Rifins: A second family of clonally variant proteins expressed on the surface of red cells infected with Plasmodium falciparum

Many pathogens evade the host immune response or adapt to their environment by expressing surface proteins that undergo rapid switching. In the case o f Plasmodium falciparum, products of a multigene family known as var are ex pressed on the surface of infected red cells, where they undergo clonal ant igenic variation and contribute to malaria pathogenesis by mediating adhesi on to a variety of host endothelial receptors and to uninfected red blood c ells by forming rosettes, Herein we show that a second gene family, rif, wh ich is associated with var at subtelomeric sites in the genome, encodes clo nally variant proteins (rifins) that are expressed on the infected red cell surface, Their high copy number, sequence variability, and red cell surfac e location indicate an important role for rifins in malaria host-parasite i nteraction.