Eikenella corrodens adherence to human buccal epithelial cells.

The mechanism of Eikenella corrodens adherence to human buccal epithelial cells in vitro was studied. Initial experiments to determine the optimal conditions for adherence of E. corrodens to buccal epithelial cells showed that adherence was dependent on time, temperature, bacterial concentration, and pH. Different strains of E. corrodens varied in their ability to adhere, and strain 1073 showed the greatest ability in adherence. Strain 1073 was selected for studies of adherence mechanisms. Trypsin treatment or heating (100 degrees C, 10 min) of the bacterial cells abolished their capacity to adhere to buccal epithelial cells. Treatment of buccal epithelial cells with trypsin also abolished adherence of E. corrodens 1073, whereas neuraminidase treatment of buccal epithelial cells enhanced the adherence. The adherence was inhibited by ethylenediaminetetraacetic acid and restored by adding Ca2+. The adherence was remarkably inhibited by sugars containing D-galactose and n-acetyl-D-galactosamine. Treatment of neuraminidase-treated epithelial cells with sodium metaperiodate or alpha- and beta-galactosidase did not decrease the adherence. These data suggest that adherence of E. corrodens 1073 to human buccal epithelial cells may require the interaction of lectin-like proteins on the bacterial surface with galactose-like receptors on the surface of epithelial cells.     

Biological activities of Eikenella corrodens outer membrane and lipopolysaccharide

Highly purified preparations of the outer membrane and lipopolysaccharide (LPS) of Eikenella corrodens strain ATCC 23834 and the outer membrane fraction (OMF) of strain 470 were tested in in vitro biological assays. The OMFs of both strains were found to be mitogenic for BDF and C3H/HeJ murine splenocytes. The E. corrodens LPS was mitogenic for BDF spleen cells; however, doses of LPS as high as 50 micrograms/ml failed to stimulate C3H/HeJ cells. When incubated with T-lymphocyte-depleted C3H/HeJ splenocytes, the strain 23834 OMF demonstrated significant mitogenic activity, indicating that the OMF is a B-cell mitogen by a mechanism other than that elicited by conventional LPS. The E. corrodens 23834 OMF and LPS were stimulators of bone resorption when tested in organ cultures of fetal rat long bones. In contrast, the strain 470 OMF was only weakly stimulatory. Both OMFs and LPSs demonstrated "endotoxic" activity, since as little as 0.062 micrograms of E. corrodens LPS and 0.015 micrograms of the OMFs induced gelation in the Limulus amebocyte clotting assay. Thus, despite having a "nonclassical" LPS biochemistry, the E. corrodens LPS elicits classical endotoxic activities. These results also indicate that the surface structures of E. corrodens have significant biological activities as measured in vitro. The expression of such activities in vivo may play an important role in the pathogenesis of periodontitis as well as other E. corrodens infections.     

An Eikenella corrodens toxin detected by plaque toxin-neutralizing monoclonal antibodies.

Bacterial plaque from the gingival region of teeth contains cytotoxic agents which lyse undifferentiated human HL60 cells. A small panel of monoclonal antibodies (MAbs) was found to abrogate much of this activity and to detect antigens in certain strains of Streptococcus mitis and Eikenella corrodens. The aim of this study was to determine whether these bacterial antigens might be involved in HL60 cells cytolysis. Saline extracts were obtained by homogenizing washed, stationary-phase cells in 65 mM NaCl with a tight-fitting Potter-Elvehjem homogenizer. The extracts of E. corrodens were toxic to HL60 cells, whereas similar extracts of S. mitis were nontoxic. Adding plaque toxin-neutralizing MAb 3hE5 blocked the toxic effect of E. corrodens extract S. mitis extracts contained a single, strongly reactive antigen of 140 kDa (s140K antigen) detected on Western blots (immunoblots) by three MAbs from the panel. Rabbit antibodies raised to this antigen excised from the gel (anti-s140K serum) detected larger antigens in addition to s140K. E. corrodens extracts contained a number of antigens detected by the MAbs. Immunoglobulin G (IgG) was purified from anti-s140K serum by passage through DE52 cellulose. A 100-fold excess (by weight) of the purified IgG to E. corrodens protein specifically cross-precipitated an 80-kDa antigen plus a nonantigenic 16-kDa protein, presumably attached noncovalently. The remaining supernatant fraction had no toxic activity. A similar ratio of control IgG (from nonimmunized rabbits) did not precipitate these proteins, and the supernatant fraction had the same activity as the extract not treated with IgG. The proteins of 80 and 16 kDa were also detected in the anti-s140K immunoprecipitate by rabbit IgG antibodies to E. corrodens whole cells. The 80-kDa antigen, alone or complexed with the 16-kDa protein, may be involved in mediating the toxic activity in E. corrodens and plaque extracts.     

