Evaluation of the thymidine kinase (tk) locus as an insertion site in the highly attenuated vaccinia MVA strain

Abstract
The highly attenuated ‘modified vaccinia Ankara’ (MVA) strain is a potential live vaccine vector. Insertional inactivation of the tk-gene resulted in viruses difficult to purify. Co-integration of a functional fowlpox virus tk-gene allowed easy generation of recombinants, indicating that the genetically stable tk-gene region is a suitable insertion site, if tk-gene activity is substituted.