Nucleobase adducts bind MR1 and stimulate MR1-restricted T cells.

MR1T cells are a recently found class of T cells that recognize antigens presented by the major histocompatibility complex-I-related molecule MR1 in the absence of microbial infection. The nature of the self-antigens that stimulate MR1T cells remains unclear, hampering our understanding of their physiological role and therapeutic potential. By combining genetic, pharmacological, and biochemical approaches, we found that carbonyl stress and changes in nucleobase metabolism in target cells promote MR1T cell activation. Stimulatory compounds formed by carbonyl adducts of nucleobases were detected within MR1 molecules produced by tumor cells, and their abundance and antigenicity were enhanced by drugs that induce carbonyl accumulation. Our data reveal carbonyl-nucleobase adducts as MR1T cell antigens. Recognizing cells under carbonyl stress allows MR1T cells to monitor cellular metabolic changes with physiological and therapeutic implications.

Surface protein and functional analyses identify CD4+CD39+ TCR αß+ and activated TCR Vδ1+ cells with distinct pro-inflammatory functions in Crohn's disease lesions.

Crohn's disease (CD) is a chronic immune-mediated disorder of the gastrointestinal tract. Extensive screening studies have revealed the accumulation of immune cell subsets with unique plasticity and immunoregulatory properties in patients with CD. We performed phenotypic and functional studies on inflamed and non-inflamed bioptic tissue to investigate the presence of distinct T cells in the intestinal mucosa of CD patients. We analysed hundreds of surface molecules expressed on cells isolated from the intestinal tissue of CD patients using anti-CD45 mAbs-based barcoding. A gene ontology enrichment analysis showed that proteins that regulate the activation of T cells were the most enriched group. We, therefore, designed T-cell focused multicolour flow-cytometry panels and performed clustering analysis which revealed an accumulation of activated TEM CD4+CD39+ T cells producing IL-17 and IL-21 and increased frequency of terminally differentiated TCR Vδ1+ cells producing TNF-α and IFN-γ in inflamed tissue of CD patients. The different functional capacities of CD4+ and TCR Vδ1+ cells in CD lesions indicate their non-overlapping contribution to inflammation. The abnormally high number of terminally differentiated TCR Vδ1+ cells suggests that they are continuously activated in inflamed tissue, making them a potential target for novel therapies.

Promiscuous recognition of MR1 drives self-reactive mucosal-associated invariant T cell responses.

Mucosal-associated invariant T (MAIT) cells use canonical semi-invariant T cell receptors (TCR) to recognize microbial riboflavin precursors displayed by the antigen-presenting molecule MR1. The extent of MAIT TCR crossreactivity toward physiological, microbially unrelated antigens remains underexplored. We describe MAIT TCRs endowed with MR1-dependent reactivity to tumor and healthy cells in the absence of microbial metabolites. MAIT cells bearing TCRs crossreactive toward self are rare but commonly found within healthy donors and display T-helper-like functions in vitro. Experiments with MR1-tetramers loaded with distinct ligands revealed significant crossreactivity among MAIT TCRs both ex vivo and upon in vitro expansion. A canonical MAIT TCR was selected on the basis of extremely promiscuous MR1 recognition. Structural and molecular dynamic analyses associated promiscuity to unique TCRß-chain features that were enriched within self-reactive MAIT cells of healthy individuals. Thus, self-reactive recognition of MR1 represents a functionally relevant indication of MAIT TCR crossreactivity, suggesting a potentially broader role of MAIT cells in immune homeostasis and diseases, beyond microbial immunosurveillance.

Kaposi's sarcoma in people living with HIV/aids in a public referral hospital in Peru. / Sarcoma de Kaposi en personas que viven con VIH-SIDA en un hospital público de referencia en Perú.

Kaposi's sarcoma (KS) is the most frequent cancer in people living with HIV. Research on this condition is scarce in the region, therefore, this article aimed to describe the demographic, clinical and therapeutic characteristics of patients with HIV who developed KS at the Cayetano Heredia Hospital between 2000 and 2018. A total of 129 KS cases were identified, with a median age of 33 years, predominantly males with 92% (119/129), and mostly men who have sex with men (MSM). The median time from HIV diagnosis to KS diagnosis was five months, associated with a CD4 lymphocyte count of 64 cells/µL (IQR: 33-185) at KS diagnosis. Cutaneous involvement was the most common presentation; however, at least half also had the visceral form.

