Immunization of rabbits with a modified vaccinia Ankara recombinant virus bearing the HIV envelope antigen on its outer membrane.

Modified vaccinia virus Ankara (MVA) is a highly attenuated strain of vaccinia virus, which propagates efficiently in chicken embryo fibroblasts but fails to complete its growth cycle in many types of mammalian cells. We constructed a recombinant virus MVA/EK5, which has a chimeric gene encoding for the extracellular domain of the HIV envelope protein fused to the cytoplasmic and transmembrane domain of the B5R protein of vaccinia virus. The fused HIV envelope antigen was expressed in the African green monkey kidney BS-C-1 cells infected with the recombinant virus. This virus, which had been grown in chicken embryo fibroblasts, induced in rabbits antibodies against the HIV envelope antigen, in addition to those against poxvirus.