IL-21-dependent expansion of memory-like NK cells enhances protective immune responses against Mycobacterium tuberculosis

BCG immunization induced KLRG1+ NK cells show memory-like responses to mycobacterial and HIV antigens

Bacille-Calmette-Guérin (BCG) is the only approved vaccine against Mycobacterium tuberculosis (MTB), offering protection not only against tuberculosis (TB) but also non-related infections. 'Trained immunity' of innate immune cells is considered one of the mechanisms of this broad protection derived through BCG. Here, we investigated the effect of BCG on Natural Killer (NK) cells, a key innate immune cell type, and their subsequent responses to mycobacterial and HIV antigens. We found that BCG-induced KLRG1+ NK cells exhibit significantly higher production of IFNγ, compared to KLRG1- cells, indicating their memory-like responses upon exposure to these antigens (p < 0.05). These findings may be important in regions of high burden of HIV and TB where BCG is routinely administered.

Lung-resident CD3-NK1.1+CD69+CD103+ Cells Play an Important Role in Bacillus Calmette-Guérin Vaccine-Induced Protective Immunity against Mycobacterium tuberculosis Infection

Tissue-resident immune cells play important roles in local tissue homeostasis and infection control. There is no information on the functional role of lung-resident CD3-NK1.1+CD69+CD103+ cells in intranasal Bacillus Calmette-Guérin (BCG)-vaccinated and/or Mycobacterium tuberculosis (Mtb)-infected mice. Therefore, we phenotypically and functionally characterized these cells in mice vaccinated intranasally with BCG. We found that intranasal BCG vaccination increased CD3-NK1.1+ cells with a tissue-resident phenotype (CD69+CD103+) in the lungs during the first 7 d after BCG vaccination. Three months post-BCG vaccination, Mtb infection induced the expansion of CD3-NK1.1+CD69+CD103+ (lung-resident) cells in the lung. Adoptive transfer of lung-resident CD3-NK1.1+CD69+CD103+ cells from the lungs of BCG-vaccinated mice to Mtb-infected naive mice resulted in a lower bacterial burden and reduced inflammation in the lungs. Our findings demonstrated that intranasal BCG vaccination induces the expansion of CD3-NK1.1+CD69+CD103+ (lung-resident) cells to provide protection against Mtb infection.

E3 ubiquitin ligase CBLB regulates innate immune responses and bacterial dissemination during nontuberculous mycobacteria infection

Nontuberculous mycobacteria (NTM) are emerging opportunistic pathogens causing pulmonary infection to fatal disseminated disease. NTM infections are steadily increasing in children and adults, and immune-compromised individuals are at a greater risk of fatal infections. The NTM disease's adverse pathology and resistance to antibiotics have further worsened the therapeutic measures. Innate immune regulators are potential targets for therapeutics to NTM, especially in a T cell-suppressed population, and many ubiquitin ligases modulate pathogenesis and innate immunity during infections, including mycobacterial infections. Here, we investigated the role of an E3 ubiquitin ligase, Casitas B-lineage lymphoma proto-oncogene B (CBLB), in immunocompromised mouse models of NTM infection. We found that CBLB is essential to prevent bacterial growth and dissemination. Cblb deficiency debilitated natural killer cells, inflammatory monocytes, and macrophages in vivo. However, Cblb deficiency in macrophages did not wane its ability to inhibit bacterial growth or production of reactive oxygen species or interferon γ production by natural killer cells in vitro. CBLB restricted NTM growth and dissemination by promoting early granuloma formation in vivo. Our study shows that CBLB bolsters innate immune responses and helps prevent the dissemination of NTM during compromised T cell immunity.

Novel Oral Adjuvant to Enhance Cytotoxic Memory-Like NK Cell Responses in an HIV Vaccine Platform

Antibody-dependent cell-mediated cytotoxicity, mediated by natural killer (NK) cells and antibodies, emerged as a secondary correlate of protection in the RV144 HIV vaccine clinical trial, the only vaccine thus far demonstrating some efficacy in human. Therefore, leveraging NK cells with enhanced cytotoxic effector responses may bolster vaccine induced protection against HIV. Here, we investigated the effect of orally administering indole-3-carbinol (I3C), an aryl hydrocarbon receptor (AHR) agonist, as an adjuvant to an RV144-like vaccine platform in a mouse model. We demonstrate the expansion of KLRG1-expressing NK cells induced by the vaccine together with I3C. This NK cell subset exhibited enhanced vaccine antigen-specific cytotoxic memory-like features. Our study underscores the potential of incorporating I3C as an oral adjuvant to HIV vaccine platforms to enhance antigen-specific (memory-like) cytotoxicity of NK cells against HIV-infected cells. This approach may contribute to enhancing the protective efficacy of HIV preventive vaccines against HIV acquisition.

Loss of circulating CD8α+ NK cells during human Mycobacterium tuberculosis infection

Natural Killer (NK) cells can recognize and kill Mtb-infected cells in vitro, however their role after natural human exposure has not been well-studied. To identify Mtb-responsive NK cell populations, we analyzed the peripheral blood of healthy household contacts of active Tuberculosis (TB) cases and source community donors in an endemic region of Port-au-Prince, Haiti by flow cytometry. We observed higher CD8α expression on NK cells in putative resistors (IGRA- contacts) with a progressive loss of these circulating cells during household-associated latent infection and disease. In vitro assays and CITE-seq analysis of CD8α+ NK cells demonstrated enhanced maturity, cytotoxic gene expression, and response to cytokine stimulation relative to CD8α- NK cells. CD8α+ NK cells also displayed dynamic surface expression dependent on MHC I in contrast to conventional CD8+ T cells. Together, these results support a specialized role for CD8α+ NK cell populations during Mtb infection correlating with disease resistance.

Therapeutic potential of interleukin-21 in cancer

Interleukin-21 (IL-21) is an immunostimulatory cytokine which belongs to the common gamma-chain family of cytokines. It plays an import role in the development, differentiation, proliferation, and activation of immune cells, in particular T and natural killer (NK) cells. Since its discovery in 2000, IL-21 has been shown to regulate both adaptive and immune responses associates with key role in antiviral and antitumor responses. Recent advances indicate IL-21 as a promising target for cancer treatment and encouraging results were obtained in preclinical studies which investigated the potency of IL-21 alone or in combination with other therapies, including monoclonal antibodies, checkpoint inhibitory molecules, oncolytic virotherapy, and adoptive cell transfer. Furthermore, IL-21 showed antitumor effects in the treatment of patients with advanced cancer, with minimal side effects in several clinical trials. In the present review, we will outline the recent progress in IL-21 research, highlighting the potential of IL-21 based therapy as single agent or in combination with other drugs to enhance cancer treatment efficiency.

OMIP-101: 27-color flow cytometry panel for immunophenotyping of major leukocyte populations in fixed whole blood

This 27-color flow cytometry antibody panel allows broad immune-profiling of major leukocyte subsets in human whole blood (WB). It includes lineage markers to identify myeloid and lymphoid cell populations including granulocytes, monocytes, myeloid dendritic cells (mDCs), natural killer (NK) cells, NKT-like cells, B cells, conventional CD4 and CD8 T cells, γδ T cells, mucosa-associated invariant T (MAIT) cells and innate lymphoid cells (ILC). To further characterize each of these populations, markers defining stages of cell differentiation (CCR7, CD27, CD45RA, CD127, CD57), cytotoxic potential (perforin, granzyme B) and cell activation/proliferation (HLA-DR, CD38, Ki-67) were included. This panel was developed for quantifying absolute counts and phenotyping major leukocyte populations in cryopreserved, fixed WB collected from participants enrolled in large multi-site tuberculosis (TB) vaccine clinical trials. This antibody panel can be applied to profile major leukocyte subsets in other sample types such as fresh WB or peripheral blood mononuclear cells (PBMCs) with only minor additional optimization.

