The Plasmodium falciparum knob-associated PfEMP3 antigen is also expressedat pre-erythrocytic stages and induces antibodies which inhibit sporozoiteinvasion

The expression of the pfemp3 gene and the corresponding PfEMP3 knob-associa ted protein in the pre-erythrocytic stages of Plasmodium falciparum was dem onstrated by RT-PCR. Western blots. IFAT and IEM. The antigen was found on the surface of the sporozoite and in the cytoplasm of mature hepatic stage parasites. Immunological cross-reactivity was observed with sporozoites Fro m the rodent malaria parasites Plasmodium yoelii yoelii and Plasmodium berg hei and was exploited to assess a potential role of this protein at the pre -erythrocytic stages. Specific antibodies From immune individuals were foun d to inhibit P. yoelii yoelii and P. berghei sporozoite invasion of primary hepatocyte cultures. PfEMP3 should now be added to the small list of prote ins expressed at the pre-erythrocytic stages of P. falciparum. and its vacc ine potential now deserves to be investigated. (C) 2001 Elsevier Science B. V. All rights reserved.