Although mutations may represent attractive targets for immunotherapy, direct identification of mutated peptide ligands isolated from human leucocyte antigens (HLA) on the surface of native tumour ...tissue has so far not been successful. Using advanced mass spectrometry (MS) analysis, we survey the melanoma-associated immunopeptidome to a depth of 95,500 patient-presented peptides. We thereby discover a large spectrum of attractive target antigen candidates including cancer testis antigens and phosphopeptides. Most importantly, we identify peptide ligands presented on native tumour tissue samples harbouring somatic mutations. Four of eleven mutated ligands prove to be immunogenic by neoantigen-specific T-cell responses. Moreover, tumour-reactive T cells with specificity for selected neoantigens identified by MS are detected in the patient's tumour and peripheral blood. We conclude that direct identification of mutated peptide ligands from primary tumour material by MS is possible and yields true neoepitopes with high relevance for immunotherapeutic strategies in cancer.
Maintenance of immunological memory has been proposed to rely on stem-cell-like lymphocytes. However, data supporting this hypothesis are focused on the developmental potential of lymphocyte ...populations and are thus insufficient to establish the functional hallmarks of stemness. Here, we investigated self-renewal capacity and multipotency of individual memory lymphocytes by in vivo fate mapping of CD8+ T cells and their descendants across three generations of serial single-cell adoptive transfer and infection-driven re-expansion. We found that immune responses derived from single naive T (Tn) cells, single primary, and single secondary central memory T (Tcm) cells reached similar size and phenotypic diversity, were subjected to comparable stochastic variation, and could ultimately reconstitute immunocompetence against an otherwise lethal infection with the bacterial pathogen Listeria monocytogenes. These observations establish that adult tissue stem cells reside within the CD62L+ Tcm cell compartment and highlight the promising therapeutic potential of this immune cell subset.
•Individual Tcm cells are multipotent to generate diverse effector and memory subsets•Individual primary Tcm cells can self-renew into multipotent secondary Tcm cells•Responses derived from single Tcm cells show nonheritable stochastic variation•Single secondary Tcm cells can provide full reconstitution of immunocompetence
Long-term persistence of adaptive immunity is suggested to rely on stem-cell-based mechanisms. Graef et al. show that upon serial single-cell transfers, propagation of protective T cell memory can be established by individual central memory T cells acting as self-renewing, multipotent tissue stem cells.
Recognition of cell death by the innate immune system triggers inflammatory responses. However, how these reactions are regulated is not well understood. Here, we identify the inhibitory C-type ...lectin receptor Clec12a as a specific receptor for dead cells. Both human and mouse Clec12a could physically sense uric acid crystals (monosodium urate, MSU), which are key danger signals for cell-death-induced immunity. Clec12a inhibited inflammatory responses to MSU in vitro, and Clec12a-deficient mice exhibited hyperinflammatory responses after being challenged with MSU or necrotic cells and after radiation-induced thymocyte killing in vivo. Thus, we identified a negative regulatory MSU receptor that controls noninfectious inflammation in response to cell death that has implications for autoimmunity and inflammatory disease.
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•Clec12a is a receptor for dead cells•Uric acid crystals (MSU) are ligands for Clec12a•Clec12a limits the MSU-induced respiratory burst•Clec12a-deficient mice exhibit hyperinflammatory responses in vivo
Efficient clearance of bacteremia prevents life-threatening disease. Platelet binding to intravascular bacteria, a process involving platelet glycoprotein GPIb and bacterial opsonization with ...activated complement C3, influences blood clearance and anti-infective immunity. Using intravital microscopy of the bloodstream of mice infected with Listeria monocytogenes, we show that bacterial clearance is not a uniform process but a “dual-track” mechanism consisting of parallel “fast” and “slow” pathways. “Slow clearance” is regulated by time-dependent bacterial opsonization, stochastic platelet binding, and capture of bacteria-platelet-complexes via the complement receptor of the immunoglobulin superfamily, CRIg. The mechanism spares some bacteria from “fast clearance” and rapid destruction in the liver via Kupffer cell scavenger receptors, keeping them available for adaptive immunity induction by splenic CD8α+ dendritic cells. We consistently find “fast” and “slow” clearance patterns for a broad panel of other Gram+ and Gram− bacteria. Thus, dual-track clearance balances rapid restoration of blood sterility with induction of specific antibacterial immunity.