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.     

Cysteine protease of Porphyromonas gingivalis 381 enhances binding of fimbriae to cultured human fibroblasts and matrix proteins.

It has been shown that Porphyromonas gingivalis 381, a suspected periodontopathogen, possesses fimbriae on its cell surface. The organism is also known to produce proteases which can degrade the host cell surface matrix proteins. In this study, we investigated the effect of protease on the binding of the purified P. gingivalis fimbriae to cultured fibroblasts or matrix proteins. A protease that can hydrolyze benzoyl-L-arginine p-nitroanilide was obtained from P. gingivalis 381 cells by sonication in phosphate-buffered 0.2% Triton X-100 and was purified by column chromatography. The molecular size of the protease was estimated to be 55 kDa by gel filtration or 47 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. The enzyme activity was markedly inhibited by sulfhydryl reagents, antipain, and leupeptin. The protease degraded various host proteins, including collagen and fibronectin, and cleaved the COOH terminus of the arginine residue in peptides such as benzoyl-L-arginine p-nitroanilide. However, P. gingivalis fimbriae were not degraded by protease activity. The enzyme activity was enhanced in the presence of reducing agents or CaCl2. When cultured fibroblasts were partially treated with the protease, the binding of the purified P. gingivalis fimbriae to the fibroblast monolayer was increased significantly. However, this enhancing effect was suppressed upon the addition of antipain and leupeptin. Similarly, binding of the fimbriae to the collagen or fibronectin immobilized on the microtiter wells was also enhanced. Addition of these host matrix proteins efficiently inhibited the binding of fimbriae to the fibroblast monolayer. The binding assay of fimbriae using dipeptidyl ligand affinity column chromatography demonstrated a clear interaction between fimbriae and the arginine residue. Taken together, these results indicate that the P. gingivalis protease at least partially degrades the host matrix proteins, which, in turn, may lead to an increased exposure of the cryptic ligands that can result in enhanced fimbria-mediated binding of this organism to periodontal tissues.     

Purification and characterization of Eikenella corrodens type IV pilin.

Eikenella corrodens is a gram-negative human pathogen associated with periodontal diseases and soft-tissue infections. Pilin was purified by association-dissociation and fast protein liquid chromatography; it had an apparent molecular mass of about 14.8 kDa and an N-terminal amino acid sequence reflective of type IV pilins. Antibodies to the purified protein reacted with pili on whole cells. This is the first report of purification of type IV pili/pilin from this organism. Other type IV pili are important virulence factors; we are currently investigating the biological role of pili in E. corrodens.     

Interaction of Treponema denticola TD-4, GM-1, and MS25 with human gingival fibroblasts.

