population to adapt to challenges within and between human hosts. There are increasing reports of restriction-modification systems that exhibit phase-variable expression. The outcome of phase variation of these systems is global changes in DNA methylation. Analysis of phase-variable Type I and Type III restriction-modification systems in multiple human-adapted bacterial pathogens has demonstrated that global changes in methylation regulate the expression of multiple genes. These systems are called phasevarions (phase-variable regulons). Phasevarion switching alters virulence phenotypes and facilitates evasion of host immune responses. This review describes the characteristics of phasevarions and implications for pathogenesis and immune evasion. We present and discuss ex les of phasevarion systems in the major human pathogens Haemophilus influenzae, Neisseria meningitidis, Neisseria gonorrhoeae, Helicobacter pylori, Moraxella catarrhalis, and Streptococcus pneumoniae.
Publisher: Frontiers Media SA
Date: 06-02-2019
Publisher: Springer Science and Business Media LLC
Date: 29-10-2021
Publisher: Elsevier BV
Date: 2022
Publisher: Future Medicine Ltd
Date: 03-2018
Publisher: Oxford University Press (OUP)
Date: 14-07-2017
Abstract: The pathogenic Neisseria provide textbook ex les of phase variation: the high frequency, random and reversible switching of gene expression. Typically, phase variable gene expression is observed in genes required for the expression of surface proteins and carbohydrate structures. All Neisseria gonorrhoeae and N. meningitidis strains also express phase variable DNA methyltransferases that are components of DNA restriction-modification systems. Phase variation of these DNA methyltransferases (Mod) alters global DNA methylation patterns. The change in DNA methylation due to phase variation events alters expression of a regulon of genes, called a phasevarion, and results in differentiation of the population into cells with two distinct phenotypes. For ex le, in N. meningitidis switching of the modA11 phasevarion alters expression of immunogenic outer membrane proteins such as lactoferrin-binding protein, and also modulates sensitivity to ceftazidime and ciprofloxacin. The modD1 phasevarion is associated with hypervirulent meningococcal clonal complexes. In N. gonorrhoeae, modA13 phasevarion switching generates differentiation into cells that display enhanced biofilm formation and enhanced intracellular survival. Phasevarions are ubiquitous in pathogenic Neisseria and modulate expression of numerous genes. These systems have the potential to impact all studies on vaccine development and pathobiology in the pathogenic Neisseria.
Publisher: Proceedings of the National Academy of Sciences
Date: 28-02-2011
Abstract: Molecular data on a limited number of chromosomal loci have shown that the population of Neisseria meningitidis ( Nm ), a deadly human pathogen, is structured in distinct lineages. Given that the Nm population undergoes substantial recombination, the mechanisms resulting in the evolution of these lineages, their persistence in time, and the implications for the pathogenicity of the bacterium are not yet completely understood. Based on whole-genome sequencing, we show that Nm is structured in phylogenetic clades. Through acquisition of specific genes and through insertions and rearrangements, each clade has acquired and remodeled specific genomic tracts, with the potential to impact on the commensal and virulence behavior of Nm . Despite this clear evidence of a structured population, we confirm high rates of detectable recombination throughout the whole Nm chromosome. However, gene conversion events were found to be longer within clades than between clades, suggesting a DNA cleavage mechanism associated with the phylogeny of the species. We identify 22 restriction modification systems, probably acquired by horizontal gene transfer from outside of the species/genus, whose distribution in the different strains coincides with the phylogenetic clade structure. We provide evidence that these clade-associated restriction modification systems generate a differential barrier to DNA exchange consistent with the observed population structure. These findings have general implications for the emergence of lineage structure and virulence in recombining bacterial populations, and they could provide an evolutionary framework for the population biology of a number of other bacterial species that show contradictory population structure and dynamics.
