Molecular and immunological analysis of genetic prostate specific antigen (PSA) vaccine

Nucleic acid immunization has been investigated as immunotherapy for infect ious diseases as well as for treating specific types of cancers. In this ap proach, nucleic acid expression cassettes are directly inoculated into the host, whose transfected cells become the production source of novel and pos sibly immunologically foreign protein, We have developed a DNA vaccine cons truct which encodes for PSA by cloning a cDNA for PSA into a mammalian expr ession vector under control of a CMV promoter, We investigated and characte rized the immunogenicity of PSA DNA expression cassettes in mice, PSA-speci fic immune responses induced in vivo by immunization were characterized by enzyme-linked immunosorbent assay (ELISA), T helper proliferation cytotoxic T lymphocyte (CTL), and flow cytometry assays, We observed a strong and pe rsistent antibody response against PSA for at least 180 days following immu nization. In addition, a significant T helper cell proliferation was observ ed against PSA protein, Using synthetic peptides spanning the PSA open fram e, we identified four dominant T helper epitopes of PSA, Furthermore, immun ization with PSA plasmid induced MHC Class I CD8+ T cell-restricted cytotox ic T lymphocyte response against tumor cell targets expressing PSA, The pro state represents a very specific functional organ critical for reproduction but not for the health and survival of the individual. Understanding the i mmunogenicity of PSA DNA immunization cassettes offers insight into the pos sible use of this tumor-associated antigen as a target for immunotherapy, T hese results demonstrate the ability of the genetic PSA to serve as a speci fic immune target capable of generating both humoral and cellular immune re sponses in vivo.