Antibodies against ribosomal phosphoprotein PO of Plasmodium falciparum protect mice against challenge with Plasmodium yoelii

Antibodies against the Plasmodium falciparum P0 ribosomal phosphoprotein (P fP0) have been detected exclusively but extensively in malaria-immune perso ns. Polyclonal rabbit and mice sera were raised against two recombinant pol ypeptides of P. falciparum P0 protein, PfP0N and PfP0C, covering amino acid s 17 to 61 and the remaining amino acids 61 to 316, respectively. Sera agai nst both these domains detected a 35-kDa protein from Plasmodium yoelii sub sp, yoelii, a rodent malarial parasite, and stained the surface of merozoit es in immunofluorescence assays. Total immunoglobulin G (IgG) purified from rabbit and mouse anti-PfP0 sera by ammonium sulfate and DEAE-cellulose chr omatography was used for passive transfer experiments in mice. Mice passive ly immunized with both anti-PfP0N and anti-PfP0C showed distinctly lower le vels of parasitemia than control mice, With immunizations on days -1, 0, 1, 3, and 5, about 50% of both sets of mice receiving anti-PfP0N and anti-PfP 0C cleared the lethal 17XL strain of P, yoelii and revived by day 25, All t he control mice died by day 10, By extending the immunization schedule, the survival period of the mice could be extended for every mouse that receive d anti-PfP0 IgG, These data demonstrate the cross-protection of the anti-Pf P0 IgG and establish parasite P0 protein as a target for invasion-blocking antibodies.