Processing and MHC class II presentation of exogenous soluble antigen involving a proteasome-dependent cytosolic pathway in CD40-activated B cells

WT1 Trio Peptide-Based Cancer Vaccine for Rare Cancers Expressing Shared Target WT1

No standard treatment has been established for most rare cancers. Here, we report a clinical trial of a biweekly WT1 tri-peptide-based vaccine for recurrent or advanced rare cancers. Due to the insufficient number of patients available for a traditional clinical trial, the trial was designed for rare cancers expressing shared target molecule WT1. The recruitment criteria included WT1-expressing tumors as well as HLA-A*24:02 or 02:01. The primary endpoints were immunoglobulin G (IgG) antibody (Ab) production against the WT1-235 cytotoxic T lymphocyte (CTL) epitope and delayed-type hypersensitivity (DTH) skin reactions to targeted WT1 CTL epitopes. The secondary endpoints were safety and clinical efficacy. Forty-five patients received WT1 Trio, and 25 (55.6%) completed the 3-month protocol treatment. WT1-235 IgG Ab was positive in 88.0% of patients treated with WT1 Trio at 3 months, significantly higher than 62.5% of the weekly WT1-235 CTL peptide vaccine. The DTH positivity rate in WT1 Trio was 62.9%, which was not significantly different from 60.7% in the WT1-235 CTL peptide vaccine. The WT1 Trio safety was confirmed without severe treatment-related adverse events, except grade 3 myasthenia gravis-like symptoms observed in a patient with thymic cancer. Fifteen (33.3%) patients achieved stable disease after 3 months of treatment. In conclusion, the biweekly WT1 Trio vaccine containing the WT1-332 helper T lymphocyte peptide induced more robust immune responses targeting WT1 than the weekly WT1-235 CTL peptide vaccine. Therefore, WT1-targeted immunotherapy may be a potential therapeutic strategy for rare cancers.

Classic and Current Opinions in Human Organ and Tissue Transplantation

Graft tolerance is a pathophysiological condition heavily reliant on the dynamic interaction of the innate and adaptive immune systems. Genetic polymorphism determines immune responses to tissue/organ transplantation, and intricate humoral and cell-mediated mechanisms control these responses. In transplantation, the clinician's goal is to achieve a delicate equilibrium between the allogeneic immune response, undesired effects of the immunosuppressive drugs, and the existing morbidities that are potentially life-threatening. Transplant immunopathology involves sensitization, effector, and apoptosis phases which recruit and engages immunological cells like natural killer cells, lymphocytes, neutrophils, and monocytes. Similarly, these cells are involved in the transfer of normal or genetically engineered T cells. Advances in tissue transplantation would involve a profound knowledge of the molecular mechanisms that underpin the respective immunopathology involved and the design of precision medicines that are safe and effective.

Molecular Determinants Regulating the Plasticity of the MHC Class II Immunopeptidome

In the last few years, advancement in the analysis of the MHC class II (MHC-II) ligandome in several mouse and human haplotypes has increased our understanding of the molecular components that regulate the range and selection of the MHC-II presented peptides, from MHC class II molecule polymorphisms to the recognition of different conformers, functional differences in endosomal processing along the endocytic tract, and the interplay between the MHC class II chaperones DM and DO. The sum of all these variables contributes, qualitatively and quantitatively, to the composition of the MHC II ligandome, altogether ensuring that the immunopeptidome landscape is highly sensitive to any changes in the composition of the intra- and extracellular proteome for a comprehensive survey of the microenvironment for MHC II presentation to CD4 T cells.

CD86+ Antigen-Presenting B Cells Are Increased in Cancer, Localize in Tertiary Lymphoid Structures, and Induce Specific T-cell Responses

