Toll-like receptor agonist therapy can profoundly augment the antitumor activity of adoptively transferred CD8(+) T cells without host preconditioning.

BACKGROUND: Lymphodepletion enhances adoptive T cell transfer (ACT) therapy by activating the innate immune system via microbes released from the radiation-injured gut. Microbial components, such as LPS, are key mediators of total body irradiation (TBI) enhancement, but our ability to strategically use these toll-like receptor (TLR) agonists to bolster the potency of T cell-based therapies for cancer remains elusive. Herein, we used TLR4 agonist LPS as a tool to address how and when to use TLR agonists to effectively improve cancer immunotherapy. METHODS: To determine the mechanisms of how innate immune activation via lymphodepletion potentiated antitumor T cell immunity, we utilized the pmel-1 melanoma mouse model. B16F10-bearing mice were preconditioned with 5Gy TBI and given a tripartite ACT therapy (consisting of transferred pmel-1 CD8(+) T cells, vaccination with fowlpox encoding gp100, and IL-2) along with TLR4 agonist LPS. The timing of LPS administration and the requirement of individual components of the tripartite therapy were evaluated based on tumor growth and the phenotype of recovered splenocytes by flow cytometry. We also evaluated the role of non-toxic and clinically used TLR4 and TLR9 agonists-monophosphoryl lipid A (MPL) and CpG Oligodeoxynucleotide (CpG ODN), respectively- for ACT therapy. RESULTS: Here we report that while exogenous administration of LPS was able to enhance adoptively transferred CD8(+) T cells' tumor destruction, LPS treatment alone did not replace individual components of the tripartite ACT regimen, or obviate TBI. Moreover, we found that sequentially administering LPS during or one day prior to ACT therapy compromised tumor regression. In contrast, administering LPS after ACT potentiated the antitumor effectiveness of the regimen, thereby supporting the expansion of transferred tumor-specific CD8(+) T cells over host CD4(+) T cells. We also found that non-toxic TLR agonists MPL and CpG potentiated the antitumor activity of infused CD8(+) T cells. Finally, TBI was no longer needed to regress tumors in mice who were depleted of host CD4(+) T cells, given a tripartite ACT regimen and then treated with low dose LPS. CONCLUSIONS: Collectively, our results identify how and when to administer TLR agonists to augment T cell-based immunotherapy in the absence or presence of host preconditioning for treatment of advanced malignancies. Our findings have clinical implications for the design of next generation immune-based therapies for patients with cancer.

Overall survival and PD-L1 expression in metastasized malignant melanoma.

BACKGROUND: Cancers are known to elude the immune system, for example, by MHC loss, FAS up-regulation, or increased secretion of TGF-beta. Recently, ligands of coinhibitory receptors like programmed cell death ligand-1 (PD-L1, B7-H1) have come to attention for their role in tumor immune escape. Various tumors have been tested for PD-L1 expression, and conflicting results were obtained regarding its correlative impact on patient survival. This study aimed to determine the prognostic relevance of PD-L1 expression for the survival of melanoma patients. METHODS: Paraffin-embedded nevi, primary melanoma, and in-transit, lymph node, and distant organ metastases from a set of 63 stages III-IV melanoma patients referred to the Netherlands Cancer Institute between 2000 and 2004 for a sentinel-node procedure or systemic therapy were studied. A large effort was invested in validating specific PD-L1 staining. In addition to immunological factors such as T-cell infiltration (CD8, CD4, and regulatory T cells), TGF-beta and MHC-I expression were assessed. RESULTS: Longitudinal analysis revealed no relevant PD-L1 expression on primary melanoma compared with metastatic disease. No significant correlations with prognosis were found regarding immunological factors, whereas known prognostic markers such as Breslow thickness and sex could be confirmed. Analyses of the overall survival of our patient cohort did not reveal a negative association with PD-L1 expression. CONCLUSIONS: Correlation of overall survival with PD-L1 expression by melanoma cells remains controversial, and future clinical studies should focus on antibody validation and time of analysis in respect to disease progression.

Genetic engineering of murine CD8+ and CD4+ T cells for preclinical adoptive immunotherapy studies.

T-cell receptor (TCR) gene therapy enables for the rapid creation of antigen-specific T cells from mice of any strain and represents a valuable tool for preclinical immunotherapy studies. Here, we describe the superiority of γ-retroviral vectors compared with lentiviral vectors for transduction of murine T cells and surprisingly illustrate robust gene-transfer into phenotypically naive/memory-stem cell like (TN/TSCM; CD62L(hi)/CD44(low)) and central memory (TCM; CD62L(hi)/CD44(hi)) CD8+ T cells using murine stem cell-based γ-retroviral vectors (MSGV1). We created MSGV1 vectors for a major histocompatibility complex-class I-restricted TCR specific for the melanocyte-differentiation antigen, glycoprotein 100 (MSGV1-pmel-1), and a major histocompatibility complex-class II-restricted TCR specific for tyrosinase-related protein-1 (MSGV1-TRP-1), and found that robust gene expression required codon optimization of TCR sequences for the pmel-1 TCR. To test for functionality, we adoptively transferred TCR-engineered T cells into mice bearing B16 melanomas and observed delayed growth of established tumors with pmel-1 TCR engineered CD8+ T cells and significant tumor regression with TRP-1 TCR transduced CD4 T cells. We simultaneously created lentiviral vectors encoding the pmel-1 TCR, but found that these vectors mediated low TCR expression in murine T cells, but robust gene expression in other murine and human cell lines. These results indicate that preclinical murine models of adoptive immunotherapies are more practical using γ-retroviral rather than lentiviral vectors.

Lethal graft-versus-host disease in mouse models of T cell receptor gene therapy.

The transfer of T cell receptor (TCR) genes can be used to induce immune reactivity toward defined antigens to which endogenous T cells are insufficiently reactive. This approach, which is called TCR gene therapy, is being developed to target tumors and pathogens, and its clinical testing has commenced in patients with cancer. In this study we show that lethal cytokine-driven autoimmune pathology can occur in mouse models of TCR gene therapy under conditions that closely mimic the clinical setting. We show that the pairing of introduced and endogenous TCR chains in TCR gene-modified T cells leads to the formation of self-reactive TCRs that are responsible for the observed autoimmunity. Furthermore, we demonstrate that adjustments in the design of gene therapy vectors and target T cell populations can be used to reduce the risk of TCR gene therapy-induced autoimmune pathology.