Comparaison de la gametocytogenese in vivo chez les souches de plasmodium falciparum cloroquino-sensibles ou resistants

Lorsque Plasmodium falciparum souffre; il a tendance a devier son cycle parasitaire vers la gametocytogenese. Toute souffrance entrainee par l'utilisation d'un medicament partiellement efficace sur des souches resistantes pourrait donc potentialiser le pouvoir gametocytogene du parasite qui n'a pas ete elimine par la cure therapeutique. Cette hypothese a ete etudiee en suivant la gametocytogenese apres acces palustres traites a la Chloroquine en zone de forte chloroquino-resistance. Des sujets de tous les ages; atteints d'acces palustre ou presentant une forte densite parasitaire apparemment asymptomatique; mais sans gametocyte a JO; ont ete individualises en 2 groupes (sensible et resistant) au vu de l'evolution de la parasitemie apres traitement controle par la Chloroquine. Au total; 144 sujets ont ete suivis. Une poussee gametocytaire atteignant son maximum de densite ou de prevalence au 7eme jour apres l'echec therapeutique; a ete observee chez les sujets resistants. Cette poussee n'a pas ete significative chez les sujets sensibles. L'hypothese emise au debut de l'etude semble donc se confirmer. La neogametocytogenese semble d'autant plus marquee que l'individu est jeune (3 ans). Ni le niveau de resistance in vivo; ni le fait d'etre symptomatique ou non n'a semble intervenir sur le declenchement de cette poussee gametocytaire

Anticorps anti-Pfs48/45 dans les serums de deux populations vivant en zone d'endemie palustre de niveaux de transmission differents

La presence d'anticorps antigamete (Pfs48/45) a ete recherchee par la technique d'ELISA competition chez deux groupes de populations vivant en zone d'endemie palustre de niveau de transmission differente. Le pour centage d'individus possedant les anticorps anti-Pfs/48/45 ainsi que les titres moyens obtenus ont ete faibles. L'age moyen d'apparition de ces anticorps etait tres eleve (37;4 ans). Ces observations indiquent que l'immunite naturelle antigamete (Pfs48/45) serait un phenomene qui s'acquiert tres lentement et necessite plusieurs episodes palustres

Plasmodium falciparum and P. malariae epidemiology in a West African village

Transmission of Plasmodium falciparum and P. malariae was studied in a village in Burkina Faso. Consecutive captures of mosquitos were organized twice a month over a year and the species of the mosquitos identified. Also, the prevalences and densities of Plasmodium spp. were determined every 2 months in a sample of children who lived in the village. Anopheles gambiae, A. funestus, and A. nili were the local vectors, but only the first two played a predominant role in both P. falciparum and P. malariae transmission. The parasitological sporozoite index (SI) was 4.48% for A. gambiae and 4.22% for A. funestus. The immunological SIs were higher: 5.82% of A. gambiae were infected with P. falciparum and only 0.16% with P. malariae; the corresponding proportions for A. funestus were 6.45% and 0.41%. Transmission of Plasmodium spp. by A. gambiae was important during the rainy season (July-October) and by A. funestus at the beginning of the dry season (September-November). Each child in the study village could receive about 396 P. falciparum-infected bites per year but only 22 of P. malariae. The P. falciparum parasite indices were maximum during the middle of the rainy season (August), while those for P. malariae reached a peak during the dry season (February)

Glutamate rich Plasmodium falciparum antigen GLURP

We have characterized a glutamate rich Plasmodium falciparum antigen; GLURP; which by immunoassays appears to be present in both the preerythrocytic and erythrocytic stages of the vertebrate life cycle. The gene which is located on chromosome 10 encodes a polypeptide of 1271 residues with a predicted molecular mass of 145 kDa. Rabbit antiserum against a fusion protein expressing the C-terminal end of the molecule detects a protein with a molecular mass os 220 kDa. The sequence includes two hydrophobic regions; 23 residues near the N-terminus; which may act as a signal peptide; and a second located at the C-terminus consisting of 33 predominantly hydrophobic residues. Except for these hydrophobic regions the protein is hydrophilic and highly charged. The sequence has two tandem repeats designated R1 and R2 these regions are found to be conserved in isolates from different geographical areas. High levels of anti-GLURP antibodies have been shown to correlate with low parasite density. The indication of GLURP being expressed in all stages of the parasite in the human host raises significantly the prospects of the potential of this molecule