When inflammatory stressors dramatically change, disease phenotypes may transform between autoimmune hematopoietic failure and myeloid neoplasms

Aplastic anemia (AA) and hypoplastic myelodysplastic syndrome are paradigms of autoimmune hematopoietic failure (AHF). Myelodysplastic syndrome and acute myeloid leukemia are unequivocal myeloid neoplasms (MNs). Currently, AA is also known to be a clonal hematological disease. Genetic aberrations typically observed in MNs are detected in approximately one-third of AA patients. In AA patients harboring MN-related genetic aberrations, a poor response to immunosuppressive therapy (IST) and an increased risk of transformation to MNs occurring either naturally or after IST are predicted. Approximately 10%-15% of patients with severe AA transform the disease phenotype to MNs following IST, and in some patients, leukemic transformation emerges during or shortly after IST. Phenotypic transformations between AHF and MNs can occur reciprocally. A fraction of advanced MN patients experience an aplastic crisis during which leukemic blasts are repressed. The switch that shapes the disease phenotype is a change in the strength of extramedullary inflammation. Both AHF and MNs have an immune-active bone marrow (BM) environment (BME). In AHF patients, an inflamed BME can be evoked by infiltrated immune cells targeting neoplastic molecules, which contributes to the BM-specific autoimmune impairment. Autoimmune responses in AHF may represent an antileukemic mechanism, and inflammatory stressors strengthen antileukemic immunity, at least in a significant proportion of patients who have MN-related genetic aberrations. During active inflammatory episodes, normal and leukemic hematopoieses are suppressed, which leads to the occurrence of aplastic cytopenia and leukemic cell regression. The successful treatment of underlying infections mitigates inflammatory stress-related antileukemic activities and promotes the penetration of leukemic hematopoiesis. The effect of IST is similar to that of treating underlying infections. Investigating inflammatory stress-powered antileukemic immunity is highly important in theoretical studies and clinical practice, especially given the wide application of immune-activating agents and immune checkpoint inhibitors in the treatment of hematological neoplasms.

Integrated Analysis of Single-Cell and Bulk RNA Sequencing Data Reveals Memory-like NK Cell Subset Associated with Mycobacterium tuberculosis Latency

Natural killer (NK) cells are innate-like lymphocytes that belong to the family of type-1 innate lymphoid cells and rapidly respond to virus-infected and tumor cells. In this study, we have combined scRNA-seq data and bulk RNA-seq data to define the phenotypic and molecular characteristics of peripheral blood NK cells. While the role of NK cells in immune surveillance against virus infections and tumors has been well established, their contribution to protective responses to other intracellular microorganisms, such as Mycobacterium tuberculosis (Mtb), is still poorly understood. In this study, we have combined scRNA-seq data and bulk RNA-seq data to illuminate the molecular characteristics of circulating NK cells in patients with active tuberculosis (TB) disease and subjects with latent Mtb infection (LTBI) and compared these characteristics with those of healthy donors (HDs) and patients with non-TB other pulmonary infectious diseases (ODs). We show here that the NK cell cluster was significantly increased in LTBI subjects, as compared to patients with active TB or other non-TB pulmonary diseases and HD, and this was mostly attributable to the expansion of an NK cell population expressing KLRC2, CD52, CCL5 and HLA-DRB1, which most likely corresponds to memory-like NK2.1 cells. These data were validated by flow cytometry analysis in a small cohort of samples, showing that LTBI subjects have a significant expansion of NK cells characterized by the prevalence of memory-like CD52+ NKG2C+ NK cells. Altogether, our results provide some new information on the role of NK cells in protective immune responses to Mtb.

p40 homodimers bridge ischemic tissue inflammation and heterologous alloimmunity in mice via IL-15 transpresentation

Virus-induced memory T cells often express functional cross-reactivity, or heterologous immunity, to other viruses and to allogeneic MHC molecules that is an important component of pathogenic responses to allogeneic transplants. During immune responses, antigen-reactive naive and central memory T cells proliferate in secondary lymphoid organs to achieve sufficient cell numbers to effectively respond, whereas effector memory T cell proliferation occurs directly within the peripheral inflammatory microenvironment. Mechanisms driving heterologous memory T cell proliferation and effector function expression within peripheral tissues remain poorly understood. Here, we dissected proliferation of heterologous donor-reactive memory CD8+ T cells and their effector functions following infiltration into heart allografts with low or high intensities of ischemic inflammation. Proliferation within both ischemic conditions required p40 homodimer-induced IL-15 transpresentation by graft DCs, but expression of effector functions mediating acute allograft injury occurred only in high-ischemic allografts. Transcriptional responses of heterologous donor-reactive memory CD8+ T cells were distinct from donor antigen-primed memory CD8+ T cells during early activation in allografts and at graft rejection. Overall, the results provide insights into mechanisms driving heterologous effector memory CD8+ T cell proliferation and the separation between proliferation and effector function that is dependent on the intensity of inflammation within the tissue microenvironment.

Immune Control in Repeated Babesia microti Infection in a Patient With B-Cell Deficiency

The immunology of human babesiosis is poorly investigated. We present a comprehensive investigation of a 75-year-old man with B-cell deficiency who experienced 3 episodes of babesiosis over a 6-year period. Slowly evolving clinical immunity was observed, as evidenced by milder clinical symptoms and lower peak parasite burden after each subsequent babesiosis episode. The patient exhibited several striking immunologic findings. First, the patient had exceptionally high Babesia microti-specific antibodies despite very few circulating B cells, which predominantly coexpressed CD27 (memory marker) and CD95 (death receptor). Second, we demonstrated the presence of long-lasting NK cells and expansion of T memory stem cells. Third, levels of the IP-10 cytokine directly correlated with parasite burden. These results raise fundamental questions on the priming, maintenance, and location of a B-cell population that produces high antibody levels in the face of severe B-cell deficiency. Our results should invoke interest among researchers to study the immunology and pathogenesis of human babesiosis.

Antigen-specific memory NK cell responses against HIV and influenza use the NKG2/HLA-E axis

Multiple studies have broadened the roles of natural killer (NK) cells functioning as purely innate lymphocytes by demonstrating that they are capable of putative antigen-specific immunological memory against multiple infectious agents including HIV-1 and influenza. However, the mechanisms underlying antigen specificity remain unknown. Here, we demonstrate that antigen-specific human NK cell memory develops upon exposure to both HIV and influenza, unified by a conserved and epitope-specific targetable mechanism largely dependent on the activating CD94/NKG2C receptor and its ligand HLA-E. We validated the permanent acquisition of antigen specificity by individual memory NK cells by single-cell cloning. We identified elevated expression of KLRG1, α4β7, and NKG2C as biomarkers of antigen-specific NK cell memory through complex immunophenotyping. Last, we uncovered individual HLA-E-restricted peptides that may constitute the dominant NK cell response in HIV-1- and influenza-infected persons in vivo. Our findings clarify the mechanisms contributing to antigen-specific memory NK cell responses and suggest that they could be potentially targeted therapeutically for vaccines or other therapeutic interventions.

Early innate cell interactions with Mycobacterium tuberculosis in protection and pathology of tuberculosis

Tuberculosis (TB) remains a significant global health challenge, claiming the lives of up to 1.5 million individuals annually. TB is caused by the human pathogen Mycobacterium tuberculosis (Mtb), which primarily infects innate immune cells in the lungs. These immune cells play a critical role in the host defense against Mtb infection, influencing the inflammatory environment in the lungs, and facilitating the development of adaptive immunity. However, Mtb exploits and manipulates innate immune cells, using them as favorable niche for replication. Unfortunately, our understanding of the early interactions between Mtb and innate effector cells remains limited. This review underscores the interactions between Mtb and various innate immune cells, such as macrophages, dendritic cells, granulocytes, NK cells, innate lymphocytes-iNKT and ILCs. In addition, the contribution of alveolar epithelial cell and endothelial cells that constitutes the mucosal barrier in TB immunity will be discussed. Gaining insights into the early cellular basis of immune reactions to Mtb infection is crucial for our understanding of Mtb resistance and disease tolerance mechanisms. We argue that a better understanding of the early host-pathogen interactions could inform on future vaccination approaches and devise intervention strategies.

