Induction of cross-reactive immune responses to NTS-DBL-1α/x of PfEMP1 and in vivo protection on challenge with Plasmodium falciparum

Abstract: The interactions of Plasmodium falciparum infected erythrocytes parasitized red blood cells (pRBC) with endothelial receptors and erythrocytes are mediated by multiple Duffy-binding like (DBL) and cysteine-rich interdomain region (CIDR) domains harboured in the Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). The success of a subunit vaccine based on PfEMP1 depends on its ability to elicit cross-reactive responses to a substantial number of PfEMP1 variants. We have here evaluated serological PfEMP1 cross-reactivity by immunizing rats with phylogenetically diverse recombinant NTS-DBL-1α/x fusion domains from the 3D7 genome parasite emulsified in Montanide ISA 720. Cross-reactivity was elicited to these diverse DBL-1α/x domains as measured by ELISA and by immunoblotting. Employing a novel in vivo model of human infected erythrocyte sequestration, immunized animals were challenged with the FCR3S1.2 clone and cross-protection in terms of reduction in lung sequestration amounting to approximately 50% was demonstrated. Our results suggest that immunization with phylogenetically distant DBL-1α/x variants, can elicit partial cross-protection to challenge with the parasites harbouring a distant variant. These observations have implications for the design of multi-component vaccines against P. falciparum malaria. [Copyright &y& Elsevier]