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A M Cevallos

Publications and source records attributed to A M Cevallos.

14 recordsLinked to original sources
PubMed2006

Taxonomic study of the Phyllosoma complex and other triatomine (Insecta: Hemiptera: Reduviidae) species of epidemiological importance in the transmission of Chagas disease: using ITS-2 and mtCytB sequences.

The purpose of this work was to clarify the taxonomy and phylogenetic relationship of the Phyllosoma complex and other important vectors in Mexico. The internal transcribed spacer 2 (ITS-2) of rDNA and the cytochrome B gene of mtDNA (mtCytB) were analyzed for the following species of triatomine: Triatoma bassolsae, T. longipennis, T. mazzottii, T. mexicana, T. pallidipennis, T. picturata, and T. phyllosoma belonging to the Phyllosoma complex, as well as T. dimidiata, T. rubida, T. infestans, and Rhodnius prolixus. The results obtained with the analysis of the ITS-2 sequences showed that the Phyllosoma complex species could not be phylogenetically separated, since T. bassolsae and T. pallidipennis, as well as T. phyllosoma and T. mazzottii were indistinguishable. In contrast, the mtCytB gene separates each one of these triatomine species. The results support the proximity of all seven species currently included in the Phyllosoma complex as well as the exclusion of T. dimidiata. For the first time T. lecticularia and T. rubida were analyzed and were also shown to be related to the Phyllosoma complex.

Animals↗
PubMed2000

Molecular cloning and expression of a gene encoding Cryptosporidium parvum glycoproteins gp40 and gp15.

Cryptosporidium parvum is a significant cause of diarrheal disease worldwide. The specific molecules that mediate C. parvum-host cell interactions and the molecular mechanisms involved in the pathogenesis of cryptosporidiosis are unknown. In this study we have shown that gp40, a mucin-like glycoprotein, is localized to the surface and apical region of invasive stages of the parasite and is shed from its surface. gp40-specific antibodies neutralize infection in vitro, and native gp40 binds specifically to host cells, implicating this glycoprotein in C. parvum attachment to and invasion of host cells. We have cloned and sequenced a gene designated Cpgp40/15 that encodes gp40 as well as gp15, an antigenically distinct, surface glycoprotein also implicated in C. parvum-host cell interactions. Analysis of the deduced amino acid sequence of the 981-bp Cpgp40/15 revealed the presence of an N-terminal signal peptide, a polyserine domain, multiple predicted O-glycosylation sites, a single potential N-glycosylation site, and a hydrophobic region at the C terminus, a finding consistent with what is required for the addition of a GPI anchor. There is a single copy of Cpgp40/15 in the C. parvum genome, and this gene does not contain introns. Our data indicate that the two Cpgp40/15-encoded proteins, gp40 and gp15, are products of proteolytic cleavage of a 49-kDa precursor protein which is expressed in intracellular stages of the parasite. The surface localization of gp40 and gp15 and their involvement in the host-parasite interaction suggest that either or both of these glycoproteins may serve as effective targets for specific preventive or therapeutic measures for cryptosporidiosis.

Amino Acid Sequence↗
PubMed2000

Mediation of Cryptosporidium parvum infection in vitro by mucin-like glycoproteins defined by a neutralizing monoclonal antibody.

The protozoan parasite Cryptosporidium parvum is a significant cause of diarrheal disease worldwide. Attachment to and invasion of host intestinal epithelial cells by C. parvum sporozoites are crucial steps in the pathogenesis of cryptosporidiosis. The molecular basis of these initial interactions is unknown. In order to identify putative C. parvum adhesion- and invasion-specific proteins, we raised monoclonal antibodies (MAbs) to sporozoites and evaluated them for inhibition of attachment and invasion in vitro. Using this approach, we identified two glycoproteins recognized by 4E9, a MAb which neutralized C. parvum infection and inhibited sporozoite attachment to intestinal epithelial cells in vitro. 4E9 recognized a 40-kDa glycoprotein named gp40 and a second, >220-kDa protein which was identified as GP900, a previously described mucin-like glycoprotein. Glycoproteins recognized by 4E9 are localized to the surface and apical region of invasive stages and are shed in trails from the parasite during gliding motility. The epitope recognized by 4E9 contains alpha-N-acetylgalactosamine residues, which are present in a mucin-type O-glycosidic linkage. Lectins specific for these glycans bind to the surface and apical region of sporozoites and block attachment to host cells. The surface and apical localization of these glycoproteins and the neutralizing effect of the MAb and alpha-N-acetylgalactosamine-specific lectins strongly implicate these proteins and their glycotopes as playing a role in C. parvum-host cell interactions.

