Transnuclear TRP1-Specific CD8 T Cells with High or Low Affinity TCRs Show Equivalent Antitumor Activity

Abstract

We have generated, via somatic cell nuclear transfer, two independent lines of transnuclear (TN) mice, using as nuclear donors CD8 T cells, sorted by tetramer staining, that recognize the endogenous melanoma antigen TRP1. These two lines of nominally identical specificity differ greatly in their affinity for antigen (TRP1high or TRP1low) as inferred from tetramer dissociation and peptide responsiveness. Ex vivo-activated CD8 T cells from either TRP1high or TRP1low mice show cytolytic activity in 3D tissue culture and in vivo, and slow the progression of subcutaneous B16 melanoma. Although naïve TRP1low CD8 T cells do not affect tumor growth, upon activation these cells function indistinguishably from TRP1high cells in vivo, limiting tumor cell growth and increasing mouse survival. The anti-tumor effect of both TRP1high and TRP1low CD8 T cells is enhanced in RAG-deficient hosts. However, tumor outgrowth eventually occurs, likely due to T cell exhaustion. The TRP1 TN mice are an excellent model for examining the functional attributes of T cells conferred by TCR affinity, and they may serve as a platform for screening immunomodulatory cancer therapies.

Target Density, Not Affinity or Avidity of Antigen Recognition, Determines Adoptive T Cell Therapy Outcomes in a Mouse Lymphoma Model

“…Although it seems counterintuitive, this is likely due to the reduced ability of high-affinity CTL to undergo serial triggering, where one MHC-peptide complex sequentially engages several TCR to achieve a critical activation threshold (23)(24)(25). Indeed, our data support findings from both mouse (26) and human (27) antimelanoma CTL where CTL with higher-avidity TCR do not elicit more potent antitumor activity than those with loweravidity TCR. An advantage of using CTL expressing low-affinity TCR is that the risk for toxic recognition of low-abundance TAA in normal tissues may be averted.…”

Profiling lymphocyte interactions at the single-cell level by microfluidic cell pairing

“…CD8 T cells from both mice recognize the identical epitope derived from endogenous melanoma antigen TRP1 (tyrosinaserelated protein 1, expressed in normal melanocytes and overexpressed in melanoma) but with tenfold different affinities as inferred from class I MHC tetramer dissociation. Despite the difference in their affinities, activated CD8 T cells from both high-affinity (TRP1 high ) and low-affinity (TRP1 low ) mice delayed ARTICLE the growth of melanoma in vivo to a similar extent 26 . Here we explored the implications of TCR affinity difference on their early activation dynamics.…”

“…We then applied our device to characterize the early activation dynamics of two lines of TN mice generated via somatic cell nuclear transfer 26 . CD8 T cells from both mice recognize the identical epitope derived from endogenous melanoma antigen TRP1 (tyrosinaserelated protein 1, expressed in normal melanocytes and overexpressed in melanoma) but with tenfold different affinities as inferred from class I MHC tetramer dissociation.…”

“…Using our devices, we demonstrate dynamic pairwise profiling of interactions between CD8 T cells and APCs at the single-pair level and perform measurements on both partners. We further used our devices to characterize the early activation dynamics of CD8 T cells from two melanoma-specific TN mouse models, which recognize the identical antigen with vastly different affinities 26 . We observed that the differences in T-cell receptor (TCR) affinity for pMHCI (peptides bound to major histocompatibility complex class I glycoprotein) complex result in qualitatively and quantitatively different T-cell activation kinetics.…”

To affinity and beyond: Harnessing the T Cell receptor for cancer immunotherapy

“…Surprisingly, the high and low affinity TCRs generated showed equivalent anti-tumor activity as assessed by CD8 cytotoxic parameters. 77 Taken together these data present a salient picture that calls into question the relevance of high affinity TCRs for adoptive immunotherapy.…”