PubMed Health⌕ Search

Biomedical subjects

E Medina-Acosta

Publications and source records attributed to E Medina-Acosta.

18 recordsLinked to original sources
PubMed2003

Egg yolk anti-BfpA antibodies as a tool for recognizing and identifying enteropathogenic Escherichia coli.

Enteropathogenic Escherichia coli (EPEC) is a major aetiological agent of childhood diarrhoea in developing countries. The structural repeating protein A subunit, BfpA, found in the bundle-forming pilus, is one of the virulent factors for EPEC pathogenesis. Recombinant BfpA in laying hens elicited sustained and vigorous antibody production. Immunoglobulin Y (IgY) anti-BfpA antibodies were recovered from egg yolk, purified and characterized. Immunoadsorption with whole extracts of the isogenic E. coli EPEC adherence factor (EAF) strain that lacks BfpA rendered the resulting IgY preparations capable of: (a) recognizing purified or recombinant BfpA proteins in a dose-dependent fashion; (b) blocking the colonization of HeLa cells by EPEC EAF+, in vitro; (c) specifically identifying E. coli bearing EAF+; and (d) inhibiting the growth of E. coli EAF+ but not the EAF strain. IgY anti-BfpA is potentially useful as a specific, low-cost immunobiological reagent to screen human faecal specimens for the presence of EPEC.

Animals↗
PubMed2001

RNAIII inhibiting peptide (RIP) inhibits agr-regulated toxin production.

Staphylococcal enterotoxins (SEs) are emetic toxins that cause food poisoning. SEs also function as powerful pyrogenic toxin superantigens that stimulate non-specific T-cell proliferation. Together with the hemolysins, SEs have been largely implicated as virulence factors in multiple infection models. Recent biochemical and genetic analyses have demonstrated that production of some of these toxins is partially regulated by quorum sensing mechanisms where proteins and peptides activate the accessory gene regulator (agr). Because toxin production is central to bacterial pathogenesis, therapeutic strategies alternative to antibiotics, and based on rational interference of the quorum sensing systems involved, are currently being developed. This approach would lead to repression of toxin production and, thus, to disease prevention. Here we provide evidence to conclude that synthetic analogs of the RNAIII inhibiting peptide (RIP) and antibodies to its target molecule TRAP function in vitro as efficient suppressors of agr-regulated exotoxin production by Staphylococcus aureus.

Antibodies↗
PubMed2000

Prevention of diseases caused by Staphylococcus aureus using the peptide RIP.

Staphylococcus aureus causes many diseases including cellulitis, keratitis, osteomyelitis, septic arthritis and mastitis. The heptapeptide RIP has been shown to prevent cellulitis in mice, which was induced by S. aureus strain Smith diffuse. Here we show that RIP can also significantly reduce the overall pathology and delay the onset of disease symptoms in several other models of S. aureus infections, including: keratitis (tested in rabbits against S. aureus 8325-4), osteomyelitis (tested in rabbits against S. aureus MS), mastitis (tested in cows against S. aureus Newbould 305, AE-1, and environmental infections) and septic arthritis (tested in mice against S. aureus LS-1). These findings substantiate that RIP is not strain specific in its inhibitory activity and that RIP is an effective inhibitor of bacterial pathology at multiple body sites following diverse routes and doses of administration. These findings strongly evidence the potential value of RIP as a chemotherapeutic agent.

Animals↗
PubMed1997

Trypanosoma cruzi in the opossum Didelphis marsupialis: a study of the correlations and kinetics of the systemic and scent gland infections in naturally and experimentally infected animals.

The genus Didelphis (Marsupialia, Didelphidae) has the unique capacity of supporting both multiplication cycles of Trypanosoma cruzi simultaneously; besides the intracellular forms, the epimastigotes can be found multiplying and differentiating abundantly in the lumen of the scent glands. The biological significance of the life cycle of T. cruzi within the scent glands of Didelphis marsupialis, as well as its contribution to the epidemiology of the disease, is presently unclear. In order to clarify the mechanisms involved in the colonization of this singular habitat by T. cruzi, as well as to understand its biological role, we have carried out a serological and parasitological follow-up of both natural and experimental infections of young and adult opossums. Although all natural infections were stable and long lasting, no infected scent glands were found, indicating that the stability of the systemic infections does not depend on the presence of flagellates in the scent gland. In 84% of the experimentally infected animals the colonization of the scent glands was preceded by a period of patent parasitemia. Parasitism of the scent glands was essentially permanent and bilateral, and its maintenance was independent of circulating parasites. Moreover, the course of the infection differed depending on the source (scent glands versus axenic culture-derived) of the metacyclic forms. Our results suggest that parasitism of the SG of D. marsupialis is most likely a secondary acquisition, a step toward independence from the insect vector, similarly to what is accepted for Trypanosoma equiperdum.

