Anti-viral activity induced by culturing lymphocytes with tumor-derived or virus-transformed cells. Enhancement of human natural killer cell activity by interferon and antagonistic inhibition of susceptibility of target cells to lysis

Interferon-I modulation and natural products: Unraveling mechanisms and therapeutic potential in severe COVID-19

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to pose a significant global public health threat, particularly to older adults, pregnant women, and individuals with underlying chronic conditions. Dysregulated immune responses to SARS-CoV-2 infection are believed to contribute to the progression of COVID-19 in severe cases. Previous studies indicates that a deficiency in type I interferon (IFN-I) immunity accounts for approximately 15 %-20 % of patients with severe pneumonia caused by COVID-19, highlighting the potential therapeutic importance of modulating IFN-I signals. Natural products and their derivatives, due to their structural diversity and novel scaffolds, play a crucial role in drug discovery. Some of these natural products targeting IFN-I have demonstrated applications in infectious diseases and inflammatory conditions. However, the immunomodulatory potential of IFN-I in critical COVID-19 pneumonia and the natural compounds regulating the related signal pathway remain not fully understood. In this review, we offer a comprehensive assessment of the association between IFN-I and severe COVID-19, exploring its mechanisms and integrating information on natural compounds effective for IFN-I regulation. Focusing on the primary targets of IFN-I, we also summarize the regulatory mechanisms of natural products, their impact on IFNs, and their therapeutic roles in viral infections. Collectively, by synthesizing these findings, our goal is to provide a valuable reference for future research and to inspire innovative treatment strategies for COVID-19.

Pharmacogenomics of coronary artery response to intravenous gamma globulin in kawasaki disease

Kawasaki disease (KD) is a multisystem inflammatory illness of infants and young children that can result in acute vasculitis. The mechanism of coronary artery aneurysms (CAA) in KD despite intravenous gamma globulin (IVIG) treatment is not known. We performed a Whole Genome Sequencing (WGS) association analysis in a racially diverse cohort of KD patients treated with IVIG, both using AHA guidelines. We defined coronary aneurysm (CAA) (N = 234) as coronary z ≥ 2.5 and large coronary aneurysm (CAA/L) (N = 92) as z ≥ 5.0. We conducted logistic regression models to examine the association of genetic variants with CAA/L during acute KD and with persistence >6 weeks using an additive model between cases and 238 controls with no CAA. We adjusted for age, gender and three principal components of genetic ancestry. The top significant variants associated with CAA/L were in the intergenic regions (rs62154092 p < 6.32E-08 most significant). Variants in SMAT4, LOC100127, PTPRD, TCAF2 and KLRC2 were the most significant non-intergenic SNPs. Functional mapping and annotation (FUMA) analysis identified 12 genomic risk loci with eQTL or chromatin interactions mapped to 48 genes. Of these NDUFA5 has been implicated in KD CAA and MICU and ZMAT4 has potential functional implications. Genetic risk score using these 12 genomic risk loci yielded an area under the receiver operating characteristic curve (AUC) of 0.86. This pharmacogenomics study provides insights into the pathogenesis of CAA/L in IVIG-treated KD and shows that genomics can help define the cause of CAA/L to guide management and improve risk stratification of KD patients.

Pharmacogenomics of Coronary Artery Response to Intravenous Gamma Globulin in Kawasaki Disease

Background

Kawasaki disease (KD) is a multisystem inflammatory illness of infants and young children that can result in acute vasculitis. The pathological walls of afflicted coronary arteries show propensity for forming thrombosis and aneurysms. The mechanism of coronary artery aneurysms (CAA) despite intravenous gamma globulin (IVIG) treatment is not known.

Methods

We performed a Whole Genome Sequencing (WGS) association analysis in a racially diverse cohort of KD patients treated with IVIG, both using AHA guidelines. We defined coronary aneurysm (CAA) (N = 234) as coronary z>2.5 and large coronary aneurysm (CAA/L) (N = 92) as z>5.0. We conducted logistic regression models to examine the association of genetic variants with CAA/L during acute KD and with persistence >6 weeks using an additive model between cases and 238 controls with no CAA. We adjusted for age, gender and three principal components of genetic ancestry. We performed functional mapping and annotation (FUMA) analysis and further assessed the predictive risk score of genomic risk loci using the area under the receiver operating characteristic curve (AUC).

Results

The top significant variants associated with CAA/L were in the intergenic regions (rs62154092 p<6.32E-08 most significant). Variants in SMAT4, LOC100127 , PTPRD, TCAF2 and KLRC2 were the most significant non-intergenic SNPs. FUMA identified 12 genomic risk loci with eQTL or chromatin interactions mapped to 48 genes. Of these NDUFA5 has been implicated in KD CAA and MICU and ZMAT4 has potential functional implications. Genetic risk score using these 12 genomic risk loci yielded an AUC of 0.86.

Conclusions

This pharmacogenomics study provides insights into the pathogenesis of CAA/L in IVIG-treated KD patients. We have identified multiple novel SNPs associated with CAA/L and related genes with potential functional implications. The study shows that genomics can help define the cause of CAA/L to guide management and improve risk stratification of KD patients.

Single-cell functional genomics reveals determinants of sensitivity and resistance to natural killer cells in blood cancers

Cancer cells can evade natural killer (NK) cell activity, thereby limiting anti-tumor immunity. To reveal genetic determinants of susceptibility to NK cell activity, we examined interacting NK cells and blood cancer cells using single-cell and genome-scale functional genomics screens. Interaction of NK and cancer cells induced distinct activation and type I interferon (IFN) states in both cell types depending on the cancer cell lineage and molecular phenotype, ranging from more sensitive myeloid to less sensitive B-lymphoid cancers. CRISPR screens in cancer cells uncovered genes regulating sensitivity and resistance to NK cell-mediated killing, including adhesion-related glycoproteins, protein fucosylation genes, and transcriptional regulators, in addition to confirming the importance of antigen presentation and death receptor signaling pathways. CRISPR screens with a single-cell transcriptomic readout provided insight into underlying mechanisms, including regulation of IFN-γ signaling in cancer cells and NK cell activation states. Our findings highlight the diversity of mechanisms influencing NK cell susceptibility across different cancers and provide a resource for NK cell-based therapies.

Immune modulation in chronic myeloid leukaemia patients treated with nilotinib and interferon-alpha

The addition of interferon to tyrosine kinase inhibitors (TKIs), to improve deep molecular response (DMR) and potentially treatment-free remission (TFR) rates in chronic-phase chronic myeloid leukaemia (CP-CML) patients is under active investigation. However, the immunobiology of this combination is poorly understood. We performed a comprehensive longitudinal assessment of immunological changes in CML patients treated with nilotinib and interferon-alpha (IFN-α) within the ALLG CML11 trial (n = 12) or nilotinib alone (n = 17). We demonstrate that nilotinib+IFN transiently reduced absolute counts of natural killer (NK) cells, compared with nilotinib alone. Furthermore, CD16+ -cytolytic and CD57+ CD62L- -mature NK cells were transiently reduced during IFN therapy, without affecting NK-cell function. IFN transiently increased cytotoxic T-lymphocyte (CTL) responses to leukaemia-associated antigens (LAAs) proteinase-3, BMI-1 and PRAME; and had no effect on regulatory T cells, or myeloid-derived suppressor cells. Patients on nilotinib+IFN who achieved MR4.5 by 12 months had a significantly higher proportion of NK cells expressing NKp46, NKp30 and NKG2D compared with patients not achieving this milestone. This difference was not observed in the nilotinib-alone group. The addition of IFN to nilotinib drives an increase in NK-activating receptors, CTLs responding to LAAs and results in transient immune modulation, which may influence earlier DMR, and its effect on long-term outcomes warrants further investigation.

