Safety and immunogenicity of a three-component blood-stage malaria vaccinein adults living in an endemic area of Papua New Guinea

A Phase I safety and immunogenicity study with a three-component blood-stag e malaria vaccine was conducted in adult male subjects living in an endemic area of Papua New Guinea. The preparations were recombinant proteins which corresponded to parts of the two merozoite surface proteins of Plasmodium falciparum (MSP1 and 2), and of the ring-infected erythrocyte surface antig en (RESA). The three proteins were emulsified with the adjuvant Montanide I SA720. Ten subjects were injected twice (four weeks apart) with the vaccine formulation and two with the adjuvant alone. Mild pain at the site of inje ction was reported by about half of the subjects but no systemic reaction r elated to the formulation occurred. There was a sharp rise in geometric mea n stimulation index after the second dose compared to baseline for MSPI and RESA, while the rise was small for MSP2. Geometric mean antibody titres in creased for MSP1 during the study, whereas they hardly changed for MSP2 and RESA. The vaccine formulation was safe when used in an already immune popu lation. The vaccine induced good cellular responses, especially for MSP1 an d RESA. Boosting of humoral responses was weak, probably because of high ba seline antibody levels. (C) 2000 Elsevier Science Ltd. All rights reserved.