INDUCTION OF MURINE CYTOTOXIC T-LYMPHOCYTES AGAINST PLASMODIUM-FALCIPARUM SPOROZOITE SURFACE PROTEIN-2

Sporozoite surface protein 2 has been identified as a target of malari a vaccines designed to produce protective CD8(+) cytotoxic T lymphocyt es (CTL) because mice immunized with mastocytoma cells expressing a fr agment of Plasmodium yoelii sporozoite surface protein 2 (PySSP2) are protected against malaria by an immune response that requires CD8(+) C TL. To define CTL epitopes in the Plasmodium falciparum sporozoite sur face protein 2 (PfSSP2), spleen cells (SC) from mice immunized with ir radiated sporozoites (irr spz) were stimulated with synthetic peptides , and these effecters were tested for cytolytic activity against pepti de-pulsed, major histocompatibility complex (MHC)-matched targets. Two peptides containing CTL epitopes, A6 (Pf SSP2 3D7 214-233) and BH1 (P f SSP2 3D7 3-11) were identified in bulk cultures of SC from immune C5 7BL/6 mice, and by production of CTL lines. Immunization with recombin ant vaccinia expressing the full length PfSSP2 induced antigen specifi c, MHC-restricted, CD8(+) T cell-dependent cytolytic activity against these two peptides. Finally CTL were induced by immunization with a ba cteria-derived recombinant fragment of PfSSP2 (rPfSSP2) mixed with a l iposomal formulation containing a cationic lipid (Lipofectin(R) Reagen t, LPF). Induced CTL lysed target cells pulsed with peptide A6 or with LPF/rPfSSP2, but not targets pulsed with only rPfSSP2. These studies demonstrate that CTL specific to PfSSP2 are present in C57BL/6 mice an d that immunization with purified rPfSSP2 delivered with LPF induces a cytotoxic T cell response.