Cross–reactive antigenic determinants present on different Plasmodium falciparum blood–stage antigens

Summary A gene encoding a previously undescribed antigen of Plasmodium falciparum has been isolated from a genomic expression library by use of a pool of human immune sera. Northern blot analysis indicated that the gene is expressed at the late stages of the intra–erythrocytic cycle. This antigen, 332, contains a series of degenerated amino acid repeats. Human antibodies affinity–purified on the 332 recombinant antigen reacted with a family of parasite proteins that are products of different genes. We identified antigens 11.1 and Pf 155–RESA as members of this family and confirmed, using a human monoclonal antibody, the presence of cross–reacting determinants. The sequences of these antigens also share some structural homologies. The significance of this family of blood–stage antigens is discussed.