Animals↗
PubMed1994

Trans-sialidase and sialidase activities discriminate between morphologically indistinguishable trypanosomatids.

The expression of trans-sialidase and sialidase activities in the kinetoplastid protozoa was explored as a potential marker to discriminate between the morphologically indistinguishable flagellates isolated from human, insects and vertebrate reservoir hosts. By virtue of the differences observed in the ratios of these enzyme activities, a collection of 52 species and strains comprising the major taxa of these parasites could be separated into four expression types. Type-I parasites express comparable levels of both trans-sialidase and sialidase activities (Endotrypanum species and Trypanosoma lewisi). Type-II parasites express predominantly trans-sialidase activity (Trypanosoma cruzi and Trypanosoma conorhini). Type-III parasites express sialidase activity exclusively (Trypanosoma rangeli and Trypanosoma leeuwenhoeki). Type-IV parasites do not express either activity (Leishmania species and Trypanoplasma borreli). The measurement of trans-sialidase and sialidase activities thus permits the differentiation of parasites frequently found in the same insect vectors that are difficult to distinguish, such as T. cruzi and T. rangeli, or in the same sylvatic vertebrate and invertebrate hosts, such as Leishmania and Endotrypanum.

Animals↗
PubMed1994

Combined occurrence of trypanosomal sialidase/trans-sialidase activities and leishmanial metalloproteinase gene homologues in Endotrypanum sp.

Endotrypanum (order Kinetoplastida: family Trypanosomatidae) is a parasite of forest dwelling tree sloths (Edentata: genera Choleopus and Bradypus). Unique among the haemoflagellates, this protozoan has an intraerythrocytic phase in the mammalian host. Nevertheless, many striking similarities exist between Endotrypanum and the human pathogen Leishmania that make it a useful model for epidemiological and evolutionary aspects of the biology of trypanosomatids. Importantly, Endotrypanum species share both the insect vector and host reservoir with certain species of Leishmania (subgenus Viannia). Because mixed infections with Endotrypanum and Leishmania are common in sloths and, therefore, likely to occur in the sandfly vector, there is a need for adequate biochemical markers to distinguish Endotrypanum from Leishmania infections. In this paper we show that Endotrypanum promastigotes possess sialidase and trans-sialidase activities, which are absent from Leishmania, and which are not closely related to the previously described trypanosomal sialidase/trans-sialidase enzyme. We also document the occurrence in Endotrypanum of homologues of the leishmanial surface metalloproteinase gp63 genes. The combined occurrence of sialidase/trans-sialidase activities and gp63 gene homologues in a unique organism has important ramifications for both field and laboratory studies on the biology of trypanosomatids, especially those related to host infection and evolution.

Animals↗
PubMed1993

Effective immunization against cutaneous leishmaniasis with recombinant bacille Calmette-Guérin expressing the Leishmania surface proteinase gp63.

Leishmania parasites cause a spectrum of diseases that afflict the populations of 86 countries in the world. The parasites can survive within the lysosomal compartments of the host's macrophages, unless those macrophages are appropriately activated. Despite the fact that protective immunity can be induced by vaccination with crude parasite preparations, little progress has been made toward a defined vaccine for humans. In this study the gene encoding the Leishmania surface proteinase gp63 was cloned and expressed as a cytoplasmic protein in a bacille Calmette-Guérin (BCG) vaccine strain. BALB/c and CBA/J mice were inoculated with a single dose of recombinant BCG and challenged with infective Leishmania major or Leishmania mexicana promastigotes. Significant protection was observed in both mouse strains against L. mexicana and in CBA/J against L. major, whereas only a delay in L. major growth was seen in BALB/c mice. Recombinant BCG also engendered a strong protective response against challenge with amastigotes of L. mexicana, demonstrating that the induced immune response recognized the intracellular form of the parasite. The results support the view that recombinant BCG expressing gp63 may prove a useful vaccine for inducing protective cell-mediated immune responses to Leishmania species causing American cutaneous leishmaniasis.

