Enhanced NK cell activity in mice injected with interferon and interferon inducers

Standing on Shoulders: Interferon Research From Viral Interference to Lupus Pathogenesis and Treatment

The discovery of interferon in the 1950s represents much more than the identification of the first cytokine and the key mediator of antiviral host defense. Defining the molecular nature and complexity of the type I interferon family, as well as its inducers and molecular mechanisms of action, was the work of investigators working at the highest level and producing insights of great consequence. Current knowledge of receptor-ligand interactions, cell signaling, and transcriptional regulation derives from studies of type I interferon. It is on the shoulders of the giants who produced that knowledge that others stand and have revealed critical mechanisms of the pathogenesis of systemic lupus erythematosus and other autoimmune diseases. The design of novel therapeutics is informed by the advances in investigation of type I interferon, with the potential for important impact on patient management.

Enhancing immunotherapy outcomes by targeted remodeling of the tumor microenvironment via combined cGAS-STING pathway strategies

Immune checkpoint inhibitors (ICIs) represent a groundbreaking advance in the treatment of malignancies such as melanoma and non-small cell lung cancer, showcasing substantial therapeutic benefits. Nonetheless, the efficacy of ICIs is limited to a small subset of patients, primarily benefiting those with "hot" tumors characterized by significant immune infiltration. The challenge of converting "cold" tumors, which exhibit minimal immune activity, into "hot" tumors to enhance their responsiveness to ICIs is a critical and complex area of current research. Central to this endeavor is the activation of the cGAS-STING pathway, a pivotal nexus between innate and adaptive immunity. This pathway's activation promotes the production of type I interferon (IFN) and the recruitment of CD8+ T cells, thereby transforming the tumor microenvironment (TME) from "cold" to "hot". This review comprehensively explores the cGAS-STING pathway's role in reconditioning the TME, detailing the underlying mechanisms of innate and adaptive immunity and highlighting the contributions of various immune cells to tumor immunity. Furthermore, we delve into the latest clinical research on STING agonists and their potential in combination therapies, targeting this pathway. The discussion concludes with an examination of the challenges facing the advancement of promising STING agonists in clinical trials and the pressing issues within the cGAS-STING signaling pathway research.

A Frail Hairy Cell Leukemia Patient Successfully Treated with Pegylated Interferon-α-2A

Hairy cell leukemia (HCL) treatment in elderly, frail subjects is still unsatisfactory, and interferons, old-fashioned therapies, can be effectively used in this subset of patients. Here, to the best of our knowledge, we report for the first time an old, frail HCL patient effectively and safely treated with pegylated interferon-α-2a in monotherapy as a first-line treatment. At diagnosis, the patient arrived in a life-threating condition due to severe neutropenia and splenomegaly with high risk of splenic rupture. However, splenectomy was proposed and refused by the patient; therefore, a therapy with pegylated interferon-α-2a was initiated. After six months of therapy, the patient displayed the disappearance of palpable splenomegaly and of peripheral hairy cells at morphological examination without any drug-related adverse event. Our case report supports the use of pegylated interferon-α-2a in monotherapy as an effective and safe alternative therapeutic option in frail, elderly patients not eligible for purine analogous or targeted therapies.

Prompt Hematological Recovery in Response to a Combination of Pegylated Interferon α-2a and Rituximab in a Profoundly Immuno-Suppressed Hairy Cell Leukemia Patient with a Mycobacterial Infection at Onset: Benefits and Drawbacks of Rapid Immune Reconstitution

The present paper reports, to the best of our knowledge for the first time, the efficacy and tolerability of the combination of interferon (IFN)α-2a in pegylated formulation and rituximab after a “priming” phase with IFN in the frontline treatment of hairy cell leukemia (HCL) in a profoundly immunosuppressed patient with a Mycobacterium abscessus infection at onset. This immunotherapy combination may represent a potential therapeutic option in patients with active severe infection and for whom the use of purine nucleoside analogues (PNA) is contraindicated. The benefits and drawbacks of remarkably rapid immune reconstitution in the context of opportunistic infections are highlighted as well, as the potentially paradoxical effects of immune recovery as a result of effective immunotherapy strategies, known as immune reconstitution inflammatory syndrome (IRIS), have to be taken into account when dealing with patients with opportunistic infections.

Chemical and Biomolecular Strategies for STING Pathway Activation in Cancer Immunotherapy

The stimulator of interferon genes (STING) cellular signaling pathway is a promising target for cancer immunotherapy. Activation of the intracellular STING protein triggers the production of a multifaceted array of immunostimulatory molecules, which, in the proper context, can drive dendritic cell maturation, antitumor macrophage polarization, T cell priming and activation, natural killer cell activation, vascular reprogramming, and/or cancer cell death, resulting in immune-mediated tumor elimination and generation of antitumor immune memory. Accordingly, there is a significant amount of ongoing preclinical and clinical research toward further understanding the role of the STING pathway in cancer immune surveillance as well as the development of modulators of the pathway as a strategy to stimulate antitumor immunity. Yet, the efficacy of STING pathway agonists is limited by many drug delivery and pharmacological challenges. Depending on the class of STING agonist and the desired administration route, these may include poor drug stability, immunocellular toxicity, immune-related adverse events, limited tumor or lymph node targeting and/or retention, low cellular uptake and intracellular delivery, and a complex dependence on the magnitude and kinetics of STING signaling. This review provides a concise summary of the STING pathway, highlighting recent biological developments, immunological consequences, and implications for drug delivery. This review also offers a critical analysis of an expanding arsenal of chemical strategies that are being employed to enhance the efficacy, safety, and/or clinical utility of STING pathway agonists and lastly draws attention to several opportunities for therapeutic advancements.

