Figure 5: Protective and antigen-specific immunity to melanoma B16 cells expressing OVA. C57BL/6J mice were immunized once with either the parental WSN virus or the recombinant WSN-OVAI/II virus. Three weeks after immunization, mice were challenged i.v. with B16-OVA cells or with PBS. The number of pulmonary metastases (a) and the frequency of SIINFEKL-specific IFN-γ-producing T cells, as measured by using the ELISPOT assay on spleen-derived lymphocytes (b) was determined 12 days after the tumor cell inoculation. All of the experiments included 8 mice per group and were repeated three times with similar results. and , comparing WSN-OVAI/II-versus WSN-infected and naïve mice.