Pathogenic Leptospira Species Acquire Factor H and Vitronectin via the Surface Protein LcpA

Upon infection, pathogenicLeptospiraspecies bind several complement regulators in order to overcome host innate immunity. We previously characterized a 20-kDa leptospiral surface protein which interacts with C4b binding protein (C4BP):leptospiralcomplement regulator-acquiringprotein A (LcpA). Here we show that LcpA also interacts with human factor H (FH), which remains functionally active once bound to the protein. Antibodies directed against short consensus repeat 20 (SCR20) inhibited binding of FH to LcpA by approximately 90%, thus confirming that this particular domain is involved in the interaction. We have also shown for the first time that leptospires bind human vitronectin and that the interaction is mediated by LcpA. Coincubation with heparin blocked LcpA-vitronectin interaction in a dose-dependent manner, strongly suggesting that binding may occur through the heparin binding domains of vitronectin. LcpA also bound to the terminal pathway component C9 and inhibited Zn2+-induced polymerization and membrane attack complex (MAC) formation. Competitive binding assays indicated that LcpA interacts with C4BP, FH, and vitronectin through distinct sites. Taken together, our findings indicate that LcpA may play a role in leptospiral immune evasion.

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Implication of Antigenic Conversion of Helicobacter pylori Lipopolysaccharides That Involve Interaction with Surfactant Protein D

Infection and Immunity ◽

10.1128/iai.00345-12 ◽

2012 ◽

Vol 80 (8) ◽

pp. 2956-2962 ◽

Cited By ~ 10

Author(s):

Shin-ichi Yokota ◽

Ken-ichi Amano ◽

Chiaki Nishitani ◽

Shigeru Ariki ◽

Yoshio Kuroki ◽

...

Keyword(s):

Helicobacter Pylori ◽

Biological Activities ◽

Surfactant Protein ◽

Binding Activity ◽

Surfactant Protein D ◽

Dependent Manner ◽

Antigenic Epitope ◽

Binding Assays ◽

Content Type ◽

Gastric Cancer Patients

ABSTRACTWe propose two antigenic types ofHelicobacter pylorilipopolysaccharides (LPS): highly antigenic epitope-carrying LPS (HA-LPS) and weakly antigenic epitope-carrying LPS (WA-LPS) based on human serum reactivity. Strains carrying WA-LPS are highly prevalent in isolates from gastric cancer patients. WA-LPS exhibits more potent biological activities compared to HA-LPS, namely, upregulation of Toll-like receptor 4 (TLR4) expression and induction of enhanced epithelial cell proliferation. The results of competitive binding assays using monosaccharides and methylglycosides, as well as binding assays using glycosidase-treated LPS, suggested that β-linkedN-acetyl-d-glucosamine and β-linkedd-galactose residues largely contributed to the highly antigenic epitope and the weakly antigenic epitope, respectively. WA-LPS exhibited greater binding activity to surfactant protein D (SP-D) in a Ca2+-dependent manner, and this interaction was inhibited by methyl-β-d-galactoside. The biological activities of WA-LPS were markedly enhanced by the addition of SP-D. Lines of evidence suggested that removal of β-N-acetyl-d-glucosamine residue, which comprises the highly antigenic epitope, results in exposure of the weakly antigenic epitope. The weakly antigenic epitope interacted preferentially with SP-D, and SP-D enhanced the biological activity of WA-LPS.

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PspK of Streptococcus pneumoniae Increases Adherence to Epithelial Cells and Enhances Nasopharyngeal Colonization

Infection and Immunity ◽

10.1128/iai.00755-12 ◽

2012 ◽

Vol 81 (1) ◽

pp. 173-181 ◽

Cited By ~ 50

Author(s):

L. E. Keller ◽

C. V. Jones ◽

J. A. Thornton ◽

M. E. Sanders ◽

E. Swiatlo ◽

...

