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Usage in Response to Influenza Hemagglutinin 307319 Peptide1
Molecular Genetics Program, Virginia Mason Research Center, Seattle, WA 98101; and Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195
We have developed a T cell activation-based system that allows for
the selection of TCRs with defined peptide/MHC specificities from
libraries in which complementarity-determining region (CDR) sequences
have been randomized by in vitro mutagenesis. Using this system, we
have explored the sequence requirements for CDR1 and CDR2 of the TCR
-chain in a human T cell response characterized by restricted V
and V
usage. Libraries of T cells expressing receptors built on the
framework of a TCR specific for the influenza virus peptide
hemagglutinin 307319 presented by HLA-DR4, but with random sequences
inserted at CDR1
or CDR2
, were selected for response to the same
peptide/MHC ligand. A wide variety of CDR2
sequences were found to
be permissive for recognition. Indeed, >25% of T cell clones chosen
at random displayed a significant response. In contrast, a similar
challenge of a randomized CDR1
library yielded only the parental
sequence, and then only after multiple rounds of selection. T cell
clones cross-reactive on closely related HLA alleles (subtypes
of DR4) could be isolated from randomized libraries, but not clones
restricted by more distantly related alleles such as HLA-DR1. These
results indicate that, in the context of this T cell response, the
structural requirements for recognition at CDR1
are significantly
more restricted than at CDR2
. This system for mutation and selection
of TCRs in vitro may be of use in engineering T cells with defined
specificities for therapeutic applications.
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