Receptor analogs and monoclonal antibodies that inhibit adherence of Bordetella pertussis to human ciliated respiratory epithelial cells

Lectin domains in the toxin of Bordetella pertussis: selectin mimicry linked to microbial pathogenesis

The pathogenesis of many infectious diseases is critically determined by prokaryotic lectins which enable differential recognition and activation of targeted eukaryotic cells. Some bacterial adhesins mimic and co-opt eukaryotic cell-cell adhesion motifs. This is illustrated by the toxin of Bordetella pertussis. Pertussis toxin mediates intoxication of eukaryotic cells by elevation of cAMP and it serves as an adhesin binding the bacteria to ciliated cells and respiratory macrophages. These activities are mediated by the lectin-like properties of the binding oligomer of the toxin. A comparison of pertussis toxin and the selectins involved in leukocyte trafficking indicates that these prokaryotic and eukaryotic C-type lectins share some element of primary sequence similarity, three dimensional structure, and biological activities. Such mimicry suggests a link between eukaryotic cell-cell adhesion motifs and microbial pathogenesis.

Sulfated glycoconjugate receptors for the Bordetella pertussis adhesin filamentous hemagglutinin (FHA) and mapping of the heparin-binding domain on FHA

Filamentous hemagglutinin (FHA) is a major adhesin present on the surface of the gram-negative respiratory pathogen Bordetella pertussis. A number of binding mechanisms have been described for the interaction of FHA with eukaryotic cells. We have focused on its function as a sulfated polysaccharide-binding protein and on identifying potential receptors for FHA on the epithelial cell surface. Using a thin-layer overlay technique, we found that FHA binds specifically to sulfated glycolipids but not to gangliosides or other neutral glycolipids. These results suggest that epithelial cell surface sulfated glycolipids function as receptors for FHA. Further studies demonstrated that a Chinese hamster ovary (CHO) cell strain deficient in glycosaminoglycan expression exhibits greatly diminished attachment to FHA. By FHA-Affi-Gel chromatography, a putative receptor for FHA that has characteristics consistent with a heparan sulfate proteoglycan was isolated from epithelial cell extracts. In addition, by using recombinant FHA fusion proteins, a specific glycosaminoglycan-binding domain located near the N terminus of the FHA molecule was identified. Our results indicate that the B. pertussis adhesin FHA may utilize sulfated glycolipids and proteoglycans commonly found on the surface of human cells and tissues to initiate infection.

Bordetella pertussis filamentous hemagglutinin interacts with a leukocyte signal transduction complex and stimulates bacterial adherence to monocyte CR3 (CD11b/CD18)

Bordetella pertussis, the causative agent of whooping cough, adheres to human monocytes/macrophages by means of a bacterial surface-associated protein, filamentous hemagglutinin (FHA) and the leukocyte integrin, complement receptor 3 (CR3, alpha M beta 2, CD11b/CD18). We show that an FHA Arg-Gly-Asp site induces enhanced B. pertussis binding to monocytes, and that this enhancement is blocked by antibodies directed against CR3. Enhancement requires a monocyte signal transduction complex, composed of leukocyte response integrin (alpha? beta 3) and integrin-associated protein (CD47). This complex is known to upregulate CR3 binding activity. Thus, a bacterial pathogen enhances its own attachment to host cells by coopting a host cell signaling pathway.

Glycolipid receptors for attachment of Mycoplasma hyopneumoniae to porcine respiratory ciliated cells

Glycolipid receptors for Mycoplasma hyopneumoniae attachment were analyzed by using a thin-layer chromatography (TLC) overlay assay. M. hyopneumoniae bound specifically to sulfatide, globoside, and monosialoganglioside GM3. No binding to sphingomyelin, cerebroside, lactosyl ceramide, ceramide trihexoside, monosialogangliosides GM1 and GM2, disialogangliosides (GD1a, GD1b, and GD3), trisialoganglioside (GT1b), cholesterol, cholesterol sulfate, palmitic acid, tripalmitin, or cholesteryl palmitate was detected. Total lipids extracted from cilia of the swine respiratory epithelium, the natural targets of M. hyopneumoniae infection, were also separated on TLC plates and overlaid with mycoplasmas. M. hyopneumoniae bound specifically to three ciliary glycolipids identified as La, Lb, and Lc. Binding to Lc was stronger than to La and Lb. All three lipids were believed to be sulfated glycolipids, as determined by laminin binding and staining with azure A. Lc was identified as a putative sulfatide because it has a mobility similar to that of authentic sulfatide and comigrated with sulfatide on TLC plates. Laminin bound to La, Lb, and Lc and produced dose-dependent inhibition of adherence of the mycoplasma to the three ciliary receptors. Binding of the mycoplasma to sulfatide, La, Lb, and Lc was partially inhibited by dextran sulfate, heparin, fucoidan, mucin, and chondroitin sulfate B. These substances blocked the adherence of M. hyopneumoniae to cilia and ciliated cells as shown in a previous study (Q. Zhang, T. F. Young, and R. F. Ross, Infect. Immun. 62:1616-1622, 1994). These results indicate that La, Lb, and Lc are the major native receptors for M. hyopneumoniae adherence to ciliated cells.

Surface-associated filamentous hemagglutinin induces autoagglutination of Bordetella pertussis

Filamentous hemagglutinin (FHA) is a major adhesin produced by Bordetella pertussis, the etiologic agent of whooping cough. FHA has been shown to be surface associated but is also secreted by virulent bacteria. Microscopic observations of lungs of mice infected with B. pertussis showed that the bacteria grow as clusters within the alveolar lumen. When B. pertussis was cultivated in vitro with chemically defined medium, bacteria grew as aggregates, mimicking growth observed in vivo. This aggregation was abolished by the addition of cyclodextrin (CDX) to the growth medium and depended on the production of FHA, because a mutant lacking the FHA structural gene failed to form aggregates in a CDX-free medium. Western blot (immunoblot) analyses revealed that, in the absence of CDX, FHA was attached to the bacterial surface and was not efficiently released into the growth medium. Hydrophobic chromatography of FHA showed that CDX drastically reduced the hydrophobicity of FHA, suggesting a direct binding of CDX to FHA, which was further supported by the partial protection of FHA from trypsin digestion in the presence of CDX. In addition, free FHA can interact in a CDX-inhibitable manner with solid phase-immobilized FHA. It can therefore be postulated that the B. pertussis aggregates are most likely due to direct FHA-FHA interaction.

