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U Vergara

Publications and source records attributed to U Vergara.

17 recordsLinked to original sources
PubMed2003

Action of Trypanosoma rangeli in infections with virulent Trypanosoma cruzi populations.

In experimental murine infections with Trypanosoma rangeli it has been observed development immune response to Trypanosoma cruzi. The aim of the present work was to analyze the result of antigenic stimuli and the protective effect with T. rangeli in T. cruzi infections. Mice groups immunized with metacyclic trypomastigotes of T. rangeli (Choach -2V strain), derived from haemolymph and salivary gland and reinfected with T. cruzi virulent populations (Tulahuen strain, SA strain and Dm28c clone) from infected in vitro cells, showed decrease severity of disease outcomes, low parasitemia levels and 100% survival of all mice immunized, in comparison with groups infected only with T. cruzi populations, which demonstrated tissue affection, high parasitemia levels and the death of all animals. The above mentioned data contribute to understand the biological behaviour of T. cruzi and T. rangeli and their interaction with vertebrate host.

Animals↗
PubMed1999

[T lymphocyte immunological response to different antigenic fractions of Mycobacterium bovis in juvenile chronic polyarthritis].

BACKGROUND: The possible relationship of stress or heat-shock proteins (hsp) with the pathogenesis of autoimmune disease has been intensely studied recently. In adult rheumatoid arthritis, a bacterial hsp (65 kDa hsp from Mycobacterium tuberculosis or bovis) would have a cross reactivity with a hsp of ARTICULAR cartilage. AIM: To assess the cellular immune response to the 65 kA hsp from M Bovis in children. PATIENTS AND METHODS: The proliferative response of peripheral mononuclear cells of 20 children with juvenile chronic polyarthritis and 20 healthy controls, against the 65 kDa hsp and other antigenic fractions from M bovis, was studied. RESULTS: Patients with juvenile chronic polyarthritis had a intense reaction against 65 kDa fraction and a second fraction located between 32.5 and 27.5 kDa. Patients with a prolonged evolution of the disease (more than five years), reacted preferentially to an antigenic segment located between 32.5 and 27.5 kDa and those with a shorter evolution did so with an antigen of 27.5-18.5 kDa. CONCLUSIONS: These results support the hypothesis that 65 kDa hsp from M bovis is involved in the pathogenesis of chronic juvenile polyarthritis and suggest that patients with short or prolonged evolutions of the disease would react to different antigenic fractions.

Adolescent↗
PubMed1996

Serum antibodies to Trypanosoma cruzi antigens in Atacameños patients from highland of northern Chile.

In the present work we have investigated the serum antibody spectrum to parasite antigens involved in human T. cruzi infection. Analysis was performed by conventional serology (IHA, IFAT and ELISA), complement-mediated lysis, anti-gal antibody assay and reactivity against recombinant and synthetic peptides and metacyclic antigens by immunowestern-blotting. All the sera showed a significant reactivity in IHA, IFAT and ELISA. We found that 84.2% of the sera showed lytic activity and thirty serum samples (78.9%) which showed a lytic activity higher than 50%, also showed anti-gal antibodies at serum dilutions higher than 1:1,600. Ninety-four percent of sera reacted with one or more of the recombinant DNA clones and 97.3% reacted with one or more of the synthetic peptides. A pool of serum samples with a lytic activity higher than 75% were able to produce 60% to 78% inhibition of cell invasion. Thirty-six of the serum samples (94.7%) were able to react by immunowestern blotting with a T. cruzi metacyclic antigen with molecular size of 70 kDa. The results obtained give preliminary information about the humoral immune response and the possible role of antibodies in protection against T. cruzi infection of chronic patients from the highlands of Chile.

Adolescent↗
PubMed1993

[The diagnosis of chronic Chagas disease using recombinant antigens of Trypanosoma cruzi].

A panel of eight recombinant Trypanosoma cruzi antigens was used to study the IgG reactivity of sera proceeding from 151 patients with chronic Chagas disease. These samples were reactive against T Cruzi epimastigotes by immunofluorescence and enzyme linked assays. A dot blot assay was performed to evaluate the reactivity against recombinant clones 1, 2, 13, 26, 30, 36, 54 and SAPA (Shed Acute Phase Antigen). Ninety six percent of samples reacted against one or more of these antigens. The most frequently recognized proteins were clones 1, 2, 13, 36 and 26 with 90, 89, 76, 71 and 66 percent of reactivity respectively. Less than 50% of sera reacted against clones 30, 54 and SAPA. Sera from symptomatic patients had a significantly higher frequency of reactivity against clone SAPA than those from asymptomatic patients. This difference suggests that a high reactivity against clone SAPA may be related to acute infections and symptoms. No significant relationship could be established between specific recombinant clone recognitions and particular clinical forms of the disease (cardiological or digestive). It is concluded that these recombinant proteins may become a good tool for the evaluation of the immune response of patients infected with T. cruzi.

Adolescent↗
PubMed1992

Evaluation of an enzyme-linked immunosorbent assay for the diagnosis of Chagas' disease using synthetic peptides.

An enzyme-linked immunosorbent assay (ELISA) has been developed to detect antibodies in human sera to synthetic peptides derived from the repeating amino acid sequence in recombinant Trypanosoma cruzi antigens. Sixty serum samples from patients with chronic Chagas' disease were used to determine the reactivity against the synthetic repeat peptides derived from clones 1, 2, 30, 36, and shed acute phase antigen (SAPA). Ninety-eight percent of the samples had detectable antibodies to one or more of the synthetic peptides at titers greater than 1:100. The percentage of reactive sera increased from 28% with peptide SAPA to 93% with peptide 2. The exposure of patients to T. cruzi was reflected in indirect immunofluorescent antibody titers to fixed epimastigotes. Comparisons between ELISA and immunoradiometric assay data indicated that both tests were of approximately equal sensitivity.

Amino Acid Sequence↗
PubMed1992

Immunodetection of antibodies in sera from symptomatic and asymptomatic Chilean Chagas' disease patients with Trypanosoma cruzi recombinant antigens.

A panel of eight Trypanosoma cruzi antigens produced by recombinant DNA techniques was used to compare the reactivity of IgG specificities in the sera from 45 chronic Chagas' disease patients with different clinical symptoms (cardiac disease, gastrointestinal lesions, and combined syndrome) with those present in the sera from 55 asymptomatic patients in Chile. All of the serum samples were first characterized for antibody to T. cruzi epimastigotes by immunofluorescence assay. All of the Chagas' disease sera were reactive, but none of five healthy controls whose sera were also tested had antibodies against the fixed parasites. A dot-blot assay was then performed to evaluate the serum reactivity against recombinant DNA clones 1, 2, 13, 26, 30, 36, 54, and SAPA (shed acute phase antigen). These recombinant antigens were recognized by a large proportion of the sera collected from the Chilean patients. Ninety-five percent of the serum samples reacted with one or more of the recombinant clones. Analysis of the reactivity with individual fusion proteins showed that 88% of these sera reacted with clones 1 and 2, and 78% reacted with clone 13. Differences in reactivity to clones number 13, 30, and SAPA were observed when symptomatic and asymptomatic patients were compared. These differences in reactivity were statistically significant (P less than 0.01) according to Fisher's exact test.

Adolescent↗
PubMed1991

Assay for detection of Trypanosoma cruzi antibodies in human sera based on reaction with synthetic peptides.

Synthetic peptides modelled according to the amino acid sequences derived from the repeated domains of five Trypanosoma cruzi antigens were used in an immunoradiometric assay to detect antibodies appearing after natural human infections. An enzyme-linked immunosorbent assay and an indirect immunofluorescence assay performed with a complex antigenic mixture from parasites were used as controls. The results indicate that the synthetic peptides were recognized by a large proportion of serum samples collected from 34 patients with Chagas' disease in Chile and point to their possible use in diagnosis.

Adolescent↗
PubMed1989

[The 4th complement factor (C4) and t haplotypes in wild mice].

Five different lines of tailless mice bearing different t recessive haplotypes (tAn, tMo, tRa, tLa and tQu) have been established in our laboratory and maintained in combination with the brachury chromosome (T). These t haplotypes were derived from widely separated Chilean wild mouse populations. The immunoelectrophoretic typing for Ss and Slp isotypic variants of C4 showed that all lines had the Ss-High. Slp-negative phenotype suggesting that the t haplotypes might be associated with similar S regions of the major histocompatibility system of the mouse.

Animals↗
PubMed1987

Mechanism of escape of exoerythrocytic forms (EEF) of malaria parasites from the inhibitory effects of interferon-gamma.

