A CARCINOEMBRYONIC ANTIGEN POLYNUCLEOTIDE VACCINE FOR HUMAN CLINICAL USE

We have constructed a plasmid DNA encoding the full-length complementa ry DNA for human carcinoembryonic antigen (CEA) under transcriptional regulatory control of the cytomegalovirus early promoter/enhancer (pCE A) and demonstrated that this plasmid can function as a polynucleotide vaccine to elicit a CEA-specific immune response. This immune respons e protects against tumor challenge with syngeneic CEA-transduced colon carcinoma cells in mice. In the present work, the pCEA construct and purification method were modified to eliminate nonessential viral sequ ences, the ampicillin selectable marker, mutagens, and endotoxin to pr oduce a reagent suitable for human clinical trials. The human use plas mid (pGT37) directs CEA expression al levels comparable with the origi nal pCEA plasmid and can be propagated to yield large quantities of pl asmid DNA based on kanamycin selection. A simple extraction technique greatly reduces contamination by endotoxin. Six weekly intramuscular i njections of pGT37 elicited CEA-specific lymphoblastic transformation and antibody response in five of five mice and fully protected 10 of 1 0 mice against tumor challenge with syngeneic CEA-expressing colon can cer cells 42 days from the first plasmid injection. Thus, pGT37 encodi ng a tumor-associated antigen (CEA) has been shown to elicit cellular and humoral immune responses and mediate antitumor effects in vivo. Th is plasmid is suitable for human use and can be easily propagated in t he laboratory.