IDENTIFICATION AND CHARACTERIZATION OF THE PROTECTIVE HEPATOCYTE ERYTHROCYTE PROTEIN-17 KDA GENE OF PLASMODIUM-YOELII, HOMOLOG OF PLASMODIUM-FALCIPARUM EXPORTED PROTEIN-1

We recently reported the discovery of a 17-kDa Plasmodium yoelii prote in expressed in infected hepatocytes and erythrocytes, P. yoelii hepat ocyte erythrocyte protein 17 (PyHEP17), and have demonstrated that thi s protein is a target of protective antibodies and T cells, Here, we r eport the identification and characterization of the gene encoding thi s protein and reveal that it is composed of two exons, Immunization of mice with PyHEP17 plasmid DNA induces antibodies, cytotoxic T lymphoc ytes, and protective immunity directed against the infected hepatocyte , Based on extensive sequence homology, expression pattern, and antige nic cross-reactivity, the Plasmodium falciparum homolog of PyHEP17 is identified as the protein known as exported protein-1 (PfExp-1), also called antigen 5.1, circumsporozoite related antigen, or QF116. Identi ty between PyHEP17 and PfExp-1 is 37% at the amino acid level (60/161 residues), mapping primarily to two regions within the second exon of 73% (16/22 residues) and 71% (25/35 residues) identity, On this basis, PfExp-1 is proposed as an important component of pre-erythrocytic hum an malaria vaccines.