Antigenic quantitation of type 1 fimbriae on the surface of Escherichia coli cells by an enzyme-linked immunosorbent inhibition assay

Flow-aligned, single-shot fiber diffraction using a femtosecond X-ray free-electron laser

A major goal for X-ray free-electron laser (XFEL) based science is to elucidate structures of biological molecules without the need for crystals. Filament systems may provide some of the first single macromolecular structures elucidated by XFEL radiation, since they contain one-dimensional translational symmetry and thereby occupy the diffraction intensity region between the extremes of crystals and single molecules. Here, we demonstrate flow alignment of as few as 100 filaments (Escherichia coli pili, F-actin, and amyloid fibrils), which when intersected by femtosecond X-ray pulses result in diffraction patterns similar to those obtained from classical fiber diffraction studies. We also determine that F-actin can be flow-aligned to a disorientation of approximately 5 degrees. Using this XFEL-based technique, we determine that gelsolin amyloids are comprised of stacked β-strands running perpendicular to the filament axis, and that a range of order from fibrillar to crystalline is discernable for individual α-synuclein amyloids.

Nitazoxanide inhibits biofilm production and hemagglutination by enteroaggregative Escherichia coli strains by blocking assembly of AafA fimbriae

Enteroaggregative Escherichia coli (EAEC) strains have emerged as common causes of persistent diarrhea and malnutrition among children and HIV-infected persons. During infection, EAEC typically adheres to the intestinal mucosa via fimbrial adhesins, which results in a characteristic aggregative pattern. In the study described here we investigated whether the broad-spectrum antiparasitic and antidiarrheal drug nitazoxanide (NTZ) might be active against EAEC in vitro. While E. coli strains were resistant to NTZ in rich Luria-Bertani medium (MIC > 64 microg/ml), the drug was slightly inhibitory in a minimal medium supplemented with glucose (MinA-G medium; MIC, approximately 32 microg/ml). NTZ also inhibited biofilm production by strain EAEC 042 in both Dulbecco's modified Eagle's medium and MinA-G medium with a 50% inhibitory concentration of approximately 12 microg/ml. Immunofluorescence and immunoblot analyses with antibody against the major fimbrial subunit AafA of aggregative adherence fimbriae vaariant II (AAF/II) established that the numbers of AAF/II filaments on bacteria grown in the presence of NTZ were dramatically reduced. Comparative quantitative reverse transcription-PCR and reporter gene fusions (aafA::phoA) indicated that aafA expression was unaffected by NTZ, while aggR transcript levels and aggR::lacZ expression were increased approximately 10- and 2.5-fold, respectively, compared with that for the untreated controls. More generally, NTZ inhibited hemagglutination (HA) of red blood cells by the non-biofilm-producing strain JM221 expressing either AAF/I or type I fimbriae. Our findings suggest that the inhibitory action of NTZ on biofilm formation and HA is likely due to inhibition of fimbrial assembly. Antimicrobial agents that inhibit the assembly or function of fimbrial filaments should be good candidates for the prevention of infection.

FimH alleles direct preferential binding of Salmonella to distinct mammalian cells or to avian cells

This study aimed to determine whether allelic variants of the FimH adhesin from Salmonella enterica confer differential bacterial binding to different types of mammalian cells [murine bone marrow-derived dendritic cells (DCs) and HEp-2 cells] and chicken leukocytes. Although the type 1 fimbriated S. enterica serovar Typhimurium strains AJB3 (SR-11 derivative) and SL1344 both aggregated yeast cells, only the former bound efficiently to DCs and HEp-2 cells. Type 1 fimbriae-mediated binding to DCs having previously been shown to require the FimH adhesin and to be inhibited by mannose, FimH sequences from strains SL1344 and AJB3 were compared and found to differ by only one residue, asparagine 158 in SL1344 being replaced by a tyrosine in AJB3. The importance of residue 158 for FimH-mediated binding was further confirmed in recombinant Escherichia coli expressing S. enterica type 1 fimbriae with a variety of substitutions engineered at this position. Additional studies with the 'non-adhesive' FimH of a type 2 fimbriated S. enterica serovar Gallinarum showed that this FimH did not mediate bacterial binding to murine DCs or HEp-2 cells. However, the type 2 FimH significantly improved bacterial adhesion to chicken leukocytes, in comparison to the type 1 FimH of strain AJB3, attributing for the first time a function to the type 2 fimbriae of S. enterica. Consequently, our data show that allelic variation of the S. enterica FimH adhesin directs not only host-cell-specific recognition, but also distinctive binding to mammalian or avian receptors. It is most relevant that this allele-specific binding profile parallels the host specificity of the respective FimH-expressing pathogen.

Adhesin-dependent binding and uptake of Salmonella enterica serovar Typhimurium by dendritic cells

Salmonella enterica serovar Typhimurium can be internalized by immature dendritic cells (DCs). The interacting host and bacterial molecules initiating this process remain uncharacterized. The objective of this study was to investigate whether specific fimbriae are involved in the early step of binding and uptake of Salmonella by DCs. Type 1 fimbriated S. enterica serovar Typhimurium or recombinant Escherichia coli expressing the type 1 fimbriae showed a significantly greater ability to attach to murine bone-marrow-derived DCs than non-fimbriated bacteria. The FimH adhesin was required for efficient interactions with DCs, since fimbriated fimH mutants were impaired in both binding and internalization. Finally, the internalization involved a FimH-dependent process but did not require sipB, a gene essential for Salmonella-mediated invasion of mammalian epithelial cells. Collectively, these data suggest that the bacterial interaction of DCs through the type 1 fimbrial adhesin FimH is sufficient to target S. enterica serovar Typhimurium for cellular uptake.

Hydroxyapatite chromatography of phage-display virions

Hydroxyapatite column chromatography can be used to purify filamentous bacteriophage—the phage most commonly used for phage display. Virions that have been partially purified from culture supernatant by two cycles of precipitation in 2% polyethylene glycol are adsorbed onto the matrix at a density of at least 7.6 × 1013 virions (about 3 mg) per milliliter of packed bed volume in phosphate-buffered saline (PBS; 0.15 M NaCl, 5 mM NaH2PO4, pH-adjusted to 7.0 with NaOH). The matrix is washed successively with wash buffer I (150 mM NaCl, 125 mM phosphate, pH 7.0), wash buffer II (2.55 M NaCl, 125 mM phosphate, pH 7.0), and wash buffer I; after which virions are desorbed in desorption buffer (150 mM NaCl, 200 mM phosphate, pH 7.0), and the matrix is stripped with stripping buffer (150 mM NaCl, 1 M phosphate, pH 7.0). About half of the applied virions are recovered in desorption buffer. Western blot analysis shows that they have undetectable levels of host-derived protein contaminants that are present in the input virions and in virions purified by CsCl equilibrium density gradient centrifugation—the method most commonly used to prepare virions in high purity. Hydroxyapatite chromatography is thus an attractive alternative method for purifying filamentous virions, particularly when the scale is too large for ultracentrifugation to be practical.

