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The latent viral reservoir is the critical barrier for the development of a cure for HIV-1 infection. Previous studies have shown direct antiviral activity of potent HIV-1 Env-specific broadly neutralizing antibodies (bNAbs) administered when antiretroviral therapy (ART) was discontinued, but it remains unclear whether bNAbs can target the viral reservoir during ART. Here we show that administration of the V3 glycan-dependent bNAb PGT121 together with the Toll-like receptor 7 (TLR7) agonist vesatolimod (GS-9620) during ART delayed viral rebound following discontinuation of ART in simian–human immunodeficiency virus (SHIV)-SF162P3-infected rhesus monkeys in which ART was initiated during early acute infection. Moreover, in the subset of monkeys that were treated with both PGT121 and GS-9620 and that did not show viral rebound after discontinuation of ART, adoptive transfer studies and CD8-depletion studies also did not reveal virus. These data demonstrate the potential of bNAb administration together with innate immune stimulation as a possible strategy for targeting the viral reservoir. In monkeys infected with an AIDS-like virus, a combination of a broadly neutralizing antibody and an immune stimulator during antiretroviral therapy suppressed viral rebound after antiretroviral drug discontinuation.

IgA + B cells expressing programmed death ligand 1 (PD-L1) and interleukin 10 accumulate in the inflamed livers of humans and mice with non-alcoholic fatty liver disease where they promote the progression to hepatocellular carcinoma by limiting the local activation of PD-1-expressing CD8 + T cells. The role of adaptive immunity in early cancer development is controversial. Here we show that chronic inflammation and fibrosis in humans and mice with non-alcoholic fatty liver disease is accompanied by accumulation of liver-resident immunoglobulin-A-producing (IgA + ) cells. These cells also express programmed death ligand 1 (PD-L1) and interleukin-10, and directly suppress liver cytotoxic CD8 + T lymphocytes, which prevent emergence of hepatocellular carcinoma and express a limited repertoire of T-cell receptors against tumour-associated antigens. Whereas CD8 + T-cell ablation accelerates hepatocellular carcinoma, genetic or pharmacological interference with IgA + cell generation attenuates liver carcinogenesis and induces cytotoxic T-lymphocyte-mediated regression of established hepatocellular carcinoma. These findings establish the importance of inflammation-induced suppression of cytotoxic CD8 + T-lymphocyte activation as a tumour-promoting mechanism. Increased cancer risk in fatty livers Cancer progression beyond the early stages is thought to be caused in some cases by adaptive immunity, but its role remains controversial. In this study, Michael Karin and colleagues show that PD-L1-expressing IgA + B cells accumulate in the inflamed livers of humans and mice with non-alcoholic fatty liver disease. The inflammation-induced IgA + cells promote the progression to hepatocellular carcinoma by suppressing liver cytotoxic CD8 + T cells that prevent the emergence of this aggressive tumour.

T cells expressing chimeric antigen receptors (CAR T cells) targeting human CD19 (hCD19) have shown clinical efficacy against B cell malignancies 1 , 2 . CAR T cells have been less effective against solid tumours 3 – 5 , in part because they enter a hyporesponsive (‘exhausted’ or ‘dysfunctional’) state 6 – 9 triggered by chronic antigen stimulation and characterized by upregulation of inhibitory receptors and loss of effector function. To investigate the function of CAR T cells in solid tumours, we transferred hCD19-reactive CAR T cells into hCD19 + tumour-bearing mice. CD8 + CAR + tumour-infiltrating lymphocytes and CD8 + endogenous tumour-infiltrating lymphocytes expressing the inhibitory receptors PD-1 and TIM3 exhibited similar profiles of gene expression and chromatin accessibility, associated with secondary activation of nuclear receptor transcription factors NR4A1 (also known as NUR77), NR4A2 (NURR1) and NR4A3 (NOR1) by the initiating transcription factor NFAT (nuclear factor of activated T cells) 10 – 12 . CD8 + T cells from humans with cancer or chronic viral infections 13 – 15 expressed high levels of NR4A transcription factors and displayed enrichment of NR4A-binding motifs in accessible chromatin regions. CAR T cells lacking all three NR4A transcription factors ( Nr4a triple knockout) promoted tumour regression and prolonged the survival of tumour-bearing mice. Nr4a triple knockout CAR tumour-infiltrating lymphocytes displayed phenotypes and gene expression profiles characteristic of CD8 + effector T cells, and chromatin regions uniquely accessible in Nr4a triple knockout CAR tumour-infiltrating lymphocytes compared to wild type were enriched for binding motifs for NF-κB and AP-1, transcription factors involved in activation of T cells. We identify NR4A transcription factors as having an important role in the cell-intrinsic program of T cell hyporesponsiveness and point to NR4A inhibition as a promising strategy for cancer immunotherapy. Transfer of NR4A-deficient T cells expressing chimeric antigen receptors is shown to reduce tumour burden and increase survival by shifting T cell transcriptional programs away from exhaustion and towards increased effector function.