When breaks get hot: inflammatory signaling in BRCA1/2-mutant cancers

Genomic instability and inflammation are intricately connected hallmark features of cancer. DNA repair defects due to BRCA1/2 mutation instigate immune signaling through the cGAS/STING pathway. The subsequent inflammatory signaling provides both tumor-suppressive as well as tumor-promoting traits. To prevent clearance by the immune system, genomically instable cancer cells need to adapt to escape immune surveillance. Currently, it is unclear how genomically unstable cancers, including BRCA1/2-mutant tumors, are rewired to escape immune clearance. Here, we summarize the mechanisms by which genomic instability triggers inflammatory signaling and describe adaptive mechanisms by which cancer cells can 'fly under the radar' of the immune system. Additionally, we discuss how therapeutic activation of the immune system may improve treatment of genomically instable cancers.

Evading immune surveillance via tyrosine phosphorylation of nuclear PCNA

Increased DNA replication and metastasis are hallmarks of cancer progression, while deregulated proliferation often triggers sustained replication stresses in cancer cells. How cancer cells overcome the growth stress and proceed to metastasis remains largely elusive. Proliferating cell nuclear antigen (PCNA) is an indispensable component of the DNA replication machinery. Here, we show that phosphorylation of PCNA on tyrosine 211 (pY211-PCNA) regulates DNA metabolism and tumor microenvironment. Abrogation of pY211-PCNA blocks fork processivity, resulting in biogenesis of single-stranded DNA (ssDNA) through a MRE11-dependent mechanism. The cytosolic ssDNA subsequently induces inflammatory cytokines through a cyclic GMP-AMP synthetase (cGAS)-dependent cascade, triggering an anti-tumor immunity by natural killer (NK) cells to suppress distant metastasis. Expression of pY211-PCNA is inversely correlated with cytosolic ssDNA and associated with poor survival in patients with cancer. Our results pave the way to biomarkers and therapies exploiting immune responsiveness to target metastatic cancer.

PD-1 Expression on NK Cells in Malaria-Exposed Individuals Is Associated with Diminished Natural Cytotoxicity and Enhanced Antibody-Dependent Cellular Cytotoxicity

Natural killer (NK) cells are key effector cells of innate resistance capable of destroying tumors and virus-infected cells through cytotoxicity and rapid cytokine production. The control of NK cell responses is complex and only partially understood. PD-1 is an inhibitory receptor that regulates T cell function, but a role for PD-1 in regulating NK cell function is only beginning to emerge. Here, we investigated PD-1 expression on NK cells in children and adults in Mali in a longitudinal analysis before, during, and after infection with Plasmodium falciparum malaria. We found that NK cells transiently upregulate PD-1 expression and interleukin-6 (IL-6) production in some individuals during acute febrile malaria. Furthermore, the percentage of PD-1 expressing NK cells increases with age and cumulative malaria exposure. Consistent with this, NK cells of malaria-naive adults upregulated PD-1 following P. falciparum stimulation in vitro Additionally, functional in vitro studies revealed that PD-1 expression on NK cells is associated with diminished natural cytotoxicity but enhanced antibody-dependent cellular cytotoxicity (ADCC). These data indicate that PD-1⁺ NK cells expand in the context of chronic immune activation and suggest that PD-1 may contribute to skewing NK cells toward enhanced ADCC during infections such as malaria.

Immune Conversion of Tumor Microenvironment by Oncolytic Viruses: The Protoparvovirus H-1PV Case Study

Cancer cells utilize multiple mechanisms to evade and suppress anticancer immune responses creating a “cold” immunosuppressive tumor microenvironment. Oncolytic virotherapy is emerging as a promising approach to revert tumor immunosuppression and enhance the efficacy of other forms of immunotherapy. Growing evidence indicates that oncolytic viruses (OVs) act in a multimodal fashion, inducing immunogenic cell death and thereby eliciting robust anticancer immune responses. In this review, we summarize information about OV-mediated immune conversion of the tumor microenvironment. As a case study we focus on the rodent protoparvovirus H-1PV and its dual role as an oncolytic and immune modulatory agent. Potential strategies to improve H-1PV anticancer efficacy are also discussed.

