Enhanced neuroblastoma transduction for an improved antitumor vaccine

Background, A recent clinical trial of an antineuroblastoma vaccine used ad enovirus serotype 5 (Ad5) vectors to transduce autologous tumor cells with the gene encoding IL-2. A method to improve transduction efficiency was sou ght to enable the use of lower viral titers, especially when in situ adenov iral-mediated tumor cell transduction is considered. Materials and methods. A chimeric adenoviral delivery vector was utilized i n which the fiber head from adenovirus serotype 3 was incorporated into the backbone of Ad5. Since the fiber head protein is responsible for viral att achment to target cells, a different spectrum and range of infectivity migh t result. Both the chimeric (Av9LacZ4) and Ad5 (Av1LacZ4) vectors were cons tructed to carry a beta-galactosidase transgene. The relative transduction efficiency of these two vectors was then evaluated in five tumor-derived sh ort-term neuroblastoma cultures and four established neuroblastoma cell lin es. Enzyme activity was assessed using three different methods: in situ sta ining, flow cytometric analysis, and a quantitative assay. Results. A significant improvement in transduction efficiency of the short- term neuroblastoma cultures with the new chimeric adenovector was demonstra ted. A similar improvement in transduction efficiency was not observed in t he established cell lines, suggesting that the cell surface receptor for th e Ad 3 serotype had been lost in vitro. Increased transduction of tumor cel ls with N-myc amplification was also observed. Conclusions. The newly constructed chimeric adenoviral vector transduces sh ort-term neuroblastoma cultures more efficiently than the standard Ad5 vect or. This vector will permit the use of lower viral titers and may be useful in other adenoviral-based gene-therapy protocols. Increased transgene expr ession in N-myc-amplified cells offers possible selectivity for in situ gen e delivery. (C) 1999 Academic Press.