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G Duvallet

Publications and source records attributed to G Duvallet.

At least 37 records · Page 2Linked to original sources
PubMed1992

Identification and characterization of two repetitive non-variable antigens from African trypanosomes which are recognized early during infection.

The present paper describes two repetitive proteins representing common antigens of African trypanosomes which are non-variant and which are recognized early in infection by the host immune system. These antigens were identified by their ability to immunoreact with bovine serum taken during the early phase of a cyclic trypanosomal infection. Screening of a cDNA library from T. b. gambiense with such early infection serum identified a protein which contains a repetitive motif consisting of 68 amino acid repeat units (GM6). Immunofluorescence and immunogold electron microscopy revealed that GM6 is located on fibres which connect the microtubules of the membrane skeleton with the flagellum. A second repetitive antigen detected by this serum is MARP1 (microtubule-associated repetitive protein 1), a protein previously characterized in this laboratory as a high-molecular weight component of the membrane skeleton, which consists of more than 50 tandemly repeated, near-identical 38 amino acid repeat units. Beta-galactosidase fusion products of both proteins demonstrated a strong immunoreactivity with sera from T. b. brucei and T. congolense-infected cattle. The result from this preliminary immunological evaluation indicates a high immunodiagnostic sensitivity (90%) of the two recombinant antigens which make them interesting candidates for immunodiagnosis of trypanosomiasis in cattle.

Amino Acid Sequence↗
PubMed1992

[Evaluation of the test for detecting trypanosoma circulating antigens using monoclonal antibodies. Experimental and natural infections].

An antigen detection ELISA for the diagnosis of trypanosomes was recently proposed by Nantulya and Lindqvist (1989). Based on species-specific monoclonal antibodies, this test could be used to diagnose a current infection and to identify the causing trypanosomes. The test was evaluated at CRTA during experimental infections in small ruminants and with sera from naturally infected cattle, thanks to reagents supplied by the International Laboratory for Research on Animal Diseases (ILRAD). Sera from cattle sampled in France were also tested. Cattle sera from France gave optical densities (OD) from 0.007 to 0.009 with three monoclonal antibodies against T. congolense, T. vivax and T. brucei. These OD values were well below 0.050, which is considered as a positive threshold OD reading. In the small ruminant experimental infections, the sensitivity of the test was 63.2% for T. congolense-infected animals and 9.9% for T. vivax-infected animals. The sensitivity of parasitological tests was 55.1 and 48.6%, respectively. The combination of the antigen- and parasite-detection tests increased the sensitivity to 82.4 and 52.8%, respectively. Means of OD values, with the naturally infected cattle sera, were 0.116 +/- 0.030 for T. congolense, and 0.011 +/- 0.028 for T. vivax-infected animals. Sixteen out of 20 T. congolense-infected sera (sensitivity of 80%) and one out of 20 T. vivax-infected sera (sensitivity of 5%) gave an OD value exceeding 0.050. The determination of a threshold OD reading lower than 0.050 would greatly improve the sensitivity of the test. This determination could either be done by studying the preinfection sera or a local population of animals living in an area free from trypanosomosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Sensitivity of double microcentrifugation for the research of trypanosomes].

The double microcentrifugation technique, described by KRATZER and ONDIEK (1989) for the parasitological diagnosis of trypanosomes, has been tested both in the laboratory and in the field. The limits of detection obtained here were not as low as those described in the original experiment, but the sensitivity of this technique for the detection of Trypanosoma brucei, T. congolense and T. vivax was better than the phase contrast buffy coat method. This technique, which is easy to apply in the field, is highly recommended, especially for epidemiological surveys. A protocol and a list of equipment are included.

Animals↗
PubMed1987

[Experimental trypanosomiasis caused by Trypanosoma brucei brucei in domestic cattle. Antigenic diversity and trypanotolerance].

The antigenic repertoire expressed in four trypanosensitive Zebu cattle after cyclic infection by a late variant of the repertoire DiTAR 1 was studied using agglutinating antibodies. The repertoire expressed appeared similar to that found previously following syringe infection or cyclic infection by an early variant in trypanosensitive and trypanoresistant bovids. The late variant used to infect the Glossina, however, appeared earlier, immediately after the dominant variants. These results also confirm that the sensitivity of certain bovids to trypanosomiasis is not due to the expression of different antigenic variants.

Animals↗
PubMed1985

Trypanosoma brucei: analysis of relapsing populations in sensitive and resistant breeds of cattle.

The clone DiTat 1.1 of Trypanosoma brucei brucei was injected into four bovids, and clones obtained from successive waves of parasitemia were used to study the expressed variant-specific surface glycoprotein repertoire. Twenty-four clones were obtained which could be classified into 12 different variable antigen types, in addition to the clone injected, using agglutination or immunofluorescence with monospecific antisera. The variable surface glycoproteins of the 25 clones were extracted using the detergent octyl-beta-D-glucopyranoside in the presence of the protease inhibitor, N-cbz-L-phenylalaninechloromethylketone. The molecular weights varied from 52,000 to 69,000 and the pI from 5.0 to 8.8. The virulence of 14 clones representing 13 variable antigen types was ascertained in mice. The mean survival time ranged from 20.5 to 43.0 days. Clones isolated from early peaks of parasitemia in the bovid were the most virulent while clones derived from later peaks were less virulent. It seems that organisms of diminishing virulence appear in bovids, leading to self-cure of the disease. All clones were sensitive to human serum in a blood infectivity inhibition test. Antibody against all virulent clones appeared in 20 cattle (10 Zebus, 10 Baoulés) which had been injected with T. brucei DiTat 1.1. There was no evidence for parasites of high or low virulence being preferentially expressed in resistant or sensitive hosts.

