IL-21 is required for CD4 memory formation in response to viral infection

Promising Cytokine Adjuvants for Enhancing Tuberculosis Vaccine Immunity

Tuberculosis, caused by Mycobacterium tuberculosis (M. tuberculosis), remains a formidable global health challenge, affecting a substantial portion of the world's population. The current tuberculosis vaccine, bacille Calmette-Guérin (BCG), offers limited protection against pulmonary tuberculosis in adults, underscoring the critical need for innovative vaccination strategies. Cytokines are pivotal in modulating immune responses and have been explored as potential adjuvants to enhance vaccine efficacy. The strategic inclusion of cytokines as adjuvants in tuberculosis vaccines holds significant promise for augmenting vaccine-induced immune responses and strengthening protection against M. tuberculosis. This review delves into promising cytokines, such as Type I interferons (IFNs), Type II IFN, interleukins such as IL-2, IL-7, IL-15, IL-12, and IL-21, alongside the use of a granulocyte-macrophage colony-stimulating factor (GM-CSF) as an adjuvant, which has shown effectiveness in boosting immune responses and enhancing vaccine efficacy in tuberculosis models.

Spontaneous immunological activities in the target tissue of vitiligo-prone Smyth and vitiligo-susceptible Brown lines of chicken

Introduction

Vitiligo is an acquired de-pigmentation disorder characterized by the post-natal loss of epidermal melanocytes (pigment-producing cells) resulting in the appearance of white patches in the skin. The Smyth chicken is the only model for vitiligo that shares all the characteristics of the human condition including: spontaneous post-natal loss of epidermal melanocytes, interactions between genetic, environmental and immunological factors, and associations with other autoimmune diseases. In addition, an avian model for vitiligo has the added benefit of an easily accessible target tissue (a growing feather) that allows for the repeated sampling of an individual and thus the continuous monitoring of local immune responses over time.

Methods

Using a combination of flow cytometry and gene expression analyses, we sought to gain a comprehensive understanding of the initiating events leading to expression of vitiligo in growing feathers by monitoring the infiltration of leukocytes and concurrent immunological activities in the target tissue beginning prior to visual onset and continuing throughout disease development.

Results

Here, we document a sequence of immunologically significant events, including characteristic rises in infiltrating B and αβ T cells as well as evidence of active leukocyte recruitment and cell-mediated immune activities (CCL19, IFNG, GZMA) leading up to visual vitiligo onset. Examination of growing feathers from vitiligo-susceptible Brown line chickens revealed anti-inflammatory immune activities which may be responsible for preventing vitiligo (IL10, CTLA4, FOXP3). Furthermore, we detected positive correlations between infiltrating T cells and changes in their T cell receptor diversity supporting a T cell-specific immune response.

Conclusion

Collectively, these results further support the notion of cell-mediated immune destruction of epidermal melanocytes in the pulp of growing feathers and open new avenues of study in the vitiligo-prone Smyth and vitiligo-susceptible Brown line chickens.

Phenotypic signatures of immune selection in HIV-1 reservoir cells

Human immunodeficiency virus 1 (HIV-1) reservoir cells persist lifelong despite antiretroviral treatment1,2 but may be vulnerable to host immune responses that could be exploited in strategies to cure HIV-1. Here we used a single-cell, next-generation sequencing approach for the direct ex vivo phenotypic profiling of individual HIV-1-infected memory CD4+ T cells from peripheral blood and lymph nodes of people living with HIV-1 and receiving antiretroviral treatment for approximately 10 years. We demonstrate that in peripheral blood, cells harbouring genome-intact proviruses and large clones of virally infected cells frequently express ensemble signatures of surface markers conferring increased resistance to immune-mediated killing by cytotoxic T and natural killer cells, paired with elevated levels of expression of immune checkpoint markers likely to limit proviral gene transcription; this phenotypic profile might reduce HIV-1 reservoir cell exposure to and killing by cellular host immune responses. Viral reservoir cells harbouring intact HIV-1 from lymph nodes exhibited a phenotypic signature primarily characterized by upregulation of surface markers promoting cell survival, including CD44, CD28, CD127 and the IL-21 receptor. Together, these results suggest compartmentalized phenotypic signatures of immune selection in HIV-1 reservoir cells, implying that only small subsets of infected cells with optimal adaptation to their anatomical immune microenvironment are able to survive during long-term antiretroviral treatment. The identification of phenotypic markers distinguishing viral reservoir cells may inform future approaches for strategies to cure and eradicate HIV-1.