Delivery of Immunostimulatory Cargos in Nanocarriers Enhances Anti-Tumoral Nanovaccine Efficacy

Finding a long-term cure for tumor patients still represents a major challenge. Immunotherapies offer promising therapy options, since they are designed to specifically prime the immune system against the tumor and modulate the immunosuppressive tumor microenvironment. Using nucleic-acid-based vaccines or cellular vaccines often does not achieve sufficient activation of the immune system in clinical trials. Additionally, the rapid degradation of drugs and their non-specific uptake into tissues and cells as well as their severe side effects pose a challenge. The encapsulation of immunomodulatory molecules into nanocarriers provides the opportunity of protected cargo transport and targeted uptake by antigen-presenting cells. In addition, different immunomodulatory cargos can be co-delivered, which enables versatile stimulation of the immune system, enhances anti-tumor immune responses and improves the toxicity profile of conventional chemotherapeutic agents.

CD39/CD73 Dysregulation of Adenosine Metabolism Increases Decidual Natural Killer Cell Cytotoxicity: Implications in Unexplained Recurrent Spontaneous Abortion

Unexplained recurrent spontaneous abortion (URSA) is believed to be associated with impaired immunosuppression at the maternal-fetal interface, but the detailed molecular mechanism remains unclear. The ATP-adenosine metabolic pathway regulated by CD39/CD73 has recently been recognized to be important in immunosuppression. This study aimed to investigate the regulation of decidual natural killer (dNK) cells and fetal extravillous trophoblast (EVT) cells by CD39 and CD73 in URSA, as well as the possible regulatory mechanism of CD39/CD73 via the TGF-β-mTOR-HIF-1α pathway using clinical samples and cell models. Fewer CD39⁺ and CD73⁺ cells were found in the URSA decidual and villous tissue, respectively. Inhibition of CD39 on dNK cells transformed the cells to an activated state with increased toxicity and decreased apoptosis, and changed their cytokine secretion, leading to impaired invasion and proliferation of the co-cultured HTR8/SVneo cells. Similarly, inhibition of CD73 on HTR8/SVneo cells decreased the adenosine concentration in the cell culture media, increased the proportion of CD107a⁺ dNK cells, and decreased the invasion and proliferation capabilities of the HTR8/SVneo cells. In addition, transforming growth factor-β (TGF-β) triggered phosphorylation of mammalian target of rapamycin (mTOR) and Smad2/Smad3, which subsequently activated hypoxia-inducible factor-1α (HIF-1α) to induce the CD73 expression on the HTR8/SVneo cells. In summary, reduced numbers of CD39⁺ and CD73⁺ cells at the maternal-fetal interface, which may be due to downregulated TGF-β-mTOR-HIF-1α pathway, results in reduced ATP-adenosine metabolism and increased dNK cytotoxicity, and potentially contributes to URSA occurrences.

Myasthenia Gravis: An Acquired Interferonopathy?

Myasthenia gravis (MG) is a rare autoimmune disease mediated by antibodies against components of the neuromuscular junction, particularly the acetylcholine receptor (AChR). The thymus plays a primary role in AChR-MG patients. In early-onset AChR-MG and thymoma-associated MG, an interferon type I (IFN-I) signature is clearly detected in the thymus. The origin of this chronic IFN-I expression in the thymus is not yet defined. IFN-I subtypes are normally produced in response to viral infection. However, genetic diseases called interferonopathies are associated with an aberrant chronic production of IFN-I defined as sterile inflammation. Some systemic autoimmune diseases also share common features with interferonopathies. This review aims to analyze the pathogenic role of IFN-I in these diseases as compared to AChR-MG in order to determine if AChR-MG could be an acquired interferonopathy.

The changing role of natural killer cells in cancer metastasis

Natural killer (NK) cells are innate immune cells that are critical to the body's antitumor and antimetastatic defense. As such, novel therapies are being developed to utilize NK cells as part of a next generation of immunotherapies to treat patients with metastatic disease. Therefore, it is essential for us to examine how metastatic cancer cells and NK cells interact with each other throughout the metastatic cascade. In this Review, we highlight the recent body of work that has begun to answer these questions. We explore how the unique biology of cancer cells at each stage of metastasis alters fundamental NK cell biology, including how cancer cells can evade immunosurveillance and co-opt NK cells into cells that promote metastasis. We also discuss the translational potential of this knowledge.

The efficacy of probiotics on virus titres and antibody production in virus diseases: A systematic review on recent evidence for COVID-19 treatment

BACKGROUND & AIMS

There are some studies indicating the effects of probiotic-containing foods or supplements on viral diseases. We aimed to conduct a rapid review of probiotics with specific emphasis on their potential for early administration in patients at greater risk of SARS-CoV-2 infection.

METHODS

We searched on PubMed, EMBASE, Google Scholar, Science Direct, Scopus and Web of Science up to February 2021 to identify interventional and observational studies documenting the effects of probiotics strains on interleukins, virus titers, and antibody production with a focus on probiotic-containing foods (PROSPERO Registration ID. CRD42020181453) RESULTS: From a total of 163 records, 21 studies were classified into three domains based on the efficacy of probiotics on 1) the level of interleukins (n = 7), 2) virus titers (n = 2), and 3) interferon (IFN) and antibody production (n = 12). The suppuration of pro-inflammatory interleukins and type I INF production seemed to be the main anti-viral effect of probiotics. Nine studies also indicated the beneficial effects of probiotics and fermented foods on viral diseases.

CONCLUSION

Based on evidence, some probiotic strains may be useful in viral infections; randomized trials are needed to confirm these findings.

The transcription factor reservoir and chromatin landscape in activated plasmacytoid dendritic cells

Background

Transcription factors (TFs) control gene expression by direct binding to regulatory regions of target genes but also by impacting chromatin landscapes and modulating DNA accessibility for other TFs. In recent years several TFs have been defined that control cell fate decisions and effector functions in the immune system. Plasmacytoid dendritic cells (pDCs) are an immune cell type with the unique capacity to produce high amounts of type I interferons quickly in response to contact with viral components. Hereby, this cell type is involved in anti-infectious immune responses but also in the development of inflammatory and autoimmune diseases. To date, the global TF reservoir in pDCs early after activation remains to be fully characterized.