X-linked immunodeficiency with magnesium defect, EBV infection, and neoplasia (XMEN) disease are caused by deficiency of the magnesium transporter 1 (MAGT1) gene. We studied 23 patients with XMEN, 8 of whom were EBV naive. We observed lymphadenopathy (LAD), cytopenias, liver disease, cavum septum pellucidum (CSP), and increased CD4-CD8-B220-TCRαβ+ T cells (αβDNTs), in addition to the previously described features of an inverted CD4/CD8 ratio, CD4+ T lymphocytopenia, increased B cells, dysgammaglobulinemia, and decreased expression of the natural killer group 2, member D (NKG2D) receptor. EBV-associated B cell malignancies occurred frequently in EBV-infected patients. We studied patients with XMEN and patients with autoimmune lymphoproliferative syndrome (ALPS) by deep immunophenotyping (32 immune markers) using time-of-flight mass cytometry (CyTOF). Our analysis revealed that the abundance of 2 populations of naive B cells (CD20+CD27-CD22+IgM+HLA-DR+CXCR5+CXCR4++CD10+CD38+ and CD20+CD27-CD22+IgM+HLA-DR+CXCR5+CXCR4+CD10-CD38-) could differentially classify XMEN, ALPS, and healthy individuals. We also performed glycoproteomics analysis on T lymphocytes and show that XMEN disease is a congenital disorder of glycosylation that affects a restricted subset of glycoproteins. Transfection of MAGT1 mRNA enabled us to rescue proteins with defective glycosylation. Together, these data provide new clinical and pathophysiological foundations with important ramifications for the diagnosis and treatment of XMEN disease.

While effective in specific settings, adoptive chimeric antigen receptor (CAR) T cell therapy for cancer requires further improvement and optimization. Our previous results show that CD40L-overexpressing CAR T cells mobilize endogenous immune effectors, resulting in improved antitumor immunity. However, the cell populations required for this protective effect remain to be identified. Here we show, by analyzing Batf3 −/− mice lacking the CD103 + conventional dendritic cell type 1 (cDC1) subpopulation important for antigen cross-presentation, that CD40L-overexpressing CAR T cells elicit an impaired antitumor response in the absence of cDC1s. We further find that CD40L-overexpressing CAR T cells stimulate tumor-resident CD11b − CD103 − double-negative (DN) cDCs to proliferate and differentiate into cDC1s in wild-type mice. Finally, re-challenge experiments show that endogenous CD8 + T cells are required for protective antitumor memory in this setting. Our findings thus demonstrate the stimulatory effect of CD40L-overexpressing CAR T cells on innate and adaptive immune cells, and provide a rationale for using CD40L-overexpressing CAR T cells to improve immunotherapy responses. CD40L-expressing chimeric antigen receptor (CAR) T cells show enhanced anti-tumor immunity, but the cellular mechanisms are still unclear. Here we show, by analyzing mice deficient of conventional dendritic cell type 1 (cDC1) that cDC1s are induced by CD40L + CAR T cells to prime endogenous CD8 T cells for a stronger anti-tumor immune response.