Low-density lipoprotein balances T cell metabolism and enhances response to anti-PD-1 blockade in a HCT116 spheroid model

Introduction

The discovery of immune checkpoints and the development of their specific inhibitors was acclaimed as a major breakthrough in cancer therapy. However, only a limited patient cohort shows sufficient response to therapy. Hence, there is a need for identifying new checkpoints and predictive biomarkers with the objective of overcoming immune escape and resistance to treatment. Having been associated with both, treatment response and failure, LDL seems to be a double-edged sword in anti-PD1 immunotherapy. Being embedded into complex metabolic conditions, the impact of LDL on distinct immune cells has not been sufficiently addressed. Revealing the effects of LDL on T cell performance in tumor immunity may enable individual treatment adjustments in order to enhance the response to routinely administered immunotherapies in different patient populations. The object of this work was to investigate the effect of LDL on T cell activation and tumor immunity in-vitro.

Methods

Experiments were performed with different LDL dosages (LDL^low = 50 μg/ml and LDL^high = 200 μg/ml) referring to medium control. T cell phenotype, cytokines and metabolism were analyzed. The functional relevance of our findings was studied in a HCT116 spheroid model in the context of anti-PD-1 blockade.

Results

The key points of our findings showed that LDL^high skewed the CD4⁺ T cell subset into a central memory-like phenotype, enhanced the expression of the co-stimulatory marker CD154 (CD40L) and significantly reduced secretion of IL-10. The exhaustion markers PD-1 and LAG-3 were downregulated on both T cell subsets and phenotypical changes were associated with a balanced T cell metabolism, in particular with a significant decrease of reactive oxygen species (ROS). T cell transfer into a HCT116 spheroid model resulted in a significant reduction of the spheroid viability in presence of an anti-PD-1 antibody combined with LDL^high.

Discussion

Further research needs to be conducted to fully understand the impact of LDL on T cells in tumor immunity and moreover, to also unravel LDL effects on other lymphocytes and myeloid cells for improving anti-PD-1 immunotherapy. The reason for improved response might be a resilient, less exhausted phenotype with balanced ROS levels.

Characterization of snakehead (Channa argus) interleukin-21: Involvement in immune defense against two pathogenic bacteria, in leukocyte proliferation, and in activation of JAK-STAT signaling pathway

Interleukin-21 (IL-21), a crucial immune regulatory molecule, belongs to the common γ-chain family of type I cytokines, and exerts pleiotropic effects on multiple immune cell types in mammals. However, the characteristics and functions of fish IL-21 remain unclear. To further investigate the molecular mechanism of IL-21 in teleosts, we first cloned and identified the IL-21 gene (designated shIL-21) of the snakehead (Channa argus). The full-length open reading frame of shIL-21 is 438 bp in length, and encodes a predicted protein of 145 amino acid residues. A sequence analysis showed that shIL-21 has the typical structural characteristics of other IL-21 proteins, containing four α-helices and four conserved cysteine residues. In a phylogenetic analysis, shIL-21 clustered within a subgroup of IL-21 proteins from other teleost species and shared its closest evolutionary relationship with that of Lates calcarifer. The expression analysis showed that shIL-21 was ubiquitously expressed in all the healthy snakehead tissues tested, albeit at different levels. After infection with Nocardia seriolae or Aeromonas schubertii, the relative expression of shIL-21 was mainly upregulated in the head kidney and spleen in vivo. Similarly, after stimulation with the three pathogen analogues lipoteichoic acid, lipopolysaccharides, and polyinosinic-polycytidylic acid, the expression of shIL-21 was also induced in head kidney leukocytes in vitro. A recombinant shIL-21 protein was expressed and purified, and promoted the proliferation of head kidney leukocytes, induced the expression of genes encoding critical signaling molecules in the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) pathway, including JAK1, JAK3, STAT1, and STAT3, and induced the expression of endogenous shIL-21 and genes encoding several key proinflammatory cytokines (tumor necrosis factor-α, interferon-γ, and IL-1β). Taken together, these preliminary findings suggest that shIL-21 is involved in the immune defense against bacterial infection, in leukocyte proliferation, and in the activation of the JAK-STAT pathway. They thus extend the functional studies of IL-21 in teleosts.