Results

To fill this gap, we have performed a comprehensive analysis in naïve versus TLR9-activated murine pDCs in a time course study covering early timepoints after stimulation (2 h, 6 h, 12 h) integrating gene expression (RNA-Seq) and chromatin landscape (ATAC-Seq) studies. To unravel the biological processes underlying the changes in TF expression on a global scale gene ontology (GO) analyses were performed. We found that 70% of all genes annotated as TFs in the mouse genome (1014 out of 1636) are expressed in pDCs for at least one stimulation time point and are covering a wide range of TF classes defined by their specific DNA binding mechanisms. GO analysis revealed involvement of TLR9-induced TFs in epigenetic modulation, NFκB and JAK-STAT signaling, and protein production in the endoplasmic reticulum. pDC activation predominantly “turned on” the chromatin regions associated with TF genes. Our in silico analyses pointed at the AP-1 family of TFs as less noticed but possibly important players in these cells after activation. AP-1 family members exhibit (1) increased gene expression, (2) enhanced chromatin accessibility in their promoter region, and (3) a TF DNA binding motif that is globally enriched in genomic regions that were found more accessible in pDCs after TLR9 activation.

Conclusions

In this study we define the complete set of TLR9-regulated TFs in pDCs. Further, this study identifies the AP-1 family of TFs as potentially important but so far less well characterized regulators of pDC function.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12863-021-00991-2.

STING Agonists as Cancer Therapeutics

The interrogation of intrinsic and adaptive resistance to cancer immunotherapy has identified lack of antigen presentation and type I interferon signaling as biomarkers of non-T-cell-inflamed tumors and clinical progression. A myriad of pre-clinical studies have implicated the cGAS/stimulator of interferon genes (STING) pathway, a cytosolic DNA-sensing pathway that drives activation of type I interferons and other inflammatory cytokines, in the host immune response against tumors. The STING pathway is also increasingly understood to have other anti-tumor functions such as modulation of the vasculature and augmentation of adaptive immunity via the support of tertiary lymphoid structure development. Many natural and synthetic STING agonists have entered clinical development with the first generation of intra-tumor delivered cyclic dinucleotides demonstrating safety but only modest systemic activity. The development of more potent and selective STING agonists as well as novel delivery systems that would allow for sustained inflammation in the tumor microenvironment could potentially augment response rates to current immunotherapy approaches and overcome acquired resistance. In this review, we will focus on the latest developments in STING-targeted therapies and provide an update on the clinical development and application of STING agonists administered alone, or in combination with immune checkpoint blockade or other approaches.

Dual effects of natural killer cells in transplantation for leukemia

Natural killer (NK) cells were originally considered to belong to the innate immune system to play a protective role against tumor cells and viral infections. In human, they can recognize self and non-self HLA class 1 as their ligand. So, analyzing the outcomes of allogeneic hematopoietic stem cell transplantation is a good opportunity to know the antitumor effects and regulatory effects of NK cells through HLA class 1 matching and mismatching of donor and recipient. In this review, I looked back on the main analysis results of the past transplants, summarized our reports consisting of many cases in a single ethnic, and showed that NK cells might work oppositely depending on the type of leukemia. New treatment strategies based on these concepts may offer individualized treatment options and ultimately increase offer the possibility of a cure for patients with leukemia.

A New Hope for CD56negCD16pos NK Cells as Unconventional Cytotoxic Mediators: An Adaptation to Chronic Diseases

Natural Killer (NK) cells play an essential role in antiviral and anti-tumoral immune responses. In peripheral blood, NK cells are commonly classified into two major subsets: CD56^brightCD16^neg and CD56^dimCD16^pos despite the characterization of a CD56^negCD16^pos subset 25 years ago. Since then, several studies have described the prevalence of an CD56^negCD16^pos NK cell subset in viral non-controllers as the basis for their NK cell dysfunction. However, the mechanistic basis for their cytotoxic impairment is unclear. Recently, using a strict flow cytometry gating strategy to exclude monocytes, we reported an accumulation of CD56^negCD16^pos NK cells in Plasmodium falciparum malaria-exposed children and pediatric cancer patients diagnosed with endemic Burkitt lymphoma (eBL). Here, we use live-sorted cells, histological staining, bulk RNA-sequencing and flow cytometry to confirm that this CD56^negCD16^pos NK cell subset has the same morphological features as the other NK cell subsets and a similar transcriptional profile compared to CD56^dimCD16^pos NK cells with only 120 genes differentially expressed (fold change of 1.5, p < 0.01 and FDR<0.05) out of 9235 transcripts. CD56^negCD16^pos NK cells have a distinct profile with significantly higher expression of MPEG1 (perforin 2), FCGR3B (CD16b), FCGR2A, and FCGR2B (CD32A and B) as well as CD6, CD84, HLA-DR, LILRB1/2, and PDCD1 (PD-1), whereas Interleukin 18 (IL18) receptor genes (IL18RAP and IL18R1), cytotoxic genes such as KLRF1 (NKp80) and NCR1 (NKp46), and inhibitory HAVCR2 (TIM-3) are significantly down-regulated compared to CD56^dimCD16^pos NK cells. Together, these data confirm that CD56^negCD16^pos cells are legitimate NK cells, yet their transcriptional and protein expression profiles suggest their cytotoxic potential is mediated by pathways reliant on antibodies such as antibody-dependent cell cytotoxicity (ADCC), antibody-dependent respiratory burst (ADRB), and enhanced by complement receptor 3 (CR3) and FAS/FASL interaction. Our findings support the premise that chronic diseases induce NK cell modifications that circumvent proinflammatory mediators involved in direct cytotoxicity. Therefore, individuals with such altered NK cell profiles may respond differently to NK-mediated immunotherapies, infections or vaccines depending on which cytotoxic mechanisms are being engaged.

Harnessing cancer immunotherapy during the unexploited immediate perioperative period

The immediate perioperative period (days before and after surgery) is hypothesized to be crucial in determining long-term cancer outcomes: during this short period, numerous factors, including excess stress and inflammatory responses, tumour-cell shedding and pro-angiogenic and/or growth factors, might facilitate the progression of pre-existing micrometastases and the initiation of new metastases, while simultaneously jeopardizing immune control over residual malignant cells. Thus, application of anticancer immunotherapy during this critical time frame could potentially improve patient outcomes. Nevertheless, this strategy has rarely been implemented to date. In this Perspective, we discuss apparent contraindications for the perioperative use of cancer immunotherapy, suggest safe immunotherapeutic and other anti-metastatic approaches during this important time frame and specify desired characteristics of such interventions. These characteristics include a rapid onset of immune activation, avoidance of tumour-promoting effects, no or minimal increase in surgical risk, resilience to stress-related factors and minimal induction of stress responses. Pharmacological control of excess perioperative stress-inflammatory responses has been shown to be clinically feasible and could potentially be combined with immune stimulation to overcome the direct pro-metastatic effects of surgery, prevent immune suppression and enhance immunostimulatory responses. Accordingly, we believe that certain types of immunotherapy, together with interventions to abrogate stress-inflammatory responses, should be evaluated in conjunction with surgery and, for maximal effectiveness, could be initiated before administration of adjuvant therapies. Such strategies might improve the overall success of cancer treatment.

