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At least 127 records · Page 7Linked to original sources
PubMed1989

Differential distribution of immature Ixodes dammini (Acari: Ixodidae) on rodent hosts.

Ectoparasites such as ixodid ticks that remain attached to hosts for several days while feeding on blood are able to overcome the inflammatory and immune responses of some hosts and not others. The immature stages of the deer tick Ixodes dammini are found more frequently on the white-footed mouse, Peromyscus leucopus, than on other rodents. We propose that P. leucopus is more tolerant to I. dammini than is a less common host, the meadow vole, Microtus pennsylvanicus. To test this hypothesis, the distribution patterns and engorgement indices were determined for larval and nymphal I. dammini collected from wild-caught P. leucopus and M. pennsylvanicus. There were more immature ticks, which were more fully engorged, on P. leucopus than on M. pennsylvanicus. There were more and better engorged ticks on male than on female hosts. Laboratory studies on the number and weights of larval I. dammini collected off naive and previously exposed P. leucopus and M. pennsylvanicus support the results of the field study. Fewer larval ticks were recovered from previously exposed M. pennsylvanicus than P. leucopus, and the ticks weighed less. Larval and nymphal ticks aggregated among hosts in the study grid, and higher densities per male P. leucopus were correlated with higher engorgement indices, suggesting that immature I. dammini feed better at higher densities. The feeding success of I. dammini on its preferred host species might be due to its adaptation to the immune and inflammatory reactions of the host.

Animals↗
PubMed1991

Characterisation of potential adhesins of the bacterium Pasteuria penetrans, and of putative receptors on the cuticle of Meloidogyne incognita, a nematode host.

Pasteuria penetrans spores were fragmented by glass bead vortexing, producing exosporial membranes and spore fragments, which consisted of fibre bundles. Both exosporia and spore fragments are capable of host-specific attachment to the cuticle of Meloidogyne incognita, a root-knot nematode host. Putative M. incognita receptors appear to be soluble in beta-mercaptoethanol (BME) but not SDS, and are also sensitive to tryptic digestion and deglycosylation by endoglycosidase F. Polyclonal antibodies against intact spores and spore fragments of antispore antibodies produced 100% inhibition. The antibodies, however, did not show preferential staining of particular spore structures in thin section immunolabelling studies. Exposure of Pasteuria penetrans spores to HCl or urea-SDS-dithiothreitol renders them incapable of attachment to their host juveniles and extensively disrupts fibres that surround the spore core. Protein extracts from spore fragments or from exosporial membranes are identical, and urea-BME extracts from either structure, but not SDS extracts, can inhibit the attachment of spores to juveniles by 60-80%. An inhibitory BME extract from spore fragments was analysed by anion-exchange chromatography and adsorption onto host cuticle followed by immunoblotting. It appeared to contain six potential spore adhesins of approximate Mr 24-29, 38-47, 59, 89, 126, and 190 (x10(3)). Lectin affinity blotting with wheat germ agglutinin and concanavalin A showed that all of these proteins bear terminal N-acetylglucosamine residues and the 38-47 kDa band also bears terminal Glc/Man residues.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Glycosides derived from Hemidesmus indicus R. Br. root inhibit adherence of Salmonella typhimurium to host cells: receptor mimicry.

