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The interaction between each one of Trichomonas vaginalis and Tritrichomonas foetus with their hosts is a complex process in which components associated to the cell surfaces of both parasites and host epithelial cells, and also to soluble components found in vaginal/urethral secretions, are involved. Either cytoadhesion or the cytotoxicity exerted by parasites to host cells can be dictated by virulence factors such as adhesins, cysteine proteinases, laminin-binding proteins, integrins, integrin-like molecules, a cell detachment factor, a pore-forming protein, and glycosidases among others. How trichomonads manipulate informations from the extracellular medium, transduce such informations, and respond to them by stimulating the activities of some surface molecules and/or releasing enzymes are the aspects concerning trichomonal virulence which are here briefly reviewed and discussed.

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Cell surface saccharide composition and surface charge of promastigote (PRO) and opisthomorph (OPM) forms of Herpetomonas roitmani were analyzed using labeled lectins and flow cytometry and cell electrophoresis. The FITC signals for concanavalin A, Helix pomatia agglutinin and wheat germ agglutinin were stronger in PRO forms, whereas for Limulus polyphemus agglutinin (LPA) and Wisteria floribunda agglutinin they were stronger in OPM forms. Prior treatment of the cells with neuraminidase decreased the FITC signal for LPA in OPM but not in PRO forms. Furthermore OPMs displayed a high negative charge (-15.45+/-1.10 mV) than PROs (-9.47+/-1.01 mV). Neuraminidase and phospholipase C treatment of the parasites significantly reduced the surface charge, especially in OPM forms. TLC analysis of the acidic components of H. roitmani showed the presence of N-acetyl-neuraminic acid. The results presented in this work indicate that changes in exposed cell surface components occur between PRO and OPM forms of H. roitmani obtained by growing the cells under different conditions.

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Aedes albopictus cells possess a negative cell surface charge of -12.7 mV with an isoelectrophoretic point (IEP) located between pH 3.0 and 4.0. Infection with Mayaro virus rendered the surface of A. albopictus cells less negative reaching a zeta-potential value of -9.7 mV after 100 h of infection. Concomitantly, the IEP of the infected cells were also altered from 3.0-4.0 to 4.0-5.0. Furthermore, the contact angle measurements clearly showed qualitative alterations in the cell surface of infected cells.

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The surface charge of heart muscle cells (HMC) and Trypanosoma cruzi trypomastigotes was estimated during their interaction by means of zeta potential (ZP). Metacyclic and bloodstream trypomastigote, but not amastigote forms, are able to decrease the surface charge of HMC as well as other nonphagocytic cells. However, no alteration could be detected on T. cruzi-infected macrophage cell line. Trypomastigote forms collected from the supernatant after 20 h of contact with HMC also have their ZP value decreased. The analysis of the surface components of both the parasite and HMC involved in such interaction was also carried out. Assays concerning the kinetics of the cell-parasite interaction demonstrated the influence of parasite surface anionogenicity during its interaction with HMC. The binding of bloodstream forms to HMC was enhanced after their incubation with cationized ferritin (CF), whereas phospholipase C and neuraminidase treatments improved and trypsin treatment inhibited parasite uptake in HMC. Conversely, the incubation of HMC with phospholipase C impaired, and with trypsin enhanced, the interiorization of the parasites. These results suggest that trypomastigote forms of T. cruzi may process the surface of HMC and its own surface either by removing molecules or by exposing ligands for their internalization.

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The surface ionogenicity of five enteropathogenic Escherichia coli serogroups (O111:H2, O111:H12, O125:H9, O119:H6, and O26:H11) was investigated by electrokinetical approaches. All of the studied surfaces are negatively charged with their mean values of zeta potential (ZP) varying from -9.0 (O26:H11) to -11.9 mV (O111:H2). The populational behavior of the all bacteria are similar since very high ZP values varying from -26 to -30 mV were obtained in experiments carried out with the slip plane calculated at 6.83 nm from the cell surface. All the surfaces are extremely acidic, because the isoelectrophoretic points are localized at pH values below 3.0. Treatment of the microorganisms with neuraminidase did not alter their surface anionogenicity, while treatment with trypsin or phospholipase C reduced their negative charge.

