The erythrocytic stage of Plasmodium falciparum (Pf) kills an estimated 2 million children annually. Pf invades erythrocytes (RBCs) by attaching to surface receptors, one of which includes sialic acids on glycophorinA. Region II of EBA-175 is a RBC receptor-binding ligand of Pf, the binding of which is sialic acid dependent. Region II DNA vaccines induce antibodies that block EBA-175 binding to RBCs and inhibit Pf invasion of RBCs. Region II DNA vaccines have not induced antibody titers high enough to consistently protect monkeys against Pf. However, upon Pf challenge, which in effect provides for protein boosting, anti-region II blocking antibodies were increased 10-fold. When a baculovirus recombinant EBA-175 region II protein was delivered in adjuvant to DNA vaccine primed or naive animals, similarly high antibody titers were achieved. However, the yield of this baculovirus expressed protein is too low to be commercially viable. We have GMP experience with a high yield Pichia pastoris recombinant expression system.
The specific aim i s thus to express region II protein in P. pastoris. Short term goals for recombinant region II protein are: 1) optimization of expression, fermentation and purification, 2) biochemical, and functional characterization, 3) study of safety, immunogenicity, and efficacy in Aotus monkeys. The long-term goal is large-scale GMP production of a commercially viable region II protein for Phase I/II human malaria vaccine studies alone and/or in combination with a region II DNA vaccine.
Effective approach for expression of recombinant PF proteins for malaria vaccine development for DNA prime/potein boost or protein alone vaccine.
