Abstract 1693: T cell responses to peptide-epitopes can be boosted by immune complexes of circulating anti-tetanus antibodies

Abstract

The ability of dendritic cells (DCs) to boost an antigen-specific immune response is utilized in several cancer immunotherapy strategies including therapeutic vaccination using long peptides. Naked peptides are rapidly degraded and oil-based delivery strategies trap immune cells to unwanted sites or have inappropriate adjuvant properties. To enhance the uptake of cancer or viral T cell epitopes and subsequent activation of DCs we make use of circulating antibodies to mount cellular responses against tumor antigens of interest by conjugating a B cell epitope to a T cell epitope. The conjugation of the two greatly improves antigen uptake and concomitant activation of the same DC in contrast to naked long peptides which are not conjugated. Our identified B cell epitope of choice is derived from tetanus toxin and can be targeted by tetanus-specific antibodies boosted by a standard tetanus toxoid vaccine. We have applied a modified chandler loop model preserving intact cascade systems to characterize how the tetanus-peptide conjugated vaccine is targeted to human immune cells. The B cell-T cell conjugate is taken up by human monocytes and blood DCs in an antibody-dependent manner. Rather than FcγRs, the internalization of the antigen appears to be partly mediated through the classical pathway of the complement system. Tetanus-CMV conjugates, containing a T cell epitope from the pp65 protein of cytomegalovirus (CMV), strongly reactivates memory T cells when analyzed in blood from donors with CMV-specific T cells. The CMV-specific T cells rapidly produce IFNγ and TNF in response to the conjugate illustrating that the uptake of the conjugate leads to activation of antigen-specific T cells. Uptake as well as T cell activation occurs at low concentrations of the SLP conjugate, superior to a conjugate lacking the tetanus-sequence as well as to SLPs with or without additional adjuvant (LPS). Of importance, when the B and T cell epitopes are separate entities but mixed, CMV-specific T cells are not activated, illustrating the requirement of conjugating the two. Our data show that we have a unique delivery system for peptide based vaccines that can aid induction of human T cell responses, and may potentiate immune responses in cancer patients.We are now actively working on a prostate cancer vaccine candidate using this novel loading/adjuvant technology. Citation Format: Erika A. Fletcher, Wendy van Maren, Robert Cordfunke, Jasper Dinkelaar, Ricardo Castelli, Jeroen Codee, Gijs van de Marel, Cornelis J. Melief, Ferry Ossendorp, Jan Wouter Drijfhout, Sara Mangsbo. T cell responses to peptide-epitopes can be boosted by immune complexes of circulating anti-tetanus antibodies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1693. doi:10.1158/1538-7445.AM2017-1693

An Adaptable Antibody‐Based Platform for Flexible Synthetic Peptide Delivery Built on Agonistic CD40 Antibodies

“…Next, a WBLA [ 17,21,23 ] was used to study the BiTag antibodies interaction with FcγRIIIA on natural killer (NK) cells using whole human blood. The WBLA has previously been shown to provide information on the interaction between monoclonal antibodies and the FcγRIIIA on NK cells, resulting in NK cell activation and cytokine release.…”

“…The pTag‐Ag is a SLP of 30–40 amino acid length consisting of two domains; a constant pTag, to which the scFv binds, and a variable peptide sequence that accommodates the antigenic epitope (Ag) of interest within a flanking sequence of amino acids. Herein, an 18‐mer linear B cell epitope, [ 17 ] pTag, FITC [ 18 ] fTag, were used as the constant tag for concept evaluation (Table 2). The design of the BiTag allows for the simultaneous delivery of the agonistic CD40 signaling and the cargo antigen associated to the same DC, ensuring robust T cell activation (Figure 1C).…”

“…14GIIICII originates in a mouse IgG1 antibody, previously generated by immunization of mice with a linear B‐cell epitope of tetanus toxin (amino acid sequence FIGITELKKLESKINKVF). [ 17 ] Hybridoma sequencing, outsourced to Absolute Antibody (Redcar, United Kingdom), was performed by proprietary next‐generation sequencing (NGS)‐based technology. The VH and VL regions were successfully assembled and sequenced, and based on these, a gene encoding an scFv was formed by fusing the VH to the VL, N‐terminal to C‐terminal, via a glycine‐serine linker ((Gly4Ser)4).…”