Peptide vaccines derived from a malarial surface antigen: effects of dose and adjuvants on immunogenicity

Peptides P2122 (CKNNNSTNSGI) and P513 (CSQRSTNSAST) containing an epitope of a malarial surface antigen (MSA2) recognised by inhibitory monoclonal antibodies were conjugated to diphtheria toxoid (DT) protein and formulated with various gel-based and water in oil emulsion adjuvants in vaccine trials in mice and rabbits. The P2122-DT construct was effective in raising antibodies reactive with both the immunising peptide and the native antigen. Effective adjuvanticity as measured by the titre of the anti-peptide or anti-protein response in mice varied in the order: Algammulin, Montanide ISA 50 greater than or equal to Freund's adjuvant, Montanide ISA 708, 721, 70 much greater than alum, Squalene Arlacel greater than SAF-1. A similar order of adjuvant efficacy: Freund's greater than alum greater than Squalene Arlacel greater than SAF-1, was observed in rabbits.