The HMW1 adhesin of nontypeable Haemophilus influenzae recognizes sialylated glycoprotein receptors on cultured human epithelial cells

Disease due to nontypeable Haemophilus influenzae begins with colonization of the upper respiratory tract mucosa. We recently reported that two surface-exposed high-molecular-weight proteins (HMW1 and HMW2) expressed by a prototypic strain of nontypeable H. influenzae mediate attachment to cultured epithelial cells. In the present study, we examined the nature of the epithelial cell receptor with which HMW1 interacts. Both proteinase K pretreatment and periodate oxidation of epithelial monolayers resulted in a marked decrease in HMW1-mediated binding, suggesting interaction with a glycoprotein structure. Treatment with peptide-N-glycosidase F produced a similar decrease in attachment and thereby provided further evidence for this conclusion. Desialylation of the epithelial cell surface also reduced binding, implying the presence of sialic acid in the receptor structure. Furthermore, lectins specific for terminal alpha 2-3-linked sialic acid were capable of inhibiting HMW1-mediated attachment. In summary, our results indicate that the HMW1 adhesin interacts with a glycoprotein receptor containing N-linked oligosaccharide chains with sialic acid in an alpha 2-3 configuration.

Circulating fibronectin and fibronectin receptor in children with pertussis

AIM

To determine concentrations of fibronectin and fibronectin receptor in children with pertussis.

METHODS

Concentrations of circulating fibronectin and serum fibronectin receptor were detected in eight children affected by pertussis, eight children with acute upper or lower respiratory tract infections, and in 14 healthy control children. The single radial immunodiffusion technique and a solid phase enzyme immunoassay were used to detect circulating serum concentrations of fibronectin and fibronectin receptor.

RESULTS

On admission, a significant decrease in fibronectin was detected in children with pertussis (p = 0.0006). Significant and decreased concentrations of fibronectin were also observed in children with upper or lower respiratory tract infections (p = 0.0002). On the other hand, serum fibronectin receptor concentrations were significantly increased in patients with pertussis, whereas patients with upper or lower respiratory tract infections had normal circulating fibronectin receptor concentrations.

CONCLUSIONS

Fibronectin deficiency in children with pertussis may be related to diffusion and deposition of this protein in bronchial and alveolar spaces to limit infection, while increased fibronectin receptor concentrations are probably the expression of T cell activation and cell-mediated immunity during Bordetella pertussis infection.

High-molecular-weight proteins of nontypeable Haemophilus influenzae mediate bacterial adhesion to cellular proteoglycans

A family of high-molecular-weight (HMW) surface-exposed proteins of nontypeable Haemophilus influenzae (NT H. influenzae) mediated adherence of these organisms to human epithelium. To better understand the molecular basis for this adherence, the role of glycosaminoglycans (GAGs), substances commonly expressed on cell surfaces, was examined. Bacterial adherence to cells with specific deficiencies in GAG biosynthesis was measured. HMW protein-dependent bacterial adherence to normal cells was significantly greater than adherence to cells deficient in sulfated GAGs or to cells deficient in heparan sulfate but overexpressing chondroitin sulfate. Cells expressing undersulfated heparan sulfate exhibited intermediate levels of bacterial adherence. The addition of exogenous dextran sulfate or heparin inhibited over 70% of the adherence of NT H. influenzae to normal cells, whereas hyaluronic acid and chondroitin sulfate tested at the same concentration (100 micrograms/ml) inhibited bacterial adherence by less than 11%. Treatment of cells with heparinase significantly reduced bacterial adherence. Following electrophoretic separation, HMW proteins were shown to bind directly to radiolabeled heparin. These results indicate that HMW protein-dependent adherence of NT H. influenzae is mediated by cellular sulfated GAGs and that heparan sulfate may be the predominant GAG involved in this process. However, the decreased adherence of bacteria to cells expressing undersulfated heparan sulfate and the inhibition of bacterial adherence by the addition of exogenous dextran sulfate suggest that bacterial adhesion to mammalian cells is likely to be influenced by a variety of factors, including the degree of sulfation and the specificity of the carbohydrate moieties contained in the cellular proteoglycans.

Characterization of murine lung inflammation after infection with parental Bordetella pertussis and mutants deficient in adhesins or toxins

Bordetella pertussis expresses factors such as filamentous hemagglutinin, agglutinogens, pertactin, and pertussis toxin, which participate in bacterial adhesion; pertussis toxin, dermonecrotic toxin, lipopolysaccharide, and tracheal cytotoxin, which are responsible for toxic effects; and adenylate cyclase-hemolysin, which is required to initiate infection. By using a murine respiratory model, we showed that the RGD sequences of filamentous hemagglutinin and pertactin are important for bacterial persistence. However, mutants deficient in filamentous hemagglutinin and agglutinogens or in pertactin and the RGD sequence of filamentous hemagglutinin behaved as did wild-type B. pertussis, i.e., induced bronchopneumonia, alveolitis, and an influx of macrophages, lymphocytes, and polymorphonuclear leukocytes into bronchoalveolar lavage fluids. These results suggest that these adhesins are not involved in the induction of pulmonary lesions following infection. The intensity of inflammation was markedly reduced after infection with mutants deficient in either hemolytic activity or pertussis toxin expression, whereas a mutant devoid of adenylate cyclase activity behaved as did the avirulent mutant. Pertussis toxin and adenylate cyclase-hemolysin may act indirectly by altering immune cell functions and thus allowing other factors, such as filamentous hemagglutinin, agglutinogens, and pertactin, to trigger adhesion and lipopolysaccharide, dermonecrotic toxin, and tracheal cytotoxin to induce their toxic effects. However, it is possible that pertussis toxin is also responsible for the induction of some pulmonary alterations.

