EpiScreen™ – T cell epitope mapping
EpiScreen™ – T cell epitope mapping
EpiScreen™ T cell epitope mapping assays identify CD4+ T cell epitopes within protein sequences in order to design deimmunised variants with a lower risk of immunogenicity in the clinic.
The highly sensitive ex vivo T cell assay can identify the precise location, number and magnitude of T cell epitopes in toxins, protein scaffolds and both human and non-human proteins. This information can be used to aid deimmunisation and contributes to the reduction in risk of clinical immunogenicity.
Accurate mapping of CD4+ T cell epitopes
In CD4+ T cell epitope mapping studies, 15mer peptides with a 12 amino acid overlap are synthesised spanning the test sample sequence. Individual peptides are then tested against CD8+ T cell-depleted PBMCs which contain APCs and CD4+ T cells at physiological ratios from 50 donors with >80% DRB1 allotypic coverage of the world population. Peptides may displace other peptides already bound to MHC class II or are taken up by antigen-presenting cells such as dendritic cells which process the peptides and present them in the form of linear peptides bound in the groove of MHC class II. Binding of the T cell receptor to these MHC class II/peptide complexes by CD4+ T cells can trigger an activation cascade causing T cell proliferation. T cell activation is determined by measuring T cell proliferation using 3H-thymidine uptake.
Significant immunogenicity is determined through predetermined statistical assessment of the dataset using the T-test to provide details on magnitude of T cell response based on stimulation index normalisation against background/vehicle control. T cell epitopes are then identified by comparing overlapping immunogenic peptides to identify the core T cell epitope sequence.
Below: PBMC from 50 healthy donors were used to map the location of T cell epitopes in variable regions of antibody variants A to C. Peptides containing T cell epitopes are identified by the frequency (%) response above the background threshold (red dotted line). Five CD4+ T cell epitopes were identified in variable regions of both antibodies A and B whilst none were found in the non-immunogenic antibody C.
