SYNTHETIC OLIGONUCLEOTIDE EXPRESSED BY A RECOMBINANT VACCINIA VIRUS ELICITS THERAPEUTIC CTL

P815A is a naturally occurring tumor rejection Ag of the methylcholant hrene-induced murine mastocytoma P815. The gene encoding the Ag P815A, designated P1A, is identical to that encoded in the normal genome of the DBA/2 mouse. A recombinant vaccinia virus (rVV) was constructed th at expressed a synthetic oligonucleotide encoding the minimal determin ant peptide of the tumor-associated Ag. Although the rVV recombinant e xpressing this mini-gene was recognized efficiently in vitro, it was a n ineffective immunogen in vivo. The addition of an endoplasmic reticu lum insertion signal sequence to the NH2 terminus of the minimal deter minant resulted in a rVV that elicited CD8(+) T cells that could lyse P815 mastocytoma cells in vitro and that were therapeutic in vivo. Rec ombinant viruses expressing synthetic oligonucleotide sequences preced ed by the insertion signal sequences allow the expression of Ag direct ly into the endoplasmic reticulum, where binding to MHC class I molecu les is most efficient. Vaccines based on synthetic oligonucleotides co uld be constructed with ease and rapidity but, most importantly, such constructs avoid the dangers associated with the expression of full le ngth genes encoding TAA that are potentially oncogenic.