Dendritic cells orchestrate the crosstalk between innate and adaptive immunity. CD8α + dendritic cells present antigens to CD8 + T cells and elicit cytotoxic T cell responses to viruses, bacteria and tumours 1 . Although lineage-specific transcriptional regulators of CD8α + dendritic cell development have been identified 2 , the molecular pathways that selectively orchestrate CD8α + dendritic cell function remain elusive. Moreover, metabolic reprogramming is important for dendritic cell development and activation 3 , 4 , but metabolic dependence and regulation of dendritic cell subsets are largely uncharacterized. Here we use a data-driven systems biology algorithm (NetBID) to identify a role of the Hippo pathway kinases Mst1 and Mst2 (Mst1/2) in selectively programming CD8α + dendritic cell function and metabolism. Our NetBID analysis reveals a marked enrichment of the activities of Hippo pathway kinases in CD8α + dendritic cells relative to CD8α − dendritic cells. Dendritic cell-specific deletion of Mst1/2—but not Lats1 and Lats2 (Lats1/2) or Yap and Taz (Yap/Taz), which mediate canonical Hippo signalling—disrupts homeostasis and function of CD8 + T cells and anti-tumour immunity. Mst1/2-deficient CD8α + dendritic cells are impaired in presentation of extracellular proteins and cognate peptides to prime CD8 + T cells, while CD8α − dendritic cells that lack Mst1/2 have largely normal function. Mechanistically, compared to CD8α − dendritic cells, CD8α + dendritic cells exhibit much stronger oxidative metabolism and critically depend on Mst1/2 signalling to maintain bioenergetic activities and mitochondrial dynamics for their functional capacities. Further, selective expression of IL-12 by CD8α + dendritic cells depends on Mst1/2 and the crosstalk with non-canonical NF-κB signalling. Our findings identify Mst1/2 as selective drivers of CD8α + dendritic cell function by integrating metabolic activity and cytokine signalling, and highlight that the interplay between immune signalling and metabolic reprogramming underlies the unique functions of dendritic cell subsets. A data-driven analysis helps to identify specific roles of the Hippo signalling kinases Mst1 and Mst2 in integrating metabolic activity and cytokine signalling in dendritic cells, and thereby orchestrating immune cell function.

DNA mismatch repair-deficient (MMR-d) cancers present an abundance of neoantigens that is thought to explain their exceptional responsiveness to immune checkpoint blockade (ICB) 1 , 2 . Here, in contrast to other cancer types 3 – 5 , we observed that 20 out of 21 (95%) MMR-d cancers with genomic inactivation of β2-microglobulin (encoded by B2M ) retained responsiveness to ICB, suggesting the involvement of immune effector cells other than CD8 + T cells in this context. We next identified a strong association between B2M inactivation and increased infiltration by γδ T cells in MMR-d cancers. These γδ T cells mainly comprised the Vδ1 and Vδ3 subsets, and expressed high levels of PD-1, other activation markers, including cytotoxic molecules, and a broad repertoire of killer-cell immunoglobulin-like receptors. In vitro, PD-1 + γδ T cells that were isolated from MMR-d colon cancers exhibited enhanced reactivity to human leukocyte antigen (HLA)-class-I-negative MMR-d colon cancer cell lines and B2M -knockout patient-derived tumour organoids compared with antigen-presentation-proficient cells. By comparing paired tumour samples from patients with MMR-d colon cancer that were obtained before and after dual PD-1 and CTLA-4 blockade, we found that immune checkpoint blockade substantially increased the frequency of γδ T cells in B2M-deficient cancers. Taken together, these data indicate that γδ T cells contribute to the response to immune checkpoint blockade in patients with HLA-class-I-negative MMR-d colon cancers, and underline the potential of γδ T cells in cancer immunotherapy. γδ T cells contribute to the response to immune checkpoint blockade treatment in patients with HLA-class-I-negative DNA mismatch repair-deficient colon cancers. .