Role of Type I Interferons on Filovirus Pathogenesis

Filoviruses, such as Ebola and Marburg virus, encode viral proteins with the ability to counteract the type I interferon (IFN-I) response. These IFN-I antagonist proteins are crucial to ensure virus replication, prevent an antiviral state in infected and bystander cells, and impair the ability of antigen-presenting cells to initiate adaptive immune responses. However, in recent years, a number of studies have underscored the conflicting data between in vitro studies and in vivo data obtained in animal models and clinical studies during outbreaks. This review aims to summarize these data and to discuss the relative contributions of IFN-α and IFN-β to filovirus pathogenesis in animal models and humans. Finally, we evaluate the putative utilization of IFN-I in post-exposure therapy and its implications as a biomarker of vaccine efficacy.

Weak vaccinia virus-induced NK cell regulation of CD4 T cells is associated with reduced NK cell differentiation and cytolytic activity

Natural killer (NK) cells control antiviral adaptive immune responses in mice during some virus infections, but the universality of this phenomenon remains unknown. Lymphocytic choriomeningitis virus (LCMV) infection of mice triggered potent cytotoxic activity of NK cells (NK^LCMV) against activated CD4 T cells, tumor cells, and allogeneic lymphocytes. In contrast, NK cells activated by vaccinia virus (VACV) infection (NK^VACV) exhibited weaker cytolytic activity against each of these target cells. Relative to NK^LCMV cells, NK^VACV cells exhibited a more immature (CD11b^-CD27⁺) phenotype, and lower expression levels of the activation marker CD69, cytotoxic effector molecules (perforin, granzyme B), and the transcription factor IRF4. NK^VACV cells expressed higher levels of the inhibitory molecule NKG2A than NK^LCMV cells. Consistent with this apparent lethargy, NK^VACV cells only weakly constrained VACV-specific CD4 T-cell responses. This suggests that NK cell regulation of adaptive immunity, while universal, may be limited with viruses that poorly activate NK cells.

Dynamics of Natural Killer Cells Cytotoxicity in Microwell Arrays with Connecting Channels

Natural killer (NK) cells serve an important role in immune system by recognizing and killing the potentially malignant cells without antigen sensitization, and could be promising in cancer therapy. We have designed and fabricated microwell arrays with microchannel connections in polydimethylsiloxane (PDMS) substrates to study the interaction dynamics of NK-92MI cells with MCF7 breast cancer cells using time-lapse imaging by fluorescence microscopy for 15 h. Although cell seeding density was the same, NK cell cytotoxicity was found to be higher in larger microwells, which is manifested as increased target death ratio from 13.7 ± 3.1 to 46.3 ± 3.3% and shorter triggering time of first target lysis from 502 ± 49 to 391 ± 63 min in 150 μm × 150 μm microwells comparing to 50 μm × 50 μm wells in 15 h. Mirochannel connection between adjacent microwells of the same size increased the overall target death ratio by >10%, while connection between microwells of different sizes led to significantly increased target death ratio and delayed first target lysis in smaller microwells. Our findings reveal unique cell interaction dynamics, such as initiation and stimulation, of NK cell cytotoxicity in a confined microenvironment, which is different from population-based study, and the results could lead to a better understanding of the dynamics of NK cell cytotoxicity.

Colonization and effector functions of innate lymphoid cells in mucosal tissues

Innate lymphoid cells (ILCs) protect mucosal barrier tissues to fight infection and maintain tissue integrity. ILCs and their progenitors are developmentally programmed to migrate, differentiate and populate various mucosal tissues and associated lymphoid tissues. Functionally mature ILC subsets respond to diverse pathogens such as bacteria, viruses, fungi and parasites in subset-specific manners. In this review, we will discuss how ILCs populate mucosal tissues and regulate immune responses to distinct pathogens to protect the host and maintain tissue integrity.

Species difference in reactivity to lignin-like enzymatically polymerized polyphenols on interferon-γ synthesis and involvement of interleukin-2 production in mice

Recent studies have revealed that lignin-like polymerized polyphenols can activate innate immune systems. In this study, we aimed to evaluate whether these polymerized polyphenols could activate leukocytes from different murine strains. Splenocytes from 12 mouse strains were investigated. Our results revealed species differences in reactivity to phenolic polymers on interferon-γ (IFN-γ) release. Mice that possessed the H2(a) or H2(k) haplotype antigens were the highly responsive strains. To clarify these different points in soluble factors, multiplex cytokine profiling analysis was carried out and we identified interleukin (IL)-2 as a key molecule for IFN-γ induction by polymerized polyphenols. Furthermore, inhibition of IL-2 and IL-2Rα by neutralizing antibodies significantly decreased cytokine production in the highly responsive mice strains. Our results indicate that species difference in reactivity to phenolic polymers is mediated by adequate release of IL-2 and its receptor, IL-2Rα.

Recognition and Regulation of T Cells by NK Cells

Regulation of T cell responses by innate lymphoid cells (ILCs) is increasingly documented and studied. Direct or indirect crosstalk between ILCs and T cells early during and after T cell activation can affect their differentiation, polarization, and survival. Natural killer (NK) cells that belong to the ILC1 group were initially described for their function in recognizing and eliminating "altered self" and as source of early inflammatory cytokines, most notably type II interferon. Using signals conveyed by various germ-line encoded activating and inhibitory receptors, NK cells are geared to sense sudden cellular changes that can be caused by infection events, malignant transformation, or cellular stress responses. T cells, when activated by TCR engagement (signal 1), costimulation (signal 2), and cytokines (signal 3), commit to a number of cellular alterations, including entry into rapid cell cycling, metabolic changes, and acquisition of effector functions. These abrupt changes may alert NK cells, and T cells might thereby expose themselves as NK cell targets. Here, we review how activated T cells can be recognized and regulated by NK cells and what consequences such regulation bears for T cell immunity in the context of vaccination, infection, or autoimmunity. Conversely, we will discuss mechanisms by which activated T cells protect themselves against NK cell attack and outline the significance of this safeguard mechanism.