Keyword(s):

Streptococcus Pneumoniae ◽

Epithelial Cells ◽

Immunoglobulin A ◽

Surface Protein ◽

Invasive Disease ◽

Factor H ◽

Host Cells ◽

Content Type ◽

Capsule Locus ◽

Complement Regulator

Streptococcus pneumoniae(the pneumococcus) colonizes the human nasopharynx and can cause invasive disease aided by the pneumococcal capsule. Group II nontypeableS. pneumoniae(NTSp) lacks a polysaccharide capsule, and a subgroup of NTSp carriage isolates has been found to have a novel gene, pneumococcal surface protein K (pspK), which replaces the capsule locus. A recent rise in the number of NTSp isolates colonizing the human nasopharynx has been observed, but the colonization factors of NTSp have not been well studied. PspK has been shown to play a role in mouse colonization. We therefore examined PspK-mediated immune evasion along with adherence to host cells and colonization. PspK bound human secretory immunoglobulin A (sIgA) but not the complement regulator factor H and did not decrease C3b deposition on the pneumococcal surface. PspK increased binding of pneumococci to epithelial cells and enhanced pneumococcal colonization independently of the genetic background. Understanding how NTSp colonizes and survives within the nasopharynx is important due to the increase in NTSp carriage. Our data suggest that PspK may aid in the persistence of NTSp within the nasopharynx but is not involved in invasion.

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Plasmodium vivaxMerozoite Surface Protein 1 Paralog as a Mediator of Parasite Adherence to Reticulocytes

Infection and Immunity ◽

10.1128/iai.00239-18 ◽

2018 ◽

Vol 86 (9) ◽

Cited By ~ 6

Author(s):

Jin-Hee Han ◽

Jee-Sun Cho ◽

Yang Cheng ◽

Fauzi Muh ◽

Won Gi Yoo ◽

...

Keyword(s):

Surface Protein ◽

Merozoite Surface Protein ◽

Binding Activity ◽

Binding Motif ◽

Dependent Manner ◽

Human Beings ◽

Content Type ◽

C Terminus ◽

Significant Difference

ABSTRACTPlasmodium vivaxparasites preferentially invade reticulocytes in human beings.P. vivaxmerozoite surface protein 1 (PvMSP1) and PvMSP1 paralog (PvMSP1P) may have important functions in reticulocyte adherence during invasion. These proteins share similar structures, including the presence of two epidermal growth factor (EGF)-like and glycosylphosphatidylinositol (GPI)-anchored domains at the C terminus. However, there have been no reports concerning the functional activity of PvMSP1P in reticulocyte adherence duringP. vivaxinvasion. In this study, the ability of PvMSP1P-19 to bind to reticulocytes and normocytes was analyzed. The reticulocyte binding activity of PvMSP1P-19 was 4.0-fold higher than its normocyte binding activity. The binding of PvMSP1P-19 to reticulocytes and normocytes was inhibited in a dose-dependent manner by antibodies from immunized rabbits and by antibodies from vivax parasite-infected patients. Consistently, antibodies against PvMSP1P inhibited parasite invasion during short-termin vitrocultivation. Similar to the case for PvDBPII binding activity, PvMSP1P-19 binding activity was reduced in chymotrypsin-treated reticulocytes. However, no significant difference between the binding of PvMSP1P-19 to Duffy-positive and Duffy-negative erythrocytes was found. The minimal binding motif of PvMSP1P-19 was characterized using synthetic peptides. The results showed that the residues at amino acid positions 1791 to 1808 may have an important function in mediating merozoite adherence to reticulocytes. The positively charged residues within the EGF-like domain were shown to constitute a key binding motif. This work presents strong evidence supporting the role of PvMSP1P in host target cell selection and invasion of Duffy-independent pathway inP. vivax. Moreover, PvMSP1P-19-specific antibodies may confer protection againstP. vivaxreinvasion.