The Distinct Binding Specificities Exhibited by Enterobacterial Type 1 Fimbriae Are Determined by Their Fimbrial Shafts

Type 1 fimbriae of enterobacteria are heteropolymeric organelles of adhesion composed of FimH, a mannose-binding lectin, and a shaft composed primarily of FimA. We compared the binding activities of recombinant clones expressing type 1 fimbriae from Escherichia coli, Klebsiella pneumoniae, and Salmonella typhimurium for gut and uroepithelial cells and for various soluble mannosylated proteins. Each fimbria was characterized by its capacity to bind particular epithelial cells and to aggregate mannoproteins. However, when each respective FimH subunit was cloned and expressed in the absence of its shaft as a fusion protein with MalE, each FimH bound a wide range of mannose-containing compounds. In addition, we found that expression of FimH on a heterologous fimbrial shaft, e.g. K. pneumoniae FimH on the E. coli fimbrial shaft or vice versa, altered the binding specificity of FimH such that it closely resembled that of the native heterologous type 1 fimbriae. Furthermore, attachment to and invasion of bladder epithelial cells, which were mediated much better by native E. coli type 1 fimbriae compared with native K. pneumoniae type 1 fimbriae, were found to be dependent on the background of the fimbrial shaft (E. coli versus K. pneumoniae) rather than the background of the FimH expressed. Thus, the distinct binding specificities of different enterobacterial type 1 fimbriae cannot be ascribed solely to the primary structure of their respective FimH subunits, but are also modulated by the fimbrial shaft on which each FimH subunit is presented, possibly through conformational constraints imposed on FimH by the fimbrial shaft. The capacity of type 1 fimbrial shafts to modulate the tissue tropism of different enterobacterial species represents a novel function for these highly organized structures.

Regulatory and functional co-operation of flagella and type 1 pili in adhesive and invasive abilities of AIEC strain LF82 isolated from a patient with Crohn's disease

Genetic determinants that co-operate with type 1 pili to mediate invasion were sought for in adherent-invasive Escherichia coli strain LF82 isolated from a patient with Crohn's disease. Two mutants selected for their impaired ability to invade epithelial cells carried insertions of a TnphoA transposon within genes of the flagellar regulon. An isogenic mutant LF82-DeltafliC deleted for the flagellin-encoding gene did not adhere, did not invade and, surprisingly, expressed only a few type 1 pili. Type 1 pili downregulation resulted from a preferential switch towards the off-position of the invertible DNA element located upstream of the fim operon. This was also correlated with a decrease in the flagellar regulator flhDC mRNA levels, suggesting that the transcriptional regulator FlhD2C2 could control type 1 pili expression directly or indirectly. Transformation with a cloned fim operon allowed bypass of the type 1 pili downexpression in the LF82-DeltafliC mutant. Thus, we showed that flagella play a direct role in the adhesion process via active motility. In addition to downregulating type 1 pili expression, flagella also play an undefined role in strain LF82 invasion, which is not restricted to motility or flagellar structure, but could be related to co-ordinate expression of invasive determinants.

Type 1 pili-mediated adherence of Escherichia coli strain LF82 isolated from Crohn's disease is involved in bacterial invasion of intestinal epithelial cells

We previously characterized the invasive ability of Escherichia coli strain LF82, isolated from an ileal biopsy of a patient with Crohn's disease. In the present study, we performed TnphoA insertion mutagenesis to identify genes involved in LF82 invasion of intestinal epithelial cells. Most of the non-invasive mutants had an insertion mutation within the type 1 pili-encoding operon. Two non-invasive fim mutants, which harboured an insertion within the fimI and fimF genes, still adhered but had lost the ability to induce host cell membrane elongations at the sites of contact with the epithelial cells. Transcomplementation experiments with a fim operon cloned from E. coli K-12 restored both invasive ability and the ability to induce host cell membrane elongations. Expression of the cloned LF82 or K-12 fim operon into the non-invasive laboratory strain JM109 did not confer invasive properties. Thus, these findings showed that: (i) type 1 pili-mediated adherence is involved in LF82-induced perturbation of host cell signalling responsible for membrane elongations; (ii) native shafts are required for type 1 pilus-mediated induction of membrane elongations; (iii) this active phenomenon is a key step in the establishment of the invasive process; and (iv) type 1 pili alone are not sufficient to trigger bacterial internalization.

Molecular basis for the enterocyte tropism exhibited by Salmonella typhimurium type 1 fimbriae

Salmonella typhimurium exhibits a distinct tropism for mouse enterocytes that is linked to their expression of type 1 fimbriae. The distinct binding traits of Salmonella type 1 fimbriae is also reflected in their binding to selected mannosylated proteins and in their ability to promote secondary bacterial aggregation on enterocyte surfaces. The determinant of binding in Salmonella type 1 fimbriae is a 35-kDa structurally distinct fimbrial subunit, FimHS, because inactivation of fimHS abolished binding activity in the resulting mutant without any apparent effect on fimbrial expression. Surprisingly, when expressed in the absence of other fimbrial components and as a translational fusion protein with MalE, FimHS failed to demonstrate any specific binding tropism and bound equally to all cells and mannosylated proteins tested. To determine if the binding specificity of Salmonella type 1 fimbriae was determined by the fimbrial shaft that is intimately associated with FimHS, we replaced the amino-terminal half of FimHS with the corresponding sequence from Escherichia coli FimH (FimHE) that contains the receptor binding domain of FimHE. The resulting hybrid fimbriae bearing FimHES on a Salmonella fimbrial shaft exhibited binding traits that resembled that of Salmonella rather than E. coli fimbriae. Apparently, the quaternary constraints imposed by the fimbrial shaft on the adhesin determine the distinct binding traits of S. typhimurium type 1 fimbriae.

Prevention of mucosal Escherichia coli infection by FimH-adhesin-based systemic vaccination

Virtually all uropathogenic strains of Escherichia coli, the primary cause of cystitis, assemble adhesive surface organelles called type 1 pili that contain the FimH adhesin. Sera from animals vaccinated with candidate FimH vaccines inhibited uropathogenic E. coli from binding to human bladder cells in vitro. Immunization with FimH reduced in vivo colonization of the bladder mucosa by more than 99 percent in a murine cystitis model, and immunoglobulin G to FimH was detected in urinary samples from protected mice. Furthermore, passive systemic administration of immune sera to FimH also resulted in reduced bladder colonization by uropathogenic E. coli. This approach may represent a means of preventing recurrent and acute infections of the urogenital mucosa.

Macrophage-T cell interaction in murine salmonellosis: selective down-regulation of ICAM-1 and B7 molecules in infected macrophages and its probable role in cell-mediated immunity

Vaccine development and understanding of cellular immune modulatory mechanisms in salmonella infections have been impeded due to the paucity of data on antigens capable of eliciting effective immune responses. The present study was done to evaluate the efficacy of five major purified salmonella antigens (porins, pili, flagella, outer membrane proteins and heat shock proteins) in modulating T cell-macrophage interactions which play a central role in resistance to and recovery from infection with several intracellular pathogens, including salmonella. The results showed that the T cells recovered 10 days post-immunization (D10 T cells) from mice immunized with porins and outer membrane proteins showed maximum proliferation in the presence of macrophages incubated with dead bacteria; however, this response was decreased when T cells were co-cultured with live Salmonella typhimurium-infected macrophages. Delayed-type hypersensitivity responses, as measured by increased footpad thickness at 24 h, though induced effectively by porins, pili and flagella, were completely abrogated when D10 T cells were pre-incubated with macrophages infected with live bacteria. The phagocytic and bactericidal ability of normal macrophages, when grown in presence of T cell supernatants, was not influenced by the immunizing agents, but T cell supernatants obtained from mice immunized with porins and heat-shock protein triggered increased bactericidal activity. Further, the expression of the co-stimulatory molecules ICAM-1 and B7 increased with increasing bacteria (dead):macrophage ratio, but this expression was down-regulated upon incubation with live bacteria.

