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F Peyron

Publications and source records attributed to F Peyron.

At least 109 records · Page 6Linked to original sources
PubMed1992

Rapid in vivo detection of chloroquine resistance by the Quantitative Buffy Coat Malaria Diagnosis System.

The use of the Giemsa-stained thick blood smear for the diagnosis of malaria has not been supplanted since the discovery of the parasite by A. Laveran in 1880. Recently, a new direct diagnosis technique, the Quantitative Buffy Coat (QBC)* Malaria Diagnosis System, has been developed. We compared this technique with the thick blood smear diagnosis in a study of the efficacy of chloroquine therapy in Zaire. A total of 815 subjects were screened; 71 participated in the trial. They were given chloroquine at a dose of 25 mg/kg of body weight over three days and were examined for parasitemia two and seven days after treatment. Chloroquine resistance was detected in 38% of the subjects by thick blood smear and in 45% by the QBC test. Of greater interest was the time required for each diagnosis: an average of 17 min was required to examine microscopic fields with 1,000 leukocytes by thick blood smear analysis compared with less than one min by the QBC system. In addition, we did not observe diminished attention from fatigue by microscopists using the QBC system despite the large number of tests conducted. We conclude that the QBC system is an important tool for studies of drug resistance.

Animals↗
PubMed1991

Relationships between clinical protection and antibodies to Plasmodium falciparum RESA (ring-infected erythrocyte surface antigen) peptides.

A longitudinal study involving 76 individuals living in Dafinso and Vallée du Kou (near Bobo-Dioulasso, Burkina Faso, West Africa) was performed in June 1987 (beginning of the transmission period), August-September 1987 (during) and January 1988 (after). The serological antibody (Ab) responses against synthetic peptides representing repeat amino acid sequences of the P. falciparum Ring-Infected Erythrocyte Surface Antigen (RESA): (EENV)5, (EENVEHDA)4, (DDEHVEEPTVA)2 were evaluated by ELISA. The clinical longitudinal study during the transmission period allowed us to define three different groups in terms of age and occurrence of clinical malarial attack (greater than 5000 parasites mm-3 of blood and axillary fever greater than 37.7 degrees C). Levels (A620) of Ab to (EENVEHDA)4 and (DDEHVEEPTVA)2 were correlated with age. The adult group (III) had the highest prevalences of Ab to RESA peptides. No significant difference was found between groups of children with or without malaria attack. Nevertheless, at the beginning of the transmission period, children who had at least one malaria attack during the study presented the lowest level of antibodies to RESA peptides.

Animals↗
PubMed1991

Development of natural immunity in Plasmodium falciparum malaria: study of antibody response by Western immunoblotting.

A longitudinal study was carried out in Burkina Faso to investigate the natural development of the immune response to Plasmodium falciparum malaria. Three bleedings were carried out before, during, and after the seasonal peak of transmission. Detailed antigen mapping and antibody prevalence of the 248 collected serum samples were established by immunoblotting on the basis of several epidemiological and biological parameters. An improved Western immunoblotting system was used to analyze up to 67 serum samples on each nitrocellulose sheet. This system allowed us to perform the entire study with strictly comparable conditions. Two different blood-stage antigens (exoantigens and somatic antigens) were used to analyze the distribution of different classes and subclasses of immunoglobulins according to the age of the individuals, the presence or absence of a malarial attack, the transmission period, the origin of parasite isolates, and the response to intraerythrocytic stages. Although this analysis emphasizes strong individual variations, reactions with two major antigens of 115 and 103 kDa were especially noted. These antigens induced high antibody levels and prevalences but were probably not involved in protection. The prevalence of immunoglobulin G (IgG) antibodies differed by isotype. Most of antigens stimulating IgG production were also responsible for the IgM antibody response. The role played by these antibodies in the development of natural immunity against malaria is discussed.

Adolescent↗
PubMed1991

Levels of cytokines in plasma during Plasmodium falciparum malaria attacks.

