Target Structures of the CD8+-T-Cell Response to Human Cytomegalovirus: the 72-Kilodalton Major Immediate-Early Protein Revisited |
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| Authors: | Florian Kern, Ingolf Pascal Surel, Nicole Faulhaber, Claudia Fr mmel, Jens Schneider-Mergener, Constanze Sch nemann, Petra Reinke, Hans-Dieter Volk |
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| Affiliation: | Institut für Medizinische Immunologie, Medizinische Fakultät der Humboldt-Universität zu Berlin (Charité), 10098 Berlin,1. and Medizinische Klinik mit Schwerpunkt Hämatologie und Onkologie (Institut für Transfusionsmedizin und Immunhämatologie),3. and Medizinische Klinik mit Schwerpunkt Nephrologie und Intensivmedizin,2. Fakultät der Humboldt-Universität zu Berlin (Charité), 13353 Berlin, Germany |
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| Abstract: | Cell-mediated immunity plays an essential role in the control of infection with the human cytomegalovirus (HCMV). However, only a few CD8(+)-T-cell epitopes are known, with the majority being contained in the pp65 phosphoprotein, which is believed to dominate the CD8(+)-T-cell response to HCMV. Here, we have readdressed the issue of CD8(+) T cells specific for the 72-kDa major immediate-early protein (IE-1), which is nonstructural but is found very early and throughout the replicative cycle. Using a novel flow-cytometric assay, we were able to identify CD8(+)-T-cell epitopes (by IE-1 peptide-specific induction of cytokine synthesis) and simultaneously measure the frequency of cells directed against them. For this purpose, 81 pentadecamer peptides covering the complete 491-amino-acid sequence of IE-1 were tested on peripheral blood mononuclear cells of anti-HCMV immunoglobulin G-seropositive donors. At least 10 new epitopes were identified, and the fine specificity and presenting HLA molecule of the first of them was determined. The frequencies of CD8(+) T cells directed against IE-1 were similar to those directed against pp65 in donors tested with known pp65-derived peptides. Importantly, additional testing of a corresponding set of peptides covering the complete sequence of pp65 on 10 of these donors identified individuals whose CD8(+) T cells recognized IE-1 but not pp65 and vice versa, clearly illustrating that either protein may be a major target. In summary, our results suggest that IE-1 is far more important as a CD8(+)-T-cell target than current opinion suggests. |
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