CD8 + T-cell priming and boosting: more antigen-presenting DC, or more antigen per DC?
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ORIGINAL ARTICLE
CD8+ T‑cell priming and boosting: more antigen‑presenting DC, or more antigen per DC? Niels Schaft · Verena Wellner · Christian Wohn · Gerold Schuler · Jan Dörrie
Received: 19 July 2013 / Accepted: 25 September 2013 / Published online: 10 October 2013 © Springer-Verlag Berlin Heidelberg 2013
Abstract RNA transfection is a standard method to load dendritic cells (DC) with antigen for therapeutic cancer vaccination. While electroporation yields high transfection efficiency and satisfying expression levels, lipofection results in only few cells expressing high amounts of antigen. We compared antigen loading of human monocytederived DC by MelanA RNA electroporation and lipofection. No differences in phenotype or migrational capacity were detected, but lipofected DC induced stronger cytokine secretion by antigen-specific T cells and were superior in priming and boosting of MelanA-specific CD8+ T cells. Interestingly, T cells stimulated with the differently transfected DC did not differ in their functional avidity. To determine whether the amount of antigen per cell is indeed responsible for the superiority of the lipofected DC, we increased the amount of MelanA RNA fivefold and mixed those DC with mock-electroporated ones to mimic the antigen distribution of lipofected cells. This significantly improved the stimulatory capacity, indicating that indeed the amount of antigen per cell seems to be the responsible feature for the observed superiority of lipofected DCs. These data suggest that a few DC that express high amounts of antigen are more immunogenic than many DC
Electronic supplementary material The online version of this article (doi:10.1007/s00262-013-1481-z) contains supplementary material, which is available to authorized users. N. Schaft · V. Wellner · C. Wohn · G. Schuler · J. Dörrie (*) Department of Dermatology, Universitätsklinikum Erlangen, Hartmannstraße 14, 91052 Erlangen, Germany e-mail: jan.doerrie@uk‑erlangen.de Present Address: C. Wohn ErasmusMC, Rotterdam, The Netherlands
expressing lower amounts, although this needs to be tested in a two-armed immunogenicity trial. Keywords Lipofection · Electroporation · Antigen presentation · Dendritic cells · T cells
Introduction The primary purpose of therapeutic tumor immunization, i.e., anticancer vaccination, is to overcome the weak and ineffective immune response against the tumor and to induce a robust and long-lasting tumor-specific T-cell response. DC, as nature’s own adjuvant, are the most commonly targeted APC in this field (reviewed in [1]). Apart from in vivo-targeting strategies, DC can be generated from monocytes in sufficient quantities in cell culture and can be loaded with antigen in vitro, before being reapplied into the patient [2]. An elegant way to gain direct access to the cell’s antigen processing and MHC presentation machinery is the expression of Ag as full-length protein within the DC. This allows the generation and presentation of all biologically relevant peptides that can be derived from the protein of inte
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