Agglutination Tests↗
PubMed1981

[The epidemiology of human trypanosomiasis due to Trypanosoma gambiense in a focus of the Ivory Coast. I. The distribution of the disease in the population (author's transl)].

The authors have studied the distribution of trypanosomiasis in the population of the focus around Vavoua in the Ivory Coast. Because of numerous immigrants from Upper Volta who have settled in the area, the composition of the population differs from the general population of the Ivory Coast. The cases diagnosed from 1977 to 1979 were studied by village, ethnic group, sex and age. The study shows that the highest incidence of sleeping sickness occurs among men, in the age-groups from 10 to 30 years and among immigrants from Upper Volta.

Adolescent↗
PubMedDate not supplied

Review on the molecular tools for the understanding of the epidemiology of animal trypanosomosis in West Africa.

The epidemiology of animal trypanosomosis around Bobo-Dioulasso (Burkina Faso, West Africa) benefited a lot in the last years from the progress of molecular tools. The two most used molecular techniques were the polymerase chain reaction for the diagnosis of the disease in cattle and the characterization of the trypanosomes in the host and the vector on one hand, and the microsatellite DNA polymorphism in tsetse flies to study the intraspecific genetic variability of the vector on the other hand. The results obtained in the Sideradougou area during a recent two year survey with these techniques, associated with many other georeferenced informations concerning vector and cattle distribution, natural environment, landuse, ground occupation, livestock management, were combined in a Geographical Information System. This new approach of a complex pathogenic system led to a better evaluation of the risk of trypanosome transmission.

Africa, Western↗
PubMedDate not supplied

[Value of indirect fluorescent tests for on the spot prospection of human African trypanosomiasis (author's transl)].

The equipment of a laboratory making indirect antibody-fluorescent tests on dried blood blots in the heart of the trypanosomiasis focus of Bouaflé (Ivory Coast) gave good results. On a visited population of 1444 people, 13 cases were diagnosed by immunofluorescence tests; 8 were already diagnosed on the spot, trypanosome found in gland juice; 5 were diagnosed following the results of immunofluorescence tests. Reduction of time between sampling and immunological results makes easier the search of suspects. Based on these observations, the writers emphasize the great value of the use of immunofluorescence technics on the spot and the establishment of a regional mobile immunofluorescence team for supplementing the work of local prospection teams.

Cote d'Ivoire↗
PubMedDate not supplied

[Human trypanosomiasis focus of Vavoua (Ivory Coast). A clinical, parasitological and sero-immunological survey (author's transl)].

Vavoua human trypanosomiasis focus, located 60 km north of Daloa (Ivory Coast Republic) is facing a period of hyperactivity. A medical survey has been conducted in 9 villages of this focus: 7.424 persons have been examined and 128 new cases diagnosed in the field after clinical and parasitological examinations. Indirect Fluorescence Antibody Test applied to dried blood blots, in the laboratory, revealed 266 immunological suspects to be reexamined. 185 suspects were reexamined, 104 of whom were diagnosed after tyrpanosomes had been found in blood or/and in gland juice. The microhaematocrit centrifuge technique gave good results. Most of the 232 new cases were in the classical first period (unaltered CSF). Authors are insisting on the importance of survey prospections allowing an early diagnosis of sleeping sickness and on the interest of an immunodiagnostic test in addition to classical techniques to diagnose asymptomatical forms.

Cote d'Ivoire↗
PubMedDate not supplied

[Comparative value of ELISA technique and immunofluorescence for the detection in the foci of human African trypanosomiasis].

As the parasitological diagnosis method consisting in the detection of the parasite in people suffering from sleeping sickness did not prove entirely reliable, the authors have tested a new immunoenzymatic diagnosis method called ELISA. 41 sera from clinical suspects have been tested (parasite having been found in 16 of them). Positive and negative levels have been tested by comparison with indirect immunofluorescence. The following results, given in optical density, have been obtained: negative cases less than 36 less than or equal to uncertain cases less than or equal to 40 less than positive cases. When using these date, correlation with immunofluorescence proves to be excellent with a sensibility between 95 and 97,5 p. 100 and a specificity between 97,5 and 99 p. 100.

Cote d'Ivoire↗
PubMedDate not supplied

[Contribution of immunoglobulin assays to the diagnosis of human African trypanosomiasis in patients immunologically suspect (immunofluorescence and ELISA). A preliminary report (author's transl)].

Can the diagnosis of sleeping sickness in patients immunologically suspect, without seeing the parasite, be obtained by dosing IgG and IgM? The authors demonstrate that two groups of people with positive immunodiagnosis, one parasitologically confirmed and the other not confirmed, do not show significant difference when dosing immunoglobulins. These two groups respectively show a significant difference when compared with a parasitologically and immunologicaly negative group. The simultaneous increase in IgG and IgM might confirm the immunodiagnosis.

Cote d'Ivoire↗
PubMedDate not supplied

[Reliability of the indirect immunofluorescence test in the diagnosis of African human trypanosomiasis (author's transl)].

The reliability of an immunodiagnosis depends on its efficiency, i.e. the possibility of sorting out infected people from uninfected thanks to a good sensibility and a good specificity, and to its reproductibility. The authors have studied the reliability of the Indirect Immunofluorescence Antibody Test (IFAT) for trypanosomiasis diagnosis on 90 sera (30 sera from patients with proven trypanosomiasis and 60 sera from patients free of trypanosome infection). Reproductibility is considered as good when the reading has been done by the same reader. Sensibility approaches 100 p. 100 and specificity varies according to readers: the reader taking the "brillance" into account obtains a specificity of more than 85 p. 100 and the reader reading the immunofluorescence extinction obtains a specificity between 65 p. 100 and 77 p. 100. The IFAT may be taken as a reference to evaluate new immunodiagnosis.

Antigens↗