Anti-HER2 CD4 T helper type 1 response in breast cancer: Is there a role for immunorestoration?

636 Background: Tumor microenvironment infiltration of IFNγ-producing CD4 T helper 1 (Th1) cells is linked to improved prognosis in invasive breast cancer (IBC). We investigated circulating anti-HER2 CD4 Th1 response (Th1resp) involved in breast tumorigenesis, and compared Th1resp prior to after chemotherapy/trastuzumab (C/T) treatment or dendritic cell vaccination in HER2+ IBC pts. Methods: Th1resp were compared in healthy donors (HD; n=21) and pts with benign breast biopsy (BD; n=9), HER2neg IBC (n=11), HER2+ DCIS (n=31), and HER2+ IBC (n=14). Th1resp of pts enrolled in neoadjuvant immunization trials for HER2+ DCIS and found to have Stage I IBC at surgery (n=11) were analyzed pre/postimmunization, and compared with HER2+ IBC pts after C/T (n=34). Th1resp were generated from PBMC pulsed with 6 HER2 MHC class II peptides, by measuring IFNγ via ELISPOT. Th1resp metrics were (1) anti-HER2 response rate, (2) # of reactive peptides (repertoire), (3) cumulative response across 6 peptides (SFC/106 cells). Cont...