Recombinant vaccines hold great promise for the prevention and therapy of infectious diseases and cancer. We have explored the use of polk) virus as a recombinant vector to deliver genes into cells for the purpose of vaccination. For our studies, we have chosen to express the gene-encoding carcinoembryonic antigen (CEA) using a novel poliovirus vector. We have constructed a recombinant CEA-poliovirus repticon in which the CEA gene was substituted for the poliovirus capsid gene. Following in vitro transcription, the RN A was transfected into cells to demonstrate CEA expression. We found that a genome in which the region encoding the signal sequence of the CEA protein (amino acids 1-34) was removed was replication competent (i.e., referred to as a replicon). We encapsidated the CEA-poliovirus replkon by transfecting this RNA into cells previously infected with a recombinant vaccinia virus (W-Pl) which expresses the poliovirus capsid protein (P1). Serial passage in the presence of W-P1 resulted in the generation of stocks of these encapsidated replicons. Infection of cells with the encapsidated repikon containing the CEA-poliovirus genome resulted in expression of the CEA protein. To test immunogenidty, mice susceptible to poliovirus were given three doses of the encapsidated replicons via the i.m. route. By the third administration, a CEA-specific antibody response was detected. Potential future use of the poliovirus replicon system as both a parenteral and oral vaccine vector is discussed. © 1994, American Association for Cancer Research. All rights reserved.