13 results found
Siris S, Gladstone CA, Guo Y, et al., 2021, Isolating Pathogen-Specific Human Monoclonal Antibodies (hmAbs) Using Bacterial Whole Cells as Molecular Probes., Methods Mol Biol, Vol: 2183, Pages: 9-18
The immunoglobulin capture assay (ICA) enables the enrichment for pathogen-specific plasmablasts from individuals with a confirmed adaptive immune response to vaccination or disseminated infection. Only single recombinant antigens have been used previously as probes in this ICA and it was unclear whether the method was applicable to complex probes such as whole bacterial cells. Here, we describe the enrichment of plasmablasts specific for polysaccharide and protein antigens of both Streptococcus pneumoniae and Neisseria meningitidis using whole formalin-fixed bacterial cells as probes. The modified ICA protocol described here allowed for a pathogen-specific hmAb cloning efficiency of >80%.
Mashbat B, Bellos E, Hodeib S, et al., 2020, A rare mutation in SPLUNC1 underlies meningococcal disease affecting bacterial adherence and invasion, Clinical Infectious Diseases, Vol: 70, Pages: 2045-2053, ISSN: 1058-4838
BackgroundNeisseriameningitidis (Nm) is a nasopharyngeal commensal carried by healthy individuals. However, invasive infections occurs in a minority of individuals, with devastating consequences. There is evidence that common polymorphisms are associated with invasive meningococcal disease (IMD) but the contribution of rare variants other than complement has not been determined.MethodsWe identified familial cases of IMD in the UK meningococcal disease study and the European Union Life-threatening Infectious Disease Study. Candidate genetic variants were identified by whole exome sequencing of two patients with familial IMD. Candidate variants were further validated by in vitro assays.ResultsExomes of two siblings with IMD identified a novel heterozygous missense mutation in BPIFA1/SPLUNC1. Sequencing of 186 other non-familial cases identified another unrelated IMD patient with the same mutation. SPLUNC1 is an innate immune defence protein expressed in the nasopharyngeal epithelia, however, its role in invasive infections is unknown. In vitro assays demonstrated that recombinant SPLUNC1 inhibits biofilm formation by Nm, and impedes Nm adhesion and invasion of human airway cells. The dominant negative mutant rSPLUNC1 (p.G22E) showed reduced anti-biofilm activity, increased meningococcal adhesion and invasion of cells compared with wild type SPLUNC1.ConclusionsA mutation in SPLUNC1 affecting mucosal attachment, biofilm formation and invasion of mucosal epithelial cells is a new genetic cause of meningococcal disease.
Bidmos FA, Siris S, Gladstone C, et al., 2018, Bacterial vaccine antigen discovery in the reverse vaccinology 2.0 era: progress and challenges, Frontiers in Immunology, Vol: 9, ISSN: 1664-3224
The ongoing, and very serious, threat from antimicrobial resistance necessitates the development and use of preventative measures, predominantly vaccination. Polysaccharide-based vaccines have provided a degree of success in limiting morbidity from disseminated bacterial infections, including those caused by the major human obligate pathogens, Neisseria meningitidis and Streptococcus pneumoniae. Limitations of these polysaccharide vaccines, such as partial coverage and induced escape leading to persistence of disease, provide a compelling argument for the development of protein vaccines. In this review, we briefly chronicle approaches that have yielded licensed vaccines before highlighting reverse vaccinology 2.0 and its potential application in the discovery of novel bacterial protein vaccine candidates. Technical challenges and research gaps are also discussed.