Virus-induced natural killer cell lysis of T cell subsets

In addition to direct anti-viral activity, NK cells regulate viral pathogenesis by virtue of their cytolytic attack on activated CD4 and CD8 T cells. To gain insight into which differentiated T cell subsets are preferred NK targets, transgenic T cells were differentiated in vitro into Th0, Th1, Th2, Th17, Treg, Tc1, and Tc2 effector cells and then tested for lysis by enriched populations of lymphocytic choriomeningitis virus (LCMV)-induced activated NK cells. There was a distinct hierarchy of cytotoxicity in vitro and in vivo, with Treg, Th17, and Th2 cells being more sensitive and Th0 and Th1 cells more resistant. Some distinctions between in vitro vs in vivo generated T cells were explainable by type 1 interferon induction of class 1 histocompatibility antigens on the effector T cell subsets. NK receptor (NKR)-deficient mice and anti-NKR antibody studies identified no one essential NKR for killing, though there could be redundancies.

Probiotics and Paraprobiotics in Viral Infection: Clinical Application and Effects on the Innate and Acquired Immune Systems

Recently, the risk of viral infection has dramatically increased owing to changes in human ecology such as global warming and an increased geographical movement of people and goods. However, the efficacy of vaccines and remedies for infectious diseases is limited by the high mutation rates of viruses, especially, RNA viruses. Here, we comprehensively review the effectiveness of several probiotics and paraprobiotics (sterilized probiotics) for the prevention or treatment of virally-induced infectious diseases. We discuss the unique roles of these agents in modulating the cross-talk between commensal bacteria and the mucosal immune system. In addition, we provide an overview of the unique mechanism by which viruses are eliminated through the stimulation of type 1 interferon production by probiotics and paraprobiotics via the activation of dendritic cells. Although further detailed research is necessary in the future, probiotics and/or paraprobiotics are expected to be among the rational adjunctive options for the treatment of various viral diseases.

Plasmacytoid dendritic cell dysfunction caused by heat stress is improved by administration of Lactococcus lactis strain plasma in mice

Plasmacytoid dendritic cells (pDCs) are crucial in anti-viral immunity, acting as regulators in both adaptive and innate immunity. In this study, brief heat stress caused a decrease in splenic pDC activity in mice. Administration of Lactococcus lactis strain Plasma (LC-Plasma) significantly suppressed the decrease in pDC activity and IFN-α production. Abbreviations: LC-Plasma: Lactococcus lactis strain Plasma; LAB: lactic acid bacteria; pDC: plasmacytoid dendritic cell; IFN: interferons; mDC: myeloid dendritic cells.

The immunomodulatory-drug, lenalidomide, sustains and enhances interferon-α production by human plasmacytoid dendritic cells

Background: Lenalidomide (LEN), an immunomodulatory drug (IMiD), is currently used for treatment of multiple myeloma (MM). LEN potentiates T cell and natural killer cell functions. However, the cellular and molecular mechanisms underlying the immunomodulatory effects of LEN remain unclear. We focused on the effects of LEN on human plasmacytoid dendritic cells (pDCs), which are the major source of interferon (IFN)-α in the blood and play a central role in innate immune responses. Results: We found that bortezomib, a proteasome inhibitor used to treat MM, killed pDCs but that 0.1-3 μM LEN (covering clinical plasma concentration range) did not affect pDC survival or CD86 expression. Bortezomib inhibited pDC-derived IFN-α production in a dose-dependent fashion, but 0.1-3 µM LEN sustained pDC-derived IFN-α production when stimulated with an optimal concentration of CpG-ODN 2216 (3 μM). In pDCs stimulated with a low concentration of CpG-ODN (0.1 μM), LEN enhanced IFN-α production. These results indicated that LEN, when used at a clinically relevant concentration, can potentially enhance IFN-α production by pDCs. Conclusion: Collectively, our findings unveiled a novel target of LEN and extend the repertoire of the drug's known immunomodulatory effects. These effects may explain the low incidence of herpes zoster viral infection observed during LEN treatment compared with bortezomib treatment. LEN may function as an IMiD affecting a wide array of immune cells, including pDCs, leading to amplification of a positive immune axis able to eliminate MM cells.

Sources of Type I Interferons in Infectious Immunity: Plasmacytoid Dendritic Cells Not Always in the Driver's Seat

Type I Interferons (IFNs) are hallmark cytokines produced in immune responses to all classes of pathogens. Type I IFNs can influence dendritic cell (DC) activation, maturation, migration, and survival, but also directly enhance natural killer (NK) and T/B cell activity, thus orchestrating various innate and adaptive immune effector functions. Therefore, type I IFNs have long been considered essential in the host defense against virus infections. More recently, it has become clear that depending on the type of virus and the course of infection, production of type I IFN can also lead to immunopathology or immunosuppression. Similarly, in bacterial infections type I IFN production is often associated with detrimental effects for the host. Although most cells in the body are thought to be able to produce type I IFN, plasmacytoid DCs (pDCs) have been termed the natural "IFN producing cells" due to their unique molecular adaptations to nucleic acid sensing and ability to produce high amounts of type I IFN. Findings from mouse reporter strains and depletion experiments in in vivo infection models have brought new insights and established that the role of pDCs in type I IFN production in vivo is less important than assumed. Production of type I IFN, especially the early synthesized IFNβ, is rather realized by a variety of cell types and cannot be mainly attributed to pDCs. Indeed, the cell populations responsible for type I IFN production vary with the type of pathogen, its tissue tropism, and the route of infection. In this review, we summarize recent findings from in vivo models on the cellular source of type I IFN in different infectious settings, ranging from virus, bacteria, and fungi to eukaryotic parasites. The implications from these findings for the development of new vaccination and therapeutic designs targeting the respectively defined cell types are discussed.

Poorly cytotoxic terminally differentiated CD56negCD16pos NK cells accumulate in Kenyan children with Burkitt lymphomas

Natural killer (NK) cells are critical for restricting viral infections and mediating tumor immunosurveillance. Epstein-Barr virus (EBV) and Plasmodium falciparum malaria are known risk factors for endemic Burkitt lymphoma (eBL), the most common childhood cancer in equatorial Africa. To date, the composition and function of NK cells have not been evaluated in eBL etiology or pathogenesis. Therefore, using multiparameter flow cytometry and in vitro killing assays, we compared NK cells from healthy children and children diagnosed with eBL in Kenya. We defined 5 subsets based on CD56 and CD16 expression, including CD56^negCD16^pos We found that licensed and terminally differentiated perforin-expressing CD56^negCD16^pos NK cells accumulated in eBL children, particularly in those with high EBV loads (45.2%) compared with healthy children without (6.07%) or with (13.5%) malaria exposure (P = .0007 and .002, respectively). This progressive shift in NK cell proportions was concomitant with fewer CD56^dimCD16^pos cells. Despite high MIP-1β expression, CD56^negCD16^pos NK cells had diminished cytotoxicity, with lower expression of activation markers NKp46, NKp30, and CD160 and the absence of TNF-α. Of note, the accumulation of poorly cytotoxic CD56^negCD16^pos NK cells resolved in long-term eBL survivors. Our study demonstrates impaired NK cell-mediated immunosurveillance in eBL patients but with the potential to restore a protective NK cell repertoire after cancer treatment. Characterizing NK cell dysfunction during coinfections with malaria and EBV has important implications for designing immunotherapies to improve outcomes for children diagnosed with eBL.

