Cellular and Molecular Mechanisms of CD8+ T Cell Differentiation, Dysfunction and Exhaustion.

T cells follow a triphasic distinct pathway of activation, proliferation and differentiation before becoming functionally and phenotypically "exhausted" in settings of chronic infection, autoimmunity and in cancer. Exhausted T cells progressively lose canonical effector functions, exhibit altered transcriptional networks and epigenetic signatures and gain constitutive expression of a broad coinhibitory receptor suite. This review outlines recent advances in our understanding of exhausted T cell biology and examines cellular and molecular mechanisms by which a state of dysfunction or exhaustion is established, and mechanisms by which exhausted T cells may still contribute to pathogen or tumour control. Further, this review describes our understanding of exhausted T cell heterogeneity and outlines the mechanisms by which checkpoint blockade differentially engages exhausted T cell subsets to overcome exhaustion and recover T cell function.

Anti-PD-1 blockade with nivolumab with and without therapeutic vaccination for virally suppressed chronic hepatitis B: A pilot study.

BACKGROUND & AIMS: To evaluate the hypothesis that increasing T cell frequency and activity may provide durable control of hepatitis B virus (HBV), we administered nivolumab, a programmed death receptor 1 (PD-1) inhibitor, with or without GS-4774, an HBV therapeutic vaccine, in virally suppressed patients with HBV e antigen (HBeAg)-negative chronic HBV. METHODS: In a phase Ib study, patients received either a single dose of nivolumab at 0.1 mg/kg (n = 2) or 0.3 mg/kg (n = 12), or 40 yeast units of GS-4774 at baseline and week 4 and 0.3 mg/kg of nivolumab at week 4 (n = 10). The primary efficacy endpoint was mean change in HBV surface antigen (HBsAg) 12 weeks after nivolumab. Safety and immunologic changes were assessed through week 24. RESULTS: There were no grade 3 or 4 adverse events or serious adverse events. All assessed patients retained T cell PD-1 receptor occupancy 6-12 weeks post-infusion, with a mean total across 0.1 and 0.3 mg/kg cohorts of 76% (95% CI 75-77), and no significant differences were observed between cohorts (p = 0.839). Patients receiving 0.3 mg/kg nivolumab without and with GS-4774 had mean declines of -0.30 (95% CI -0.46 to -0.14) and -0.16 (95% CI -0.33 to 0.01) log10 IU/ml, respectively. Patients showed significant HBsAg declines from baseline (p = 0.035) with 3 patients experiencing declines of >0.5 log10 by the end of study. One patient, whose HBsAg went from baseline 1,173 IU/ml to undetectable at week 20, experienced an alanine aminotransferase flare (grade 3) at week 4 that resolved by week 8 and was accompanied by a significant increase in peripheral HBsAg-specific T cells at week 24. CONCLUSIONS: In virally suppressed HBeAg-negative patients, checkpoint blockade was well-tolerated and led to HBsAg decline in most patients and sustained HBsAg loss in 1 patient. LAY SUMMARY: Chronic hepatitis B virus infection (CHB) is characterized by a dysfunctional immune response. In patients with CHB, inhibitory receptors, such as programmed death receptor 1 (PD-1) are overexpressed on T cells, leading to an ineffective immune response in the liver. Herein, we show that the PD-1 inhibitor, nivolumab, is safe and effective for the treatment of virally suppressed patients with CHB. Australian New Zealand Clinical Trials Registry (http://www.anzctr.org.au/) number: ACTRN12615001133527.

Plasmin and regulators of plasmin activity control the migratory capacity and adhesion of human T cells and dendritic cells by regulating cleavage of the chemokine CCL21.