Bidmos FA, Nadel S, Screaton GR, et al., 2018, Cross-reactive bactericidal antimeningococcal antibodies can be isolated from convalescing invasive Meningococcal disease patients using reverse vaccinology 2.0, Frontiers in Immunology, Vol: 9, ISSN: 1664-3224
The threat from invasive meningococcal disease remains a serious source of concern despite the licensure and availability of vaccines. A limitation of currently-available serogroup B vaccines is the breadth of coverage afforded, resulting from the capacity for extensive variation of the meningococcus and its huge potential for the generation of further diversity. Thus, the continuous search for candidate antigens that will compose supplementary or replacement vaccines is mandated. Here, we describe successful efforts to utilize the reverse vaccinology 2.0 approach to identify novel functionally-immunogenic meningococcal antigens. In this study, eight broadly cross-reactive sequence-specific anti-meningococcal human monoclonal antibodies (hmAbs) were cloned from 4 ml of blood taken from a 7-month old sufferer of invasive meningococcal disease (IMD). Three of these hmAbs possessed human complement-dependent bactericidal activity against meningococcal serogroup B strains of disparate PorA and 4CMenB antigen sequence types, strongly suggesting that the target(s) of these bactericidal hmAbs are not PorA (the immunodominant meningococcal antigen), factor-H binding protein (fHbp) or other components of currently-available meningococcal vaccines. Reactivity of the bactericidal hmAbs was confirmed to a single ca. 35 kDa protein in western blots. Unequivocal identification of this antigen is currently ongoing. Collectively, our results provide proof-of-principle for the use of reverse vaccinology 2.0 as a powerful tool in the search for alternative meningococcal vaccine candidate antigens.
Mashbat B, Bellos E, Bidmos F, et al., 2018, Whole exome sequencing identifies BPIFA1 mutation underlying invasive meningococcal disease, Human Genome Meeting 2018, Publisher: BIOMED CENTRAL LTD, ISSN: 1473-9542
Bidmos FA, Chan H, Praekelt U, et al., 2015, Investigation into the Antigenic Properties and Contributions to Growth in Blood of the Meningococcal Haemoglobin Receptors, HpuAB and HmbR., PLOS One, Vol: 10, ISSN: 1932-6203
Acquisition of iron from host complexes is mediated by four surface-located receptors of Neisseria meningitidis. The HmbR protein and heterodimeric HpuAB complex bind to haemoglobin whilst TbpBA and LbpBA bind iron-loaded transferrin and lactoferrin complexes, respectively. The haemoglobin receptors are unevenly distributed; disease-causing meningococcal isolates encode HmbR or both receptors while strains with only HpuAB are rarely-associated with disease. Both these receptors are subject to phase variation and 70-90% of disease isolates have one or both of these receptors in an ON expression state. The surface-expression, ubiquity and association with disease indicate that these receptors could be potential virulence factors and vaccine targets. To test for a requirement during disease, an hmbR deletion mutant was constructed in a strain (MC58) lacking HpuAB and in both a wild-type and TbpBA deletion background. The hmbR mutant exhibited an identical growth pattern to wild-type in whole blood from healthy human donors whereas growth of the tbpBA mutant was impaired. These results suggest that transferrin is the major source of iron for N. meningitidis during replication in healthy human blood. To examine immune responses, polyclonal antisera were raised against His-tagged purified-recombinant variants of HmbR, HpuA and HpuB in mice using monolipopolysaccharide as an adjuvant. Additionally, monoclonal antibodies were raised against outer membrane loops of HmbR presented on the surface of EspA, an E. coli fimbrial protein. All antisera exhibited specific reactivity in Western blots but HmbR and HpuA polyclonal sera were reactive against intact meningococcal cells. None of the sera exhibited bactericidal activity against iron-induced wild-type meningococci. These findings suggest that the HmbR protein is not required during the early stages of disease and that immune responses against these receptors may not be protective.