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Corynebacterium diphtheriaeIron-Regulated Surface Protein HbpA Is Involved in the Utilization of the Hemoglobin-Haptoglobin Complex as an Iron Source

Journal of Bacteriology ◽

10.1128/jb.00676-17 ◽

2018 ◽

Vol 200 (7) ◽

Cited By ~ 1

Author(s):

Lindsey R. Lyman ◽

Eric D. Peng ◽

Michael P. Schmitt

Keyword(s):

Sequence Similarity ◽

Bacterial Pathogens ◽

Surface Protein ◽

Surface Proteins ◽

Cell Fractionation ◽

Dependent Manner ◽

Human Respiratory Tract ◽

Homologous Proteins ◽

Content Type ◽

Iron Source

ABSTRACTCorynebacterium diphtheriaeutilizes various heme-containing proteins, including hemoglobin (Hb) and the hemoglobin-haptoglobin complex (Hb-Hp), as iron sources during growth in iron-depleted environments. The ability to utilize Hb-Hp as an iron source requires the surface-anchored proteins HtaA and either ChtA or ChtC. The ability to bind hemin, Hb, and Hb-Hp by each of theseC. diphtheriaeproteins requires the previously characterized conserved region (CR) domain. In this study, we identified an Hb-Hp binding protein, HbpA (38.5 kDa), which is involved in the acquisition of hemin iron from Hb-Hp. HbpA was initially identified from total cell lysates as an iron-regulated protein that binds to both Hb and Hb-Hpin situ. HbpA does not contain a CR domain and has sequence similarity only to homologous proteins present in a limited number ofC. diphtheriaestrains. Transcription ofhbpAis regulated in an iron-dependent manner that is mediated by DtxR, a global iron-dependent regulator. Deletion ofhbpAfromC. diphtheriaeresults in a reduced ability to utilize Hb-Hp as an iron source but has little or no effect on the ability to use Hb or hemin as an iron source. Cell fractionation studies showed that HbpA is both secreted into the culture supernatant and associated with the membrane, where its exposure on the bacterial surface allows HbpA to bind Hb and Hb-Hp. The identification and analysis of HbpA enhance our understanding of iron uptake inC. diphtheriaeand indicate that the acquisition of hemin iron from Hb-Hp may involve a complex mechanism that requires multiple surface proteins.IMPORTANCEThe ability to utilize host iron sources, such as heme and heme-containing proteins, is essential for many bacterial pathogens to cause disease. In this study, we have identified a novel factor (HbpA) that is crucial for the use of hemin iron from the hemoglobin-haptoglobin complex (Hb-Hp). Hb-Hp is considered one of the primary sources of iron for certain bacterial pathogens. HbpA has no similarity to the previously identified Hb-Hp binding proteins, HtaA and ChtA/C, and is found only in a limited group ofC. diphtheriaestrains. Understanding the function of HbpA may significantly increase our knowledge of how this important human pathogen can acquire host iron that allows it to survive and cause disease in the human respiratory tract.

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The Yeast Candida albicans Binds Complement Regulators Factor H and FHL-1

Infection and Immunity ◽

10.1128/iai.70.9.5185-5192.2002 ◽

2002 ◽

Vol 70 (9) ◽

pp. 5185-5192 ◽

Cited By ~ 112

Author(s):

T. Meri ◽

A. Hartmann ◽

D. Lenk ◽

R. Eck ◽

R. Würzner ◽

...

Keyword(s):

