Binding of TCR Multimers and a TCR-Like Antibody with Distinct Fine-Specificities Is Dependent on the Surface Density of HLA Complexes

Abstract

Class I Major Histocompatibility Complex (MHC) molecules evolved to sample degraded protein fragments from the interior of the cell, and to display them at the surface for immune surveillance by CD8+ T cells. The ability of these lymphocytes to identify immunogenic peptide-MHC (pMHC) products on, for example, infected hepatocytes, and to subsequently eliminate those cells, is crucial for the control of hepatitis B virus (HBV). Various protein scaffolds have been designed to recapitulate the specific recognition of presented antigens with the aim to be exploited both diagnostically (e.g. to visualize cells exposed to infectious agents or cellular transformation) and therapeutically (e.g. for the delivery of drugs to compromised cells). In line with this, we report the construction of a soluble tetrameric form of an αβ T cell receptor (TCR) specific for the HBV epitope Env183–191 restricted by HLA-A*02:01, and compare its avidity and fine-specificity with a TCR-like monoclonal antibody generated against the same HLA target. A flow cytometry-based assay with streptavidin-coated beads loaded with Env183–191/HLA-A*02:01 complexes at high surface density, enabled us to probe the specific interaction of these molecules with their cognate pMHC. We demonstrate that the TCR tetramer has similar avidity for the pMHC as the antibody, but they differ in their fine-specificity, with only the TCR tetramer being capable of binding both natural variants of the Env183–191 epitope found in HBV genotypes A/C/D (187Arg) and genotype B (187Lys). Collectively, the results highlight the promiscuity of our soluble TCR, which could be an advantageous feature when targeting cells infected with a mutation-prone virus, but that binding of the soluble oligomeric TCR relies considerably on the surface density of the presented antigen.

Development of a T‐cell receptor multimer with high avidity for detecting a naturally presented tumor‐associated antigen on osteosarcoma cells

“…Affinity of FKS-D11P TCR (K D value of 4.70 × 10 −9 mol/L) was much higher than that of naturally occurring TCR binding to HLA class I/peptides (K D value of 1-50 × 10 −6 mol/L). 21 In previous studies on a soluble TCR-multimer, K D values of TCR for HLA-A2/HTLV type 1 Tax [11][12][13][14][15][16][17][18][19] , HLA-A2/HBV env [183][184][185][186][187][188][189][190][191] , HLA-A2/MART1 26-35(A27L) and HL A-A2/NY-ESO-1 157-167(C165V) were 1.06 × 10 −6 , 0.6 × 10 −6 , 5.4 × 10 −6 and 4.3 × 10 −6 mol/L, respectively. 17,19,20 These results suggested that the affinities of successfully constructed soluble TCR were also higher than the general affinity of TCR.…”

“…So far, results of several studies aimed at the development of a TCR multimer have been reported. However, most of the TCR were directed to viral antigens, human T‐cell leukemia virus type 1 tax, HIV‐gag and HBV env . Regarding a TAA‐specific TCR, only Bethune et al reported soluble TCR tetramers and dextramers directed to MART1 26‐35(A27L) and NY‐ESO‐1 157‐167(C165V) in the context of HLA‐A2.…”

TCR-mimic bispecific antibodies targeting LMP2A show potent activity against EBV malignancies

“…Since Andersen et al, first produced a mAb with TCR specificity (43), there have been over 60 TCRlike mAbs generated against HLA class I complexes. For most of these TCR-like mAbs, it is not clear which specific portions of their target peptide are crucial for recognition (33,34,36,37,(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57). Thus, even though these mAbs recognize a given pHLA, it may not be entirely specific, and any cross-reactivity against similar pHLA can lead to severe or lethal consequences when used in patients (31,58).…”