Neoantigen-specific CD4+ tumor-infiltrating lymphocytes are potent effectors identified within adoptive cell therapy products for metastatic melanoma patients

BACKGROUND

Adoptive cell therapy (ACT) with tumor-infiltrating lymphocytes (TILs) is a promising immunotherapeutic approach for patients with advanced solid tumors. While numerous advances have been made, the contribution of neoantigen-specific CD4+T cells within TIL infusion products remains underexplored and therefore offers a significant opportunity for progress.

METHODS

We analyzed infused TIL products from metastatic melanoma patients previously treated with ACT for the presence of neoantigen-specific T cells. TILs were enriched on reactivity to neoantigen peptides derived and prioritized from patient sample-directed mutanome analysis. Enriched TILs were further investigated to establish the clonal neoantigen response with respect to function, transcriptomics, and persistence following ACT.

RESULTS

We discovered that neoantigen-specific TIL clones were predominantly CD4+ T cells and were present in both therapeutic responders and non-responders. CD4+ TIL demonstrated an effector T cell response with cytotoxicity toward autologous tumor in a major histocompatibility complex class II-dependent manner. These results were validated by paired TCR and single cell RNA sequencing, which elucidated transcriptomic profiles distinct to neoantigen-specific CD4+ TIL.

CONCLUSIONS

Despite methods which often focus on CD8+T cells, our study supports the importance of prospective identification of neoantigen-specific CD4+ T cells within TIL products as they are a potent source of tumor-specific effectors. We further advocate for the inclusion of neoantigen-specific CD4+ TIL in future ACT protocols as a strategy to improve antitumor immunity.

SARS-CoV-2 antibody response duration and neutralization following natural infection

Background

The role of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) neutralizing antibody response from natural infection and vaccination, and the potential determinants of this response are poorly understood. Characterizing this antibody response and the factors associated with neutralization can help inform future prevention efforts and improve clinical outcomes in those infected.

Objectives

The goals of this study were to prospectively evaluate SARS-CoV-2 antibody levels and the neutralizing antibody responses among naturally infected adults and to determine demographic and behavioral factors independently associated with these responses.

Methods

Serum was collected from seropositive individuals at baseline, four-weeks, and three-months following their first study visit to be evaluated for antibody levels. Detection of neutralizing antibodies was performed at baseline. Participant demographic and behavioral information was collected via web questionnaire prior to their first visit.

Results

At baseline, higher antibody levels were associated with better neutralization capacity, with 83% of participants having detectable neutralizing antibodies. We found an age-dependent effect on antibody level and neutralization capacity with participants over 65 years having significantly higher levels. Ethnicity, heart disease, autoimmune disease, and COVID symptoms were associated with higher antibody levels, but not with increased neutralization capacity. Work environment during the pandemic correlated with increased neutralization capacity, while kidney or liver disease and traveling out of state after February 2020 correlated with decreased neutralization capacity, however neither correlated with antibody levels.

Conclusions

Our data show that natural infection by SARS-CoV-2 can induce a humoral response reflected by high antibody levels and neutralization capacity.

Abstract 887: Killer cell immunoglobulin-like receptor 2DL2 (KIR2DL2) immune checkpoint modulates CAR-T cell effector function

Significance: A modulatory role of killer immunoglobulin-like receptor 2DL2 (KIR2DL2) during T cell receptor (TCR) late signaling events has been proposed. However, its role in CAR-T cell effector function has not yet been studied. Our work aims to understand the differential modulatory effect of KIR2DL2 immune checkpoint on the effector function of therapeutic T cells used for the treatment of liquid and solid tumors.

Methods: We generated CAR-T cells, with or without KIR2DL2 overexpression, using a bicistronic retroviral vector based on the MSGV1 backbone. HLA-C1-deficient tumor cells (HLA-C1−/−) were generated by CRISPR/Cas-based knockout of the B2M gene. We designed gRNAs targeting KIR2DL2, validated their cleavage efficiency and proved the feasibility to abrogate its expression in primary T cells. We tested the inhibitory role of KIR2DL2 in vitro in HLA-C1+ or HLA-C1−/− tumor cells using impedance- and bioluminescence-based cytotoxic assays at different effector:target ratios. We evaluated cytokine production after coculture of CAR-T and target cells using the ELLA system. To assess the modulatory role of KIR2DL2 in vivo, we generated HLA-C1+ or HLA-C1− subcutaneous xenografts of human pancreatic adenocarcinoma (HPAC) cells, then treated the mice with KIR2DL2+ or KIR2DL2− PSCA-CAR-T cells. We assessed the effect of KIR2DL2 in a lymphoblastic leukemia (ALL) xenograft model (NALM6 cells), treated with either KIR2DL2+ or KIR2DL2-deficient CD19-CAR-T cells (i.v.).

