Characterization of conserved T- and B-cell epitopes in Plasmodium falciparum major merozoite surface protein 1

Vaccines for P. falciparum will need to contain both T- and B-cell epitopes . Conserved epitopes are the most desirable, but they are often poorly immu nogenic. The major merozoite surface protein 1 (MSP-1) is currently a leadi ng vaccine candidate antigen. In this study, six peptides from conserved or partly conserved regions of MSP-1 were evaluated for immunogenicity in B10 congenic mice. Following immunization with the peptides, murine T cells we re tested for the ability to proliferate in vitro and antibody responses to MSP-1 were evaluated in vivo. The results showed that one highly conserved sequence (MSP-1#1, VTHESYQELVKKLEALEDAV; located at amino acid positions 2 0 to 39) and one partly conserved sequence (MSP-1#23, GLFHKEKMIL NEEEITTKGA ; located at positions 44 to 63) contained both T- and B-cell epitopes. Imm unization of mice with these peptides resulted in T-cell proliferation and enhanced production of antibody to MSP-1 upon exposure to merozoites. MSP-1 #1 stimulated T-cell responses in three of the six strains of mice evaluate d, whereas MSP-1#23 was immunogenic in only one strain. Immunization with t he other four peptides resulted in T-cell responses to the peptides, but no ne of the resulting peptide-specific T cells recognized native MSP-1. These results demonstrate that two sequences located in the N terminus of MSP-1 can induce T- and B-cell responses following immunization in a murine model . Clearly, these sequences merit further consideration for inclusion in a v accine for malaria.