The adherence of Treponema denticola GM-1, TD-4, and MS25 to human gingival fibroblasts (HGFs) was studied to serve as an introduction to investigations into the interactions of these oral bacteria with human host cells. Under both aerobic (5% CO2) and anaerobic (85% N2 plus 10% H2 plus 5% CO2) environments, the interactions with the HGFs were such that strains GM-1 and MS25 were consistently more adherent than strain TD-4. Polyclonal antibodies to GM-1 inhibited GM-1 adherence by 70%, while MS25 and TD-4 showed differing degrees of cross-reactive inhibition, indicative of common but not identical epitopes on the surface of the three T. denticola strains. Pretreatment of the three strains with trypsin did not inhibit adherence; proteinase K did, however, inhibit this interaction by 80%. Trypsin pretreatment of the HGFs resulted in increases in adherence of 50 and 86% for GM-1 and MS25, respectively, while a decrease of 41% was noted for TD-4. Exposure of the T. denticola strains to sugars and lectin pretreatment of the HGFs implicated adherence mediation by mannose and galactose residues on the HGF surface. Periodate treatment of HGFs resulted in a 50% drop in adherence for GM-1 and MS25, but did not decrease that of TD-4. Addition of fetal bovine serum inhibited adherence of the three strains to differing degrees, with TD-4 being the most susceptible. Addition of purified fibronectin (100 micrograms/ml) resulted in greater than 50% inhibition in GM-1 and MS25 adherence, while a 25% increase occurred with TD-4. While strain differences were noted in some of the parameters studied, the results indicate two possibilities for T. denticola-HGF adherence: a lectinlike adhesin(s) on the T. denticola surface with affinity for galactose and mannose on the HGF surface, and a serum host factor(s) bridging T. denticola and HGFs.     

Inhibition of attachment of Escherichia coli RDEC-1 to intestinal microvillus membranes by rabbit ileal mucus and mucin in vitro.

Intestinal mucus is postulated to play a role in preventing colonization of the gastrointestinal tract by microbial pathogens. To evaluate the ability of both crude mucus and purified mucin, a glycoprotein of goblet cell origin, to inhibit mucosal adherence of enteric pathogens, we examined whether mucus and mucin derived from rabbit ileum interact with the rabbit enteropathogen Escherichia coli RDEC-1. We examined the manner in which mucus and mucin inhibited adherence of bacteria to rabbit ileal microvillus membranes (MVMs) in vitro. The purity of the mucin preparation was demonstrated by polyacrylamide gel electrophoresis before and after reduction and by showing that an antiserum raised to the mucin localized to goblet cells in rabbit intestine. Using radioactive labeling of bacteria, we quantitated attachment of RDEC-1 to MVMs, mucus, and mucin that had been immobilized on polystyrene microtiter wells. Binding of RDEC-1 to MVMs was also determined after preincubation of organisms with crude ileal mucus and purified mucin. RDEC-1 bound to both crude mucus and purified mucin when they expressed lectinlike adhesions, previously designated attachment factor rabbit 1 pili. Adherence of piliated RDEC-1 to MVMs, mucus, and mucin was significantly greater than when the bacteria were nonpiliated. Binding of piliated RDEC-1 to MVMs was decreased by preincubation of bacteria with both crude mucus (45.6 +/- 4.2% of control) and purified mucin (50.2 +/- 5.8%). These data indicate that the E. coli enteropathogen RDEC-1 can bind to purified glycoproteins of goblet cell origin and that adherence of these bacteria to mucin is mediated by expression of pili. The findings also support a role for intestinal mucus and its principal organic constituent, mucin, in preventing adherence of a known E. coli enteric pathogen to apical MVMs of enterocytes.     

Purification and characterization of a protease produced by Vibrio mimicus.

A protease produced by Vibrio mimicus was purified to apparent homogeneity by ammonium sulfate fractionation and successive column chromatography on Sephacryl S-100 and Mono Q Monobeads. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE) of the final preparation of the enzyme revealed the homogeneity of the purified enzyme. Conventional PAGE showed that the purified protease migrated as a single band with protease activity. The molecular weight of the protease was estimated to be about 31,000 on the basis of its mobility on sodium dodecyl sulfate-PAGE. The purified protease had both proteolytic and hemagglutination (HA) activities. The proteolytic and HA activities were inhibited by metalloprotease inhibitors and heat treatment. V. mimicus protease therefore appeared as a heat-labile, bifunctional molecule capable of mediating proteolysis and HA. The immunodiffusion analysis showed that the proteases produced by Vibrio cholerae and V. mimicus are immunologically cross-reactive.     

Enzyme-linked immunosorbent assay for adherence of bacteria to animal cells.