Publisher: American Society for Microbiology
Date: 19-07-2018
DOI: 10.1128/MRA.00821-18
Abstract: Nontypeable Haemophilus influenzae (NTHi) is an important bacterial pathogen that causes otitis media and exacerbations of chronic obstructive pulmonary disease (COPD). Here, we report the complete genome sequences of NTHi strains 10P129H1 and 84P36H1, isolated from COPD patients, which contain the phase-variable epigenetic regulators ModA15 and ModA18, respectively.
Publisher: Elsevier BV
Date: 08-2015
Publisher: Microbiology Society
Date: 08-2019
DOI: 10.1099/JMM.0.001033
Abstract: Moraxella catarrhalis is an important but insufficiently studied respiratory pathogen. To determine antibiotic susceptibility and impact of recent antibiotics on M. catarrhalis from children with chronic endobronchial suppuration. We cultured nasopharyngeal (NP) swabs and bronchoalveolar lavage (BAL) fluids collected from children who were prospectively enrolled in studies of chronic cough and had flexible bronchoscopy performed. Recent β-lactam or macrolide antibiotic use was recorded. M. catarrhalis isolates stored at -80 °C were re-cultured and susceptibility determined to a range of antibiotics including the macrolide antibiotic erythromycin. Data from concurrently collected NP and BAL specimens were available from 547 children (median age 2.4 years) enrolled from 2007 to 2016. M. catarrhalis NP carriage was detected in 149 (27 %) children and lower airway infection (≥10 Despite the frequent use of macrolides, few macrolide-resistant isolates were detected. This suggests a fitness cost associated with macrolide resistance in M. catarrhalis. Macrolide antibiotics remain an effective choice for treating M. catarrhalis lower airway infection in children with chronic endobronchial suppuration.
Publisher: Frontiers Media SA
Date: 30-06-2022
DOI: 10.3389/FCIMB.2022.909888
Abstract: Neisseria gonorrhoeae and Neisseria meningitidis are human-specific pathogens in the Neisseriaceae family that can cause devastating diseases. Although both species inhabit mucosal surfaces, they cause dramatically different diseases. Despite this, they have evolved similar mechanisms to survive and thrive in a metal-restricted host. The human host restricts, or overloads, the bacterial metal nutrient supply within host cell niches to limit pathogenesis and disease progression. Thus, the pathogenic Neisseria require appropriate metal homeostasis mechanisms to acclimate to such a hostile and ever-changing host environment. This review discusses the mechanisms by which the host allocates and alters zinc, manganese, and copper levels and the ability of the pathogenic Neisseria to sense and respond to such alterations. This review will also discuss integrated metal homeostasis in N. gonorrhoeae and the significance of investigating metal interplay.
Publisher: Oxford University Press (OUP)
Date: 29-11-2020
Abstract: The sexually transmitted infection gonorrhoea is on the rise worldwide and an increased understanding of the mechanisms of colonization and pathogenesis of Neisseria gonorrhoeae is required to aid development of new treatment and prevention strategies. In the current study, we investigate the neisserial heparin-binding antigen (NHBA) of N. gonorrhoeae and confirm its role in binding to several glycans, including heparin, and identify interactions of NHBA with both gonococcal and host cells. Furthermore, we report that a gonococcal nhba mutant displays decreased cell aggregation and microcolony formation, as well as reduced survival in human serum and reduced adherence to human cervical and urethral epithelial cells, relative to the wild-type strain. These data indicate that the gonococcal NHBA contributes to several aspects of the colonization and survival of N. gonorrhoeae and may be a target for new antimicrobial or vaccines.
Publisher: American Society for Microbiology
Date: 08-2005
DOI: 10.1128/IAI.73.8.5269-5272.2005
Abstract: Neisseria gonorrhoeae has well-characterized oxidative stress defense systems that protect against oxidative killing in in vitro assays. In contrast, mutant strains of N. gonorrhoeae lacking oxidative stress defenses are identical to the wild type when tested in an ex vivo survival assay using human polymorphonuclear leukocytes.
