Backlund and Holden et al. demonstrated that conjugates of antigen and cell-penetrating peptides (CPP) promoted dendritic cell-mediated antigen uptake and enhanced peptide vaccine potency in vivo. Antigen–CPP conjugates primed a polyfunctional T cell population in a cross-presenting DC-dependent manner, but not via cytosolic delivery of peptide to the MHC class I antigen processing pathway. Linkage to CPPs significantly enhanced antigen accumulation in draining lymph nodes (dLNs), increased uptake by APCs in dLNs, protected linked antigens from degradation in serum, and prolonged the duration of antigen presentation in dLNs.
Contributed by Shishir Pant
ABSTRACT: Peptide-based cancer vaccines are widely investigated in the clinic but exhibit modest immunogenicity. One approach that has been explored to enhance peptide vaccine potency is covalent conjugation of antigens with cell-penetrating peptides (CPPs), linear cationic and amphiphilic peptide sequences designed to promote intracellular delivery of associated cargos. Antigen-CPPs have been reported to exhibit enhanced immunogenicity compared to free peptides, but their mechanisms of action in vivo are poorly understood. We tested eight previously described CPPs conjugated to antigens from multiple syngeneic murine tumor models and found that linkage to CPPs enhanced peptide vaccine potency in vivo by as much as 25-fold. Linkage of antigens to CPPs did not impact dendritic cell activation but did promote uptake of linked antigens by dendritic cells both in vitro and in vivo. However, T cell priming in vivo required Batf3-dependent dendritic cells, suggesting that antigens delivered by CPP peptides were predominantly presented via the process of cross-presentation and not through CPP-mediated cytosolic delivery of peptide to the classical MHC class I antigen processing pathway. Unexpectedly, we observed that many CPPs significantly enhanced antigen accumulation in draining lymph nodes. This effect was associated with the ability of CPPs to bind to lymph-trafficking lipoproteins and protection of CPP-antigens from proteolytic degradation in serum. These two effects resulted in prolonged presentation of CPP-peptides in draining lymph nodes, leading to robust T cell priming and expansion. Thus, CPPs can act through multiple unappreciated mechanisms to enhance T cell priming that can be exploited for cancer vaccines with enhanced potency.
Author Info: (1) The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142. (2) Department of Chemistry, Massachusetts Institute of Technolo
Author Info: (1) The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142. (2) Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA (3) The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142. Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139. (4) The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142. (5) Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA (6) The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142. Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139. (7) The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142. (8) The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142. (9) Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115. Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02215. Broad Institute of MIT and Harvard, Cambridge, MA 02142. (10) Center for Neuro-Oncology, Dana-Farber Cancer Institute, Harvard University School of Medicine, Boston, MA 02215. (11) Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02215. Broad Institute of MIT and Harvard, Cambridge, MA 02142. (12) The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142. Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA Broad Institute of MIT and Harvard, Cambridge, MA 02142. Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139. (13) The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142. Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139. Broad Institute of MIT and Harvard, Cambridge, MA 02142. Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology and Harvard University, Cambridge, MA 02139. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139. Howard Hughes Medical Institute, Chevy Chase, MD 20815.