El sarcoma de Kaposi (SK) es el cáncer más frecuente en las personas que viven con VIH. Las investigaciones sobre esta condición son escasas en la región, por lo que, el objetivo de este artículo fue describir las características demográficas, clínicas y terapéuticas de los pacientes con VIH que desarrollaron SK en el Hospital Cayetano Heredia entre el 2000 y 2018. Se identificaron 129 casos de SK, con una mediana de edad de 33 años, con predominio en varones con el 92% (119/129), y en su mayoría hombres que tienen sexo con hombres (HSH). La mediana de tiempo desde el diagnóstico de VIH hasta el del SK fue de cinco meses, asociado con un recuento de linfocitos CD4 de 64 células/µL (RIC: 33-185) al momento del diagnóstico de SK. El compromiso cutáneo fue el más común; sin embargo, al menos la mitad de ellos también tuvo la forma visceral.

Sarcoma de Kaposi en personas que viven con VIH-SIDA en un hospital público de referencia en Perú / Kaposi's sarcoma in people living with HIV/aids in a public referral hospital in Peru

RESUMEN El sarcoma de Kaposi (SK) es el cáncer más frecuente en las personas que viven con VIH. Las investigaciones sobre esta condición son escasas en la región, por lo que, el objetivo de este artículo fue describir las características demográficas, clínicas y terapéuticas de los pacientes con VIH que desarrollaron SK en el Hospital Cayetano Heredia entre el 2000 y 2018. Se identificaron 129 casos de SK, con una mediana de edad de 33 años, con predominio en varones con el 92% (119/129), y en su mayoría hombres que tienen sexo con hombres (HSH). La mediana de tiempo desde el diagnóstico de VIH hasta el del SK fue de cinco meses, asociado con un recuento de linfocitos CD4 de 64 células/µL (RIC: 33-185) al momento del diagnóstico de SK. El compromiso cutáneo fue el más común; sin embargo, al menos la mitad de ellos también tuvo la forma visceral.

ABSTRACT Kaposi's sarcoma (KS) is the most frequent cancer in people living with HIV. Research on this condition is scarce in the region, therefore, this article aimed to describe the demographic, clinical and therapeutic characteristics of patients with HIV who developed KS at the Cayetano Heredia Hospital between 2000 and 2018. A total of 129 KS cases were identified, with a median age of 33 years, predominantly males with 92% (119/129), and mostly men who have sex with men (MSM). The median time from HIV diagnosis to KS diagnosis was five months, associated with a CD4 lymphocyte count of 64 cells/μL (IQR: 33-185) at KS diagnosis. Cutaneous involvement was the most common presentation; however, at least half also had the visceral form.

Cancer in people living with HIV-AIDS at a referral hospital in Lima, Peru. / Cáncer en personas que viven con VIH-SIDA en un hospital público de referencia en Perú.

This study was carried out to describe and compare the demographic, clinical, and therapeutic characteristics of HIV patients who developed some cancer. We identified 276 cancer cases diagnosed at Hospital Cayetano Heredia between 2000 and 2018. 80,8% (223/276) had AIDS-defining-cancers (ADCs), being Kaposi's Sarcoma the most frequent type; meanwhile, among non-AIDS-defining-cancers (NADCs), the most frequent was Hodgkin lymphoma. The median age was 36,5 years, being highest among the cases diagnosed with NADCs. Concerning CD4 lymphocyte counts, the median among ADCs was much lower than NADCs, 87,5 cells/µl and 216 cells/µl, respectively. Therefore, NADCs cases have a longer history of HIV infection, and an older age at cancer diagnosis, as well as higher CD4 cells counts.

El objetivo del estudio fue describir las características demográficas, clínicas y terapéuticas de pacientes con VIH-SIDA que desarrollaron algún tipo de cáncer. Se identificaron 276 casos de cáncer diagnosticados en el Hospital Nacional Cayetano Heredia entre el 2000 y 2018. El 80,8% (223/276) correspondieron a neoplasias definitorias de sida (NDS), siendo el más frecuente el sarcoma de Kaposi; mientras que, entre las neoplasias no definitorias de sida (NNDS), el más frecuente fue el linfoma de Hodgkin. La mediana de edad fue 36,5 años, siendo más alta entre los casos diagnosticados de NNDS. Con respecto al nivel de linfocitos CD4 al diagnóstico de cáncer, la mediana entre las NDS fue mucho menor que las NNDS, 87,5 células/µL y 216 células/µL, respectivamente. Por tanto, las NNDS tuvieron una historia más larga de infección por VIH, y una edad más avanzada al diagnóstico de cáncer, así como niveles de células CD4 más altos.

