Recombinant vaccinia expressing interleukin-2 for cancer gene therapy

Use of a recombinant vaccinia virus expressing human interleukin-2 (IL-2) was evaluated for preparation of tumor vaccines. A/J mice were immunized against neuroblastoma (C1300) cells using a preparation of C1300 cells infected/transfected with the recombinant virus, vCF13, expressing IL-2. A second recombinant vaccinia, vSC8, expressing Escherichia coli beta-galactosidase, was used as a control. After three weekly immunizations with virus-transfected cells, the mice were challenged with 1 x 10(6) unmodified C1300 cells and tumor development was monitored. Tumor development in the mice was inhibited by immunization with vCF13-transfected cells, compared to those vaccinated with vSC8-transfected cells (P < .008). A group of mice (7/15) immunized with vCF13-transfected cells followed by tumor challenge survived more than 60 days, at which time all mice immunized with the control vaccine were dead (p < .006). Five of the mice treated with the vCF13 vaccine were alive for more than 75 days (P < .05), after which they were rechallenged with another dose of 1 x 10(6) unmodified tumor cells. Tumor development was not apparent in these mice for more than 45 days following the second challenge, suggesting that these mice were completely protected by this immunization. These results demonstrate that recombinant vaccinia virus expressing IL-2 may be useful for cancer gene therapy.