The variation of levels of tumor necrosis factor, granulocyte-macrophage colony-stimulating factor, gamma interferon, neopterin, and interleukin-2 receptors in plasma were monitored in 16 patients presenting with an acute Plasmodium falciparum malaria attack. Relations among cytokine levels and between cytokine levels and hematological and parasitological data were assessed.

Adult↗
PubMed1991

Platelet cytotoxicity against parasites.

Platelets are not restricted to hemostasis and thrombosis since they are involved in defence mechanisms especially in parasitic diseases. They express cytotoxic functions in vitro and in vivo against extra-cellular and intra-cellular parasites. The toxic process is mediated either by specific antibodies or directly by the parasite itself. As some metabolic pathways seem to be implicated both in hemostasis and in parasiticidal activity, primary hemostasis and cytotoxicity may be considered as specialized inflammatory responses.

Animals↗
PubMed1991

[Tumor necrosis factor during the course of neuromalaria: new therapeutic perspectives].

Malaria remains one of the major public health problem in tropical and subtropical world. Malaria pathogeny depends partly on parasite multiplication and partly on some elements of the immunological response. It has recently become evident that one of these elements, Tumor Necrosis Factor (TNF), is directly implicated in the pathogenesis of cerebral malaria. TNF increase cytoadherence of infected erythrocytes to the brain microvascular endothelium. In a study involving african children with cerebral malaria high levels of TNF were positively correlated with a fatal outcome. We have previously demonstrated that in vitro Plasmodium falciparum products can directly stimulate the production of TNF from human macrophages. The aim of this work was to identify this soluble parasitic substance. Our results demonstrated that this substance could be a repetitive amino-acid sequence of the Ring-infected Erythrocyte Surface Antigen (RESA). The immunization against this kind of well-known peptides may be used as anti-disease vaccine. The elimination of mortality would be an essential target instead of parasitic clearance.

Antigens, Protozoan↗
PubMed1990

Plasma levels of tumor necrosis factor during a longitudinal survey in an endemic area of malaria.

The plasma levels of tumor necrosis factor were measured during a longitudinal survey of 84 subjects living in an endemic area of malaria. In most cases, the plasma tumor necrosis factor was found at its highest level during the malaria transmission peak and became normal again during the dry season. Children having suffered from malarial attack keep low tumor necrosis factor levels compared to adults and asymptomatic children. These results suggest that tumor necrosis factor could be associated with the development of resistance against malaria.

Adolescent↗
PubMed1990

Correlation between beta 2-microglobulin and soluble interleukin-2 receptor levels in plasma of individuals living in a malarial endemic region.

beta 2-Microglobulin (beta 2m) levels were related to the expected immunoprotection in 81 individuals living in a malarial mesoendemic area near Bobo-Dioulasso (Burkina Faso), who were longitudinally followed. Soluble interleukin-2 receptor (sIL-2R) levels were positively correlated to those of beta 2m (r = 0.44; n = 237; P less than 0.001). This suggests that most of the beta 2m could have originated from activated T and B cell membrane turnover. In our study, both beta 2m and sIL-2R were inversely related to IgG antibodies (Ab) against somatic antigen of Plasmodium falciparum (Som-Ag). Therefore, these molecules at high levels could have a down regulating activity, directly or indirectly, on B cells producing this kind of Ab.

Adolescent↗
PubMed1990

Tumor necrosis factor production by human macrophages stimulated in vitro by Plasmodium falciparum.

Production of tumor necrosis factor by human macrophages may be induced in vitro by cytoadherent and noncytoadherent strains of Plasmodium falciparum, with an optimal ratio of one to three parasitized erythrocytes per macrophage. Centrifuged and heated crude culture supernatants have the same effect, thus showing the existence of a thermostable soluble factor able to induce this expression. In vitro kinetic experiments have shown that the secretion of tumor necrosis factor appears early, with a maximal peak at 8 h.

Animals↗
PubMed1990

Longitudinal survey in an endemic region of plasma soluble interleukin-2 receptor and antibody levels in Plasmodium falciparum malaria.

