Co-delivery of antigen and adjuvant by site-specific conjugation to dendritic cell-targeted Fab fragments potentiates T cell responses

Abstract

The aim of therapeutic cancer vaccines is to induce tumor-specific cellular immune responses. This requires tumor antigens to be efficiently processed and presented by antigen-presenting cells, in particular dendritic cells (DCs). In addition, DCs require maturation to upregulate the surface expression and secretion of T cell costimulatory molecules, which is achieved by co-administration of adjuvants in vaccines. Peptide-based antigen vaccination is an attractive strategy due to the established biocompatibility of peptides as well as the dosing control. To enhance the efficacy of peptide-based vaccines, antigens can be targeted to DCs. Antigen–adjuvant conjugates are known to enhance T cell activation by ensuring DC maturation upon antigen delivery. In this study, we aim to combine these two approaches in a single molecule, and present a DC-targeted antibody fragment–antigen–adjuvant (AAA)-conjugate. We generate the AAA-conjugate through a combination of site-specific sortase-mediated chemoenzymatic ligation and click chemistry. Ex vivo T cell activation assays show enhanced efficacy of the AAA-conjugate compared to non-adjuvanted control conjugates. The in vivo performance of the AAA-conjugate was suboptimal, which we hypothesize to be a consequence of the hydrophobic character of the conjugate. In vivo efficacy was rescued by co-administration of antibody fragment–antigen conjugates and antibody fragment-adjuvant conjugates, in which the antigen and adjuvant were separatedly delivered using two different DC-targeting molecules. In conclusion, this study provides a proof-of-concept for effective in vivo antigen-specific T cell activation by targeted delivery of both antigen and adjuvant to DCs in a single or separate molecule using site-specific protein engineering.

Graphical abstract: Co-delivery of antigen and adjuvant by site-specific conjugation to dendritic cell-targeted Fab fragments potentiates T cell responses

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Article information

Article type
Paper
Submitted
23 Jan 2025
Accepted
24 Apr 2025
First published
05 May 2025
This article is Open Access
Creative Commons BY license

RSC Chem. Biol., 2025, Advance Article

Co-delivery of antigen and adjuvant by site-specific conjugation to dendritic cell-targeted Fab fragments potentiates T cell responses

Z. Wijfjes, I. Ramos Tomillero, C. M. Le Gall, E. A. W. van Dinther, F. Turlings, R. Classens, S. Manna, D. van Dalen, R. J. R. W. Peters, K. Schouren, F. L. Fennemann, I. M. Hagemans, F. J. van Dalen, J. M. S. van der Schoot, C. G. Figdor, A. Esser-Kahn, F. A. Scheeren and M. Verdoes, RSC Chem. Biol., 2025, Advance Article , DOI: 10.1039/D5CB00014A

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