In vitro selection of Plasmodium falciparum 3D7 for expression of variant surface antigens associated with severe malaria in African children

TY - JOUR

T1 - In vitro selection of Plasmodium falciparum 3D7 for expression of variant surface antigens associated with severe malaria in African children

AU - Staalsoe, Trine

AU - Nielsen, Morten A

AU - Vestergaard, Lasse S

AU - Jensen, Anja T R

AU - Theander, Thor G

AU - Hviid, Lars

N1 - Keywords: Adolescent; Adult; Africa; Animals; Antibodies, Protozoan; Antigens, CD36; Antigens, Protozoan; CHO Cells; Cell Adhesion; Child; Cricetinae; Erythrocytes; Gene Expression; Humans; Immunoglobulin G; Malaria, Falciparum; Middle Aged; Plasmodium falciparum; Selection (Genetics); Variant Surface Glycoproteins, Trypanosoma

PY - 2003

Y1 - 2003

N2 - P. falciparum-infected red blood cells (IRBC) can adhere to endothelial host receptors through parasite-encoded, clonally variant surface antigens (VSA). The VSA-mediated IRBC adhesion and the acquired VSA-specific antibody response have both been linked to IRBC organ tropism and disease severity. Parasites isolated from young children with severe malaria (SM) tend to express a limited and conserved set of VSA (VSASM) that are both stronger and more commonly recognized by IgG in the plasma of malaria-exposed individuals than VSA (VSAUM) expressed by parasites causing uncomplicated malaria (UM) in older semi-immune children. Establishment of the genetic mechanism underlying changes in VSA expression in response to in vitro selective pressure is now possible because of the availability of the entire genomic sequence of the P. falciparum clone 3D7. As a first step towards direct molecular identification of VSASM-encoding genes in 3D7, we report here a method of enforcing expression of VSASM-like antigens in this parasite clone by a novel selection method using plasma from semi-immune children with low VSAUM-specific, but high VSASM-specific, IgG reactivity. In addition to the resulting increase in VSA-specific IgG recognition, VSASM-expressing 3D7(3D7-Dodowa1) showed reduced adhesion to CD36. Finally, levels of IgG specific for the VSA expressed by 3D7-Dodowa1 were uniformly higher than those of IgG with specificity for VSA expressed by the unselected 3D7 in plasma samples from geographically and epidemiologically diverse areas of endemic parasite transmission. The described selection method appears a useful tool in the identification of genes encoding VSA involved in severe and life-threatening P. falciparum malaria.

AB - P. falciparum-infected red blood cells (IRBC) can adhere to endothelial host receptors through parasite-encoded, clonally variant surface antigens (VSA). The VSA-mediated IRBC adhesion and the acquired VSA-specific antibody response have both been linked to IRBC organ tropism and disease severity. Parasites isolated from young children with severe malaria (SM) tend to express a limited and conserved set of VSA (VSASM) that are both stronger and more commonly recognized by IgG in the plasma of malaria-exposed individuals than VSA (VSAUM) expressed by parasites causing uncomplicated malaria (UM) in older semi-immune children. Establishment of the genetic mechanism underlying changes in VSA expression in response to in vitro selective pressure is now possible because of the availability of the entire genomic sequence of the P. falciparum clone 3D7. As a first step towards direct molecular identification of VSASM-encoding genes in 3D7, we report here a method of enforcing expression of VSASM-like antigens in this parasite clone by a novel selection method using plasma from semi-immune children with low VSAUM-specific, but high VSASM-specific, IgG reactivity. In addition to the resulting increase in VSA-specific IgG recognition, VSASM-expressing 3D7(3D7-Dodowa1) showed reduced adhesion to CD36. Finally, levels of IgG specific for the VSA expressed by 3D7-Dodowa1 were uniformly higher than those of IgG with specificity for VSA expressed by the unselected 3D7 in plasma samples from geographically and epidemiologically diverse areas of endemic parasite transmission. The described selection method appears a useful tool in the identification of genes encoding VSA involved in severe and life-threatening P. falciparum malaria.

U2 - 10.1111/j.1365-3024.2003.00652.x

DO - 10.1111/j.1365-3024.2003.00652.x

M3 - Journal article

C2 - 14651589

SN - 0141-9838

VL - 25

SP - 421

EP - 427

JO - Parasite Immunology

JF - Parasite Immunology

IS - 8-9

ER -