Cable (cbl) type II pili of cystic fibrosis-associated Burkholderia (Pseudomonas) cepacia: nucleotide sequence of the cblA major subunit pilin gene and novel morphology of the assembled appendage fibers

Previous studies have shown that appendage pili of Burkholderia cepacia strains isolated from patients with cystic fibrosis (CF) at The Hospital for Sick Children, Toronto, Canada, mediate adherence to mucus glycoproteins and also enhance adherence to epithelial cells. The specific pilin-associated adhesin molecule is a 22-kDa protein. In the present study we purified the major subunit pilin (17 kDa) and immunolocalized it to peritrichously arranged pili. On the basis of their novel morphological appearance as giant intertwined fibers, we refer to them as cable (Cbl) pili. Using an oligonucleotide probe corresponding to regions of the N-terminal amino acid sequence of the pilin subunit, we detected the encoding cblA gene in a chromosomal DNA library. Sequencing revealed this structural gene to be 555 bp in length, encoding a leader sequence of 19 amino acids, a cleavage site between the alanine at position 19 and the valine at position 20, and a mature pilin sequence of 165 amino acids. The calculated molecular mass is 17.3 kDa. Hydrophobic plus apolar amino acids account for 60% of the total residues. The pilin exhibits some similarities in its amino acid sequence to colonization factor antigen I and CS1 fimbriae of Escherichia coli. With the cblA gene used as a probe, hybridization assays of 59 independent isolates, including those from several geographically separated CF centers, plus environmental and clinical (non-CF) strains, gave positive results with all of the 15 CF-associated B. cepacia isolates from Toronto, plus a single strain from one other CF center (Jackson, Mississippi). The cblA gene is the first pilin subunit gene of B. cepacia to be identified.

Type 1 fimbrial shafts of Escherichia coli and Klebsiella pneumoniae influence sugar-binding specificities of their FimH adhesins

The type 1 fimbriae of enterobacteria comprise FimA, which constitutes most of the fimbrial shaft, and a cassette of three minor ancillary subunits including FimH, the mannose-binding moiety. The sugar-binding specificities of Escherichia coli and Klebsiella pneumoniae type 1 fimbriae were examined by determining the relative activities of two aromatic mannosides in inhibiting the yeast aggregation caused by the fimbriated bacteria. 4-Methylumbelliferyl alpha-mannoside (MeUmb alpha Man) was approximately 10-fold more effective than p-nitrophenyl alpha-mannoside (p-NP alpha Man) in inhibiting the yeast aggregation caused by the recombinant expressing native E. coli type 1 fimbriae. In contrast, MeUmb alpha Man was only fourfold more effective than p-NP alpha Man in assays employing the recombinant expressing native K. pneumoniae type 1 fimbriae. In order to elucidate the molecular mechanisms underlying the sugar-binding specificities of type 1 fimbriae in the two species, transcomplementation studies were performed and resulted in the creation of recombinants expressing two types of hybrid fimbriae: one consisting of a cassette of minor subunits of E. coli fimbriae borne on a filamentous shaft of K. pneumoniae FimA subunits and the other consisting of a cassette of K. pneumoniae minor fimbrial subunits borne on a shaft of E. coli FimA subunits. Although the heterologous FimH was incorporated into the fimbrial filaments in amounts comparable to those observed in native fimbriae, the hemagglutination activities of recombinants expressing hybrid fimbriae were significantly lower than those of their counterparts bearing native fimbriae. The sugar-binding specificity of the recombinant expressing hybrid fimbriae consisting of an E. coli shaft bearing K. pneumoniae FimH was different from those of recombinants expressing native K. pneumoniae fimbriae in its affinity for the two aromatic sugars but was remarkably similar to the specificities exhibited by recombinants expressing native E. coli fimbriae. Conversely, the sugar-binding specificity of the recombinant expressing hybrid fimbriae consisting of a K. pneumoniae shaft bearing E. coli FimH was different from that of the recombinant expressing native E. coli fimbriae but was very similar to those of recombinants expressing native K. pneumoniae fimbriae. We conclude that the differences in the sugar-binding specificity between E. coli and K. pneumoniae FimH fimbrial subunits is influenced by the fimbrial shafts which carry the adhesin molecules in a functionally competent form at the distal tips.

Cell separations using targeted monoclonal antibodies against overproduced surface proteins

The capacity of polystyrene microspheres with immobilized antibodies against type 1 pili of E. coli was measured. Using pure IgG-type monoclonal antibodies obtained by affinity purification, it was found that, at high concentrations of antibody in solution, 2.6 +/- 0.4 mg of antibody immobilized/m2 of surface area. The binding of piliating E. coli cells on incubation with antibody-coated microspheres at various microsphere-to-cell number ratios ranging from 1-3750 was studied. It was found that a maximum of 290 +/- 50 cells were bound/microsphere, equivalent to a binding capacity of 2.9 +/- 0.7 x 10(10) cells/m2 of surface area.

FimH family of type 1 fimbrial adhesins: functional heterogeneity due to minor sequence variations among fimH genes

We recently reported that the type 1-fimbriated Escherichia coli strains CSH-50 and HB101(pPKL4), both K-12 derivatives, have different patterns of adhesion to yeast mannan, human plasma fibronectin, and fibronectin derivatives, suggesting functional heterogeneity of type 1 fimbriae. In this report, we provide evidence that this functional heterogeneity is due to variations in the fimH genes. We also investigated functional heterogeneity among clinical isolates and whether variation in fimH genes accounts for differences in receptor specificity. Twelve isolates obtained from human urine were tested for their ability to adhere to mannan, fibronectin, periodate-treated fibronectin, and a synthetic peptide copying the 30 amino-terminal residues of fibronectin. CSH-50 and HB101(pPKL4) were tested for comparison. Selected isolates were also tested for adhesion to purified fragments spanning the entire fibronectin molecule. Three distinct functional classes, designated M, MF, and MFP, were observed. The fimH genes were amplified by PCR from chromosomal DNA obtained from representative strains and expressed in a delta fim strain (AAEC191A) transformed with a recombinant plasmid containing the entire fim gene cluster but with a translational stop-linker inserted into the fimH gene (pPKL114). Cloned fimH genes conferred on AAEC191A(pPKL114) receptor specificities mimicking those of the parent strains from which the fimH genes were obtained, demonstrating that the FimH subunits are responsible for the functional heterogeneity. Representative fimH genes were sequenced, and the deduced amino acid sequences were compared with the previously published FimH sequence. Allelic variants exhibiting >98% homology and encoding proteins differing by as little as a single amino acid substitution confer distinct adhesive phenotypes. This unexpected adhesive diversity within the FimH family broadens the scope of potential receptors for enterobacterial adhesion and may lead to a fundamental change in our understanding of the role(s) that type 1 fimbriae may play in enterobacterial ecology or pathogenesis.

T-cell-independent stimulation of immunoglobulin secretion in resting human B lymphocytes by the mannose-specific adhesin of Escherichia coli type 1 fimbriae

Purified Escherichia coli type 1 fimbriae have been shown previously to stimulate T-cell-independent proliferation of human B lymphocytes. The response is mediated by the mannose-specific, lectin-like adhesin protein FimH. Here we show that type 1 fimbriae also stimulate immunoglobulin (Ig) secretion by B cells. The response was maximal at three days of culture and consisted predominantly of the IgM isotype. It was independent of serum components, T lymphocytes, monocytes, and natural killer cells. Highly purified resting B cells were induced to proliferate and secrete Ig in response to the fimbriae. The role of FimH in the response was shown by the failure of FimH- type 1 fimbriae to stimulate and by inhibition of the response with alpha-methyl mannoside. In light of the fact that carbohydrate-binding adhesins have been found on a wide variety of microorganisms, these studies suggest the possibility that responses of other cell types to other microbial adhesins will be discovered.