Innate Antiviral Defenses Independent of Inducible IFNα/β Production

The type I interferons (IFNs) (IFNα and IFNβ) not only have potent antiviral activities, but also have pathological functions if produced at high levels or over a long time. Recent articles have described antiviral immune mechanisms that are activated in response to virus infection at epithelial surfaces independently of IFNα and IFNβ. This may allow the host to exert rapid local antiviral activity and only induce a full-blown, and potentially pathological, type I IFN response in situations where stronger protective immunity is needed. Here, I describe the emerging understanding of early antiviral defenses, which are independent of type I IFN responses, and also discuss how this enables tissues to exert rapid antiviral activities and to limit type I IFN production.

NK cells regulating T cell responses: mechanisms and outcome

Natural killer (NK) cells are important innate effectors in immunity. NK cells also have a role in the regulation of the adaptive immune response, and have been shown, in different contexts, to stimulate or inhibit T cell responses. Recent findings have expanded our understanding of the mechanisms underlying this regulation, revealing that regulation by NK cells can result from both direct interactions between NK cells and T cells, as well as indirectly, involving interactions with antigen presenting cells and the impact of NK cells on infected cells and pathogen load. We review these recent findings here, and outline emerging principles of how this regulation influences the overall outcome of adaptive immunity in infection and disease.

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.

Type I interferons protect T cells against NK cell attack mediated by the activating receptor NCR1

Direct type I interferon (IFN) signaling on T cells is necessary for the proper expansion, differentiation, and survival of responding T cells following infection with viruses prominently inducing type I IFN. The reasons for the abortive response of T cells lacking the type I IFN receptor (Ifnar1(-/-)) remain unclear. We report here that Ifnar1(-/-) T cells were highly susceptible to natural killer (NK) cell-mediated killing in a perforin-dependent manner. Depletion of NK cells prior to lymphocytic choriomeningitis virus (LCMV) infection completely restored the early expansion of Ifnar1(-/-) T cells. Ifnar1(-/-) T cells had elevated expression of natural cytotoxicity triggering receptor 1 (NCR1) ligands upon infection, rendering them targets for NCR1 mediated NK cell attack. Thus, direct sensing of type I IFNs by T cells protects them from NK cell killing by regulating the expression of NCR1 ligands, thereby revealing a mechanism by which T cells can evade the potent cytotoxic activity of NK cells.

Regulation of mouse NK cell development and function by cytokines

Natural Killer (NK) cells are innate lymphocytes with an important role in the early defense against intracellular pathogens and against tumors. Like other immune cells, almost every aspects of their biology are regulated by cytokines. Interleukin (IL)-15 is pivotal for their development, homeostasis, and activation. Moreover, numerous other activating or inhibitory cytokines such as IL-2, IL-4, IL-7, IL-10, IL-12, IL-18, IL-21, Transforming growth factor-β (TGFβ) and type I interferons regulate their activation and their effector functions at different stages of the immune response. In this review we summarize the current understanding on the effect of these different cytokines on NK cell development, homeostasis, and functions during steady-state or upon infection by different pathogens. We try to delineate the cellular sources of these cytokines, the intracellular pathways they trigger and the transcription factors they regulate. We describe the known synergies or antagonisms between different cytokines and highlight outstanding questions in this field of investigation. Finally, we discuss how a better knowledge of cytokine action on NK cells could help improve strategies to manipulate NK cells in different clinical situations.

The host environment is responsible for aging-related functional NK cell deficiency

NK cells play an important role in immunity against infection and tumors. Aging-related functional NK cell deficiency is well documented in humans and mice. However, the mechanism for this is poorly understood. Using an adoptive transfer approach in mice, we found that NK cells from both young and aged mice responded vigorously to priming by pathogen-derived products after being cotransferred into young mice. In contrast, NK cells from young mice responded poorly to priming by pathogen-derived products after being transferred to aged mice. In addition to defects in NK cell priming, maturation of NK cells under steady-state conditions is also impaired in aged mice, resulting in a decreased proportion of CD27(-) mature NK cells. We found that bone marrow from young and aged mice gave rise to CD27(-) mature NK cells similarly in young mixed bone marrow chimeric mice. Furthermore, by using a novel bone marrow transfer approach without irradiation, we found that after being transferred to aged mice, bone marrow from young mice gave rise to NK cells with maturation defects. Finally, we found that aging-related functional NK cell deficiency was completely reversed by injecting soluble IL-15/IL-15Rα complexes. In contrast, blockade of IL-10 signaling, which broadly augments inflammatory responses to pathogen-derived products, had little effect on aging-related defects in NK cell priming. These data demonstrate that the aged host environment is responsible for aging-related functional NK cell deficiency. Additionally, our data suggest that IL-15 receptor agonists may be useful tools in treating aging-related functional NK cell deficiency.

