The pUL17/pUL25/pUL31 complex forms in the absence of pUL18, intact capsids, pUL34, or pUS3. CV1 cells were infected with HSV-1(F), UL18 null, UL34 null, or US3 null viruses. At 18 h after infection cells were lysed and immunoprecipitated with anti-pUL17 (Left) or anti-pUL31 (Right) antibodies. The immunoprecipitated material was then subjected to immunoblotting with anti-pUL25, anti-UL31, or anti-pUL17 antibodies.