The B subunit of Shiga toxin coupled to full-size antigenic protein elicits humoral and cell-mediated immune responses associated with a Th1-dominant polarization

Abstract

A number of studies in animal models and humans have shown that both humoral andcell-mediated immune responses play an important role in the control of viral infection and tumor development. In most cases, vaccination with non-vectorized peptides or proteins induces low antibody responses and fails to elicit specific cytotoxic T lymphocytes (CTL). In order to make vaccination more efficient, we chemically coupled the non-toxic B subunit of Shiga toxin (STxB) to a full-size antigenic model protein, ovalbumin (OVA), yielding STxB-OVA. We found that STxB-OVA delivers OVA-derived peptides into both the MHC class I- and II-restricted presentation pathways in mouse dendritic cells. Accordingly, the study of STxB trafficking in these cells revealed that, after internalization, a fraction of STxB followed the retrograde transport pathway to the endoplasmic reticulum, while another fraction was targeted to late endosomes/lysosomes. Vaccination of mice with STxB-OVA primed a specific anti-OVA CTL response without the use of adjuvants. Splenocytes and, particularly, CD4(+) T cells from mice immunized with STxB-OVA also produced higher amounts of the T(h)1 cytokine IFN-gamma and IgG2a-type antibodies than mice immunized with non-vectorized ovalbumin. In conclusion, this study identifies a unique non-live vaccine delivery system for polyepitopic antigens that elicits antigen-specific CTL, a humoral immune response and a T(h)1-type polarization without the use of adjuvant.

Membrane cytosolic translocation of verotoxin A1 subunit in target cells

“…Both VT1 holotoxin and VTB can deliver antigens for MHC presentation, but how each targets antigens to the cytosol for presentation is unknown (Haicheur et al, 2003;Noakes et al, 1999;Vingert et al, 2006). Our results favour a retrograde ER translocation pathway in verotoxin-sensitive cells but a less efficient endosomal pathway for verotoxin-insensitive antigen presentation remains possible (Falguieres et al, 2001).…”

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

“…However, successful targeting of antigen to DC has also been associated with antibody induction [67], which may explain previous results regarding the ability of STxB-OVA to increase the amount of OVA-specific IgG2a antibodies in mice [25].…”

“…Recently, it was shown that oral immunization with STxB linked to a fragment of the immunogenic rotavirus nonstructural protein (NSP4) protects mice against gastroenteritis mediated by a rotavirus challenge, and this was associated with a strong Th1-mediated response [24]. In a previous study, we showed that STxB efficiently targets exogenous peptides into the MHC class I pathway and induces humoral and cell-mediated immune responses [25]. In the present study, we show that STxB delivers antigen directly to DC in vivo and induces a robust and long-lasting specific CD8 + T cell response detected directly ex vivo.…”

Human colorectal tumors and metastases express Gb3 and can be targeted by an intestinal pathogen-based delivery tool

“…Another advantage of this system is that STxB can be manipulated without altering the affinity and specificity of its interaction with Gb 3 on target cells (25). Moreover, STxB is a little immunogenic protein with MHC dependence (26).…”