The 70-kilodalton pertussis toxin-binding protein in Jurkat cells

125I-ASD photoaffinity-labeling derivatives of pertussis toxin (125I-ASD-PT) or lipopolysaccharide (125I-ASD-LPS) labeled similar 70-kDa proteins in Jurkat cells, a cell line derived from human CD4+ T lymphocytes. Labeling of this 70-kDa protein by 125I-ASD-PT was inhibited by underivatized PT but not by underivatized LPS. However, an immunoglobulin M monoclonal antibody with specificity for the p73 LPS receptor in murine splenocytes (S. W. Bright, T.-Y. Chen, L. M. Flebbe, M.-G. Lei, and D. C. Morrison, J. Immunol. 145:1-7, 1990) inhibited 125I-ASD-PT labeling of the 70-kDa species in Jurkat cells. Our results suggested that PT may bind to the same 70-kDa protein as LPS does in Jurkat cells but that PT and LPS bind to different sites on this receptor candidate. 125I-ASD-PT photoaffinity labeling of the 70-kDa protein was also inhibited by underivatized glycoproteins to which PT has been shown to bind, and this inhibition correlated with the relative binding affinities of the glycoproteins for PT. 125I-ASD derivatives of two sialic acid-specific plant lectins, Maackia amurensis leukoagglutinin and Sambucus nigra agglutinin, with oligosaccharide binding specificities similar to those of PT also labeled a 70-kDa protein in Jurkat cells. This suggests that the 70-kDa PT receptor candidate in Jurkat cells likely contains sialooligosaccharide sequences to which PT, M. amurensis leukoagglutinin, and S. nigra agglutinin bind. The cross-reacting epitope recognized by monoclonal antibody 5D3 in this 70-kDa species might overlap the PT- and LPS-binding sites.

Microtiter plate adherence assay and receptor analogs for Mycoplasma hyopneumoniae

A microtiter plate adherence assay for Mycoplasma hyopneumoniae was established by use of purified swine tracheal cilia which contained receptors for the mycoplasmas. M. hyopneumoniae bound specifically to plates coated with solubilized cilia. The binding was dependent on both the concentration of cilia and the number of mycoplasmas. Dextran sulfate, heparin, chondroitin sulfate, laminin, mucin, and fucoidan significantly inhibited the binding of the mycoplasmas. The six inhibitors also disrupted the adherence of the mycoplasmas to intact ciliated cells. Preincubation with either mycoplasmas or cilia indicated that heparin, mucin, fucoidan, and chondroitin sulfate interacted with the adhesive molecules on the surface of the mycoplasmas, while laminin blocked the receptors in cilia. The basis for the inhibition induced by dextran sulfate was unknown. Treatment of cilia with neuraminidase appeared to promote adherence of the mycoplasmas, whereas treatment of cilia with sodium metaperiodate decreased binding. These results indicate that receptors for M. hyopneumoniae in the ciliated epithelium of the respiratory tract of pigs are glycoconjugate in nature.

Heparin-inhibitable lectin activity of the filamentous hemagglutinin adhesin of Bordetella pertussis

Bordetella pertussis, the etiologic agent of whooping cough, produces an outer membrane-associated filamentous hemagglutinin (FHA) which is the major adhesin of this organism. FHA exhibits a lectin-like activity for heparin and dextran sulfate. By using in vitro adherence assays to cultured epithelial cells, the attachment of B. pertussis was reduced in the presence of sulfated polysaccharides such as heparin and dextran sulfate but not in the presence of dextran, indicating the crucial role of polysaccharide sulfation. In addition, inhibition of cellular sulfation by chlorate treatment of the cells resulted in a reduction of B. pertussis adherence, suggesting that epithelial cell surface-exposed sulfated glycoconjugates may serve as receptors for the microorganism. B. pertussis mutant strains deficient in FHA production expressed residual adherence that was no longer inhibited by sulfated polysaccharides. In addition, purified FHA displayed heparin-inhibitable binding to epithelial cells. Mapping experiments of the heparin-binding site of FHA indicated that this site is different from the RGD site and the recently proposed carbohydrate-binding site involved in the interaction of FHA with lactosylceramide. This result demonstrates that FHA contains at least three different binding sites, a feature unusual for bacterial adhesions but similar to features of eukaryotic adhesins and extracellular matrix proteins.

Bordetella pertussis induces apoptosis in macrophages: role of adenylate cyclase-hemolysin

Bordetella pertussis, the causative agent of whooping cough, has been shown recently to enter and survive in epithelial cells and macrophages in vitro. In the present study, we show that B. pertussis is cytotoxic for J774A.1 cells, a monocyte-macrophage cell line, and for murine alveolar macrophages. We demonstrate that cell cytotoxicity mediated by B. pertussis occurred through apoptosis, as shown by changes in nuclear morphology and by host cell DNA fragmentation. Parental strains and a mutant deficient in pertussis toxin expression are able to induce apoptosis, whereas avirulent mutant or adenylate cyclase-hemolysin-deficient mutants are not cytotoxic. Both adenylate cyclase and hemolytic activities are required for programmed cell death. These results show that induction of apoptosis is dependent on the expression of adenylate cyclase-hemolysin. The infection of murine alveolar macrophages in primary culture with B. pertussis leads to apoptosis, suggesting that this process might be relevant in vivo. The ability of B. pertussis to promote cell death may be important for the initiation of infection, bacterial survival, and escape of the host immune response.

Adhesion of Bordetella pertussis to eukaryotic cells requires a time-dependent export and maturation of filamentous hemagglutinin

Bordetella pertussis, the human pathogen of whooping cough, when grown at 22 degrees C is nonvirulent and unable to bind eukaryotic cells. In response to a temperature shift to 37 degrees C, the bacterium acquires the ability to bind eukaryotic cells in a time-dependent fashion. By studying in vitro the temperature-induced transition, from the nonvirulent to the virulent state, we found that binding to CHO cells is mediated by the Arg-Gly-Asp-containing domain of filamentous hemagglutinin (FHA), a protein with multiple binding specificities. This protein is synthesized as a 367-kDa polypeptide within 10 min after temperature shift, but requires 2 hr before it is detected on the bacterial cell surface and starts to bind CHO cells. Mutations affecting the cell surface export of FHA abolish bacterial adhesion to CHO cells, while mutations in the outer membrane protein pertactin strongly reduce binding. This suggests that multiple chaperon proteins are required for a correct function of FHA. Finally, several hours after maximum binding efficiency is achieved, the N-terminal 220-kDa portion of FHA that contains the binding regions is cleaved off, possibly to release the bacteria from the bound cells and facilitate spreading. The different forms of FHA may play different roles during bacterial infection.

