The precursor frequency of alloreactive CTLs is proportional to the number of T cell epitope specificities

The aim of this study is to find the experimental evidence that the precursor frequency of alloreactive CTLs is proportional to the number of the T-cell epitope specificities. The number of T-cell epitope specificities was manipulated by pulsing different humor of HLA-A2 restricted peptide（s） onto the T2 cells, which acted as stimulating cells to elicit allo-reaction by co-culturing with peripheral blood lymphocytes （PBLs） of HLA-A2 negative individual. Ten HLA-A2 restricted peptides （all were normal cell components ） were synthesized, and cell peptide extract was prepared by frozen and thawed. T2 cells loaded with different number of peptide（s） were co-cultured with PBLs of an HLA-A2 negative individual; the latter were stained with PKH67 in advance. Then the proliferation was monitored with flow cytometry, and the precursor frequency of the effector cells was ＇analyzed by the ModFit Software. After 6 d of culture, no proliferation was observed in the bulk culture of PBL alone, and obvious proliferation took place when PBLs of the HLA-A2 negative were co-cultured with T2 cells loaded with or without loading peptide（ s）. The precursor frequency of the alloreactive CTLs was 0.052 819 for co-culture with T2 cells loaded without peptide; however it was 0. 030 429 for T2 cells with EBV/LMP2A and 0. 030 528 for T2 cells loaded with a single autogeneic peptide, and increased up to 0. 144 942 for T2 cells loaded with 10 autogeneic peptides; the precursor frequency was 0. 203 649 when co-cultured with T2 cells loaded with miscellaneous peptides extracted from the cytoplasm of T2 cells. This study reveals that the precursor frequency of alloreactive CTLs is proportional to the number of T-cell epitope specificities, and independent of the density of the allogeneic HLA Class Ⅰ molecule. Our findings support the hypothesis that the alloreactive T cell populations comprise miscellaneous T cell clones; each is specific to corresponding pMHC. The novel constellation of peptides presented by allogeneic MHC molecules makes thousands of different epitopes, which account for the exceptional high precursor frequency of alloreactive T cells.

Exploring the therapeutic potential of precision T-Cell Receptors (TCRs) in targeting KRAS G12D cancer through in vitro development

Objectives:The Kirsten rat sarcoma virus(KRAS)G12D oncogenic mutation poses a significant challenge in treating solid tumors due to the lack of specific and effective therapeutic interventions.This study aims to explore innovative approaches in T cell receptor(TCR)engineering and characterization to target the KRAS G12D7-16 mutation,providing potential strategies for overcoming this therapeutic challenge.Methods:In this innovative study,we engineered and characterized two T cell receptors(TCRs),KDA11-01 and KDA11-02 with high affinity for the KRAS G12D7-16 mutation.These TCRs were isolated from tumor-infiltrating lymphocytes(TILs)derived from tumor tissues of patients with the KRAS G12D mutation.We assessed their specificity and anti-tumor activity in vitro using various cancer cell lines.Results:KDA11-01 and KDA11-02 demonstrated exceptional specificity for the HLA-A*11:01-restricted KRAS G12D7-16 epitope,significantly inducing IFN-γrelease and eliminating tumor cells without cross-reactivity or alloreactivity.Conclusions:The successful development of KDA11-01 and KDA11-02 introduces a novel and precise TCR-based therapeutic strategy against KRAS G12D mutation,showing potential for significant advancements in cancer immunotherapy.

Peptide-specific,allogeneic T cell response in vitro induced by a self-peptide binding to HLA-A2

The role of the bound peptide in alloreactive T-cell recognition is controversial, ranging from pep-tide-independent to peptide-specific recognition of alloreactive T-cells. The aim of this study is to find the evidence that there exist peptide/MHC complex (pMHC)-specific CTLs among alloreactive T cells generated with long-term mixed lymphocytes culture (LTMLC). A single pMHC was manipulated by loading the TAP-defective, HLA-A2 expressing T2 cells with a viral peptide (LMP2A426-434) or a self-peptide (Tyr369-377). The PBLs samples from 4 HLA-A2 positive (HLA-A2+ve) and 4 HLA-A2 negative (HLA-A2-ve) donors were included in this study. The HLA-A2+ve PBL co-cultured with the LMP2A426-434 pulsed T2 (T2/LMP) stands for the nominal T-cell response to a viral antigen, and the HLA-A2-ve PBLs co-cultured with the Tyr369-377 pulsed T2 (T2/Tyr) for alloreactive T-cell response to an allogeneic antigen. The specificity of the expanded CTLs after the LTMLC was detected by their specific cytotoxicity and binding ability to specific pMHC-tetramer. An HLA-A2 restricted, HIV peptide (Gag77-85)was included for control. The cultural bulk of HLA-A2+ve PBLs with the T2/LMP showed an elevated specific cytotoxicity against the T2/LMP compared to that against the T2/HIV (26.52%±3.72% vs 7.01%±0.87%, P<0.001), and an increased frequency of binding to LMP-tetramer compared to that binding to HIV-tetramer (0.98%±0.33% vs 0.05%±0.01%, P=0.0014). The cultural bulk of HLA-A2-ve PBLs with the T2/Tyr showed a more active cytotoxicity against the T2/Tyr than that against T2/HIV (28.07%±2.58% vs 6.87%±0.01 %, P<0.001), and a higher frequency of binding to the Tyr-tetramer than that binding to the HIV-tetramer (0.88%±0.3% vs 0.06%±0.03%, P=0.0018). Our results indicate that the LTMLC is able to expand the viral antigen-specific CTLs as well as allogeneic antigen-specific CTLs. A relatively large proportion of alloreactive CTLs should be pMHC-specific, i.e., the specificity of the alloreactive lines depends on both the bound peptide and the allotype of MHC. Our observations support the hypothesis that the cumulative effect of T cells specific to each peptide epitope could account for the strength and diversity of the alloresponse. The method using manipulated pMHC and the LTMLC to generate pMHC-specific, alloreactive CTLs is of potential importance for adoptive T-cell immunotherapy.

Selective expansion of human natural killer cells leads to enhanced alloreactivity

In allogeneic stem cell transplantation （SCT）, natural killer （NK） cells lacking their cognate inhibitory ligand can induce graft-versus-leukemia responses, without the induction of severe graft-versus-host disease （GVHD）. This feature can be exploited for cellular immunotherapy. In this study, we examined selective expansion of NK cell subsets expressing distinct killer immunoglobulin-like receptors （KIRs） within the whole human peripheral blood NK cell population, in the presence of HLA-Cw3 （C1） or Cw4 （C2） transfected K562 stimulator cells. Coculture of KIR＋ NK cells with C1 or C2 positive K562 cells, in the presence of IL-2＋ IL-15, triggered the outgrowth of NK cells that missed their cognate ligand. This resulted in an increased frequency of alloreactive KIR＋ NK cells within the whole NK cell population. Also, after preculture with K562 cells lacking their cognate ligand, we observed that this alloreactive NK population revealed higher numbers of CD107~ cells when cocultured with the relevant K562 HLA-C transfected target cells, as compared to coculture with untransfected K562 cells. This enhanced reactivity was confirmed using primary leukemic cells as target. This study demonstrates that HLA class I expression can mediate the skewing of the NK cell repertoire and enrich the population for cells with enhanced alloreactivity towards leukemic target cells. This feature may support future clinical applications of NK cell-based immunotherapy.