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Biomedical subjects

C Rogier

Publications and source records attributed to C Rogier.

At least 73 records · Page 4Linked to original sources
PubMed1996

Plasmodium falciparum induces apoptosis in human mononuclear cells.

The level of spontaneous apoptosis in short-term lymphocyte cultures was evaluated in different human immunodeficiency virus-negative groups of either healthy control individuals or patients with clinical malaria. The mean percentage of spontaneous apoptosis found in patients during a malaria attack was significantly higher than in sex- and age-matched healthy controls. The healthy asymptomatic controls were individuals with different degrees of exposure to Plasmodium falciparum as reflected by their various mean levels of specific anti-P. falciparum (immunoglobulin G and M) antibodies. The percentages of apoptotic nuclei were found to be significantly higher in lymphocytes from subjects living in an area where malaria is holoendemic than in lymphocytes from subjects less exposed. Concentrations of soluble plasma interleukin-2 receptor were also higher in subjects from areas where malaria is endemic than in other groups, revealing different levels of lymphocyte activation. Of particular relevance to the in vivo situation, a P. falciparum schizont-rich extract induced a systematic and significant elevation of apoptotic nuclei at day 6 in 87.5% (35 of 40) of the subjects tested. In additional studies with different concentrations of extract, [3H]thymidine incorporation was concomitant with a low or limited level of apoptosis. Taken together, our results strongly suggest that acute as well as chronic asymptomatic P. falciparum infections were consistently associated with a marked increase in the level of mononuclear cell apoptosis. This process could be implicated in some of the alterations reported for the proliferative T-cell responses in areas where malaria is endemic.

Adult↗
PubMed1996

Rapid turnover of Plasmodium falciparum populations in asymptomatic individuals living in a high transmission area.

A polymerase chain reaction (PCR) typing technique, based on the amplification of polymorphic regions from the merozoite surface protein 1 (MSP-1) and MSP-2 Plasmodium falciparum genes, was used to characterize parasites collected in a longitudinal study of asymptomatic carriers of malaria parasites living in two distinct epidemiologic situations. Blood samples were collected from children and adults living in the village of Dielmo, Senegal, when malaria transmission was 3-6 infective bites/week/individual. For each individual, every sample collected at two-week intervals over a period of three months showed a specific PCR pattern. Changes involved both appearance and disappearance of specific alleles. Analysis of blood samples collected at a few-days interval showed that modifications of the PCR patterns occurred rapidly. Most alleles were detected over a period of 2-3 weeks, but some alleles could be detected only for a few days. The frequent modifications of the PCR patterns indicate significant changes in allelic balance over time, and importantly, this was observed both in children and adults. These results strongly contrast with the stability of the parasite types harbored by asymptomatic individuals living in Pikine, Senegal during a period in which malaria transmission was interrupted, and therefore suggest that the rapid turnover observed in Dielmo may reflect the introduction of new parasite populations by mosquitoes.

Adult↗
PubMed1996

The spread of tick-borne borreliosis in West Africa and its relationship to sub-Saharan drought.

In West Africa, tick-borne relapsing fever is due to the spirochete Borrelia crocidurae and its geographic distribution is classically limited to the Sahel and Saharan regions where the vector tick Alectorobius sonrai is distributed. We report results of epidemiologic investigations carried out in the Sudan savanna of Senegal where the existence of the disease was unknown. A two-year prospective investigation of a rural community indicated that 10% of the study population developed an infection during the study period. Transmission patterns of B. crocidurae to humans and the small wild mammals who act as reservoirs for infection were similar to those previously described in the Sahel region. Examination of 1,197 burrows and blood samples from 2,531 small mammals indicated a considerable spread of the known area of distribution of A. sonrai and B. crocidurae. The actual spread of the vector and the disease has affected those regions where the average rainfall, before the start of the extended drought in West Africa, reached up to 1,000 mm and corresponds to the movement of the 750-mm isohyet toward the south from 1970 to 1992. Our findings suggest that the persistence of sub-Saharan drought, allowing the vector to colonize new areas in the Sudan savanna of West Africa, is probably responsible for a considerable spread of tick-borne borreliosis in this part of Africa.

