Temperature-sensitive viruses induce cytotoxicity after infection of CLL cells. CLL cells from patient no. 7 were infected with a temperature-sensitive viruses containing mutations in the E2A gene (Ad5ts125) at the restrictive (37°C) and permissive (33°C) temperatures. Cytotoxicity was determined by cell counting and trypan blue staining at various times after infection. Control refers to uninfected cells and mock refers to cells infected with heat-inactivated virus. (⊡) Mock infection; (□) infection with Ad5dl309; (▵) infection with Ad5ts125 at 33°C; (◊) infection with Ad5ts125 at 37°C.