Animals↗
PubMed1999

Detection of anti-colon antibodies in inflammatory bowel disease using human cultured colonic cells.

BACKGROUND: Investigation of anti-colon antibodies may be simplified if a sensitive method and homogeneous source of antigen were available. AIMS: To examine the anti-colon antibody response using human colonic carcinoma cell lines as antigen. SUBJECTS: Patients with inflammatory bowel disease and other gastrointestinal disorders and healthy controls were studied. METHODS: Comparative enzyme linked immunosorbent assays (ELISAs) were performed to assess the value of whole Caco-2, HT-29, and LS-180 cells as antigen. The antigenic determinants of the immune response were characterised by western blot analysis. RESULTS: Sera demonstrated immunoreactivity against each of the cell lines, but different epitopes were recognised. Applying whole Caco-2 cells as antigen in an ELISA, the prevalence of anti-colon antibodies was significantly greater in patients with ulcerative colitis (36%) than Crohn's disease (13%), other gastrointestinal disorders (13%) and healthy controls (0) (p<0. 05). The immune response was not associated with one predominant antigen. CONCLUSIONS: Fixed whole cell ELISA is a simple and feasible method for studying the anti-colon antibody response. This response is non-specific, being directed against multiple antigens, and is likely to be an epiphenomenon of inflammatory bowel disease, more so for ulcerative colitis than Crohn's disease.

Adolescent↗
PubMed1999

Generation of a polyclonal Fab phage display library to the protozoan parasite Cryptosporidium parvum.

We had developed a technology for creation of recombinant polyclonal antibody libraries, standardized perpetual mixtures of polyclonal whole antibodies for which the genes are available and can be altered as desired. We report here the first phase of generating a polyclonal antibody library to Cryptosporidium parvum, a protozoan parasite that causes severe disease in AIDS patients, for which there is no effective treatment. BALB/c mice, immunized by neonatal oral infection with oocysts followed by intraperitoneal immunization with a sporozoite/oocyst preparation of C. parvum, were used for construction of a Fab phage display library in a specially-designed bidirectional vector. This library was selected for reactivity to an oocyst/sporozoite preparation, and was shown to be antigen-specific and diverse. Following mass transfer of the selected variable region gene pairs to appropriate mammalian expression vectors, such anti-C. parvum Fab phage display libraries could be used to develop chimeric polyclonal antibody libraries, with mouse variable regions and human constant regions, for passive immunotherapy of C. parvum infection.

Animals↗
PubMed1998

Cryptosporidium: molecular basis of host-parasite interaction.

Host-parasite interactions occur at a number of stages during the process of infection with Cryptosporidium. Until recently, very little was known about the molecular basis of these interactions or of specific parasite and host molecules involved in them. Within the past decade significant advances have been made in our understanding of Cryptosporidium host-parasite interactions and in identifying molecules involved in them. However, with most interactions the story is far from complete and a number of gaps remain to be filled. This chapter reviews the existing knowledge of the molecular basis of various host-parasite interactions and of specific molecules that may be involved in them, and identifies areas in which further investigation is necessary. Identification of these molecules and elucidation of molecular mechanisms underlying the host-parasite interaction are of vital importance in developing strategies to combat cryptosporidiosis by targeted chemo- and immunotherapy.

Animals↗
PubMed1994

Phenotypic and genotypic variation in Giardia lamblia isolates during chronic infection.

Two Giardia isolates were axenised in vitro after recovery by duodenal aspiration from a man with hypo-gamma globulinaemia and chronic giardiasis, before and after three unsuccessful courses of metronidazole. In vitro drug sensitivity assays showed that the pretreatment isolate was sensitive to metronidazole with minimum inhibitory concentration (MIC) and dose that inhibited growth by 50% (ED50) values of 0.1 and 0.03 mumol/l, respectively. The post-treatment isolate was 20-fold more resistant (MIC and ED50 4.3 and 0.58 mumol/l, respectively). Differences between these isolates were also found in the surface protein profiles after radioiodination, metabolic labelling patterns with 35S-methionine, malic enzyme isoenzyme patterns, and by DNA fingerprinting with a M-13 bacteriophage probe. The phenotypic and genotypic differences between the pretreatment and post-treatment isolates suggest that we have isolated two different strains from the same patient and that treatment with metronidazole resulted in selection of the more resistant strain.

Adult↗
PubMed1993

Impaired IgA response to Giardia heat shock antigen in children with persistent diarrhoea and giardiasis.

The serum antibody response in Gambian children with persistent diarrhoea and giardiasis has been studied. Total serum IgG, IgA, and IgM concentrations were increased in these patients as compared with controls from the same area. Determination of the concentrations of Giardia specific antibodies by enzyme linked immuno adsorbent assay (ELISA), however, revealed that only IgM was raised while those of IgA and IgG were similar to the controls. Analysis of the antigenic determinants of the IgG and IgA responses by immunoblotting showed that patients with chronic infection unlike those who clear the infection have no IgA response to a 57 kDa Giardia heat shock antigen. The association of high concentrations of Giardia specific IgM, low concentrations of Giardia specific IgA and IgG and inability to clear the infection suggests that the switch from an IgM to an IgG or IgA response is inefficient.

Animals↗
PubMed1992

An immunodominant antigen of Giardia lamblia is a heat shock protein.

In this study we demonstrate that an immunodominant antigen of Giardia lamblia is a heat shock protein. The expression of the antigen was induced not only by heat shock but also when Giardia trophozoites were placed in media more closely resembling the environment in the host, indicating that this antigen may play an important role in host-parasite interactions.

Animals↗
PubMed1991

Prevalence and treatment of giardiasis in chronic diarrhoea and malnutrition.

To determine the prevalence of giardiasis in Gambian children with chronic diarrhoea and to assess their response to treatment, 31 children with chronic diarrhoea and malnutrition were investigated for giardiasis using a combination of serology (specific antigiardia IgM antibody) and microscopy of faeces and jejunal biopsy specimens. Fourteen of 31 children with chronic diarrhoea had giardiasis compared with only four of 33 healthy age and sex matched control children. Four of 15 malnourished children without diarrhoea were giardia positive. Twenty-three children with chronic diarrhoea were reinvestigated after treatment with metronidazole; giardia was found in 11 of them. These results show that giardia is highly prevalent in children with chronic diarrhoea and malnutrition and that the infection does not respond to standard therapeutic measures.

Animals↗
PubMedDate not supplied

Antibodies to gut protozoa in commercial immunoglobulin preparations.

Using parasite agglutination, indirect immunofluorescence, enzyme-linked immunosorbent assay, and immunoblotting, Giardia lamblia specific antibody was detected in 5 commercially available immunoglobulin (IgG) preparations. IgG antibodies to Entamoeba histolytica were either present in very low titre or were absent. Immunoblotting showed that anti-G. lamblia antibodies were detected towards a range of Giardia proteins, 25-200 kDa. These findings raise the possibility that pooled human IgG preparations could be evaluated in the treatment of chronic giardiasis which is refractory to conventional therapy.

Agglutination↗
PubMedDate not supplied

Evaluation of specific serum anti-Giardia IgM antibody response in diagnosis of giardiasis in children.

Diagnosis of Giardia intestinalis infection is usually made by examination of stool specimens and/or by more invasive methods such as microscopy of duodenal juice or small bowel mucosal biopsies. Serological diagnostic methods have been developed but have not been evaluated in children. In this study specific anti-Giardia immunoglobulin (Ig) M, IgG and IgA antibody titres were measured by enzyme-linked immunosorbent assay. Giardia parasites were sought in jejunal mucosal biopsies and in faeces from 72 children in The Gambia, West Africa; 50 jejunal biopsies, 271 stool samples and 95 serum samples were examined for evidence of Giardia infection. As a diagnostic test, a raised specific anti-Giardia IgM antibody titre (greater than or equal to 1:800) had a sensitivity of 63% and specificity of 93%, with a positive predictive value of 85% and a negative predictive value of 81%. There was poor correlation between positive microscopical identification of Giardia and elevated specific anti-Giardia IgG or IgA antibody titres in children on admission to the study. Elevated serum anti-Giardia IgM, however, was correlated well with active Giardia infection and may prove useful in epidemiological studies of giardiasis in developing countries.

Animals↗