Candida Albicans ◽

Complement Activation ◽

Fungal Infections ◽

Factor H ◽

Classical Pathway ◽

Binding Assays ◽

Pathogenic Yeast ◽

Mutant Proteins ◽

Binding Domains ◽

Complement Regulators

ABSTRACT The human facultative pathogenic yeast Candida albicans causes mucocutaneous infections and is the major cause of opportunistic fungal infections in immunocompromised patients. C. albicans activates both the alternative and classical pathway of the complement system. The aim of this study was to assay whether C. albicans binds human complement regulators in order to control complement activation at its surface. We observed binding of two central complement regulators, factor H and FHL-1, from normal human serum to C. albicans by adsorption assays, immunostaining, and fluorescence-activated cell sorter (FACS) analyses. Specificity of acquisition was further confirmed in direct binding assays with purified proteins. The surface-attached regulators maintained their complement regulatory activities and mediated factor I-dependent cleavage of C3b. Adsorption assays with recombinant deletion mutant proteins were used to identify binding domains. Two binding sites were localized. One binding domain common to both factor H and FHL-1 is located in the N-terminal short consensus repeat domains (SCRs) 6 and 7, and the other one located in C-terminal SCRs 19 and 20 is unique to factor H. These data indicate that by surface acquisition of host complement regulators, the human pathogenic yeast C. albicans is able to regulate alternative complement activation at its surface and to inactivate toxic complement activation products.

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ErpY-like lipoprotein of Leptospira outsmart host complement regulation by acquiring complement regulators, activating alternate pathway, and intervening membrane attack complex

10.1101/2021.05.27.446086 ◽

2021 ◽

Author(s):

Saswat Hota ◽

Md Saddam Hussain ◽

Manish Kumar

Keyword(s):

Serum Proteins ◽

Membrane Attack Complex ◽

Factor H ◽

Classical Pathway ◽

Complement Components ◽

Pathogenic Leptospira ◽

Bacterial Surface ◽

Alternate Complement Pathway ◽

Complement Regulators

The survival of pathogenic Leptospira in the host pivots on its proficiency to circumvent the immune response. These pathogens evade the complement system in serum by enticing and amassing the serum complement regulators onto their surface. ErpY-like lipoprotein, a surface-exposed protein of Leptospira spp., is conserved and exclusively present in the pathogenic spirochete. The recombinant form of this protein is comprehended to interact with multiple extracellular matrix (ECM) components and serum proteins like soluble complement regulators factor H (FH) and factor I (FI). Here, we document that the supplementation of recombinant ErpY-like protein (40 µg/mL) in the host (humans) serum augments the viability of E. coli and saprophytic L. biflexa by more than 2-fold. Pure complement regulators FH and FI, when bound to rErpY-like protein, preserve their respective cofactor and protease activity mandated to cleave the complement component C3b. The supplementation of rErpY-like protein (40 µg/mL) in serum ensued in ~90 % reduction of membrane attack complex (C5b-9/MAC) deposition through alternate complement pathway (AP) activation. However, rErpY-like protein could moderately reduce (~16%) MAC deposition in serum through the classical pathway (CP). In addition, the rErpY-like protein solely activated the AP, suggesting its role in the rapid consumption and depletion of the complement components. Blocking the pathogenic L. interrogans surface with anti-rErpY resulted in an increase in MAC formation on the bacterial surface, indicating a specific role of the ErpY-like lipoprotein in complement-mediated immune evasion. This study underscores the role of the ErpY-like lipoprotein of Leptospira in complement evasion.

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Design and development of TT30, a novel C3d-targeted C3/C5 convertase inhibitor for treatment of human complement alternative pathway–mediated diseases

Blood ◽

10.1182/blood-2011-06-359646 ◽

2011 ◽

Vol 118 (17) ◽

pp. 4705-4713 ◽

Cited By ~ 83

Author(s):

Masha Fridkis-Hareli ◽

Michael Storek ◽

Istvan Mazsaroff ◽

Antonio M. Risitano ◽

Ante S. Lundberg ◽

...