Functional heterogeneity of type 1 fimbriae of Escherichia coli

Escherichia coli and other members of the family Enterobacteriaceae express surface fibrillar structures, fimbriae, that promote bacterial adhesion to host receptors. Type 1 fimbriae possess a lectinlike component, FimH, that is commonly thought to cause binding to mannose-containing oligosaccharides of host receptors. Since adhesion of type 1 fimbriated organisms are inhibited by mannose, the reactions are described as mannose sensitive (MS). We have studied the adhesion of the type 1 fimbriated CSH-50 strain of E. coli (which expresses only type 1 fimbriae) to fibronectin (FN). E. coli CSH-50 does not bind detectable amounts of soluble FN but adheres well to immobilized plasma or cellular FN. This adhesion was inhibited by mannose-containing saccharides. By using purified domains of FN, it was found that E. coli CSH-50 adheres primarily to the amino-terminal and gelatin-binding domains, only one of which is glycosylated, in an MS fashion. Binding of the mannose-specific lectin concanavalin A to FN and ovalbumin was eliminated or reduced, respectively, by incubation with periodate or endoglycosidase. Adhesion of E. coli CSH-50 to ovalbumin was reduced by these treatments, but adhesion to FN was unaffected. E. coli CSH-50 also adheres to a synthetic peptide copying a portion of the amino-terminal FN domain (FNsp1) in an MS fashion. Purified CSH-50 fimbriae bound to immobilized FN and FNsp1 in an MS fashion and inhibited adhesion of intact organisms. However, fimbriae purified from HB101 (pPKL4), a recombinant strain harboring the entire type 1 fim gene locus and expressing functional type 1 fimbriae, neither bound to FN or FNsp1 nor inhibited E. coli adhesion to immobilized FN or FNsp1. These novel findings suggest that there are two forms of type 1 MS fimbriae. One form exhibits only the well-known MS lectinlike activity that requires a substratum of mannose-containing glycoproteins. The other form exhibits not only the MS lectinlike activity but also binds to nonglycosylated regions of proteins in an MS manner.

New enzyme immunoassays for specific assay and general detection of Trypanosoma cruzi, epimastigotes

A highly specific competitive enzyme-linked immunosorbent assay for the epimastigote of Tulahuen strain was developed by using the usual 3 immunological reagents, a rabbit antiserum specific for T. cruzi, epimastigote of Tulahuen strain, beta-D-galactosidase-labeled goat anti-rabbit immunoglobulin G and the solid-phase cell fragments of the epimastigote of Tulahuen strain. A new method, the selected antibody enzyme immunoassay (SAEIA) which generally detected all strains of the epimastigote tested with the same working range, was developed by changing only the solid-phase antigen to the epimastigote of Y strain among the 3 immunological reagents. Both assays permitted us to measure accurately as little as 1,000 parasites per assay tube. Scope of the SAEIA was limited to the epimastigote. Both life-cycle forms of T. cruzi which appear in mammals, amastigote and trypomastigote, and other kinetoplastids showed low cross-reaction values by the assay. The assay principle of the new method and a preliminary study to apply the SAEIA for finding the field T. cruzi-infected insect vectors were also reported.

Type 1 fimbriation and fimE mutants of Escherichia coli K-12

We reexamined the influence of fimE, also referred to as hyp, on type 1 fimbriation in Escherichia coli K-12. We found that one strain used previously and extensively in the analysis of type 1 fimbriation, strain CSH50, is in fact a fimE mutant; the fimE gene of CSH50 contains a copy of the insertion sequence IS1. Using a recently described allelic exchange procedure, we transferred the fimE::IS1 allele from CSH50 to our present wild-type strain, MG1655. Characterization of this IS1-containing strain (AAEC137), together with another fimE mutant of MG1655 (AAEC143), led to two conclusions about the role of fimE. First, the formation of phase variant colony types, reported widely in strains of E. coli, depends on mutation of fimE, at least in K-12 strain MG1655. Here we showed that this phenomenon reflects the ability of fimE to stimulate the rapid inversion of the fim invertible element from on to off when the bacteria are grown on agar. Second, our analysis of fimE mutants, which is limited to chromosomal constructs, provided no evidence that they are hyperfimbriate. We believe that these results, which are at odds with a previous study using fim-containing multicopy plasmids, reflect differences in gene copy number.

Fragmentation of Escherichia coli type 1 fimbriae exposes cryptic D-mannose-binding sites

Cells of the gram-negative bacterium Escherichia coli are able to attach to various host cells by means of a mannose-specific adhesin associated with type 1 fimbriae. Here we show that fragmentation of type 1 fimbriae by freezing and thawing results in increased mannose-binding activity as demonstrated by increased hemagglutination, increased stimulation of human lymphocyte proliferation, and increased binding of the mannose-containing enzyme horseradish peroxidase. Increased activity in all three assays was mannose sensitive and was not exhibited by FimH- mutant type 1 fimbriae lacking the adhesin. Scatchard analysis of the data from peroxidase binding assays showed that unfrozen and frozen fimbriae contain binding sites displaying two classes of affinity. Frozen and thawed fimbriae expressed an increase in the number of high-affinity binding sites. These results show that fragmentation of the fimbrial structure exposes cryptic mannose-binding activity associated with type 1 fimbriae, presumably that of internally located adhesin molecules. Our data support earlier observations that adhesin moieties of type 1 fimbriae are located both at the tips and at intervals along the length of the fimbriae. In addition, our data suggest that only the adhesin moieties that are located at the fimbrial tips are functional in binding mannose. Adhesins located along the length of the fimbriae have their mannose-binding activity buried within the fimbrial structure and hence are not functional. We propose an updated model for the structure of type 1 fimbriae that is in agreement with the above observations.

Allelic exchange in Escherichia coli using the Bacillus subtilis sacB gene and a temperature-sensitive pSC101 replicon

To facilitate efficient allelic exchange of genetic information into a wild-type strain background, we improved upon and merged approaches using a temperature-sensitive plasmid and a counter-selectable marker in the chromosome. We first constructed intermediate strains of Escherichia coli K12 in which we replaced wild-type chromosomal sequences, at either the fimB-A or lacZ-A loci, with a newly constituted DNA cassette. The cassette consists of the sacB gene from Bacillus subtilis and the neomycin (kanamycin) resistance gene of Tn5, but, unlike another similar cassette, it lacks IS1 sequences. We found that sucrose sensitivity was highly dependent on incubation temperature and sodium chloride concentration. The DNA to be exchanged into the chromosome was first cloned into derivatives of plasmid pMAK705, a temperature-sensitive pSC101 replicon. The exchanges were carried out in two steps, first selecting for plasmid integration by standard techniques. In the second step, we grew the plasmid integrates under non-selective conditions at 42 degrees C, and then in the presence of sucrose at 30 degrees C, allowing positive selection for both plasmid excision and curing. Despite marked locus-specific strain differences in sucrose sensitivity and in the growth retardation due to the integrated plasmids, the protocol permitted highly efficient exchange of cloned DNA into either the fim or lac chromosomal loci. This procedure should allow the exchange of any DNA segment, in addition to the original or mutant allelic DNA, into any non-essential parts of the E. coli chromosome.

Structure-function analysis of the K88ab fimbrial subunit protein from porcine enterotoxigenic Escherichia coli

Several in-frame linker insertions have been made in various positions in the faeG gene encoding the K88ab fimbrial subunit protein from porcine enterotoxigenic Escherichia coli. The effects of the linker insertions have been investigated with regard to the ability of the mutated fimbrial subunits to be exported to the surface of the bacterial cell and assembled into a fimbrial structure. The structure/function relationship of the subunit protein is discussed in the light of the phenotypes of the mutations constructed, secondary structure predictions, and hydrophilicity plots.

