Calreticulin as an Adjuvant In Vivo to Promote Dendritic Cell Maturation and Enhance Antigen-Specific T Lymphocyte Responses against Melanoma

Abstract

An endoplasmic reticulum resident protein, calreticulin (CRT), participates in many cellular processes. CRT is a tumor-associated antigen with an important role in antitumor immunity. Previously, we reported that the recombinant CRT fragment 39-272 (CRT/39-272) exhibited superior immunobiological activity, activating macrophages to release cytokines and promoting dendritic cell (DC) maturation. However, the effect of CRT/39-272 in vivo, especially its adjuvant effect on in vivo antitumor immune responses, was not fully investigated. In this study, we constructed a fusion protein linking CRT/39-272 to an ovalbumin (OVA) peptide (residues 182–297, OVAp) and used the fusion protein (OVAp-CRT) to examine the adjuvant effect of CRT. We investigated whether CRT/39-272 could induce bone marrow-derived DC maturation and strongly promote the proliferation of OVA-specific T cells in vitro. Compared with OVAp, OVAp-CRT induced stronger antigen-specific T lymphocyte responses, including antigen-specific T cell proliferation, interferon-γ secretion, and cytotoxic T lymphocyte responses. OVAp-CRT-immunized mice generated significantly increased OVAp-specific antibody and CD4+/CD8+ memory T cells, which mediated long-term protective effects. OVAp-CRT upregulated CD40, CD80, and CD86 expressions in splenic conventional DCs. Furthermore, OVAp-CRT protected immunized mice against OVA-expressing B16 melanoma cells in vivo. Moreover, mice that were adoptively transferred with OVAp-CRT-pulsed DCs showed inhibited tumor growth and prolonged mouse survival. Our results demonstrate that CRT/39-272 can be used as a potential new adjuvant for tumor vaccines, and this finding may be useful in tumor vaccine development.

Biomimetic Dual-Target Theranostic Nanovaccine Enables Magnetic Resonance Imaging and Chemo/Chemodynamic/Immune Therapy of Glioma

“…To verify the feasibility of NGs in inducing ICD of cancer cells, representative damage-associated molecular patterns released in cancer cells after different treatments were assayed, including high mobility group box 1 (HMGB-1) release, adenosine triphosphate (ATP) secretion, and calreticulin (CRT) exposure. When CRT is translocated from the endoplasmic reticulum to the cancer cell surface, it can stimulate the maturation of DCs, enhance their recognition and phagocytosis of antigens from the apoptotic cancer cells, and present the relevant antigens to T cells . The exposure of CRT in cancer cells after treatment with different materials was observed by CLSM (Figures B and S13).…”

Overcoming Resistance to Immune Checkpoint Inhibitor Therapy Using Calreticulin-Inducing Nanoparticle

“…Calreticulin (CRT) is an endoplasmic-reticulum-resident chaperone that functions as a DAMP and plays a crucial role in tumor antigen recognition [ 32 , 33 , 34 ]. The ICD-induced expression of CRT on cancer surfaces can attract phagocytes, such as DCs and macrophages, which enhances antigen presentation [ 35 , 36 , 37 ].…”