Attenuated adenovirus infection of CLL cells induces cytotoxicity. Primary CLL cells from 7 patients were infected with Ad5dl309, heat-inactivated Ad5dl309 (mock-infected), an E1A deleted adenovirus (E1A−), or an adenovirus with a deletion of E1A and E1B (Pac3). At the indicated times, cell viability was determined by cell counting and trypan blue staining and compared with the viability of uninfected and mock-infected cells. (A) The degree of cytotoxicity seen 4 days after infection of primary CLL with each of the adenoviruses. (B) The degree of cytotoxicity seen 20 days after infection of primary CLL cells with each of the adenoviruses. In both figures, control refers to uninfected cells and mock refers to cells infected with heat-inactivated virus.