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Combination antiretroviral therapy (ART) is highly effective in controlling human immunodeficiency virus (HIV)-1 but requires lifelong medication due to the existence of a latent viral reservoir 1 , 2 . Potent broadly neutralizing antibodies (bNAbs) represent a potential alternative or adjuvant to ART. In addition to suppressing viremia, bNAbs may have T cell immunomodulatory effects as seen for other forms of immunotherapy 3 . However, this has not been established in individuals who are infected with HIV-1. Here, we document increased HIV-1 Gag-specific CD8 + T cell responses in the peripheral blood of all nine study participants who were infected with HIV-1 with suppressed blood viremia, while receiving bNAb therapy during ART interruption 4 . Increased CD4 + T cell responses were detected in eight individuals. The increased T cell responses were due both to newly detectable reactivity to HIV-1 Gag epitopes and the expansion of pre-existing measurable responses. These data demonstrate that bNAb therapy during ART interruption is associated with enhanced HIV-1-specific T cell responses. Whether these augmented T cell responses can contribute to bNAb-mediated viral control remains to be determined. T cell responses specific for HIV-1 Gag peptides increased in HIV-positive recipients of two broadly neutralizing antibodies with prolonged suppression of blood viremia during antiretroviral treatment interruption.

Manipulations capable of breaking host tolerance to induce tissue-specific T cell-mediated inflammation are of central importance to tumor immunotherapy and our understanding of autoimmunity. We demonstrate that androgen ablative therapy induces profuse T cell infiltration of benign glands and tumors in human prostates. T cell infiltration is readily apparent after 7-28 days of therapy and is comprised predominantly of a response by CD4+ T cells and comparatively fewer CD8+ T cells. Also, T cells within the treated prostate exhibit restricted TCR V β gene usage, consistent with a local oligoclonal response. Recruitment/activation of antigen-presenting cells in treated prostate tissues may contribute to local T cell activation. The induction of T cell infiltration in prostate tissues treated with androgen ablation may have implications for the immunotherapeutic treatment of prostate cancer as well as other hormone-sensitive malignancies, including breast carcinoma.

IL-15 has potential as an immunotherapeutic agent for cancer treatment because of its ability to effectively stimulate CD8 T cell, natural killer T cell, and natural killer cell immunity. However, its effectiveness may be limited by negative immunological checkpoints that attenuate immune responses. Recently a clinical trial of IL-15 in cancer immunotherapy was initiated. Finding strategies to conquer negative regulators and enhance efficacy of IL-15 is critical and meaningful for such clinical trials. In a preclinical study, we evaluated IL-15 combined with antibodies to block negative immune regulator cytotoxic T lymphocyte antigen 4 (CTLA-4) and programmed death ligand 1 (PD-L1) in an established murine transgenic adenocarcinoma of mouse prostate (TRAMP)-C2 prostate tumor model. IL-15 treatment resulted in a significant prolongation of survival in tumor-bearing animals. Coadministration of anti-PD-L1 or anti-CTLA-4 singly with IL-15 did not improve animal survival over that of IL-15 alone. However, simultaneous administration of IL-15 with anti-CTLA-4 and anti-PD-L1 was associated with increased numbers of tumor antigen-specific tetramer-positive CD8 T cells, increased CD8 T-cell tumor lytic activity, augmented antigen-specific IFN-γ release, decreased rates of tumor growth, and improved animal survival compared with IL-15 alone. Furthermore, triple combination therapy was associated with inhibition of suppressive functions of CD4+CD25+ regulatory T cells and CD8+CD122+ regulatory T cells. Thus, simultaneous blockade of CTLA-4 and PD-L1 protected CD4 and/or CD8 T-cell activity from these regulatory T cells. Combining the immune stimulatory properties of IL-15 with simultaneous removal of two critical immune inhibitory checkpoints, we showed enhancement of immune responses, leading to increased antitumor activity.

The infusion of coronavirus disease 2019 (COVID-19) patients with mesenchymal stem cells (MSCs) potentially improves clinical symptoms, but the underlying mechanism remains unclear. We conducted a randomized, single-blind, placebo-controlled (29 patients/group) phase II clinical trial to validate previous findings and explore the potential mechanisms. Patients treated with umbilical cord-derived MSCs exhibited a shorter hospital stay ( P  = 0.0198) and less time required for symptoms remission ( P  = 0.0194) than those who received placebo. Based on chest images, both severe and critical patients treated with MSCs showed improvement by day 7 ( P  = 0.0099) and day 21 ( P  = 0.0084). MSC-treated patients had fewer adverse events. MSC infusion reduced the levels of C-reactive protein, proinflammatory cytokines, and neutrophil extracellular traps (NETs) and promoted the maintenance of SARS-CoV-2-specific antibodies. To explore how MSCs modulate the immune system, we employed single-cell RNA sequencing analysis on peripheral blood. Our analysis identified a novel subpopulation of VNN2 + hematopoietic stem/progenitor-like (HSPC-like) cells expressing CSF3R and PTPRE that were mobilized following MSC infusion. Genes encoding chemotaxis factors — CX3CR1 and L-selectin — were upregulated in various immune cells. MSC treatment also regulated B cell subsets and increased the expression of costimulatory CD28 in T cells in vivo and in vitro. In addition, an in vivo mouse study confirmed that MSCs suppressed NET release and reduced venous thrombosis by upregulating kindlin-3 signaling. Together, our results underscore the role of MSCs in improving COVID-19 patient outcomes via maintenance of immune homeostasis.