Epithelial cells scraped from human oral mucosa and from pig intestines were immobilized onto the flat bottom surfaces of microtiter plates to study the adherence of various bacterial species to host cells. Bacterial adherence was quantitated either by an enzyme-linked immunosorbent assay technique with specific antibacterial serum as the first antibody followed by peroxidase-conjugated second antibody or by using biotinylated bacteria and avidin-peroxidase as the detecting agent. Unlabeled Escherichia coli and purified E. coli 987P fimbriae inhibited the adherence of biotinylated E. coli to immobilized enterocytes. The adherence of a mannose-sensitive strain of E. coli to immobilized oral epithelial cells was inhibited by mannose derivatives. The adherence of fimbriated E. coli 987P to immobilized enterocytes was approximately four times higher than the adherence of a nonfimbriated variant of the same strain. The adherence of Streptococcus pyogenes to oral cells was detected in the range of 10 to 150 bacteria per cell and was inhibited by lipoteichoic acid and albumin. The data suggest that the putative receptors which bind bacteria on the immobilized cells retain a functional form similar to that of native cells in suspension. The proposed adherence assay is easy to perform, allows the detection of specific adherence of test bacteria, and provides objective quantitation of adherence with a sensitivity of 10 bacteria per cell. Most importantly, the assay allows the testing of many variables in the same day.     

Participation of the serine-rich Entamoeba histolytica protein in amebic phagocytosis of apoptotic host cells

Entamoeba histolytica is an intestinal ameba that causes dysentery and liver abscesses. Cytotoxicity and phagocytosis of host cells characterize invasive E. histolytica infection. Prior to phagocytosis of host cells, E. histolytica induces apoptotic host cell death, using a mechanism that requires contact via an amebic galactose-specific lectin. However, lectin inhibition only partially blocks phagocytosis of already dead cells, implicating at least one additional receptor in phagocytosis. To identify receptors for engulfment of apoptotic cells, monoclonal antibodies against E. histolytica membrane antigens were screened for inhibition of phagocytosis. Of 43 antibodies screened, one blocked lectin-independent uptake of apoptotic cells, with >90% inhibition at a dose of 20 μg/ml (P < 0.0003 versus control). The same antibody also inhibited adherence to apoptotic lymphocytes and, to a lesser extent, adherence to and killing of viable lymphocytes. The antigen recognized by the inhibitory antibody was purified by affinity chromatography and identified by liquid chromatography-mass spectrometry as the serine-rich E. histolytica protein (SREHP). Consistent with this, the inhibitory antibody bound to recombinant SREHP present in bacterial lysates on immunoblots. The SREHP is an abundant immunogenic surface protein of unclear function. The results of this unbiased antibody screen strongly implicate the SREHP as a participant in E. histolytica phagocytosis and suggest that it may play an important role in adherence to apoptotic cells.     

Escherichia coli strain RDEC-1 AF/R1 endogenous fimbrial glycoconjugate receptor molecules in rabbit small intestine

Escherichia coli strain RDEC-1 causes a diarrheagenic infection in rabbits with AF/R1 fimbriae, which have been identified as an important colonization factor in RDEC-1 adherence leading to disease. The AF/R1-mediated RDEC-1 adherence model has been used as a model systems for E. coli diarrheal diseases. In this study, RDEC-1 adhered specifically to small intestinal brush borders, with both sialic acid and beta-galactosyl residues apparently involved. The AF/R1-mediated adherence activity of [(14)C]-labeled RDEC-1 was analyzed quantitatively by using 24-well plates coated with purified brush borders and purified microvilli. Two microvillus membrane proteins (130 and 140 kDa) were individually isolated, and chicken antibody raised to each protein inhibited bacterial adherence. These same two proteins, previously shown to be recognized by AF/R1, were individually digested with trypsin, and the amino acid sequences of peptides were determined by reversed-phase capillary liquid chromatography-mass spectrometry tandem mass spectrometry (LC-MS). This LC-MS analysis indicated that these proteins are subunits of the rabbit sucrase-isomaltase protein (SI) complex. Guinea pig serum raised to purified rabbit SI complex inhibited bacterial adherence to microvilli. Additionally, as determined by high-performance thin-layer chromatography and autoradiography, RDEC-1 adhered selectively, via AF/R1 fimbriae, to a glycolipid tentatively identified as galactosylceramide (Gal beta 1-1Cer) in the lipid extract of rabbit small intestinal brush borders. RDEC-1 adherence to Gal beta 1-1Cer was partially inhibited in the presence of galactose. These combined results indicate that the endogenous receptor molecule for AF/R1 fimbriae of RDEC-1 is each individual component of the SI complex, although binding to glycolipid may be responsible for an additional adherence mechanism.     

