Coupling of antigen to cholera toxin for dendritic cell vaccination promotes the induction of MHC class I‐restricted cytotoxic T cells and the rejection of a cognate antigen‐expressing model tumor

Abstract

We previously demonstrated that cholera toxin (CT) is highly efficient as a combined carrier and adjuvant for dendritic cell (DC) vaccination, inducing strong Th1-dominated B cell and CD4 + T cell responses. In this study we show that vaccination with DC pre-pulsed ex vivo with CT-conjugated OVA (OVA-CT) gives rise to OVA-specific CD8 + T cells that produce IFN-+ and are cytotoxic for OVA-expressing E.G7 tumor cells both in vitro and in vivo. The induction of specific CD8 + CTL by OVA-CT-treated DC was associated with enhanced presentation of OVA peptide (SIINFEKL) on MHC class I in combination with an overall activation of the pulsed DC. Vaccination of mice with OVA-CT-pulsed DC resulted in rejection of already established MHC class I-positive, MHC class II-negative, OVA-expressing E.G7 tumors in an antigen-specific, CD8 + T cell-dependent fashion and was associated with high numbers of tumor-infiltrating CD8 + T cells. Conjugation of antigen to CT facilitated DC uptake of the linked antigen through the GM1 receptor-binding B subunit and induced strong activationmaturation signals through the biologically active A subunit. These results have interesting implications for DC vaccination aimed at inducing CTL immune responses.

The Shiga toxin B‐subunit targets antigen in vivo to dendritic cells and elicits anti‐tumor immunity

“…Furthermore, we showed that DC are required for efficient priming of specific CD8 + T cells after STxB-OVA administration. Harnessing of DC in vivo seems to be a prerequisite for inducing immunity, as other carrier proteins have been shown to efficiently channel exogenous antigen into the MHC class I pathway of many cells without priming CTL in mice, likely because they do not specifically target DC in vivo [34][35][36]. The glycolipid receptor of STxB, Gb 3 , may be expressed by cells other than DC such as some epithelial and B cells [22,26,27].…”

Cholera-Toxin Suppresses Carcinogenesis in a Mouse Model of Inflammation-Driven Sporadic Colon Cancer

“…CD8+ cytotoxic lymphocytes with increased potency to recognize and kill cancer cells have been demonstrated to occur with the use of CT in a dendritic cell vaccination-based anti-neoplastic therapy of tumor transplanted mice (46). Further research is also needed to assess the role of resident gut microbiota in the anti-neoplastic effect of CT. For example, Verdù et al have shown that CT administration was able to ameliorate DSS-induced colitis in mice only when co-administered with anaerobic bacteria.…”

Suppression of an Already Established Tumor Growing through Activated Mucosal CTLs Induced by Oral Administration of Tumor Antigen with Cholera Toxin

“…Although both CT-conjugated-OVA and CTB-conjugated OVA are cross-presented by MHC class I in DCs, only CT-OVA but not CTB-OVA cross-primes OVA-specific CD8 ϩ CTLs in vivo (23,34). Additionally, DCs pulsed with intact OVA alone cannot crosspresent and cross-prime CTLs (23).…”

“…Additionally, DCs pulsed with intact OVA alone cannot crosspresent and cross-prime CTLs (23). For the cross-priming of Agspecific CTLs by Ag-captured immature DCs, maturation signaling via some surface molecules such as TLR-3 in those DCs is essential (35,36).…”

“…ϩ T cells (23), indicating that the elimination of previously established tumor cells might require the infiltration of tumor-specific activated CD8…”