Natural Killer Repertoire Restoration in TB/HIV Co-Infected Individuals Experienced an Immune Reconstitution Syndrome (CAMELIA Trial, ANRS 12153)

IRIS is a common complication in HIV-infected patients treated for tuberculosis (TB) and cART. Our aim was to evaluate NK cell reconstitution in HIV-infected patients with TB-IRIS compared to those without IRIS. 147 HIV-infected patients with TB from the CAMELIA trial were enrolled. HIV+TB+ patients were followed for 32 weeks. The NK cell repertoire was assessed in whole blood at different time points. As CAMELIA has two arms (early and late cART initiation), we analysed them separately. At enrolment, individuals had low CD4 cell counts (27 cells/mm3) and high plasma viral loads (5.76 and 5.50 log/mL for IRIS and non-IRIS individuals, respectively). Thirty-seven people developed IRIS (in the early and late arms). In the early and late arms, we observed similar proportions of total NK and NK cell subsets in TB-IRIS and non-IRIS individuals during follow-up, except for the CD56dimCD16pos (both arms) and CD56dimCD16neg (late arm only) subsets, which were higher in TB-IRIS and non-IRIS individuals, respectively, after cART. Regarding the repertoire and markers of NK cells, significant differences (lower expression of NKp30, NKG2A (CD159a), NKG2D (CD314) were observed in TB-IRIS compared to non-IRIS individuals after the start of cART. In the late arm, some changes (increased expression of CD69, NKG2C, CD158i) were observed in TB-IRIS compared to non-IRIS individuals, but only before cART initiation (during TB treatment). KIR expression by NK cells (CD158a and CD158i) was similar in both groups. CD69 expression by NK cells decreased in all groups. Expression of the NCR repertoire (NKp30, NKp44, NKp46) has similar kinetics in TB-IRIS subjects compared to non-IRIS subjects regardless of the arm analysed. NK cell reconstitution appeared to be better in TB-IRIS subjects. Although NK cell reconstitution is impaired in HIV infection after cART, as previously reported, it does not appear to be affected by the development of IRIS in HIV and TB-infected individuals.

Leukemic transformation during anti-tuberculosis treatment in aplastic anemia-paroxysmal nocturnal hemoglobinuria syndrome: A case report and review of literature

BACKGROUND

Accumulating evidence demonstrates that autoimmune hematopoietic failure and myeloid neoplasms have an intrinsic relationship with regard to clonal hematopoiesis and disease evolution. In approximately 10%-15% of patients with severe aplastic anemia (SAA), the disease phenotype is transformed into myeloid neoplasms following antithymocyte globulin plus cyclosporine-based immunosuppressive therapy. In some of these patients, myeloid neoplasms appear during or shortly after immunosuppressive therapy. Leukemic transformation in SAA patients during anti-tuberculosis treatment has not been reported.

CASE SUMMARY

A middle-aged Chinese female had a 6-year history of non-SAA and a 2-year history of paroxysmal nocturnal hemoglobinuria (PNH). With aggravation of systemic inflammatory symptoms, severe pancytopenia developed, and her hemoglobinuria disappeared. Laboratory findings in cytological, immunological and cytogenetic analyses of bone marrow samples met the diagnostic criteria for "SAA." Definitive diagnosis of disseminated tuberculosis was made in the search for infectious niches. Remarkable improvement in hematological parameters was achieved within 1 mo of anti-tuberculosis treatment, and complete hematological remission was achieved within 4 mo of treatment. Frustratingly, the hematological response lasted for only 3 mo, and pancytopenia reemerged. At this time, cytological findings (increased bone marrow cellularity and an increased percentage of myeloblasts that accounted for 16.0% of all nucleated hematopoietic cells), immunological findings (increased percentage of cluster of differentiation 34+ cells that accounted for 12.28% of all nucleated hematopoietic cells) and molecular biological findings (identification of somatic mutations in nucleophosmin-1 and casitas B-lineage lymphoma genes) revealed that "SAA" had transformed into acute myeloid leukemia with mutated nucleophosmin-1. The transformation process suggested that the leukemic clones were preexistent but were suppressed in the PNH and SAA stages, as development of symptomatic myeloid neoplasm through acquisition and accumulation of novel oncogenic mutations is unlikely in an interval of only 7 mo. Aggravation of inflammatory stressors due to disseminated tuberculosis likely contributed to the repression of normal and leukemic hematopoiesis, and the relief of inflammatory stressors due to anti-tuberculosis treatment contributed to penetration of neoplastic hematopoiesis. The concealed leukemic clones in the SAA and PNH stages raise the possibility of an inflammatory stress-fueled antileukemic mechanism.

CONCLUSION

Aggravated inflammatory stressors can repress normal and leukemic hematopoiesis, and relieved inflammatory stressors can facilitate penetration of neoplastic hematopoiesis.

Engineered human pluripotent stem cell-derived natural killer cells with PD-L1 responsive immunological memory for enhanced immunotherapeutic efficacy

Adoptive chimeric antigen receptor (CAR)-engineered natural killer (NK) cells have shown promise in treating various cancers. However, limited immunological memory and access to sufficient numbers of allogenic donor cells have hindered their broader preclinical and clinical applications. Here, we first assess eight different CAR constructs that use an anti-PD-L1 nanobody and/or universal anti-fluorescein (FITC) single-chain variable fragment (scFv) to enhance antigen-specific proliferation and anti-tumor cytotoxicity of NK-92 cells against heterogenous solid tumors. We next genetically engineer human pluripotent stem cells (hPSCs) with optimized CARs and differentiate them into functional dual CAR-NK cells. The tumor microenvironment responsive anti-PD-L1 CAR effectively promoted hPSC-NK cell proliferation and cytotoxicity through antigen-dependent activation of phosphorylated STAT3 (pSTAT3) and pSTAT5 signaling pathways via an intracellular truncated IL-2 receptor β-chain (ΔIL-2Rβ) and STAT3-binding tyrosine-X-X-glutamine (YXXQ) motif. Anti-tumor activities of PD-L1-induced memory-like hPSC-NK cells were further boosted by administering a FITC-folate bi-specific adapter that bridges between a programmable anti-FITC CAR and folate receptor alpha-expressing breast tumor cells. Collectively, our hPSC CAR-NK engineering platform is modular and could constitute a realistic strategy to manufacture off-the-shelf CAR-NK cells with immunological memory-like phenotype for targeted immunotherapy.

Identification and function of a novel human memory-like NK cell population expressing CD160 in melioidosis

NK cells are endowed with immunological memory to a range of pathogens but the development of NK cell memory in bacterial infections remains elusive. Here, we establish an assay inducing memory-like NK cell response to Burkholderia pseudomallei, the causative agent of the severe bacterial disease called melioidosis, and explore NK cell memory in a melioidosis patient cohort. We show that NK cells require bacteria-primed monocytes to acquire memory-like properties, demonstrated by bacteria-specific responses, features that strongly associate with CD160 expression. Induction of this memory-like NK cell is partly dependent on CD160 and IL-12R. Importantly, CD160 expression identifies memory-like NK cells in a cohort of recovered melioidosis patients with heightened responses maintained at least 3 months post hospital admission and reduced numbers of this cell population independently correlate with recurrent melioidosis. These newly identified memory-like NK cells are a promising target for future vaccine design and for monitoring protection against infection.