The immune system of patients infected by SARS-CoV-2 is severely impaired. Detailed investigation of T cells and cytokine production in patients affected by COVID-19 pneumonia are urgently required. Here we show that, compared with healthy controls, COVID-19 patients’ T cell compartment displays several alterations involving naïve, central memory, effector memory and terminally differentiated cells, as well as regulatory T cells and PD1 + CD57 + exhausted T cells. Significant alterations exist also in several lineage-specifying transcription factors and chemokine receptors. Terminally differentiated T cells from patients proliferate less than those from healthy controls, whereas their mitochondria functionality is similar in CD4 + T cells from both groups. Patients display significant increases of proinflammatory or anti-inflammatory cytokines, including T helper type-1 and type-2 cytokines, chemokines and galectins; their lymphocytes produce more tumor necrosis factor (TNF), interferon-γ, interleukin (IL)-2 and IL-17, with the last observation implying that blocking IL-17 could provide a novel therapeutic strategy for COVID-19. COVID-19 is a serious pandemic threat to public health, but insights on the pathophysiological and immunological conditions are only emerging. Here the authors use multi-color flow cytometry to characterize CD4 + and CD8 + T cells in peripheral blood from 39 COVID-19 patients in Italy to report altered T cell activation, function and polarization.

Patients with glioblastoma currently do not sufficiently benefit from recent breakthroughs in cancer treatment that use checkpoint inhibitors 1 , 2 . For treatments using checkpoint inhibitors to be successful, a high mutational load and responses to neoepitopes are thought to be essential 3 . There is limited intratumoural infiltration of immune cells 4 in glioblastoma and these tumours contain only 30–50 non-synonymous mutations 5 . Exploitation of the full repertoire of tumour antigens—that is, both unmutated antigens and neoepitopes—may offer more effective immunotherapies, especially for tumours with a low mutational load. Here, in the phase I trial GAPVAC-101 of the Glioma Actively Personalized Vaccine Consortium (GAPVAC), we integrated highly individualized vaccinations with both types of tumour antigens into standard care to optimally exploit the limited target space for patients with newly diagnosed glioblastoma. Fifteen patients with glioblastomas positive for human leukocyte antigen (HLA)-A*02:01 or HLA-A*24:02 were treated with a vaccine (APVAC1) derived from a premanufactured library of unmutated antigens followed by treatment with APVAC2, which preferentially targeted neoepitopes. Personalization was based on mutations and analyses of the transcriptomes and immunopeptidomes of the individual tumours. The GAPVAC approach was feasible and vaccines that had poly-ICLC (polyriboinosinic-polyribocytidylic acid-poly- l -lysine carboxymethylcellulose) and granulocyte–macrophage colony-stimulating factor as adjuvants displayed favourable safety and strong immunogenicity. Unmutated APVAC1 antigens elicited sustained responses of central memory CD8 + T cells. APVAC2 induced predominantly CD4 + T cell responses of T helper 1 type against predicted neoepitopes. In a phase I trial, highly individualized peptide vaccines against unmutated tumour antigens and neoepitopes elicited sustained responses in CD8 + and CD4 + T cells, respectively, in patients with newly diagnosed glioblastoma.

Tumor cell-derived exosomes (TEX) suppress functions of immune cells. Here, changes in the gene profiles of primary human T lymphocytes exposed in vitro to exosomes were evaluated. CD4 + Tconv, CD8 + T or CD4 + CD39 + Treg were isolated from normal donors’ peripheral blood and co-incubated with TEX or exosomes isolated from supernatants of cultured dendritic cells (DEX). Expression levels of 24–27 immune response-related genes in these T cells were quantified by qRT-PCR. In activated T cells, TEX and DEX up-regulated mRNA expression levels of multiple genes. Multifactorial data analysis of ΔCt values identified T cell activation and the immune cell type, but not exosome source, as factors regulating gene expression by exosomes. Treg were more sensitive to TEX-mediated effects than other T cell subsets. In Treg, TEX-mediated down-regulation of genes regulating the adenosine pathway translated into high expression of CD39 and increased adenosine production. TEX also induced up-regulation of inhibitory genes in CD4 + Tconv, which translated into a loss of CD69 on their surface and a functional decline. Exosomes are not internalized by T cells, but signals they carry and deliver to cell surface receptors modulate gene expression and functions of human T lymphocytes.