Keyword(s):

Cell Surface ◽

Ex Vivo ◽

Alternative Pathway ◽

Membrane Attack Complex ◽

Factor H ◽

Dependent Manner ◽

Human Complement ◽

Complement Alternative Pathway ◽

Inflammatory Conditions ◽

Wide Range

Abstract To selectively modulate human complement alternative pathway (CAP) activity implicated in a wide range of acute and chronic inflammatory conditions and to provide local cell surface and tissue-based inhibition of complement-induced damage, we developed TT30, a novel therapeutic fusion protein linking the human complement receptor type 2 (CR2/CD21) C3 fragment (C3frag = iC3b, C3dg, C3d)-binding domain with the CAP inhibitory domain of human factor H (fH). TT30 efficiently blocks ex vivo CAP-dependent C3frag accumulation on activated surfaces, membrane attack complex (MAC) formation and hemolysis of RBCs in a CR2-dependent manner, and with a ∼ 150-fold potency gain over fH, without interference of C3 activation or MAC formation through the classic and lectin pathways. TT30 protects RBCs from hemolysis and remains bound and detectable for at least 24 hours. TT30 selectively inhibits CAP in cynomolgus monkeys and is bioavailable after subcutaneous injection. Using a unique combination of targeting and effector domains, TT30 controls cell surface CAP activation and has substantial potential utility for the treatment of human CAP-mediated diseases.

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Role of Gonococcal Neisserial Surface Protein A (NspA) in Serum Resistance and Comparison of Its Factor H Binding Properties with Those of Its Meningococcal Counterpart

Infection and Immunity ◽

10.1128/iai.00658-18 ◽

2018 ◽

Vol 87 (2) ◽

Cited By ~ 5

Author(s):

Lisa A. Lewis ◽

Peter A. Rice ◽

Sanjay Ram

Keyword(s):

Protein A ◽

Phase Variation ◽

Surface Protein ◽

Multidrug Resistant ◽

Factor H ◽

Serum Resistance ◽

Content Type ◽

Global Threat ◽

Loop 2 ◽

Human Specific

ABSTRACTNeisseria gonorrhoeae, the causative agent of gonorrhea, has evolved several mechanisms to subvert complement, including binding of the complement inhibitor factor H (FH). We previously reported FH binding toN. gonorrhoeaeindependently of lipooligosaccharide (LOS) sialylation. Here we report that factor H-like protein 1 (FHL-1), which contains FH domains 1 through 7 and possesses complement-inhibitory activity, also binds toN. gonorrhoeae. The ligand for both FH and FHL-1 was identified as neisserial surface protein A (NspA), which has previously been identified as a ligand for these molecules onNeisseria meningitidis. As withN. meningitidisNspA (Nm-NspA),N. gonorrhoeaeNspA (Ng-NspA) bound FH/FHL-1 through FH domains 6 and 7. Binding of FH/FHL-1 to NspA was human specific; the histidine (H) at position 337 of domain 6 contributed to human-specific FH binding to bothNg- andNm-NspA. FH/FHL-1 boundNm-NspA better thanNg-NspA; introducing Q at position 73 (loop 2, present inNg-NspA) or replacing V and D at positions 112 and 113 inNm-NspA loop 3 with A and H (Ng-NspA), respectively, reduced FH/FHL-1 binding. The converseNg-NspA toNm-NspA mutations increased FH/FHL-1 binding. Binding of FH/FHL-1 through domains 6 and 7 toN. gonorrhoeaeincreased with truncation of the heptose I (HepI) chain of LOS and decreased with LOS sialylation. Loss of NspA significantly decreased serum resistance ofN. gonorrhoeaewith either wild-type or truncated LOS. This report highlights the role for NspA in enablingN. gonorrhoeaeto subvert complement despite LOS phase variation. Knowledge of FH-NspA interactions will inform the design of vaccines and immunotherapies against the global threat of multidrug-resistant gonorrhea.

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Genetic Distribution of Noncapsular Meningococcal Group B Vaccine Antigens in Neisseria lactamica

Clinical and Vaccine Immunology ◽

10.1128/cvi.00090-13 ◽

2013 ◽

Vol 20 (9) ◽

pp. 1360-1369 ◽

Cited By ~ 12

Author(s):

Jay Lucidarme ◽

Stefanie Gilchrist ◽

Lynne S. Newbold ◽

Stephen J. Gray ◽

Edward B. Kaczmarski ◽

...

