CD161-Expressing Human T Cells

Expression of the Natural Killer cell receptor CD161 has recently been identified on a subset of T cells, including both CD4+ T helper and CD8+ T cells. Expression of this molecule within the adult circulation is restricted to those T cells with a memory phenotype. However, the distinct properties of these T cell populations is yet to be fully determined, although expression of CD161 has been related to the secretion of interleukin-17, and therefore to a type 17 phenotype. Recent studies have aimed to determine both the origin of these cells and the significance of CD161 expression as either a marker of specific cell types or as an effector and regulator of lymphocyte function, and hence to characterize the role of these CD161+ cells within a variety of human diseases in which they have been implicated

Emulsion and liposome-based adjuvanted R21 vaccine formulations mediate protection against malaria through distinct immune mechanisms

Adjuvanted protein vaccines offer high efficacy, yet most potent adjuvants remain proprietary. Several adjuvant compounds are being developed by the Vaccine Formulation Institute in Switzerland for global open access clinical use. In the context of the R21 malaria vaccine, in a mouse challenge model, we characterize the efficacy and mechanism of action of four Vaccine Formulation Institute adjuvants: two liposomal (LQ and LMQ) and two squalene emulsion-based adjuvants (SQ and SMQ), containing QS-21 saponin (Q) and optionally a synthetic TLR4 agonist (M). Two R21 vaccine formulations, R21/LMQ and R21/SQ, offer the highest protection (81%–100%), yet they trigger different innate sensing mechanisms in macrophages with LMQ, but not SQ, activating the NLRP3 inflammasome. The resulting in vivo adaptive responses have a different TH1/TH2 balance and engage divergent innate pathways while retaining high protective efficacy. We describe how modular changes in vaccine formulation allow for the dissection of the underlying immune pathways, enabling future mechanistically informed vaccine design

Early and nonreversible decrease of CD161++ /MAIT cells in HIV infection

HIV infection is associated with immune dysfunction, perturbation of immune-cell subsets and opportunistic infections. CD161++ CD8+ T cells are a tissue-infiltrating population that produce IL17A, IL22, IFN, and TNFα, cytokines important in mucosal immunity. In adults they dominantly express the semi-invariant TCR Vα7.2, the canonical feature of mucosal associated invariant T (MAIT) cells and have been recently implicated in host defense against pathogens. We analyzed the frequency and function of CD161++ /MAIT cells in peripheral blood and tissue from patients with early stage or chronic-stage HIV infection. We show that the CD161++ /MAIT cell population is significantly decreased in early HIV infection and fails to recover despite otherwise successful treatment. We provide evidence that CD161++ /MAIT cells are not preferentially infected but may be depleted through diverse mechanisms including accumulation in tissues and activation-induced cell death. This loss may impact mucosal defense and could be important in susceptibility to specific opportunistic infections in HIV

Maturing Human CD127+ CCR7+ PDL1+ Dendritic Cells Express AIRE in the Absence of Tissue Restricted Antigens.

Expression of the Autoimmune regulator (AIRE) outside of the thymus has long been suggested in both humans and mice, but the cellular source in humans has remained undefined. Here we identify AIRE expression in human tonsils and extensively analyzed these "extra-thymic AIRE expressing cells" (eTACs) using combinations of flow cytometry, CyTOF and single cell RNA-sequencing. We identified AIRE+ cells as dendritic cells (DCs) with a mature and migratory phenotype including high levels of antigen presenting molecules and costimulatory molecules, and specific expression of CD127, CCR7, and PDL1. These cells also possessed the ability to stimulate and re-stimulate T cells and displayed reduced responses to toll-like receptor (TLR) agonists compared to conventional DCs. While expression of AIRE was enriched within CCR7+CD127+ DCs, single-cell RNA sequencing revealed expression of AIRE to be transient, rather than stable, and associated with the differentiation to a mature phenotype. The role of AIRE in central tolerance induction within the thymus is well-established, however our study shows that AIRE expression within the periphery is not associated with an enriched expression of tissue-restricted antigens (TRAs). This unexpected finding, suggestive of wider functions of AIRE, may provide an explanation for the non-autoimmune symptoms of APECED patients who lack functional AIRE.JF and HS were funded by project ERC-2013-ADG number 341038. MB was funded by EMBO ALTF 786-2013. BH was supported by the Netherlands Organization for Scientific Research (NWO) Veni program (91618032). LH, JpvH, and ST were supported by a grant from the Dutch Arthritis Foundation (2013_2_37). MM was supported by Wellcome Trust (grant105045/Z/14/Z). JM was supported by core funding from the European Molecular Biology Laboratory and from Cancer Research UK (award number 17197)

An HLA-E-targeted TCR bispecific molecule redirects T cell immunity against Mycobacterium tuberculosis

Peptides presented by HLA - E, a molecule with very limited polymorphism, represent attractive targets for T cell receptor (TCR) - based immunotherapies to circumvent the limitations imposed by the high polymorphism of classical HLA genes in the human population. Here, we describe a TCR - based bispecific molecule that potently and selectively binds HLA - E in complex with a peptide encoded by the inhA gene of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis in humans. We reveal the biophysical and structural bases underpinning the potency and specificity of this molecule and demonstrate its ability to redirect polyclonal T cells to target HLA - E - expressing cells transduced with mycobacterial inhA as well as primary cells infected with virulent Mtb. Additionally, we demonstrate elimination of Mtb - infected cells and reduction of intracellular Mtb growth. Our study suggests an approach to enhance host T cell immunity against Mtb and provides proof of principle for an innovative TCR - based therapeutic strategy overcoming HLA polymorphism and therefore applicable to a broader patient population