Streptococcus pneumoniae drives specific and lasting Natural Killer cell memory

NK cells are important mediators of innate immunity and play an essential role for host protection against infection, although their responses to bacteria are poorly understood. Recently NK cells were shown to display memory properties, as characterized by an epigenetic signature leading to a stronger secondary response. Although NK cell memory could be a promising mechanism to fight against infection, it has not been described upon bacterial infection. Using a mouse model, we reveal that NK cells develop specific and long-term memory following sub-lethal infection with the extracellular pathogen Streptococcus pneumoniae. Memory NK cells display intrinsic sensing and response to bacteria in vitro, in a manner that is enhanced post-bacterial infection. In addition, their transfer into naïve mice confers protection from lethal infection for at least 12 weeks. Interestingly, NK cells display enhanced cytotoxic molecule production upon secondary stimulation and their protective role is dependent on Perforin and independent of IFNγ. Thus, our study identifies a new role for NK cells during bacterial infection, opening the possibility to harness innate immune memory for therapeutic purposes.

HIV-Differentiated Metabolite N-Acetyl-L-Alanine Dysregulates Human Natural Killer Cell Responses to Mycobacterium tuberculosis Infection

Mycobacterium tuberculosis (Mtb) has latently infected over two billion people worldwide (LTBI) and caused ~1.6 million deaths in 2021. Human immunodeficiency virus (HIV) co-infection with Mtb will affect the Mtb progression and increase the risk of developing active tuberculosis by 10-20 times compared with HIV- LTBI+ patients. It is crucial to understand how HIV can dysregulate immune responses in LTBI+ individuals. Plasma samples collected from healthy and HIV-infected individuals were investigated using liquid chromatography-mass spectrometry (LC-MS), and the metabolic data were analyzed using the online platform Metabo-Analyst. ELISA, surface and intracellular staining, flow cytometry, and quantitative reverse-transcription PCR (qRT-PCR) were performed using standard procedures to determine the surface markers, cytokines, and other signaling molecule expressions. Seahorse extra-cellular flux assays were used to measure mitochondrial oxidative phosphorylation and glycolysis. Six metabolites were significantly less abundant, and two were significantly higher in abundance in HIV+ individuals compared with healthy donors. One of the HIV-upregulated metabolites, N-acetyl-L-alanine (ALA), inhibits pro-inflammatory cytokine IFN-γ production by the NK cells of LTBI+ individuals. ALA inhibits the glycolysis of LTBI+ individuals' NK cells in response to Mtb. Our findings demonstrate that HIV infection enhances plasma ALA levels to inhibit NK-cell-mediated immune responses to Mtb infection, offering a new understanding of the HIV-Mtb interaction and providing insights into the implication of nutrition intervention and therapy for HIV-Mtb co-infected patients.

HIV-differentiated metabolite N-Acetyl-L-Alanine dysregulates human natural killer cell responses to Mycobacterium tuberculosis infection

Background

Mycobacterium tuberculosis ( Mtb ) has latently infected over two billion people worldwide (LTBI) and causes 1.8 million deaths each year. Human immunodeficiency virus (HIV) co-infection with Mtb will affect the Mtb progression and increase the risk of developing active tuberculosis by 10-20 times compared to the HIV-LTBI+ patients. It is crucial to understand how HIV can dysregulate immune responses in LTBI+ individuals.

Methods

Plasma samples collected from healthy and HIV-infected individuals were investigated by liquid chromatography-mass spectrometry (LC-MS), and the metabolic data were analyzed using an online platform Metabo-Analyst. ELISA, surface and intracellular staining, flow cytometry, quantitative reverse transcription PCR (qRT-PCR) were performed by standard procedure to determine the surface markers, cytokines and other signaling molecule expression. Seahorse extra cellular flux assays were used to measure the mitochondrial oxidative phosphorylation and glycolysis.

Results

Six metabolites were significantly less abundant, and two were significantly higher in abundance in HIV+ individuals compared to healthy donors. One of the HIV-upregulated metabolites, N-Acetyl-L-Alanine (ALA), inhibits pro-inflammatory cytokine IFN-□ production by NK cells of LTBI+ individuals. ALA inhibits glycolysis of LTBI+ individuals' NK cells in response to Mtb .

Conclusions

Our findings demonstrate that HIV infection enhances plasma ALA levels to inhibit NK cell-mediated immune responses to Mtb infection, offering a new understanding of the HIV- Mtb interaction and providing the implication of nutrition intervention and therapy for HIV- Mtb co-infected patients.

Mycobacterium tuberculosis infection drives a type I IFN signature in lung lymphocytes

Mycobacterium tuberculosis (Mtb) infects 25% of the world's population and causes tuberculosis (TB), which is a leading cause of death globally. A clear understanding of the dynamics of immune response at the cellular level is crucial to design better strategies to control TB. We use the single-cell RNA sequencing approach on lung lymphocytes derived from healthy and Mtb-infected mice. Our results show the enrichment of the type I IFN signature among the lymphoid cell clusters, as well as heat shock responses in natural killer (NK) cells from Mtb-infected mice lungs. We identify Ly6A as a lymphoid cell activation marker and validate its upregulation in activated lymphoid cells following infection. The cross-analysis of the type I IFN signature in human TB-infected peripheral blood samples further validates our results. These findings contribute toward understanding and characterizing the transcriptional parameters at a single-cell depth in a highly relevant and reproducible mouse model of TB.

Natural Killer (NK) and CAR-NK Cell Expansion Method using Membrane Bound-IL-21-Modified B Cell Line

Chimeric antigen receptor (CAR)-modified immune cell therapy has become an emerging treatment for cancers and infectious diseases. NK-based immunotherapy, particularly CAR-NK cell, is one of the most promising 'off-the-shelf' development without severe life-threatening toxicity. However, the bottleneck for developing a successful CAR-NK therapy is achieving sufficient numbers of non-exhaustive, long-lived, 'off-the-shelf' CAR-NK cells from a third party. Here, we developed a new CAR-NK expansion method using an Epstein-Barr virus- (EBV) transformed B cell line expressing a genetically modified membrane form of interleukin-21 (IL-21). In this protocol, step-by-step procedures are provided to expand NK and CAR-NK cells from cord blood and peripheral blood, as well as solid organ tissues. This work will significantly enhance the clinical development of CAR-NK immunotherapy.

Disseminated lymph node tuberculosis after splenectomy: an unusual case report in an adolescent

BACKGROUND

Splenectomized patients are at an increased risk for overwhelming post-splenectomy infections typically with encapsulated bacteria. The clinical association between splenectomy and lymph-node tuberculosis is unclear.

CASE PRESENTATION

We describe a rare case of disseminated tuberculous lymphadenitis in an 18-year-old woman with history of splenectomy because of hereditary sherocytosis. She was admitted with enlargement of bilateral-cervical and left-axillary lymph nodes and fever. A diagnosis of probable tuberculosis was made based on the findings of fine-needle aspiration. Histology showed granulomas and extensive caseous necrosis, with the site of puncture located at an enlarged lymph node on the right side. The diagnosis was confirmed via nucleic-acid amplification tests following excisional biopsy of the left axillary lymph node. Disseminated tuberculous lymphadenitis was localized in the bilateral neck, right lung hilum, left sub-axillary region, and mediastinum, as detected from contrast-enhanced computed tomography of the neck.

CONCLUSIONS

Mycobacterium tuberculosis infection should be considered in children and adolescents with extensive enlargement of lymph nodes after splenectomy.

