Plasmodium falciparum population dynamics in a cohort of pregnant women in Senegal.
BACKGROUND
Pregnant women acquire protective antibodies that cross-react with geographically diverse placental Plasmodium falciparum isolates, suggesting that surface molecules expressed on infected erythrocytes by pregnancy-associated malaria (PAM) parasites have conserved epitopes and, that designing a PAM vaccine may be envisaged. VAR2CSA is the main candidate for a pregnancy malaria vaccine, but vaccine development may be complicated by its sequence polymorphism.


METHODS
The dynamics of P. falciparum genotypes during pregnancy in 32 women in relation to VAR2CSA polymorphism and immunity was determined. The polymorphism of the msp2 gene and five microsatellites was analysed in consecutive parasite isolates, and the DBL5epsilon + Interdomain 5 (Id5) part of the var2csa gene of the corresponding samples was cloned and sequenced to measure variation.


RESULTS
In primigravidae, the multiplicity of infection in the placenta was associated with occurrence of low birth weight babies. Some parasite genotypes were able to persist over several weeks and, still be present in the placenta at delivery particularly when the host anti-VAR2CSA antibody level was low. Comparison of diversity among genotyping markers confirmed that some PAM parasites may harbour more than one var2csa gene copy in their genome.


CONCLUSIONS
Host immunity to VAR2CSA influences the parasite dynamics during pregnancy, suggesting that the acquisition of protective immunity requires pre-exposure to a limited number of parasite variants. Presence of highly conserved residues in surface-exposed areas of the VAR2CSA immunodominant DBL5epsilon domain, suggest its potential in inducing antibodies with broad reactivity.
Guitard
Juliette
J
Institut de Recherche pour le Développement, Université Paris Descartes, France. julietteguitard@yahoo.fr
Andersen
Pernille
P
Ermont
Caroline
C
Gnidehou
Sédami
S
Fievet
Nadine
N
Lund
Ole
O
Deloron
Philippe
P
Ndam
Nicaise Tuikue
NT
D000595:Amino Acid Sequence; D000953:Antigens, Protozoan / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015331:Cohort Studies; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D016778:Malaria, Falciparum / Q000276:immunology* / Q000469:parasitology; D018895:Microsatellite Repeats / Q000235:genetics; D008969:Molecular Sequence Data; D010920:Placenta / Q000469:parasitology*; D010963:Plasmodium falciparum / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D011110:Polymorphism, Genetic / Q000235:genetics; D011247:Pregnancy; D015597:Pregnancy Complications, Parasitic / Q000097:blood / Q000235:genetics* / Q000276:immunology; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D012675:Senegal / Q000453:epidemiology
D000953:Antigens, Protozoan; D015800:Protozoan Proteins; C512601:VAR2CSA protein, Plasmodium falciparum; C065974:merozoite surface protein 2, Plasmodium