Human T cells engineered with a leukemia lipid-specific TCR enables donor-unrestricted recognition of CD1c-expressing leukemia.

Acute leukemia relapsing after chemotherapy plus allogeneic hematopoietic stem cell transplantation can be treated with donor-derived T cells, but this is hampered by the need for donor/recipient MHC-matching and often results in graft-versus-host disease, prompting the search for new donor-unrestricted strategies targeting malignant cells. Leukemia blasts express CD1c antigen-presenting molecules, which are identical in all individuals and expressed only by mature leukocytes, and are recognized by T cell clones specific for the CD1c-restricted leukemia-associated methyl-lysophosphatidic acid (mLPA) lipid antigen. Here, we show that human T cells engineered to express an mLPA-specific TCR, target diverse CD1c-expressing leukemia blasts in vitro and significantly delay the progression of three models of leukemia xenograft in NSG mice, an effect that is boosted by mLPA-cellular immunization. These results highlight a strategy to redirect T cells against leukemia via transfer of a lipid-specific TCR that could be used across MHC barriers with reduced risk of graft-versus-host disease.

Antigen specificities and functional properties of MR1-restricted T cells.

MR1 is an MHC class I-like molecule with unique structural and biological features that make it an important member among the molecules involved in antigen presentation to T cells. Distinctive features include ubiquitous expression of the MR1 gene and its monomorphism. Another relevant property is that the MR1 protein appears at very low levels on the plasma membrane and its surface expression is regulated by antigen binding. Finally, the nature of presented antigens differs from those that bind other presenting molecules and includes small metabolites of microbial and self-origin, small drugs and tumor-associated antigens. This opinion paper describes in detail some of those features and discusses recent literature in the field.

Cáncer en personas que viven con VIH-SIDA en un hospital público de referencia en Perú

El objetivo del estudio fue describir las características demográficas, clínicas y terapéuticas de pacientes con VIH-SIDA que desarrollaron algún tipo de cáncer. Se identificaron 276 casos de cáncer diagnosticados en el Hospital Nacional Cayetano Heredia entre el 2000 y 2018. El 80,8% (223/276) correspondieron a neoplasias definitorias de sida (NDS), siendo el más frecuente el sarcoma de Kaposi; mientras que, entre las neoplasias no definitorias de sida (NNDS), el más frecuente fue el linfoma de Hodgkin. La mediana de edad fue 36,5 años, siendo más alta entre los casos diagnosticados de NNDS. Con respecto al nivel de linfocitos CD4 al diagnóstico de cáncer, la mediana entre las NDS fue mucho menor que las NNDS, 87,5 células/µL y 216 células/µL, respectivamente. Por tanto, las NNDS tuvieron una historia más larga de infección por VIH, y una edad más avanzada al diagnóstico de cáncer, así como niveles de células CD4 más altos.

This study was carried out to describe and compare the demographic, clinical, and therapeutic characteristics of HIV patients who developed some cancer. We identified 276 cancer cases diagnosed at Hospital Cayetano Heredia between 2000 and 2018. 80,8% (223/276) had AIDS-defining-cancers (ADCs), being Kaposi's Sarcoma the most frequent type; meanwhile, among non-AIDS-defining-cancers (NADCs), the most frequent was Hodgkin lymphoma. The median age was 36,5 years, being highest among the cases diagnosed with NADCs. Concerning CD4 lymphocyte counts, the median among ADCs was much lower than NADCs, 87,5 cells/µl and 216 cells/µl, respectively. Therefore, NADCs cases have a longer history of HIV infection, and an older age at cancer diagnosis, as well as higher CD4 cells counts.

MR1-Restricted T Cells Are Unprecedented Cancer Fighters.

Non-polymorphic MHC class I-related molecule MR1 presents antigenic bacterial metabolites to mucosal-associated invariant T (MAIT) cells and self-antigens to MR1-restricted T (MR1T) cells. Both MR1-restricted T cell populations are readily identified in healthy individuals, with MAIT cells accounting for 1-10% of circulating T cells, while MR1T cells have frequencies comparable to peptide-specific T cells (<0.1%). Self-reactive MR1T cells display a heterogeneous phenotype, and are capable of releasing both TH1 and TH2 cytokines, supporting not only activation of inflammation but also contributing to its regulation. Importantly, MR1T cells recognize and kill a diverse range of MR1-expressing tumor cells. On the other hand, evidence suggests MAIT cells augment cancer growth and metastases. This review addresses the potential role of MR1-restricted T cells in controlling tumor cells, facilitating their elimination and regulating cancer immunity. We also discuss therapeutic opportunities surrounding MR1-restricted T cells in cancer.

