Bispecific dendritic-T cell engager potentiates anti-tumor immunity.

Immune checkpoint inhibition treatment using aPD-1 monoclonal antibodies is a promising cancer immunotherapy approach. However, its effect on tumor immunity is narrow, as most patients do not respond to the treatment or suffer from recurrence. We show that the crosstalk between conventional type I dendritic cells (cDC1) and T cells is essential for an effective aPD-1-mediated anti-tumor response. Accordingly, we developed a bispecific DC-T cell engager (BiCE), a reagent that facilitates physical interactions between PD-1+ T cells and cDC1. BiCE treatment promotes the formation of active dendritic/T cell crosstalk in the tumor and tumor-draining lymph nodes. In vivo, single-cell and physical interacting cell analysis demonstrates the distinct and superior immune reprogramming of the tumors and tumor-draining lymph nodes treated with BiCE as compared to conventional aPD-1 treatment. By bridging immune cells, BiCE potentiates cell circuits and communication pathways needed for effective anti-tumor immunity.

Fc glycoengineering of a PD-L1 antibody harnesses Fcγ receptors for increased antitumor efficacy.

FDA-approved anti-PD-L1 monoclonal antibodies (mAbs) bear the IgG1 isotype, whose scaffolds are either wild-type (e.g., avelumab) or Fc-mutated and lacking Fcγ receptor (FcγR) engagement (e.g., atezolizumab). It is unknown whether variation in the ability of the IgG1 Fc region to engage FcγRs renders mAbs with superior therapeutic activity. In this study, we used humanized FcγR mice to study the contribution of FcγR signaling to the antitumor activity of human anti-PD-L1 mAbs and to identify an optimal human IgG scaffold for PD-L1 mAbs. We observed similar antitumor efficacy and comparable tumor immune responses in mice treated with anti-PD-L1 mAbs with wild-type and Fc-mutated IgG scaffolds. However, in vivo antitumor activity of the wild-type anti-PD-L1 mAb avelumab was enhanced by combination treatment with an FcγRIIB-blocking antibody, which was co-administered to overcome the suppressor function of FcγRIIB in the tumor microenvironment (TME). We performed Fc glycoengineering to remove the fucose subunit from the Fc-attached glycan of avelumab to enhance its binding to the activating FcγRIIIA. Treatment with the Fc-afucosylated version of avelumab also enhanced antitumor activity and induced stronger antitumor immune responses compared with the parental IgG. The enhanced effect by afucosylated PD-L1 antibody was dependent on neutrophils and associated with decreased frequencies of PD-L1+ myeloid cells and increased infiltration of T cells in the TME. Our data reveal that the current design of FDA-approved anti-PD-L1 mAbs does not optimally harness FcγR pathways and suggest two strategies to enhance FcγR engagement to optimize anti-PD-L1 immunotherapy.

Next Generation CD40 Agonistic Antibodies for Cancer Immunotherapy.

The clinical use of anti-CD40 agonist monoclonal antibodies (mAbs) is aimed at recruiting the immune system to fight the tumor cells. This approach has been demonstrated to be effective in various preclinical models. However, human CD40 Abs displayed only modest antitumor activity in cancer patients, characterized by low efficacy and dose-limiting toxicity. While recent studies highlight the importance of engineering the Fc region of human CD40 mAbs to optimize their agonistic potency, toxicity remains the main limiting factor, restricting clinical application to suboptimal doses. Here, we discuss the current challenges in realizing the full potential of CD40 mAbs in clinical practice, and describe novel approaches designed to circumvent the systemic toxicity associated with CD40 agonism.

Bispecific antibodies increase the therapeutic window of CD40 agonists through selective dendritic cell targeting.

Therapeutic use of agonistic anti-CD40 antibodies is a potentially powerful approach for activation of the immune response to eradicate tumors. However, the translation of this approach to clinical practice has been substantially restricted due to the severe dose-limiting toxicities observed in multiple clinical trials. Here, we demonstrate that conventional type 1 dendritic cells are essential for triggering antitumor immunity but not the toxicity of CD40 agonists, while macrophages, platelets and monocytes lead to toxic events. Therefore, we designed bispecific antibodies that target CD40 activation preferentially to dendritic cells, by coupling the CD40 agonist arm with CD11c-, DEC-205- or CLEC9A-targeting arms. These bispecific reagents demonstrate a superior safety profile compared to their parental CD40 monospecific antibody while triggering potent antitumor activity. We suggest such cell-selective bispecific agonistic antibodies as a drug platform to bypass the dose-limiting toxicities of anti-CD40, and of additional types of agonistic antibodies used for cancer immunotherapy.

