Abstract 2407: Establishment of a clinically applicable human tyrosine hydroxylase DNA vaccine for anti-neuroblastoma immunotherapy

Abstract

Listen

Translate article

Abstract Background: Neuroblastoma (NB) is an aggressive neoplasm of the sympathetic nervous system in early childhood. Current treatment of high-risk NB consists of intensive myeloablative therapy followed by bone marrow transplantation. However, children with advanced stage disease or those with refractory disease have a poor prognosis. A promising adjuvant approach could be active immunotherapy with DNA vaccines encoding tumor-associated antigens, like tyrosine hydroxylase (TH), which is highly expressed on NB cells. We already established human TH (hTH) DNA vaccination in a syngeneic NB mouse model achieving complete remission of established mass disease and of metastasis. With regard to a clinical application important aspects of this xenogeneic TH DNA vaccination approach have to be readjusted for the use in humans. Methods: For this purpose, hTHcDNA fused to mutated ubiquitin (Gly76[[Unsupported Character - [[Unsupported Character - ]]]]Ala76) was cloned into the FDA-approved, kanamycin encoding DNA plasmid pING. To examine the functionality of the new plasmid design, pING-hTH was transfected into HEK293 cells. Gene expression was verified by immunofluorescence and western-blot analysis. Furthermore, efficacy of the vaccine was tested in a syngeneic NB mouse model in a prophylactic setting employing attenuated Salmonella typhimurium SL7207 as DNA delivery system. Primary tumors were induced by s.c. injection of NXS2 NB cells and tumor growth was monitored over time. Furthermore, immunological mechanisms of tumor protection were evaluated. Results: In vitro, functional hTH protein expression by the new plasmid design could be established in HEK293 cells. In vivo, xenogeneic TH DNA vaccination induced an anti-NB effect in mice receiving pING-hTH as indicated by a 48-52% reduction in s.c. tumor volume in contrast to empty vector controls. Immunization with hTH-pING DNA-vaccine further generated CTL-mediated responses against NXS2 NB cells and an increase in IFN-γ production. Furthermore, CD8+ T-cells presented at higher levels at primary tumor sites in hTH-vaccinated mice compared to controls. Conclusion: The new vaccine design (hTH-pING) effectively induced an anti-NB immune response in vivo indicated by the suppression of s.c. primary tumors, which is mediated by NB-specific CTLs. Our findings open the possibility for developing a clinically applicable vaccination strategy for one of the most challenging childhood tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2407.