PLASMODIUM-FALCIPARUM - SURFACE MODIFICATIONS OF INFECTED ERYTHROCYTES FROM CLINICAL ISOLATES - EVIDENCE OF ANTIGENIC DIVERSITY USING VENEZUELAN HUMAN MALARIAL SERA

Infections of human erythrocytes with the mature asexual blood stages of Plasmodium falciparum result in antigenic changes in the host cell membrane that, by virtue of their position, length of exposure, and cl ose association with functional changes critical to pathogenesis, are a potential important target for host effector mechanisms. These paras ite-induced antigens expressed on the surface of infected erythrocytes have been shown to exhibit considerable polymorphism. An antibody-med iated agglutination assay using malaria serum samples from different r egions of Venezuela has been developed to examine the extent of antige nic diversity of infected red blood cells (IRBC) taken from subjects w ith naturally acquired P. falciparum infections. An important humoral immune recognition of surface molecules from red blood cells infected with a wide variety of clinical isolates of P. falciparum was observed even when sera from individuals experiencing a single episode of mala ria were used. A process of in vivo antigenic variation of surface mol ecules is postulated, since agglutination of IRBC was observed with ac ute heterologous but not autologous sera. When sera obtained from Amer indians inhabiting the Venezuelan Amazon were assayed, a strong immune response to different parasite isolates, including those of another g eographic region, was observed, suggesting the recognition of highly c onserved immunogenic parasitic epitopes in people exposed to multiple malaria infections.