scholarly journals Characterization of Diverse Subvariants of the Meningococcal Factor H (fH) Binding Protein for Their Ability To Bind fH, To Mediate Serum Resistance, and To Induce Bactericidal Antibodies

2010 ◽  
Vol 79 (2) ◽  
pp. 970-981 ◽  
Author(s):  
Kate L. Seib ◽  
Brunella Brunelli ◽  
Barbara Brogioni ◽  
Emmanuelle Palumbo ◽  
Stefania Bambini ◽  
...  
Keyword(s):  
Binding Protein ◽  
Genetically Engineered ◽  
Factor H ◽  
Serum Resistance ◽  
Dependent Manner ◽  
Bacterial Surface ◽  
Bactericidal Antibody ◽  
Human Sera ◽  
The Stability

ABSTRACTNeisseria meningitidisis 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 MC58ΔfHbpstrain 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 diverse 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.

scholarly journals Molecular and Functional Characterization of a ToxR-Regulated Lipoprotein from a Clinical Isolate of Aeromonas hydrophila

2006 ◽  
Vol 74 (7) ◽  
pp. 3742-3755 ◽  
Author(s):  
Lakshmi Pillai ◽  
Jian Sha ◽  
Tatiana E. Erova ◽  
Amin A. Fadl ◽  
Bijay K. Khajanchi ◽  
...  
Keyword(s):  
Virulence Factor ◽  
Aeromonas Hydrophila ◽  
Functional Characterization ◽  
Affinity Column ◽  
Serum Resistance ◽  
Classical Pathway ◽  
Dependent Manner ◽  
T7 Promoter

ABSTRACT Human diseases caused by species of Aeromonas have been classified into two major groups: septicemia and gastroenteritis. In this study, we reported the molecular and functional characterization of a new virulence factor, ToxR-regulated lipoprotein, or TagA, from a diarrheal isolate, SSU, of Aeromonas hydrophila. The tagA gene of A. hydrophila exhibited 60% identity with that of a recently identified stcE gene from Escherichia coli O157:H7, which encoded a protein (StcE) that provided serum resistance to the bacterium and prevented erythrocyte lysis by controlling classical pathway of complement activation by cleaving the complement C1-esterase inhibitor (C1-INH). We purified A. hydrophila TagA as a histidine-tagged fusion protein (rTagA) from E. coli DE3 strain using a T7 promoter-based pET30 expression vector and nickel affinity column chromatography. rTagA cleaved C1-INH in a time-dependent manner. The tagA isogenic mutant of A. hydrophila, unlike its corresponding wild-type (WT) or the complemented strain, was unable to cleave C1-INH, which is required to potentiate the C1-INH-mediated lysis of host and bacterial cells. We indeed demonstrated colocalization of C1-INH and TagA on the bacterial surface by confocal fluorescence microscopy, which ultimately resulted in increased serum resistance of the WT bacterium. Likewise, we delineated the role of TagA in contributing to the enhanced ability of C1-INH to inhibit the classical complement-mediated lysis of erythrocytes. Importantly, we provided evidence that the tagA mutant was significantly less virulent in a mouse model of infection (60%) than the WT bacterium at two 50% lethal doses, which resulted in 100% mortality within 48 h. Taken together, our data provided new information on the role of TagA as a virulence factor in bacterial pathogenesis. This is the first report of TagA characterization from any species of Aeromonas.

scholarly journals Impaired Immunogenicity of a Meningococcal Factor H-Binding Protein Vaccine Engineered To Eliminate Factor H Binding

2010 ◽  
Vol 17 (7) ◽  
pp. 1074-1078 ◽  
Author(s):  
Peter T. Beernink ◽  
Jutamas Shaughnessy ◽  
Sanjay Ram ◽  
Dan M. Granoff
Keyword(s):  
Binding Protein ◽  
Factor H ◽  
Vaccine Antigen ◽  
Mouse Strains ◽  
Enzyme Linked Immunosorbent Assay ◽  
Complement Factor ◽  
Protein Vaccine ◽  
Wild Type ◽  
Bacterial Surface ◽  
Cast Doubt

