SDS-PAGE resolution of infected cell proteins that were radiolabeled with 35S-methionine during MVAΔudg (vDG014)-, MVA(udg+)-, or mock-infection of CAN20 and DF-1 cells demonstrated a defect in the production of the protein products of several late genes during MVAΔudg-infection of non-complementing DF-1 cells (Figure 6). The gene discussed is UNG; the disease is infection.