A CTL epitope from human cytomegalovirus IE1 defined by combining prediction of HLA binding and proteasomal processing is the target of dominant immune responses in patients after allogeneic stem cell transplantation.
OBJECTIVE
In an attempt to define HCMV IE1-derived, HLA-A(*)0201-restricted epitopes, an advanced computer-based epitope prediction combining HLA binding and proteasomal cleavages in silico was performed.


RESULTS
This prediction algorithm clearly confirmed VLEETSVML to be the most likely CTL epitope. By tetramer staining, HCMV pp65 NLVPMVATV-specific CD8(+) T cells were detectable in 18/24 HCMV seropositive HLA-A(*)0201-expressing individuals (median frequency 0.58%; range 0.1%-4.7%), and IE1 VLEETSVML-specific CD8(+) T cells in 5/24 (median frequency 2.1%; range 0.1%-4.3%), respectively (p<0.01). Also in recipients of an allogeneic SCT, VLEETSVML- and NLVPMVATV-specific CD8(+) T cells were detectable in comparable frequencies, but again the number of patients with detectable pp65-specific CD8(+) T cells was higher (p=0.014). In 4/15 individuals, all demonstrating IE1 VLEETSVML-specific CD8(+) T cells prior to peptide stimulation, VLEETSVML-specific T cell lines (purity of 42.6%-98.6% of all CD3(+)/CD8(+) T cells) were successfully generated after 2-4 weeks of culture using the IFN-gamma secretion assay.


CONCLUSIONS
In conclusion, this novel prediction strategy efficiently predicted an immunodominant viral T-cell epitope.
Hebart
Holger
H
Medizinische Klinik II, Institut für Zellbiologie, Eberhard-Karls-Universität Tübingen, Tübingen, Germany.
Rauser
Georg
G
Stevanovic
Stefan
S
Haenle
Claire
C
Nussbaum
Alexander K
AK
Meisner
Christoph
C
Bissinger
Alfred L
AL
Tenzer
Stefan
S
Jahn
Gerhard
G
Loeffler
Juergen
J
Rammensee
Hans-Georg
HG
Schild
Hansjörg
H
Einsele
Hermann
H
D000328:Adult; D001782:Blood Donors; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D018984:Epitopes, T-Lymphocyte; D006680:HLA Antigens / Q000378:metabolism*; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D017874:Immediate-Early Proteins / Q000276:immunology*; D007371:Interferon-gamma / Q000378:metabolism; D008875:Middle Aged; D009097:Multienzyme Complexes / Q000378:metabolism*; D010750:Phosphoproteins / Q000276:immunology; D046988:Proteasome Endopeptidase Complex; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014184:Transplantation, Homologous; D014763:Viral Matrix Proteins / Q000276:immunology; D014764:Viral Proteins
D018984:Epitopes, T-Lymphocyte; D006680:HLA Antigens; C088645:IE1 protein, cytomegalovirus; D017874:Immediate-Early Proteins; D009097:Multienzyme Complexes; D010750:Phosphoproteins; D014763:Viral Matrix Proteins; D014764:Viral Proteins; C065418:cytomegalovirus matrix protein 65kDa; D007371:Interferon-gamma; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex