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S F Breniere

Publications and source records attributed to S F Breniere.

17 recordsLinked to original sources
PubMed2003

Impact of number of isoenzyme loci on the robustness of intraspecific phylogenies using multilocus enzyme electrophoresis: consequences for typing of Trypanosoma cruzi.

Thirty-one stocks of Trypanosoma cruzi, the agent of Chagas disease, representative of the genetic variability of the 2 principal lineages, that subdivide T. cruzi, were selected on the basis of previous multilocus enzyme electrophoresis analysis using 21 loci. Analyses were performed with lower numbers of loci to explore the impact of the number of loci on the robustness of the phylogenies obtained, and to identify the loci that have more impact on the phylogeny. Analyses were performed with numerical (UPGMA) and cladistical (Wagner parsimony analysis) methods for all sets of loci. Robustness of the phylogenies obtained was estimated by bootstrap analysis. Low numbers of randomly selected loci (6) were sufficient to demonstrate genetic heterogeneity among the stocks studied. However, they were unable to give reliable phylogenetic information. A higher number of randomly selected loci (15 and more) were required to reach this goal. All loci did not convey equivalent information. The more variable loci detected a greater genetic heterogeneity among the stocks, whereas the least variable loci were better for robust clustering. Finally, analysis was performed with only 5 and 9 loci bearing synapomorphic allozyme characters previously identified among larger samples of stocks. A set of 9 such loci was able to uncover both genetic heterogeneity among the stocks and to build robust phylogenies. It can therefore be recommended as a minimum set of isoenzyme loci that bring maximal information for all studies aiming to explore the phylogenetic diversity of a new set of T. cruzi stocks and for any preliminary genetic typing. Moreover, our results show that bootstrap analysis, like any statistics, is highly dependent upon the information available and that absolute bootstrap figures should be cautiously interpreted.

Animals↗
PubMed1998

Smallness of the panmictic unit of Triatoma infestans (Hemiptera: Reduviidae).

The population genetic structure of Triatoma infestans (Klug), the principal vector of the causative agent of Chagas disease in Bolivia, was investigated by enzyme electrophoresis at 15 loci, of which 3 were polymorphic. A total of 1,286 adults and nymphs was collected from 19 localities of the Cochabamba (high endemicity) and La Paz (low endemicity) departments. Previous results were confirmed, including a low level of polymorphism (0.20), low genetic distance between geographic areas, and a population structure compatible with an isolation by distance model. However, a high proportion (26.3%) of the surveyed localities showed a significant excess of homozygotes, disputing previous conclusions that considered the village as the probable panmictic unit. The excess of homozygotes was reduced when smaller subunits, such as individual houses or chicken coops, were considered, indicating a Wahlund effect.

Animals↗
PubMed1997

PCR-based diagnosis for Chagas' disease in Bolivian children living in an active transmission area: comparison with conventional serological and parasitological diagnosis.

A large field study has been performed in the Cochabamba region of Bolivia with the aim of comparing the polymerase chain reaction (PCR) with other diagnostic methods for Chagas' disease. The amplification of Trypanosoma cruzi-specific kinetoplast DNA sequences in blood samples was compared with classical serological methods, specific IgM detection and direct parasite visualization for 268 school children in a single village where Chagas' disease transmission is active. Of 113 children positive by classical serology or buffy coat examination, 106 were detected by PCR (sensitivity: 93.8%). We did not observe any significant difference of PCR sensitivity between initial (IgM and/or buffy coat positive) and indeterminate stage (only IgG positive) patients. Among the remaining 155 children unconfirmed as chagasic (who were either only IgM positive, IgG-, IgM-, and buffy coat-negative) only 1 case was PCR positive. This case may be due to DNA contamination, or to a very recent infection not detected otherwise, or to specific immune depression. These results show that PCR is a very sensitive parasitological test for Chagas' disease in active transmission regions. The future follow-up of the possibly infected patients who were only IgM-positive should clarify the interest of PCR and IgM tests in the detection of starting infections.

Adolescent↗
PubMed1995

Field application of polymerase chain reaction diagnosis and strain typing of Trypanosoma cruzi in Bolivian triatomines.