Modulation of interferon-γ synthesis by the effects of lignin-like enzymatically polymerized polyphenols on antigen-presenting cell activation and the subsequent cell-to-cell interactions

Lignin-like polymerized polyphenols strongly activate lymphocytes and induce cytokine synthesis. We aimed to characterise the mechanisms of action of polymerized polyphenols on immunomodulating functions. We compared the reactivity of leukocytes from various organs to that of polymerized polyphenols. Splenocytes and resident peritoneal cavity cells (PCCs) responded to polymerized polyphenols and released several cytokines, whereas thymocytes and bone-marrow cells showed no response. Next, we eliminated antigen-presenting cells (APCs) from splenocytes to study their involvement in cytokine synthesis. We found that APC-negative splenocytes showed significantly reduced cytokine production induced by polymerized polyphenols. Additionally, adequate interferon-γ (IFN-γ) induction by polymerized polyphenols was mediated by the coexistence of APCs and T cells because the addition of T cells to PCCs increased IFN-γ production. Furthermore, inhibition of the T cell-APC interaction using neutralising antibodies significantly decreased cytokine production. Thus, cytokine induction by polymerized polyphenols was mediated by the interaction between APCs and T cells.

Immunotherapy for tularemia

Francisella tularensis is a gram-negative bacterium that causes the zoonotic disease tularemia. Francisella is highly infectious via the respiratory route (~10 CFUs) and pulmonary infections due to type A strains of F. tularensis are highly lethal in untreated patients (>30%). In addition, no vaccines are licensed to prevent tularemia in humans. Due to the high infectivity and mortality of pulmonary tularemia, F. tularensis has been weaponized, including via the introduction of antibiotic resistance, by several countries. Because of the lack of efficacious vaccines, and concerns about F. tularensis acquiring resistance to antibiotics via natural or illicit means, augmentation of host immunity, and humoral immunotherapy have been investigated as countermeasures against tularemia. This manuscript will review advances made and challenges in the field of immunotherapy against tularemia.

The human natural killer cytotoxic cell line NK-92, once armed with a murine CD16 receptor, represents a convenient cellular tool for the screening of mouse mAbs according to their ADCC potential

To take advantage of the large number of well-characterized mouse immunoglobulins (IgGs) for the study of antibody-dependent cell-mediated cytotoxicity (ADCC) in human cells, we armed human cytotoxic lymphocytes with a mouse receptor for the Fc portion of IgG antibodies. The human ΝΚ-92 natural killer cell line was transduced with a mouse receptor gene (mCD16), which was stably expressed on the cell surface (referred to as NK-92 (mCD16) ). When tested against a B-lymphoblastoid cell line (BLCL) coated with mouse anti-CD20 IgG1, IgG2a or IgG2b monoclonal antibodies (mAbs), the newly expressed mouse Fc receptor enabled the NK-92 (mCD16) cells to kill the BLCL by ADCC. Next, using the NK-92 (mCD16) we compared mouse mAbs directed at B lineage specific CD antigens for their ability to induce ADCC against human Epstein-Barr virus- infected B lymphoblastoid (for anti-CD19, -CD20 and -CD21) or against myeloma (for anti-CD38 and -CD138) target cells. Our results demonstrated that the "NK-92 (mCD16) assay" allows convenient and sensitive discrimination of mouse mAbs for their ability to mediate ADCC in a human cellular system. In addition, our results provide examples of dissociation between opsonization and target cell killing through ADCC. These "murinized" human effector cells thus represent a convenient cellular tool for the study of ADCC.

Targeted induction of interferon-λ in humanized chimeric mouse liver abrogates hepatotropic virus infection

BACKGROUND & AIMS

The interferon (IFN) system plays a critical role in innate antiviral response. We presume that targeted induction of IFN in human liver shows robust antiviral effects on hepatitis C virus (HCV) and hepatitis B virus (HBV).

METHODS

This study used chimeric mice harboring humanized livers and infected with HCV or HBV. This mouse model permitted simultaneous analysis of immune responses by human and mouse hepatocytes in the same liver and exploration of the mechanism of antiviral effect against these viruses. Targeted expression of IFN was induced by treating the animals with a complex comprising a hepatotropic cationic liposome and a synthetic double-stranded RNA analog, pIC (LIC-pIC). Viral replication, IFN gene expression, IFN protein production, and IFN antiviral activity were analyzed (for type I, II and III IFNs) in the livers and sera of these humanized chimeric mice.

RESULTS

Following treatment with LIC-pIC, the humanized livers of chimeric mice exhibited increased expression (at the mRNA and protein level) of human IFN-λs, resulting in strong antiviral effect on HBV and HCV. Similar increases were not seen for human IFN-α or IFN-β in these animals. Strong induction of IFN-λs by LIC-pIC occurred only in human hepatocytes, and not in mouse hepatocytes nor in human cell lines derived from other (non-hepatic) tissues. LIC-pIC-induced IFN-λ production was mediated by the immune sensor adaptor molecules mitochondrial antiviral signaling protein (MAVS) and Toll/IL-1R domain-containing adaptor molecule-1 (TICAM-1), suggesting dual recognition of LIC-pIC by both sensor adaptor pathways.

