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Chimeric antigen receptor (CAR) T cells targeting CD19 are a breakthrough treatment for relapsed, refractory B cell malignancies 1 – 5 . Despite impressive outcomes, relapse with CD19 − disease remains a challenge. We address this limitation through a first-in-human trial of bispecific anti-CD20, anti-CD19 (LV20.19) CAR T cells for relapsed, refractory B cell malignancies. Adult patients with B cell non-Hodgkin lymphoma or chronic lymphocytic leukemia were treated on a phase 1 dose escalation and expansion trial ( NCT03019055 ) to evaluate the safety of 4-1BB–CD3ζ LV20.19 CAR T cells and the feasibility of on-site manufacturing using the CliniMACS Prodigy system. CAR T cell doses ranged from 2.5 × 10 5 –2.5 × 10 6 cells per kg. Cell manufacturing was set at 14 d with the goal of infusing non-cryopreserved LV20.19 CAR T cells. The target dose of LV20.19 CAR T cells was met in all CAR-naive patients, and 22 patients received LV20.19 CAR T cells on protocol. In the absence of dose-limiting toxicity, a dose of 2.5 × 10 6 cells per kg was chosen for expansion. Grade 3–4 cytokine release syndrome occurred in one (5%) patient, and grade 3–4 neurotoxicity occurred in three (14%) patients. Eighteen (82%) patients achieved an overall response at day 28, 14 (64%) had a complete response, and 4 (18%) had a partial response. The overall response rate to the dose of 2.5 × 10 6 cells per kg with non-cryopreserved infusion ( n  = 12) was 100% (complete response, 92%; partial response, 8%). Notably, loss of the CD19 antigen was not seen in patients who relapsed or experienced treatment failure. In conclusion, on-site manufacturing and infusion of non-cryopreserved LV20.19 CAR T cells were feasible and therapeutically safe, showing low toxicity and high efficacy. Bispecific CARs may improve clinical responses by mitigating target antigen downregulation as a mechanism of relapse. A new bispecific CAR T cell product targeting the CD20 and CD19 antigens demonstrates an excellent safety profile and high clinical efficacy in patients with B cell non-Hodgkin lymphoma and chronic lymphocytic leukemia.

CD28 and CTLA-4 (CD152) play essential roles in regulating T cell immunity, balancing the activation and inhibition of T cell responses, respectively. Although both receptors share the same ligands, CD80 and CD86, the specific requirement for two distinct ligands remains obscure. In the present study, we demonstrate that, although CTLA-4 targets both CD80 and CD86 for destruction via transendocytosis, this process results in separate fates for CTLA-4 itself. In the presence of CD80, CTLA-4 remained ligand bound, and was ubiquitylated and trafficked via late endosomes and lysosomes. In contrast, in the presence of CD86, CTLA-4 detached in a pH-dependent manner and recycled back to the cell surface to permit further transendocytosis. Furthermore, we identified clinically relevant mutations that cause autoimmune disease, which selectively disrupted CD86 transendocytosis, by affecting either CTLA-4 recycling or CD86 binding. These observations provide a rationale for two distinct ligands and show that defects in CTLA-4-mediated transendocytosis of CD86 are associated with autoimmunity.The inhibitory receptor CTLA-4 recognizes two ligands on opposing antigen-presenting cells, CD80 and CD86. Sansom and colleagues show CTLA-4 captures ligands by transendocytosis, whereupon low-affinity CD86 releases CTLA-4 at low pH to promote CTLA-4 recycling; however, high-affinity CD80 remains bound and targets CTLA-4 for ubiquitination and destruction.

Infectious and inflammatory diseases have repeatedly shown strong genetic associations within the major histocompatibility complex (MHC); however, the basis for these associations remains elusive. To define host genetic effects on the outcome of a chronic viral infection, we performed genome-wide association analysis in a multiethnic cohort of HIV-1 controllers and progressors, and we analyzed the effects of individual amino acids within the classical human leukocyte antigen (HLA) proteins. We identified > 300 genome-wide significant single-nucleotide polymorphisms (SNPs) within the MHC and none elsewhere. Specific amino acids in the HLA-B peptide binding groove, as well as an independent HLA-C effect, explain the SNP associations and reconcile both protective and risk HLA alíeles. These results implicate the nature of the HLA-viral peptide interaction as the major factor modulating durable control of HIV infection.

Outcomes for patients with refractory diffuse large B cell lymphoma (DLBCL) are poor. In the multicenter ZUMA-1 phase 1 study, we evaluated KTE-C19, an autologous CD3ζ/CD28-based chimeric antigen receptor (CAR) T cell therapy, in patients with refractory DLBCL. Patients received low-dose conditioning chemotherapy with concurrent cyclophosphamide (500 mg/m2) and fludarabine (30 mg/m2) for 3 days followed by KTE-C19 at a target dose of 2 × 106 CAR T cells/kg. The incidence of dose-limiting toxicity (DLT) was the primary endpoint. Seven patients were treated with KTE-C19 and one patient experienced a DLT of grade 4 cytokine release syndrome (CRS) and neurotoxicity. Grade ≥3 CRS and neurotoxicity were observed in 14% (n = 1/7) and 57% (n = 4/7) of patients, respectively. All other KTE-C19-related grade ≥3 events resolved within 1 month. The overall response rate was 71% (n = 5/7) and complete response (CR) rate was 57% (n = 4/7). Three patients have ongoing CR (all at 12+ months). CAR T cells demonstrated peak expansion within 2 weeks and continued to be detectable at 12+ months in patients with ongoing CR. This regimen of KTE-C19 was safe for further study in phase 2 and induced durable remissions in patients with refractory DLBCL. In a multicenter phase 1 study, Locke, Neelapu, et al. report tolerability and safety of KTE-C19, a CD19 chimeric antigen receptor technology, in patients with chemorefractory DLBCL. More importantly, KTE-C19 could provide durable clinical benefit in this difficult-to-treat patient population, demonstrating broad clinical applicability of KTE-C19.

Moreau score has been used to differentiate chronic lymphocytic leukemia (CLL) from other mature B‐cell neoplasms. However, it showed limitations in Asian patients. Therefore, we conducted a new score system replacing CD5 and CD23 with CD43 and CD180 to evaluate its diagnostic value of CLL. 237 untreated samples diagnosed with mature B‐cell neoplasms were collected and were randomly divided into an exploratory and a validation cohort by a 2:1 ratio. The expression of CD5, CD19, CD20, CD23, CD43, CD79b, CD180, CD200, FMC7, and surface immunoglobulin (SmIg) were analyzed among all the samples. A proposed score was developed based on the logistic regression model. The sensitivity and specificity of the proposed score were calculated by ROC curves. CD43/CD180, CD200, FMC7, and CD79b were included in our new CLL score, which showed a sensitivity of 91.8% and a specificity of 83.1%. These results were confirmed in a validation cohort with a sensitivity of 90.5% (p = 0.808) and a specificity of 79.5% (p = 0.639). In CD5 negative or CD23 negative CLL group, the new CLL score displayed improved sensitivity of 79.4% compared to Moreau score and CLLflow score (41.2% and 47.1%, respectively). In atypical CLL group, the new CLL score showed improved sensitivity of 84.2% compared to Moreau score and CLLflow score (61.4% and 64.9%, respectively). This proposed atypical CLL score helped to offer an accurate differentiation of CLL from non‐CLL together with morphological and molecular methods, particularly in Chinese patients with atypical immunophenotype. This study demonstrated the diagnostic value of combination of CD43 and CD180 with CD200, FMC7 and CD79b in CD5‐ or CD23‐ CLL for the first time. How to differentiate atypical CLL from other mature B cell neoplasms poses a problem in the diagnosis of CLL. This study investigated the immunophenotyping data of patients with mature B‐cell malignancies, and developed a new combined score including CD43 and CD180 which could improve the diagnostic value of CLL versus non‐CLL, particularly in atypical CLL.

Key Points MHC class II molecules bind antigenic peptides that are generated in endosomal–lysosomal antigen-processing compartments. These peptides are derived from proteins that access these compartments using various endocytic pathways and also as a result of autophagy. Proteolysis in antigen-processing compartments is regulated in antigen-presenting cells (APCs) to favour the formation of antigenic peptides that can bind to MHC class II and to avoid the complete hydrolysis of proteins to very short peptides or to amino acids. Nonspecific endocytosis processes are terminated following dendritic cell (DC) activation, but mature DCs can still internalize antigen by receptor-mediated endocytosis or phagocytosis. Using these pathways, mature DCs can generate peptide–MHC class II complexes and activate naive CD4 + T cells. The formation of antigen-processing compartments is regulated during APC activation. B cell activation results in MHC class II recruitment to endosomes and lysosomes to form these compartments, whereas in DCs, lysosomal proteases relocalize to antigen-processing compartments and enhance antigen proteolysis. APC activation leads to efficient generation of peptide–MHC class II complexes and markedly increases the expression of these complexes on the APC plasma membrane. Increased surface expression of peptide–MHC class II complexes on activated APCs is a result of enhanced MHC class II transcription and/or translation, movement of intracellular peptide–MHC class II complexes to the APC plasma membrane and reduced lysosomal MHC class II degradation. Expression of the E3 ubiquitin ligase MARCH1 by immature APCs promotes rapid turnover of peptide–MHC class II complexes. DC activation terminates MARCH1 expression and ubiquitylation of peptide–MHC class II complexes, thus increasing the half-life of peptide–MHC class II complexes. To play their part in the generation of effective adaptive immune responses, different types of antigen-presenting cell (APC) take up and process antigen in different ways. The length of time that peptide–MHC class II complexes are present on APC surfaces can also vary depending on the cell type. This Review describes the different modes and mechanisms that regulate MHC class II processing and presentation. Antigenic peptide-loaded MHC class II molecules (peptide–MHC class II) are constitutively expressed on the surface of professional antigen-presenting cells (APCs), including dendritic cells, B cells, macrophages and thymic epithelial cells, and are presented to antigen-specific CD4 + T cells. The mechanisms of antigen uptake, the nature of the antigen processing compartments and the lifetime of cell surface peptide–MHC class II complexes can vary depending on the type of APC. It is likely that these differences are important for the function of each distinct APC subset in the generation of effective adaptive immune responses. In this Review, we describe our current knowledge of the mechanisms of uptake and processing of antigens, the intracellular formation of peptide–MHC class II complexes, the intracellular trafficking of peptide–MHC class II complexes to the APC plasma membrane and their ultimate degradation.

Unlike conventional αβ T cells, γδ T cells typically recognize non-peptide ligands independently of major histocompatibility complex (MHC) restriction. Accordingly, the γδ T cell receptor (TCR) can potentially recognize a wide array of ligands; however, few ligands have been described to date. While there is a growing appreciation of the molecular bases underpinning variable (V)δ1⁺ and Vδ2⁺ γδ TCR-mediated ligand recognition, the mode of Vδ3⁺ TCR ligand engagement is unknown. MHC class I–related protein, MR1, presents vitamin B metabolites to αβ T cells known as mucosal-associated invariant T cells, diverse MR1-restricted T cells, and a subset of human γδ T cells. Here, we identify Vδ1/2⁻ γδ T cells in the blood and duodenal biopsy specimens of children that showed metabolite-independent binding of MR1 tetramers. Characterization of one Vδ3Vγ8 TCR clone showed MR1 reactivity was independent of the presented antigen. Determination of two Vδ3Vγ8 TCR-MR1-antigen complex structures revealed a recognition mechanism by the Vδ3 TCR chain that mediated specific contacts to the side of the MR1 antigen-binding groove, representing a previously uncharacterized MR1 docking topology. The binding of the Vδ3⁺ TCR to MR1 did not involve contacts with the presented antigen, providing a basis for understanding its inherent MR1 autoreactivity. We provide molecular insight into antigen-independent recognition of MR1 by a Vδ3⁺ γδ TCR that strengthens an emerging paradigm of antibody-like ligand engagement by γδ TCRs.

B cell depletion via anti-CD20 antibodies is a highly effective treatment for multiple sclerosis (MS). However, little is known about the maturation/activation stage of the returning B cell population after treatment cessation and the wider effects on other immune cells. In the present study, 15 relapsing-remitting MS patients receiving 1,000 mg of rituximab were included. B, T, and myeloid cells were analyzed before anti-CD20 administration and in different time intervals thereafter over a period of 24 mo. In comparison to the phenotype before anti-CD20 treatment, the reappearing B cell pool revealed a less mature and more activated phenotype: 1) reappearing B cells were significantly enriched in transitional (before: 10.1 ± 1.9%, after: 58.8 ± 5.2%) and mature naive phenotypes (before: 45.5 ± 3.1%, after: 25.1 ± 3.5%); 2) the frequency of memory B cells was reduced (before: 36.7 ± 3.1%, after: 8.9 ± 1.7%); and 3) reappearing B cells showed an enhanced expression of activation markers CD25 (before: 2.1 ± 0.4%, after: 9.3 ± 2.1%) and CD69 (before: 5.9 ± 1.0%, after: 21.4 ± 3.0%), and expressed significantly higher levels of costimulatory CD40 and CD86. T cells showed 1) a persistent increase in naive (CD4⁺: before: 11.8 ± 1.3%, after: 18.4 ± 3.4%; CD8⁺: before: 12.5 ± 1.4%, after: 16.5 ± 2.3%) and 2) a decrease in terminally differentiated subsets (CD4⁺: before: 47.3 ± 3.2%, after: 34.4 ± 3.7%; CD8⁺: before: 53.7 ± 2.1%, after: 49.1 ± 2.7%).

Targeted approaches to treat autoimmune diseases would improve upon current therapies that broadly suppress the immune system and lead to detrimental side effects. Antigen-specific tolerance was induced using poly(lactide-co-glycolide) nanoparticles conjugated with disease-relevant antigen to treat a model of multiple sclerosis. Increasing the nanoparticle dose and amount of conjugated antigen both resulted in more durable immune tolerance. To identify active tolerance mechanisms, we investigated downstream cellular and molecular events following nanoparticle internalization by antigen-presenting cells. The initial cell response to nanoparticles indicated suppression of inflammatory signaling pathways. Direct and functional measurement of surface MHC-restricted antigen showed positive correlation with both increasing particle dose from 1 to 100 μg/mL and increasing peptide conjugation by 2-fold. Co-stimulatory analysis of cells expressing MHC-restricted antigen revealed most significant decreases in positive co-stimulatory molecules (CD86, CD80, and CD40) following high doses of nanoparticles with higher peptide conjugation, whereas expression of a negative co-stimulatory molecule (PD-L1) remained high. T cells isolated from mice immunized against myelin proteolipid protein (PLP139–151) were co-cultured with antigen-presenting cells administered PLP139–151-conjugated nanoparticles, which resulted in reduced T cell proliferation, increased T cell apoptosis, and a stronger anti-inflammatory response. These findings indicate several potential mechanisms used by peptide-conjugated nanoparticles to induce antigen-specific tolerance. Peptide-conjugated nanoparticles induce antigen-specific tolerance in models of autoimmunity. Kuo et al. investigated cellular and molecular mechanisms of antigen-presenting cells following nanoparticle internalization. Increasing peptide conjugation and delivering higher nanoparticle doses both contributed to enhanced antigen presentation, as well as reductions in co-stimulatory expression and effector T cell responses.

Neoadjuvant ipilimumab plus nivolumab showed high pathologic response rates (pRRs) in patients with macroscopic stage III melanoma in the phase 1b OpACIN ( NCT02437279 ) and phase 2 OpACIN-neo ( NCT02977052 ) studies 1 , 2 . While the results are promising, data on the durability of these pathologic responses and baseline biomarkers for response and survival were lacking. After a median follow-up of 4 years, none of the patients with a pathologic response ( n  = 7/9 patients) in the OpACIN study had relapsed. In OpACIN-neo ( n  = 86), the 2-year estimated relapse-free survival was 84% for all patients, 97% for patients achieving a pathologic response and 36% for nonresponders ( P  < 0.001). High tumor mutational burden (TMB) and high interferon-gamma-related gene expression signature score (IFN-γ score) were associated with pathologic response and low risk of relapse; pRR was 100% in patients with high IFN-γ score/high TMB; patients with high IFN-γ score/low TMB or low IFN-γ score/high TMB had pRRs of 91% and 88%; while patients with low IFN-γ score/low TMB had a pRR of only 39%. These data demonstrate long-term benefit in patients with a pathologic response and show the predictive potential of TMB and IFN-γ score. Our findings provide a strong rationale for a randomized phase 3 study comparing neoadjuvant ipilimumab plus nivolumab versus standard adjuvant therapy with antibodies against the programmed cell death protein-1 (anti-PD-1) in macroscopic stage III melanoma. Long-term outcomes and biomarker analyses of two neoadjuvant immunotherapy clinical trials in melanoma patients support the clinical benefit of this treatment approach and uncover prognostic correlates of response.