Emerging cellular and molecular interactions between the lung microbiota and lung diseases

With the discovery of the lung microbiota, its study in both pulmonary health and disease has become a vibrant area of emerging research interest. Thus far, most studies have described the lung microbiota composition in lung disease quite well, and some of these studies indicated alterations in lung microbial communities related to the onset and development of lung disease and vice versa. However, the underlying mechanisms, particularly the cellular and molecular links, are still largely unknown. In this review, we highlight the current progress in the complex cellular and molecular mechanisms by which the lung microbiome interacts with immune homeostasis and pulmonary disease pathogenesis to advance our understanding of the elaborate function of the lung microbiota in lung disease. We hope that this work can attract more attention to this still-young yet very promising field to facilitate the identification of new therapeutic targets and provide more innovative therapies. Additional accurate standard-based methodologies and technological breakthroughs are critical to propel the field forward to ultimately achieve the goal of maintaining respiratory health.

Defective expansion and function of memory like natural killer cells in HIV+ individuals with latent tuberculosis infection

Purpose

Tuberculosis (TB) is the leading cause of infectious disease related mortality, and only 10% of the infected individuals develop active disease. The likelihood of progression of latent tuberculosis infection (LTBI) to active TB disease is high in HIV infected individuals. Identification of HIV+ individuals at risk would allow treating targeted population, facilitating completion of therapy for LTBI and prevention of TB development. NK cells have an important role in T cell independent immunity against TB, but the exact role of NK cell subsets in LTBI and HIV is not well characterized.

Methods

In this study, we compared the expansion and function of memory like NK cells from HIV-LTBI+ individuals and treatment naïve HIV+LTBI+ patients in response to Mtb antigens ESAT-6 and CFP-10.

Results

In freshly isolated PBMCs, percentages of CD3^-CD56⁺ NK cells were similar in HIV+LTBI+ patients and healthy HIV-LTBI+ individuals. However, percentages of CD3^-CD56⁺CD16⁺ NK cells were higher in healthy HIV-LTBI+ individuals compared to HIV+LTBI+ patients. HIV infection also inhibited the expansion of memory like NK cells, production of IL-32α, IL-15 and IFN-γ in response to Mtb antigens in LTBI+ individuals.

Conclusion

We studied phenotypic, functional subsets and activation of memory like-NK cells during HIV infection and LTBI. We observed that HIV+LTBI+ patients demonstrated suboptimal NK cell and monocyte interactions in response to Mtb, leading to reduced IL-15, IFN-γ and granzyme B and increased CCL5 production. Our study highlights the effect of HIV and LTBI on modulation of NK cell activity to understand their role in development of interventions to prevent progression to TB in high risk individuals.

Distinct blood transcriptomic signature of treatment in latent tuberculosis infected individuals at risk of developing active disease

Although only a small fraction will ever develop the active form of tuberculosis (ATB) disease, chemoprophylaxis treatment in latent TB infected (LTBI) individuals is an effective strategy to control pathogen transmission. Characterizing immune responses in LTBI upon chemoprophylactic treatment is important to facilitate treatment monitoring, and thus improve TB control strategies. Here, we studied changes in the blood transcriptome in a cohort of 42 LTBI and 8 ATB participants who received anti-TB therapy. Based on the expression of previously published gene signatures of progression to ATB, we stratified the LTBI cohort in two groups and examined if individuals deemed to be at elevated risk of developing ATB before treatment (LTBI-Risk) differed from others (LTBI-Other). We found that LTBI-Risk and LTBI-Other groups were associated with two distinct transcriptomic treatment signatures, with the LTBI-Risk signature resembling that of treated ATB patients. Notably, overlapping genes between LTBI-Risk and ATB treatment signatures were associated with risk of progression to ATB and interferon (IFN) signaling, and were selectively downregulated upon treatment in the LTBI-Risk but not the LTBI-Other group. Our results suggest that transcriptomic reprogramming following treatment of LTBI is heterogeneous and can be used to distinguish LTBI-Risk individuals from the LTBI cohort at large.

Reduced thyroxine production in young household contacts of tuberculosis patients increases active tuberculosis disease risk

In the current study, we followed 839 household contacts (HHCs) of tuberculosis (TB) patients for 2 years and identified the factors that enhanced the development of TB. Fourteen of the 17 HHCs who progressed to TB were in the 15- to 30-year-old age group. At baseline (the “0“ time point, when all the individuals were healthy), the concentration of the thyroid hormone thyroxine (T4) was lower, and there were increased numbers of Tregs in PBMCs of TB progressors. At baseline, PBMCs from TB progressors stimulated with early secretory antigenic target 6 (ESAT-6) and 10 kDa culture filtrate antigen (CFP-10) produced less IL-1α. Thyroid hormones inhibited Mycobacterium tuberculosis (Mtb) growth in macrophages in an IL-1α–dependent manner. Mtb-infected Thra1^PV/+ (mutant thyroid hormone receptor) mice had increased mortality and reduced IL-1α production. Our findings suggest that young HHCs who exhibit decreased production of thyroid hormones are at high risk of developing active TB disease.

Phenotype of Peripheral NK Cells in Latent, Active, and Meningeal Tuberculosis

The mechanisms underlying the immunopathology of tuberculous meningitis (TBM), the most severe clinical form of extrapulmonary tuberculosis (TB), are not understood. It is currently believed that the spread of Mycobacterium tuberculosis (Mtb) from the lung is an early event that occurs before the establishment of adaptive immunity. Hence, several innate immune mechanisms may participate in the containment of Mtb infection and prevent extrapulmonary disease manifestations. Natural killer (NK) cells participate in defensive processes that distinguish latent TB infection (LTBI) from active pulmonary TB (PTB). However, their role in TBM is unknown. Here, we performed a cross-sectional analysis of circulating NK cellCID="C008" value="s" phenotype in a prospective cohort of TBM patients (n = 10) using flow cytometry. Also, we addressed the responses of memory-like NK cell subpopulations to the contact with Mtb antigens in vitro. Finally, we determined plasma levels of soluble NKG2D receptor ligands in our cohort of TBM patients by enzyme-linked immunosorbent assay (ELISA). Our comparative groups consisted of individuals with LTBI (n = 11) and PTB (n = 27) patients. We found that NK cells from TBM patients showed lower absolute frequencies, higher CD69 expression, and poor expansion of the CD45RO⁺ memory-like subpopulation upon Mtb exposure in vitro compared to LTBI individuals. In addition, a reduction in the frequency of CD56^brightCD16⁻ NK cells characterized TBM patients but not LTBI or PTB subjects. Our study expands on earlier reports about the role of NK cells in TBM showing a reduced frequency of cytokine-producing cells compared to LTBI and PTB.

Use of a Contained Mycobacterium tuberculosis Mouse Infection Model to Predict Active Disease and Containment in Humans

Previous studies have identified whole-blood transcriptional risk and disease signatures for tuberculosis; however, several lines of evidence suggest that these signatures primarily reflect bacterial burden, which increases before symptomatic disease. We found that the peripheral blood transcriptome of mice with contained Mycobacterium tuberculosis infection (CMTI) has striking similarities to that of humans with active tuberculosis and that a signature derived from these mice predicts human disease with accuracy comparable to that of signatures derived directly from humans. A set of genes associated with immune defense are up-regulated in mice with CMTI but not in humans with active tuberculosis, suggesting that their up-regulation is associated with bacterial containment. A signature comprising these genes predicts both protection from tuberculosis disease and successful treatment at early time points where current signatures are not predictive. These results suggest that detailed study of the CMTI model may enable identification of biomarkers for human tuberculosis.

