Fig. 3.

Vaccine design and efficacy of a MYCN-DNA vaccination. a The sequences of MYCNHigh and MYCNLow minigene epitopes identified by syfpeithi and their respective scores are shown. Epitopes were separated by an AAY spacer sequence, which represents a preferential proteasomal cleavage site (left panel). An HA tag was included to allow detection. Schematic of the expression vector pCMV-F3Ub with the BglII restriction site for insertion of minigenes (right panel). b Primary tumor growth of wt-NXS2 cells (n = 6, left panel) or NXS2-MYCN (n = 9, right panel) was analyzed after DNA vaccination with attenuated Salmonella typhimurium SL7207 as described in materials and methods. Results are presented as mean tumor volume in mm³ ± SE. The MYCNHigh-vaccinated group: black triangles, MYCN-cDNA: dark gray circles, MYCNLow: light gray diamonds. Differences in the NXS2-MYCN model growth were statistically significant (*p = 0.0019) in contrast to the wt-NXS2 tumor model (p = 0.0887). c Individual tumor growth in the NXS2-MYCN model immunized with MYCNLow (left panel) and MYCNHigh (right panel). One mouse died in the MYCNLow experimental group during vaccination. The time period between tumor challenge and tumor removal (size > 800 mm³/necrosis) was significantly extended in MYCNHigh-vaccinated mice (median 21 days) compared to MYCNLow-vaccinated mice (median 16 days) (*p < 0.05)