Enhanced efficacy and reduced toxicity of multifactorial adjuvants compared with unitary adjuvants as cancer vaccines

Abstract

Identification of Toll-like receptors (TLRs)and their ligands, and tumor necrosis factor-tumor necrosis factor receptor (TNF-TNFR) pairs have provided the first logical, hypothesis-based strategies to molecularly concoct adjuvants to elicit potent cell-mediated immunity via activation of innate and adaptive immunity. However, isolated activation of one immune pathway in the absence of others can be toxic, ineffective, and detrimental to long-term, protective immunity. Effective engineered vaccines must include agents that trigger multiple immunologic pathways. Here, we report that combinatorial use of CD40 and TLR agonists as a cancer vaccine, compared with monotherapy, elicits high frequencies of selfreactive CD8 ؉ T cells, potent tumorspecific CD8 ؉ memory, CD8 ؉ T cells that efficiently infiltrate the tumor-burdened target organ; therapeutic efficacy; heightened ratios of CD8 ؉ T cells to FoxP3 ؉ cells at the tumor site; and reduced hepatotoxicity. These findings provide intelligent strategies for the formulation of multifactorial vaccines to achieve maximal efficacy in cancer vaccine trials in hu IntroductionThe molecular identification of Toll-like receptors (TLRs) and their ligands, as well as tumor necrosis factor (TNF)-tumor necrosis factor receptor (TNFR) pairs that control adaptive immunity, has provided the first logical, hypothesis-based strategies to molecularly concoct adjuvants that elicit potent cell-mediated immunity. Paralleling TLRs in mobilizing the innate immune response, CD40 and its ligand represent the primary ligand-receptor pair essential for development of the adaptive immune response. Individually, TLR agonists 1 and CD40 agonists 2-4 have entered clinical trials as adjuvants for eliciting protective immune responses to cancer. Inherent in these monotherapeutic approaches are limited induction of immunity, lack of clinical efficacy and, in some cases, hepatotoxicity. 3,4 TLRs are widely expressed on both hematopoietic and nonhematopoietic cells and elicit proinflammatory responses upon receptor engagement. Indeed, use of TLR agonists as solitary adjuvants triggers dendritic cell (DC) maturation, leukocyte migration, and release of chemokines and cytokines, and enhances immunity. 5,6 Studies in which TLR agonists have been scrutinized for their ability to induce cross-presentation and antigen-specific CD8 ϩ responses in vivo 7 show some level of activity that is minimal compared with that observed when combined with a CD40 agonist. 8,9 TLR agonists as unitary adjuvants in murine tumor models have demonstrated marginal efficacy, as reviewed, 10 but have proven effective when combined with other vaccine modalities. [11][12][13] Finally, clinical use of a TLR9 agonist in lung cancer trials has been recently suspended due to lack of clinical response. 1Studies from animal models underscore the utility of anti-CD40 (␣CD40) as a unitary adjuvant. 14,15 We previously demonstrated that the magnitude of immune responses elicited by TLR or CD40 agonists alone is minimal compared with the magnit...

Ig-Like Transcript 3 Regulates Expression of Proinflammatory Cytokines and Migration of Activated T Cells

“…Attempts to use DC-based vaccines to mount a strong Ag-specific immune response against tumorassociated Ags or pathogenic agents, which elude the human immune system, rely on the use of adjuvants. Various TLR ligands have been used with some success as adjuvants in DCbased vaccines against tumor-associated Ags (35)(36)(37)(38). The present findings offer the tantalizing possibility that knockdown of ILT3 could be used as an adjuvant itself to improve the effectiveness of DC based vaccines to generate immunogenic responses against tumor Ags or chronic pathogenic infections.…”

Local Activation of CD8 T Cells and Systemic Tumor Eradication without Toxicity via Slow Release and Local Delivery of Agonistic CD40 Antibody

“…Some studies that describe the use of anti-CD40 Ab as an immunotherapy against tumors conclude that monotherapy is not sufficient for tumor eradication but this treatment has to be combined with cytokines, TLR ligand signaling, or chemotherapy (13)(14)(15)39). We agree that anti-CD40 Ab monotherapy, as described in this study, is not always capable of tumor eradication and that the use of combinatorial treatments will be beneficial, and propose that our superior administration method (i.e., delivery of a low-dose agonistic CD40 Ab in a slow-release formulation in the tumor-draining area) is also valuable when combining anti-CD40 Ab treatment with other agents.…”

PKCθ is required for alloreactivity and GVHD but not for immune responses toward leukemia and infection in mice

“…Next, we determined the effect of microbial/inflammatory agents on PKCθ -/-2C T cell expansion. Recent studies indicate that a combination of TLR ligands and agonistic anti-CD40 Abs (FGK45) provide an exceptionally strong signal for T cell proliferation (40)(41)(42). Furthermore, studies have shown that TLR ligands can exacerbate GVHD (43).…”