T cell dysfunction is a hallmark of many cancers, but the basis for T cell dysfunction and the mechanisms by which antibody blockade of the inhibitory receptor PD-1 (anti-PD-1) reinvigorates T cells are not fully understood. Here we show that such therapy acts on a specific subpopulation of exhausted CD8 + tumor-infiltrating lymphocytes (TILs). Dysfunctional CD8 + TILs possess canonical epigenetic and transcriptional features of exhaustion that mirror those seen in chronic viral infection. Exhausted CD8 + TILs include a subpopulation of ‘progenitor exhausted’ cells that retain polyfunctionality, persist long term and differentiate into ‘terminally exhausted’ TILs. Consequently, progenitor exhausted CD8 + TILs are better able to control tumor growth than are terminally exhausted T cells. Progenitor exhausted TILs can respond to anti-PD-1 therapy, but terminally exhausted TILs cannot. Patients with melanoma who have a higher percentage of progenitor exhausted cells experience a longer duration of response to checkpoint-blockade therapy. Thus, approaches to expand the population of progenitor exhausted CD8 + T cells might be an important component of improving the response to checkpoint blockade. Exhausted cytotoxic T lymphocytes (CTLs) express the receptor PD-1 as a key signature. Haining and colleagues show that there are different ‘depths’ of exhaustion with a subset of exhausted CTLs that retain polyfunctionality and are responsive to PD-1 blockade.

Checkpoint blockade therapies that reactivate tumour-associated T cells can induce durable tumour control and result in the long-term survival of patients with advanced cancers 1 . Current predictive biomarkers for therapy response include high levels of intratumour immunological activity, a high tumour mutational burden and specific characteristics of the gut microbiota 2 , 3 . Although the role of T cells in antitumour responses has thoroughly been studied, other immune cells remain insufficiently explored. Here we use clinical samples of metastatic melanomas to investigate the role of B cells in antitumour responses, and find that the co-occurrence of tumour-associated CD8 + T cells and CD20 + B cells is associated with improved survival, independently of other clinical variables. Immunofluorescence staining of CXCR5 and CXCL13 in combination with CD20 reveals the formation of tertiary lymphoid structures in these CD8 + CD20 + tumours. We derived a gene signature associated with tertiary lymphoid structures, which predicted clinical outcomes in cohorts of patients treated with immune checkpoint blockade. Furthermore, B-cell-rich tumours were accompanied by increased levels of TCF7 + naive and/or memory T cells. This was corroborated by digital spatial-profiling data, in which T cells in tumours without tertiary lymphoid structures had a dysfunctional molecular phenotype. Our results indicate that tertiary lymphoid structures have a key role in the immune microenvironment in melanoma, by conferring distinct T cell phenotypes. Therapeutic strategies to induce the formation of tertiary lymphoid structures should be explored to improve responses to cancer immunotherapy. The co-occurrence of tumour-associated CD8 + T cells and CD20 + B cells, and the formation of tertiary lymphoid structures, are linked with improved survival in cohorts of patients with metastatic melanoma.

Crohn’s disease (CD) is a chronic transmural inflammation of intestinal segments caused by dysregulated interaction between microbiome and gut immune system. Here, we profile, via multiple single-cell technologies, T cells purified from the intestinal epithelium and lamina propria (LP) from terminal ileum resections of adult severe CD cases. We find that intraepithelial lymphocytes (IEL) contain several unique T cell subsets, including NKp30 + γδT cells expressing RORγt and producing IL-26 upon NKp30 engagement. Further analyses comparing tissues from non-inflamed and inflamed regions of patients with CD versus healthy controls show increased activated T H 17 but decreased CD8 + T, γδT, T FH and Treg cells in inflamed tissues. Similar analyses of LP find increased CD8 + , as well as reduced CD4 + T cells with an elevated T H 17 over Treg/T FH ratio. Our analyses of CD tissues thus suggest a potential link, pending additional validations, between transmural inflammation, reduced IEL γδT cells and altered spatial distribution of IEL and LP T cell subsets. Crohn’s disease results from transmural inflammation in the gut, but analyses of local immune populations are still lacking. Here, the authors show, by combining multiple single-cell approaches, that intraepithelial and lamina propria T cells are heterogenous, show unique phenotypes, and exhibit altered subsets upon inflammation.