Delayed-type hypersensitivity response is a predictor of peripheral blood T-cell immunity after HER-2/neu peptide immunization

Many groups that immunize cancer patients with cancer vaccines use the gene ration of a delayed-type hypersensitivity (DTH) response as the primary mea sure of the ability to immunize a patient to a tumor cell or specific tumor antigen. This study examines whether the development of a tumor antigen sp ecific DTH response, measured after vaccination with peptide-based vaccines , correlates to in vitro assessment of peripheral blood antigen-specific T- cell responses. The HER-2/neu protein was used as a model tumor antigen. Th irty-two patients who completed a course of immunization with HER-2/neu pep tide-based vaccines were analyzed. HER-2/neu peptide specific DTH responses (n = 93) and peripheral blood T-cell responses (n = 93) were measured 30 d ays after the final immunization. Size of DTH induration was correlated wit h HER-2/neu-specific T-cell proliferative responses assessed from periphera l blood lymphocytes isolated concurrently with peptide skin test placement. HER-2/neu peptide-specific DTH responses greater than or equal to 10 mm(2) correlated significantly to a measurable peptide-specific peripheral blood T-cell response defined as stimulation index >2.0 (P = 0.0006). However, a ntigen-specific DTH responses with magnitudes between 5 and 9 mm(2) were no t significantly associated with the development of systemic immunity. DTH r esponses between 5 and 9 mm(2) carried an odds ratio of 1.3 (P = 0.61) in p redicting a measurable systemic tumor antigen response. The findings presen ted here demonstrate that tumor antigen-specific DTH responses greater than or equal to 10 mm(2) correlate with measurable in vitro antigen-specific l ymphocytic proliferation and are, in this model system, a reflection of sys temic immunization.