The immune landscape in tuberculosis reveals populations linked to disease and latency

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) latently infects approximately one-fourth of the world's population. The immune mechanisms that govern progression from latent (LTBI) to active pulmonary TB (PTB) remain poorly defined. Experimentally Mtb-infected non-human primates (NHP) mirror the disease observed in humans and recapitulate both PTB and LTBI. We characterized the lung immune landscape in NHPs with LTBI and PTB using high-throughput technologies. Three defining features of PTB in macaque lungs include the influx of plasmacytoid dendritic cells (pDCs), an Interferon (IFN)-responsive macrophage population, and activated T cell responses. In contrast, a CD27+ Natural killer (NK) cell subset accumulated in the lungs of LTBI macaques. This NK cell population was also detected in the circulation of LTBI individuals. This comprehensive analysis of the lung immune landscape will improve the understanding of TB immunopathogenesis, providing potential targets for therapies and vaccines for TB control.

The role of donor-unrestricted T-cells, innate lymphoid cells, and NK cells in anti-mycobacterial immunity

Vaccination strategies against mycobacteria, focusing mostly on classical T‐ and B‐cells, have shown limited success, encouraging the addition of alternative targets. Classically restricted T‐cells recognize antigens presented via highly polymorphic HLA class Ia and class II molecules, while donor‐unrestricted T‐cells (DURTs), with few exceptions, recognize ligands via genetically conserved antigen presentation molecules. Consequently, DURTs can respond to the same ligands across diverse human populations. DURTs can be activated either through cognate TCR ligation or via bystander cytokine signaling. TCR‐driven antigen‐specific activation of DURTs occurs upon antigen presentation via non‐polymorphic molecules such as HLA‐E, CD1, MR1, and butyrophilin, leading to the activation of HLA‐E–restricted T‐cells, CD1‐restricted T‐cells, mucosal‐associated invariant T‐cells (MAITs), and TCRγδ T‐cells, respectively. NK cells and innate lymphoid cells (ILCs), which lack rearranged TCRs, are activated through other receptor‐triggering pathways, or can be engaged through bystander cytokines, produced, for example, by activated antigen‐specific T‐cells or phagocytes. NK cells can also develop trained immune memory and thus could represent cells of interest to mobilize by novel vaccines. In this review, we summarize the latest findings regarding the contributions of DURTs, NK cells, and ILCs in anti–M tuberculosis, M leprae, and non‐tuberculous mycobacterial immunity and explore possible ways in which they could be harnessed through vaccines and immunotherapies to improve protection against Mtb.

The Role of Innate Immunity in Pulmonary Infections

Innate immunity forms a protective line of defense in the early stages of pulmonary infection. The primary cellular players of the innate immunity against respiratory infections are alveolar macrophages (AMs), dendritic cells (DCs), neutrophils, natural killer (NK) cells, and innate lymphoid cells (ILCs). They recognize conserved structures of microorganisms through membrane-bound and intracellular receptors to initiate appropriate responses. In this review, we focus on the prominent roles of innate immune cells and summarize transmembrane and cytosolic pattern recognition receptor (PRR) signaling recognition mechanisms during pulmonary microbial infections. Understanding the mechanisms of PRR signal recognition during pulmonary pathogen infections will help us to understand pulmonary immunopathology and lay a foundation for the development of effective therapies to treat and/or prevent pulmonary infections.

Initiation of Post-Primary Tuberculosis of the Lungs: Exploring the Secret Role of Bone Marrow Derived Stem Cells

Mycobacterium tuberculosis (Mtb), the causative organism of pulmonary tuberculosis (PTB) now infects more than half of the world population. The efficient transmission strategy of the pathogen includes first remaining dormant inside the infected host, next undergoing reactivation to cause post-primary tuberculosis of the lungs (PPTBL) and then transmit via aerosol to the community. In this review, we are exploring recent findings on the role of bone marrow (BM) stem cell niche in Mtb dormancy and reactivation that may underlie the mechanisms of PPTBL development. We suggest that pathogen's interaction with the stem cell niche may be relevant in potential inflammation induced PPTBL reactivation, which need significant research attention for the future development of novel preventive and therapeutic strategies for PPTBL, especially in a post COVID-19 pandemic world. Finally, we put forward potential animal models to study the stem cell basis of Mtb dormancy and reactivation.

Memory like NK cells display stem cell like properties after Zika virus infection

NK cells have been shown to display adaptive traits such as memory formation akin to T and B lymphocytes. Here we show that Zika virus infection induces memory like NK cells that express CD27. Strikingly, these cells exhibit stem-like features that include expansion capacity, self-renewal pathway, differentiation into effector cells, longer telomeres and gene signature associated with hematopoietic stem cell (HSC) progenitors. This subset shared transcriptional and epigenetic changes with memory CD8 T cells, stem cells and stem like T cells. These NK cells with memory and stem cell features, which we term "NK memory stem cells", demonstrated greater antiviral potential than CD27- or naïve CD27+ NK when adoptively transferred to Zika infected mice. Our results also suggest a role for the transcription factor TCF-1 in memory and stemness features of this NK subset. This study defines a unique TCF1hi CD27+ NK subset with memory capacity and stem cell features that play a role in antiviral immunity.

A Bovine Enteric Mycobacterium Infection Model to Analyze Parenteral Vaccine-Induced Mucosal Immunity and Accelerate Vaccine Discovery

Mycobacterial diseases of cattle are responsible for considerable production losses worldwide. In addition to their importance in animals, these infections offer a nuanced approach to understanding persistent mycobacterial infection in native host species. Mycobacteriumavium ssp. paratuberculosis (MAP) is an enteric pathogen that establishes a persistent, asymptomatic infection in the small intestine. Difficulty in reproducing infection in surrogate animal models and limited understanding of mucosal immune responses that control enteric infection in the natural host have been major barriers to MAP vaccine development. We previously developed a reproducible challenge model to establish a consistent MAP infection using surgically isolated intestinal segments prepared in neonatal calves. In the current study, we evaluated whether intestinal segments could be used to screen parenteral vaccines that alter mucosal immune responses to MAP infection. Using Silirum^® – a commercial MAP bacterin – we demonstrate that intestinal segments provide a platform for assessing vaccine efficacy within a relatively rapid period of 28 days post-infection. Significant differences between vaccinates and non-vaccinates could be detected using quantitative metrics including bacterial burden in intestinal tissue, MAP shedding into the intestinal lumen, and vaccine-induced mucosal immune responses. Comparing vaccine-induced responses in mucosal leukocytes isolated from the site of enteric infection versus blood leukocytes revealed substantial inconsistences between these immune compartments. Moreover, parenteral vaccination with Silirum did not induce equal levels of protection throughout the small intestine. Significant control of MAP infection was observed in the continuous but not the discrete Peyer’s patches. Analysis of these regional mucosal immune responses revealed novel correlates of immune protection associated with reduced infection that included an increased frequency of CD335⁺ innate lymphoid cells, and increased expression of IL21 and IL27. Thus, intestinal segments provide a novel model to accelerate vaccine screening and discovery by testing vaccines directly in the natural host and provides a unique opportunity to interrogate mucosal immune responses to mycobacterial infections.

The role of Th17 cells in psoriasis

T helper 17 (Th17) cells have been involved in the pathogenesis of many autoimmune and inflammatory diseases, like psoriasis, multiple sclerosis (MS), rheumatoid arthritis (RA), and inflammatory bowel disease (IBD). However, the role of Th17 cells in psoriasis has not been clarified completely. Th17-derived proinflammatory cytokines including IL-17A, IL-17F, IL-21, IL-22, and IL-26 have a critical role in the pathogenesis of these disorders. In this review, we introduced the signaling and transcriptional regulation of Th17 cells. And then, we demonstrate the immunopathology role of Th17 cells and functions of the related cytokines in the psoriasis to get a better understanding of the inflammatory mechanisms mediated by Th17 cells in this disease.

