The invention comprises a plasmid vector, utilizing genetic material that causes high levels of expression of poxvirus genes, and the method of using this genetic material. One preferred embodiment comprises an upstream cis-acting element of a poxvirus gene encoding the major protein component of the poxvirus A-type inclusion. A second preferred embodiment of the invention comprises a downstream cis-acting element of a poxvirus gene encoding the major protein component of the poxvirus A-type inclusion. These elements are inserted upstream and downstream respectively, of selected cloned genes in the plasmid vector to obtain very high levels of expression of the cloned gene.