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•Platelet-bound and free L. monocytogenes clear from circulation with distinct kinetics•Liver macrophages mediate “fast clearance” of intravascular LM via scavenger receptors•Platelet binding shifts LM from “fast” into CRIg-dependent “slow” clearance pathways•“Dual-track clearance” balances innate and adaptive immunity during bacteremia
Broadley et al. report that overall clearance of intravascular bacteria is the cumulative result of two parallel and kinetically distinct pathways. Platelet binding shifts blood-borne bacteria from “fast clearance” via scavenger receptors toward CRIg-dependent “slow clearance.” Consequently, “dual-track” clearance balances rapid restoration of blood sterility with induction of specific antibacterial immunity.
Since the first bone marrow transplantation, adoptive T cell therapy (ACT) has developed over the last 80 years to a highly efficient and specific therapy for infections and cancer. Genetic ...engineering of T cells with antigen-specific receptors now provides the possibility of generating highly defined and efficacious T cell products. The high sensitivity of engineered T cells towards their targets, however, also bears the risk of severe off-target toxicities. Therefore, different safety strategies for engineered T cells have been developed that enable removal of the transferred cells in case of adverse events, control of T cell activity or improvement of target selectivity. Receptor avidity is a crucial component in the balance between safety and efficacy of T cell products. In clinical trials, T cells equipped with high avidity T cell receptor (TCR)/chimeric antigen receptor (CAR) have been mostly used so far because of their faster and better response to antigen recognition. However, over-activation can trigger T cell exhaustion/death as well as side effects due to excessive cytokine production. Low avidity T cells, on the other hand, are less susceptible to over-activation and could possess better selectivity in case of tumor antigens shared with healthy tissues, but complete tumor eradication may not be guaranteed. In this review we describe how ‘optimal’ TCR/CAR affinity can increase the safety/efficacy balance of engineered T cells, and discuss simultaneous or sequential infusion of high and low avidity receptors as further options for efficacious but safe T cell therapy.
Dietary restriction regimes extend lifespan in various animal models. Here we show that longevity in male C57BL/6J mice subjected to every-other-day feeding is associated with a delayed onset of ...neoplastic disease that naturally limits lifespan in these animals. We compare more than 200 phenotypes in over 20 tissues in aged animals fed with a lifelong every-other-day feeding or ad libitum access to food diet to determine whether molecular, cellular, physiological and histopathological aging features develop more slowly in every-other-day feeding mice than in controls. We also analyze the effects of every-other-day feeding on young mice on shorter-term every-other-day feeding or ad libitum to account for possible aging-independent restriction effects. Our large-scale analysis reveals overall only limited evidence for a retardation of the aging rate in every-other-day feeding mice. The data indicate that every-other-day feeding-induced longevity is sufficiently explained by delays in life-limiting neoplastic disorders and is not associated with a more general slowing of the aging process in mice.Dietary restriction can extend the life of various model organisms. Here, Xie et al. show that intermittent periods of fasting achieved through every-other-day feeding protect mice against neoplastic disease but do not broadly delay organismal aging in animals.
infection is the most prevalent bacterial infection worldwide. Besides being the most important risk factor for gastric cancer development, epidemiological data show that infected individuals harbour ...a nearly twofold increased risk to develop colorectal cancer (CRC). However, a direct causal and functional connection between
infection and colon cancer is lacking.
