Immune Response in Patients Who Have Undergone Vaccine Therapy for Stage III or Stage IV Breast Cancer That Overexpresses HER2

OBJECTIVES: Primary * Determine whether immunologic memory to the HER-2/neu (HER2) intracellular domain (ICD) protein has been generated by active immunization with a HER2 ICD plasmid-based vaccine by assessing the delayed-type hypersensitivity response to HER2 ICD peptides 6 months after vaccination in patients with HER2-overexpressing stage III or IV breast cancer. Secondary * Characterize the memory T-cell population and quantitate memory precursor frequency at 3, 6, and 12 months after active immunization using intracellular cytokine staining. OUTLINE: This is an open-label study. Patients receive HER2 intracellular domain (ICD) protein mixture intradermally and sterile water injected intradermally (as a negative control) at 6 months post-vaccination with pNGVL3-hICD vaccine. Vital signs and injection site will be monitored prior to skin test and at 60 minutes post-test. Patients return 48-72 hours after skin test for delayed-type hypersensitivity (DTH) measurements. The injection site is biopsied and examined by immunohistochemistry for infiltrating T-cell and antigen-presenting cell populations. Blood is drawn at 3, 6, and 12 months post-vaccination for assessment of immune memory response. Blood draws are coordinated with parent study. Blood samples are examined by flow cytometry for the presence of memory markers including L-selectin, CD45 isoforms, cytokines, and CCR7. PROJECTED ACCRUAL: A total of 56 patients will be accrued for this study.