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In the present study the parental cells and glycosylation mutants of Chinese hamster ovary (CHO) cells were used to analyze the influence of surface carbohydrates on the cytoadhesion of trichomonads. Trichomonas vaginalis and Tritrichomonas foetus were allowed to interact with host cells for 2 h at 37 degrees C. Alternatively, CHO cells were treated with 10 mM periodate prior to the assays. Both trichomonads adhered to all CHO cell clones tested. A remarkable difference could be observed between the cytoadhesion of T. vaginalis and T. foetus. Sialic acid residues present on the surface of CHO cells may favor the cytoadhesion of T. foetus while hampering that of T. vaginalis. The specificity of the parasite cytoadhesion was further investigated. Sialic acid, mannose, and galactose as well as mannose, galactose, and N-acetylglucosamine added to the interaction medium at 50, 100, and 200 mM were capable of significantly inhibiting the cytoadhesion of each trichomonad species. Periodate treatment of target cells also induced decreases in the cytoadhesion of the trichomonads. These results strongly suggest an important role for host-cell surface glycoconjugates during the cytoadhesion of trichomonads. In addition, they also point out the presence of "lectin-like" molecules on the surface of both T. vaginalis and T. foetus.

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The cell surface hydrophobicity, net electric surface charge and cell adhesion of six group B streptococci strains were assessed. Treatment with trypsin reduced cytoadhesion of the six strains (80340, 90356, 85147, 90222, 90186 and 88641) and induced loss of surface negative charge in the other four strains (80340, 85147, 90222 and 90186). The same treatment increased the surface hydrophobicity of three strains (90356, 90222 and 88641). Neuraminidase treatment caused a decrease in the negative surface charge of all the strains resulting in significant increases in both cytoadhesion and surface hydrophobicity of five (80340, 90356, 85147, 90222 and 88641) and four (90356, 85147, 90222 and 88641) strains, respectively. This indicates that sialic acid residues are important anionogenic groups exposed on the streptococcal cell surface. Treatment of buccal epithelial cells with N-acetyl-beta-D-glucosaminidase made them less adherent for most of the strains (80340, 85147, 90222, 90186 and 88641) assayed.

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The effects of subinhibitory concentrations of metronidazole on the general morphology, ultrastructure and charge and hydrophobicity of Bacteroides fragilis were investigated using transmission and scanning electron microscopy, and measurements of zeta-potentials and contact angles. Metronidazole treatment induced morphological alterations in B. fragilis. Cells became filamentous and showed a significant loss of cytoplasm. The surface anionogenicity and hydrophobicity of B. fragilis were enhanced by the drug treatment. Metronidazole, by modifying B. fragilis surface properties, could alter, indirectly, interactions with host cells.

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The surface charge of Crithidia fasciculata and Crithidia luciliae was analysed by measurement of the zeta-potential and labelling of the protozoan surface with cationized ferritin particles. Both trypanosomatids have a net negative surface charge, with a zeta-potential of -10.39 mV and -11.12 mV for C. luciliae and C. fasciculata, respectively. Enzyme treatment showed that phosphate groups, but not sialic acid, significantly contributed to the negative surface charge. Lectin-induced agglutination was used to analyse the presence of surface-exposed carbohydrates in C. fasciculata and C. luciliae. The cells did not agglutinate when incubated in the presence of lectins which recognized L-fucose, N-acetyl-D-glucosamine and sialic acid. However, lectins which bind to N-acetyl-D-galactosamine, D-galactose and D-mannose agglutinated both protozoa.

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Supernatants taken from axenic cultures of Trichomonas vaginalis and Tritrichomonas foetus contain a neuraminidase activity, the detection of which is augmented when the trichomonad culture media are supplemented with 30% supernatant of confluent epithelial cultures. The enzyme was active against human erythrocytes, which became highly reactive to peanut agglutinin lectin. The specificity of the enzyme was checked by using a substrate specific to neuraminidase: 2'-(4-methylumbelliferyl)-alpha-D-N-acetylneuramic acid.

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The effects of propranolol (10(-3) mM) on the surface anionic groups of Herpetomonas muscarum muscarum were analysed by cell electrophoresis, by ultrastructural cytochemistry and by identification of sialic acids using paper chromatography. Differentiation of H. muscarum muscarum induced by propranolol treatment caused a significant increase in the net negative surface charge. Binding of cationized ferritin (CF) and colloidal iron hydroxide particles was observed at the cell surface of both untreated and propranolol-treated cells. In cells incubated in the presence of the drug the CF particles were distributed in all membrane regions. However, there were small areas where the particles were absent. In H. muscarum muscarum exposed to propranolol the density of residues of sialic acid per cell was higher, and the agglutinating activity with Sendai virus was more intense. However, the pattern of sialic acid, characterized by the presence of N-acetylneuraminic acid derivative, was not modified upon cell interaction with the drug. Treatment of both control and propranolol-treated protozoa with neuraminidase significantly reduced the surface charge. These findings suggest that sialic acid residues are the major anionogenic groups exposed on the surface of H. muscarum muscarum.