CONCLUSIONS

These findings demonstrate that the expression and function of various IFNs differ depending on the animal species and tissues under investigation. Chimeric mice harboring humanized livers demonstrate that IFN-λs play an important role in the defense against human hepatic virus infection.

Activation mechanisms of natural killer cells during influenza virus infection

During early viral infection, activation of natural killer (NK) cells elicits the effector functions of target cell lysis and cytokine production. However, the cellular and molecular mechanisms leading to NK cell activation during viral infections are incompletely understood. In this study, using a model of acute viral infection, we investigated the mechanisms controlling cytotoxic activity and cytokine production in response to influenza (flu) virus. Analysis of cytokine receptor deficient mice demonstrated that type I interferons (IFNs), but not IL-12 or IL-18, were critical for the NK cell expression of both IFN-γ and granzyme B in response to flu infection. Further, adoptive transfer experiments revealed that NK cell activation was mediated by type I IFNs acting directly on NK cells. Analysis of signal transduction molecules showed that during flu infection, STAT1 activation in NK cells was completely dependent on direct type I IFN signaling, whereas STAT4 activation was only partially dependent. In addition, granzyme B induction in NK cells was mediated by signaling primarily through STAT1, but not STAT4, while IFN-γ production was mediated by signaling through STAT4, but not STAT1. Therefore, our findings demonstrate the importance of direct action of type I IFNs on NK cells to mount effective NK cell responses in the context of flu infection and delineate NK cell signaling pathways responsible for controlling cytotoxic activity and cytokine production.

Poly (I:C), an agonist of toll-like receptor-3, inhibits replication of the Chikungunya virus in BEAS-2B cells

Background

Double-stranded RNA (dsRNA) and its mimic, polyinosinic acid: polycytidylic acid [Poly (I:C)], are recognized by toll-like receptor 3 (TLR3) and induce interferon (IFN)-β in many cell types. Poly (I:C) is the most potent IFN inducer. In in vivo mouse studies, intraperitoneal injection of Poly (I:C) elicited IFN-α/β production and natural killer (NK) cells activation. The TLR3 pathway is suggested to contribute to innate immune responses against many viruses, including influenza virus, respiratory syncytial virus, herpes simplex virus 2, and murine cytomegalovirus. In Chikungunya virus (CHIKV) infection, the viruses are cleared within 7–10 days postinfection before adaptive immune responses emerge. The innate immune response is important for CHIKV clearance.

Results

The effects of Poly (I:C) on the replication of CHIKV in human bronchial epithelial cells, BEAS-2B, were studied. Poly (I:C) suppressed cytopathic effects (CPE) induced by CHIKV infection in BEAS-2B cells in the presence of Poly (I:C) and inhibited the replication of CHIKV in the cells. The virus titers of Poly (I:C)-treated cells were much lower compared with those of untreated cells. CHIKV infection and Poly (I:C) treatment of BEAS-2B cells induced the production of IFN-β and increased the expression of anti-viral genes, including IFN-α, IFN-β, MxA, and OAS. Both Poly (I:C) and CHIKV infection upregulate the expression of TLR3 in BEAS-2B cells.

Conclusions

CHIKV is sensitive to innate immune response induced by Poly (I:C). The inhibition of CHIKV replication by Poly (I:C) may be through the induction of TLR3, which triggers the production of IFNs and other anti-viral genes. The innate immune response is important to clear CHIKV in infected cells.

The effect of enzymatically polymerised polyphenols on CD4 binding and cytokine production in murine splenocytes

High-molecular weight polymerised polyphenols have been shown to exhibit anti-influenza virus, anti-HIV, and anti-cancer activities. The purpose of this study was to evaluate the immunomodulating activities of enzymatically polymerised polyphenols, and to clarify the underlying mechanisms of their effects. The cytokine-inducing activity of the enzymatically polymerised polyphenols derived from caffeic acid (CA), ferulic acid (FA), and p-coumaric acid (CoA) was investigated using murine splenocytes. Polymerised polyphenols, but not non-polymerised polyphenols, induced cytokine synthesis in murine splenocytes. Polymerised polyphenols induced several cytokines in murine splenocytes, with interferon-γ (IFN-γ) and granulocyte-macrophage colony-stimulating factor (GM-CSF) being the most prominent. The underlying mechanisms of the effects of the polymerised polyphenols were then studied using neutralising antibodies and fluorescent-activated cell sorting (FACS) analysis. Our results show that polymerised polyphenols increased IFN-γ and GM-CSF production in splenocytes. In addition, the anti-CD4 neutralised monoclonal antibody (mAb) inhibited polymerised polyphenol-induced IFN-γ and GM-CSF secretion. Moreover, polymerised polyphenols bound directly to a recombinant CD4 protein, and FACS analysis confirmed that interaction occurs between polymerised polyphenols and CD4 molecules expressed on the cell surface. In this study, we clearly demonstrated that enzymatic polymerisation confers immunoactivating potential to phenylpropanoic acids, and CD4 plays a key role in their cytokine-inducing activity.