Antigens of Mycobacterium tuberculosis Stimulate CXCR6+ Natural Killer Cells

Natural killer (NK) cells participate in immunity against several pathogens by exerting cytotoxic and cytokine-production activities. Some NK cell subsets also mediate recall responses that resemble memory of adaptive lymphocytes against antigenic and non-antigenic stimuli. The C-X-C motif chemokine receptor 6 (CXCR6) is crucial for the development and maintenance of memory-like responses in murine NK cells. In humans, several subsets of tissue-resident and circulating NK cells with different functional properties express CXCR6. However, the role of CXCR6+ NK cells in immunity against relevant human pathogens is unknown. Here, we addressed whether murine and human CXCR6+ NK cells respond to antigens of Mycobacterium tuberculosis (Mtb). For this purpose, we evaluated the immunophenotype of hepatic and splenic CXCR6+ NK cells in mice exposed to a cell-wall (CW) extract of Mtb strain H37Rv. Also, we characterized the expression of CXCR6 in peripheral NK cells from active pulmonary tuberculosis (ATB) patients, individuals with latent TB infection (LTBI), and healthy volunteer donors (HD). Furthermore, we evaluated the responses of CXCR6+ NK cells from HD, LTBI, and ATB subjects to the in vitro exposure to CW preparations of Mtb H37Rv and Mtb HN878. Our results showed that murine hepatic CXCR6+ NK cells expand in vivo after consecutive administrations of Mtb H37Rv CW to mice. Remarkably, pooled hepatic and splenic, but not isolated splenic NK cells from treated mice, enhance their cytokine production capacity after an in vitro re-challenge with H37Rv CW. In humans, CXCR6+ NK cells were barely detected in the peripheral blood, although slightly significative increments in the percentage of CXCR6+, CXCR6+CD49a−, CXCR6+CD49a+, and CXCR6+CD69+ NK cells were observed in ATB patients as compared to HD and LTBI individuals. In contrast, the expansion of CXCR6+CD49a− and CXCR6+CD69+ NK cells in response to the in vitro stimulation with Mtb H37Rv was higher in LTBI individuals than in ATB patients. Finally, we found that Mtb HN878 CW generates IFN-γ-producing CXCR6+CD49a+ NK cells. Our results demonstrate that antigens of both laboratory-adapted and clinical Mtb strains are stimulating factors for murine and human CXCR6+ NK cells. Future studies evaluating the role of CXCR6+ NK cells during TB are warranted.

Molecular Markers of Regulatory T Cells in Cancer Immunotherapy with Special Focus on Acute Myeloid Leukemia (AML) - A Systematic Review

The next-generation immunotherapy can only be effective if researchers have an in-depth understanding of the function and regulation of Treg cells in antitumor immunity combined with the discovery of new immunity targets. This can enhance clinical efficacy of future and novel therapies and reduces any adverse reactions arising from the latter. This review discusses tumor treatment strategies using regulatory T (Treg) cell therapy in a Tumor Microenvironment (TME). It also discusses factors affecting TME instability as well as relevant treatments to prevent future immune disorders. It is prognosticated that PD-1 inhibitors are risky and their adverse effects should be taken into account when they are administered to treat Acute Myeloid Leukemia (AML), lung adenocarcinoma, and prostate adenocarcinoma. In contrast, Treg molecular markers FoxP3 and CD25 analyzed here have stronger expression in almost all kinds of cancers compared with normal people. However, CD25 inhibitors are more effective compared to FoxP3 inhibitors, especially in combination with TGF-β blockade, in predicting patient survival. According to the data obtained from the Cancer Genome Atlas, we then concentrate on AML immunotherapy and discuss different therapeutic strategies including anti-CD25/IL-2, anti-CTLA-4, anti-IDO, antityrosine kinase receptor, and anti-PI3K therapies and highlight the recent advances and clinical achievements in AML immunotherapy. In order to prognosticate the risk and adverse effects of key target inhibitors (namely against CTLA-4, FoxP3, CD25, and PD-1), we finally analyzed and compared the Cancer Genome Atlas derived from ten common cancers. This review shows that Treg cells are strongly increased in AML and the comparative review of key markers shows that Tregbased immunotherapy is not effective for all kinds of cancer. Therefore, blocking CD25(+)FoxP3(+) Treg cells is suggested in AML more than other kinds of cancer; meanwhile, Treg markers studied in other cancers have also great lessons for AML immunotherapy.

H3K4me1 Supports Memory-like NK Cells Induced by Systemic Inflammation

Natural killer (NK) cells are unique players in innate immunity and, as such, an attractive target for immunotherapy. NK cells display immune memory properties in certain models, but the long-term status of NK cells following systemic inflammation is unknown. Here we show that following LPS-induced endotoxemia in mice, NK cells acquire cell-intrinsic memory-like properties, showing increased production of IFNγ upon specific secondary stimulation. The NK cell memory response is detectable for at least 9 weeks and contributes to protection from E. coli infection upon adoptive transfer. Importantly, we reveal a mechanism essential for NK cell memory, whereby an H3K4me1-marked latent enhancer is uncovered at the ifng locus. Chemical inhibition of histone methyltransferase activity erases the enhancer and abolishes NK cell memory. Thus, NK cell memory develops after endotoxemia in a histone methylation-dependent manner, ensuring a heightened response to secondary stimulation.

Targeting Unconventional Host Components for Vaccination-Induced Protection Against TB

The current tuberculosis (TB) vaccine, Bacille Calmette-Guerin (BCG), is effective in preventing TB in young children but was developed without a basic understanding of human immunology. Most modern TB vaccine candidates have targeted CD4⁺ T cell responses, thought to be important for protection against TB disease, but not known to be sufficient or critical for protection. Advances in knowledge of host responses to TB afford opportunities for developing TB vaccines that target immune components not conventionally considered. Here, we describe the potential of targeting NK cells, innate immune training, B cells and antibodies, and Th17 cells in novel TB vaccine development. We also discuss attempts to target vaccine immunity specifically to the lung, the primary disease site in humans.

Immune memory characteristics of innate lymphoid cells

PURPOSE OF REVIEW

Immune memory is essential for host defense against invaders and it is also used as a basis for vaccine development. For these reasons, it is crucial to understand its molecular basis. In this review, we describe recent findings on memory characteristics of innate-like lymphocytes and its contribution to host protection.(Figure is included in full-text article.) RECENT FINDINGS: In addition to adaptive immune cells, innate cells are also able to mount memory responses through a process called 'trained immunity.' Importantly, the lymphoid lineage is not restricted to cells carrying specific T-cell or B-cell receptors, but include cells with germline-encoded receptors. Recent studies show that these innate-like lymphocytes are able to generate efficient recall responses to reinfection. In different circumstances and depending on the cell type, innate-like lymphocyte memory can be antigen-specific or unspecific. Epigenetic changes accompany the generation of memory in these cells, but are still poorly defined.

SUMMARY

Immune memory is not restricted to antigen-specific cells, but also encompass different populations of innate immune cells. Innate-like lymphocytes embrace features of both innate and adaptive immune memory, and thus bridge adaptive and innate immune characteristics.

