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Abstract

Malaria causes 300–500 million new infections and 1-2 million deaths annually, and immunoprotection achieved by the most successful vaccine is still partial and short lived. MAEBL is a chimeric molecule expressed in infected erythrocytes and possesses amino terminal cysteine-rich, a transmembrane and a cytoplasmatic domain. Th is molecule also contains two other domains (M1 and M2) involved in parasite attachment to red blood cells, and is also expressed in salivary glands sporozoitesand in infected hepatocytes. Here, we amplifi ed, cloned and expressed Plasmodium yoelii MAEBL-M2 domain, in eukaryotic (pcDNA3) and prokaryotic (pet28a) vectors, to be used for injection as a recombinant protein (rM2-MAEBL) and as a naked DNA (M2pcDNA3) in DNA (Prime)–Protein (Boost) immunization regimen. Mice immunized with four doses of rM2-MAEBLin Freund adjuvant (CFA/IFA) or primed with M2pcDNA3 followed by three doses of rM2-MAEBL displayed high levels of antibodies against the recombinant protein. Aft er challenge with P. yoeliilethal strain, a signifi cant reduction on parasitemia levels and protection of 90% or 100% were observed,respectively in the group immunized with the recombinant proteinor with DNA (Prime)–Protein (Boost) in comparison to CFA/IFA injected animals.Moreover, in immunofl uorescence assays antisera harvested from mice immunized with rM2-MAEBL or DNA (Prime)–Protein(Boost) recognizednative protein on free P. yoelii or P. falciparum merozoites, and inhibited up to 51% P. falciparum (3D7) merozoite reinvasion in comparison to CFA/IFA group. Collectively, these data confi rm the potential use of this antigen as a vaccine candidate against malaria blood forms, and open perspectives for the development of an experimental vaccine targeting erythrocytic and preerythrocytic stages of the parasite.