Unique T-Cell Populations Define Immune-Inflamed Hepatocellular Carcinoma.

BACKGROUND & AIMS: The characterization of T cells infiltrating hepatocellular carcinoma (HCC) provides information on cancer immunity and also on selection of patients with precise indication of immunotherapy. The aim of the study was to characterize T-cell populations within tumor tissue and compare them with non-neoplastic liver tissue as well as circulating cells of the same patients. METHODS: The presence of unique cell populations was investigated in 36 HCC patients by multidimensional flow cytometry followed by t-distributed stochastic neighbor embedding analysis. Functional activity of tumor-infiltrating T cells was determined after activation by phorbol 12-myristate 13-acetate and ionomycin. RESULTS: Within the tumor there were more cells expressing CD137 and ICOS than in non-neoplastic liver tissue, possibly after recent antigenic activation. These cells contained several populations, including the following: (1) functionally impaired, proliferating CD4+ cells co-expressing Inducible T-cell costimulator (ICOS) and T cell immunoreceptor with Ig and ITIM domains (TIGIT); (2) functionally active CD8+ cells co-expressing CD38 and Programmed cell-death protein 1 (PD1); and (3) CD4-CD8 double-negative T-cell receptor αß and γδ cells (both non-major histocompatibility complex-restricted T cells). When the identified clusters were compared with histologic classification performed on the same samples, an accumulation of activated T cells was observed in immune-inflamed HCC. The same analyses performed in 7 patients receiving nivolumab treatment showed a remarkable reduction in the functionally impaired CD4+ cells, which returned to almost normal activity over time. CONCLUSIONS: Unique populations of activated T cells are present in HCC tissue, whose antigen specificity remains to be investigated. Some of these cell populations are functionally impaired and nivolumab treatment restores their responsiveness. The finding of ongoing immune response within the tumor shows which lymphocyte populations are impaired within the HCC and identifies the patients who might take benefit from immunotherapy.

Isolation and Characterization of MAIT Cells from Human Tissue Biopsies.

Human mucosal-associated invariant T (MAIT) cells are unconventional T cells highly enriched in tissues exposed to microbial antigens including the oral, gastrointestinal and genital mucosae, liver, and lung. Here we describe a protocol for isolation and characterization of peripheral blood and tissue-infiltrating MAIT cells by using multicolor flow cytometry. This technology allows the analysis of multiple markers in a single sample at a single-cell level. Study of human samples requires particular care since the sample amount is often limited. We present a protocol optimized for the isolation and characterization of human MAIT cells and the identification of MAIT cell populations detected by simultaneous expression of multiple activation markers and inhibitory receptors.

The Conventional Nature of Non-MHC-Restricted T Cells.

The definition "unconventional T cells" identifies T lymphocytes that recognize non-peptide antigens presented by monomorphic antigen-presenting molecules. Two cell populations recognize lipid antigens and small metabolites presented by CD1 and MR1 molecules, respectively. A third cell population expressing the TCR Vγ9Vδ2 is stimulated by small phosphorylated metabolites. In the recent past, we have learnt a lot about the selection, tissue distribution, gene transcription programs, mode of expansion after antigen recognition, and persistence of these cells. These studies depict their functions in immune homeostasis and diseases. Current investigations are revealing that unconventional T cells include distinct sub-populations, which display unexpected similarities to classical MHC-restricted T cells in terms of TCR repertoire diversity, antigen specificity variety, functional heterogeneity, and naïve-to-memory differentiation dynamic. This review discusses the latest findings with a particular emphasis on these T cells, which appear to be more conventional than previously appreciated, and with the perspective of using CD1 and MR1-restricted T cells in vaccination and immunotherapy.

Modulation of bacterial metabolism by the microenvironment controls MAIT cell stimulation.

