Figure 6. Protection from EBNA1-induced B cell lymphoma challenge by heterologous vaccination.

(A) huDEC205-Tg mice were immunized with different combinations of vaccines for the prime and the boost, scheduled 10 days apart. Mice were challenged with 3 × 10⁶ to 5 × 10⁶ EBNA1⁺ B cell tumor cells (BL-E1) i.v. 14 days after the boost in a preventive setting. Mice were monitored every second day, including measurement of weight, observation of general behavior, and assessment using the mouse grimace scale. (B) At sacrifice, bulk single-cell suspensions of cells from LNs, spleen, liver, and blood were harvested and analyzed by EBNA1 qPCR. Abundance of the EBNA1 gene was normalized to the UBC gene as the tumor load. Data are shown as the mean ± SD from 2 independent experiments with at least 5 mice per group. (C) A tumor load cutoff of 0.005 or higher was set, and results of all analyzed organs from each mouse were pooled. The percentage of mice per condition without tumor burden and with tumor burden in 1 to 4 organs is depicted. *P < 0.05; Mantel-Cox test. (D) At sacrifice, splenic tissue from treated mice with EBNA1-induced B cell lymphoma were fixed in PFA and embedded in paraffin. Splenic tissues from PBS-treated mice without tumor treatment were used. Splenic tissue samples were stained with H&E, αCD19, αPCNA, and αXIAP Abs. One representative staining for each group is shown. Scale bar: 20 μm.