Cell-permeable capsids as universal antigen carrier for the induction of an antigen-specific CD8+ T-cell response

Abstract

Vaccine platforms that can be flexibly loaded with antigens can contribute to decrease response time to emerging infections. For many pathogens and chronic infections, induction of a robust cytotoxic T lymphocytes-mediated response is desirable to control infection. Antigen delivery into the cytoplasm of antigen presenting cells favors induction of cytotoxic T cells. By fusion of the cell-permeable translocation motif (TLM)-peptide to the capsid-forming core protein of hepatitis B virus, and by insertion of the strep-tag in the spike tip (a domain that protrudes from the surface of the capsid), cell-permeable carrier capsids were generated that can be flexibly loaded with various antigens. Loading with antigens was demonstrated by electron microscopy, density gradient centrifugation and surface plasmon resonance spectroscopy. Confocal immunofluorescence microscopy showed that cell-permeable carrier capsids mediate transfer of cargo antigen into the cytoplasm. Using cell-permeable carrier capsids loaded with ovalbumin as model antigen, activation of antigen presenting cells and ovalbumin-specific CD8+ T-cells, which correlates with enhanced specific killing activity, was found. This demonstrates the capacity of TLM-carrier-capsids to serve as universal antigen carrier to deliver antigens into the cytoplasm of antigen presenting cells, which leads to enhanced MHC class I-mediated presentation and induction of antigen-specific cytotoxic T lymphocytes response.

New Routes and Opportunities for Modular Construction of Particulate Vaccines: Stick, Click, and Glue

“…Virus-like particles are pre-eminent vaccine platforms for inducing antibody responses; a central challenge for the field is to develop platforms giving potent T cell and B cell responses, important for the most intractable pathogens such as tuberculosis or HIV ( 21 , 112 , 113 ). Though existing Catcher/Tag-VLNP platforms have not yet been thoroughly assessed for T cell responses, recent work has enhanced T cell induction based on co-delivered adjuvants ( 114 ), additional helper T-cell epitopes ( 115 ), or incorporating cell-permeable peptides ( 116 ).…”

The Utilization of Cell-Penetrating Peptides in the Intracellular Delivery of Viral Nanoparticles

“…Although various CPPs have been investigated as enhancers of cell-mediated immunity for antigenic cargoes consisting of DNA vaccines, peptides, proteins, or nanoparticles (e.g., liposomes) [85,87,88,89,90,91], the impact of CPPs on VP-based vaccines has not yet been systematically investigated. However, the proof-of-principle has been presented recently in a study concerning VPs derived from the core protein of the hepatitis B virus fused with a cell-translocation motif peptide [92]. The capsids with translocation motif loaded with antigen triggered the activation of the dendritic cells and the stimulation of the CD8+ cytotoxic T lymphocyte response as well as the specific killing of the target cells in contrast with the HBV capsid, which lacked the translocation motif.…”

Intracellular Trafficking of HBV Particles

“…The peptide has been designated as translocation motif (TLM). It has been described as a novel tool for the delivery of proteins and nucleic acids into tissues and cells [59][60][61][62][63][64][65]. The functionality of TLM depends on a defined pattern of hydrophilic and hydrophobic amino acids that form a labile amphipathic alpha helix [60,62,64,66].…”