Evaluation of E1B - mutant Replicating Adenoviruses for Cancer Gene Therapy

Abstract

Purpose: Gene-attenuated replication-competent adenoviruses are emerging as a promising new modality for the treatment of cancer. In an effort to continually improve upon cancer gene therapy, we have modified gene- attenuated replication-competent adenoviruses so as to cause them to replicate efficiently and lyse the infected cancer cells more effectively. Materials and Methods: We modified the E1 region of the adenovirus (Ad) systematically, generating Ad-Δ E1B19, Ad-ΔE1B55, Ad-ΔE1B19/55, and Ad-WT. The cytopathic effects (CPE) and viral replication of these four gene modified adenoviruses were compared, and the morphology and DNA fragmentation of the infected cells was evaluated. Results: Among the constructed adenoviruses , E1B 19kD-inactivated adenovirus (Ad-ΔE1B19) was the most potent, inducing the larges t-sized plaques and marked CPE. Moreover, cells infected with Ad-ΔE1B19 showed complete cell lysis with disinteg rated cellular structure whereas cells infected with Ad-WT maintained intact cellular and nuclear membrane with properly structured organelles. TUNEL assay was also used to monitor DNA integrity, and amore profound induction of apoptos is was observed in the Ad-ΔE1B19 infected cells in comparis on to wild type adenovirus infected cells. Conclusion: We demonstrate that the inactivation of the E1B19kD gene in a replicating adenovirus leads to in creased CPE, rapid viral release, improvedcell-to-cell viral spread and increased induction of apoptosis.