Adolescent↗
PubMed1996

Pattern of immunoglobulin isotype response to Plasmodium falciparum blood-stage antigens in individuals living in a holoendemic area of Senegal (Dielmo, west Africa).

Three cross-sectional studies were conducted in a representative cohort of individuals living continuously in an area holoendemic for malaria in Senegal. Plasma from 145 children and adults were tested. The pattern of antimalarial immunoglobulin class (IgM and IgG) and subclass (IgG1 to IgG4) antibody distribution was determined by enzyme-linked immunosorbent assay using a crude blood-stage antigen of Plasmodium falciparum-infected red blood cells. Adults had higher levels of specific antibodies than children, and IgM, IgG2, and IgG3 accounted for the highest difference (2.9, 6.5, and 4.5 times, respectively). Differences in antibody levels were significant for IgG1 to IgG4 between the lowest and the highest transmission season. No particular isotype distribution pattern could be found associated with any given parasitemia level. The relationship between the optical density (OD) values of each isotype and the risk of clinical malaria attack was tested using a Poisson regression model. Only the IgG3 OD increases were found associated with a significantly reduced risk of malaria attack. These seroepidemiologic data suggest that whereas the total IgG-specific activity is not indicative of any given level of protection against malaria, the level of IgG3 was significantly associated with the relative susceptibility to clinical P. falciparum malaria attacks.

Adult↗
PubMed1996

Evidence for an age-dependent pyrogenic threshold of Plasmodium falciparum parasitemia in highly endemic populations.

The high prevalence of asymptomatic malaria infections and the nonspecific signs and symptoms of the disease make the individual diagnosis of clinical malaria uncertain in highly endemic areas. Longitudinal data obtained during a four-month period from a daily survey of 200 permanent inhabitants (one month-83 years old) living in a holoendemic area were analyzed in a random-effects logistic regression model to investigate the relationship between the level of Plasmodium falciparum parasitemia and risk of fever. It was not possible to build a model that described/summarized correctly this relationship by a continuous function. Findings provide evidence for an age-dependent threshold effect of parasitemia on the occurrence of fever. The level of this threshold varied by 2.45 trophozoites per leukocyte, maximum at one year of age, to 0.5 trophozoites per leukocyte, minimum at 60 years of age. When the parasite density of a person crossed the threshold level corresponding to his or her age, the individual's risk of fever was multiplied by 44 (95% confidence interval = 13.6-144.8). The existence of this threshold effect allows parasite density to be used to distinguish malaria attacks from other causes of fever within an individual and should facilitate the accurate evaluation of the incidence of clinical malaria in highly endemic areas.

Adolescent↗
PubMed1996

Different genetic characteristics of Plasmodium falciparum isolates collected during successive clinical malaria episodes in Senegalese children.

A narrow epidemiologic survey was conducted during a four-month period of intense malaria transmission in Dielmo, a holoendemic Senegalese village. Longitudinal clinical and parasitologic follow-up indicate that clinical malaria episodes always occurred after an abrupt increase in parasite densities. Polymerase chain reaction analysis of Plasmodium falciparum parasites was carried out in blood samples collected longitudinally from 10 children who had experienced several clinical episodes during this period. Our data show that the genetic diversity of the parasites circulating in this village is very large. The successive clinical episodes experienced by each child were caused by genetically distinct parasite populations that were recently inoculated and multiplied in an apparently unrestricted manner. Importantly, the genetic characteristics of the parasite populations detected during phases of asymptomatic carriage differed from those causing a clinical episode, suggesting that the various factors that control of parasite growth in these children are strain-specific.

Animals↗
PubMed1996

Tick-borne borreliosis in west Africa: recent epidemiological studies.

Tick-borne borreliosis in West Africa is classically considered a rare disease whose geographic distribution is limited to Saharan and Sahelian regions. We report results of epidemiological investigations which indicate that tick-borne borreliosis is endemic in all regions of Senegal north to the 13 degrees 30'N latitude and is a major cause of morbidity in these areas. Our findings indicate a considerable range extension for the vector tick Alectorobius sonrai and suggest that the persistence of Subsaharan drought is responsible for a large spread of tick-borne borreliosis in West Africa.

Adolescent↗
PubMed1996

[In vitro sensitivity of 85 Plasmodium falciparum isolates in the Fatick region, Senegal].