We infected two
-mutant mouse models and C57BL/6 mice with
and conducted a comprehensive analysis of
-induced changes in intestinal immune responses and epithelial signatures via flow cytometry, chip cytometry, immunohistochemistry and single cell RNA sequencing. Microbial signatures were characterised and evaluated in germ-free mice and via stool transfer experiments.
infection accelerated tumour development in
-mutant mice. We identified a unique
-driven immune alteration signature characterised by a reduction in regulatory T cells and pro-inflammatory T cells. Furthermore, in the intestinal and colonic epithelium,
induced pro-carcinogenic STAT3 signalling and a loss of goblet cells, changes that have been shown to contribute-in combination with pro-inflammatory and mucus degrading microbial signatures-to tumour development. Similar immune and epithelial alterations were found in human colon biopsies from
-infected patients. Housing of
-mutant mice under germ-free conditions ameliorated, and early antibiotic eradication of
infection normalised the tumour incidence to the level of uninfected controls.
Our studies provide evidence that
infection is a strong causal promoter of colorectal carcinogenesis. Therefore, implementation of
status into preventive measures of CRC should be considered.
A core feature of protective T cell responses to infection is the robust expansion and diversification of naïve antigen-specific T cell populations into short-lived effector and long-lived memory ...subsets. By means of in vivo fate mapping, we found a striking variability of immune responses derived from individual CD8⁺ T cells and show that robust acute and recall immunity requires the initial recruitment of multiple precursors. Unbiased mathematical modeling identifies the random integration of multiple differentiation and division events as the driving force behind this variability. Within this probabilistic framework, cell fate is specified along a linear developmental path that progresses from slowly proliferating long-lived to rapidly expanding short-lived subsets. These data provide insights into how complex biological systems implement stochastic processes to guarantee robust outcomes.
Adaptive evolution is a key feature of T cell immunity. During acute immune responses, T cells harboring high-affinity T cell antigen receptors (TCRs) are preferentially expanded, but whether ...affinity maturation by clonal selection continues through the course of chronic infections remains unresolved. Here we investigated the evolution of the TCR repertoire and its affinity during the course of infection with cytomegalovirus, which elicits large T cell populations in humans and mice. Using single-cell and bulk TCR sequencing and structural affinity analyses of cytomegalovirus-specific T cells, and through the generation and in vivo monitoring of defined TCR repertoires, we found that the immunodominance of high-affinity T cell clones declined during the chronic infection phase, likely due to cellular senescence. These data showed that under conditions of chronic antigen exposure, low-affinity TCRs preferentially expanded within the TCR repertoire, with implications for immunotherapeutic strategies.
Herpes simplex virus (HSV) replication can be detected in the respiratory secretions of a high proportion of ventilated intensive care unit (ICU) patients. However, the clinical significance remains ...poorly defined. We investigated whether patients with ventilator-associated pneumonia not responding to antibiotics and in whom high levels of HSV could be detected in respiratory secretions benefit from acyclovir treatment.
Respiratory secretions (bronchoalveolar lavage fluid or tracheal aspirates) were tested for HSV replication by quantitative real-time PCR. ICU survival times, clinical parameters, and radiographic findings were retrospectively compared between untreated and acyclovir treated patients with high (> 10
HSV copies/mL) and low (10
-10
HSV copies/mL) viral load.
Fifty-seven low and 69 high viral load patients were identified. Fewer patients with high viral load responded to antibiotic treatment (12% compared to 40% of low load patients, p = 0.001). Acyclovir improved median ICU survival (8 vs 22 days, p = 0.014) and was associated with a significantly reduced hazard ratio for ICU death (HR = 0.31, 95% CI 0.11-0.92, p = 0.035) in high load patients only. Moreover, circulatory and pulmonary oxygenation function of high load patients improved significantly over the course of acyclovir treatment: mean norepinephrine doses decreased from 0.05 to 0.02 μg/kg body weight/min between days 0 and 6 of treatment (p = 0.049), and median PaO
/FiO
ratio increased from 187 to 241 between day 3 and day 7 of treatment (p = 0.02). Chest radiographic findings also improved significantly (p < 0.001).
In patients with ventilator-associated pneumonia, antibiotic treatment failure, and high levels of HSV replication, acyclovir treatment was associated with a significantly longer time to death in the ICU and improved circulatory and pulmonary function. This suggests a causative role for HSV in this highly selected group of patients.
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