In vivo switching between variant surface antigens in human Plasmodium falciparum infection.
A semi-immune individual was retrospectively found to have maintained an apparently monoclonal and genotypically stable asymptomatic infection for months after clinical cure of a Plasmodium falciparum malaria episode. Before the attack, the individual had no antibodies to variant surface antigens (VSAs) expressed by an isolate (isolate A) obtained at the time of the episode or by a genotypically identical isolate (isolate B) obtained from the same individual 3 months later. Six weeks after the attack, a strong isolate A-specific VSA antibody response had developed in the complete absence of isolate B-specific antibodies. In contrast, plasma obtained 7 months after the attack contained high levels of VSA antibodies recognizing both isolates. This is the first direct evidence of in vivo switching between VSAs in human P. falciparum infection. Our results suggest that VSA switching is an important survival strategy of P. falciparum, enabling the parasite to persist despite protective, parasite-specific immune responses.
Staalsoe
Trine
T
Centre for Medical Parasitology, Copenhagen University Hospital, Rigshospitalet, and Institute for Medical Microbiology and Immunology, University of Copenhagen, Copenhagen, Denmark. tscmp@rh.dk
Hamad
Amel A
AA
Hviid
Lars
L
Elhassan
Ibrahim M
IM
Arnot
David E
DE
Theander
Thor G
TG
D000818:Animals; D000913:Antibodies, Protozoan / Q000096:biosynthesis / Q000097:blood; D000940:Antigenic Variation / Q000276:immunology*; D000953:Antigens, Protozoan / Q000235:genetics / Q000276:immunology*; D015331:Cohort Studies; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004912:Erythrocytes / Q000469:parasitology; D005434:Flow Cytometry; D006801:Humans; D016778:Malaria, Falciparum / Q000097:blood / Q000276:immunology*; D010963:Plasmodium falciparum / Q000235:genetics / Q000276:immunology*; D016133:Polymerase Chain Reaction; D012189:Retrospective Studies; D013397:Sudan
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D016054:DNA, Protozoan