Vaccination of metastatic melanoma patients with autologous HSPPC-96 is feasible and devoid of significant toxicity. This vaccine induced clinical and tumor-specific T-cell responses in a significant minority of patients.

Given the important role of adjuvants in prophylactic vaccines, identification and development of new adjuvants with enhanced efficacy and safety is necessary. The use of adjuvants with immunopotentiating properties that can direct the immune responses to humoral or cell-mediated immunity and can induce T-cell responses has made it possible to design more protective vaccines. Although current regulations focus on traditional adjuvants, notably aluminum and calcium salts, advances have been made in regulatory considerations. The regulatory agencies for the evaluation of medicinal products are actively drafting guidance on requirements for the evaluation of new adjuvants. This article briefly summarizes the most widely studied adjuvants in vaccination, including those licensed for human vaccines and the regulatory aspects relevant to adjuvant quality at development stages.

Heat shock proteins (hsp) 96 play an essential role in protein metabolism and exert stimulatory activities on innate and adaptive immunity. Vaccination with tumor-derived hsp96 induces CD8+ T cell-mediated tumor regressions in different animal models. In this study, we show that hsp96 purified from human melanoma or colon carcinoma activate tumor- and Ag-specific T cells in vitro and expand them in vivo. HLA-A*0201-restricted CD8+ T cells recognizing Ags expressed in human melanoma (melanoma Ag recognized by T cell-1 (MART-1)/melanoma Ag A (Melan-A)) or colon carcinoma (carcinoembryonic Ag (CEA)/epithelial cell adhesion molecule (EpCAM)) were triggered to release IFN-γ and to mediate cytotoxic activity by HLA-A*0201-matched APCs pulsed with hsp96 purified from tumor cells expressing the relevant Ag. Such activation occurred in class I HLA-restricted fashion and appeared to be significantly higher than that achieved by direct peptide loading. Immunization with autologous tumor-derived hsp96 induced a significant increase in the recognition of MART-1/Melan-A27–35 in three of five HLA-A*0201 melanoma patients, and of CEA571–579 and EpCAM263–271 in two of five HLA-A*0201 colon carcinoma patients, respectively, as detected by ELISPOT and HLA/tetramer staining. These increments in Ag-specific T cell responses were associated with a favorable disease course after hsp96 vaccination. Altogether, these data provide evidence that hsp96 derived from human tumors can present antigenic peptides to CD8+ T cells and activate them both in vitro and in vivo, thus representing an important tool for vaccination in cancer patients.