BCR affinity differentially regulates colonization of the subepithelial dome and infiltration into germinal centers within Peyer's patches.

Gut-derived antigens trigger immunoglobulin A (IgA) immune responses that are initiated by cognate B cells in Peyer's patches (PPs). These cells colonize the subepithelial domes (SEDs) of the PPs and subsequently infiltrate pre-existing germinal centers (GCs). Here we defined the pre-GC events and the micro-anatomical site at which affinity-based B cell selection occurred in PPs. Using whole-organ imaging, we showed that the affinity of the B cell antigen receptor (BCR) regulated the infiltration of antigen-specific B cells into GCs but not clonal competition in the SED. Follicular helper-like T cells resided in the SED and promoted its B cell colonization, independently of the magnitude of BCR affinity. Imaging and immunoglobulin sequencing indicated that selective clonal expansion ensued during infiltration into GCs. Thus, in contrast to the events in draining lymph nodes and spleen, in PPs, T cells promoted mainly the population expansion of B cells without clonal selection during pre-GC events. These findings have major implications for the design of oral vaccines.

Mouse PVRIG Has CD8+ T Cell-Specific Coinhibitory Functions and Dampens Antitumor Immunity.

A limitation to antitumor immunity is the dysfunction of T cells in the tumor microenvironment, in part due to upregulation of coinhibitory receptors such as PD-1. Here, we describe that poliovirus receptor-related immunoglobulin domain protein (PVRIG) acts as a coinhibitory receptor in mice. Murine PVRIG interacted weakly with poliovirus receptor (PVR) but bound poliovirus receptor-like 2 (PVRL2) strongly, making the latter its principal ligand. As in humans, murine NK and NKT cells constitutively expressed PVRIG. However, when compared with humans, less PVRIG transcript and surface protein was detected in murine CD8+ T cells ex vivo However, activated CD8+ T cells upregulated PVRIG expression. In the mouse tumor microenvironment, infiltrating CD8+ T cells expressed PVRIG whereas its ligand, PVRL2, was detected predominantly on myeloid cells and tumor cells, mirroring the expression pattern in human tumors. PVRIG-deficient mouse CD8+ T cells mounted a stronger antigen-specific effector response compared with wild-type CD8+ T cells during acute Listeria monocytogenes infection. Furthermore, enhanced CD8+ T-cell effector function inhibited tumor growth in PVRIG-/- mice compared with wild-type mice and PD-L1 blockade conferred a synergistic antitumor response in PVRIG-/- mice. Therapeutic intervention with antagonistic anti-PVRIG in combination with anti-PD-L1 reduced tumor growth. Taken together, our results suggest PVRIG is an inducible checkpoint receptor and that targeting PVRIG-PVRL2 interactions results in increased CD8+ T-cell function and reduced tumor growth.See related article on p. 257.

RIPK3 as a potential therapeutic target for Gaucher's disease.

Gaucher's disease (GD), an inherited metabolic disorder caused by mutations in the glucocerebrosidase gene (GBA), is the most common lysosomal storage disease. Heterozygous mutations in GBA are a major risk factor for Parkinson's disease. GD is divided into three clinical subtypes based on the absence (type 1) or presence (types 2 and 3) of neurological signs. Type 1 GD was the first lysosomal storage disease (LSD) for which enzyme therapy became available, and although infusions of recombinant glucocerebrosidase (GCase) ameliorate the systemic effects of GD, the lack of efficacy for the neurological manifestations, along with the considerable expense and inconvenience of enzyme therapy for patients, renders the search for alternative or complementary therapies paramount. Glucosylceramide and glucosylsphingosine accumulation in the brain leads to massive neuronal loss in patients with neuronopathic GD (nGD) and in nGD mouse models. However, the mode of neuronal death is not known. Here, we show that modulating the receptor-interacting protein kinase-3 (Ripk3) pathway markedly improves neurological and systemic disease in a mouse model of GD. Notably, Ripk3 deficiency substantially improved the clinical course of GD mice, with increased survival and motor coordination and salutary effects on cerebral as well as hepatic injury.