Prokaryotic peptides that block leukocyte adherence to selectins

Pertussis toxin binds target cells through the carbohydrate recognition properties of two subunits, S2 and S3, which share amino acid sequence similarity with the lectin domains of the eukaryotic selectin family. Selectins appear on inflamed endothelial cells and promote rolling of leukocytes by reversibly binding carbohydrates. S2, S3, and synthetic peptides representing their carbohydrate recognition domains competitively inhibited adherence of neutrophils to selectin-coated surfaces and to endothelial cells in vitro. These proteins and peptides also rapidly upregulated the function of the leukocyte integrin CD11b/CD18. These findings implicate mimicry of eukaryotic selectins by prokaryotic adhesive ligands and link the mechanisms underlying leukocyte trafficking to microbial pathogenesis.

The filamentous haemagglutinin, a multifaceted adhesion produced by virulent Bordetella spp

Filamentous haemagglutinin (FHA) is the major attachment factor produced by virulent Bordetella spp. Similar to the other virulence factors, its production is tightly regulated by a two-component system in response to environmental changes. Although of impressive size (c. 220 kDa), it is very efficiently released into the culture supernatant of Bordetella pertussis. Its biogenesis involves complex processing of a larger precursor with a calculated molecular mass of 370 kDa. Export of FHA into the culture medium depends on an outer membrane protein homologous to haemolysin accessory proteins. Purified extracellular FHA is able to increase the adherence of other pathogens to the host, which may contribute to super-infection in whooping cough. Although FHA- mutants colonize lungs as efficiently as the wild-type parent strains, immune responses against FHA appear to protect against colonization. Unlike many other adhesins, FHA expresses at least three different attachment activities, one specific for the CR3 integrins of macrophages, one involving a carbohydrate-binding site, specific for interactions with cilia, and a heparin-binding activity that may be important for interaction of B. pertussis with epithelial cells or extracellular matrices.

Identification of a carbohydrate recognition domain in filamentous hemagglutinin from Bordetella pertussis

The adherence of Bordetella pertussis to ciliated cells and macrophages is critical to colonization and infection of the respiratory tract. Adherence to both types of cells involves the recognition of eukaryotic carbohydrates by the bacterial adhesin filamentous hemagglutinin (Fha). The carbohydrate recognition domain (CRD) of Fha is considered an important antigen for subcomponent vaccines to maximize the generation of antiadherence antibodies capable of protecting against colonization. For identification of the CRD of Fha, a bank of eight monoclonal antibodies (MAbs) that mapped to four contiguous regions were tested for their ability to block Fha binding to lactosylceramide or to block bacterial binding to ciliated cells. Only MAb 12.5A9, which maps to amino acid residues 1141 to 1279, blocked both Fha binding to lactosylceramide and bacterial binding to ciliated cells. An 18-kDa polypeptide corresponding to this region was expressed in Escherichia coli. Cell lysates containing this protein bound to lactosylceramide in a manner identical to that of native Fha. Mutant strains of B. pertussis that contained an in-frame deletion of the coding sequence for this region produced a truncated Fha that showed negligible cross-reactivity with MAb 12.5A9. In an adherence assay, these mutant strains failed to bind efficiently to either ciliated cells or macrophages. The numbers of adherent bacteria for these strains were reduced to the number obtained with a nonadherent strain. We conclude that the region defined by residues 1141 to 1279 of Fha constitutes a CRD critical for bacterial adherence and represents a potential candidate for a subcomponent vaccine.

Characterization of pertussis toxin analogs containing mutations in B-oligomer subunits

The S2, S3, and S4 subunit genes of pertussis toxin (PT) from Bordetella pertussis were subjected to site-directed mutagenesis, and the resultant PT analogs were assayed for altered biological properties. PT analogs S2(T91,R92,N93) delta and S2(Y102A,Y103A) exhibited reduced binding to fetuin. Several PT analogs with mutations in the S2, S3, or S4 subunit showed reduced in vitro toxicity, as measured in the Chinese hamster ovary (CHO) cell clustering assay. In particular, PT analogs S3(Y82A) and S3(I91,Y92,K93) delta retained 10% or less residual toxicity. These mutants also exhibited significantly lower mitogenic and hemagglutinating activities and reduced in vivo activities, as measured by the histamine sensitization and leukocytosis assays. The S4(K54A,K57A) PT analog had significantly reduced CHO cell clustering activity, though other biological activities remained unaffected. PT analogs S1(E129G)/S3(Y82A) and S1(E129G)/S3(I91,Y92,K93) delta displayed a cumulative effect of the S1 and S3 mutations for both in vitro and in vivo toxic activities. These PT analogs, as well as S1(R9K,E129G)/S3(K82A) and S1(R9K,E129G)/S3(I91,Y92,K93) delta, still expressed an epitope which elicits a neutralizing antitoxin antibody and were protective in the mouse intracerebral challenge test. Recombinant pertussis vaccines based on PT analogs with detoxifying mutations in multiple subunits may thus represent the next generation of improved whooping cough vaccines.

P fimbriae of uropathogenic Escherichia coli as multifunctional adherence organelles

P fimbriae are the major single virulence factor of uropathogenic Escherichia coli strains. Recent analyses have shown that P fimbriae possess two distinct binding specificities mediated by different fimbrial subunits. P fimbriae bind to Gal alpha (1-4)Gal-containing globoseries of glycolipids of epithelial cells; this binding is mediated by the lectin-like minor protein G of the filament. In vitro mapping of the human urinary tract for binding sites of P fimbriae has revealed that they bind in a Gal alpha (1-4)Gal-inhibitable manner to epithelia of kidney and bladder. On the other hand, P fimbriae bind to immobilized fibronectin and its amino- and carboxyterminal fragments; this binding is dependent on the E and the F minor proteins of the P-fimbrial filament and seems to be based on a protein-protein interaction. The P fimbriae-fibronectin interaction has been demonstrated also on frozen sections of kidney. P fimbriae thus possess two tissue-adherence properties: one specific for epithelial glycoconjugates and the other for fibronectin of subepithelial extracellular matrices. P-fimbrial binding to epithelial glycoconjugates seems to be important in determining the host tropism and enabling the ascent of E. coli urinary tract infections. Binding to fibronectin may be important in secondary phases of the infection, e.g. after epithelial injury.