Publisher: MDPI AG
Date: 13-05-2020
Abstract: Due to the continuing emergence of multidrug resistant strains of Neisseria gonorrhoeae there is an urgent need for the development of a gonococcal vaccine. We evaluated the gonococcal Neisseria heparin binding antigen (NHBA) as a potential vaccine candidate, in terms of its sequence conservation and expression in a range of N. gonorrhoeae strains, as well as its immunogenicity and the functional activity of antibodies raised to either the full length NHBA or a C-terminal fragment of NHBA (NHBA-c). The gene encoding NHBA is highly conserved and expressed in all N. gonorrhoeae strains investigated. Recombinant NHBA is immunogenic, and mice immunized with either NHBA or NHBA-c adjuvanted with either Freund’s or aluminium hydroxide (alum) generated a humoral immune response, with predominantly IgG1 antibodies. Antibodies generated by both NHBA and NHBA-c antigens promoted complement activation and mediated bacterial killing via both serum bactericidal activity and opsonophagocytic activity, with slightly higher titers seen for the NHBA-c antigen. Anti-NHBA was also able to block the functional activity of NHBA by reducing binding to heparin and adherence to cervical and urethral epithelial cells. These data suggest that the gonococcal NHBA is a promising vaccine antigen to include in a vaccine to control N. gonorrhoeae.
Publisher: Springer Science and Business Media LLC
Date: 25-04-2018
DOI: 10.1038/S41598-018-24639-X
Abstract: Neisseria meningitidis is a Gram-negative bacterial pathogen that causes life threatening meningitis and septicemia. Neisseria Heparin Binding Antigen (NHBA) is an outer membrane protein that binds heparin and heparan sulfate and DNA. This protein is one of the four antigens in the meningococcal serogroup B vaccine Bexsero. In the current study, we sought to define the full glycan-binding repertoire of NHBA to better understand its role in meningococcal pathogenesis and vaccine efficacy. Glycan array analysis revealed binding to 28 structures by recombinant NHBA. Surface plasmon resonance was used to confirm the binding phenotype and to determine the affinity of the interactions. These studies revealed that the highest affinity binding of NHBA was with chondroitin sulfate (K D = 5.2 nM). This affinity is 10-fold higher than observed for heparin. Analysis of binding with well-defined disaccharides of the different chondroitin sulfate types demonstrated that the most preferred ligand has a sulfate at the 2 position of the GlcA/IdoA and 6 position of the GalNAc, which is an equivalent structure to chondroitin sulfate D. Chondroitin sulfate is widely expressed in human tissues, while chondroitin sulfate D is predominantly expressed in the brain and may constitute a new receptor structure for meningococci.
Publisher: Portland Press Ltd.
Date: 24-07-2019
DOI: 10.1042/BST20180633
Abstract: Phase-variation of genes is defined as the rapid and reversible switching of expression — either ON-OFF switching or the expression of multiple allelic variants. Switching of expression can be achieved by a number of different mechanisms. Phase-variable genes typically encode bacterial surface structures, such as adhesins, pili, and lipooligosaccharide, and provide an extra contingency strategy in small-genome pathogens that may lack the plethora of ‘sense-and-respond’ gene regulation systems found in other organisms. Many bacterial pathogens also encode phase-variable DNA methyltransferases that control the expression of multiple genes in systems called phasevarions (phase-variable regulons). The presence of phase-variable genes allows a population of bacteria to generate a number of phenotypic variants, some of which may be better suited to either colonising certain host niches, surviving a particular environmental condition and/or evading an immune response. The presence of phase-variable genes complicates the determination of an organism's stably expressed antigenic repertoire many phase-variable genes are highly immunogenic, and so would be ideal vaccine candidates, but unstable expression due to phase-variation may allow vaccine escape. This review will summarise our current understanding of phase-variable genes that switch expression by a variety of mechanisms, and describe their role in disease and pathobiology.
