TY - JOUR

T1 - Plasmodium falciparum variant surface antigen expression varies between isolates causing severe and nonsevere malaria and is modified by acquired immunity

AU - Nielsen, Morten A

AU - Staalsoe, Trine

AU - Kurtzhals, Jørgen

AU - Goka, Bamenla Q

AU - Dodoo, Daniel

AU - Alifrangis, Michael

AU - Theander, Thor G

AU - Akanmori, Bartholomew D

AU - Hviid, Lars

N1 - Keywords: Adult; Age Factors; Anemia; Animals; Antibodies, Protozoan; Antibody Specificity; Antigen-Antibody Reactions; Antigens, Protozoan; Child; Child, Preschool; Cloning, Molecular; Erythrocytes; Humans; Immunity, Active; Malaria, Cerebral; Malaria, Falciparum; Merozoite Surface Protein 1; Plasmodium falciparum; Protozoan Proteins; Severity of Illness Index

PY - 2002

Y1 - 2002

N2 - In areas of endemic parasite transmission, protective immunity to Plasmodium falciparum malaria is acquired over several years with numerous disease episodes. Acquisition of Abs to parasite-encoded variant surface Ags (VSA) on the infected erythrocyte membrane is important in the development of immunity, as disease-causing parasites appear to be those not controlled by preexisting VSA-specific Abs. In this work we report that VSA expressed by parasites from young Ghanaian children with P. falciparum malaria were commonly and strongly recognized by plasma Abs from healthy children in the same area, whereas recognition of VSA expressed by parasites from older children was weaker and less frequent. Independent of this, parasites isolated from children with severe malaria (cerebral malaria and severe anemia) were better recognized by VSA-specific plasma Abs than parasites obtained from children with nonsevere disease. This was not due to a higher infection multiplicity in younger patients or in patients with severe disease. Our data suggest that acquisition of VSA-specific Ab responses gradually restricts the VSA repertoire that is compatible with parasite survival in the semi-immune host. This appears to limit the risk of severe disease by discriminating against the expression of VSA likely to cause life-threatening complications, such as cerebral malaria and severe anemia. Such VSA seem to be preferred by parasites infecting a nonimmune host, suggesting that VSA expression and switching are not random, and that the VSA expression pattern is modulated by immunity. This opens the possibility of developing morbidity-reducing vaccines targeting a limited subset of common and particularly virulent VSA.

AB - In areas of endemic parasite transmission, protective immunity to Plasmodium falciparum malaria is acquired over several years with numerous disease episodes. Acquisition of Abs to parasite-encoded variant surface Ags (VSA) on the infected erythrocyte membrane is important in the development of immunity, as disease-causing parasites appear to be those not controlled by preexisting VSA-specific Abs. In this work we report that VSA expressed by parasites from young Ghanaian children with P. falciparum malaria were commonly and strongly recognized by plasma Abs from healthy children in the same area, whereas recognition of VSA expressed by parasites from older children was weaker and less frequent. Independent of this, parasites isolated from children with severe malaria (cerebral malaria and severe anemia) were better recognized by VSA-specific plasma Abs than parasites obtained from children with nonsevere disease. This was not due to a higher infection multiplicity in younger patients or in patients with severe disease. Our data suggest that acquisition of VSA-specific Ab responses gradually restricts the VSA repertoire that is compatible with parasite survival in the semi-immune host. This appears to limit the risk of severe disease by discriminating against the expression of VSA likely to cause life-threatening complications, such as cerebral malaria and severe anemia. Such VSA seem to be preferred by parasites infecting a nonimmune host, suggesting that VSA expression and switching are not random, and that the VSA expression pattern is modulated by immunity. This opens the possibility of developing morbidity-reducing vaccines targeting a limited subset of common and particularly virulent VSA.

M3 - Journal article

C2 - 11907103

VL - 168

SP - 3444

EP - 3450

JO - Journal of Immunology

JF - Journal of Immunology

SN - 0022-1767

IS - 7

ER -