Keyword(s):

Outer Membrane ◽

Membrane Vesicle ◽

Geographic Region ◽

Factor H ◽

Heparin Binding ◽

Content Type ◽

Vaccine Responses ◽

Neisseria Lactamica ◽

Genetic Distribution ◽

Group B

ABSTRACTThe poor immunogenicity of the meningococcal serogroup B (MenB) capsule has led to the development of vaccines targeting subcapsular antigens, in particular the immunodominant and diverse outer membrane porin, PorA. These vaccines are largely strain specific; however, they offer limited protection against the diverse MenB-associated diseases observed in many industrialized nations. To broaden the scope of its protection, the multicomponent vaccine (4CMenB) incorporates a PorA-containing outer membrane vesicle (OMV) alongside relatively conserved recombinant protein components, including factor H-binding protein (fHbp),Neisseriaadhesin A (NadA), and neisserial heparin-binding antigen (NHBA). The expression of PorA is unique to meningococci (Neisseria meningitidis); however, many subcapsular antigens are shared with nonpathogenic members of the genusNeisseriathat also inhabit the nasopharynx. These organisms may elicit cross-protective immunity against meningococci and/or occupy a niche that might otherwise accommodate pathogens. The potential for 4CMenB responses to impact such species (and vice versa) was investigated by determining the genetic distribution of the primary 4CMenB antigens among diverse members of the common childhood commensal,Neisseria lactamica. All the isolates possessednhbabut were devoid offhbpandnadA. Thenhbaalleles were mainly distinct from but closely related to those observed among a representative panel of invasive MenB isolates from the same broad geographic region. We made similar findings for the immunogenic typing antigen, FetA, which constitutes a major part of the 4CMenB OMV. Thus, 4CMenB vaccine responses may impact or be impacted by nasopharyngeal carriage of commensal neisseriae. This highlights an area for further research and surveillance should the vaccine be routinely implemented.

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Streptococcus pneumoniaePspC Subgroup Prevalence in Invasive Disease and Differences in Contribution to Complement Evasion

Infection and Immunity ◽

10.1128/iai.00010-18 ◽

2018 ◽

Vol 86 (4) ◽

Cited By ~ 3

Author(s):

Erika van der Maten ◽

Bryan van den Broek ◽

Marien I. de Jonge ◽

Kim J. W. Rensen ◽

Marc J. Eleveld ◽

...

Keyword(s):

Surface Protein ◽

Invasive Disease ◽

Factor H ◽

Complement Factor ◽

Content Type ◽

Complement Resistance ◽

Functional Differences ◽

Subgroup Ii ◽

Virulence Protein ◽

Complement Deposition

ABSTRACTThe pneumococcal capsular serotype is an important determinant of complement resistance and invasive disease potential, but other virulence factors have also been found to contribute. Pneumococcal surface protein C (PspC), a highly variable virulence protein that binds complement factor H to evade C3 opsonization, is divided into two subgroups: choline-bound subgroup I and LPxTG-anchored subgroup II. The prevalence of different PspC subgroups in invasive pneumococcal disease (IPD) and functional differences in complement evasion are unknown. The prevalence of PspC subgroups in IPD isolates was determined in a collection of 349 sequenced strains ofStreptococcus pneumoniaeisolated from adult patients.pspCdeletion mutants and isogenicpspCswitch mutants were constructed to study differences in factor H binding and complement evasion in relation to capsule thickness. Subgroup IpspCwas far more prevalent in IPD isolates than subgroup IIpspC. The presence of capsule was associated with a greater ability of bound factor H to reduce complement opsonization. Pneumococcal subgroup I PspC bound significantly more factor H and showed more effective complement evasion than subgroup II PspC in isogenic encapsulated pneumococci. We conclude that variation in the PspC subgroups, independent of capsule serotypes, affects pneumococcal factor H binding and its ability to evade complement deposition.

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