ABSTRACT Meningococcal factor H-binding protein (fHbp) is a promising antigen that is part of two vaccines in clinical development. The protein specifically binds human complement factor H (fH), which downregulates complement activation on the bacterial surface and enables the organism to evade host defenses. In humans, the vaccine antigen forms a complex with fH, which may affect anti-fHbp antibody repertoire and decrease serum bactericidal activity by covering important fHbp epitopes. In a recent study, fHbp residues in contact with fH were identified from a crystal structure. Two fHbp glutamate residues that mediated ion-pair interactions with fH were replaced with alanine, and the resulting E218A/E239A mutant no longer bound the fH fragment. In the present study, we generated the E218A/E239A mutant recombinant protein and confirmed the lack of fH binding. By enzyme-linked immunosorbent assay (ELISA), the mutant fHbp showed similar respective concentration-dependent inhibition of binding of four bactericidal anti-fHbp monoclonal antibodies (MAbs) to fHbp, compared with inhibition by the soluble wild-type protein. In two mouse strains, the mutant fHbp elicited up to 4-fold-lower IgG anti-fHbp antibody titers and up to 20-fold-lower serum bactericidal titers than those elicited by the wild-type fHbp vaccine. Thus, although introduction of the two alanine substitutions to eliminate fH binding did not appear to destabilize the molecule globally, the mutations resulted in decreased immunogenicity in mouse models in which neither the mutant nor the wild-type control vaccine bound fH. These results cast doubt on the vaccine potential in humans of this mutant fHbp.

scholarly journals Identification and Functional Characterization of Complement Regulator-Acquiring Surface Protein 1 of the Lyme Disease Spirochetes Borrelia afzelii and Borrelia garinii

2005 ◽  
Vol 73 (4) ◽  
pp. 2351-2359 ◽  
Author(s):  
Reinhard Wallich ◽  
Joseph Pattathu ◽  
Veronique Kitiratschky ◽  
Christiane Brenner ◽  
Peter F. Zipfel ◽  
...  
Keyword(s):  
Lyme Disease ◽  
Binding Site ◽  
Binding Protein ◽  
Functional Characterization ◽  
Surface Protein ◽  
Factor H ◽  
Borrelia Garinii ◽  
Borrelia Afzelii ◽  
Complement Regulator

ABSTRACT Complement regulator-acquiring surface protein 1 (CRASP-1) is the dominant factor-H-like protein 1 (FHL-1)- and factor-H-binding protein of Borrelia burgdorferi and is suggested to contribute to persistence of the pathogen. The prototype CRASP-1 of B. burgdorferi sensu stricto (CRASP-1Bb) has been formerly characterized. As shown recently, serum-resistant Borrelia afzelii strains express a unique FHL-1 and factor H-binding protein, designated CRASP-1Ba. Here, we describe for the first time the isolation and functional characterization of the gene encoding the full-length CRASP-1Ba of 28 kDa, which, upon processing, is predicted to be 26.4 kDa. CPASP-1Ba of B. afzelii spirochetes is associated with a genetic locus encoding the orthologous gbb54 gene family that maps to the linear plasmid of approximately 54 kb. Ligand affinity blotting techniques demonstrate that both native and recombinant CRASP-1Ba molecules strongly bind to FHL-1 and much more weakly to factor H. The FHL-1 and factor-H-binding site in CRASP-1Ba is shown to be localized to a 12-amino-acid residue domain at the C terminus of the protein. For comparison, the corresponding cspA-like gene(s) of a serum-sensitive Borrelia garinii strain has also been cloned and characterized. Most notably, two CRASP-1-related B. garinii proteins were identified; however, both molecules bind only weakly to FHL-1 and not at all to factor H. The present identification of the binding site of CRASP-1Ba represents an important step forward in our understanding of the pathogenesis of Lyme disease and may be helpful to design therapeutic regimens to interfere with complement evasion strategies of human pathogenic Borrelia strains.

scholarly journals C4b Binding Protein Acts as an Innate Immune Effector Against Influenza A Virus

2021 ◽  
Vol 11 ◽  
Author(s):  
Praveen M. Varghese ◽  
Valarmathy Murugaiah ◽  
Nazar Beirag ◽  
Nigel Temperton ◽  
Haseeb A. Khan ◽  
...  
Keyword(s):  
Influenza A Virus ◽  
Influenza A ◽  
Matrix Protein ◽  
Binding Protein ◽  
Fluid Phase ◽  
Factor H ◽  
Epithelial Cell Line ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Independent Manner

