Furthermore, we demonstrate in a relevant non-human primate model that a udg− AIDS vaccine vector, MVAΔudg-gag, elicited 2–4-fold higher frequencies of HIV Gag-specific CD8 and CD4 T cells in immunized macaques, as compared to a udg+ control vector (MVA-gag) that expresses an identical HIV gag transgene. The gene discussed is CD8A; the disease is AIDS.