Alamro M, Bidmos FA, Chan H, et al., 2014, Phase Variation Mediates Reductions in Expression of Surface Proteins during Persistent Meningococcal Carriage, INFECTION AND IMMUNITY, Vol: 82, Pages: 2472-2484, ISSN: 0019-9567
Bidmos FA, Bayliss CD, 2014, Genomic and global approaches to unravelling how hypermutable sequences influence bacterial pathogenesis., Pathogens, Vol: 3, Pages: 164-184, ISSN: 2076-0817
Rapid adaptation to fluctuations in the host milieu contributes to the host persistence and virulence of bacterial pathogens. Adaptation is frequently mediated by hypermutable sequences in bacterial pathogens. Early bacterial genomic studies identified the multiplicity and virulence-associated functions of these hypermutable sequences. Thus, simple sequence repeat tracts (SSRs) and site-specific recombination were found to control capsular type, lipopolysaccharide structure, pilin diversity and the expression of outer membrane proteins. We review how the population diversity inherent in the SSR-mediated mechanism of localised hypermutation is being unlocked by the investigation of whole genome sequences of disease isolates, analysis of clinical samples and use of model systems. A contrast is presented between the problematical nature of analysing simple sequence repeats in next generation sequencing data and in simpler, pragmatic PCR-based approaches. Specific examples are presented of the potential relevance of this localized hypermutation to meningococcal pathogenesis. This leads us to speculate on the future prospects for unravelling how hypermutable mechanisms may contribute to the transmission, spread and persistence of bacterial pathogens.
Bidmos FA, 2013, The role of phase-variable expression of meningococcal surface proteins during carriage and disease
Neisseria meningitidis is the most common cause of bacterial meningitis, a disease that kills thousands of people yearly. Asymptomatic colonisation of the oropharynx (i. e. carriage) occurs in 10% – 30% of humans. Significant features of meningococcal genomes are simple sequence repeats (SSR), which have been shown to control gene expression in a reversible process known as phase variation (PV). This study investigated the consequence of “switching-OFF” of two haemoglobin-acquisition systems (hpuAB and hmbR) during disease and also explored potential associations between PV state of the immunodominant meningococcal antigen, PorA, and the adaptive immune response during carriage. Using an ex vivo human whole blood model, hmbR-OFF mutants of strain MC58 (hpuAB-negative) exhibited a pattern of growth similar to wild-type. Conversely, an inability to utilise transferrin (ΔtbpBA) significantly affected growth but not survival in blood. Five recombinant versions of these Hb receptors were prepared in this study and subsequently used as antigens for the generation of polyclonal and monoclonal antibodies in mice. The polyclonal antirHpuA, anti-rHpuB and anti-rHmbR antisera were reactive with homologous receptors in lysates of diverse meningococcal strains. Surface expression of HpuA and HmbR was detected by flow cytometry but all antisera were incapable of mediating killing of iron-restricted meningococci. An immunodetection assay employed in this study revealed the induction of variant-specific anti-PorA IgG antibodies following acquisition of carriage. These antibodies may have contributed to subsequent loss of carriage but a role for PV in immune escape in vivo was not established. This study posits that HmbR is less important than TbpBA and HpuAB during disease and that phase variable expression of surface receptors is irrelevant for immune evasion during carriage. Further studies are recommended to confirm the proposed importance of HpuAB over H
Oldfield NJ, Matar S, Bidmos FA, et al., 2013, Prevalence and Phase Variable Expression Status of Two Autotransporters, NalP and MspA, in Carriage and Disease Isolates of Neisseria meningitidis, PLOS ONE, Vol: 8, ISSN: 1932-6203
Bayliss CD, Bidmos FA, Anjum A, et al., 2012, Phase variable genes of Campylobacter jejuni exhibit high mutation rates and specific mutational patterns but mutability is not the major determinant of population structure during host colonization, NUCLEIC ACIDS RESEARCH, Vol: 40, Pages: 5876-5889, ISSN: 0305-1048
Ala'Aldeen DAA, Oldfield NJ, Bidmos FA, et al., 2011, Carriage of Meningococci by University Students, United Kingdom, EMERGING INFECTIOUS DISEASES, Vol: 17, Pages: 1761-1763, ISSN: 1080-6040
Bidmos FA, Neal KR, Oldfield NJ, et al., 2011, Persistence, Replacement, and Rapid Clonal Expansion of Meningococcal Carriage Isolates in a 2008 University Student Cohort, JOURNAL OF CLINICAL MICROBIOLOGY, Vol: 49, Pages: 506-512, ISSN: 0095-1137
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