For centuries, indigenous plants have been used against enteritis but their molecular targets and mode of action remain obscure. The present study was carried out to elucidate the protective and therapeutic role, if any, of glycosides from Hemidesmus indicus against S. typhimurium-induced pathogenesis. Studies were carried out in a human intestinal cell line (Int 407) and a murine macrophage cell line (P388D1) in order to evaluate its potency in local as well as systemic infections. The inhibitory role of the glycosides present in Hemidesmus indicus root extract (GHI) were tested by pre-coating the cells (both Int 407 and P388D1) with GHI prior to infection, and by neutralizing the wild-type bacteria with GHI before cell infection. In both cases, GHI protected the host cells from the cytotoxic effects of the wild S. typhimurium. This suggests that the biologically significant sugars (hexose, hexosamine, fucose and sialic acid etc) present in GHI might be mimicking host cell receptor saccharides and thereby blocking the bacterial ligands from binding to the host cells. Int 407 cells infected with wild-type bacteria had a diffused adherence pattern after 4 h incubation, but this typical character was not observed in cells infected with GHI-treated bacteria and the cells were normal in appearance at 4 h. After 18 h cells infected with wild-type bacteria were hypertrophoid with a disintegrated membrane and wrapped in a bacterial coat, whereas cells infected with treated bacteria had comparatively less morphological changes and few defective shrunken rods adhered locally. This suggests that the glycosides can change the adherence pattern of S. typhimurium from diffused to local. Treated bacteria had less adherence and invasion capability in Int 407 as well as P388D1 cells. The results show the decreased ability of adherence of GHI-treated S. typhimurium was due to a loss of surface hydrophobicity. A nonspecific binding between S. typhimurium and the glycosides was confirmed using ELISA. In summary, the glycosides of H. indicus root inhibited S. typhimurium induced pathogenesis nonspecifically, by reducing bacterial surface hydrophobicity and perhaps also by mimicking host cell receptors, thereby blocking its attachment to host cell and further pathological effects.

Animals↗
PubMed2004

Specificity of attachment sites of larval water mites (Hydrachnidia, Acari) on their insect hosts (Chironomidae, Diptera)--evidence from some stream-living species.

This study concerns the parasite-host associations of water mite larvae and their chironomid hosts in a small stream on the North German Plain. The different feeding sites on the host were tested as to whether they represented a strategy of the parasites regarding host partitioning. The attachment sites of nine ectoparasitic water mite species were observed in detail: Aturus fontinalis, Atractides nodipalpis, Feltria rouxi, Hygrobates nigromaculatus, Protzia eximia, Sperchonopsis verrucosa, Sperchon clupeifer, S. setiger and Lebertia inaequalis. Aturus fontinalis, A. nodipalpis, F. rouxi and H. nigromaculatus distinctly preferred sites on the abdomen of the host, whereas the other species preferred feeding sites on the thorax. The four species that preferentially attached to the abdomen of the host showed a distinct specificity for selected segmental and/or intersegmental regions. All species differed in their sites along the length of the abdomen. The order of attachment on the abdominal segments was, from anterior to posterior: H. nigromaculatus, F. rouxi, A. fontinalis and A. nodipalpis. The sites were analysed with regard to segmental and intersegmental attachment, the proportion of dorsal and ventral sites and the differences between attachment to different host species. Larvae attached to their hosts as single individuals showed only slight differences from the sites of mites on hosts that carried many mite larvae. The finding that less than 10% of the chironomids were parasitized by more than one water mite species suggested that, at least in the zoocoenosis of the studied collecting site, the interspecific competition for attachment sites was not strong. However, the specificity of attachment sites clearly had the potential of diminishing competition between water mite species by host partitioning. Intra- and interspecific competition for preferred sites and preparasitic constraints are discussed.

Animals↗
PubMed1986

Diurnal detachment of immature deer ticks (Ixodes dammini) from nocturnal hosts.

To test the possibility that immature deer ticks (Ixodes dammini) may concentrate in the nests of their mouse hosts, we recorded their pattern of detachment. In laboratory experiments, most engorged larvae (greater than 90%) and nymphs (greater than 80%) detached from hamsters between 1200-2000 hours when the 14-hr photophase began at 0600 hours. Time of drop-off was similar regardless of when ticks attached to hosts, but attachment late in the day delayed drop-off by one full day. Ticks detached similarly from naturally-infested Peromyscus leucopus. A post-attachment cue or cues appeared to regulate time of detachment. Such synchronous diurnal detachment may serve to concentrate ticks in the nests of their nocturnal mouse hosts, thereby enhancing pathogen transmission.

Animals↗
PubMed2004

Mycobacterium avium subsp. paratuberculosis fibronectin attachment protein facilitates M-cell targeting and invasion through a fibronectin bridge with host integrins.