Maturing Human CD127+ CCR7+ PDL1+ Dendritic Cells Express AIRE in the Absence of Tissue Restricted Antigens

Expression of the Autoimmune regulator (AIRE) outside of the thymus has long been suggested in both humans and mice, but the cellular source in humans has remained undefined. Here we identify AIRE expression in human tonsils and extensively analyzed these “extra-thymic AIRE expressing cells” (eTACs) using combinations of flow cytometry, CyTOF and single cell RNA-sequencing. We identified AIRE+ cells as dendritic cells (DCs) with a mature and migratory phenotype including high levels of antigen presenting molecules and costimulatory molecules, and specific expression of CD127, CCR7, and PDL1. These cells also possessed the ability to stimulate and re-stimulate T cells and displayed reduced responses to toll-like receptor (TLR) agonists compared to conventional DCs. While expression of AIRE was enriched within CCR7+CD127+ DCs, single-cell RNA sequencing revealed expression of AIRE to be transient, rather than stable, and associated with the differentiation to a mature phenotype. The role of AIRE in central tolerance induction within the thymus is well-established, however our study shows that AIRE expression within the periphery is not associated with an enriched expression of tissue-restricted antigens (TRAs). This unexpected finding, suggestive of wider functions of AIRE, may provide an explanation for the non-autoimmune symptoms of APECED patients who lack functional AIRE

Mucosal associated invariant T cells and related CD161 expressing T lymphocytes

The C-type lectin CD161 is expressed by a large number of T lymphocytes, with approximately a quarter of both T cell receptor (TCR)αβ+ and TCRγδ+ T cells expressing this marker. Within CD8+ T cells, a large proportion of these are comprised of Mucosal Associated Invariant T (MAIT) cells, a novel innate-like lymphocyte subset characterised by expression of a semi-invariant TCR together with high levels of CD161 (CD161++). These cells display a phenotype reflective of type 17 CD4+ helper T cells (Th17), which are also hallmarked by CD161 expression. Both MAIT and Th17 cells arise from preprogrammed progenitors, identifiable within umbilical cord blood by expression of CD161. Thus, CD161 appears to identify cells of a pre-determined and distinct phenotype. Whether this reflects a common transcriptional programme, developmentally induced within these cells, and further whether this extends to other CD161 positive T cells, was examined here by mRNA microarray analysis. This analysis identified a shared transcriptional signature and common innate-like function of all CD161 expressing T lymphocytes, and independent of TCR expression or lineage. Furthermore, a population of CD8+ T lymphocytes expressing lower levels of CD161 which overlap phenotypically with CD161++CD8+ MAIT cells was identified by both mRNA microarray analysis and mass cytometry (CyTOF); the CD161+CD8+ T cell population. TCR repertoire analysis, flow cytometry and cell culture experiments were utilised to investigate the origin of this subset, and its phenotype and function in both health and disease investigated in depth. This revealed a pre-programmed, tissue-resident memory population with potent effector functions. Both CD161++ MAIT and CD161+CD8+ T cells expressed high levels of the drug efflux pump MDR1, previously described to confer drug resistance to certain malignant cells. The significance of expression of this pump was hence investigated to determine its potential affect on the success of a variety of clinical therapies.</p

Mucosal associated invariant T cells and related CD161 expressing T lymphocytes

The C-type lectin CD161 is expressed by a large number of T lymphocytes, with approximately a quarter of both T cell receptor (TCR)&alpha;&beta;+ and TCR&gamma;&delta;+ T cells expressing this marker. Within CD8+ T cells, a large proportion of these are comprised of Mucosal Associated Invariant T (MAIT) cells, a novel innate-like lymphocyte subset characterised by expression of a semi-invariant TCR together with high levels of CD161 (CD161++). These cells display a phenotype reflective of type 17 CD4+ helper T cells (Th17), which are also hallmarked by CD161 expression. Both MAIT and Th17 cells arise from preprogrammed progenitors, identifiable within umbilical cord blood by expression of CD161. Thus, CD161 appears to identify cells of a pre-determined and distinct phenotype. Whether this reflects a common transcriptional programme, developmentally induced within these cells, and further whether this extends to other CD161 positive T cells, was examined here by mRNA microarray analysis. This analysis identified a shared transcriptional signature and common innate-like function of all CD161 expressing T lymphocytes, and independent of TCR expression or lineage. Furthermore, a population of CD8+ T lymphocytes expressing lower levels of CD161 which overlap phenotypically with CD161++CD8+ MAIT cells was identified by both mRNA microarray analysis and mass cytometry (CyTOF); the CD161+CD8+ T cell population. TCR repertoire analysis, flow cytometry and cell culture experiments were utilised to investigate the origin of this subset, and its phenotype and function in both health and disease investigated in depth. This revealed a pre-programmed, tissue-resident memory population with potent effector functions. Both CD161++ MAIT and CD161+CD8+ T cells expressed high levels of the drug efflux pump MDR1, previously described to confer drug resistance to certain malignant cells. The significance of expression of this pump was hence investigated to determine its potential affect on the success of a variety of clinical therapies.This thesis is not currently available on ORA