The role of B cells in antitumor immunity and their impact on emerging immunotherapies is increasingly gaining attention. B-cell effector functions include not only secretion of antibodies, but also presentation of antigens to T cells. A physiologic B-cell subset with immunostimulatory properties was described in humans, defined by a high expression of CD86 and downregulation of CD21. We used multicolor flow cytometry and IHC to elucidate abundance and spatial distribution of these antigen-presenting B cells (BAPC) in blood (peripheral blood mononuclear cells, PBMC) and tumor samples of 237 patients with cancer. Antigen-specific T-cell responses to cancer testis antigens were determined using tetramer staining and sorted BAPCs in FluoroSpot assays for selected patients. We found that BAPCs were increased in the tumor microenvironment of 9 of 10 analyzed cancer types with site-specific variation. BAPCs were not increased in renal cell carcinoma, whereas we found a systemic increase with elevated fractions in tumor-infiltrating lymphocytes (TIL) and PBMCs of patients with colorectal cancer and gastroesophageal adenocarcinoma. BAPCs were localized in lymphoid follicles of tertiary lymphoid structures (TLS) and were enriched in tumors with increased numbers of TLSs. BAPCs isolated from tumor-draining lymph nodes of patients with cancer showed increased percentages of tumor antigen-specific B cells and induced responses of autologous T cells in vitro. Our results highlight the relevance of BAPCs as professional antigen-presenting cells in tumor immunity and provide a mechanistic rationale for the observed correlation of B-cell abundance and response to immune checkpoint inhibition.

Pretreatment of Glioblastoma with Bortezomib Potentiates Natural Killer Cell Cytotoxicity through TRAIL/DR5 Mediated Apoptosis and Prolongs Animal Survival

Background: Natural killer (NK) cells are potential effectors in anti-cancer immunotherapy; however only a subset potently kills cancer cells. Here, we examined whether pretreatment of glioblastoma (GBM) with the proteasome inhibitor, bortezomib (BTZ), might sensitize tumour cells to NK cell lysis by inducing stress antigens recognized by NK-activating receptors. Methods: Combination immunotherapy of NK cells with BTZ was studied in vitro against GBM cells and in a GBM-bearing mouse model. Tumour cells were derived from primary GBMs and NK cells from donors or patients. Flow cytometry was used for viability/cytotoxicity evaluation as well as in vitro and ex vivo phenotyping. We performed a Seahorse assay to assess oxygen consumption rates and mitochondrial function, Luminex ELISA to determine NK cell secretion, protein chemistry and LC-MS/MS to detect BTZ in brain tissue. MRI was used to monitor therapeutic efficacy in mice orthotopically implanted with GBM spheroids. Results: NK cells released IFNγ, perforin and granzyme A cytolytic granules upon recognition of stress-ligand expressing GBM cells, disrupted mitochondrial function and killed 24-46% of cells by apoptosis. Pretreatment with BTZ further increased stress-ligands, induced TRAIL-R2 expression and enhanced GBM lysis to 33-76% through augmented IFNγ release (p < 0.05). Blocking NKG2D, TRAIL and TRAIL-R2 rescued GBM cells treated with BTZ from NK cells, p = 0.01. Adoptively transferred autologous NK-cells persisted in vivo (p < 0.05), diminished tumour proliferation and prolonged survival alone (Log Rank_10.19, p = 0.0014, 95%CI 0.252-0.523) or when combined with BTZ (Log Rank_5.25, p = 0.0219, 95%CI 0.295-0.408), or either compared to vehicle controls (median 98 vs. 68 days and 80 vs. 68 days, respectively). BTZ crossed the blood-brain barrier, attenuated proteasomal activity in vivo (p < 0.0001; p < 0.01 compared to vehicle control or NK cells only, respectively) and diminished tumour angiogenesis to promote survival compared to vehicle-treated controls (Log Rank_6.57, p = 0.0104, 95%CI 0.284-0.424, median 83 vs. 68 days). However, NK ablation with anti-asialo-GM1 abrogated the therapeutic efficacy. Conclusions: NK cells alone or in combination with BTZ inhibit tumour growth, but the scheduling of BTZ in vivo requires further investigation to maximize its contribution to the efficacy of the combination regimen.

Cognate Interaction With CD4+ T Cells Instructs Tumor-Associated Macrophages to Acquire M1-Like Phenotype

The immunosuppressive tumor microenvironment (TME) established by tumor cells, stromal cells and inhibitory immune cells counteracts the function of tumor reactive T cells. Tumor associated macrophages (TAMs) showing functional plasticity contribute to this process as so called M2-like macrophages can suppress the function of effector T cells and promote their differentiation into regulatory T cells (Tregs). Furthermore, tumor antigen specific CD4⁺ T effector cells can essentially sustain anti-tumoral immune responses as shown for various tumor entities, thus suggesting that cognate interaction between tumor antigen-specific CD4⁺ Th1 cells and TAMs might shift the intra-tumoral M1/M2 ratio toward M1. This study demonstrates repolarization of M2-like PECs upon MHC II-restricted interaction with tumor specific CD4⁺ Th1 cells in vitro as shown by extensive gene and protein expression analyses. Moreover, adoptive transfer of OVA-specific OT-II cells into C57BL/6 mice bearing OVA expressing IA^b−/− tumors resulted in increased accumulation of M1-like TAMs with enhanced M1 associated gene and protein expression profiles. Thus, this paper highlights a so far underestimated function of the CD4⁺ Th1/TAM axis in re-conditioning the immunosuppressive tumor microenvironment.

