Antigenic Variation in Plasmodium falciparum and Other Plasmodium Species

This chapter discusses the antigenic variation in plasmodium falciparum (. P. falciparum), which depends on an insect vector for transmission and completion of its life cycle. The manifestations of P. falciparum evasion on the immune control are the occurrence of continued super-infections with new parasites, the paucity of sterile immunity, the establishment of chronic asymptomatic parasitaemia, or the recrudescence of parasites. Instrumental in this evasion function is the expression of parasite-derived proteins on the surface of the infected erythrocyte (IE) with the ability to undergo clonal antigenic variation. Antigenic diversity of these multigene families is also another way of increasing the repertoire of genes. Antigenic diversity can be defined as the expression of antigenically different forms of parasite gene products by parasites of different genotype within any given isolate. This heterogeneity is maintained by genetic recombination, in addition to mutation. The diversification of antigens may confer on the parasite the ability to infect a host that has previously only been exposed to parasites of a different genotype, as the immunity directed at these parasites is species-specific and strain-specific. The diversity of adhesion mechanisms used by intraerythrocytic stages of P. falciparum is to ensure sequestration and the plasticity of the evasion systems that the parasite has developed as a response to immune pressure in the host.