Increasing resistance of Plasmodium falciparum to chloroquine and other antimalarials has been reported in Africa. Only fragmentary data are available for Senegal. Although combined chloroquine-proguanil is soon scheduled for released on the market, few studies have been published concerning the susceptibility of isolates to either drug. The in vitro susceptibility of 85 Plasmodium falciparum isolates obtained between October 24 and December 2, 1995 from malaria-infected patients living in the Fatick Region of Senegal to five classical antimalarial drugs (chloroquine, cycloguanil, quinine, mefloquine, and halofantrine) was evaluated using an isotopic, semi-microtest. Twenty-nine percent of isolates were resistant to chloroquine (IC50 > 100 nM), 22% to cycloguanil (IC50 > 500 nM), 1% to quinine (IC50 > 500 nM), 22% to mefloquine (IC50 > 20 nM), and 8% to halofantrine (IC50 > 5 nM). Five percent of isolates were resistant to both chloroquine and cycloguanil. Positive correlation was observed between quinine and halofantrine activity and between mefloquine and halofantrine activity. These findings suggest cross resistance or reduced susceptibility between these antimalarial agents which all exhibit a methanolic function.

Animals↗
PubMed1996

[Determination of HLA class I and II alleles in the village of Dielmo].

One-hundred-and sixteen Senegalese Serere were typed in HLA system and compared with other ethnic groups in Gambia. We did not find significant differences (Fisher's exact test; P < 0.01) in the HLA antigens distribution between the Serere and Mandinka groups in Senegal, and the Serere, Mandinka and Wolof in The Gambia. The most common HLA haplotypes (Chi square; P < 0.01) were: A1, B8;A2, Cw2; A10, DR10; B35, Cw4; B57, Cw3; B65, Cw8; B52, DR4; Cw2, DR17; DR7, DQ2; DR18, DQ4.

Alleles↗
PubMed1995

Age-dependent carriage of multiple Plasmodium falciparum merozoite surface antigen-2 alleles in asymptomatic malaria infections.

Genetic diversity of the merozoite surface antigen-2 gene of the human malaria parasite Plasmodium falciparum has been analyzed in a Senegalese village where malaria is holoendemic. A cross-sectional survey of 65 residents was performed in 1992 during the high transmission season. Plasmodium falciparum was detected both by microscopy (77% positive samples) and DNA amplification using a single (29% or 38% positive samples, depending on the primers used) or nested polymerase chain reaction (PCR) (78% positive samples). The overlap between the positive nested PCR and microscopic examination was not complete. The PCR fragments were analyzed for size polymorphism on agarose gels, and were subsequently assigned to the major allelic families 3D7 or FC27 by hybridization with family-specific probes. Both allelic families were found, with a slightly higher prevalence for FC27. Chimeric alleles that failed to hybridize under stringent conditions to the reference probes were also observed. Some were typed using a novel PCR approach, using hybrid pairs of primers, consisting of a family-specific sense oligonucleotide combined with an antisense oligonucleotide specific for the other family. Combining typing techniques, 82% of the positive PCR results yielded more than one band. Both the overall number of fragments and the number of allelic types per carrier were markedly reduced around the age of 15 years. The number of DNA fragments decreased abruptly from an average of four per carrier before the age of 15 years to an average of two in individuals more than 15 years of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

[The utilization of molecular biological tools in the study of malaria transmission: example of programs conducted in Senegal].

Some informations about malaria transmission, which has until nox difficult to get, can be obtained thanks to the use of molecular biology tools, PCR mainly. In Senegal, we use that technique to solve two kinds of problems: -Identification of species of the Anopheles gambiae complex: PCR technique is useful compared to other diagnostic methods (chromosome pattern, DNA probes, etc.) because it enables quickly and simply identification of captured anopheles from the DNA contained in their legs. The rest of the mosquito is tested by circumsporozoite protein antigen ELISA and blood meal ELISA. The data obtained are used to determine distribution, cycles, trophic preferences and comparative vectorial capacities of Anopheles gambiae, Anopheles arabiensis and Anopheles melas. -Identification in a mosquito blood meal of the individual bitten: we propose to evaluate factors (weight, age, sex, location of bedroom, etc.) which could explain why individuals are more, or less, bitten by a Plasmodium vector. Genetic typing is used on inhabitants'leukocytes DNA and on the leukocyte DNA extracted from the blood meal of resting anopheles. Through the high degree of polymorphism of three (AAAG)n microsatellites markers, we hope, using PCR, to attribute each blood meal to one individual. Statistical analysis will be used to identify attractivity factors and to determine more precisely the inoculation rates for each group rather than the classical rate calculated with male adults volunteers.

