Induction of antitumor response to fibrosarcoma by Newcastle disease virus-infected tumor vaccine

Fibrosarcoma is a locally aggressive malignant tumor with a high recurrence rate, so that wide excisional surgery is necessary for treatment. However, it is often difficult to resect with a sufficient margin of excision at the site of tumor infiltration. Recombinant tumor vaccine therapy is a useful method to induce specific immunity. In this study, we have shown its utility as a candidate for therapy by applying a recombinant Newcastle disease virus (rNDV) tumor vaccine (rNDV-TV). Although the therapeutic effect of similar viruses has been examined in several tumors, the vaccination efficacy against fibrosarcoma has not been demonstrated until now. In this study, we showed the induction of an antitumor response by rNDV-TV against murine fibrosarcoma and investigated the role of lymphocytes in tumor elimination. Intraperitoneal inoculation of murine fibrosarcoma (WEHI164) cells showed increased lethality in C.B.17scid/scid (scid) mice within 2 weeks of inoculation. The survival rate increased to 80% when the mice were transfused with CD3⁺ cells from BALB/c mice previously immunized with rNDV-TV. However, all mice died from tumor growth after inoculation with non-immunized CD3⁺ cells. Although the survival rate was around 50% in mice receiving only immunized CD4⁺ and CD8⁺ cells, the survival rate was not decreased in mice receiving CD3⁺CD4⁻CD8⁻ (natural killer T; NKT) cells together with immunized CD4⁺ and CD8⁺ cells. This study showed rNDV-TV induced an antitumor T cell response to WEHI164 cells, and major subsets of cells involved in tumor exclusion were CD4⁺ and CD8⁺ cells, together with NKT cells.