Efficient attachment and ingestion of Mycobacterium avium subsp. paratuberculosis by cultured epithelial cells requires the expression of a fibronectin (FN) attachment protein homologue (FAP-P) which mediates FN binding by M. avium subsp. paratuberculosis. Invasion of Peyer's patches by M. avium subsp. paratuberculosis occurs through M cells, which, unlike other intestinal epithelial cells, express integrins on their luminal faces. We sought to determine if the interaction between FAP-P of M. avium subsp. paratuberculosis and soluble FN enabled targeting and invasion of M cells by M. avium subsp. paratuberculosis in vivo via these surface integrins. Wild-type and antisense FAP-P mutant M. avium subsp. paratuberculosis strains were injected alone or coinjected with blocking peptides or antibodies into murine gut loops, and immunofluorescence microscopy was performed to assess targeting and invasion of M cells by M. avium subsp. paratuberculosis. Nonopsonized M. avium subsp. paratuberculosis preferentially invaded M cells in murine gut loops. M-cell invasion was enhanced 2.6-fold when M. avium subsp. paratuberculosis was pretreated with FN. Invasion of M cells by the antisense FAP-P mutant of M. avium subsp. paratuberculosis was reduced by 77 to 90% relative to that observed for the control strains. Peptides corresponding to the RGD and synergy site integrin recognition regions of FN blocked M. avium subsp. paratuberculosis invasion of M cells by 75 and 45%, respectively, whereas the connecting segment 1 peptide was noninhibitory. Antibodies against the alpha5, alphaV, beta1, and beta3 integrin subunits inhibited M-cell invasion by 52 to 73%. The results indicate that targeting and invasion of M cells by M. avium subsp. paratuberculosis in vivo is mediated primarily by the formation of an FN bridge formed between FAP-P of M. avium subsp. paratuberculosis and integrins on M cells.

Adhesins, Bacterial↗
PubMed1976

Boophilus microplus: the effect of host resistance on larval attachments and growth.

Growth and behaviour of Boophilus microplus larvae on British breed cattle, with different resistance levels to the tick, were studied to elucidate the nature of resistance. On highly resistant animals, larval growth rate was slower for the first 3 days, but by day 4 they had attained the normal weight and the majority were subsequently able to moult. Using phosphorus-32 labelled larvae, it was found that attachment times were shorter and more time was spent wandering on highly resistant animals during the first 16 h. On the second day, attachments had stabilized, but more detachments were still made from highly resistant animals. This was considered to impose an additional stress as the cattle skin environment can rapidly desiccate larvae. However, the larvae were able to compensate by uptake of fluid from the host. Loss by repulsion of live larvae from the host or drowning in serous exudate were also not considered of major importance. The nature of rejection is discussed in a further paper. The distribution of larvae after 24 h suggests that their early behaviour largely determines the areas favoured by adults. Movement to, and accumulation in, favoured areas is discussed.

Animals↗
PubMed2003

Deletion analysis identifies key functional domains of the cytadherence-associated protein HMW2 of Mycoplasma pneumoniae.

Mycoplasma pneumoniae attachment to host cells requires biogenesis of a functional attachment organelle, including proper localization of the adhesion protein P1 to this structure. Mutations in the hmw2 gene result in the inability to cytadhere, failure to localize P1 to the attachment organelle, altered cell morphology and accelerated turnover of the cytadherence-associated proteins HMW1, HMW3 and P65. The hmw2 gene encodes HMW2 (190 kDa) and P28 (28 kDa), the latter apparently the product of internal translation initiation near the 3' end of the hmw2 coding region. Transformation of hmw2 mutant I-2 with recombinant wild-type hmw2 restores a wild-type phenotype. In the current study, a severely truncated hmw2 gene with an in frame internal deletion of 80% of the HMW2 coding region that leaves the P28-encoding region intact restored cytadherence to mutant I-2. Transformants produced the expected 38 kDa HMW2 derivative (HMW2Deltamid) at levels comparable to that of HMW2 in wild-type cells; like HMW2, HMW2Deltamid exhibited marked Triton X-100 insolubility. HMW3, P65 and P28 were fully restored, but not HMW1. These transformants were morphologically similar to wild-type M. pneumoniae but failed to localize P1 to the attachment organelle. Finally, a C-terminally truncated HMW2 derivative was partly Triton X-100 soluble and incapable of restoring HMW1, HMW3 and P65 to wild-type levels. These data are consistent with a model in which the C-terminal domain of HMW2 imparts normal localization to the protein, and this localization itself is required for productive interactions with downstream cytadherence-associated proteins. Furthermore, these results emphasize the association of HMW1 with P1 clustering.

