Amphotericin B- and fluconazole-resistant Candida spp., Aspergillus fumigatus, and other newly emerging pathogenic fungi are susceptible to basic antifungal peptides.
The present study shows that a number of basic antifungal peptides, including human salivary histatin 5, a designed histatin analog designated dhvar4, and a peptide from frog skin, PGLa, are active against amphotericin B-resistant Candida albicans, Candida krusei, and Aspergillus fumigatus strains and against a fluconazole-resistant Candida glabrata isolate. (+info)
The cellular target of histatin 5 on Candida albicans is the energized mitochondrion.
Histatin 5 is a human basic salivary peptide with strong fungicidal properties in vitro. To elucidate the mechanism of action, the effect of histatin 5 on the viability of Candida albicans cells was studied in relation to its membrane perturbing properties. It was found that both the killing activity and the membrane perturbing activity, studied by the influx of a DNA-specific marker propidium iodide, were inhibited by high salt conditions and by metabolic inhibitors, like sodium azide. In addition, exposure to histatin 5 resulted in a loss of the mitochondrial transmembrane potential in situ, measured by the release of the potential-dependent distributional probe rhodamine 123. Localization studies using tetramethylrhodamine isothiocyanate-labeled histatin 5 or fluorescein isothiocyanate-labeled histatin 5 showed a granular intracellular distribution of the peptide, which co-localized with mitotracker orange, a permeant mitochondria-specific probe. Like the biological effects, uptake of labeled histatin 5 was inhibited by mitochondrial inhibitors and high salt conditions. Our data indicate that histatin 5 is internalized, and targets to the energized mitochondrion. (+info)
Endogenous mucosal antiviral factors of the oral cavity.
The oral cavity represents a unique site for mucosal transmission of human immunodeficiency virus type 1 (HIV-1). Unlike other mucosal sites, the oral cavity is rarely a site of HIV transmission despite detectable virus in saliva and oropharyngeal tissues of infected persons. One reason for this apparent paradox is the presence of endogenous mucosal antiviral factors. Innate inhibitory molecules, such as virus-specific antibodies, mucins, thrombospondin, and soluble proteins, have been identified and partially characterized from saliva. A recent addition to the growing list is secretory leukocyte protease inhibitor (SLPI), an approximately 12-kDa non-glycosylated protein found in serous secretions. Physiologic concentrations of SLPI potently protect adherent monocytes and activated peripheral blood mononuclear cells against HIV-1 infection. SLPI levels in saliva and semen but not breast milk approximate levels required for inhibition in vitro. Characterization of SLPI and other endogenous antiviral molecules may enhance our understanding of factors influencing mucosal HIV-1 transmission. (+info)
Interactions of Streptococcus mutans fimbria-associated surface proteins with salivary components.
Streptococcus mutans has been implicated as the major causative agent of human dental caries. S. mutans binds to saliva-coated tooth surfaces, and previous studies suggested that fimbriae may play a role in the initial bacterial adherence to salivary components. The objectives of this study were to establish the ability of an S. mutans fimbria preparation to bind to saliva-coated surfaces and determine the specific salivary components that facilitate binding with fimbriae. Enzyme-linked immunosorbent assay (ELISA) established that the S. mutans fimbria preparation bound to components of whole saliva. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot techniques were used to separate components of whole saliva and determine fimbria binding. SDS-PAGE separated 15 major protein bands from saliva samples, and Western blot analysis indicated significant binding of the S. mutans fimbria preparation to a 52-kDa salivary protein. The major fimbria-binding salivary protein was isolated by preparative electrophoresis. The ability of the S. mutans fimbria preparation to bind to the purified salivary protein was confirmed by Western blot analysis and ELISA. Incubation of the purified salivary protein with the S. mutans fimbria preparation significantly neutralized binding of the salivary protein-fimbria complex to saliva-coated surfaces. The salivary protein, whole saliva, and commercial amylase reacted similarly with antiamylase antibody in immunoblots. A purified 65-kDa fimbrial protein was demonstrated to bind to both saliva and amylase. These data indicated that the S. mutans fimbria preparation and a purified fimbrial protein bound to whole-saliva-coated surfaces and that amylase is the major salivary component involved in the binding. (+info)
Strains of Actinomyces naeslundii and Actinomyces viscosus exhibit structurally variant fimbrial subunit proteins and bind to different peptide motifs in salivary proteins.
