Analysis of Plasmodium falciparum var genes expressed in children from Papua New Guinea.
BACKGROUND
The variable antigen P. falciparum erythrocyte membrane protein-1 (PfEMP1) is a major virulence factor in malaria. A large number of var genes encode PfEMP1, and we hypothesized that a restricted PfEMP1 repertoire determines clinical disease presentation. We conducted a case-control study in Papua New Guinea and analyzed transcribed var genes in naturally infected children.


METHODS
var messenger RNA was isolated from 78 children with asymptomatic, mild, or severe malaria. We prepared complementary DNA from the upstream region into the DBL1alpha domain and picked, on average, 20 clones for sequencing.


RESULTS
Twenty-five percent of centrally located var genes were shared between children, whereas only 5% of subtelomeric genes were shared, indicating lower diversity in the former group. Linkage between group B or C var upstream sequences and DBL1alpha groups was not observed, which impeded prediction by DBL1alpha analysis. A higher proportion of var group A sequences was detected in symptomatic malaria, and a subgroup of frequently encountered var genes with complex head structure seems to be associated with severe malaria. A subset of var group C genes was frequently expressed in older children with asymptomatic high levels of parasitemia.


CONCLUSIONS
Despite this vast diversity, restricted disease-associated var genes were identified and might be used for innovative interventions based on PfEMP1.
Falk
Nicole
N
Swiss Tropical Institute, Basel, Switzerland.
Kaestli
Mirjam
M
Qi
Weihong
W
Ott
Michael
M
Baea
Kay
K
Cortés
Alfred
A
Beck
Hans-Peter
HP
D000595:Amino Acid Sequence; D000818:Animals; D016022:Case-Control Studies; D002648:Child; D005786:Gene Expression Regulation / Q000502:physiology*; D014644:Genetic Variation; D006801:Humans; D016778:Malaria, Falciparum / Q000453:epidemiology / Q000469:parasitology*; D008969:Molecular Sequence Data; D010219:Papua New Guinea / Q000453:epidemiology; D010802:Phylogeny; D010963:Plasmodium falciparum / Q000145:classification / Q000235:genetics* / Q000378:metabolism*; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016053:RNA, Protozoan / Q000235:genetics; D016415:Sequence Alignment
D015800:Protozoan Proteins; D016053:RNA, Protozoan; C085731:erythrocyte membrane protein 1, Plasmodium falciparum