Characterization of the vaccinia MVA hemagglutinin gene locus and its evaluation as an insertion site for foreign genes.

The 'Modified Vaccinia Ankara' (MVA) strain is a potential live vaccine vector. The use of the hemagglutinin (ha) gene of the MVA strain as an insertion site for foreign genes was evaluated. To identify the molecular basis of the hemagglutinin-negative (HA-) phenotype of MVA, the ha gene and the region around this gene were sequenced. Amino acid (aa) sequence comparisons with functional hemagglutinins of other vaccinia strains predicted a functional polypeptide. The late part of the promoter region of the ha gene, however, was deleted, causing the apparent loss of the ha gene function. Nevertheless, insertion of foreign DNA into the ha gene allowed generation of functional recombinant viruses, indicating that the ha-gene region is a suitable insertion site.