Adult↗
PubMed1994

[Biology of the vectors and transmission of Plasmodium falciparum, P. malariae and P. ovale in a village in the savanna of west Africa (Dielmo, Senegal)].

From April 1990 to March 1992 a longitudinal entomological study was carried out in Dielmo village, Senegal, an area of Sudan-type savanna. Mosquitoes were sampled by night-bite collections and pyretnrum spray collections. Seven anopheles species were identified: An. gambiae s.s. An. arabiensis, An. funestus, An. pharoensis, An. rufipes, An. squamosus and An. ziemanni. Present throughout the year, An. gambiae s.l. and An. funestus represented more than 98% of anopheles captured on man. A yearly wave of An. gambiae s.l. was observed in the rainy season and An. funestus was generally more abundant in the dry season. The sporozoite rate was 1.5% and 1.3%, respectively, for these two species. Sporozoite typing by monoclonal antibodies indicated that the proportion of infected salivary glands was 92.7% P. falciparum, 18.2% P malariae and 8.2% P. ovale. The inoculation rate was calculated to be respectively 111, 21 and 8 infective bites per human for P. falciparum, P. malariae and P. ovale during the first year. Transmission was highest in the second year, with respectively 272, 54 and 25 infective bites per human.

Adolescent↗
PubMed1994

Aspects of immunity for the AMA-1 family of molecules in humans and non-human primates malarias.

The apical membrane antigen (AMA-1) family of malaria merozoite proteins is characterised by a high degree of inter-species conservation. Evidence that the protein (PK66/AMA-1) from the simian parasite Plasmodium knowlesi was protective in rhesus monkeys suggested that the 83kDa P. falciparum equivalent (PF83/AMA-1) should be investigated for protective effects in humans. Here we briefly review pertinent comparative data, and describe the use of an eukaryotic full length recombinant PF83/AMA-1 molecule to develop a sensitive ELISA for the determination of serological responses in endemic populations. The assay has revealed surprisingly high levels of humoral response to this quantitatively minor antigen. We also show that PK66/AMA-1 inhibitory mAb's are active against merozoites subsequent to release from schizont-infected red cells, further implicating AMA-1 molecules in red cell invasion.

Animals↗
PubMed1994

The Dielmo project: a longitudinal study of natural malaria infection and the mechanisms of protective immunity in a community living in a holoendemic area of Senegal.

The Dielmo project, initiated in 1990, consisted of long-term investigations on host-parasite relationships and the mechanisms of protective immunity in the 247 residents of a Senegalese village in which malaria is holoendemic. Anopheles gambiae s.l. and An. funestus constituted more than 98% of 11,685 anophelines collected and were present all year round. Inoculation rates of Plasmodium falciparum, P. malariae, and P. ovale averaged respectively 0.51, 0.10, and 0.04 infective bites per person per night. During a four-month period of intensive parasitologic and clinical monitoring, Plasmodium falciparum, P. malariae, and P. ovale were observed in 72.0%, 21.1% and 6.0%, respectively, of the 8,539 thick smears examined. Individual longitudinal data revealed that 98.6% of the villagers harbored trophozoites of P. falciparum at least once during the period of the study. Infections by P. malariae and P. ovale were both observed in individuals of all age groups and their cumulative prevalences reached 50.5% and 40.3%, respectively. Malaria was responsible for 162 (60.9%) of 266 febrile episodes; 159 of these attacks were due to P. falciparum, three to P. ovale, and none to P. malariae. The incidence of malaria attacks was 40 times higher in children 0-4 years of age than in adults more than 40 years old. Our findings suggest that sterile immunity and clinical protection are never fully achieved in humans continuously exposed since birth to intense transmission.

Adolescent↗