Introduction: Vaccination with proteins mimicking ganglioside GD2 is a promising strategy to induce an active anti-tumor immune response against neuroblastoma (NB). We previously showed in vivo efficacy of a murine anti-idiotype antibody (anti-Id Ab) ganglidiomab acting as a GD2 surrogate. To reduce murine origin for human studies, we generated a human/mouse chimeric anti-Id Ab ganglidiximab by replacing murine with corresponding human constant regions and report here its GD2-mimicking properties.
Methods and Results: DNA sequences encoding for variable regions of ganglidiomab heavy and light chain were synthesized by RT-PCR using RNA of ganglidiomab-producing hybridoma cells and inserted into mammalian expression vectors encoding for human IgG1 heavy and light chain constant region, respectively. Next, CHO cells were stably co-transfected with both vectors to establish a cell line permanently producing ganglidiximab. After purification from cell culture supernatants, binding of ganglidiximab to anti-GD2 Abs of the 14.18 family (14G2a, ch14.18, ch14.18-dCH2, ch14.18-IL-2, hu14.18 and hu14.18-IL-2) was shown by ELISA and binding affinities were determined using Biacore technique. Importantly, GD2-specific NB cell lysis mediated by ch14.18 as well as binding of anti-GD2 Abs to the nominal antigen GD2 was competitively inhibited by ganglidiximab confirming its anti-idiotypic function. Finally, vaccination of mice with ganglidiximab resulted in induction of GD2-specific Abs.
Conclusion: We generated and characterized a new chimeric human/mouse anti-Id Ab for active immunotherapy against NB and demonstrated induction of a GD2-specific humoral immunity in mice providing a baseline for protein vaccine development.