UC San Diego

Vaccine-based immunotherapy holds promise as an effective treatment of metastatic malignancies with potential for long-term remission. The goal is to elicit Th1-type immune responses that utilize cytotoxic T lymphocytes to generate a protective antitumor response. Aluminum salts (alum), which generate predominantly Th2-type immune responses, are the sole adjuvants approved for use in the majority of countries worldwide. Thus, for significant advancement of cancer immunotherapy, there is a great need for the development of new immunostimulatory adjuvants that will induce Th1-type immune responses. This dissertation documents the research and development of several peptides that act as Th1-type adjuvants. These peptides are derived from, or based upon, an endogenous immunostimulatory protein, HMGB1. Most focus is placed on one particular peptide, named Hp91. The dissertation starts with an evaluation of the Th1 adjuvant properties of Hp91, and is followed by a study of the characteristics and mechanism of action. The remainder of the dissertation focuses on the research to find, as well as engineer, more potent adjuvant derivates based upon Hp91. Examples include shortened and mutated derivates, peptide dimers, and encapsulation within nanoparticles. A summary of the findings are presented here. The dissertation author shows that Hp91 potentiates in vivo cellular immune responses to peptide and protein antigen. Hp91 promotes the in vivo production of the Th1 cytokines, as well as antigen- specific activation of CD8+ CTLs. Hp91-induced secretion of IL-6 is MyD88- and TLR4-dependent, is mediated through p38 MAPK and NF[kappa]B, and signaling is dependent on clathrin- and dynamin-mediated endocytosis of Hp91. Additionally, Hp91 activates the MyD88-independent signaling pathway. The author demonstrates that the C- terminal domain of Hp91, named UC1018, is responsible for the adjuvant activity. UC1018 generates significant antitumor responses when used as adjuvant in a prophylactic cancer vaccine. Additionally, several Hp91 mutants showed enhanced immunostimulatory activity. The findings presented in this dissertation are significant because they identify and characterize novel, Th1-type synthetic peptide adjuvants that may allow development of new prophylactic and potentially therapeutic treatments of cancer. The results warrant continued development of these peptide adjuvants and may serve as a guide for the future engineering of synthetic Th1-type peptide adjuvants