JAK/STAT proteins and their biological impact on NK cell development and function

NK cells are important early effectors in the innate immune response to a variety of viral infections and for elimination of tumor cells. The JAK/STAT signaling cascade is critical for NK cell development, maturation, survival, and proliferation, therefore, it is important to understand the role of this pathway in NK cell biology. Many cytokines can activate multiple JAK/STAT protein family members, creating a severe phenotype when mutations impair their function or expression. Here we discuss the impact of defective JAK/STAT signaling pathways on NK cell development, activation and cytotoxicity.

Modulation by Ifn-Gamma of the Metastatic Ability of Murine, Human, and H-2-Transfected Tumor Cells

Interferon-gamma (IFN-gamma) can enhance the experimental metastatic ability of B16 melanoma. The in vitro treatment with IFN-gamma of four clones derived from the murine mammary adenocarcinoma TS/A increased the number of lung colonies observed after intravenous injection in syngeneic mice. The spontaneous metastatic ability of these clones was not altered by the IFN-gamma pretreatment nor by daily intratumor injection of low-dose IFN-gamma. The experimental metastatic ability in nude mice of the human rhabdomyosarcoma cell line RD was decreased by in vitro pretreatment with IFN-gamma. To study the role played by major histocompatibility complex gene products in the IFN-gamma-mediated enhancement of B16 experimental metastasis, a mutant B16 clone, B78H1, was transfected with the H-2Kb gene. B78H1 cells are not capable of expressing H-2b even after treatment with IFN-gamma; IFN-gamma readily induced high levels of H-2Kb in a set of transfected clones, but did not enhance their experimental metastatic ability.

Long-term administration of pDC-Stimulative Lactococcus lactis strain decelerates senescence and prolongs the lifespan of mice

The decline in immune function caused by aging increases the risk of infectious diseases, tumorigeneses and chronic inflammation, resulting in accelerating senescence. We previously reported a lactic acid bacteria, Lactococcus lactis strain Plasma (synonym of Lactococcus lactis subsp. lactis JCM 5805, Lc-Plasma), that stimulates plasmacytoid dendritic cells (pDCs), which play a crucial role in phylaxis from viral infection. In this study, we investigated the anti-aging effects of long-term oral administration of Lc-Plasma in a senescence-accelerated mouse strain, SAMP6. Mice given Lc-Plasma showed a significant improvement in survival rate at 82 weeks and a decreased senescence score as compared with control mice throughout this study. Anatomic analysis at 82 weeks revealed that the frequency of altered hepatocellular foci was significantly lower, and the incidence of other pathological findings in the liver and lungs tended to be lower in Lc-Plasma mice than in control mice. Transcription level of the IL-1β gene in lungs also tended to be lower in Lc-Plasma mice. Furthermore, the thinning of skin and age-related decrease in muscle mass were also significantly suppressed in the Lc-Plasma group as compared with the control group. Consistent with these phenotypic features, pDCs activity was significantly higher in Lc-Plasma mice than in control mice. In conclusion, long-term administration of Lc-Plasma can decelerate senescence and prolong lifespan via maintenance of the immune system due to activation of pDCs.

Monocyte-Derived Signals Activate Human Natural Killer Cells in Response to Leishmania Parasites

Activated natural killer (NK) cells release interferon (IFN)-γ, which is crucial for the control of intracellular pathogens such as Leishmania. In contrast to experimental murine leishmaniasis, the human NK cell response to Leishmania is still poorly characterized. Here, we investigated the interaction of human blood NK cells with promastigotes of different Leishmania species (Leishmania major, Leishmania mexicana, Leishmania infantum, and Leishmania donovani). When peripheral blood mononuclear cells or purified NK cells and monocytes (all derived from healthy blood donors from Germany without a history of leishmaniasis) were exposed to promastigotes, NK cells showed increased surface expression of the activation marker CD69. The extent of this effect varied depending on the Leishmania species; differences between dermotropic and viscerotropic L. infantum strains were not observed. Upregulation of CD69 required direct contact between monocytes and Leishmania and was partly inhibitable by anti-interleukin (IL)-18. Unexpectedly, IL-18 was undetectable in most of the supernatants (SNs) of monocyte/parasite cocultures. Confocal fluorescence microscopy of non-permeabilized cells revealed that Leishmania-infected monocytes trans-presented IL-18 to NK cells. Native, but not heat-treated SNs of monocyte/Leishmania cocultures also induced CD69 on NK cells, indicating the involvement of a soluble heat-labile factor other than IL-18. A role for the NK cell-activating cytokines IL-1β, IL-2, IL-12, IL-15, IL-21, and IFN-α/β was excluded. The increase of CD69 was not paralleled by NK cell IFN-γ production or enhanced cytotoxicity. However, prior exposure of NK cells to Leishmania parasites synergistically increased their IFN-γ release in response to IL-12, which was dependent on endogenous IL-18. CD1c+ dendritic cells were identified as possible source of Leishmania-induced IL-12. Finally, we observed that direct contact between Leishmania and NK cells reduced the expression of CD56 mRNA and protein on NK cells. We conclude that Leishmania activate NK cells via trans-presentation of IL-18 by monocytes and by a monocyte-derived soluble factor. IL-12 is needed to elicit the IFN-γ-response of NK cells, which is likely to be an important component of the innate control of the parasite.

Epstein-Barr Virus-Specific Immune Control by Innate Lymphocytes

Epstein–Barr virus (EBV) is a potent B cell transforming pathogen in humans. In most persistently EBV-infected individuals, potent cytotoxic lymphocyte responses prevent EBV-associated pathologies. In addition to comprehensive adaptive T cell responses, several innate lymphocyte populations seem to target different stages of EBV infection and are compromised in primary immunodeficiencies that render individuals susceptible to symptomatic EBV infection. In this mini-review, I will highlight the functions of natural killer, γδ T cells, and natural killer T cells during innate immune responses to EBV. These innate lymphocyte populations seem to restrict both lytic replication and transforming latent EBV antigen expression. The mechanisms underlying the recognition of these different EBV infection programs by the respective innate lymphocytes are just starting to become unraveled, but will provide immunotherapeutic strategies to target pathologies that are associated with the different EBV infection programs.

Natural killer cells in herpesvirus infections

Natural killer (NK) cells are potent innate cytotoxic lymphocytes for the destruction of infected and transformed cells. Although they were originally considered to be ready-made assassins after their hematopoietic development, it has recently become clear that their activity is regulated by mechanisms such as repertoire composition, licensing, priming, and adaptive memory-like differentiation. Some of these mechanisms are influenced by infectious disease agents, including herpesviruses. In this review, we will compare expansion, stimulation, and effector functions of NK cell populations after infections with β- and γ ₁-herpesviruses because, though closely related, these pathogens seem to drive completely opposite NK cell responses. The discussed findings suggest that different NK cell subsets expand and perform protective functions during infectious diseases and might be used diagnostically to predict resistance to the causative pathogens as well as treat them by adoptive transfer of the respective populations.