The AP1 transcription factor Batf3 is required for homeostatic development of CD8α + classical dendritic cells that prime CD8 T-cell responses against intracellular pathogens. Here we identify an alternative, Batf3 -independent pathway in mice for CD8α + dendritic cell development operating during infection with intracellular pathogens and mediated by the cytokines interleukin (IL)-12 and interferon-γ. This alternative pathway results from molecular compensation for Batf3 provided by the related AP1 factors Batf , which also functions in T and B cells, and Batf2 induced by cytokines in response to infection. Reciprocally, physiological compensation between Batf and Batf3 also occurs in T cells for expression of IL-10 and CTLA4. Compensation among BATF factors is based on the shared capacity of their leucine zipper domains to interact with non-AP1 factors such as IRF4 and IRF8 to mediate cooperative gene activation. Conceivably, manipulating this alternative pathway of dendritic cell development could be of value in augmenting immune responses to vaccines. The roles of BATF transcription factors in dendritic cell differentiation are studied, providing evidence for molecular compensation by related family members; compensation is based on the interaction of the BATF leucine zipper domains with IRF factors to mediate cooperative gene activation. Immune responses linked to BATF–IRF4 Kenneth Murphy and colleagues study the roles of the AP-1 transcription factor BATF in dendritic-cell differentiation — a process that primes CD8 + T-cell responses to intracellular pathogens — and provide evidence for molecular compensation by related family members. Compensation is based on the interaction of the BATF leucine-zipper domains with the interferon regulatory factors IRF4 and IRF8 to mediate cooperative gene activation. In a complementary study, Warren Leonard and colleagues provide evidence that IRF4 regulates CD4 + T-cell differentiation and T H 17 function by cooperative binding interactions with the AP-1 family members BATF and JUN. These studies point to potential new targets for manipulating key immune responses that depend on BATF–IRF4 interactions.

Immune-related adverse events, particularly severe toxicities such as myocarditis, are major challenges to the utility of immune checkpoint inhibitors (ICIs) in anticancer therapy 1 . The pathogenesis of ICI-associated myocarditis (ICI-MC) is poorly understood. Pdcd1 –/– Ctla4 +/– mice recapitulate clinicopathological features of ICI-MC, including myocardial T cell infiltration 2 . Here, using single-cell RNA and T cell receptor (TCR) sequencing of cardiac immune infiltrates from Pdcd1 –/– Ctla4 +/– mice, we identify clonal effector CD8 + T cells as the dominant cell population. Treatment with anti-CD8-depleting, but not anti-CD4-depleting, antibodies improved the survival of Pdcd1 –/– Ctla4 +/– mice. Adoptive transfer of immune cells from mice with myocarditis induced fatal myocarditis in recipients, which required CD8 + T cells. The cardiac-specific protein α-myosin, which is absent from the thymus 3 , 4 , was identified as the cognate antigen source for three major histocompatibility complex class I-restricted TCRs derived from mice with fulminant myocarditis. Peripheral blood T cells from three patients with ICI-MC were expanded by α-myosin peptides. Moreover, these α-myosin-expanded T cells shared TCR clonotypes with diseased heart and skeletal muscle, which indicates that α-myosin may be a clinically important autoantigen in ICI-MC. These studies underscore the crucial role for cytotoxic CD8 + T cells, identify a candidate autoantigen in ICI-MC and yield new insights into the pathogenesis of ICI toxicity. Cytotoxic CD8 + T cells specific for α-myosin are identified as pivotal players in myocarditis associated with immune checkpoint inhibitor anticancer therapies.

Background The CD4/CD8 ratio has been associated with the risk of AIDS and non-AIDS events. We describe trends in immunological parameters in people who underwent a switch to monotherapy or dual therapy, compared to a control group remaining on triple antiretroviral therapy (ART). Methods We included patients in Icona who started a three-drug combination ART regimen from an ART-naïve status and achieved a viral load ≤ 50 copies/mL; they were subsequently switched to another triple or to a mono or double regimen. Standard linear regression at fixed points in time (12-24 months after the switch) and linear mixed model analysis with random intercepts and slopes were used to compare CD4 and CD8 counts and their ratio over time according to regimen types (triple vs. dual and vs. mono). Results A total of 1241 patients were included; 1073 switched to triple regimens, 104 to dual (72 with 1 nucleoside reverse transcriptase inhibitor (NRTI), 32 NRTI-sparing), and 64 to monotherapy. At 12 months after the switch, for the multivariable linear regression the mean change in the log 10 CD4/CD8 ratio for patients on dual therapy was −0.03 (95% confidence interval (CI) –0.05, –0.0002), and the mean change in CD8 count was +99 (95% CI +12.1, +186.3), taking those on triple therapy as reference. In contrast, there was no evidence for a difference in CD4 count change. When using all counts, there was evidence for a significant difference in the slope of the ratio and CD8 count between people who were switched to triple (points/year change ratio = +0.056, CD8 = −25.7) and those to dual regimen (ratio = −0.029, CD8 = +110.4). Conclusions We found an increase in CD8 lymphocytes in people who were switched to dual regimens compared to those who were switched to triple. Patients on monotherapy did not show significant differences. The long-term implications of this difference should be ascertained.