Identification of a major rif transcript common to gametocytes and sporozoites of Plasmodium falciparum.
BACKGROUND
The Plasmodium falciparum parasite is transmitted in its sexual gametocyte stage from man to mosquito and as asexual sporozoites from mosquito to man. Developing gametocytes sequester preferentially in the bone marrow, but mature stage gametocytes are released to the bloodstream. Sexual stage parasite surface proteins are of interest as candidate target antigens for transmission blocking vaccines.


METHODS
In this study, the transcript profiles of rif and var genes, known to encode surface antigens in asexual blood stage parasites, were investigated at different stages of 3D7/NF54 gametocytogenesis and in sporozoites.


RESULTS
Gametocytes exhibited a rif transcript profile unlinked to the rif and var transcript profile of the asexual progenitors. At stage V, mature gametocytes produced high levels of a single rif gene, PF13_0006, which also dominated the rif transcript profile of sporozoites. All var genes appeared to be silenced in sporozoites.


CONCLUSIONS
The most prominent variant surface antigen transcribed in both gametocytes and sporozoites of 3D7/NF54 is a single variant of the RIFIN protein family. This discovery may lead to the identification of the parasites binding ligands responsible for the adhesion during sexual stages and potentially to novel vaccine candidates.
Wang
Christian W
CW
Department of International Health, Immunology, and Microbiology, University of Copenhagen, Copenhagen, Denmark. cwang@sund.ku.dk
Mwakalinga
Steven B
SB
Sutherland
Colin J
CJ
Schwank
Samana
S
Sharp
Sarah
S
Hermsen
Cornelus C
CC
Sauerwein
Robert W
RW
Theander
Thor G
TG
Lavstsen
Thomas
T
D000818:Animals; D000953:Antigens, Protozoan / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary; D016054:DNA, Protozoan / Q000235:genetics; D005784:Gene Amplification; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D017125:Genes, Protozoan; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000235:genetics* / Q000254:growth & development; D016133:Polymerase Chain Reaction; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D034101:Sporozoites / Q000502:physiology; D014158:Transcription, Genetic
D000953:Antigens, Protozoan; D018076:DNA, Complementary; D016054:DNA, Protozoan; D008565:Membrane Proteins; D015800:Protozoan Proteins; C534665:RIFIN protein, Plasmodium falciparum; D012333:RNA, Messenger; C085731:erythrocyte membrane protein 1, Plasmodium falciparum