Adhesins, Bacterial↗
PubMedDate not supplied

Attachment of mycoplasmas to host cell membranes.

Pathogenic mycoplasmas rarely invade the tissues or bloodstream. Their adherence to epithelial cell surface, the first stage in disease, involves protein binding sites on the mycoplasmal cell membrane and receptors on the host cell membrane. Strong evidence indicates that Mycoplasma gallisepticum and Mycoplasma pneumoniae adhere with the aid of sialic acid residues on host cells, but the data do not preclude participation by other host-cell membrane components. Several studies indicate that these mycoplasmas adhere by blebs or terminal structures; others suggest that binding occurs via other cell areas. Scanning electron microscopy suggests tight interaction between these mycoplasmas and red blood cell membranes, causing imprints resembling those from interaction of viruses with red blood cells. Because sialoglycoproteins are major sites for attachment of M. pneumoniae to respiratory epithelium and red blood cells, glycophorin--the major sialoglycoprotein of human red blood cells--was the ligand used in affinity chromatography for isolation of the binding sites specific for sialic acid receptors from M. pneumoniae membranes solubilized by detergents. The fraction eluted with 0.2% sodium dodecylsulfate from the glycophorin-Sepharose column, highly enriched with two proteins, exhibited high binding capacity to glycophorin-Sepharose beads and lower binding capacity to human red blood cells. The latter capacity was nearly abolished by glycophorin, but not by its hydrophobic moiety.

Adhesiveness↗
PubMed2003

Antibody-enhanced pneumococcal adherence requires IgA1 protease.

IgA, the major class of Ig in secretions, classically functions by interfering with microbial attachment to host tissues. Many mucosal pathogens, including Streptococcus pneumoniae, express an IgA1 protease that may circumvent the protective effects of this Ig subclass. Because these proteases are specific for human IgA1, we generated human mAbs to the major surface antigen of the pneumococcus, its capsular polysaccharide, and tested their effect in a colonization model of bacterial adherence to respiratory epithelial cells in culture. Rather than inhibiting adherence, type-specific IgA1 markedly enhanced bacterial attachment to host cells, but only when cleaved by IgA1 protease. Neither antibodies of protease-insensitive subclasses (IgA2 and IgG) nor those directed against heterologous capsules had such activity. The adherence-promoting properties of cleaved antibodies correlated with the cationic characteristics of their variable segments, suggesting that bound Fab fragments may neutralize the inhibitory effect of negatively charged capsules on adhesive interaction with host cells. Coating of pneumococci with anticapsular polysaccharide antibody unmasked the bacterial phosphorylcholine ligand, allowing for increased adherence mediated by binding to the platelet activating factor receptor on epithelial cells. In addition, our findings provide evidence for a novel function of bacterial IgA1 proteases. These enzymes may enable pathogens to subvert the antigen specificity of the humoral immune response to facilitate adhesive interactions and persistence on the mucosal surface.

Adult↗
PubMed2003

Adaptation of the Lyme disease spirochaete to the mammalian host environment results in enhanced glycosaminoglycan and host cell binding.

The Lyme disease spirochaete, Borrelia burgdorferi, is transmitted to mammals by Ixodes ticks and can infect multiple tissues. Host cell attachment may be critical for tissue colonization, and B. burgdorferi cultivated in vitro recognizes heparin- and dermatan sulphate-related glycosaminoglycans (GAGs) on the surface of mammalian cells. To determine whether growth of the spirochaete in the mammalian host alters GAG binding, we assessed the cell attachment activities of B. burgdorferi grown in vitro or in dialysis membrane chambers implanted intraperitoneally in rats. Host-adapted B. burgdorferi exhibited approximately threefold better binding to purified heparin and dermatan sulphate and to GAGs expressed on the surface of cultured endothelial cells. Three B. burgdorferi surface proteins, Bgp, DbpA and DbpB, have been demonstrated previously to bind to GAGs or to GAG-containing molecules, and we show here that recombinant derivatives of each of these proteins were able to bind to purified heparin and dermatan sulphate. Immunofluorescent staining of in vitro-cultivated or host-adapted spirochaetes revealed that DbpA and DbpB were present on the bacterial surface at higher levels after host adaptation. Recombinant Bgp, DbpA and DbpB each partially inhibited attachment of host-adapted B. burgdorferi to cultured mammalian cells, consistent with the hypothesis that these proteins may promote attachment of B. burgdorferi during growth in the mammalian host. Nevertheless, the partial nature of this inhibition suggests that multiple pathways promote mammalian cell attachment by B. burgdorferi in vivo. Given the observed increase in cell attachment activity upon growth in the mammalian host, analysis of host-adapted bacteria will facilitate identification of the cell binding pathways used in vivo.