Purification and characterization of an outer membrane protein adhesin from Haemophilus parainfluenzae HP-28.

Outer membranes were isolated from Haemophilus parainfluenzae HP-28 by a mild extraction method followed by Sephadex G-150 gel filtration chromatography. The first peak (pool 1) recovered contained an activity which inhibited adherence of HP-28 cells to saliva-coated spheroidal hydroxyapatite. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of pool 1 revealed a dominant protein band of 34 kDa. The SDS-PAGE-purified 34-kDa protein was excised from the gel and used for antibody preparation in rabbits. The antiserum produced was analyzed by immunoblot and was shown to be monospecific for the 34-kDa protein. Anti-34-kDa protein antibody was purified from the rabbit antiserum by protein A-Sepharose 6MB affinity chromatography. This antibody was then cross-linked to protein A-Sepharose 6MB to construct a second affinity column. The 34-kDa proteins were purified from outer membranes by this affinity chromatography. The 34-kDa protein was homogeneous, as confirmed by SDS-PAGE, isoelectric focusing, and reverse-phase chromatography analyses. Fab and Fc fragments of the purified anti-34-kDa protein antibodies were prepared by papain digestion, followed by carboxymethyl cellulose chromatography. Fab fragments from the anti-34-kDa protein antibody and the affinity-purified 34-kDa protein both showed significant inhibition of parent H. parainfluenzae HP-28 cell adherence to experimental salivary pellicle and to Streptococcus sanguis SA-1.     

Elastolytic activity of peripheral blood monocytes

Human peripheral blood monocytes have been purified by Ficoll-Hypaque density gradient centrifugation and adherence to plastic dishes, and assayed for elastolytic activity using insoluble [3H]elastin. Approximately 5-10 micrograms of elastin are solubilized at pH 7.5 per mg protein per h. The specific activity in monocytes varies between 3 and 15% of that of neutrophils obtained at the same time from the same subjects. The enzymatic activity derives principally from monocytes. Lymphocytes purified by Sephadex G-10 gel filtration chromatography exhibit only trace elastolytic activity, while neutrophils comprise 1% or less of the cell population. Monocyte elastolytic activity is inhibited by alpha-1-antitrypsin and Succinyl-Ala-Ala-Pro-Val-chloromethylketone indicating that it is a serine-type protease. When extracts of monocytes are analyzed by gel filtration, the elastolytic activity appears in large molecular weight forms; however, these forms are not observed when extracts of monocyte lysosomes are analyzed. Such variation in forms is also seen with neutrophil extracts. Monocytes are a source of elastolytic activity for various physiologic and pathologic actions in the lung and other organs.     

Synthetic peptides analogous to the fimbrillin sequence inhibit adherence of Porphyromonas gingivalis.

