抄録
Var gene is a multicopy family gene and encodes the antigenic protein, Plasmodium falciparum infected-erythrocytes membrane protein-1(PfEMP-1). Here we identified expressed var gene transcripts and their cytoadherent characteristics. Random cloning and sequencing analysis of DBL-alpha domain of var gene transcripts expressed in matured parasites revealed that approximately half of all cDNA clones were derived from a single gene, var-1/ItG. Immunofluorescence assay (IFA) showed that approximately 40% of ItG parasites expressed PfEMP-1 encoded by var-1/ItG-1 (PfEMP-1/ItG-1). Parasitized RBCs (PRBCs) selected for binding to C32 cells (ItG/C32), where the PfEMP-1/ItG-1-positive PRBC population increased to 78%, showed an increased cytoadhesion to C32 cells (241 PRBCs per 300 C32 cells) compared to originally cultured PRBCs (9 PRBCs per 300 C32 cells). To evaluate the contribution of PfEMP-1/ItG-1 in C32 adherence, PfEMP-1/ItG-1-enriched fraction (ItG/8A) was prepared by limiting dilution. In ItG/8A fraction, 83 % of the PRBCs were PfEMP-1/ItG-1 positive and only var-1/ItG was detected in the sequence analysis. PRBCs in ItG/8A fraction also showed higher cytoadhesion to C32 cells (153 PRBCs bound per 300 C32 cells). These results demonstrated that PfEMP-1/ItG-1 is expressed on ItG parasite-infected RBCs and contributes to the cytoadherent phenotype of ItG parasites to C32 cells.