Publisher: American Society for Microbiology
Date: 05-2019
DOI: 10.1128/IAI.00093-19
Abstract: Nontypeable Haemophilus influenzae (NTHi) is a major human pathogen, responsible for several acute and chronic infections of the respiratory tract. The incidence of invasive infections caused by NTHi is increasing worldwide.
Publisher: Elsevier BV
Date: 07-2022
Publisher: Elsevier BV
Date: 10-2020
Publisher: American Society for Microbiology
Date: 18-07-2019
DOI: 10.1128/MRA.00526-19
Abstract: Nontypeable Haemophilus influenzae (NTHi) is a major bacterial cause of exacerbations in chronic obstructive pulmonary disease (COPD). Here, we report high-depth coverage transcriptome sequencing (RNA-seq) data from two NTHi strains, each encoding a different phase-variable methyltransferase. modA phase variation results in gene expression differences. These data will serve as an important resource for future studies.
Publisher: BMJ
Date: 04-2016
Publisher: American Society for Microbiology
Date: 02-04-2020
DOI: 10.1128/MRA.01559-19
Abstract: Moraxella catarrhalis is a leading bacterial cause of otitis media and exacerbations of chronic obstructive pulmonary disease. Here, we announce a transcriptome RNA sequencing data set detailing global gene expression in two M. catarrhalis CCRI-195ME variants with expression of the DNA methyltransferase ModM3 phase varied either on or off.
Publisher: American Society for Microbiology
Date: 03-2019
DOI: 10.1128/IAI.00676-18
Abstract: Clostridium difficile is a major cause of hospital-acquired antibiotic-associated diarrhea. C. difficile produces two cytotoxins, TcdA and TcdB both toxins are multidomain proteins that lead to cytotoxicity through the modification and inactivation of small GTPases of the Rho/Rac family.
Publisher: Oxford University Press (OUP)
Date: 07-2004
DOI: 10.1086/421299
Publisher: Wiley
Date: 16-06-2011
DOI: 10.1096/FJ.11-183590
Abstract: Neisseria meningitidis is a major cause of septicemia and meningitis. The hypervirulent clonal complex 41/44 (cc41/44) has emerged as the predominant cause of serogroup B meningococcal disease, having been responsible for recent outbreaks and epidemics worldwide. However, the meningococcal factors that enable transition from asymptomatic carriage to rapidly progressing disease are poorly understood. Here we describe a novel phase-variable DNA methyltransferase, ModD, which was identified in the genome sequence of a New Zealand epidemic isolate. Investigation of the distribution of modD in the wider meningococcal population, by PCR and sequence analysis of genetically erse N. meningitidis strains, revealed the presence of modD in 20/27 strains in cc41/44, but in only 2/47 strains from other clonal complexes, indicating a significant association of modD with cc41/44 (Fisher's exact P value=3×10(-10)). The modD gene contains 5'-ACCGA-3' repeats that mediate phase variation, leading to reversible on/off switching of modD expression. Microarray analysis of modD-on/off variants revealed that ModD regulates expression of multiple genes involved in colonization, infection, and protection against host defenses, with increased catalase expression in the modD-on variant conferring increased resistance to oxidative stress. The modulation of gene expression via the ModD phase-variable regulon (phasevarion), and its significant association with the cc41/44, suggest a role in the fitness and/or pathogenesis of strains belonging to the cc41/44.