Superior Expansion and Cytotoxicity of Human Primary NK and CAR-NK Cells from Various Sources via Enriched Metabolic Pathways

Clinical success of chimeric antigen receptor (CAR) T cell immunotherapy requires the engineering of autologous T cells, which limits the broader implementation of CAR cell therapy. The development of allogeneic and universal cell products will significantly broaden their application and reduce costs. Allogeneic natural killer (NK) cells can be used for universal CAR immunotherapy. Here, we develop an alternative approach for the rapid expansion of primary NK and CAR-NK cells with superior expansion capability and in vivo cytotoxicity from various sources (including peripheral blood, cord blood, and tumor tissue). We apply a human B-lymphoblastoid cell-line 721.221 (hereinafter, 221)-based artificial feeder cell system with membrane-bound interleukin 21 (mIL-21) to propagate NK and CAR-NK cells. The expansion capability, purity, and cytotoxicity of NK cells expanded with 221-mIL-21 feeder cells are superior to that of conventional K562-mIL-21 feeder cells. RNA sequencing (RNA-seq) data show that 221-mIL-21 feeder cell-expanded NK cells display a less differentiated, non-exhausted, limited fratricidal, memory-like phenotype correlated with enriched metabolic pathways, which explains underlying mechanisms. Thus, “off-the-shelf” NK and CAR-NK cells with superior functionalities and expansion using a genetically modified 221-mIL-21 feeder cell expansion system will greatly support clinical use of NK immunotherapy.

Precision medicine in the clinical management of respiratory tract infections including multidrug-resistant tuberculosis: learning from innovations in immuno-oncology

PURPOSE OF REVIEW

In the light of poor management outcomes of antibiotic-resistant respiratory tract infection (RTI)-associated sepsis syndrome and multidrug-resistant tuberculosis (MDR-TB), new management interventions based on host-directed therapies (HDTs) are warranted to improve morbidity, mortality and long-term functional outcomes. We review developments in potential HDTs based on precision cancer therapy concepts applicable to RTIs including MDR-TB.

RECENT FINDINGS

Immune reactivity, tissue destruction and repair processes identified during studies of cancer immunotherapy share common pathogenetic mechanisms with RTI-associated sepsis syndrome and MDR-TB. T-cell receptors (TCRs) and chimeric antigen receptors targeting pathogen-specific or host-derived mutated molecules (major histocompatibility class-dependent/ major histocompatibility class-independent) can be engineered for recognition by TCR γδ and natural killer (NK) cells. T-cell subsets and, more recently, NK cells are shown to be host-protective. These cells can also be activated by immune checkpoint inhibitor (ICI) or derived from allogeneic sources and serve as potential for improving clinical outcomes in RTIs and MDR-TB.

SUMMARY

Recent developments of immunotherapy in cancer reveal common pathways in immune reactivity, tissue destruction and repair. RTIs-related sepsis syndrome exhibits mixed immune reactions, making cytokine or ICI therapy guided by robust biomarker analyses, viable treatment options.

Characterization and bioactivity of grass carp (Ctenopharyngodon idella) interleukin-21: Inducible production and involvement in inflammatory regulation

In mammals, interleukin 21 (IL-21) is a broad pleiotropic cytokine that plays critical roles in the development of several inflammatory and autoimmune diseases. In fish, functional information of Il-21 is limited, and its role in immune response is largely unknown. In the present study, we cloned a coding sequence of grass carp (Ctenopharyngodon idella) il21 gene (gcil21). To characterize the release patterns and biological activity of gcIl-21, we prepared recombinant gcIl-21 (rgcIl-21) and obtained the polyclonal antibody with gcIl-21 specificity. Western blotting analysis showed that in grass carp head kidney leukocytes (HKLs), gcIl-21 was undetected in culture supernatant of untreated cells but drastically induced by heat-killed Aeromonas hydrophila (A. hydrophila), uncovering the release features of gcIl-21 and its possible involvement in immune response. Subsequent functional experiments revealed that rgcIl-21 did not affect the mRNA expression of grass carp il1b and tgfb, but induced a strong expression of grass carp il10, and to a lesser extent of grass carp tnfa in HKLs, suggesting a dominant effect of gcIl-21 in modulating Il-10 signaling as seen in rainbow trout and mammals. Furthermore, in vivo studies showed that intraperitoneal injection of rgcIl-21 was able to increase the survival rate of grass carp infected with live A. hydrophila, and reduce the pathological responses caused by the same pathogenic bacteria in head kidney and intestine. Taken together, these results for the first time revealed the close relationship of fish Il-21 production and function with inflammatory responses, and highlighted its anti-bacterial and anti-inflammatory ability, thereby providing a new insight into host defense mechanisms in fish.

Memory and Memory-Like NK Cell Responses to Microbial Pathogens

NK cells are cytotoxic lymphocytes that provide systemic defense against pathogens and malignancy. Although historically considered cells of the innate immune system, NK cells are now known to be capable of memory or memory-like immune responses in certain settings. Memory NK responses were initially reported over a decade ago in studies involving mouse models of cytomegalovirus infection and delayed-type hypersensitivity reactions to chemical haptens and viral antigens. Since then, a growing body of literature suggests that memory or memory-like NK cell responses may occur in a broader range of immunological settings, including in response to various viral and bacterial infections, and some immunization protocols. Memory-like NK cell responses have also now been reported in humans and non-human primates. Here, we summarize recent studies demonstrating memory or memory-like responses by NK cells in settings of infection and immunization against infectious agents.

Distinct Human NK Cell Phenotypes and Functional Responses to Mycobacterium tuberculosis in Adults From TB Endemic and Non-endemic Regions

Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis (TB), which leads to an estimated 1. 5 million deaths worldwide each year. Although the immune correlates of protection against Mtb infection and TB disease have not been well-defined, natural killer (NK) cells are increasingly recognized as a key component of the innate immune response to Mtb and as a link between innate and adaptive immunity. In this study, we evaluated NK cell phenotypic and functional profiles in QuantiFERON-TB (QFT)⁺ and QFT⁻ adults in a TB endemic setting in Kisumu, Kenya, and compared their NK cell responses to those of Mtb-naïve healthy adult controls in the U.S. We used flow cytometry to define the phenotypic profile of NK cells and identified distinct CD56^dim NK cell phenotypes that differentiated the Kenyan and U.S. groups. Additionally, among Kenyan participants, NK cells from QFT⁺ individuals with latent Mtb infection (LTBI) were characterized by significant downregulation of the natural cytotoxicity receptor NKp46 and the inhibitory receptor TIGIT, compared with QFT⁻ individuals. Moreover, the distinct CD56^dim phenotypic profiles in Kenyan individuals correlated with dampened NK cell responses to tumor cells and diminished activation, degranulation, and cytokine production following stimulation with Mtb antigens, compared with Mtb-naïve U.S. healthy adult controls. Taken together, these data provide evidence that the phenotypic and functional profiles of NK cells are modified in TB endemic settings and will inform future studies aimed at defining NK cell-mediated immune correlates that may be protective against acquisition of Mtb infection and progression to TB disease.

Japanese flounder Paralichthys olivaceus interleukin 21 induces inflammatory response and plays a vital role in the immune defense against bacterial pathogen

Interleukin (IL)-21 is a pleiotropic cytokine and plays a vital role in immunity. In the current study, we examined the immune function of Japanese flounder Paralichthys olivaceus IL-21 (PoIL-21). PoIL-21 shares moderate (25.17%-46.25%) sequence identities with other teleost IL-21. PoIL-21 expression occurred in multiple tissues, especially intestine, and was regulated by bacterial infection in a time dependent manner. PoIL-21 was secreted by peripheral blood leukocytes (PBL) upon LPS stimulation. Recombinant PoIL-21 (rPoIL-21) bound to a wide range of Gram-negative and Gram-positive bacteria and inhibited the growth of the fish bacterial pathogen Streptococcus iniae. rPoIL-21 also interacted with PBL, resulting in enhanced cell proliferation, ROS production, and expression of IL-1β, TNF-α, CD8β, T-bet, PoIL-21, PoIL-21 receptor, and STAT. Consequently, the presence of rPoIL-21 significantly reduced bacterial infection in PBL. In vivo study showed that rPoIL-21 upregulated the expression of inflammatory cytokines and PoIL-21. Taken together, these results indicate that PoIL-21 is an inducible, secreted cytokine with a broad range of binding capacities and plays an important role in the regulation of anti-bacterial immunity.