Adherence and pathogenesis of Salmonella enteritidis in mice

Adherence of many pathogenic organisms to the host cells has been associated with the presence of fimbriae. The exact role of these organelles in the adherence and pathogenesis of Salmonella enteritidis is not well established. Utilizing hemagglutination tests, S. enteritidis was shown to possess type 1 and type 3 fimbriae. Polyacrylamide gel electrophoresis of the isolated fimbriae showed that type 1 and 3 fimbriae of S. enteritidis had subunit M.r of 17 and 22 kDa, respectively. In vitro adherence assays suggested that S. enteritidis utilized type 1 fimbriae to adhere to human buccal and mouse small intestine epithelial cells. In addition, antibody produced against type 1 and type 3 fimbriae protected the mice from infection with a lethal dose of S. enteritidis. These results suggest that type 1 and possibly type 3 fimbriae are involved in the adherence and pathogenesis of S. enteritidis. The data further suggest that they may have a role in the adherence and pathogenesis of the other enteric organisms.

Role of the putative "link" glycopeptide of intestinal mucin in binding of piliated Escherichia coli serotype O157:H7 strain CL-49

Purified rat intestinal mucin was used to identify mucin-binding sites for type 1-piliated Escherichia coli O157:H7 strain CL-49 isolated from a patient with hemorrhagic colitis and hemolytic uremic syndrome. Optimum binding of bacteria in a microtiter binding assay occurred with a mucin coating concentration of 15 micrograms (protein)/150 microliters. In hapten inhibition studies, several nonmucin glycoproteins bearing exposed mannosyl residues in N-linked oligosaccharides were effective inhibitors, as was rat mucin. The same glycoproteins caused bacterial aggregation. High-molecular-mass glycoproteins of the mucin were separated from its 118-kilodalton "link" glycopeptide fraction, and the latter was shown to be the mucin-binding component for E. coli CL-49 and its purified type 1 pili. This was confirmed in hemagglutination inhibition studies. Treatment of the link glycopeptide with jack bean alpha-mannosidase or endo-beta-N-acetylglucosaminidase H destroyed bacterial binding activity. Chemical or enzymatic modifications of intact rat mucin were undertaken to evaluate the normal accessibility of the link glycopeptide receptors to E. coli CL-49. Deglycosylation with trifluoromethane-sulfonic acid abolished binding, whereas pronase digestion had no effect. Reduction and alkylation as well as lipid extraction enhanced bacterial binding by the mucin, presumably by causing greater exposure of receptor sites. In summary, our binding studies revealed, for the first time, that intestinal mucin bears oligomannosyl receptors for type 1 pili and that these receptors are located on N-linked oligosaccharides of the 118-kilodalton link glycopeptide region of the mucin. Our experiments suggest the receptors are normally partly "covered" by noncovalently bound lipid. In addition, release of the link component from the rest of the mucin by disulfide bond reduction causes greater exposure of specific bacterium-binding sites.

Characteristics of binding of Escherichia coli serotype O157:H7 strain CL-49 to purified intestinal mucin

Purified rat intestinal mucin was used as a model mucin to study the binding of Escherichia coli serotype O157:H7, a human pathogen associated with outbreaks of hemorrhagic colitis and hemolytic uremic syndrome. Of six O157:H7 strains, only one strain (designated CL-49) bound to rat (and other) intestinal mucins by a specific and saturable process. Binding was observed only after the bacteria were serially passaged to promote the expression of type 1 pili (fimbriae). Several other type 1-piliated E. coli strains, however, did not bind to mucin. Binding of E. coli CL-49 was inhibited by D-mannose and short oligomannosyl derivatives, particularly Man-alpha-1,3-Man, Man-alpha-1,2-Man, and Man-alpha-1,3-Man-beta-1,4-N-acetylglucosamine. Other inhibitors of binding included p-nitrophenol (10(-4) M), heating at 60 degrees C (to remove pili), an antibody to type 1 pili, and purified type 1 pili of E. coli CL-49 used as hapten inhibitors. A comparison of the hydrophobicity of piliated E. coli CL-49 with other type 1-piliated E. coli strains indicated that the former strain was much more hydrophobic than the others. These findings indicate that highly purified intestinal mucins possess specific mannosyl receptor sites for bacterial type 1 pili on E. coli CL-49, but that strong hydrophobic interactions between the mucin and the pili stabilize the mannose-dependent binding process. We speculate that the mucin receptors for type 1 pili reside in oligosaccharides of the 118-kilodalton "link" glycopeptide, since this is the only mucin component known to contain mannose.

Polyclonal anti-idiotypic antibodies exhibit antigenic mimicry of limited type 1 fimbrial proteins of Escherichia coli

Polyclonal anti-idiotypic antibodies (anti-Ids)(fim) developed against idiotypes on antibodies (Ab-1s) that specifically bind structural, organelle fimbrial proteins of Escherichia coli were able to modulate immune function in anti-Id(fim)-immunized mice. Proliferation or suppression of splenic lymphoid cell responses by polyclonal anti-Ids in tissue culture appeared to be dose dependent. Anti-Ids were able to induce a dose-dependent T-cell-mediated immunity specific for type 1 fimbrial antigen(s) in immunized animals when assessed in vitro, but they failed to elicit in vivo positive ear-swelling skin reactions. Anti-Ids were unable to induce protective immunity against an in vivo infectious challenge with E. coli in anti-Id-immunized adult animals, but they stimulated a specific, secondary antibody response in anti-Id-challenged mice. Anti-Ids stimulated the development of anti-anti-Ids (Ab-3s) specifically binding a fimbrial antigen(s) and revealed the presence of antibody idiotypes binding E. coli adhesin proteins in the 27- to 29-kilodalton range. Results suggest discrete, but subtle, immunomodulatory effects of the anti-Ids and potential vaccinoid properties capable of stimulating a specific humoral and cellular response in vivo.

A novel enzyme immunoassay for conidia of Fusarium oxysporum f.sp. cucumerinum F504

This study was undertaken to develop a new tool to study fusarial diseases of plants. Micro- and macro-conidia of a strain (F504) of Fusarium oxysporum were isolated and antiserum against the conidia was elicited in rabbits. A highly specific and sensitive competitive-type enzyme-linked immunosorbent assay (ELISA) for conidia of the strain was developed using the antiserum with beta-D-galactosidase-labeled anti-rabbit IgG as the secondary antibody and conidia fragments of the strain as antigen attached to Amino-Dylark solid-phase balls. The assay was highly specific to conidia of the strain F504, while conidia-free hypha of the strain F504 as well as all other microorganisms tested including nine other strains of Fusarium species showed little cross-reactivity. Application of the ELISA to following the growth rates of conidia in hyphae of the strain F504 under several conditions are also reported.