C4b Binding Protein (C4BP) is a major fluid phase inhibitor of the classical and lectin pathways of the complement system. Complement inhibition is achieved by binding to and restricting the role of activated complement component C4b. C4BP functions as a co-factor for factor I in proteolytic inactivation of both soluble and cell surface-bound C4b, thus restricting the formation of the C3-convertase, C4b2a. C4BP also accelerates the natural decay/dissociation of the C3 convertase. This makes C4BP a prime target for exploitation by pathogens to escape complement attack, as seen in Streptococcus pyogenes or Flavivirus. Here, we examined whether C4BP can act on its own in a complement independent manner, against pathogens. C4BP bound H1N1 and H3N2 subtypes of Influenza A Virus (IAV) most likely via multiple sites in Complement Control Protein (CCP) 1-2, 4-5, and 7-8 domains of its α-chain. In addition, C4BP CCP1-2 bound H3N2 better than H1N1. C4BP bound three IAV envelope proteins: Haemagglutinin (~70 kDa), Neuraminidase (~55 kDa), and Matrix protein 1 (~25kDa). C4BP suppressed H1N1 subtype infection into the lung epithelial cell line, A549, while it promoted infection by H3N2 subtype. C4BP restricted viral entry for H1N1 but had the opposite effect on H3N2, as evident from experiments using pseudo-typed viral particles. C4BP downregulated mRNA levels of pro-inflammatory IFN-α, IL-12, and NFκB in the case of H1N1, while it promoted a pro-inflammatory immune response by upregulating IFN- α, TNF-α, RANTES, and IL-6 in the case of H3N2. We conclude that C4BP differentially modulates the efficacy of IAV entry, and hence, replication in a target cell in a strain-dependent manner, and acts as an entry inhibitor for H1N1. Thus, CCP containing complement proteins such as factor H and C4BP may have additional defense roles against IAV that do not rely on the regulation of complement activation.

scholarly journals Binding of Complement Factor H to Loop 5 of Porin Protein 1A: A Molecular Mechanism of Serum Resistance of Nonsialylated Neisseria gonorrhoeae

1998 ◽  
Vol 188 (4) ◽  
pp. 671-680 ◽  
Author(s):  
Sanjay Ram ◽  
Daniel P. McQuillen ◽  
Sunita Gulati ◽  
Christopher Elkins ◽  
Michael K. Pangburn ◽  
...  
Keyword(s):  
Neisseria Gonorrhoeae ◽  
Binding Site ◽  
Molecular Basis ◽  
Factor H ◽  
Serum Resistance ◽  
Complement Factor ◽  
Bacterial Surface ◽  
Exposed Region ◽  
Porin Protein ◽  
Serum Bactericidal Assay

Neisseria gonorrhoeae isolated from patients with disseminated infection are often of the porin (Por1A) serotype and resist killing by nonimmune normal human serum. The molecular basis of this resistance (termed stable serum resistance) in these strains has not been fully defined but is not related to sialylation of lipooligosaccharide. Here we demonstrate that Por1A bearing gonococcal strains bind more factor H, a critical downregulator of the alternative complement pathway, than their Por1B counterparts. This results in a sevenfold reduction in C3b, which is >75% converted to iC3b. Factor H binding to isogenic gonococcal strains that differed only in their porin serotype, confirmed that Por1A was the acceptor molecule for factor H. We identified a surface exposed region on the Por1A molecule that served as the binding site for factor H. We used gonococcal strains with hybrid Por1A/B molecules that differed in their surface exposed domains to localize the factor H binding site to loop 5 of Por1A. This was confirmed by inhibition of factor H binding using synthetic peptides corresponding to the putative exposed regions of the porin loops. The addition of Por1A loop 5 peptide in a serum bactericidal assay, which inhibited binding of factor H to the bacterial surface, permitted 50% killing of an otherwise completely serum resistant gonococcal strain. Collectively, these data provide a molecular basis to explain serum resistance of Por1A strains of N. gonorrhoeae.

scholarly journals Characterization of Neisseria meningitidis Isolates That Do Not Express the Virulence Factor and Vaccine Antigen Factor H Binding Protein

2011 ◽  
Vol 18 (6) ◽  
pp. 1002-1014 ◽  
Author(s):  
Jay Lucidarme ◽  
Lionel Tan ◽  
Rachel M. Exley ◽  
Jamie Findlow ◽  
Ray Borrow ◽  
...  
Keyword(s):  
Neisseria Meningitidis ◽  
Binding Protein ◽  
Factor H ◽  
Negative Regulator ◽  
Vaccine Antigen ◽  
Natural Immunity ◽  
Content Type ◽  
Reading Frame ◽  
Flanking Sequences

ABSTRACTNeisseria meningitidisremains a leading cause of bacterial sepsis and meningitis. Complement is a key component of natural immunity against this important human pathogen, which has evolved multiple mechanisms to evade complement-mediated lysis. One approach adopted by the meningococcus is to recruit a human negative regulator of the complement system, factor H (fH), to its surface via a lipoprotein, factor H binding protein (fHbp). Additionally, fHbp is a key antigen in vaccines currently being evaluated in clinical trials. Here we characterize strains ofN. meningitidisfrom several distinct clonal complexes which do not express fHbp; all strains were recovered from patients with disseminated meningococcal disease. We demonstrate that these strains have either a frameshift mutation in thefHbpopen reading frame or have entirely lostfHbpand some flanking sequences. No fH binding was detected to other ligands among thefHbp-negative strains. The implications of these findings for meningococcal pathogenesis and prevention are discussed.

