In a recent study, a limited search for novel flu CTL epitopes
was performed; only one epitope was found with a
search restricted to only a part of the genome, one flu isolate
and one HLA-I molecule [9]. Here, we have performed a
genome-, pathogen- and HLA-wide search for new CTL epitopes
directed against influenza A virus. The genome-wide
aspect assures that all influenza virus proteins are considered,
the pathogen-wide assures that maximum conservation
is achieved, whereas the HLA-wide aspect assures maximum
coverage of human populations. Others and we have
developed immuno-bioinformatics methods to identify CTL
epitopes. Here, we have used recently improved methods
based upon combined HLA binding, TAP binding, and proteasome
processing predictions [10–13]. Note, that these
tools have been developed using large databases such as
SYFPEITHI and Los Alamos database as biological benchmarks,
i.e. they have been designed with optimal immune
epitope identification in mind. The predicted peptides were
synthesized and tested by biochemical methods for binding
to the appropriate recombinant HLA-I protein, and by
IFN- ELISPOT analysis for CTL immune responses using
PBMCs from healthy, elderly and HLA-typed Danish subjects,
which are assumed to have been exposed to multiple
influenza infections in their past. Here – even at the limited
scale of this study – we suggest several HLA-I-restricted,
influenza-specific 9mer epitopes, many of which are conserved
among several different influenza virus isolates even
including the H5N1 bird flu virus. Combining their HLArestriction
specificity, they cover virtually the entire human
population.