We have studied the mechanism of inhibition by interferon-gamma (IFN-gamma) of the development of exoerythrocytic forms (EEF) of Plasmodium berghei in the livers of rats. At the time corresponding to the maximum development of EEF (44 hr after injection of sporozoites), the livers of the IFN-gamma-treated rats contained less parasite DNA as compared with controls. Twenty-four to 72 hr later, the livers of both groups of animals were free of parasites; that is, IFN-gamma treatment does not delay the development of the EEF. The decrease in parasite DNA observed in the IFN-gamma-treated rats was due to a diminution in the number, but not the size, of EEF. It appears, therefore, that treatment with the lymphokine either destroys the parasites or does not affect their replication. To study the mechanism of resistance to IFN-gamma of a small population of EEF, we subjected the parasites to four cycles of selection by IFN-gamma. The parasites from the "selected" and "nonselected" populations were equally susceptible to inhibition by IFN-gamma, indicating that the escape from IFN-gamma activity is not inherited.

Animals↗
PubMed1985

Multiple non-repeated epitopes on the circumsporozoite protein of Plasmodium knowlesi.

The Plasmodium knowlesi circumsporozoite (CS) protein contains a repetitive immunodominant epitope. Here we show that the serum of rabbits repeatedly immunized with P. knowlesi sporozoites contains antibodies which bind to immobilized synthetic peptides ('C2', 'N2', and 'charged') representing two different polar regions of the CS polypeptide. These reactions are specific since the binding is inhibited only by the homologous peptides. Antisporozoite antibodies were isolated from the rabbit serum by affinity chromatography on Sepharose beads coupled to two synthetic peptides, 'C2' and 'charged'. Both purified antibodies recognized the CS protein and the intracellular precursors as shown by Western blotting analysis using sporozoite extracts. These results demonstrate that the corresponding areas of the native CS molecule are immunogenic, accessible to interaction with antibody, and therefore constitute potential targets for vaccine development. In addition, the present findings confirm the published amino acid sequence of a large portion of the CS protein which has been deduced from the nucleotide sequence of the corresponding gene.

Amino Acid Sequence↗
PubMed1985

Conserved group-specific epitopes of the circumsporozoite proteins revealed by antibodies to synthetic peptides.

The immunogenic properties of sporozoites are associated mainly with the circumsporozoite (CS) protein that covers the surface of mature sporozoites. This stage-specific protein has an immunodominant region with repetitive epitopes. Rabbits that are repeatedly immunized with sporozoites of Plasmodium knowlesi, a monkey malaria parasite, also recognize two synthetic peptides (N2 and C2) representing other polar domains of the CS protein. We show in this report that antibodies to the N2 and C2 synthetic peptides react not only with P. knowlesi but also with conserved regions of the surface membrane of other human, monkey, and rodent (but not avian) malaria sporozoites. Moreover, antibodies to N2 partially neutralize the infectivity of sporozoites of P. berghei, a rodent malaria parasite. In contrast, antibodies to synthetic peptides representing the repetitive epitope of P. knowlesi were strictly species specific.

Animals↗
PubMed1984

tch, tsf and tte: three independently isolated t haplotypes in the mouse.

Three recessive lethal t haplotypes have been independently isolated from widely separated Chilean wild mouse populations. They do not complement one another, have similar transmission ratios and suppress recombination. We do not know at present if they belong to a previously described complementation group or if they define a new one.

Animals↗
PubMedDate not supplied

A novel design of peptide immunogens: synthetic peptide with a reversible handle for the attachment to protein carriers.

A novel design of peptide antigen suitable for the preparation of peptide-based antibody is described. The peptide is synthesized in a special benzhydrylamine (p-acyloxybenzhydrylamine) resin that contains two detachable sites, both of which are stable to the mild SN2 deprotection of the side chains that allows the deprotected peptide to remain attached to the resin support. Release of the peptide is achieved by methylaminolysis in a volatile solvent that produces a deprotected peptide with a detachable p-hydroxybenzhydrylamine handle for the linkage to the protein carrier via an azo bond. The peptidyl handle is detachable under a mild acidolytic condition to generate the desirable peptide. A 17-residue peptide from the circumsporozoite proteins of the human malaria parasite, Plasmodium flaciparum, was tested in this approach to prepare antibodies, and its results were compared with the conventional approach using glutaraldehyde as the crosslinking reagent. Specific antibodies obtained from this approach were found to be reactive with the peptide and the cognate protein. Our results show that this design is useful and convenient to generate site-specific peptide-based antibodies for laboratory use.

Amino Acid Sequence↗