Gnawing Between Cells and Cells in the Immune System: Friend or Foe? A Review of Trogocytosis

Trogocytosis occurs when one cell contacts and quickly nibbles another cell and is characterized by contact between living cells and rapid transfer of membrane fragments with functional integrity. Many immune cells are involved in this process, such as T cells, B cells, NK cells, APCs. The transferred membrane molecules including MHC molecules, costimulatory molecules, receptors, antigens, etc. An increasing number of studies have shown that trogocytosis plays an important role in the immune system and the occurrence of relevant diseases. Thus, whether trogocytosis is a friend or foe of the immune system is puzzling, and the precise mechanism underlying it has not yet been fully elucidated. Here, we provide an integrated view of the acquired findings on the connections between trogocytosis and the immune system.

Prediction of improved survival in patients with pancreatic cancer via IL-21 enhanced detection of mesothelin epitope-reactive T-cell responses

Most patients with pancreatic cancer present with extensive metastasis at diagnosis, with a 5-year survival rate of approximately 5%, despite chemotherapy and surgery. New treatment modalities are needed to improve survival. Mesothelin is a tumor-associated antigen (TAA) in patients with pancreatic cancer that could be used to gauge cellular immune responses directed against transformed cells since up to 100 percent of pancreatic ductal adenocarcinoma cells have been shown to strongly express mesothelin. A prospective, observational study was carried out in twenty-six, chemotherapy-naïve patients with resectable pancreatic ductal adenocarcinoma. Participants were between 48 and 81 years (median age: 64.5 years), 15 males and 11 females. All participants were clinically followed-up between 439 and 853 days post-surgery (n=14) or until death (n=12). Peripheral blood drawn on the day of surgery was stimulated with a mesothelin peptide pool (42 peptides, non-overlapping), individual mesothelin peptides, positive (anti-CD3 antibody, OKT3) and negative controls (medium) with or without adding IL-21. Kaplan-Meier estimators were used to gauge patients’ survival pattern in relation to mesothelin-specific IFN-γ responses. A survival benefit was linked with IFN-γ responses to peptides corresponding to mature mesothelin (p=0.018) and targeted recognition of the mesothelin_601-615 epitope (MQEALSGTPCLLGPG) (p=0.006) in the presence of IL-21. Conversely, production of high levels of IFN-γ to OKT3 stimulation with IL-21 conditioning was associated with reduced survival of patients (p=0.016). Gauging anti-Mesothelin- directed immune responses will aid to identify patients i) in need of a more intensive clinical follow-up and ii) who may benefit from immunotherapeutic approaches targeting mesothelin.

IL-21 modulates memory and exhaustion phenotype of T-cells in a fatty acid oxidation-dependent manner

T-cell-based therapies represent a promising strategy for cancer treatment. In this context, cytokines are discussed as a bona fide instrument for fine-tuning T- cell biology. One promising candidate is the pleiotropic interleukin-21 (IL-21) with only little being known regarding its direct effects on human T-cells. Thus, we sought out to characterize the impact of IL-21 on T-cell metabolism, fitness, and differentiation. Culturing T-cells in presence of IL-21 elicited a metabolic skewing away from aerobic glycolysis towards fatty acid oxidation (FAO). These changes of the metabolic framework were paralleled by increased mitochondrial fitness and biogenesis. However, oxidative stress levels were not increased but rather decreased. Furthermore, elevated FAO and mitochondrial biomass together with enhanced antioxidative properties are linked to formation of longer lasting memory responses and less PD-1 expression. We similarly observed an IL-21-triggered induction of central memory-like T-cells and reduced levels of PD-1 on the cell surface. Taken together, IL-21 shifts T-cells towards an immunometabolic phenotype that has been associated with increased survivability and enhanced anti-tumor efficacy. In addition, our data reveals a novel interconnection between fatty acid metabolism and immune function regulated by IL 21.