High-molecular-weight proteins of nontypable Haemophilus influenzae mediate attachment to human epithelial cells

Nontypable Haemophilus influenzae are Gram-negative bacilli that represent a common cause of human disease. These organisms initiate infection by colonizing the upper respiratory tract. Despite the essential role of colonization, the bacterial determinants of this process remain poorly defined. We recently identified a family of surface-exposed high-molecular-weight proteins of nontypable H. influenzae that are related to filamentous hemagglutinin, a critical adherence factor of Bordetella pertussis. The genes encoding the two such high-molecular-weight proteins (HMW-1 and HMW-2) expressed by a prototypic nontypable H. influenzae strain have now been cloned and sequenced. In this study we examined the role of the HMWs in adherence to human epithelial cells. We found that loss of expression of HMW-1 by the prototypic strain and a HMW-1-like protein in a heterologous nontypable H. influenzae strain markedly decreased the capacity to adhere. The absence of expression of both HMW-1 and HMW-2 in the prototypic strain or their homologs in the second strain was associated with a further decrease in adherence. Expression of either HMW-1 or HMW-2 in nonadherent laboratory strains of Escherichia coli resulted in acquisition of the adherence phenotype. These results indicate that both HMW-1 and HMW-2 and the homologous proteins from a second strain can mediate attachment. We speculate that these proteins and the related proteins in other nontypable H. influenzae isolates are important colonization factors.

Protection of mice against respiratory Bordetella pertussis infection by intranasal immunization with P.69 and FHA

Intranasal immunization of adult female Balb/c mice with the Bordetella pertussis antigens FHA or P.69, greatly enhanced their ability to clear B. pertussis from their lungs following aerosol challenge compared with ovalbumin-immunized controls. Low numbers of lymphocytes secreting antibodies (IgG, IgA and IgM) against the immunizing antigens could be isolated from the lungs of immunized mice. Following aerosol challenge with B. pertussis there was a large increase in the numbers of FHA or P.69-specific antibody-secreting cells in the lungs of mice immunized with these antigens. Intranasal immunization, particularly with FHA, also primed mice to develop a systemic serum anti-pertussis antibody response subsequent to challenge. However, pulmonary clearance of B. pertussis correlated most closely with the local antibody response. A strong anti-FHA response was demonstrated in the lungs of mice that received a booster dose of FHA 9 months after their previous exposure to FHA, demonstrating that long immunological memory can develop in the murine respiratory tract following direct application of pertussis antigens to the respiratory tract mucosa.

Two types of bacteria adherent to bovine respiratory tract ciliated epithelium

Two hundred sixty tracheas were obtained from a Philadelphia abattoir under permit from the Department of Agriculture; the tracheas were excised from predominantly Holstein calves of both sexes that weighed approximately 250 kg. Tracheas were transported in normal saline to the laboratory at Thomas Jefferson University, Philadelphia, Pennsylvania. Evidence of bacteria adherent to the tracheal epithelium was found in specimens from 20/24 of these tracheas. The epithelium from each of five tracheas was placed in glutaraldehyde fixative for transmission electron microscopic examination. Epithelium from each of 12 other tracheas was placed in formaldehyde fixative for light microscopic examination. Microscopically, 13 of these 17 bovine tracheal epithelia were observed to contain bacteria located longitudinally parallel to and between cilia and microvilli of ciliated cells. Preparations of ciliary axonemes isolated from the epithelium of seven additional bovine tracheas also contained these bacteria in sections viewed by a transmission electron microscope. These bacteria had two different ultrastructural morphologies: filamentous with a trilaminar-structured cell wall and short with a thick, homogeneously stained cell wall beneath a regularly arrayed surface layer. The short bacillus had surface carbohydrates, including mannose, galactose, and N-acetylgalactosamine, identified by lectin binding. The filamentous bacillus was apparently externally deficient in these carbohydrates. Immunogold staining revealed that the filamentous bacillus was antigenically related to cilia-associated respiratory (CAR) bacillus, which has been identified in rabbit and rodent species. Significantly decreased numbers of cilia were obtained from tracheal epithelium heavily colonized by the filamentous bacilli, suggesting a pathologic change in ciliated cells.

Binding of pertussis toxin to lipid vesicles containing glycolipids

The binding of pertussis toxin and its B oligomer to lipid vesicles containing glycosphingolipids was studied. Both pertussis toxin and the B oligomer bound to lipid vesicles containing ganglioside GD1a. Binding of pertussis toxin to these vesicles decreased upon treatment of the vesicles with neuraminidase, suggesting that sialic acid residues are important for efficient binding of the toxin to GD1a.

Role of carbohydrate recognition domains of pertussis toxin in adherence of Bordetella pertussis to human macrophages

Pertussis toxin (PT) and filamentous hemagglutinin can each mediate the association of Bordetella pertussis with human macrophages. Adherence via filamentous hemagglutinin leads to integrin-mediated entry and survival of the bacteria within the human cell. We determined the contribution of PT to bacterial adherence to human macrophages. Plating macrophages on wells coated with recombinant PT subunit 2 (S2) or S3 decreased PT-dependent bacterial binding by greater than 60%; S1, S4, and S5 were ineffective. S3-dependent adherence was reduced 63% +/- 8% by sialic acid, while S2-dependent adherence was reduced 53% +/- 11% by galactose. Loss of the carbohydrate recognition properties of S2 by deletion of residues 40 to 54 or site-specific mutations at Asn-93, His-47, or Arg-50 eliminated the ability of the subunit protein to competitively inhibit bacterial binding. Peptides corresponding to residues 28 to 45 of S2 and S3 competitively inhibited adherence. Treatment of macrophages with antibodies to Le(a) or Le(x) but not CD14, CD15, CD18, or HLA interfered with PT-mediated binding. Exposure of the macrophages to the B oligomer, S2, or S3 increased binding to the CD11b/CD18 integrin. These results indicate that the carbohydrate recognition domains of both S2 and S3 participate in adherence of B. pertussis to human macrophages. The PT receptor(s), as yet unidentified, appears to carry the Le(a) or Le(x) determinants and is functionally capable of modulating integrin-mediated binding to the macrophage.