Mucosal-associated invariant T (MAIT) cells are abundant innate-like T lymphocytes in mucosal tissues and recognize a variety of riboflavin-related metabolites produced by the microbial flora. Relevant issues are whether MAIT cells are heterogeneous in the colon, and whether the local environment influences microbial metabolism thereby shaping MAIT cell phenotypes and responses. We found discrete MAIT cell populations in human colon, characterized by the diverse expression of transcription factors, cytokines and surface markers, indicative of activated and precisely controlled lymphocyte populations. Similar phenotypes were rare among circulating MAIT cells and appeared when circulating MAIT cells were stimulated with the synthetic antigens 5-(2-oxoethylideneamino)-6-D-ribitylaminouracil, and 5-(2-oxopropylideneamino)-6-D-ribitylaminouracil. Furthermore, bacteria grown in colon-resembling conditions with low oxygen tension and harvested at stationary growth phase, potently activated human MAIT cells. The increased activation correlated with accumulation of the above antigenic metabolites as indicated by mass spectrometry. Thus, the colon environment contributes to mucosal immunity by directly affecting bacterial metabolism, and indirectly controlling the stimulation and differentiation of MAIT cells.

Functionally diverse human T cells recognize non-microbial antigens presented by MR1.

MHC class I-related molecule MR1 presents riboflavin- and folate-related metabolites to mucosal-associated invariant T cells, but it is unknown whether MR1 can present alternative antigens to other T cell lineages. In healthy individuals we identified MR1-restricted T cells (named MR1T cells) displaying diverse TCRs and reacting to MR1-expressing cells in the absence of microbial ligands. Analysis of MR1T cell clones revealed specificity for distinct cell-derived antigens and alternative transcriptional strategies for metabolic programming, cell cycle control and functional polarization following antigen stimulation. Phenotypic and functional characterization of MR1T cell clones showed multiple chemokine receptor expression profiles and secretion of diverse effector molecules, suggesting functional heterogeneity. Accordingly, MR1T cells exhibited distinct T helper-like capacities upon MR1-dependent recognition of target cells expressing physiological levels of surface MR1. These data extend the role of MR1 beyond microbial antigen presentation and indicate MR1T cells are a normal part of the human T cell repertoire.

Contact sensitizers trigger human CD1-autoreactive T-cell responses.

Allergic contact dermatitis is a primarily T-cell-mediated inflammatory skin disease induced by exposure to small molecular-weight haptens, which covalently bind to proteins. The abundance of cutaneous T cells that recognize CD1a antigen-presenting molecules raises the possibility that MHC-independent antigen presentation may be relevant in some hapten-driven immune responses. Here we examine the ability of contact sensitizers to influence CD1-restricted immunity. Exposure of human antigen-presenting cells such as monocyte-derived dendritic cells and THP-1 cells to the prototypical contact sensitizer dinitrochlorobenzene potentiated the response of CD1a- and CD1d-autoreactive T cells, which released a vast array of cytokines in a CD1- and TCR-dependent manner. The potentiating effects of dinitrochlorobenzene depended upon newly synthesized CD1 molecules and the presence of endogenous stimulatory lipids. Further examination of a broad panel of contact sensitizers revealed 1,4-benzoquinone, resorcinol, isoeugenol, and cinnamaldehyde to activate the same type of CD1-restricted responses. These findings provide a basis for the antigen-specific activation of skin-associated CD1-restricted T cells by small molecules and may have implications for contact sensitizer-induced inflammatory skin diseases.

Lysosomal Lipases PLRP2 and LPLA2 Process Mycobacterial Multi-acylated Lipids and Generate T Cell Stimulatory Antigens.

Complex antigens require processing within antigen-presenting cells (APCs) to form T cell stimulatory complexes with CD1 antigen-presenting molecules. It remains unknown whether lipids with multi-acylated moieties also necessitate digestion by lipases to become capable of binding CD1 molecules and stimulate T cells. Here, we show that the mycobacterial tetra-acylated glycolipid antigens phosphatidyl-myo-inositol mannosides (PIM) are digested to di-acylated forms by pancreatic lipase-related protein 2 (PLRP2) and lysosomal phospholipase A2 (LPLA2) within APCs. Recombinant PLRP2 and LPLA2 removed the sn1- and sn2-bound fatty acids from the PIM glycerol moiety, as revealed by mass spectrometry and nuclear magnetic resonance studies. PLRP2 or LPLA2 gene silencing in APCs abolished PIM presentation to T cells, thus revealing an essential role of both lipases in vivo. These findings show that endosomal lipases participate in lipid antigen presentation by processing lipid antigens and have a role in T cell immunity against mycobacteria.