Oral strains of Actinomyces spp. express type 1 fimbriae, which are composed of major FimP subunits, and bind preferentially to salivary acidic proline-rich proteins (APRPs) or to statherin. We have mapped genetic differences in the fimP subunit genes and the peptide recognition motifs within the host proteins associated with these differential binding specificities. The fimP genes were amplified by PCR from Actinomyces viscosus ATCC 19246, with preferential binding to statherin, and from Actinomyces naeslundii LY7, P-1-K, and B-1-K, with preferential binding to APRPs. The fimP gene from the statherin-binding strain 19246 is novel and has about 80% nucleotide and amino acid sequence identity to the highly conserved fimP genes of the APRP-binding strains (about 98 to 99% sequence identity). The novel FimP protein contains an amino-terminal signal peptide, randomly distributed single-amino-acid substitutions, and structurally different segments and ends with a cell wall-anchoring and a membrane-spanning region. When agarose beads with CNBr-linked host determinant-specific decapeptides were used, A. viscosus 19246 bound to the Thr42Phe43 terminus of statherin and A. naeslundii LY7 bound to the Pro149Gln150 termini of APRPs. Furthermore, while the APRP-binding A. naeslundii strains originate from the human mouth, A. viscosus strains isolated from the oral cavity of rat and hamster hosts showed preferential binding to statherin and contained the novel fimP gene. Thus, A. viscosus and A. naeslundii display structurally variant fimP genes whose protein products are likely to interact with different peptide motifs and to determine animal host tropism. (+info)
Molecular interactions of Porphyromonas gingivalis fimbriae with host proteins: kinetic analyses based on surface plasmon resonance.
Fimbriae of Porphyromonas gingivalis are thought to play an important role in the colonization and invasion of periodontal tissues. In this study, we analyzed the interactions of P. gingivalis fimbriae with human hemoglobin, fibrinogen, and salivary components (i.e., proline-rich protein [PRP], proline-rich glycoprotein [PRG], and statherin) based on surface plasmon resonance (SPR) spectroscopy with a biomolecular interaction analyzing system (BIAcore). The real-time observation showed that the fimbriae interacted more quickly with hemoglobin and PRG than with other proteins and more intensely with fibrinogen. The significant association constant (ka) values obtained by BIAcore demonstrated that the interactions between fimbriae and these host proteins are specific. These estimated Ka values were not too different; however, the Ka values for hemoglobin (2.43 x 10(6)) and fibrinogen (2.16 x 10(6)) were statistically greater than those for the salivary proteins (1.48 x 10(6) to 1.63 x 10(6)). The Ka value of anti-fimbriae immunoglobulin G for fimbriae was estimated to be 1. 22 x 10(7), which was 6.55-fold higher than the mean Ka value of the host proteins. Peptide PRP-C, a potent inhibitor of PRP-fimbriae interaction, dramatically inhibited fimbrial association to PRP and PRG and was also inhibitory against other host proteins by BIAcore. The binding of fimbriae to these proteins was also evaluated by other methods with hydroxyapatite beads or polystyrene microtiter plates. The estimated binding abilities differed considerably, depending on the assay method that was used. It was noted that the binding capacity of PRP was strongly diminished by immobilization on a polystyrene surface. Taken together, these findings suggest that P. gingivalis fimbriae possess a strong ability to interact with the host proteins which promote bacterial adherence to the oral cavity and that SPR spectroscopy is a useful method for analyzing specific protein-fimbriae interactions. (+info)
A critical comparison of the hemolytic and fungicidal activities of cationic antimicrobial peptides.
The hemolytic and fungicidal activity of a number of cationic antimicrobial peptides was investigated. Histatins and magainins were inactive against human erythrocytes and Candida albicans cells in phosphate buffered saline, but displayed strong activity against both cell types when tested in 1 mM potassium phosphate buffer supplemented with 287 mM glucose. The HC50/IC50 ratio, indicative of the therapeutic index, was about 30 for all peptides tested. PGLa was most hemolytic (HC50 = 0.6 microM) and had the lowest therapeutic index (HC50/IC50 = 0.5). Susceptibility to hemolysis was shown to increase with storage duration of the erythrocytes and also significant differences were found between blood collected from different individuals. In this report, a sensitive assay is proposed for the testing of the hemolytic activities of cationic peptides. This assay detects subtle differences between peptides and allows the comparison between the hemolytic and fungicidal potency of cationic peptides. (+info)
Kinetic analysis on nitric oxide binding of recombinant Prolixin-S, a nitric oxide transport protein from the bloodsucking bug, Rhodnius prolixus.
Kinetics of the NO binding and removal reaction of recombinant Prolixin-S (rProlixin-S) were analyzed using stopped-flow spectrophotometry. The reaction was observed as a biphasic process. The rate constant of the fast phase increased linearly as NO concentration increased. The rate constant at the slow phase increased as NO concentrations increased at low NO concentration, then reached a plateau at high NO concentration. These NO dependencies of the reaction are characteristic of a bimolecular two-step consecutive reaction. The reaction consisted of the fast NO binding reaction of rProlixin-S and the following slow structural change of NO-protein complex. Kinetic studies revealed that the NO binding rate constant was independent of pH, but the rate constant of the NO removal reaction increased as pH increased. The apparent NO dissociation constant (Kd) of rProlixin-S was also calculated from the values of the kinetic parameters obtained in this work. The Kd value increased as pH and temperature increased. The Kd value of rProlixin-S and NO was 10-300 nM in regular physiological condition, which is 103 higher and 103 lower than those of the other ferric and ferrous hemoproteins and NO, respectively. These results indicate that Prolixin-S is one of NO transport proteins regulating blood pressure. (+info)