Prospects for combining targeted and conventional cancer therapy with immunotherapy

Over the past 25 years, research in cancer therapeutics has largely focused on two distinct lines of enquiry. In one approach, efforts to understand the underlying cell-autonomous, genetic drivers of tumorigenesis have led to the development of clinically important targeted agents that result in profound, but often not durable, tumour responses in genetically defined patient populations. In the second parallel approach, exploration of the mechanisms of protective tumour immunity has provided several therapeutic strategies - most notably the 'immune checkpoint' antibodies that reverse the negative regulators of T cell function - that accomplish durable clinical responses in subsets of patients with various tumour types. The integration of these potentially complementary research fields provides new opportunities to improve cancer treatments. Targeted and immune-based therapies have already transformed the standard-of-care for several malignancies. However, additional insights into the effects of targeted therapies, along with conventional chemotherapy and radiation therapy, on the induction of antitumour immunity will help to advance the design of combination strategies that increase the rate of complete and durable clinical response in patients.

Infants with low vaccine antibody responses have altered innate cytokine response

We recently identified a population of 10% of infants who respond with sub-protective antibody levels to most routine primary pediatric vaccinations due to altered innate and adaptive immune responses. We term these infants as low vaccine responders (LVRs). Here we report new data showing that TLR7/8 agonist - R848 stimulation of PBMCs of LVR infants elicit significantly lower IFN-α, IL-12p70 and IL-1β, while inducing higher levels of CCL5 (RANTES) compared to normal vaccine responder (NVR) infants.

Reprogramming the lung microenvironment by inhaled immunotherapy fosters immune destruction of tumor

Due to their constant exposure to inhaled antigens, lungs represent a particularly immunosuppressive environment that limits excessive immune responses; however, cancer cells can exploit this unique environment for their growth. We previously described the ability of aerosolized CpG-ODN combined with Poly(I:C) (TLR9 and TLR3 agonists, respectively) to promote antitumor immunity in a B16 melanoma lung metastasis model. Here, we explored the possibility of improving the therapeutic efficacy of TLR9/TLR3 agonist combinations by including in the inhalant either an antibody directed to both Ly6G and Ly6C markers to locally deplete myeloid-derived suppressive cells (MDSCs) or IFNα to directly activate the natural killer (NK) and macrophage innate immune cells in the lung. Addition of nebulized anti-MDSC antibody RB6-8C5 to aerosolized CpG-ODN/Poly(I:C) resulted in reduced mRNA levels of immunsuppressive molecules (IL10, Arg-1, and Nos2), increased activation of resident NK cells and improved treatment outcome, with a significant reduction in established B16 melanoma lung metastases compared to treatment with CpG-ODN/Poly(I:C) alone. Likewise, addition of aerosolized IFNα led to increased mRNA levels of proinflammatory cytokines (IL15 and IFNγ) in the lung and recruitment of highly activated NK cells, with no evident signs of toxicity and with a significantly improved antitumor effect as compared with aerosolized CpG-ODN/Poly(I:C). Combining both IFNα and RB6-8C5 with CpG-ODN/Poly(I:C) did not produce an additive effect compared to IFNα + CpG-ODN/Poly(I:C) or RB6-8C5 + CpG-ODN/Poly(I:C). Our results indicate that the inhalation therapy is a feasible and non-invasive strategy to deliver immunodulatory molecules, including antibodies and cytokines that reprogram the lung tumor microenvironment to foster immune destruction of tumors.

Cognate HLA absence in trans diminishes human NK cell education

NK cells are innate lymphocytes with protective functions against viral infections and tumor formation. Human NK cells carry inhibitory killer cell Ig-like receptors (KIRs), which recognize distinct HLAs. NK cells with KIRs for self-HLA molecules acquire superior cytotoxicity against HLA- tumor cells during education for improved missing-self recognition. Here, we reconstituted mice with human hematopoietic cells from donors with homozygous KIR ligands or with a mix of hematopoietic cells from these homozygous donors, allowing assessment of the resulting KIR repertoire and NK cell education. We found that co-reconstitution with 2 KIR ligand-mismatched compartments did not alter the frequency of KIR-expressing NK cells. However, NK cell education was diminished in mice reconstituted with parallel HLA compartments due to a lack of cognate HLA molecules on leukocytes for the corresponding KIRs. This change in NK cell education in mixed human donor-reconstituted mice improved NK cell-mediated immune control of EBV infection, indicating that mixed hematopoietic cell populations could be exploited to improve NK cell reactivity against leukotropic pathogens. Taken together, these findings indicate that leukocytes lacking cognate HLA ligands can disarm KIR+ NK cells in a manner that may decrease HLA- tumor cell recognition but allows for improved NK cell-mediated immune control of a human γ-herpesvirus.

Monocyte and interferon based therapy for the treatment of ovarian cancer

Cytokines and cells of the innate immune system have been shown to be critical regulators in the elimination, equilibrium and escape of malignant cells. Despite in vitro and in vivo evidence, components of the innate immune system have shown limited efficacy in the treatment of ovarian cancer. Intraperitoneal immunotherapies are a promising field that has not yet been fully explored in ovarian cancer. Cytokine immunotherapy using interferon alpha (IFN-α) and interferon gamma (IFN-γ) has predominantly been used intraperitoneally in ovarian cancer, with promising results. Early studies also showed that autologous monocytes infused into the peritoneum have anti-tumor properties. Combination therapies have been shown to be more effective in treating cancer than mono-therapies. Based on these observations the combination of cell therapy with cytokine therapy may provide a unique strategy for the treatment of chemotherapy resistant solid cancers.

STAT2 Is Required for TLR-Induced Murine Dendritic Cell Activation and Cross-Presentation

TLR-stimulated cross-presentation by conventional dendritic cells (cDCs) is important in host defense and antitumor immunity. We recently reported that cDCs lacking the type I IFN signaling molecule STAT2 are impaired in cross-presenting tumor Ags to CD8(+) T cells. To investigate how STAT2 affects cross-presentation, we determined its requirements for dendritic cell activation. In this study, we report that STAT2 is essential for the activation of murine female cDCs upon TLR3, -4, -7, and -9 stimulation. In response to various TLR ligands, Stat2(-/-) cDCs displayed reduced expression of costimulatory molecules and type I IFN-stimulated genes. The cDC responses to exogenous IFN-α that we evaluated required STAT2 activation, indicating that the canonical STAT1-STAT2 heterodimers are the primary signaling transducers of type I IFNs in cDCs. Interestingly, LPS-induced production of IL-12 was STAT2 and type I IFN receptor (IFNAR) dependent, whereas LPS-induced production of TNF-α and IL-6 was STAT2 and IFNAR independent, suggesting a specific role of the IFNAR-STAT2 axis in the stimulation of proinflammatory cytokines by LPS in cDCs. In contrast, R848- and CpG-induced cytokine production was less influenced by the IFNAR-STAT2 axis. Short kinetics and IFNAR blockade studies showed that STAT2 main function is to transduce signals triggered by autocrine type I IFNs. Importantly, Stat2(-/-) cDCs were deficient in cross-presenting to CD8(+) T cells in vitro upon IFN-α, CpG, and LPS stimulation, and also in cross-priming and licensing cytotoxic T cell killers in vivo. We conclude that STAT2 plays a critical role in TLR-induced dendritic cell activation and cross-presentation, and thus is vital in host defense.

