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Keywords:

  • α-galactosylceramide;
  • dendritic cell;
  • cytotoxic T lymphocyte;
  • memory cell;
  • Listeria monocytogenes

Abstract

We evaluated the effect of immunization with dendritic cells (DCs) pulsed with α-galactosylceramide (αGalCer) and listeriolysin O (LLO) 91-99 peptide, a dominant cytotoxic T lymphocyte (CTL) epitope of Listeria monocytogenes by observing the responses of specific CD8+ T cells and in vivo CTL activity. DCs were pulsed with various combinations of αGalCer and LLO91-99 peptide and administered to BALB/c mice. Immunization with DCs pulsed with αGalCer and LLO91-99 at priming phase and with DCs pulsed with LLO91-99 alone at boosting phase induced stronger in vivo CTL activity, reduced the bacterial load in spleens of Listeria-challenged mice and augmented CD62L+ CD8+ central memory T cells compared with other immunization protocols. The blockade of interferon-γ (IFN-γ) at boosting phase reversed the induction of CD8+ central memory T cells and reduced the bacterial load in spleens of Listeria-challenged mice immunized with DCs pulsed with αGalCer and LLO91-99 at both phases, suggesting that αGalCer at boosting phase has deleterious effects through IFN-γ production. These results indicate that immunization with DCs pulsed with CTL epitope peptide together with αGalCer at priming phase, but not at boosting phase, is feasible for eliciting a specific CTL activity and protective immunity against infection of intracellular bacteria.