Influence of fluoroquinolones on expression and function of P fimbriae in uropathogenic Escherichia coli

P fimbriae are the major adhesins mediating attachment of pyelonephritogenic Escherichia coli to urinary tract tissues, and they therefore constitute a recognized virulence factor. In this work, the effect of fluoroquinolones on P fimbria expression and function in E. coli SS142 and C1212 was assessed. Ciprofloxacin, fleroxacin, and norfloxacin were compared with their precursor nalidixic acid and with trimethoprim in sublethal concentrations ranging from 1/32 to 1/4 of the MIC. Fimbria function was assessed in a standard hemagglutination assay and in a parallel hemagglutination inhibition assay in which the tier of antifimbrial antiserum necessary to inhibit hemagglutination by SS142 was determined. Adhesion of antibiotic-exposed bacteria to human uroma T24 cells in suspension was also measured. Fimbria production was quantitated in an inhibition enzyme-linked immunosorbent assay. Trimethoprim produced a dose-dependent decrease of three to four hemagglutination titers for both strains and a decline in the antiserum titer from 1:16 (control) to 1:128 (1/4 MIC) for E. coli SS142. Adherence exhibited similar decrements from 130 +/- 28 (control) to 16 +/- 3 (1/4 MIC) and from 83 +/- 19 (control) to 30 +/- 11 (1/4 MIC) E. coli cells per uroepithelial cell (mean +/- standard error) for SS142 and C1212, respectively (P less than 0.015). By enzyme-linked immunosorbent assay, the inhibition following exposure decreased in a dose-dependent manner from 31% (control) to 8% (1/4 MIC). By contrast, none of the quinolones produced significant changes in the parameters assessed above. At sublethal concentrations, trimethoprim decreased fimbria production. Following exposure to fluoroquinolones, however, E. coli expressed morphologically and functionally intact P fimbriae.

Serological response to P-fimbriae of Escherichia coli in patients with urinary tract infections

The antibody response to P-fimbriae of Escherichia coli in patients with upper urinary tract infections was investigated. In the sera of patients with pyelonephritis obtained at the initial visit to hospital (3 to 7 days after the onset of symptoms), a high incidence of antibodies to P-fimbriae was detected (12 out of 14 patients). P-fimbriated Escherichia coli strains were isolated from urine samples in all of these antibody-positive patients. Antibodies detected by ELISA using purified antigen were essentially IgG and specifically recognized P-fimbriae. These antibodies inhibited completely, or in some cases partially, mannose-resistant hemagglutination with P-fimbriated Escherichia coli.

Transport of nutrients into the renal brush border membrane vesicles as marker in evaluating the role of antipili antibodies in modulation of ascending pyelonephritis in rats

The uptake of D-glucose, L-aspartate, L-lysine and L-proline was investigated in renal brush border membrane (BBM) vesicles prepared from control, infected or passively-immunized-infected rats. Except L-aspartate, a progressive decrease in the uptake of these nutrients in both infected and immunized-infected groups during the course of infection was observed, but the changes were less apparent in immunized-infected rats than in non-immunized ones. The uptake of L-aspartate was increased in vesicles from early stages of infection but decreased in those from later stages. Also in L-aspartate uptake, the changes were smaller in immunized animals. The uptake of nutrients was detectable earlier than were histopathological alterations of both kidneys. The observations demonstrated that uptake of D-glucose and amino acids in the kidneys is disturbed prior to appearance of histopathological lesions and thus can be used for early detection of the disease. The data also demonstrate that antipili antibodies afford partial protection against ascending pyelonephritis.

Conservation of the D-mannose-adhesion protein among type 1 fimbriated members of the family Enterobacteriaceae

A variety of genera and species of the family Enterobacteriaceae bear surface fimbriae that enable them to bind to D-mannose residues on eukaryotic cells. Until recently, it was thought that the D-mannose binding site was located in the major structural subunit (FimA), of relative molecular mass (Mr) 17,000 (17 K), of these organelles in Escherichia coli. New evidence indicates that this binding site resides instead in a minor protein Mr 28-31 K (FimH) located at the tips and at long intervals along the length of the fimbriae, and is reminiscent of the minor tip adhesion proteins of pyelonephritis-associated pili (Pap) and S fimbriae. In contrast to the antigenic heterogeneity of the major FimA subunit, the antigenic structure of FimH is conserved among different strains of E. coli. Here, we report an even broader conservation of this minor adhesion protein extending to other genera and species of type 1 fimbriated Enterobacteriaceae. Our results may have implications for the development of broadly protective vaccines against Gram-negative bacillary infections in animals and perhaps in man.

Hyperadhesive mutant of type 1-fimbriated Escherichia coli associated with formation of FimH organelles (fimbriosomes)

The relationships of the genes and gene-products mediating D-mannose-specific attachment of type 1 fimbriae of Escherichia coli to eucaryotic cells were investigated by deletion mutation analysis of recombinant plasmid pSH2, which carries the genetic information for the synthesis and expression of functional type 1 fimbriae. Mutant pUT2004 was derived by a deletion remote from the structural gene encoding the 17-kilodalton (kDa) subunit protein of type 1 fimbriae. Phenotypically, the mutant demonstrated an eightfold-higher mannose-specific hemagglutination titer than the parent strain. On electron microscopy, the mutant strain expressed the same number of fimbriae as the parent strain. However, numerous 10-nm-diameter rounded structures (fimbriosomes) were observed both closely associated with fimbriae and in the culture medium. Fimbriosomes isolated from the medium agglutinated guinea pig erythrocytes in a mannose-sensitive manner. Dissociation of the fimbriosomes yielded a single 29-kDa protein, as demonstrated by sodium dodecyl sulfate gel electrophoresis. Antibodies raised against fimbriosomes reacted with a 29-kDa protein on immunoelectroblots of dissociated type 1 fimbriae and also blocked the adherence of other strains of type 1 fimbriated E. coli to eucaryotic cells. These findings suggest that the enhanced adhesive properties of the mutant pUT2004 strain are associated with overproduction of the 29-kDa FimH in the form of fimbriosomes which contain the determinant of the D-mannose-sensitive adhesion of type 1 fimbriae.

Identification of two ancillary subunits of Escherichia coli type 1 fimbriae by using antibodies against synthetic oligopeptides of fim gene products

We have chemically synthesized oligopeptides corresponding to the NH2-terminal stretch of two gene products, designated FimG and FimH, of the fim gene cluster of Escherichia coli. These synthetic peptides, designated S-T1FimG(1-16) and S-T1FimH(1-25)C, evoked antibodies in rabbits that reacted with 14- and 29-kilodalton subunits, respectively, of dissociated fimbriae encoded by the recombinant plasmid pSH2 carrying the genetic information for the synthesis and expression of functional type 1 fimbriae. Neither of these fimbrial proteins was detected in dissociated fimbrial preparations from nonadhesive E. coli cells carrying the mutant plasmid pUT2002, containing a restriction site-specific deletion of fimG and fimH. Anti-S-T1FimH(1-25)C inhibited the adherence of type 1 fimbriated E. coli to epithelial cells. Immunoelectron microscopy revealed that anti-S-T1FimH(1-25)C, but not anti-S-T1FimG(1-16), bound to intact type 1 fimbriae of E. coli at the fimbrial tips and at long intervals along the fimbrial filaments. Anti-S-T1FimG(1-16) appeared to be directed at epitopes not accessible on the intact fimbriae and consequently failed to bind to intact fimbriae or to block fimbrial attachment. Our results suggest that the fimG and fimH gene products are components of type 1 fimbriae and that FimH may be the tip adhesin mediating the binding of type 1 fimbriated E. coli to D-mannose residues on mucosal surfaces.

A novel enzyme immunoassay commonly applied for ten strains of Pyricularia oryzae

Antiserum against a strain of the rice blast fungus Pyricularia oryzae was elicited in rabbits immunized with its cell fragments emulsified with incomplete Freund's adjuvant. The fragments were also used as solid-phase antigens. A highly sensitive, competitive type enzyme-linked immunosorbent assay for P. oryzae was developed by using these two preparations as the immune reagents together with the use of beta-D-galactosidase-labeled anti-rabbit IgG as the tracer. Cross-reactivity of nine different strains of P. oryzae were measured by the assay. Sensitivity and accuracy of the assay was improved by choosing the cell fragments of the least cross-reactive strain as the solid-phase antigen. The improved method was successfully applied for sensitive and accurate assay of all ten strains of P. oryzae with the common measuring range between 1 and 100 ng per tube. Other species of microorganisms had little reactivity in this immunoassay indicating that the assay is specific to P. oryzae group microorganisms.