Results: In vitro, KIR2DL2+ CAR-T cells were significantly less cytotoxic in an HLA-C1-dependent manner, regardless of their target antigen. Cytokine analysis after coculture showed that overexpression of KIR2DL2 in CAR-T cells impaired their ability to produce IFN-γ, IL-2 and TNF-α in presence of HLA-C1. In vivo, KIR2DL2-overexpressing PSCA-CAR-T cells injected in NSG mice harboring PSCA+/HLA-C1+ pancreatic tumors were not able to eliminate tumors. In contrast, KIR2DL2-overexpressing CAR-T cells transferred to mice harboring PSCA+/HLA-C1−/− tumor cells performed as well as their KIR2DL2− counterparts. Two gRNAs targeting KIR2DL2 were validated in primary T cells by means of an enzymatic cleavage assay and flow cytometry. Current efforts are focused on characterizing the impact of KIR2DL2 ablation on the anti-leukemia activity of CAR-T cells in vivo.

Conclusions: KIR2DL2 impairs CAR-T cell effector function and cytokine secretion in vitro in both pancreatic and ALL tumor models, and in vivo in the pancreatic model. We implemented abrogation of KIR2DL2 by CRISPR/Cas9 during CD19-CAR-T cell manufacturing. Ongoing efforts focus on testing the impact of KIR2DL2 ablation on the in vivo performance of CAR-T cells. These results strengthen the notion of KIR2DL2 as an immune checkpoint with a relevant role in T cell immunosurveillance and may constitute an actionable target to enhance adoptive cell therapies.

Citation Format: Miguel Gomez Fontela, Sebastian Snedal, Elena Martinez Planes, Daniel Abate-Daga. Killer cell immunoglobulin-like receptor 2DL2 (KIR2DL2) immune checkpoint modulates CAR-T cell effector function [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 887.

Use of phage display biopanning as a tool to design CAR-T cells against glioma stem cells

Background

Glioblastoma (GBM) is both the most common and aggressive type of primary brain tumor, associated with high mortality rates and resistance to conventional therapy. Despite recent advancements in knowledge and molecular profiling, recurrence of GBM is nearly inevitable. This recurrence has been attributed to the presence of glioma stem cells (GSCs), a small fraction of cells resistant to standard-of-care treatments and capable of self-renewal and tumor initiation. Therefore, targeting these cancer stem cells will allow for the development of more effective therapeutic strategies against GBM. We have previously identified several 7-amino acid length peptides which specifically target GSCs through in vitro and in vivo phage display biopanning.

Methods and results

We have combined two of these peptides to create a dual peptide construct (EV), and demonstrated its ability to bind GSCs in vitro and target intracranial GBM in mouse models. A peptide pull-down performed with peptide EV followed by mass spectrometry determined N-cadherin as the binding partner of the peptide, which was validated by enzyme-linked immunosorbent assay and surface plasmon resonance. To develop cytotoxic cellular products aimed at specifically targeting GSCs, chimeric antigen receptors (CARs) were engineered containing the peptide EV in place of the single-chain variable fragment (scFv) as the antigen-binding domain. EV CAR-transduced T cells demonstrated specific reactivity towards GSCs by production of interferon-gamma when exposed to GSCs, in addition to the induction of GSC-specific apoptosis as illustrated by Annexin-V staining.

Conclusion

These results exemplify the use of phage display biopanning for the isolation of GSC-targeting peptides, and their potential application in the development of novel cytotoxic therapies for GBM.

STEM-14. GLIOBLASTOMA STEM CELL TARGETING CHIMERIC ANTIGEN RECEPTOR T CELLS MODIFIED USING PHAGE DISPLAY ISOLATED PEPTIDES

Glioblastoma (GBM) is the most aggressive primary brain tumor with high mortality rates and resistance to conventional therapy. Their resistance to conventional therapy has been attributed to the presence of cancer stem cells (CSCs), a sub-population of tumor cells capable of self-renewal and tumor initiation. Developing novel strategies to specifically target GSCs may allow more effective therapeutic strategies. Using in vivo phage display biopanning, we have identified several peptides with the potential to selectively target and bind GSCs. We wished to leverage the GSC targeting properties of the peptides to augment therapeutic delivery vehicles for the development of novel targeting strategies. We used a combination of GSC targeting peptides to modify the antigen-binding domain of chimeric antigen receptors, by arranging the peptides in tandem at the N-terminus of the CAR molecule. These tandem peptides were tested for binding to GSCs in vitro and in vivo. The functionality of the CAR-T cells was evaluated by measuring cytokine release in the supernatant after overnight co-culture through ELISA. Apoptosis was evaluated by flow cytometry with Annexin V staining. Two different GSC-targeting peptide CAR-T cells demonstrated specific targeting GSCs. Following co-culture with GSCs, GSC targeting CAR-T cells were activated with release of Interferon gamma and subsequently induced GSCs specific apoptosis. These results demonstrate the use of phage display biopanning to isolate GSC targeting peptides which may be used to develop novel GBM specific cytotoxic therapies.