Lactococcus lactis subsp. lactis JCM 5805 activates natural killer cells via dendritic cells

Lactococcus lactis subsp. lactis JCM 5805 (JCM5805) has been shown to stimulate plasmacytoid dendritic cells (pDC). Here, we investigated the effect of JCM5805 on NK cells. In vitro studies suggested that JCM5805 activated natural killer (NK) cells via dendritic cells including pDC. Furthermore, the oral administration of JCM5805 enhanced the cytotoxic activity of NK cells.

Effects of oral intake of plasmacytoid dendritic cells-stimulative lactic acid bacterial strain on pathogenesis of influenza-like illness and immunological response to influenza virus

Lactococcus lactis ssp. lactis JCM5805 has been shown to be a rare lactic acid bacterium that can activate plasmacytoid dendritic cells in both murine and human species. In this study, we carried out a randomised placebo-controlled double-blind experiment to evaluate its effect on the pathogenesis of influenza-like illness during the winter season. A total of 213 volunteers were divided into two groups, which received either yogurt made with L. lactis JCM5805 or a placebo beverage daily for 10 weeks. In the JCM5805 group, the cumulative incidence days of 'cough' and 'feverishness', which are defined as major symptoms of an influenza-like illness, were significantly decreased compared with the placebo group. In addition, peripheral blood mononuclear cells prepared from volunteers were cultured in the presence of inactivated human influenza virus A/H1N1 (A/PR/8/34). IFN-α elicited by A/H1N1 tended to be higher in the JCM5805 group compared with the placebo group, and an IFN-α-inducible antiviral factor, interferon-stimulated gene 15 (ISG15), elicited by A/H1N1 was significantly higher in the JCM5805 group compared with the placebo group after the intake period. These results suggest that intake of JCM5805 is able to prevent the pathogenesis of an influenza-like illness via enhancement of an IFN-α-mediated response to the influenza virus.

Immunological Analysis During Interferon-Free Therapy for Chronic Hepatitis C Virus Infection Reveals Modulation of the Natural Killer Cell Compartment

BACKGROUND

Chronic hepatitis C virus (HCV) infection is a global health problem, resulting in liver failure, hepatocellular carcinoma, and liver-related death. Natural killer (NK) cells are innate immune cells, and their activity is known to correlate to viral treatment response of HCV. In this study, we investigate the immune effects of viral load decline with direct-acting antivirals (DAAs) in blood.

METHODS

Twelve patients with chronic HCV were treated with asunaprevir and daclatasvir, and peripheral blood was analyzed at various time points during therapy.

RESULTS

In line with previous studies, we confirmed restoration of HCV-specific T-cell frequency upon viral load decline. In addition, we show that serum interferon (IFN)-γ inducible-protein 10, interleukin (IL)-12p40, and IL-18 levels decreased early after start of therapy. Surface expression of activation receptors NKp30, NKp46, and inhibitory receptor NKG2A on blood NK cells reduced during therapy. In addition, the expression of TRAIL on NK cells was reduced during IFN-free therapy, suggesting a decrease in TRAIL-mediated killing by NK cells.

CONCLUSIONS

We show that viral load decline as a consequence of treatment with novel DAAs in chronic HCV patients reduces serum levels of NK cell-stimulating cytokines and causes correction of the altered NK cell phenotype observed in chronic HCV patients.

CLINICAL TRIALS REGISTRATION

NCT02282709.

CD56brightCD16- NK Cells Produce Adenosine through a CD38-Mediated Pathway and Act as Regulatory Cells Inhibiting Autologous CD4+ T Cell Proliferation

Recent studies suggested that human CD56(bright)CD16(-) NK cells may play a role in the regulation of the immune response. Since the mechanism(s) involved have not yet been elucidated, in the present study we have investigated the role of nucleotide-metabolizing enzymes that regulate the extracellular balance of nucleotides/nucleosides and produce the immunosuppressive molecule adenosine (ADO). Peripheral blood CD56(dim)CD16(+) and CD56(bright)CD16(-) NK cells expressed similar levels of CD38. CD39, CD73, and CD157 expression was higher in CD56(bright)CD16(-) than in CD56(dim)CD16(+) NK cells. CD57 was mostly expressed by CD56(dim)CD16(+) NK cells. CD203a/PC-1 expression was restricted to CD56(bright)CD16(-) NK cells. CD56(bright)CD16(-) NK cells produce ADO and inhibit autologous CD4(+) T cell proliferation. Such inhibition was 1) reverted pretreating CD56(bright)CD16(-) NK cells with a CD38 inhibitor and 2) increased pretreating CD56(bright)CD16(-) NK cells with a nucleoside transporter inhibitor, which increase extracellular ADO concentration. CD56(bright)CD16(-) NK cells isolated from the synovial fluid of juvenile idiopathic arthritis patients failed to inhibit autologous CD4(+) T cell proliferation. Such functional impairment could be related to 1) the observed reduced CD38/CD73 expression, 2) a peculiar ADO production kinetics, and 3) a different expression of ADO receptors. In contrast, CD56(bright)CD16(-) NK cells isolated from inflammatory pleural effusions display a potent regulatory activity. In conclusion, CD56(bright)CD16(-) NK cells act as "regulatory cells" through ADO produced by an ectoenzymes network, with a pivotal role of CD38. This function may be relevant for the modulation of the immune response in physiological and pathological conditions, and it could be impaired during autoimmune/inflammatory diseases.

Twenty-five years of type I interferon-based treatment: a critical analysis of its therapeutic use

The clinical exploitation of type I interferon (IFN) as an antiviral and antineoplastic agent is based on the properties originally attributed to this cytokine family, with schedules reflecting only their antiviral and antiproliferative activities. Nevertheless, type I IFN has emerged as a central activator of the innate immunity. As current schedules of treatment for chronic hepatitis C and for hematological and solid tumors, based on the continuous administration of recombinant type I IFN or pegylated formulations, disregard viral resistance, host genetic variants predicting treatment outcome and mechanisms of refractoriness, new administration schedules, the combination of type I IFN with new drugs and the increased monitoring of patients' susceptibility to type I IFN are expected to provide a new life to this valuable cytokine.

IFN-λ-mediated IL-12 production in macrophages induces IFN-γ production in human NK cells

With increasing interest in alternative options to interferon-alpha-based treatments, IFN-λ has shown therapeutic promise in a variety of diseases. Although the antiviral activity of IFN-λ has been extensively studied, there is limited knowledge regarding the immunological functions of IFN-λ and how these differ from those of other classes of IFNs. In this study, we investigated the effects of IFN-λ on primary human NK cells, both in a direct and indirect capacity. We demonstrate that in contrast to interferon-alpha, IFN-λ is unable to directly stimulate NK cells, due to the absence of IFN-λ receptor chain 1 (IFN-λR1) on NK cells. However, IFN-λ, in combination with TLR4 challenge, is able to induce the production of select members of the IL-12 family of cytokines in monocyte-derived macrophages. We further show that through macrophage-mediated IL-12 production, IFN-λ is able to indirectly affect NK cells and ultimately induce IFN-γ production.