A new approach for direct identification and characterization of Trypanosoma cruzi stocks in biological samples was tested for field applicability on an extensive sample of feces collected from triatomine vectors from four different species found in Bolivia. The first step of the technique is polymerase chain reaction (PCR) amplification of the hypervariable region of kinetoplast DNA minicircles of T. cruzi parasites. In this report, 345 fecal samples were analyzed and the PCR results were compared with microscopic examination. For Triatoma infestans, the principal Bolivian vector, both techniques were in concordance 85.3% of the time. For the three other species, Rhodnius pictipes, Eratyrus mucronatus, and Triatoma sordida, the fecal samples were all negative by microscopic examination whereas PCR results showed several T. cruzi-infected insects in each species. The second step of the procedure is the characterization of the T. cruzi clones by means of hybridization of the PCR products with clone-specific probes generated by the PCR. We used two probes corresponding to major clones circulating in high frequency in Bolivia (as shown by previous population genetic studies using isoenzyme characterization). We obtained four primary results: 1) we confirm the importance of two major clones in Bolivia in two distinct regions; 2) we report high rates of mixed infections (multiple clones in a single vector) in Triatoma infestans, up to 22% and 35% in Cochabamba and La Paz departments, respectively; 3) the results favor the absence of interaction between different clones; and 4) we find, for the first time, evidence of the major clones circulating in three species of triatomines that are known as mainly sylvatic species.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Identification of Trypanosoma brucei gambiense group I by a specific kinetoplast DNA probe.

A set of 26 Trypanosoma brucei stocks from various African countries, previously characterized by multilocus enzyme electrophoresis (MLEE) for 18 polymorphic loci, have been selected to be representative of the three T. brucei classic subspecies. The kinetoplast DNA minicircle variable regions from these stocks have been amplified using the polymerase chain reaction (PCR) technique, and hybridized with the amplified variable regions of three T. brucei reference stocks, previously identified as T. brucei brucei, T. brucei gambiense, and T. brucei rhodesiense, respectively. Both T. b. brucei and T. b. rhodesiense probes hybridized only with their own stocks, but the T. b. gambiense probe specifically hybridized with a group of 12 stocks that represented most of the human stocks from West and Central Africa in our sample. These stocks, which appeared as a clearly separable cluster based on previous MLEE analysis, probably correspond to T. brucei gambiense group I. No other stock hybridized with this amplified fragment. Since the T. b. gambiense probe obtained is specific for many isolates that are pathogenic for humans in Central and West Africa, it appears to be a promising tool for epidemiologic and medical surveys.

Africa↗
PubMed1993

Population genetics of Trypanosoma cruzi and Trypanosoma rangeli: taxonomical and epidemiological purpose.

A genetic analysis of a set of Trypanosoma cruzi and Trypanosoma rangeli stocks was performed by two combined approaches, namely multilocus enzyme electrophoresis (MLEE) and labeling by DNA probes. A considerable genetic variability was evidenced within each of the two species. Since the upper level of resolution of the isoenzyme method was reached, it was impossible to draw any definite discrimination between the two species by usual clustering methods. Nevertheless, two markers appeared as species-specific, namely the malic enzyme, and a probe that hybridizes highly-repeated sequences of T. cruzi.

Animals↗
PubMed1992

Direct identification of Trypanosoma cruzi natural clones in vectors and mammalian hosts by polymerase chain reaction amplification.

The polymerase chain reaction was used to amplify the highly variable region of the kinetoplast minicircle of Trypanosoma cruzi directly in biological samples (feces of infected Triatomine bugs, blood samples of experimentally infected mice, and artificially infected human blood samples). Hybridization of the amplified DNAs with reference stocks representing different genotypes (natural clones) enabled us to characterize the stocks infecting the biological samples under study. The main interest of this new approach is the diagnosis of T. cruzi infection and simultaneous direct identification of the different natural clones circulating in vectors and mammalian blood without isolation of the stocks. The suitability of this technique for epidemiologic studies is also discussed.

Animals↗
PubMed1991

Antigenic specificity of the 72-kilodalton major surface glycoprotein of Leishmania braziliensis braziliensis.

We examined the expression and the antigenicity of the major surface polypeptides of Leishmania braziliensis braziliensis and Leishmania donovani chagasi, parasites which commonly coexist in the same endemic areas of Bolivia. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis protein profiles from surface-iodinated promastigotes showed the presence of a unique iodinatable polypeptide of 72 kDa on the L. b. braziliensis surface and of two major components of 65 and 50 kDa exposed at the surface of L. d. chagasi. Comparison of the peptide digestion profiles of the major iodinated polypeptides of both strains showed no similarity between the maps of the 72- and the 65-kDa polypeptides of L. b. braziliensis and L. d. chagasi, respectively. Immunoprecipitation of surface-labeled L. b. braziliensis Nonidet P-40 extracts with 35 serum specimens obtained from Bolivian patients with cutaneous and mucocutaneous leishmaniasis showed that all serum specimens recognized predominantly the 72-kDa antigen and high-molecular-mass proteins in some cases. The recognition patterns were independent of the geographical origin of the patient, the type of lesion, and the serum antibody titer. Serum specimens from children with visceral leishmaniasis did not precipitate the L. b. braziliensis 72-kDa antigen. Hamster hyperimmune serum against L. b. braziliensis also recognized the 72-kDa surface antigen. However, this recognition was inhibited in the presence of the homologous nonlabeled antigen but not in the presence of heterologous (L. d. chagasi and Trypanosoma cruzi) antigens. The specific recognition of 72-kDa surface antigen in both natural and experimental L. b. braziliensis infections suggests that this antigen could be a good candidate for use in the differential immunodiagnosis and prognosis of the disease.