Assembly of a chemically synthesized peptide of Escherichia coli type 1 fimbriae into fimbria-like antigenic structures

Escherichia coli type 1 fimbriae are composed of subunits, each of which comprises 158 amino acids. We synthesized a copy of a 13-residue peptide, located near the NH2 terminus of the fimbrial subunit, that assumed some of the properties of type 1 fimbriae. At pH 5.5 the synthetic peptide autoassembled into fibrillar structures that resembled type 1 fimbriae except that they appeared less rigid and rodlike. A quaternary structure-specific monoclonal antibody against type 1 fimbriae recognized the synthetic peptide in the assembled but not the unassembled state. Furthermore, when the synthetic peptide was injected in its fimbrial conformation into rabbits, it evoked antibodies that reacted with type 1 fimbriae isolated from E. coli.

Use of monoclonal antibodies to probe subunit- and polymer-specific epitopes of 987P fimbriae of Escherichia coli

The relationship between the structure and biological function of 987P fimbriae of a strain of enterotoxigenic Escherichia coli (O9:K103:H-) from piglets was investigated. A set of four monoclonal antibodies was prepared from the spleen cells of mice immunized with isolated 987P fimbriae. Antibodies E11, D5, and C3, but not G10, reacted in enzyme-linked immunosorbent assays with 987P fimbriae-bearing E. coli. Electron microscopy showed that E11 and D5 reacted in a discrete periodic pattern forming a spiral motif along the length of the fimbriae. The results of enzyme-linked immunosorbent assays were in agreement with these results; antibodies E11 and D5 reacted at a high dilution (1:12,000) with native fimbriae on the surface of E. coli, whereas antibody C3 reacted at an intermediate dilution (1:3,000) and G10 failed to react at all (less than 1:250). In contrast, C3 and G10 reacted at a dilution of 1:3,276,000 with the fimbrial subunits derived by treating the isolated fimbriae with 6 M guanidine hydrochloride, whereas E11 and D5 reacted with the subunits at much lower dilutions of 1:800 and 1:6,400, respectively. Moreover, fimbriae reassembled from the subunits regained reactivity with antibodies D5 and E11, indicating that these antibodies are directed against quaternary conformational epitopes. Only the three antibodies (D5, E11, and C3) that recognized epitopes accessible on intact fimbriae were able to efficiently block the adhesion of 987P fimbriated E. coli to piglet enterocytes. These results indicate that certain epitopes of 987P fimbriae are dependent on quaternary structural conformation, whereas others are present on monomeric subunits; some of the latter appear to remain accessible on fully assembled fimbriae.

Characterization of genes encoding type 1 fimbriae of Klebsiella pneumoniae, Salmonella typhimurium, and Serratia marcescens

With a minicell system, the organization of genes encoding type 1 fimbriae of Salmonella typhimurium, Klebsiella pneumoniae, and Serratia marcescens was determined. In all cases multiple gene products were necessary for the phenotypic expression of fimbriae; thus fimbrial expression in these strains is similar to that in Escherichia coli. The type 1 fimbrial subunit gene was detected by the ability of its product to react with specific antiserum. At least six genes were found to be involved in the expression of type 1 fimbriae by S. typhimurium, and at least four genes constituted the fimbrial gene cluster of K. pneumoniae. In the case of S. marcescens, a minimum of three detectable polypeptides was required for the production of fimbriae. Also, a gene probe consisting in part of nucleotide sequences from the E. coli fimbrial subunit gene hybridized to a discrete DNA fragment derived from the plasmid encoding K. pneumoniae fimbriae. Such a fragment was assumed to contain a gene encoding the structural component of the type 1 fimbriae. Each of the three cloned systems encoded a number of polypeptides which varied in size; thus, the organization and molecular weight of fimbrial accessory proteins of each genus were not identical.

Immunoelectron microscopic analysis of elongation of type 1 fimbriae in Escherichia coli

Using 10- and 20-nm-diameter gold particles conjugated to an antifimbrial monoclonal antibody, we analyzed the location of assembly of newly formed subunits on growing type 1 fimbriae of Escherichia coli. Fimbriae were removed from an E. coli K-12-derived strain, CSH50, by blending. Blended cells were allowed to regenerate their fimbriae in growth medium for approximately 25 min, after which they were labeled with a 20-nm-gold-monoclonal antibody probe. Continued outgrowth of these labeled fimbriae was allowed for additional time intervals, after which they were labeled with a 10-nm-gold-monoclonal antibody probe. The resulting fimbriae, double labeled with 10- and 20-nm-diameter gold particles, were examined in an electron microscope. The pattern of labeling on individual fimbrial organelles indicated morphologically that newly synthesized subunits are added to a growing organelle at its base.

Interaction of a 60-kilodalton D-mannose-containing salivary glycoprotein with type 1 fimbriae of Escherichia coli

A 60-kilodalton glycoprotein previously isolated and purified from human saliva (J. B. Babu, E. H. Beachey, D. L. Hasty, and W. A. Simpson, Infect. Immun. 51: 405-413, 1986) was found to interact with type 1 fimbriae and prevent adhesion of type 1 fimbriated Escherichia coli to animal cells in a D-mannose-sensitive manner. Purified salivary glycoprotein agglutinated type 1 fimbriated E. coli and, at subagglutinating concentrations, blocked the ability of type 1 fimbriated E. coli to attach to human buccal epithelial cells or agglutinate guinea pig erythrocytes. Both interactions were inhibited by alpha-methyl-D-mannoside but not by alpha-methyl-D-glucoside. Complexing of the glycoprotein to type 1 fimbriae was demonstrated by molecular sieve chromatography and modified Western blots. When mixed with type 1 fimbriae, the radiolabeled salivary glycoprotein coeluted with type 1 fimbriae from a column of Sepharose 4B. When blotted from a sodium dodecyl sulfate gel to nitrocellulose sheets, the glycoprotein interacted directly with type 1 fimbriae applied to the blots. Both of the latter interactions also were blocked by alpha-methyl-D-mannoside but not by alpha-methyl-D-glucoside. Chemical modification of the glycoprotein with sodium metaperiodate abolished its ability to interact with isolated type 1 fimbriae or type 1 fimbriated E. coli. These results suggest that the carbohydrate moiety of the 60-kilodalton glycoprotein serves as a receptor for type 1 fimbriae in the oral cavity, and we postulate that the interaction may cause agglutination and early removal of E. coli, thereby preventing colonization by these organisms of oropharyngeal mucosae and dental tissues.

