SIMULTANEOUS INDUCTION OF MULTIPLE ANTIGEN-SPECIFIC CYTOTOXIC T-LYMPHOCYTES IN NONHUMAN-PRIMATES BY IMMUNIZATION WITH A MIXTURE OF 4 PLASMODIUM-FALCIPARUM DNA PLASMIDS

CD8(+) T cells have been implicated as critical effector cells in prot ective immunity against malaria parasites developing within hepatocyte s, A vaccine that protects against malaria by inducing CD8(+) T cells will probably have to include multiple epitopes on the same protein or different proteins, because of parasite polymorphism and genetic rest riction of T-cell responses. To determine if CD8(+) T-cell responses a gainst multiple P. falciparum proteins can be induced in primates by i mmunization with plasmid DNA, rhesus monkeys were immunized intramuscu larly with a mixture of DNA plasmids encoding four P. falciparum prote ins or with individual plasmids. All six monkeys immunized with PfCSP DNA, seven of nine immunized with PfSSP2 DNA, and five of six immunize d with PfExp-1 or PfLSA-1 DNA had detectable antigen-specific cytotoxi c T lymphocytes (CTL) after in vitro restimulation of peripheral blood mononuclear cells. CTL activity was genetically restricted and depend ent on CD8(+) T cells. By providing the first evidence for primates th at immunization with a mixture of DNA plasmids induces CD8(+) T-cell r esponses against all the components of the mixture, these studies prov ide the foundation for multigene immunization of humans.