NK cells and interferons

The role of Natural Killer cells in host defense against infections as well as in tumour surveillance has been widely appreciated for a number of years. Upon recognition of "altered" cells, NK cells release the content of cytolytic granules, leading to the death of target cells. Moreover, NK cells are powerful producers of chemokines and cytokines, particularly Interferon-γ (IFN-γ), of which they are the earliest source upon a variety of infections. Despite being armed to fight against pathogens, NK cells become fully functional upon an initial phase of activation that requires the action of several cytokines, including type I IFNs. Type I IFNs are now recognized as key players in antiviral defense and immune regulation, and evidences from both mouse models of disease and in vitro studies support the existence of an alliance between type I IFNs and NK cells to ensure effective protection against viral infections. This review will focus on the role of type I IFNs in regulating NK cell functions to elicit antiviral response and on NK cell-produced IFN-γ beneficial and pathological effects.

IL-15 complexes induce NK- and T-cell responses independent of type I IFN signaling during rhinovirus infection

Rhinoviruses are among the most common viruses to infect man, causing a range of serious respiratory diseases including exacerbations of asthma and COPD. Type I IFN and IL-15 are thought to be required for antiviral immunity; however, their function during rhinovirus infection in vivo is undefined. In RV-infected human volunteers, IL-15 protein expression in fluid from the nasal mucosa and in bronchial biopsies was increased. In mice, RV induced type I IFN-dependent expressions of IL-15 and IL-15Rα, which in turn were required for NK- and CD8(+) T-cell responses. Treatment with IL-15-IL-15Rα complexes (IL-15c) boosted RV-induced expression of IL-15, IL-15Rα, IFN-γ, CXCL9, and CXCL10 followed by recruitment of activated, IFN-γ-expressing NK, CD8(+), and CD4(+) T cells. Treating infected IFNAR1(-/-) mice with IL-15c similarly increased IL-15, IL-15Rα, IFN-γ, and CXCL9 (but not CXCL10) expression also followed by NK-, CD8(+)-, and CD4(+)-T-cell recruitment and activation. We have demonstrated that type I IFN-induced IFN-γ and cellular immunity to RV was mediated by IL-15 and IL-15Rα. Importantly, we also show that IL-15 could be induced via a type I IFN-independent mechanism by IL-15 complex treatment, which in turn was sufficient to drive IFN-γ expression and lymphocyte responses.

Dendritic cell derived cytokines in human natural killer cell differentiation and activation

Dendritic cells (DCs) and natural killer (NK) cells shape each other’s functions early during immune responses. DCs activate NK cells and NK cells can mature or kill DCs. In this review we will discuss which DC and NK cell subsets are mainly affected by this interaction, where these encounters might take place and which signals are exchanged. Finally, we will point out what the clinical benefit of understanding this interaction might be and how it changed our view on NK cells as innate lymphocytes.

Immunomodulatory effect of Lactococcus lactis JCM5805 on human plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs) play a crucial role in anti-viral immunity through production of large amounts of interferons (IFNs). A previous study revealed the existence of lactic acid bacteria that directly stimulate pDCs in mice. In this study, we demonstrated that Lactococcus lactis JCM5805 activates human pDCs and induces IFN production in vitro. In addition, our randomized, placebo-controlled, double blind test showed that yogurt fermented with L. lactis JCM5805 activated pDC activity in vivo. This effect was greater in low pDC subjects, and their ability to produce IFNs was increased from the beginning. Furthermore, the risk of morbidity from the common cold was suppressed in the L. lactis JCM5805 group compared with the placebo group. In conclusion, intake of L. lactis JCM5805 can directly activate pDCs and increase the ability to produce IFNs in vivo. Therefore, L. lactis JCM5805 may be a beneficial tool to enhance anti-viral immunity in humans.

The Yin and Yang of Toll-like receptors in cancer

Recognition of non-self molecular patterns by pattern recognition receptors is a cornerstone of innate immunity. Toll-like receptors (TLRs) exert a key role in recognizing pathogen-associated molecular patterns (PAMPs) but have also been implicated in the recognition of damage-associated molecular patterns (DAMPs). As such, TLRs regulate a wide range of biological responses including inflammatory and immune responses during carcinogenesis. The high expression of TLRs by antigen-presenting cells, including dendritic cells, and their ability to induce antitumor mediators such as type I interferon has led to efforts to utilize TLR agonists in tumor therapy in order to convert the often tolerant immune response toward antitumor responses. However, TLRs are also increasingly recognized as regulators of tumor-promoting inflammation and promoters of tumor survival signals. Here, we will review in detail the dichotomous role of TLRs in tumor biology, focusing on relevant TLR-dependent pro- and antitumor pathways, and discuss clinical applications of TLR-targeted therapies for tumor prevention and treatment.

Containing "The Great Houdini" of viruses: combining direct acting antivirals with the host immune response for the treatment of chronic hepatitis C

Presently the development of new therapies for hepatitis C virus (HCV) is rapidly moving forward. Almost every week new data appear on how direct acting antivirals (DAAs) succeed or fail in clinical trials. Despite the potency of many of the DAA combinations, the effect exerted by ribavirin (RBV) is still needed for an effective therapy in many new DAA combinations. Due to the strong antiviral effect of DAAs, it is likely that a major complementary therapeutic effect exerted by RBV is immune modulation resulting in an increased barrier to development of resistance. For HCV genotype 1a infections elimination of pegylated interferon, is not possible in many DAA combinations without jeopardizing the results. The host immune response is thus likely to play a key role even during DAA-based therapies. Hence, T cells may recognize and eliminate viral variants with resistance to the DAAs. We herein show several examples where this may be the case, supporting the rationale of including the host response also in the new therapeutic regimens. This review will describe the potential benefits of combining various DAAs with means to activate the specific immune response against HCV.

Plasmacytoid dendritic cells: no longer an enigma and now key to transplant tolerance?

Plasmacytoid (p) dendritic cells (DC) are a specialized subset of DC whose primary role was initially defined by the production of type I interferons in response to viral infection. They are now known to also possess a repertoire of functions capable of determining T cell fate and activation. Under homeostatic conditions, non-lymphoid tissue-resident pDC play a critical role in the regulation of mucosal immunity, as well as the development of central and peripheral tolerance. Although these cells display a number of characteristics that differ from conventional DC, particularly altered costimulatory molecule expression and poor allostimulatory capacity when interacting with T cells, this phenotype favors the generation of alloantigen-specific regulatory CD4(+) or CD8(+) T cells critical to the development of graft tolerance. In this minireview, we discuss pDC ontogeny, functional biology and the emerging data that demonstrate the importance of pDC in the induction of tolerance, as well as recent studies that define mechanisms underlying pDC-mediated tolerance to both solid organ and haematopoietic stem cell transplants. We also highlight their use in clinical settings and the potential of pDC both as targets and cellular therapeutic agents to improve the outcome of organ transplantation.

The role of natural killer cells in hepatitis C infection

HCV infection is an exponentially growing health burden worldwide, with an estimated 170 million people infected. Although therapies for HCV are continually improving, there remain a considerable proportion of patients who do not achieve viral eradication and develop liver disease. Natural killer (NK) cells are crucial for T-cell activation and are one of the first-line sentinel cell responders to viral infection. A recent explosion in studies exploring the role of NK cells in HCV infection has yielded important mechanistic information and intriguing potential therapeutic options for HCV infection. This review provides a general overview of normal NK cell function and outlines some of the important mechanisms characterizing the immune interplay between NK cells and HCV infection.