scholarly journals Identification and Characterization of a Linear-Plasmid-Encoded Factor H-Binding Protein (FhbA) of the Relapsing Fever Spirochete Borrelia hermsii

2004 ◽  
Vol 186 (9) ◽  
pp. 2612-2618 ◽  
Author(s):  
Kelley M. Hovis ◽  
John V. McDowell ◽  
LaToya Griffin ◽  
Richard T. Marconi
Keyword(s):  
Molecular Mechanisms ◽  
Binding Protein ◽  
Genetic Locus ◽  
Factor H ◽  
Linear Plasmid ◽  
Relapsing Fever ◽  
Gene Encoding ◽  
Borrelia Hermsii ◽  
Identification And Characterization

ABSTRACT In North America, tick-borne relapsing fever (TBRF) is caused by the spirochete species Borrelia hermsii, Borrelia parkeri, and Borrelia turicatae. We previously demonstrated that some isolates of B. hermsii and B. parkeri are capable of binding factor H and that cell-bound factor H can participate in the factor I-mediated cleavage of C3b. Isolates that bound factor H expressed a factor H-binding protein (FHBP) that we estimated to be approximately 19 to 20 kDa in size and thus, pending further characterization, temporarily designated FHBP19. Until this report, none of the FHBPs of the TBRF spirochetes had been characterized. Here we have recovered the gene encoding the FHBP of B. hermsii YOR from a lambda ZAP II library and determined its sequence. The gene encodes a full-length protein of 22.7 kDa, which after processing is predicted to be 20.5 kDa. This protein, which we redesignate factor H-binding protein A (FhbA), is unique to B. hermsii. Two-dimensional pulsed-field gel electrophoresis and hybridization analyses revealed that the B. hermsii gene encoding FhbA is a single genetic locus that maps to a linear plasmid of approximately 220 kb. The general properties of FhbA were also assessed. The protein was found to be surface exposed and lipidated. Analysis of the antibody response to FhbA in infected mice revealed that it is antigenic during infection, indicating expression during infection. The identification and characterization of FhbA provides further insight into the molecular mechanisms of pathogenesis of the relapsing fever spirochetes.

scholarly journals Molecular characterization of two sub-family specific monoclonal antibodies to meningococcal Factor H binding protein

Heliyon ◽  
2018 ◽  
Vol 4 (4) ◽  
pp. e00591 ◽  
Author(s):  
C. Lo Passo ◽  
L. Zippilli ◽  
A. Angiolillo ◽  
I. Costa ◽  
I. Pernice ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Molecular Characterization ◽  
Binding Protein ◽  
Factor H

scholarly journals Design of Meningococcal Factor H Binding Protein Mutant Vaccines That Do Not Bind Human Complement Factor H

2012 ◽  
Vol 80 (8) ◽  
pp. 2667-2677 ◽  
Author(s):  
Rolando Pajon ◽  
Peter T. Beernink ◽  
Dan M. Granoff
Keyword(s):  
Amino Acid ◽  
Binding Protein ◽  
Sequence Similarity ◽  
Factor H ◽  
Complement Factor ◽  
Amino Acid Residues ◽  
Bactericidal Antibody ◽  
Group 2 ◽  
Complement Regulator ◽  
Species Specific

ABSTRACTMeningococcal factor H binding protein (fHbp) is a human species-specific ligand for the complement regulator, factor H (fH). In recent studies, fHbp vaccines in which arginine at position 41 was replaced by serine (R41S) had impaired fH binding. The mutant vaccines elicited bactericidal responses in human fH transgenic mice superior to those elicited by control fHbp vaccines that bound human fH. Based on sequence similarity, fHbp has been classified into three variant groups. Here we report that although R41 is present in fHbp from variant groups 1 and 2, the R41S substitution eliminated fH binding only in variant group 1 proteins. To identify mutants in variant group 2 with impaired fH binding, we generated fHbp structural models and predicted 63 residues influencing fH binding. From these, we created 11 mutants with one or two amino acid substitutions in a variant group 2 protein and identified six that decreased fH binding. Three of these six mutants retained conformational epitopes recognized by all six anti-fHbp monoclonal antibodies (MAbs) tested and elicited serum complement-mediated bactericidal antibody titers in wild-type mice that were not significantly different from those obtained with the control vaccine. Thus, fHbp amino acid residues that affect human fH binding differ across variant groups. This result suggests that fHbp sequence variation induced by immune selection also affects fH binding motifs via coevolution. The three new fHbp mutants from variant group 2, which do not bind human fH, retained important epitopes for eliciting bactericidal antibodies and may be promising vaccine candidates.

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