A survey involving 81 individuals living in Dafinso and Vallée du Kou no. 4 (near Bobo-Dioulasso), Burkina Faso, was performed in June 1987, August to September 1987, and January 1988, respectively, at the beginning of, during, and after the transmission season of malaria. The clinical longitudinal study during the transmission period allowed us to define three different groups in terms of both age and occurrence of malaria attack (5,000 Plasmodium falciparum per mm3 of blood and axillary fever of greater than 37.7 degrees C) as follows: group 1, persons less than or equal to 15 years old who had at least one malaria attack during the transmission period; group 2, individuals less than or equal to 15 years old who did not have any malaria attacks; and group 3, individuals considered to be protected (adults greater than 15 years old with no malaria attacks). Soluble interleukin-2 receptor (sIL-2R) levels were found to be significantly increased (P less than 0.001) in the first two groups (1,047 +/- 481 U/ml [mean +/- standard deviation]) as compared with the adult group (605 +/- 307 U/ml). Considering all the groups, no significant difference was observed between observation periods. Levels of sIL-2R were inversely correlated (r = -0.39, n = 237, P less than 0.01) with age (range, 4 to 67 years). Negative correlations were also noticed between the levels of sIL-2R and those of antibodies to somatic antigen of P. falciparum (immunoglobulin G [IgG] class [r = -0.33, n = 237, P less than 0.01] and IgM class [r = -0.20, n = 237, P less than 0.05]). IgG antibody levels to somatic antigen were correlated with age, but IgM antibody levels to somatic antigen were not. The possible role played by sIL-2R in effector mechanisms against malaria is discussed.

Adolescent↗
PubMed1990

[Erythrocytes infected by Plasmodium falciparum activate human platelets].

Blood platelets are involved in Plasmodium falciparum malaria pathology as shown by thrombocytopenia and increased plasma level of two alpha granule proteins: beta thromboglobulin (beta TG) and platelet factor 4 (PF4). In this study we demonstrate that Plasmodium falciparum parasitized erythrocytes activate directly the secretion of beta TG and PF4 by human platelets. This secretion is related to parasitemia and occurs immediately after contact. Treatment of parasited erythrocytes by trypsin and diffusion chamber experiments suggest that platelet activation is triggered by parasitic substances shed on erythrocyte membrane and released in the culture medium.

Animals↗
PubMed1990

[Uncommon clinical aspects of Plasmodium falciparum malaria].

An attack of malaria can be lethal; however, besides this classic form, clinical cases are less brutal, often with blood disorders, related to Plasmodium falciparum infection resistant to chloroquine. Because of the importance of chloroquinoresistance through the world, chemoprophylaxis is very difficult, and the fight against mosquitoes' bites is once again very important.

Animals↗
PubMed1990

[Prevention of post-transfusional malaria in France: a descriptive survey].

Due to an expansion in international travel, an increasing number of blood donors are at risk of exposure to malaria. Preventions of transfusional malaria is required by law in France. Acting as National Reference Center for Malarial Immunology we noticed that this regulation was not being respected by all blood banks. We conducted a questionnaire study concerning 181 blood banks to evaluate under which circumstances serological tests were requested, the policy employed in case of seropositivity, the cost of screening, and wishes concerning modification of the law. The response rate was 46.9%. We noticed a great variability in attitude: only 21% of blood banks followed the regulation; 63% added extra criteria to the law; 16% did not follow the regulation. Indirect immunofluorescence was the main method used by 91.5% of blood banks. However the specificity threshold fluctuated. The fate of the blood unit in case of seropositivity was variable (discard of blood bags, plasma fractionation, blood used). Centers who answered to questionnaire performed 2,513,687 blood donations during the survey. A serology was carried out in 2.6% of donations, and was positive in 9.4% of cases i.e. 0.24% of donations. The average cost of screening was 35 FF. The profit loss due to discard of positive blood was estimated at 1.7 million FF. for the duration of the survey and the blood banks studied. 99% of centers answering the questionnaire expressed desire for standardisation of screening method.

Animals↗