The homeostatic chemokine CCL21 has a pivotal role in lymphocyte homing and compartment localisation within the lymph node, and also affects adhesion between immune cells. The effects of CCL21 are modulated by its mode of presentation, with different cellular responses seen for surface-bound and soluble forms. Here we show that plasmin cleaves surface-bound CCL21 to release the C-terminal peptide responsible for CCL21 binding to glycosaminoglycans on the extracellular matrix and cell surfaces, thereby generating the soluble form. Loss of this anchoring peptide enabled the chemotactic activity of CCL21 and reduced cell tethering. Tissue plasminogen activator did not cleave CCL21 directly but enhanced CCL21 processing through generation of plasmin from plasminogen. The tissue plasminogen activator inhibitor neuroserpin prevented processing of CCL21 and blocked the effects of soluble CCL21 on cell migration. Similarly, the plasmin-specific inhibitor α2-antiplasmin inhibited CCL21-mediated migration of human T cells and dendritic cells and tethering of T cells to APCs. We conclude that the plasmin system proteins plasmin, tissue plasminogen activator and neuroserpin regulate CCL21 function in the immune system by controlling the balance of matrix- and cell-bound CCL21.

Cell-targeted platinum nanoparticles and nanoparticle clusters.

Herein, we report the facile preparation of cell-targeted platinum nanoparticles (PtNPs), through the design of peptides that, as a single molecule added in small concentration during the synthesis, control the size of PtNP clusters during their growth, stabilise the PtNPs in aqueous suspension and enable the functionalisation of the PtNPs with a versatile range of cell-targeting ligands. Water-soluble PtNPs targeted respectively at blood group antigens and at integrin receptors are demonstrated.

Proliferating macrophages in human tumours show characteristics of monocytes responding to myelopoietic growth factors.

Macrophages play essential roles in maintaining tissue homeostasis and immune defence. However, their extensive infiltration into tumours has been linked to adverse outcomes in multiple human cancers. Within the tumour microenvironment (TME), tumour-associated macrophages (TAMs) promote tumour growth and metastasis, making them prime targets for cancer immunotherapy. Recent single-cell analysis suggest that proliferating TAMs accumulate in human cancers, yet their origins and differentiation pathways remain uncertain. Here, we show that a subpopulation of CD163+ TAMs proliferates in situ within the TME of melanoma, lung cancer, and breast cancer. Consistent with their potential role in suppressing anti-tumour activities of T cells, CD163+ TAMs express a range of potent immunosuppressive molecules, including PD-L1, PD-L2, IL-10, and TGF-ß. Other phenotypic markers strongly suggested that these cells originate from CD14+ CCR2+ monocytes, a cell population believed to have minimal capacity for proliferation. However, we demonstrate in vitro that certain myelopoietic cytokines commonly available within the TME induce robust proliferation of human monocytes, especially the combination of interleukin 3 (IL-3) and Macrophage Colony-Stimulating Factor 1 (M-CSF). Monocytic cells cultured with these cytokines efficiently modulate T cell proliferation, and their molecular phenotype recapitulates that of CD163+ TAMs. IL-3-driven proliferation of monocytic cells can be completely blocked by IL-4, associated with the induction of CDKN1A, alongside the upregulation of transcription factors linked to dendritic cell function, such as BATF3 and IRF4. Taken together, our work suggests several novel therapeutic routes to reducing immunosuppressive TAMs in human tumours, from blocking chemokine-mediated recruitment of monocytes to blocking their proliferation.

Identification and Targeting of Mutant Peptide Neoantigens in Cancer Immunotherapy.

In recent decades, adoptive cell transfer and checkpoint blockade therapies have revolutionized immunotherapeutic approaches to cancer treatment. Advances in whole exome/genome sequencing and bioinformatic detection of tumour-specific genetic variations and the amino acid sequence alterations they induce have revealed that T cell mediated anti-tumour immunity is substantially directed at mutated peptide sequences, and the identification and therapeutic targeting of patient-specific mutated peptide antigens now represents an exciting and rapidly progressing frontier of personalized medicine in the treatment of cancer. This review outlines the historical identification and validation of mutated peptide neoantigens as a target of the immune system, and the technical development of bioinformatic and experimental strategies for detecting, confirming and prioritizing both patient-specific or "private" and frequently occurring, shared "public" neoantigenic targets. Further, we examine the range of therapeutic modalities that have demonstrated preclinical and clinical anti-tumour efficacy through specifically targeting neoantigens, including adoptive T cell transfer, checkpoint blockade and neoantigen vaccination.

Erratum: Novel high-affinity EGFRvIII-specific chimeric antigen receptor T cells effectively eliminate human glioblastoma.