Animals↗
PubMed1993

Inhibition of glycosylphosphatidylinositol biosynthesis in Leishmania mexicana by mannosamine.

In several Leishmania species, glycosylated inositol phospholipids exist as free lipids, as membrane protein anchors, and as the membrane-binding moieties of the lipophosphoglycans. Both the glycolipid-anchored cell surface metalloproteinase, gp63, and the lipophosphoglycans have been proposed to be involved in cell invasion. Moreover, the lipophosphoglycans have been implicated in the survival of Leishmania in the parasitophorous vacuole of the host macrophage. In this report we show that mannosamine effectively inhibits the biosynthesis of both free glycosylated inositol phospholipids and the lipophosphoglycans of Leishmania mexicana. [3H]Mannosamine is incorporated into glycosylated inositol phospholipids, but not significantly into lipophosphoglycans when added as a radiochemical tracer at a subinhibitory concentration. The reversible inhibitory effect of mannosamine may be useful for studying precursor/product relationships during the biosynthesis of free glycosylated inositol phospholipids, glycolipid anchors, and the lipophosphoglycans. The implications of these data for the mode of action of mannosamine are discussed.

Animals↗
PubMed1993

Rapid isolation of DNA from trypanosomatid protozoa using a simple 'mini-prep' procedure.

Although several methods for isolating genomic DNA from trypanosomatid protozoa exist, all are time-consuming and cumbersome. Faster, simpler and efficient protocols for preparation of DNA from these protozoa are needed to ease the screening of mutants and transfectants. We describe the use of a bacterial lysis method to isolate chromosomal DNA from a wide range of trypanosomatids. The method is based on the finding reported by He et al., who noticed that phenol/chloroform treatment of Escherichia coli cells in the presence of LiCl and Triton X-100 solubilizes plasmid DNA, while precipitating unwanted chromosomal DNA and denatured cellular proteins. In applying this lysis method to the isolation of episomal DNA from transfected trypanosomatids, we found that, unlike bacterial genomic DNA, chromosomal DNA of trypanosomatids was soluble in the phenol/chloroform/Triton/LiCl mixture. This observation prompted us to use the bacterial lysis method as a routine protocol for extraction of DNA from trypanosomatids.

Animals↗
PubMed1993

Structurally distinct genes for the surface protease of Leishmania mexicana are developmentally regulated.

gp63 is a highly abundant glycosylphosphatidylinositol (GPI)-anchored membrane protein expressed in both the promastigote and the amastigote forms of Leishmania species. In Leishmania mexicana, gp63 exists as a heterogeneous family of proteins that are differentially processed and localized during the 2 developmental stages. In this study we determined the molecular organization of the L. mexicana gp63 gene family, demonstrating that the gp63 genes fall into 3 linked families of tandemly repeated, but structurally distinct, entities designated as C1, C2 and C3. The C1 and C2 gene clusters contain 4-5 copies each, while the C3 gene may be single copy. Whilst promastigotes contain transcripts from all 3 gene classes, the intracellular amastigote only expresses detectable transcript from the C1 gene class. Moreover, the sequence of the C1 genes predicts a unique carboxy terminus substantially different from the GPI anchor addition signal sequence found in other Leishmania spp. and which has characteristics incompatible with substitution with a GPI anchor. These findings have significance for both the diversity of gp63 and for the regulation of tightly clustered, tandem gene arrays.

Amino Acid Sequence↗
PubMed1993

Crithidia fasciculata contains a transcribed leishmanial surface proteinase (gp63) gene homologue.

We have cloned and analysed a gene from the insect parasite, Crithidia fasciculata, with homology to the gp63 metalloendoproteinase gene of Leishmania. The Crithidia gene homologue is arranged as a multicopy family comprised of approximately 7 genes. The mature transcript is 4.0 kb. The predicted amino acid sequence has significant homology with Leishmania gp63s, contains a zinc-binding motif and a potential site for addition of a glycosylphosphatidylinositol anchor. Demonstration of a gp63 homologue in C. fasciculata, a monogenetic parasite, suggests that the molecule may play a role in parasite survival within the insect gut.

Amino Acid Sequence↗
PubMed1993

Evolution and expression of the Leishmania surface proteinase (gp63) gene locus.