Fimbriae are important in the adherence of many bacterial species to the surfaces they eventually colonize. Porphyromonas (Bacteroides) gingivalis fimbriae appear to mediate adherence to oral epithelial cells and the pellicle-coated tooth surface. The role and contribution of fimbriae in the binding of P. gingivalis to hydroxyapatite (HAP) coated with saliva as a model for the pellicle-coated tooth surface were investigated. 3H-labeled P. gingivalis or the radioiodinated purified fimbriae were incubated with 2 mg of HAP beads coated with whole human saliva (sHAP) and layered on 100% Percoll to separate unbound from sHAP-bound components. The radioactivity of the washed beads was a measure of the bound components. The binding of P. gingivalis 2561 (381) cells and that of purified fimbriae were concentration dependent and saturable at approximately 10(8) cells and 40 micrograms of fimbriae added, respectively. The addition of fimbriae inhibited binding of P. gingivalis to sHAP beads by 65%, while the 75-kDa protein, which is another major surface component of P. gingivalis 2561, did not show significant inhibition, suggesting that the fimbriae are important in adherence. Encapsulated and sparsely fimbriated P. gingivalis W50 did not bind to sHAP beads. On the basis of the predicted sequence of the fimbrillin, a structural subunit of fimbriae, a series of peptides were synthesized and used to localize the active fimbrillin domains involved in P. gingivalis adherence to sHAP beads. Peptides from the carboxyl-terminal one-third of the fimbrillin strongly inhibited P. gingivalis binding to sHAP beads. Active residues within the sequence of inhibitory peptide 226-245 (peptide containing residues 226 to 245) and peptide 293-306 were identified by using smaller fragments prepared either by trypsin cleavage of the peptide 226-245 or by synthesis of smaller segments of peptide 293-306. Hemagglutinin activity, lectinlike binding, and ionic interaction did not seem to be involved in this binding since lysine, arginine, carbohydrates, and calcium ions failed to affect the binding of P. gingivalis. The observation that poly-L-lysine, bovine serum albumin, and defatted bovine serum albumin, even at high concentrations, only partially blocked the binding of P. gingivalis indicates that hydrophobic interactions are not the major forces involved in P. gingivalis binding to sHAP beads. Protease inhibitors such as EDTA, leupeptin, pepstatin, 1,10-phenanthroline, and phenylmethylsulfonyl fluoride did not interfere with the binding of P. gingivalis. However, the binding of P. gingivalis to trypsin- or chymotrypsin-pretreated sHAP beads was reduced.(ABSTRACT TRUNCATED AT 400 WORDS)     

Purification and properties of hemagglutinin from culture supernatant of Bacteroides gingivalis.

The hemagglutinating factor (hemagglutinin) of Bacteroides gingivalis was prepared from the supernatant of a 5-day diffusate broth culture by ammonium sulfate precipitation and column chromatography with a hydrophobic column of Phenyl-Sepharose CL-4B, DEAE-Sephadex A-50, and Sephadex G-100 gel filtration. The hemagglutinating activity of the preparation was 53.3 times higher than that of ammonium sulfate precipitate. In electron microphotographs, hemagglutinin appears to have a vesicle or tubelike structure. The hemagglutinating activity of intact cells was completely destroyed by heating at 100 degrees C for 10 min, but the activity of extracted hemagglutinin was heat stable. The activity of hemagglutinin was inhibited by L-arginine and L-lysine and partially inhibited by phospholipase D, but it was not affected by proteolytic enzymes, neuraminidase, hyaluronidase, lipase, phospholipase A and C, or sugars. The B. gingivalis hemagglutinin appeared to be comprised mainly of a 40,000-molecular-weight material. The Fab fragment of immunoglobulin G prepared from rabbit antiserum to whole cells of B. gingivalis and monoclonal antibody against the hemagglutinin bound to the cell surface and inhibited the hemagglutinating activity of both the cells and the purified hemagglutinin.     

An inhibitory factor for cell-free protein synthesis from Salmonella enteritidis exhibits cytopathic activity against Chinese hamster ovary cells.

A factor inhibiting cell-free protein synthesis was purified from Salmonella enteritidis cell lysate by sequential ammonium sulfate precipitation, chromatography on anion exchange and hydrophobic interaction columns, and polyacrylamide disc gel electrophoresis. The purified factor, which was named SIPS (Salmonella inhibitor of protein synthesis), inhibited in vitro protein synthesis in rabbit reticulocyte lysate and had a molecular mass of 38 kDa, estimated by PAGE under denaturing conditions. SIPS was also cytopathic for Chinese hamster ovary cells. The N-terminal amino acid sequence (20 residues) of SIPS was found to be identical to that of mature L-asparaginase II of Escherichia coli. Indeed, the purified SIPS exhibited asparaginase activity, E. coli L-asparaginase II had cytopathic activity and inhibited in vitro protein synthesis. The results suggest that at least a part of cytotoxicity and inhibition of cell-free protein synthesis caused by S. enteritidis is a property of the bacterial L-asparaginase.     

