Browsing by Subject "Cancer vaccine"

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    Combination of STING and TLR 7/8 agonists as vaccine adjuvants for cancer immunotherapy
    (2021-01) Shah, Manan Chandraj
    Cancer vaccines have evolved as a new treatment modality to eradicate cancer and has gained in popularity since the approval of Provenge® vaccine. By activating antigen-presenting cells (APCs), which, in turn, activate innate or adaptive immune responses, immunoadjuvants have become promising tools for cancer immunotherapy. Different types of immunoadjuvants such as toll-like receptor (TLR) agonists, exosomes, and metallic immunoadjuvants have been studied for their immunological effects. However, the clinical use of immunoadjuvants is limited by transient responses and various side-effects. Therefore, there is a need for exploring novel adjuvant technologies such as adjuvant combinations to achieve effective immune responses.In this study, we investigated the use of a multi-adjuvant approach by combining two different classes of adjuvants, STING and TLR 7/8 agonists because of their distinct immune cell targets, signaling pathways, and significant roles in the activation and maintenance of immune responses. STING and TLRs are pattern recognition receptors that act as sensors for “danger signals” and aid in identification and elimination of foreign bodies. Activation of these receptors induces an immune cascade, leading to secretion of numerous cytokines, chemokines and phenotypical changes in an immune cell. Owing to their potent immunological effects, clinical and preclinical studies have demonstrated great potential of STING and TLR agonists as cancer vaccine adjuvants. We evaluated the potential of combining 522, a TLR 7/8 agonist, and DMXAA, a STING agonist, to stimulate an immune response in APCs. Using flow cytometry and ELISA, we investigated the costimulatory molecule expression and cytokine secretion in dendritic cells, and M2 to M1 polarization after treatment with the agonists, individually or in combination. Also, PLGA nanoparticles were formulated and characterized in vitro. We observed that the combined treatment showed enhanced DC activation and M2 repolarization compared to the individual agonists. However, we also observed an increased induction of IL-10, an immunosuppressive cytokine. Small molecules display poor pharmacokinetic profiles in vivo, therefore, we fabricated nanoparticles to improve their in vivo disposition. PLGA NPs displayed similar DC activation to free drugs and hence will be used for further in vivo studies.
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    TLR7/8 Agonist Encapsulating Polymeric Nanoparticles for Cancer Immunotherapy
    (2018-10) Kim, Hyunjoon
    The immune system is important for the prevention of cancer and formed the basis of cancer immunotherapy. That is, enhancement of the immune response for the treatment of malignant cancer cells. The field has undergone significant progress to include the use of checkpoint inhibitors, monoclonal antibodies and cytokine therapies. In addition, a cancer vaccine, composed of tumor associated antigens (TAAs) and vaccine adjuvant, is particularly promising. Effective vaccines can mobilize tumor-specific CD8 T cells to kill selectively tumor cells with cytotoxic granules and secrete IFN-ɣ that sensitize tumors to be susceptible to effector immune cells. Additionally, activated CD8 T cells become memory cells and can respond to same TAA-epitopes, which can be effective for long-term protective immunity to inhibit cancer recurrence. Activation of dendritic cells (DCs), which are the main antigen-presenting cells (APCs), is critical for T cell immunity. To an elicit tumor-specific CD8 T cell response, DCs have to process and present TAAs to CD8 T cells through the major histocompatibility complex (MHC) I. Moreover, co-stimulatory signals and pro-inflammatory cytokines are required to stimulate CD 8 T cells. However, CD8 T cell anergy and exhaustion will occur if TAA treatment is not sufficiently immunogenic to trigger DC activation. Therefore, development of immunostimulatory adjuvant that can trigger DC activation can enhance therapeutic efficacy of cancer vaccines. Imidazoquinoline-structured synthetic toll-like receptor (TLR) 7/8 agonists are strong cytokine inducers that can be a potent vaccine adjuvant. TLR7/8 ligation can activate MyD88 signaling pathways and stimulate DCs to upregulate co-stimulatory molecules and secrete pro-inflammatory cytokines and type I interferons. However, TLR7/8 agonists lack prominent efficacy in vivo due to the rapid clearance from the injection site. Following subcutaneous (SC) injection, small molecules enter the systemic circulation via blood capillaries and only small portion can reach the draining lymph nodes. Therefore, our goal was to develop a SC injectable drug carrier that can more efficiently deliver as well as prolong duration of at the site of action of TLR7/8 agonists. In this study, we fabricated poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) containing TLR7/8 agonists. Nanoparticulate delivery of TLR7/8 agonist showed enhanced DC activation and antigen-presentation compared to the soluble form of TLR7/8 agonists. When combined with peptide/tumor cell lysate-based antigens, NPs potentiated the antigen-specific CD8 T cell expansion and increased cytotoxic functions, which resulted in enhanced efficacy in both prophylactic and therapeutic tumor models. To further enhance endo/lysosomal delivery of TLR7/8 agonists in PLGA NPs, we included a sodium bicarbonate-mediated gas-generating system that is acidic pH-responsive. This approach resulted in 33-fold greater amount of TLR7/8 agonists encapsulated within the NPs. More importantly, the PLGA NP immunization elicited a stronger CD8 T cell response compared to conventional PLGA NPs, which in turn, enhanced therapeutic efficacy. As tumor microenvironment is immune suppressive, we examined whether modulation of tumor microenvironment can enhance the therapeutic efficacy of cancer vaccine. We reduced the immune suppressive cells including myeloid-derived suppressive cells (MDSCs) and regulatory T cells (Tregs) by daily oral dosing of a tyrosine kinase inhibitor (TKI), sunitinib. Additionally, we adapted an anti-PD-L1 antibody to block programmed death ligand 1 (PD-L1) expressed on tumor-associated (M2) macrophages and MDSCs that exhaust CD8 T cells, to augment the CD8 T cell activation at the tumor. In our study, combination of sunitinib and PD-L1 blockade significantly decreased the immune suppressive cell population and reduced PD-L1 expression on these cells. We also examined if nanoparticulate delivery of TLR7/8 agonist can potentiate NK cell-mediated cancer immunotherapy through its known effect on TH1 immunity. Antibody-dependent cellular cytotoxicity (ADCC) of monoclonal antibodies was found to be augmented in response to TLR7/8 agonist encapsulating NPs as a vaccine adjuvant. Overall, our studies demonstrate that PLGA NPs broaden the application of TLR7/8 agonists for improved cancer treatment. Moreover, this platform holds promise to enhance the efficacy of cancer vaccines composed of tumor associated antigens (TAAs) and vaccine adjuvant