Endogenously Expressed Antigens Bind Mammalian RNA via Cationic Domains that Enhance Priming of Effector CD8T Cells by DNA Vaccination.

Jana Krieger,Reinhold Schirmbeck,Martin Wagner,Gleyder Roman-Sosa,Thomas Seufferlein,Katja Stifter,Petra Riedl

doi:10.1016/j.ymthe.2019.01.011

Jana Krieger, Reinhold Schirmbeck + Show 5 more

Open Access

https://doi.org/10.1016/j.ymthe.2019.01.011

Copy DOI

Abstract

Hepatitis B virus (HBV) core (HBV-C) antigens with homologous or heterologous HIV-tat48-57-like (HBV-C149tat) cationic domains non-specifically bind cellular RNA in vector-transfected cells. Here, we investigated whether RNA-binding to cationic domains influences the immunogenicity of endogenously expressed antigens delivered by DNA vaccination. We initially evaluated induction of HBV-C (Kb/C93)-specific CD8+ T cell responses in C57BL/6J (B6) and 1.4HBV-Smut transgenic (tg) mice that harbor a replicating HBV genome in hepatocytes by DNA immunization. RNA-binding HBV-C and HBV-C149tat antigens moderately enhanced Kb/C93-specific CD8+ T cells in B6 mice as compared with RNA-free HBV-C149 antigen (lacking cationic domains). However, only the RNA-binding antigens elicited Kb/C93-specific CD8+ T cells that inhibited HBV replication in 1.4HBV-Smut tg mice. Moreover, RNA-binding to designer antigens, which express a Kb/p15E epitope from an endogenous murine leukemia virus-derived tumor-specific gp70 protein, was crucial to prime tumor-rejecting effector CD8+ T cells in B6 mice. Antigen-bound endogenous RNAs function as a Toll-like receptor 7 (TLR-7) ligand and stimulated priming of Kb/p15E-specific CD8+ T cells in B6, but not TLR-7−/−, mice. Antigen-bound cellular RNAs thus function as an endogenous natural adjuvant in in vivo vector-transfected cells, and thus are an attractive tool to induce and/or enhance effector CD8+ T cell responses directed against chronic viral infections or tumor self-antigens by DNA vaccination.

Highlights

It has been shown that non-specific “exogenous” bacterial RNAs function as a Toll-like receptor 7 (TLR-7) ligand and stimulatedTh1-biased immune responses in mice, when co-delivered with recombinant antigens or when directly bound by particulate or non-particulate antigens.[1,2,3,4,5,6] Antigen-bound bacterial RNA has an >1,000-fold higher potency as a Th1-inducing adjuvant than free RNA mixed to a recombinant antigen.[7]
We previously showed that Hepatitis B virus (HBV)-C, but not the HBV-C149 antigen, bound mammalian RNA in transiently transfected cell lines
To elucidate RNA-mediated helper function(s) on de novo priming of hepatitis B virus core (HBV-C) (Kb/C93)-specific CD8+ T cells, we initially immunized B6 mice with vectors that express the RNA-binding HBV-C or the RNA-free HBVC149 antigen (Figure 1A)

Summary

Introduction

It has been shown that non-specific “exogenous” bacterial RNAs function as a Toll-like receptor 7 (TLR-7) ligand and stimulatedTh1-biased immune responses in mice, when co-delivered with recombinant antigens or when directly bound by particulate or non-particulate antigens.[1,2,3,4,5,6] Antigen-bound bacterial RNA has an >1,000-fold higher potency as a Th1-inducing adjuvant than free RNA mixed to a recombinant antigen.[7]. DNA vaccines expressing RNA-binding antigen(s) are attractive to target immune-stimulating cellular RNA in in vivo transfected antigen-presenting cells.[14,15]

Methods

Results

Conclusion