INDUCTION IN-VITRO OF PRIMARY CYTOTOXIC T-LYMPHOCYTE RESPONSES WITH DNA ENCODING HERPES-SIMPLEX VIRUS PROTEINS

Vaccines which successfully protect against virus infections usually n eed to induce a broadly reactive immune response which includes the in duction of cytotoxic T lymphocytes (CTL). In this study, we have used a convenient in vitro approach to investigate if plasmid DNAs encoding proteins of herpes simplex virus (HSV) are capable of inducing primar y CD8(+) CTL. Dendritic cells or macrophages were transfected with eit her plasmid DNA encoding glycoprotein B or DNA encoding the immediate- early protein ICP27. These antigen-presenting cells (APC) were then us ed to stimulate enriched populations of naive T cells in microcultures for 5 days in vitro. Antigen-specific CD8(+) CTL which reacted both w ith specific protein-expressing targets and with syngeneic targets inf ected with HSV could be demonstrated. Dendritic cells, as APC, generat ed the maximal responses, but such cells needed to be transfected with DNA in the presence of a cationic lipid. However, macrophages could a ct as APC when they were exposed to purified DNA; HSV-primed splenocyt es mere also shown to generate specific CTL responses when they were s timulated with purified DNA encoding ICP27. The novel approach describ ed in this paper promises to be extremely useful, since defining immun ogenicity profiles and identifying epitopes on viral proteins should b e easier and more convenient when working with DNA and investigating v ariables in vitro. This is particularly the case with complex viruses such as HSV, most of whose encoded proteins have yet to be isolated in sufficient quantity or purity to perform in vivo immunological studie s.