B Cell-Based Cancer Immunotherapy

B cells are not only producers of antibodies, but also contribute to immune regulation or act as potent antigen-presenting cells. The potential of B cells for cellular therapy is still largely underestimated, despite their multiple diverse effector functions. The CD40L/CD40 signaling pathway is the most potent activator of antigen presentation capacity in B lymphocytes. CD40-activated B cells are potent antigen-presenting cells that induce specific T-cell responses in vitro and in vivo. In preclinical cancer models in mice and dogs, CD40-activated B cell-based cancer immunotherapy was able to induce effective antitumor immunity. So far, there have been only few early-stage clinical studies involving B cell-based cancer vaccines. These trials indicate that B cell-based immunotherapy is generally safe and associated with little toxicity. Furthermore, these studies suggest that B-cell immunotherapy can elicit antitumor T-cell responses. Alongside the recent advances in cellular therapies in general, major obstacles for generation of good manufacturing practice-manufactured B-cell immunotherapies have been overcome. Thus, a first clinical trial involving CD40-activated B cells might be in reach.

A new perspective: Exploring future therapeutic strategies for cancer by understanding the dual role of B lymphocytes in tumor immunity

Our previous understanding of the role of B lymphocytes in tumor immunity is its antitumor effects. However, further evidence indicates B lymphocytes can also promote tumorigenesis by modulating immune responses. Therefore, the increasingly complex role of B lymphocytes in tumor immunity may become an important factor in tumor immunotherapy. In this review, we describe the development of B cells in tumor microenvironments. We then focus on the most controversial issues of the biological functions of B lymphocytes. Finally, we nominate B cells as therapeutic targets, which should open broad perspectives for the development of their clinical applications.

Grp94 in complexes with IgG is a soluble diagnostic marker of gastrointestinal tumors and displays immune-stimulating activity on peripheral blood immune cells

Glucose-regulated protein94 (Grp94), the most represented endoplasmic reticulum (ER)-resident heat shock protein (HSP), is a tumor antigen shared by different types of solid and hematological tumors. The tumor-specific feature of Grp94 is its translocation from the ER to the cell surface where it displays pro-oncogenic functions. This un-physiological location has important implications for both the tumor pathology and anti-tumor therapy. We wanted to address the question of whether Grp94 could be measured as liquid marker in cancer patients in order to make predictions of diagnostic and therapeutic relevance for the tumor. To this aim, we performed an in-depth investigation on patients with primary tumors of the gastrointestinal (GI) tract, using different methodological approaches to detect Grp94 in tumor tissues, plasma and peripheral blood mononuclear cells (PBMCs). Results indicate that Grp94 is not only the antigen highly expressed in any tumor tissue and in cells of tumor infiltrates, mostly B lymphocytes, but it is also found in the circulation. However, the only form in which Grp94 was detected in the plasma of any patients and in B lymphocytes induced to proliferate, was that of stable complexes with Immunoglobulin (Ig)G. Using a specific immune-enzyme assay to measure plasma Grp94-IgG complexes, we showed that Grp94-IgG complexes were significantly increased in cancer patients compared to healthy control subjects, serving as diagnostic tumor biomarker. Results also demonstrate that the stimulation of patient PBMCs with Grp94-IgG complexes led to an increased secretion of inflammatory cytokines that might drive a potentially beneficial anti-tumor effect.

B cells and the humoral response in melanoma: The overlooked players of the tumor microenvironment

Evidence of tumor-resident mature B cell and antibody compartments and reports of associations with favorable prognosis in malignant melanoma suggest that humoral immunity could participate in antitumor defense. Likely striving to confer immunological protection while being subjected to tumor-promoting immune tolerance, B cells may engender multiple functions, including antigen processing and presentation, cytokine-mediated signaling, antibody class switching, expression and secretion. We review key evidence in support of multifaceted immunological mechanisms by which B cells may counter or contribute to malignant melanoma, and we discuss their potential translational implications. Dissecting the contributions of tumor-associated humoral responses can inform future treatment avenues.