The Leishmania surface proteinase, gp63, is the most abundant, surface-exposed protein on the promastigote form of the parasite. It is the product of a multigene family that, in some Leishmania species, shows marked heterogeneity among its members. The differential expression of structurally distinct gp63 genes shows circumstantial correlation with the differential processing and localization of the protein in the intracellular, amastigote form of Leishmania mexicana. The recent cloning and sequencing of a homologous gene in the monoxenous trypanosomatid, Crithidia fasciculata, provides a reference sequence for comparison with ten Leishmania gp63 genes sequenced to date. The amino terminal and the carboxy terminal regions of the protein sequences suggest different evolutionary histories within some of the genes. The evolutionary significance of the structure, organization, and regulation of the gp63 genes from different Leishmania species is described and speculated upon.

Amino Acid Sequence↗
PubMed1991

The interface between the Leishmania-infected macrophage and the host's immune system.

The protozoan parasite Leishmania exploits the lysosomal compartment of the macrophages of its vertebrate host. Given that the macrophage is capable of killing the parasite if supplied with the correct stimulus from the host's immune system, the successful continuation of the infection is in the balance. This paper examines certain aspects of the Leishmania/macrophage interplay, with particular emphasis on the nature of defined protective antigens, and of the interface between the infected macrophage and the host's immune system.

Animals↗
PubMed1989

Genes encoding the major surface glycoprotein in Leishmania are tandemly linked at a single chromosomal locus and are constitutively transcribed.

The major surface glycoprotein of Leishmania, gp63, is encoded by a small multi-gene family of tandemly linked genes which map to a single chromosome. For Leishmania major, there are five 3.1 kilobasepair (kb) direct repeat units which include a 1.8-kb open reading frame and a 1.3-kb intergenic or spacer region. In addition, there is a single gene copy linked as a direct repeat but separated from the tandem array of gp63 genes by about 8 kb. The restriction enzyme map of the repeat unit is highly conserved among the gene copies. The regions which flank the tandemly repeated genes diverge outside of the 3.1-kb repeat unit. Transcription of the gp63 gene locus is constitutive as the 3-kb transcript was present in promastigotes as well as in amastigotes. A minor 6-kb gp63 gene transcript was also detected in Northern blot analysis which could signify the transcription of the genes as a polycistronic or multigene precursor RNA.

Animals↗
PubMed1989

The promastigote surface protease (gp63) of Leishmania is expressed but differentially processed and localized in the amastigote stage.

The expression, processing and localization of the promastigote surface glycoprotein, gp63, in the amastigote form of Leishmania mexicana was examined. Metabolically labeled protein was immunoprecipitated from promastigotes and amastigotes. The isolated proteins were subjected to deglycosylation and partial peptide mapping. The cleavage products generated migrated similarly in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicating that the proteins were closely related. The majority of gp63 in amastigotes was inaccessible to surface-labeling procedures, and lacked the phosphatidylinositol membrane anchor. Immunolocalization of this subpopulation of gp63 revealed it to be present within the parasite's flagellar pocket. Despite the relative paucity of 'membrane-form' gp63, isolation and analysis of surface proteins from lesion amastigotes indicated that gp63 was the most abundant protein on the amastigote surface.

Animals↗
PubMedDate not supplied

Genetic data showing evolutionary links between Leishmania and Endotrypanum.

Striking similarities at the morphological, molecular and biological levels exist between many trypanosomatids isolated from sylvatic insects and/or vertebrate reservoir hosts that make the identification of medically important parasites demanding. Some molecular data have pointed to the relationship between some Leishmania species and Endotrypanum, which has an important epidemiological significance and can be helpful to understand the evolution of those parasites. In this study, we have demonstrated a close genetic relationship between Endotrypanum and two new leishmanial species, L. (V.) colombiensis and L. (V.) equatorensis. We have used (a) numerical zymotaxonomy and (b) the variability of the internal transcribed spacers of the rRNA genes to examine relationships in this group. The evolutionary trees obtained revealed high genetic similarity between L. (V.) colombiensis, L. (V.) equatorensis and Endotrypanum, forming a tight cluster of parasites. Based on further results of (c) minicircle kDNA heterogeneity analysis and (d) measurement of the sialidase activity these parasites were also grouped together.

Animals↗