Animals↗
PubMed1991

General procedure to construct highly specific kDNA probes for clones of Trypanosoma cruzi for sensitive detection by polymerase chain reaction.

Our strategy of probes designing for major clones of Trypanosoma cruzi was performed taking into account the: (i) clear identification of the major clones under multilocus study; (ii) hypothesis of a parallel evolution between the extranuclear and nuclear markers; (iii) structure of kDNA which allowed to amplify high variable regions of the minicircle (HVRm) by PCR. The large production of HVRm was very useful to test their ability to be used as probes for detection of DNA from a diversified genetic panel of T. cruzi. Our success in designing such probes has important implications on: the enhancement of 2 evolutive hypothesis about the clonal structure of T. cruzi and the parallel evolution of their extranuclear and nuclear genetics markers; direct diagnosis in patients and vectors. Studies on bio-clinical significance of major clones are discussed. This procedure could be used as a general strategy to generate DNA probes for Kinetoplastida.

Animals↗
PubMed1990

Identification of cytoplasmic soluble antigens related to the major surface antigens of Leishmania braziliensis braziliensis and L. donovani chagasi.

This study describes the identification of aqueous-soluble antigens in Leishmania promastigotes immunologically and biochemically closely related to the major surface antigen. Proteins from surface-iodinated L. braziliensis braziliensis and L. donovani chagasi promastigotes, extracted and separated by partitioning in the detergent Triton X-114, were analyzed. Immunoblotting of the extracted proteins, using homologous antisera, showed recognition of a 72-kDa labeled, amphiphilic antigen of L. b. braziliensis and a 65-kDa surface antigen of L. d. chagasi. The respective homologous sera also recognized non-labeled hydrophilic antigens, similar in their apparent molecular weights to the major surface antigens. The amphiphilic and hydrophilic antigens of each species were found to share common antigenic determinants, inasmuch as monospecific antibodies that recognized the amphiphilic protein reacted with the hydrophilic antigen. Structural homology was also obtained in the peptide-digestion profiles of the amphiphilic and the respective hydrophilic major antigens. Zymogram assay showed that both amphibilic and hydrophilic fractions displayed proteolytic activity that could be directly attributed to the major L. b. braziliensis and L. d. chagasi antigens. The hydrophilic antigens found in this study are probably not hydrolytic products of the surface antigens and occur in large quantities in the promastigote cytosol.

Animals↗
PubMed1985

Comparisons of immunological tests for serodiagnosis of Chagas disease in Bolivian patients.

Enzyme linked immunosorbent assay (ELISA) and immunoelectrophoresis (IEP) were evaluated and compared to the classical immunofluorescence (IF) and complement fixation test (CFT) in the immunological diagnosis of Chagas' disease, using 407 sera from Bolivian patients. 72.7 to 79.5% of randomised sera, coming from patients living in endemic areas for Chagas' disease were considered as positive, according to the test limits, previously determined. The techniques could be classified according to their percentage detection as ELISA greater than IF greater than CFT greater than IEP. The quantitative correlations between the tests were excellent (p less than 0.001). 92.8% of the sera were positive or negative for the four tests, 6.1% for three tests and 1.1% for only two tests. The agreement between the tests ranged from 94.6 to 99.2%, co-positivity from 95.5 to 100% and co-negativity from 88.5 to 100%. IF gave the best results, and could be considered as the reference test since it was easy and rapid to perform. However to avoid errors or discrepancies between laboratories, two tests, such as IF and CFT, might be associated. ELISA can be used if higher sensitivity is required. IEP showed 1 to 14 precipitation bands in 96% of the sera from infected patients. The precipitation band 5, previously demonstrated as Trypanosoma cruzi specific, was present in 73% of these sera, indicating the interest to use immunoprecipitation test, if more specificity is required for the immunodiagnosis of Chagas' disease.

Bolivia↗