The efficiency of viruses in cancer therapy is enhanced by proteins that mediate the fusion of infected cells with their neighbors. It was reported that replication-competent adenovirus particles can spread between nuclei within fusion-generated syncytia. To assess this conjecture, we generated fusogenic adenoviruses that express a balanced ratio of the F and H glycoproteins of measles virus. The viruses displayed enhancedcytotoxicity but largely unchanged replication efficiencies compared to a

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... nonfusogenic virus. Most notably, thevirus genomes did not spread through fusion-generated multinuclear cells. Hence, adenovirus replication insyncytia remains largely restricted to initially transduced nuclei.