Natural killer cell-produced IFN-γ and TNF-α induce target cell cytolysis through up-regulation of ICAM-1

NK cells control tumor and virus-infected cells through releasing cytotoxic granules and proinflammatory cytokines. IFN-γ and TNF-α secretions and cytotoxicity are regarded as two distinct functions of NK cells with little synergy in between as results of early association of the two functions with distinct subsets of NK populations and of the studies showing target cells developing NK resistance upon IFN-γ treatment. Here, we show that IFN-γ and TNF-α synergistically enhance NK cell cytotoxicity through NF-κB-dependent up-regulation of ICAM-1 expression in target cells, thereby promoting their conjugate formation with NK cells. Neutralizing IFN-γ and TNF-α during cytolysis significantly impaired NK cell lysis of the target cells. Further, tumor cells exhibiting IFN-γ-inducible lysis are generally less-sensitive NK target cells but express inducible levels of ICAM-1. In contrast, sensitive NK targets tend to express higher but less-inducible ICAM-1. Their preferential induction in the lysis of insensitive NK target cells suggests that IFN-γ and TNF-α are functionally linked to and should be regarded as an integral part of NK cytolytic function.

NK cell development, homeostasis and function: parallels with CD8⁺ T cells

Natural killer (NK) cells survey host tissues for signs of infection, transformation or stress and, true to their name, kill target cells that have become useless or are detrimental to the host. For decades, NK cells have been classified as a component of the innate immune system. However, accumulating evidence in mice and humans suggests that, like the B and T cells of the adaptive immune system, NK cells are educated during development, possess antigen-specific receptors, undergo clonal expansion during infection and generate long-lived memory cells. In this Review, we highlight the many stages that an NK cell progresses through during its remarkable lifetime, discussing similarities and differences with its close relative, the cytotoxic CD8(+) T cell.

Defective interfering influenza A virus protects in vivo against disease caused by a heterologous influenza B virus

Influenza A and B viruses are major human respiratory pathogens that contribute to the burden of seasonal influenza. They are both members of the family Orthomyxoviridae but do not interact genetically and are classified in different genera. Defective interfering (DI) influenza viruses have a major deletion of one or more of their eight genome segments, which renders them both non-infectious and able to interfere in cell culture with the production of infectious progeny by a genetically compatible, homologous virus. It has been shown previously that intranasal administration of a cloned DI influenza A virus, 244/PR8, protects mice from various homologous influenza A virus subtypes and that it also protects mice from respiratory disease caused by a heterologous virus belonging to the family Paramyxoviridae. The mechanisms of action in vivo differ, with homologous and heterologous protection being mediated by probable genome competition and type I interferon (IFN), respectively. In the current study, it was shown that 244/PR8 also protects against disease caused by a heterologous influenza B virus (B/Lee/40). Protection from B/Lee/40 challenge was partially eliminated in mice that did not express a functional type I IFN receptor, suggesting that innate immunity, and type I IFN in particular, are important in mediating protection against this virus. It was concluded that 244/PR8 has the ability to protect in vivo against heterologous IFN-sensitive respiratory viruses, in addition to homologous influenza A viruses, and that it acts by fundamentally different mechanisms.

NK cells and immune "memory"

Immunological memory is a hallmark of the adaptive immune system. However, the ability to remember and respond more robustly against a second encounter with the same pathogen has been described in organisms lacking T and B cells. Recently, NK cells have been shown to mediate Ag-specific recall responses in several different model systems. Although NK cells do not rearrange the genes encoding their activating receptors, NK cells experience a selective education process during development, undergo a clonal-like expansion during virus infection, generate long-lived progeny (i.e., memory cells), and mediate more efficacious secondary responses against previously encountered pathogens--all characteristics previously ascribed only to T and B cells in mammals. This review describes past findings leading up to these new discoveries, summarizes the evidence for and characteristics of NK cell memory, and discusses the attempts and future challenges to identify these long-lived memory NK cell populations in humans.

Intratumoral injection of interferon-α and systemic delivery of agonist anti-CD137 monoclonal antibodies synergize for immunotherapy

CD137 artificial costimulation results in complete tumor rejection in several mouse models. Type I interferons (IFN) exert antitumor effects through an array of molecular functions on malignant cells, tumor stroma and immune system cells. The fact that agonist anti-CD137 mAb induce tumor regressions in mice deficient in the unique receptor for Type I IFNs (IFNAR(-/-) ) indicated potential for treatment combinations. Indeed, combination of intratumor injections of mouse IFN-α and intraperitoneal injections of anti-CD137 mAb synergized as seen on subcutaneous lesions derived from the MC38 colon carcinoma, which is resistant to each treatment if given separately. Therapeutic activity was achieved both against lesions directly injected with IFN-α and against distant concomitant tumors. Experiments in bone marrow chimeras prepared with IFNAR(-/-) and WT mice concluded that expression of the receptor for Type I interferons is mainly required on cells of the hematopoietic compartment. Synergistic effects correlated with a remarkable cellular hyperplasia of the tumor draining lymph nodes (TDLNs). Enlarged TDLNs contained more plasmacytoid and conventional dendritic cells (DC) that more readily cross-presented. Importantly, numbers of both DC subtypes inversely correlated with the tumor size. Numbers of CD8 T cells specific for a dominant tumor antigen were increased at TDLNs by each separate treatment but only with slight augments due to the combination. Combined antitumor effects of the therapeutic strategy were also seen on subcutaneous TC-1 tumors established for 24 days before treatment onset. The described strategy is realistic because (i) agents of each kind are clinically available and (ii) equivalent procedures in humans are feasible.