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The surface anionic groups of untreated or dimethyl sulfoxide (DMSO)-treated Herpetomonas samuelpessoai cells were analyzed by cell electrophoresis, ultrastructural cytochemistry, and identification of sialic acids using thin-layer chromatography. Differentiation of H. samuelpessoai induced by DMSO treatment caused a significant increase in the net negative surface charge. In flagellates exposed to DMSO, more cationized ferritin, colloidal iron hydroxide, and sendai virus particles bound to the cell surface. Treatment of both untreated and DMSO-treated flagellates with neuraminidase decreased markedly the EPM of cells to the cathodic pole. These findings suggest that sialic acid residues are the major anionogenic groups exposed on the surface of H. samuelpessoai. Thin-layer chromatography showed that N-acetyl and N,O-diacylneuraminic acids, in equal proportions, were present in H. samuelpessoai. However, N-acetylneuraminic acid predominates in DMSO-treated cells.

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1. The virulence of pathogens and metastatic capacity of cancer cells seems to correlate with the ability to adhere to cells and/or to basement membrane components. A key feature of this mechanism is the expression of specific receptors for the basement membrane protein laminin. Three different receptors have been already described in cells phylogenetically very distant, such as human white blood cells, Trichomonas vaginalis and Staphylococcus aureus, all recognizing laminin with the same range of affinity. 2. We have shown that laminin, which is also found in the circulation, enhances phagocytosis of S. aureus by macrophages in a species-specific fashion. Also, monoclonal antibodies (MAb) raised against the bacterial receptor inhibit the phagocytic enhancement mediated by laminin and recognize laminin-binding proteins in unicellular parasites and mammalian cells. The same Mab 1.H12 elutes a 52-kDa protein from bacterial extracts and a 67-kDa band from cancer cell extracts. Since the MAb is a monospecific reagent, results with 1.H12 strongly suggest an evolutionary conservation of the binding site of phylogenetically different laminin receptors.

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The surface charge of three strains of Trichomonas vaginalis and five strains of Tritrichomonas foetus was determined by direct measurement of the mean cellular electrophoretic mobility (EPM) of cells suspended in solutions of different ionic strength and pH. No differences were observed in the mean EPM among the two species, although significant differences among the strains exist. Strains that are more pathogenic to mouse, as measured using the subcutaneous assay, had a surface more negative. Treatment of the parasites with trypsin or neuraminidase reduced significantly their mean EPM and increased their isoelectric point. Tritrichomonas foetus was more sensitive to the enzyme treatment than T. vaginalis. Enzyme-treated cells recovered their normal EPM if, after enzyme treatment, they were incubated in fresh culture medium. The recovery process of trypsin-treated cells was inhibited 10-20% by addition of inhibitors of either protein synthesis (puromycin) or N-glycosylation of proteins (tunicamycin) to the incubation medium, suggesting that a cytoplasmic pool of sialoglycoproteins may exist. The recovering of the EPM of T. foetus and T. vaginalis previously treated with neuraminidase was inhibited by puromycin or tunicamycin about 40-50% and 17-30%, respectively. These observations suggest that sialoglycolipids exist on the surface of both parasite species, and that they contribute more to the surface charge of T. vaginalis than to that of T. foetus.

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The surface charge of Tritrichomonas foetus was evaluated by means of the binding of colloidal iron hydroxide particles at pH 1.8 and cationized ferritin particles at pH 7.2 to the cell surface, as visualized by electron microscopy and by direct measurements of the electrophoretic mobility (EPM), of cells suspended in solutions of different ionic strength and pH. At pH 7.2, T. foetus has a negative surface charge with a mean EPM of -1.03 micrometer . s-1 . V-1 . cm. At lower pH, there is a decrease in the negative surface charge with an isoelectric point at pH 1.2. At higher pH (greater than 9.0), there is an increase in the surface charge reaching an EPM of -2.5 micrometers . s-1 . V-1 . cm. These results indicate that the surface of T. foetus contains both negatively and positively charged dissociating groups. Binding of colloidal iron hydroxide and cationized ferritin particles throughout the cell surface of the protozoon was observed. Treatment of T. foetus with neuraminidase or trypsin reduced significantly the EPM of the cells. Enzyme-treated cells recovered their normal EPM when incubated for 6 h in fresh culture medium by a process that is inhibited by puromycin.

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