Purification and characterization of a novel hemagglutinin from Vibrio cholerae.

A lectin with strong hemagglutinating activity toward erythrocytes of several animal species was isolated from an 18-h culture supernatant of a diarrheagenic strain, V2, of non-O1 Vibrio cholerae. The hemagglutinin (HA) was purified free of lipopolysaccharide by salt fractionation followed by gel filtration, hydrophobic interaction chromatography, and, finally, gel filtration in the presence of urea and deoxycholate. The purification procedure resulted in an HA preparation with 80-fold enhancement of specific activity. The HA consisted of noncovalently bound subunits of Mr 62,000 and behaved essentially as a single component with pI 6.0. Nonpolar and acidic amino acids contributed 46 and 24%, respectively, to the total amino acid residues. Electron micrographs of the HA showed it to consist of large, nonstoichiometric aggregates' of disklike molecules of 10-nm diameter. Inhibition of the HA by the glycoproteins fetuin, asialofetuin, and mucin, but not by ovalbumin and simple sugars, suggested the specific requirement of complex carbohydrates for binding. Rabbit antisera to the purified HA inhibited the hemagglutinating activities of the crude cell-free HA preparations, but not cell-associated HA activities of the parent (V2) or of other O1 and non-O1 V. cholerae strains. This suggested that the released and cell-associated HA activities were mediated by antigenically distinct components. Immunoblotting experiments showed that the antisera recognized a polypeptide component of Mr 62,000 in the cell envelope preparations of the parent and several other V. cholerae O1 and non-O1 strains. These data suggested that the HA was a nonfimbrial lectin of somatic origin with no protease activity and was apparently distinct from V. cholerae HAs described so far.     

Interaction of Haemophilus influenzae with human erythrocytes and oropharyngeal epithelial cells is mediated by a common fimbrial epitope.

The role of fimbriae in the adherence of Haemophilus influenzae to oropharyngeal epithelial cells and the hemagglutination (HA) of human Anton-positive erythrocytes was examined. HA of bacteria was lost after shearing. Fimbriae purified from the extracellular fluid caused HA and bound to oropharyngeal epithelial cells, as analyzed with immunoperoxidase staining, in a way which was similar to the adherence of bacteria to these cells: binding was over the entire surface of the cells and showed cell-to-cell variation. The specific role of fimbriae in HA and adherence was further examined by inhibition experiments with monoclonal antibodies elicited against the isolated fimbriae. These monoclonal antibodies bound along the entire length of the fimbriae, as seen by immunogold electron microscopy. The monoclonal antibodies and their Fab fragments inhibited HA (reduction in titer from 1:512 to 1:128 and 1:64, respectively) and inhibited the adherence of the homologous H. influenzae strain and of three of eight heterologous H. influenzae strains to oropharyngeal epithelial cells. These results indicate that fimbriae are involved in adherence and HA and that the binding site for the monoclonal antibodies on the fimbriae is not common on all strains.     

Human T-lymphocyte proliferation, lymphokine production, and amebicidal activity elicited by the galactose-inhibitable adherence protein of Entamoeba histolytica.

We studied human T-lymphocyte responses to the purified Entamoeba histolytica galactose-inhibitable adherence protein. Individuals having serum anti-adherence protein antibodies possess peripheral blood lymphocytes which demonstrate antigen-specific responses to the purified adherence protein (10 micrograms/ml) and whole soluble amebic antigen (100 micrograms/ml). This was determined by incorporation of [3H]thymidine (53,080 and 73,114 dpm, respectively) and by increased production of interleukin-2 and gamma interferon (42.0 and 67.5 U/ml, respectively) (P less than 0.05 for each in comparison with values for control lymphocyte responses). Lymphocytes from antiamebic antibody-positive subjects develop in vitro amebicidal activity only when incubated for 5 days with the purified adherence protein (P = 0.02). In conclusion, the E. histolytica galactose-inhibitable adherence protein elicits an in vitro amebicidal cell-mediated immune response, further supporting the potential for the use of this protein in a subunit amebiasis vaccine.