Comparative roles of the Arg-Gly-Asp sequence present in the Bordetella pertussis adhesins pertactin and filamentous hemagglutinin

Pertactin and filamentous hemagglutinin (FHA), proteins present on the surface of the gram-negative organism Bordetella pertussis, have been shown to contain the putative cell-binding sequence arginine-glycine-aspartic acid (RGD) and to promote eukaryotic cell attachment. The attachment of epithelial cells to purified pertactin and the entry of B. pertussis into human HeLa cells are both inhibited by an RGD-containing peptide derived from the pertactin sequence. In contrast, an RGD-containing peptide derived from the FHA sequence has no effect on either the attachment of epithelial cells to purified FHA or the entry of B. pertussis into HeLa cells. Staphylococcus aureus organisms coated with pertactin or FHA, purified from B. pertussis, enter HeLa cells more efficiently than S. aureus cells coated with bovine serum albumin. The pertactin-enhanced entry of S. aureus is inhibited by 75% in the presence of the RGD peptide from pertactin, whereas the RGD peptide derived from FHA has no effect on the increased entry promoted by the pertactin-coated or by the FHA-coated S. aureus. These results indicate that the active uptake of B. pertussis by certain mammalian cells may be mediated by the interaction of the RGD site found in pertactin with eukaryotic cell surface receptors.

Properties of pertussis toxin B oligomer assembled in vitro from recombinant polypeptides produced by Escherichia coli

The subunits that make up the pentameric B oligomer of pertussis toxin (S2, S3, S4, and S5) were individually synthesized as recombinant polypeptides in Escherichia coli, isolated as insoluble inclusion bodies, and assembled into a multimeric form in vitro by spontaneous association following treatment with a chaotropic agent, reduction, and reoxidation. The recombinant B multimer, purified by fetuin-Sepharose affinity chromatography, contained all four of the individual subunits and possessed the mitogenic and hemagglutinating activities characteristic of the native B oligomer. Immunization of mice with the recombinant B oligomer elicited antibodies that neutralized pertussis toxin in vitro and, moreover, provided protection in vivo against the leukocytosis-promoting activity of the toxin. These results demonstrate the potential for assembly of complex multimeric proteins from recombinant DNA-derived polypeptides and provide a novel means for production of an acellular pertussis vaccine component.

Cloning, expression, and DNA sequence analysis of genes encoding nontypeable Haemophilus influenzae high-molecular-weight surface-exposed proteins related to filamentous hemagglutinin of Bordetella pertussis

A group of high-molecular-weight surface-exposed proteins of nontypeable Haemophilus influenzae are major targets of human serum antibody (S. J. Barenkamp and F. F. Bodor, Pediatr. Infect. Dis. J. 9:333-337, 1990). To further characterize these proteins, we cloned and sequenced genes encoding two related high-molecular-weight proteins from a prototype nontypeable Haemophilus strain. The gene encoding a 120-kDa Haemophilus protein consisted of a 4.4-kbp open reading frame, and the gene encoding a 125-kDa protein consisted of a 4.6-kbp open reading frame. The first 1,259 bp of the two genes were identical. Thereafter, the sequences began to diverge, but overall they were 80% identical, and the derived amino acid sequences showed 70% identity. A protein sequence homology search demonstrated similarity between the derived amino acid sequences of both cloned genes and the derived amino acid sequence of the gene encoding filamentous hemagglutinin, a surface protein produced by the gram-negative pathogen Bordetella pertussis. Antiserum raised against a recombinant protein encoded by the 4.6-kbp open reading frame recognized both the 120- and the 125-kDa proteins in the prototype strain as well as antigenically related high-molecular-weight proteins in 75% of a collection of 125 epidemiologically unrelated nontypeable H. influenzae strains. The antiserum directed against the recombinant protein also recognized purified filamentous hemagglutinin. A murine monoclonal antibody to filamentous hemagglutinin recognized both the 120-kDa and the 125-kDa protein in the prototype strain as well as proteins identical to those recognized by the recombinant-protein antiserum in 35% of the nontypeable H. influenzae strain collection. Thus, we have identified and partially characterized a group of highly immunogenic surface-exposed proteins of nontypeable H. influenzae which are related to the filamentous hemagglutinin of B. pertussis.

Pertussis toxin has eukaryotic-like carbohydrate recognition domains

Bordetella pertussis is bound to glycoconjugates on human cilia and macrophages by multiple adhesins, including pertussis toxin. The cellular recognition properties of the B oligomer of pertussis toxin were characterized and the location and structural requirements of the recognition domains were identified by site-directed mutagenesis of recombinant pertussis toxin subunits. Differential recognition of cilia and macrophages, respectively, was localized to subunits S2 and S3 of the B oligomer. Despite greater than 80% sequence homology between these subunits, ciliary lactosylceramide exclusively recognized S2 and leukocytic gangliosides bound only S3. Substitution at residue 44, 45, 50, or 51 in S2 resulted in a shift of carbohydrate recognition from lactosylceramide to gangliosides. Mutational exchange of amino acid residues 37-52 between S2 and S3 interchanged their carbohydrate and target cell specificity. Comparison of these carbohydrate recognition sequences to those of plant and animal lectins revealed that regions essential for function of the prokaryotic lectins were strongly related to a subset of eukaryotic carbohydrate recognition domains of the C type.

Detection of Bordetella pertussis associated with the alveolar macrophages of children with human immunodeficiency virus infection

In humans, infection with Bordetella pertussis is considered to be localized to an epithelial surface. However, an intracellular state in cultured cells and in the macrophages of infected animals has been shown. By using indirect immunofluorescence with a monoclonal antibody, it was found that 3 of 20 bronchoalveolar lavage specimens from children with human immunodeficiency virus infection had B. pertussis associated with pulmonary alveolar macrophages. None of the cultures from the patients grew B. pertussis. The B. pertussis appeared to be intracellular.

Synthesis and characterization of a Pertussis toxin-biotin conjugate

We prepared a Pertussis toxin-biotin conjugate and found its biological properties to be similar to those of native Pertussis toxin with respect to the hemagglutination, Chinese hamster ovary cell, and lymphocyte proliferation assays. Direct binding to Chinese hamster ovary and Jurkat cells was observed using fluorescence microscopy. Pertussis toxin-biotin was also found to possess similar glycoconjugate binding specificities as those of 125I-labeled Pertussis toxin.