Adaptation, Physiological↗
PubMed1996

Limitations in the use of attachments in a Mediterranean population.

It has been asserted that the average height of natural teeth in Mediterranean Latin populations is relatively short and that these teeth are of insufficient size to host standard attachments manufactured by different companies. The occlusogingival height of 159 potential abutment teeth from 50 Spanish patients was measured and compared to the sizes of intracoronal and extracoronal attachments available from one manufacturer. Twenty-one abutments (13% of the sample) were smaller than the smallest intracoronal attachment available. Eighty-seven percent of the abutments in the sample would have allowed the use of an attachment. However, only 11% of the sample would have allowed the use of a large intracoronal or medium extracoronal attachment, and none would have been able to host a large extracoronal attachment. In addition, 35% of the sample could only have accepted a small intracoronal attachment. In such cases, the capacity for retention would have to be carefully evaluated.

Adult↗
PubMed1992

Attachment of Trypanosoma cruzi to host cells: a monoclonal antibody recognizes a trypomastigote stage-specific epitope on the gp 83 required for parasite attachment.

A set of monoclonal antibodies against the purified surface gp 83 of T. cruzi trypomastigotes was produced and the ability of these monoclonals to inhibit the attachment of trypomastigotes to heart myoblasts was investigated. Western blots of solubilized trypomastigotes, epimastigotes or amastigotes probed with this set of monoclonal antibodies show that the gp 83 is present in invasive trypomastigotes, but not in non-invasive epimastigotes or amastigotes. One monoclonal antibody (Mab 4A4) from this set inhibits the attachment of trypomastigotes to heart myoblasts, whereas the others (MAbs 2H6, 4B9, 2D11) do not. These results show that the Mab 4A4 recognizes an epitope on the gp 83 of invasive trypomastigotes required for parasite binding to host cells.

Animals↗
PubMed1981

Attachment of mycoplasmas to erythrocytes: a model to study mycoplasma attachment to the epithelium of the host respiratory tract.

Mycoplasma pneumoniae, M. gallisepticum and M. pulmonis are pathogens of the respiratory tract. Their adherence to the host tissue is a prerequisite for manifestation of the disease. The attachment occurs between membrane components of the mycoplasmas and the host cells. In the attachment of M. pneumoniae and M. gallisepticum, binding sites of a protein nature of the mycoplasma membranes interact primarily with sialic acid residues of sialoglycoproteins of the host cell membranes. The latter was clearly indicated in studies on the pathogenic strain of M. pneumoniae and its nonpathogenic nonhemadsorbing mutants, and by the assessment of the direct binding of glycophorin [the major sialoglycoprotein of human red blood cells (RBC)] and other sialoglycoproteins to M. pneumoniae and M. gallisepticum. The components involved in the interaction of M. pulmonis with the host cells are not as well characterized, since the attachment is not affected by proteolytic treatment of the mycoplasmas, nor by removal of sialic acid residues from the host cell membranes. The attachment of the mycoplasmas to the host cells also occurs with nonviable organisms and can, in addition, by reproduced by isolated membranes. The binding sites of M. pneumoniae and M. gallisepticum were partially purified by affinity chromatography, using the high affinity of the binding sites for glycophorin. By this procedure the membranes were solubilized with detergents and chromatographed through glycophorin attached to Sepharose 4B as an affinity matrix. The binding sites retained the high affinity for glycophorin and bound to RBC membranes. Are the binding sites distributed throughout the membrane? Since the binding of the mycoplasma is via a polar structure (the tip or bleb), one may suggest that these structures harbor them. Experimental evidence for their distribution is being sought.