Utilization of anion-exchange chromatography and monoclonal antibodies to characterize multiple pilus types on a uropathogenic Escherichia coli O6 isolate

Multiple pilus types from a uropathogenic strain of Escherichia coli O6, strain 6260, were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), high-pressure liquid chromatography, binding assays, and erythrocyte adsorption. In addition, monoclonal antibodies were raised against purified pili of E. coli 6260 and used for immunological characterization. SDS-PAGE analysis of the purified pili showed at least three different subunits with molecular weights of 15,700, 17,800, and 19,300. SDS-PAGE analysis of four protein peaks from anion-exchange chromatography of intact pili showed polypeptides with molecular weights of 19,300 (fraction 1), 15,700 (fraction 2), and 17,800 and 15,700 (both fractions 3 and 4). Erythrocyte adsorption of the whole-pilus preparation removed the 17,800-molecular-weight subunit (17.8K subunit) and reduced the 15.7K subunit. Pili from an isogenic hemagglutination-negative variant of E. coli 6260, showing only the 15.7K and 19.3K subunits by SDS-PAGE, lacked the 17.8K subunit of fractions 3 and 4 present in the parent high-pressure liquid chromatography profile. Our data suggest that two of the pilus subunits, the 15.7K and 17.8K subunits, mediate mannose-resistant agglutination of human erythrocytes. Pili in fractions 1 and 2 from the parent strain bound specifically to mannose residues, while pili in fraction 4 bound to P-coated horse erythrocytes; no receptor specificity was identified for pili in fraction 3. Immunological analysis by the immunoblot technique showed that monoclonal antibody 11-2 reacted with the 19.3K subunit, monoclonal antibodies 34-3 and 73-3 reacted with the 15.7K subunit, and monoclonal antibodies 81-1, 82-1, and 91-1 reacted with polymers of subunits retained in the stacking gel. Intact pili precipitated by any of the six monoclonal antibodies showed two polypeptides by SDS-PAGE: 15.7K and 19.3K polypeptides for monoclonal antibody 11-2, and 15.7K and 17.8K polypeptides for monoclonal antibodies 34-3, 73-3, 81-1, 82-1, and 91-1. The cross-reactivity of the monoclonal antibodies with purified pili from other E. coli strains was determined by enzyme-linked immunosorbent assay. Monoclonal antibody 11-2 showed no significant cross-reactivity with heterogeneous pili. In contrast, the other monoclonal antibodies showed equivalent or greater reactivity with P pili from heterologous strains as compared with reactivity with E. coli 6260 pili.(ABSTRACT TRUNCATED AT 400 WORDS)

Monoclonal antibodies that recognize the P fimbriae F71, F72, F9, and F11 from uropathogenic Escherichia coli

The Escherichia coli P fimbriae F71, F72, F9, and F11 from four cloned strains were purified, and polyclonal antisera were raised in rabbits. Cross-reactions of these antisera with eight different cloned and purified fimbriae were measured in an enzyme-linked immunosorbent assay. These antisera showed a reaction with the homologous fimbriae and also with most heterologous fimbriae. Monoclonal antibodies (MAbs) directed against the same four native fimbriae were produced by the fusion of spleen cells from immunized BALB/c mice with SP2/0 myeloma cells. The resulting four series of MAbs were also screened in an enzyme-linked immunosorbent assay with eight different cloned and purified fimbriae. Four different F71 hybridomas produced MAbs which recognized only epitopes on F71 fimbriae. Two F72 MAbs recognized epitopes on F72 and F9 fimbriae, whereas another F72 MAb recognized an epitope on only F72 fimbriae. Three MAbs raised against F9 reacted only with epitopes on F9 fimbriae. Six MAbs against F11 fimbriae could be divided into two groups: on the one hand two MAbs recognizing F11, pyelonephritis-associated pilus, Pap, and F72 fimbriae and on the other hand four MAbs recognizing F11 and "Clegg" fimbriae. None of the MAbs reacted with 1A or 1C fimbriae. In a hemagglutination inhibition assay it was shown that none of the MAbs produced inhibited the adhesive properties of homologous cloned strains.

Immunochemical characterization of P pili from invasive Escherichia coli

P pili (or fimbriae) are present on most pyelonephritogenic Escherichia coli strains, and they mediate binding to erythrocytes and epithelial cells. To determine the antigenic diversity of P pili, we purified the pili from 14 bacteremic E. coli strains which caused mannose-resistant hemagglutination. Pilus preparations consisted of one to three bands in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and ranged in molecular weight from 14,000 to 19,500. There was no single band common to all the strains. An enzyme-linked immunosorbent inhibition assay detected 20 ng of pilus antigen. When four different rabbit antisera were used, only two or fewer heterologous strains could inhibit the enzyme-linked immunosorbent assay. Immunoblots yielded the same results. Protein sequences of four P pili had identical N termini. These results show that despite having identical amino-terminal sequences, P pili are antigenically heterogeneous. The receptor-binding domains which are likely to be identical in all strains must be immunorecessive.

Structural and antigenic analysis of meningococcal piliation

Pilin with an Mr of 16,500 was purified to homogeneity from Neisseria meningitidis SP3428. Procedures which provided useful separation during purification included high-pressure liquid chromatography with a TSK size exclusion column, Sephacryl S-200 column chromatography, ion-exchange chromatography with SP-Sephadex, and preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The amino acid composition of this pilin was similar to that previously reported for this species. The sequence of N-terminal 51 amino acids was also determined. The protein lacked a modified phenylalanine at the amino terminus and displayed six residues which were different from Neisseria gonorrhoeae in that region of the molecule determined to be the lectin-binding domain. Monoclonal antibody raised to this pilin was employed, along with a monoclonal antibody to an epitope common to all gonococcal pilins, to analyze the intra- and interstrain heterogeneity of meningococcal piliation. The results indicate that N. meningitidis displays considerable intra- and interstrain heterogeneity with respect to both pilus subunit size and antigenicity. The Mr of subunits ranged from 13,000 to 20,000.

Mannose-specific and hydrophobic interaction between Escherichia coli and polymorphonuclear leukocytes--influence of bacterial culture period

The influence of culture period on mannose-specific and hydrophobic properties of the bacterial surface and on bacteria/polymorphonuclear leukocyte (PMNL) interaction was studied. Four E. coli strains, PN7 (01:K1), ABU2 (ON:K14), CU9 (06:K14) and CU13 (08:KN) and two Salmonella typhimurium strains 395 MR10 and 395 MS, well characterized according to physicochemical surface properties, presence of type 1 fimbriae and interaction with PMNL, were used in the study. The results show that with prolonged culture period, the liability to hydrophobic interaction increases, the agglutination-strength of mannose-specific maltobionamide liposomes increases, while the agglutination-titer with guinea-pig erythrocytes remains constant. Furthermore, the mannose-specific association with and metabolic activation of PMNL is augmented, while the ingestion is unchanged. In addition, our results demonstrate differences in sensitivity between the methods used to detect exposure of mannose-specific structures on the surface of bacteria, and that the culture condition is important for bacterial surface properties. It thus appears that the culture conditions have a great influence on the surface properties of E. coli bacteria and the interaction with phagocytic cells.

Isolation and separation of physicochemically distinct fimbrial types expressed on a single culture of Escherichia coli O7:K1:H6

The fimbrial (pili) profile of a single strain of Escherichia coli O7:K1:H6 (WF96) was evaluated. Fimbriae were isolated by sucrose density gradient ultracentrifugation, purified from flagellae by the use of 0.4% sodium dodecyl sulfate (SDS), and separated into distinct fimbrial types. Analysis of the purified WF96 fimbriae by SDS-polyacrylamide gel electrophoresis revealed two polypeptide bands with molecular weights of 16,000 and 21,000. Treatment of the fimbrial mixture with saturated guanidine hydrochloride resulted in the appearance of a third band with a molecular weight of 19,500. The relative susceptibilities of the WF96 fimbrial types to disrupting chemicals (octyl-glucoside, urea, SDS, and guanidine hydrochloride) were assessed by exposure of the fimbrial mixture to each agent, separation of the depolymerized fimbriae from intact fimbriae by gel filtration on Sepharose CL-4B, and identification of the disaggregated fimbrial types by SDS-polyacrylamide gel electrophoresis of column fractions. The physicochemical heterogeneity of the three fimbrial types coexpressed on WF96 was exploited to develop a method for separation of individual fimbriae.