Integrin-mediated localization of Bordetella pertussis within macrophages: role in pulmonary colonization

The adherence of Bordetella pertussis to human respiratory cilia is critical to the pathogenesis of whooping cough but the significance of bacterial attachment to macrophages has not been determined. Adherence to cilia and macrophages is mediated by two large, nonfimbrial bacterial proteins, filamentous hemagglutinin (FHA), and pertussis toxin (PT). PT and FHA both recognize carbohydrates on cilia and macrophages; FHA also contains an Arg-Gly-Asp (RGD) sequence which promotes bacterial association with the macrophage integrin complement receptor 3 (CR3). We determined that virulent B. pertussis enter and survive in mammalian macrophages in vitro and that CR3 is important for this uptake process. We then determined the relative contribution of CR3 versus carbohydrate-dependent interactions to in vivo pulmonary colonization using a rabbit model. B. pertussis colonized the lung as two approximately equal populations, one extracellular population attached to ciliary and macrophage surface glycoconjugates and another population within pulmonary macrophages. Loss of the CR3 interaction, either by mutation of FHA or treatment with antibody to CR3, disrupted accumulation of viable intracellular bacteria but did not prevent lung pathology. In contrast, elimination of carbohydrate-bound bacteria, either by a competitive receptor analogue or an anti-receptor antibody, was sufficient to prevent pulmonary edema. We propose that CR3-dependent localization of B. pertussis within macrophages promotes persistence of bacteria in the lung without pulmonary injury. On the other hand, the presence of extracellular bacteria adherent to cilia and macrophages in carbohydrate-dependent interactions is associated with pulmonary pathology.

Interaction of the Bordetella pertussis filamentous hemagglutinin with heparin

Heparin, a glycosaminoglycan synthesized in connective tissue-mast cells, appeared to inhibit the hemagglutination of rabbit erythrocytes induced by the filamentous hemagglutinin (FHA), a major adhesin of Bordetella pertussis. This inhibition suggested an interaction of heparin with the FHA region responsible for the hemagglutination activity. FHA-heparin interactions may play a role in bacterial attachment and persistence in the lungs during human pertussis. To confirm a direct FHA-heparin interaction, heparin was used as ligand in an affinity chromatography procedure. This technique allowed to purify FHA directly from the bacterial culture medium in a single-step using heparin-Sepharose CL-6B or Zetaffinity heparin 60 disks. The purified FHA was highly immunoreactive with anti-FHA monoclonal antibodies and showed no signs of degradation after 15 successive cycles of freezing-thawing. The described purification method is simple, and suitable for the rapid preparation of FHA.

Pertactin, an Arg-Gly-Asp-containing Bordetella pertussis surface protein that promotes adherence of mammalian cells

A 69-kDa protein has been identified on the surface of the Gram-negative pathogen Bordetella pertussis that can elicit a protective immune response in animal models. This protein is associated with virulent strains of B. pertussis but its function has remained unclear. In this report we demonstrate that purified preparations of the 69-kDa outer membrane protein can promote the attachment of Chinese hamster ovary (CHO) cells. The interaction between the mammalian cells and this protein can be specifically inhibited by an Arg-Gly-Asp (RGD)-containing synthetic peptide that is homologous with a region found in the 69-kDa protein sequence. These studies indicate that a specific cell binding site containing an Arg-Gly-Asp sequence may be involved in the interaction of this bacterial protein with mammalian cell surfaces. To further investigate the role of this protein as a bacterial adhesin, a mutant of B. pertussis W28 that does not express the 69-kDa protein was constructed using the plasmid vector pRTP1. This mutant was 30-40% less efficient at adhering to CHO cells and to human HeLa cells than was the parent strain. These data support a role for this 69-kDa outer membrane protein in the attachment of B. pertussis to mammalian cells. We propose the name "pertactin" for this protein.

Effects of Bordetella pertussis infection on human respiratory epithelium in vivo and in vitro

Bordetella pertussis infection probably involves attachment to and destruction of ciliated epithelial cells, but most previous studies have used animal tissue. During an epidemic, nasal epithelial biopsy specimens of 15 children (aged 1 month to 3 1/2 years) with whooping cough were examined for ciliary beat frequency, percent ciliation of the epithelium, and ciliary and epithelial cell ultrastructure. In addition, the in vitro effects of filtrates from a 24-h broth culture and of tracheal cytotoxin derived from B. pertussis on human nasal tissue organ culture were measured. B. pertussis was cultured from nasal swabs from 12 children. The mean ciliary beat frequency of their nasal biopsy specimens, 11.3 Hz (range, 10.4 to 13.0 Hz) was similar to that found in biopsy specimens from 10 normal children (mean, 12.5 Hz; range, 11.8 to 13.5 Hz). The abnormalities of the epithelium observed in 14 of 15 patients were a reduction in the number of ciliated cells, an increase in the number of cells with sparse ciliation, an increase in the number of dead cells, and extrusion of cells from the epithelial surface. In vitro, neither culture filtrate nor tracheal cytotoxin had any acute effect on ciliary function, but culture filtrate and tracheal cytotoxin (1 and 5 microM, respectively) caused extrusion of cells from the epithelial surface of turbinate tissue, loss of ciliated cells, an increased frequency of sparsely ciliated cells, and toxic changes in some cells. These changes were dose dependent and progressive, and between 36 and 90 h ciliary beating ceased. The observations made with patient tissue confirm that B. pertussis infection damages ciliated epithelium, and the in vitro experiments suggest that tracheal cytotoxin may be responsible for the abnormalities observed in vivo.

