Recombinant fowlpox virus forin vitrogene delivery to pancreatic islet tissue

Construction and characterization of novel fowlpox virus shuttle vectors

Viral vectors are important vehicles in vaccine research. Avipoxviruses including fowlpox virus (FPV) play major roles in viral vaccine vector development for the prevention and therapy of human and other veterinary diseases due to their immunomodulatory effects and safety profile. Recently, we analyzed the genomic and proteomic backgrounds of the Chinese FPV282E4 strain. Based on analysis of the whole genome of FPV282E4, the FPV150 and FPV193 loci were chosen as insertion sites for foreign genes, and two shuttle vectors with a triple-gene expression cassette were designed and constructed. Homologous recombination between the FPV virus genome and sequences within the shuttle plasmids in infected cells was confirmed. The recombinants were obtained through several rounds of plaque purification using enhanced green fluorescent protein as a reporter and evaluated for the correct expression of foreign genes in vitro using RT-PCR, real-time PCR and Western blotting. Morphogenesis and growth kinetics were assayed via transmission electron microscopy and viral titering, respectively. Results showed that recombinant viruses were generated and correctly expressed foreign genes in CEF, BHK-21 and 293T cells. At least three different exogenous genes could be expressed simultaneously and stably over multiple passages. Additionally, the FPV150 mutation, FPV193 deletion and insertion of foreign genes did not affect the morphogenesis, replication and proliferation of recombinant viruses in cells. Our study contributes to the improvement of FPV vectors for multivalent vaccines.

Antitumor effects of a recombinant fowlpox virus expressing Apoptin in vivo and in vitro

Apoptin is a chicken anemia virus-derived, p53-independent, bcl-2-insensitive apoptotic protein with the ability to specifically induce apoptosis in tumor cells. To explore the use of the Apoptin gene in cancer gene therapy, we constructed a recombinant fowlpox virus expressing the Apoptin protein (vFV-Apoptin) and compared the tumor-killing activity of the recombinant virus with that of wild-type fowlpox virus in the human hepatoma cell line HepG2. We found that although cells were somewhat resistant to the basal cytotoxic effect of wild-type fowlpox virus, infection with vFV-Apoptin caused a pronounced, additional cytotoxic effect. Furthermore, cell death and disruption of tumor integrity were apparent in the vFV-Apoptin-infected cells. We also tested whether fowlpox virus-mediated expression of Apoptin in tumor cells could stimulate an antitumor effect by injecting aggressive subcutaneous tumors derived from H22 mouse hepatoma cells in C57BL/6 mice with vFV-Apoptin. We found that fowlpox virus-mediated intratumoral expression of the Apoptin gene can induce protective and therapeutic antitumor effects and significantly increase survival. Taken together, these data indicate that infection of tumors with fowlpox virus expressing Apoptin inhibits tumor growth, induces apoptosis and may be an effective cancer treatment.