title: The 3D7var5.2 (var COMMON) type var gene family is commonly expressed in non-placental Plasmodium falciparum malaria.
abstract: Relapse variants in chronic Plasmodium falciparum infections are antigenically distinct from the parental parasites. The variable antigen PfEMP1 expressed at the surface of the infected erythrocyte (IE) is encoded by the var gene family with approximately 60 copies per haploid genome. Placental isolates commonly express DBLgamma containing subtypes of var genes with homology to either 3D7var5.2 (var(COMMON)) or FCR3var(CSA). Here we report that var(COMMON) related genes are constitutively transcribed in approximately 60% of malaria infected children in Gabon. var(COMMON) is conserved in field isolates over at least 2.1kb. In 3D7 parasites var(COMMON) is present on chromosome 5 (var5.2) and constitutively transcribed in the opposite direction to most other var genes. It lacks a regulatory intron, an acidic terminal segment and ends in telomeric repeat sequences. var(COMMON) encodes a large, hypothetical PfEMP1 of a structure similar to previous placenta-binding PfEMP1s but it is not present at the IE-surface. IE of a 3D7 clone (3D7S8) transcribe var(COMMON) but express a PfEMP1 distinct from var(COMMON) at the surface and adhere to placental tissues through var(COMMON) independent novel mechanisms. Our report suggests that expression of var(COMMON) type genes is not restricted to placental malaria.
authors.affiliation: Microbiology and Tumor Biology Center, Karolinska Institutet, P.O. Box 280, SE-171 77, Stockholm, Sweden.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Winter
authors.forename: Qijun
authors.initials: Q
authors.lastname: Chen
authors.forename: Kirsten
authors.initials: K
authors.lastname: Flick
authors.forename: Peter
authors.initials: P
authors.lastname: Kremsner
authors.forename: Victor
authors.initials: V
authors.lastname: Fernandez
authors.forename: Mats
authors.initials: M
authors.lastname: Wahlgren
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004912:Erythrocytes / Q000378:metabolism / Q000469:parasitology; D005260:Female; D005786:Gene Expression Regulation; D017125:Genes, Protozoan; D006801:Humans; D016778:Malaria, Falciparum / Q000235:genetics / Q000378:metabolism / Q000469:parasitology*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D010922:Placenta Diseases / Q000469:parasitology; D010963:Plasmodium falciparum / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D011247:Pregnancy; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D015800:Protozoan Proteins; C085731:erythrocyte membrane protein 1, Plasmodium falciparum