Lymphocyte receptors for pertussis toxin

We have investigated human T-lymphocyte receptors for pertussis toxin by affinity isolation and photoaffinity labeling procedures. T lymphocytes were obtained from peripheral human blood, surface iodinated, and solubilized in Triton X-100. The iodinated mixture was then passed through pertussis toxin-agarose, and the fractions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Autoradiography of the fixed, dried gels revealed several bands in the pertussis toxin-bound fraction that were not observed in fractions obtained from histone or fetuin-agarose. Further investigations employed a photoaffinity labeling reagent, sulfosuccinimidyl 2-(p-azido-salicylamido)-1,3'-dithiopropionate, to identify pertussis toxin receptors in freshly isolated peripheral blood monocytic cells, T lymphocytes, and Jurkat cells. In all three cell systems, the pertussis toxin affinity probe specifically labeled a single protein species with an apparent molecular weight of 70,000 that was not observed when the procedure was performed in the presence of excess unmodified pertussis toxin. A protein comparable in molecular weight to the one detected by the photoaffinity labeling technique was also observed among the species that bound to pertussis toxin-agarose. The results suggest that pertussis toxin may bind to a 70,000-Da receptor in human T lymphocytes.

Comparison of the lectin-like activity of pertussis toxin with two plant lectins that have differential specificities for alpha (2-6) and alpha (2-3)-linked sialic acid

In this report we have compared the lectin-like properties of Pertussis toxin with two plant lectins which are known to possess different specificities towards terminal Neu5Ac Gal linkages on glycoconjugates. The hemagglutinin from elderberry bark (Sambucus nigra) has a binding specificity for terminal Neu5Ac alpha (2-6) Gal sequences and was found to bind a series of glycoconjugates with a similar specificity as Pertussis toxin. The binding specificity of Pertussis toxin was different from that of the leukoagglutinin from the seeds of Maackia amurensis which preferentially binds terminal Neu5Ac alpha (2-3) Gal sequences. These observations confirm the specificity of Pertussis toxin for Neu5Ac alpha (2-6) Gal glycoconjugate sequences.

Cryptococcus neoformans, Candida albicans, and other fungi bind specifically to the glycosphingolipid lactosylceramide (Gal beta 1-4Glc beta 1-1Cer), a possible adhesion receptor for yeasts

The role of glycosphingolipids as adhesion receptors for yeasts was examined. Cryptococcus neoformans, Candida albicans, and Saccharomyces cerevisiae, as well as Histoplasma capsulatum and Sporotrichum schenckii (in their yeast phases), bound specifically to lactosylceramide (Gal beta 1-4Glc beta 1-1Cer), as measured by overlaying glycosphingolipid chromatograms with 125I-labeled organisms. An unsubstituted galactosyl residue was required for binding, because the yeasts did not bind to glucosylceramide (Glc beta 1-1Cer) derived from lactosylceramide by treatment with beta-galactosidase or to other neutral or acidic glycosphingolipids tested that contained internal lactosyl residues. Interestingly, the yeasts preferentially bound to the upper band of the lactosylceramide doublet in human lung and bovine erythrocytes, suggesting that the ceramide structure also affects binding. Active metabolism of the yeasts was required for binding to lactosylceramide, as binding was maximal in buffer containing glucose and was almost completely abolished in nutrient-deficient medium. C. neoformans also bound to human glioma brain cells grown in monolayers, and this binding was inhibited by liposomes containing lactosylceramide but not by liposomes containing glucosylceramide. Lactosylceramide is a major glycosphingolipid in these cells and the only one to which the yeasts bound. As lactosylceramide is widely distributed in epithelial tissues, this glycosphingolipid may be the receptor for yeast colonization and disseminated disease in humans.

Recognition of a bacterial adhesion by an integrin: macrophage CR3 (alpha M beta 2, CD11b/CD18) binds filamentous hemagglutinin of Bordetella pertussis

During the course of whooping cough, Bordetella pertussis interacts with alveolar macrophages and other leukocytes on the respiratory epithelium. We report here mechanisms by which these bacteria adhere to human macrophages in vitro. Whole bacteria adhere by means of two proteins, filamentous hemagglutinin (FHA) and pertussis toxin, either of which is sufficient to mediate adherence. FHA interacts with two classes of molecules on macrophages, galactose-containing glycoconjugates and the integrin CR3 (alpha M beta 2, CD11b/CD18). The interaction between CR3 and FHA involves recognition of the Arg-Gly-Asp (RGD) sequence at positions 1097-1099 in FHA. This study demonstrates that bacterial adherence can be based on the interaction of a bacterial adhesin RGD sequence with an integrin and that bacterial adhesins can have multiple binding sites characteristic of eukaryotic extracellular matrix proteins.

Blocking of Mycobacterium leprae adherence to dissociated Schwann cells by anti-mycobacterial antibodies

The association of Mycobacterium leprae with Schwann cells may represent an early crucial step in M. leprae pathogenesis. Using a dissociated Schwann-cell system and anti-mycobacterial monoclonal and polyclonal antibodies directed against surface and cytoplasmic components, we investigated the nature of M. leprae epitopes that mediate cytadhesion. Antibodies to polysaccharide and lipid components of M. leprae cell wall inhibited cytadhesion, whereas those directed against both surface and cytoplasmic protein epitopes did not show any such effect. No synergistic or antagonistic activity in inhibiting cytadhesion was observed when antibodies were used in combination. Thus, the association of M. leprae with Schwann cells may be mediated collectively by more than one of its lipid/polysaccharide epitopes. Also, a role for humoral immunity in intervention in the initial steps of M. leprae pathogenesis needs to be considered.

Lectinlike properties of pertussis toxin

We have examined the lectinlike properties of pertussis toxin by binding-inhibition assays and affinity chromatography of goose erythrocyte membranes. Although pertussis toxin and wheat germ agglutinin apparently recognize similar sugar sequences on glycoproteins, the binding activities of the two lectins are not identical.

Filamentous hemagglutinin of Bordetella pertussis: nucleotide sequence and crucial role in adherence

Filamentous hemagglutinin is a surface-associated adherence protein of Bordetella pertussis, which is a component of some new acellular pertussis vaccines. The nucleotide sequence of an open reading frame that encompasses the filamentous hemagglutinin structural gene, fhaB, suggests that proteolytic processing is necessary to generate the mature 220-kDa filamentous hemagglutinin product. An Arg-Gly-Asp (RGD) tripeptide is found within filamentous hemagglutinin that may be involved in its adherence properties. An internal in-frame deletion in fhaB, encompassing the RGD region, causes loss of B. pertussis-binding to ciliated eukaryotic cells, confirming a potential role for this protein in host-cell binding and infection.