Induction of CD4(+) T cell-dependent CD8(+) type 1 responses in humans by a malaria DNA vaccine

We assessed immunogenicity of a malaria DNA vaccine administered by needle i.m. or needleless jet injection [i.m. or i.m./intradermally (i.d.)] in 14 volunteers. Antigen-specific IFN-gamma responses were detected by enzyme-li nked immunospot (ELISPOT) assays in all subjects to multiple 9- to 23-aa pe ptides containing class I and/or class II restricted epitopes, and were dep endent on both CD8(+) and CD4(+) T cells. Overall, frequency of response wa s significantly greater after i.m. jet injection. CD8(+)-dependent cytotoxi c T lymphocytes (CTL) were detected in 8/14 volunteers. Demonstration in hu mans of elicitation of the class I restricted IFN-gamma responses we believ e necessary for protection against the liver stage of malaria parasites bri ngs us closer to an effective malaria vaccine.