Publisher: BMJ
Date: 09-2015
Publisher: American Society for Microbiology
Date: 02-2011
DOI: 10.1128/IAI.00891-10
Abstract: Neisseria meningitidis is a commensal of the human nasopharynx but is also a major cause of septicemia and meningitis. The meningococcal factor H binding protein (fHbp) binds human factor H (fH), enabling downregulation of complement activation on the bacterial surface. fHbp is a component of two serogroup B meningococcal vaccines currently in clinical development. Here we characterize 12 fHbp subvariants for their level of surface exposure and ability to bind fH, to mediate serum resistance, and to induce bactericidal antibodies. Flow cytometry and Western analysis revealed that all strains examined expressed fHbp on their surface to different extents and bound fH in an fHbp-dependent manner. However, differences in fH binding did not always correlate with the level of fHbp expression, indicating that this is not the only factor affecting the amount of fH bound. To overcome the issue of strain variability in fHbp expression, the MC58Δ fHbp strain was genetically engineered to express different subvariants from a constitutive heterologous promoter. These recombinant strains were characterized for fH binding, and the data confirmed that each subvariant binds different levels of fH. Surface plasmon resonance revealed differences in the stability of the fHbp-fH complexes that ranged over 2 orders of magnitude, indicating that differences in residues between and within variant groups can influence fH binding. Interestingly, the level of survival in human sera of recombinant MC58 strains expressing erse subvariants did not correlate with the level of fH binding, suggesting that the interaction of fHbp with fH is not the only function of fHbp that influences serum resistance. Furthermore, cross-reactive bactericidal activity was seen within each variant group, although the degree of activity varied, suggesting that amino acid differences within each variant group influence the bactericidal antibody response.
Publisher: Public Library of Science (PLoS)
Date: 24-04-2009
Publisher: Oxford University Press (OUP)
Date: 14-12-2018
DOI: 10.1093/CID/CIY1061
Abstract: Neisseria gonorrhoeae and Neisseria meningitidis are closely-related bacteria that cause a significant global burden of disease. Control of gonorrhoea is becoming increasingly difficult, due to widespread antibiotic resistance. While vaccines are routinely used for N. meningitidis, no vaccine is available for N. gonorrhoeae. Recently, the outer membrane vesicle (OMV) meningococcal B vaccine, MeNZB, was reported to be associated with reduced rates of gonorrhoea following a mass vaccination c aign in New Zealand. To probe the basis for this protection, we assessed the cross-reactivity to N. gonorrhoeae of serum raised to the meningococcal vaccine Bexsero, which contains the MeNZB OMV component plus 3 recombinant antigens (Neisseria adhesin A, factor H binding protein [fHbp]-GNA2091, and Neisserial heparin binding antigen [NHBA]-GNA1030). A bioinformatic analysis was performed to assess the similarity of MeNZB OMV and Bexsero antigens to gonococcal proteins. Rabbits were immunized with the OMV component or the 3 recombinant antigens of Bexsero, and Western blots and enzyme-linked immunosorbent assays were used to assess the generation of antibodies recognizing N. gonorrhoeae. Serum from humans immunized with Bexsero was investigated to assess the nature of the anti-gonococcal response. There is a high level of sequence identity between MeNZB OMV and Bexsero OMV antigens, and between the antigens and gonococcal proteins. NHBA is the only Bexsero recombinant antigen that is conserved and surfaced exposed in N. gonorrhoeae. Bexsero induces antibodies in humans that recognize gonococcal proteins. The anti-gonococcal antibodies induced by MeNZB-like OMV proteins could explain the previously-seen decrease in gonorrhoea following MeNZB vaccination. The high level of human anti-gonococcal NHBA antibodies generated by Bexsero vaccination may provide additional cross-protection against gonorrhoea.
Publisher: Public Library of Science (PLoS)
Date: 05-05-2011
Publisher: American Society for Microbiology
Date: 25-05-2017
Abstract: Moraxella catarrhalis is an important bacterial pathogen that causes otitis media and exacerbations of chronic obstructive pulmonary disease. Here, we report the complete genome sequence of M. catarrhalis strain CCRI-195ME, which contains the phase-variable epigenetic regulator ModM3.
Publisher: American Society for Clinical Investigation
Date: 09-2009
DOI: 10.1172/JCI38330
Start Date: 2023
End Date: 12-2025
Amount: $680,663.00
Funder: Australian Research Council
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