Target structures of the CD8(+)-T-cell response to human cytomegalovirus: the 72-kilodalton major immediate-early protein revisited.
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.
Kern
F
F
Institut für Medizinische Immunologie, Medizinische Fakultät der Humboldt-Universität zu Berlin (Charité), 10098 Berlin, Germany. florian.kern@charite.de
Surel
I P
IP
Faulhaber
N
N
Frömmel
C
C
Schneider-Mergener
J
J
Schönemann
C
C
Reinke
P
P
Volk
H D
HD
D017951:Antigen Presentation; D000956:Antigens, Viral / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000821:virology*; D003587:Cytomegalovirus / Q000276:immunology*; D003586:Cytomegalovirus Infections / Q000276:immunology*; D000939:Epitopes / Q000276:immunology; D006801:Humans; D017874:Immediate-Early Proteins / Q000276:immunology*; D007111:Immunity, Cellular; D007371:Interferon-gamma / Q000276:immunology; D015534:Trans-Activators / Q000276:immunology*
D000956:Antigens, Viral; D000939:Epitopes; C094775:IE-1 protein, murine cytomegalovirus; D017874:Immediate-Early Proteins; D015534:Trans-Activators; D007371:Interferon-gamma