1. ¹Institute of Agricultural Biotechnology, Timiryazevskaya St. 42, Moscow 127550, Russia
2. ²Gamaleya Research Institute of Epidemiology and Microbiology, Gamaleya St. 18, Moscow 123098, Russia
3. ³Institute of Carcinogenesis, Blokhin Cancer Research Center, Kashirskoe Sh. 24, Moscow 115487, Russia
4. ⁴Department of Molecular Microbiology and Immunology, St Louis University School of Medicine, 1402 South Grand Blvd., St Louis, Missouri 63104, USA

Correspondence: Dr Konstantin Doronin, Department of Molecular Microbiology and Immunology, St Louis University School of Medicine, 1402 South Grand Blvd., St Louis, MO 63104, USA. E-mail: doronink@slu.edu

Received 10 August 2004; Published online 11 March 2005.

Abstract

Avian adenovirus CELO is a novel adenovirus vector system with the advantages of efficient production, high virion stability, and the absence of crossreactivity with Ad5-neutralizing antibodies. In this study, we evaluated the anticancer efficacy of a CELO vector encoding the herpes simplex virus type 1 thymidine kinase, a prodrug-activating therapeutic gene. Vectors carrying the gene for HSV-tk or EGFP under the control of the HCMV promoter in place of the "nonessential" region of the CELO genome were constructed. Anticancer activity of the CELO-TK vector was studied in vitro, in human and murine tumor cells in cell culture, and in vivo, in established subcutaneous murine B16 melanoma tumors in C57BL/6 mice. The CELO-TK vector mediated delivery of functional HSV-tk to tumor cell lines in cell culture. Comparison of the CELO-TK vector to a first-generation human adenovirus type 5 vector Ad5-TK in cultured H1299 cells showed equal levels of functional activity at increasing multiplicities of infection with CELO-based vector. CELO vectors allowed for transduction and expression of EGFP and HSV-tk genes in subcutaneous melanoma tumors in C57BL/6 mice. Intratumoral injections of CELO-TK followed by ganciclovir administration resulted in suppression of tumor growth and significantly increased the median of survival. The results of the study demonstrated the efficacy of CELO vector as a vehicle for the delivery of prodrug-activating genes such as HSV-tk to tumor cells in vitro and in vivo.