[This corrects the article DOI: 10.1002/cti2.1283.].

Novel high-affinity EGFRvIII-specific chimeric antigen receptor T cells effectively eliminate human glioblastoma.

OBJECTIVES: The increasing success of Chimeric Antigen Receptor (CAR) T cell therapy in haematological malignancies is reinvigorating its application in many other cancer types and with renewed focus on its application to solid tumors. We present a novel CAR against glioblastoma, an aggressive, malignant glioma, with a dismal survival rate for which treatment options have remained unchanged for over a decade. METHODS: We use the human Retained Display (ReD) antibody platform (Myrio Therapeutics) to identify a novel single-chain variable fragment (scFv) that recognises epidermal growth factor receptor mutant variant III (EGFRvIII), a common and tumor-specific mutation found in glioblastoma. We use both in vitro functional assays and an in vivo orthotopic xenograft model of glioblastoma to examine the function of our novel CAR, called GCT02, targeted using murine CAR T cells. RESULTS: Our EGFRvIII-specific scFv was found to be of much higher affinity than reported comparators reverse-engineered from monoclonal antibodies. Despite the higher affinity, GCT02 CAR T cells kill equivalently but secrete lower amounts of cytokine. In addition, GCT02-CAR T cells also mediate rapid and complete tumor elimination in vivo. CONCLUSION: We present a novel EGFRvIII-specific CAR, with effective antitumor functions both in in vitro and in a xenograft model of human glioblastoma.

Synthesis and Evaluation of Novel TLR2 Agonists as Potential Adjuvants for Cancer Vaccines.

Cancer immunotherapy has gained increasing attention due to its potential specificity and lack of adverse side effects when compared to more traditional modes of treatment. Toll-like receptor 2 (TLR2) agonists are lipopeptides possessing the S-[2,3-bis(palmitoyloxy)propyl]-l-cysteine (Pam2Cys) motif and exhibit potent immunostimulatory effects. These agonists offer a means of providing "danger signals" in order to activate the immune system toward tumor antigens. Thus, the development of TLR2 agonists is attractive in the search of potential immunostimulants for cancer. Existing SAR studies of Pam2Cys with TLR2 indicate that the structural requirements for activity are, for the most part, very intolerable. We have investigated the importance of stereochemistry, the effect of N-terminal acylation, and homologation between the two ester functionalities in Pam2Cys-conjugated lipopeptides on TLR2 activity. The R diastereomer is significantly more potent than the S diastereomer and N-terminal modification generally lowers TLR2 activity. Most notably, homologation gives rise to analogues which are comparatively active to the native Pam2Cys containing constructs.

Human T cell activation induces synaptic translocation and alters expression of the serine protease inhibitor neuroserpin and its target protease.

Contact between T cells and APCs and activation of an effective immune response trigger cellular polarization and the formation of a structured interface known as the immunological synapse. Interactions across the synapse and secretion of T cell and APC-derived factors into the perisynaptic compartment regulate synapse formation and activation of T cells. We report that the serine protease inhibitor neuroserpin, an axonally secreted protein thought to play roles in the formation of the neuronal synapse and refinement of synaptic activity, is expressed in human naïve effector memory and central memory subsets of CD4(+) and CD8(+) T cells, as well as monocytes, B cells, and NK cells. Neuroserpin partially colocalized with a TGN38/LFA-1-positive vesicle population in T cells and translocates to the immunological synapse upon activation with TCR antibodies or antigen-pulsed APCs. Activation of T cells triggered neuroserpin secretion, a rapid, 8.4-fold up-regulation of the serine protease tissue plasminogen activator, the protease target for neuroserpin, and a delayed, 6.25-fold down-regulation of neuroserpin expression. Evidence of polarization and regulated neuroserpin expression was also seen in ex vivo analyses of human lymph nodes and blood-derived T cells. Increased neuroserpin expression was seen in clusters of T cells in the paracortex of human lymph nodes, with some showing polarization to areas of cell:cell interaction. Our results support a role for neuroserpin and tissue plasminogen activator in activation-controlled proteolytic cleavage of proteins in the synaptic or perisynaptic space to modulate immune cell function.