Therapy-induced antitumor vaccination in neuroblastomas by the combined targeting of IL-2 and TNF alpha

L19-IL2 and L19TNF are fusion proteins composed of L19(scFv), specific for the angiogenesis-associated ED-B containing fibronectin isoform and IL-2 or TNF. Because of the tumor targeting properties of L19, IL-2 and TNF concentrate at therapeutic doses at the tumor vascular level. To evaluate the therapeutic effects of L19-IL2 and L19mTNF in neuroblastoma (NB)-bearing mice, A/J mice bearing Neuro2A or NIE115 NB were systemically treated with L19-IL2 and L19mTNF, alone or in combination protocols. Seventy percent of Neuro2A- and 30% of NIE115-bearing mice were cured by the combined treatment with L19-IL2 and L19mTNF, and further rejected a homologous tumor challenge, indicating specific antitumor immune memory. The immunological bases of tumor cure and rejection were studied. A highly efficient priming of CD4+ T helper cells and CD8+ CTL effectors was generated, paralleled by massive infiltration in the tumor tissue of CD4+ and CD8+ T cells at day 16 after tumor cell implantation, when, after therapy, tumor volume was drastically reduced and tumor necrosis reached about 80%. The curative treatment resulted in a long-lasting antitumor immune memory, accompanied by a mixed Th1/Th2 type of response. Concluding, L19-IL2 and L19mTNF efficiently cooperate in determining a high percentage of NB cure that, in our experimental models, is strongly associated to the generation of adaptive immunity involving CD4+ and CD8+ T cells.