Protection from intravenous tumor challenge after vaccination with SINCP or Adeno. Groups of mice were vaccinated three times at 2-week intervals with SINCP-neu (a plasmid containing Sindbis virus genes and the gene for rat HER2/neu) or SINCP-βgal. (a) or once with Adeno-neu (an E1,E2a-deleted adenovirus also containing the gene for rat HER2/neu) or Adeno-empty (adenovirus lacking an inserted gene) (b). Two weeks after the final vaccination with SINCP or 6 weeks after vaccination with Adeno, the mice were challenged with A2L2 cells injected into the tail vein. Twenty-one days after the challenge in SINCP-vaccinated animals or 35 days after the challenge in Adeno-vaccinated animals, the mice were killed and the number of tumor nodules on the surfaces of the lungs was counted. Each symbol represents one mouse. Horizontal bars indicate means.