Adhesiveness↗
PubMed1995

Hemagglutination and proteoglycan binding by the Lyme disease spirochete, Borrelia burgdorferi.

The ability of the Lyme disease spirochete to attach to host components may contribute to its ability to infect diverse tissues. We present evidence that the Lyme disease spirochete expresses a lectin activity that promotes agglutination of erythrocytes and bacterial attachment to glycosaminoglycans. Among a diverse collection of 21 strains of Lyme disease spirochete, hemagglutinating activity was easily detected in all but 3 strains, and these three strains were noninfectious. The ability to agglutinate erythrocytes was associated with the ability of the spirochete to bind to the sulfated polysaccharide dextran sulfate and to mammalian cells. Soluble dextran sulfate was a potent inhibitor of both hemagglutination and attachment to mammalian cells, while dextran had no effect on either activity, suggesting that dextran sulfate may inhibit attachment by mimicking host cell glycosaminoglycans. Consistent with this, the spirochete bound to immobilized heparin, and soluble heparin inhibited bacterial adhesion to mammalian cells. The bacterium did not bind efficiently to Vero cells treated with heparinase or heparitinase or to mutant CHO cell lines that are deficient in proteoglycan synthesis. Sulfation of glycosaminoglycans was critical for efficient bacterial recognition, as Vero cells treated with an inhibitor of sulfation, or a mutant CHO cell line that produces undersulfated heparan sulfate, did not mediate maximal spirochetal binding. Binding of the spirochete to extracellular matrix also appeared to be dependent upon this attachment pathway. These findings suggest that a glycosaminoglycan-binding activity which can be detected by hemagglutination contributes to the attachment of the Lyme disease spirochete to host cells and matrix.

Animals↗
PubMed1991

Role of La Crosse virus glycoproteins in attachment of virus to host cells.

Data presented in this report demonstrate that the initial event of La Crosse virus (LACV) infection of cells is probably the interaction of viral glycoproteins with specific cellular receptor sites. We have shown that LACV glycoprotein G1 binds, in a dose-dependent manner, to continuous vertebrate and mosquito cell lines, but not to mosquito midguts isolated ex vivo. This binding can be inhibited by the pretreatment of cells with excess homologous glycoprotein but not with excess heterologous LACV glycoprotein. In contrast, we have shown that LACV glycoprotein G2 binds to the continuous mosquito cell line and vector midgut cells, but not to vertebrate cells. LACV infection of vertebrate cells can be inhibited by treatment of cells with purified G1, while infection in mosquito cells can be reduced by treatment of cells with a combination of G1 and G2. The results suggest that G1 is the viral attachment protein (VAP) for vertebrate cells, and that G2 serves the same purpose for mosquito midgut cells. We speculate that the protease-resistant G2 molecule may have evolved to serve as the VAP in the midgut under conditions in which G1 might be altered or removed from the virus envelope, and thus is essential to the evolution and maintenance of vertebrate-invertebrate transmission cycles.

Animals↗
PubMed1999

Isolation of additional bacteriophages with genomes of segmented double-stranded RNA.

Eight different bacteriophages were isolated from leaves of Pisum sativum, Phaseolus vulgaris, Lycopersicon esculentum, Daucus carota sativum, Raphanus sativum, and Ocimum basilicum. All contain three segments of double-stranded RNA and have genomic-segment sizes that are similar but not identical to those of previously described bacteriophage phi6. All appear to have lipid-containing membranes. The base sequences of some of the viruses are very similar but not identical to those of phi6. Three of the viruses have little or no base sequence identity to phi6. Two of the viruses, phi8 and phi12, contain proteins with a size distribution very different from that of phi6 and do not package genomic segments of phi6. Whereas phi6 attaches to host cells by means of a pilus, several of the new isolates attach directly to the outer membrane. Although the normal hosts of these viruses seem to be pseudomonads, those viruses that attach directly to the outer membrane can establish carrier states in Escherichia coli or Salmonella typhimurium. One of the isolates, phi8, can form plaques on heptoseless strains of S. typhimurium.

Bacteriophages↗