TRANSIENT MARKER STABILIZATION - A GENERAL PROCEDURE TO CONSTRUCT MARKER-FREE RECOMBINANT VACCINIA VIRUS

Recombinant vaccinia viruses based on the highly attenuated Modified V accinia Ankara (MVA) strain expressing HIV-1 antigen genes were constr ucted by a novel procedure involving the transient use of two marker g enes. The selectable markers used, the Escherichia coli guanine phosph oribosyltransferase (gpt) and the beta-galactosidase (lacZ) genes, are not retained within the final recombinant virus. The transient marker stabilisation (TMS) procedure allows the generation of marker-free re combinant viruses in a series of simple plaque purification steps. HIV -1 gag pol genes were inserted into two loci of vaccinia MVA demonstra ting the efficiency of the procedure.