Natural killer cell tolerance persists despite significant reduction of self MHC class I on normal target cells in mice

BACKGROUND

A major group of murine inhibitory receptors on Natural Killer (NK) cells belong to the Ly49 receptor family and recognize MHC class I molecules. Infected or transformed target cells frequently downmodulate MHC class I molecules and can thus avoid CD8(+) T cell attack, but may at the same time develop NK cell sensitivity, due to failure to express inhibitory ligands for Ly49 receptors. The extent of MHC class I downregulation needed on normal cells to trigger NK cell effector functions is not known.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we show that cells expressing MHC class I to levels well below half of the host level are tolerated in an in vivo assay in mice. Hemizygous expression (expression from only one allele) of MHC class I was sufficient to induce Ly49 receptor downmodulation on NK cells to a similar degree as homozygous expression, despite a strongly reduced cell surface level of MHC class I. Co-expression of weaker MHC class I ligands in the host did not have any further effect on the degree of Ly49 downmodulation. Furthermore, a single MHC class I allele could downmodulate up to three Ly49 receptors on individual NK cells. Only when NK cells simultaneously expressed several Ly49 receptors and hemizygous MHC class I levels, a putative threshold for Ly49 downmodulation was reached.

CONCLUSION

Collectively, our findings suggest that in interactions between NK cells and normal untransformed cells, MHC class I molecules are in most cases expressed in excess compared to what is functionally needed to ensure self tolerance and to induce maximal Ly49 downmodulation. We speculate that the reason for this is to maintain a safety margin for otherwise normal, autologous cells over a range of MHC class I expression levels, in order to ensure robustness in NK cell tolerance.

Studying NK cell/dendritic cell interactions

Although NK cells were originally identified as "naturally" active cells believed to follow a cell-autonomous activation program, it is now widely accepted that NK cells need to interact with dendritic cells for their full functional activation and for their homeostasis. In this chapter, we will provide an experimental guide to the analysis of NK cell/DC interactions in vitro and in vivo. We have put special emphasis on the recently developed mouse models allowing the inducible and specific ablation of various subsets of DCs and other myeloid cells.

Tissue-specific homing and expansion of donor NK cells in allogeneic bone marrow transplantation

NK cells have potential therapeutic impact in suppressing graft-versus-host disease (GVHD) and enhancing antitumor effects as a cellular therapy for hematologic malignancies. However, few studies have addressed the trafficking and in vivo behavior of NK cells in murine models of bone marrow transplantation (BMT). We investigated NK cell trafficking and survival following allogeneic and syngeneic BMT using a novel bioluminescence-based imaging strategy. Transplantation of luciferase-expressing NK cells revealed CD62L-mediated trafficking to lymphoid organs and trafficking to GVHD target tissues, as evidenced by in vivo and ex vivo bioluminescence imaging. The NK cells persisted for approximately 4 wk after transplantation in allogeneic recipients, but were not detectable in syngeneic recipients. CFSE-labeling studies showed extensive NK cell proliferation in vivo. Transplanted NK cells up-regulated molecules necessary for homing to the lymph nodes, gastrointestinal tract, and skin, yet did not cause clinical GVHD. This expansion and tissue-specific homing was not solely due to the conditioning regimen, as NK cells proliferated and reached lymphoid and GVHD target tissue in unconditioned allogeneic RAG2(-/-) gamma-chain(-/-) recipients. IL-2 enhanced expansion and antitumor activity of NK cells. These results provide significant insight into the behavior and potential therapeutic impact of NK cells in BMT.

Natural killer cells: remembrances of things past

Recent work has revealed that natural killer cells exhibit a form of memory, previously considered an exclusive property of adaptive immunity. While protective, natural killer cell memory is probably hazier and more fleeting than T cell memory.

Distinct and overlapping patterns of cytokine regulation of thymic and bone marrow-derived NK cell development

Although bone marrow (BM) represents the main site for postnatal NK cell development, recently a distinct thymic-dependent NK cell pathway was identified. These studies were designed to investigate the role of cytokines in regulation of thymic NK cells and to compare with established regulatory pathways of BM-dependent NK cell compartment. The common cytokine receptor gamma-chain (Il2rg) essential for IL-15-induced signaling, and FMS-like tyrosine kinase 3 (FLT3) receptor ligand (Flt3l) were previously identified as important regulatory pathways of the BM NK cell compartment based on lack of function studies in mice, however their complementary action remains unknown. By investigating mice double-deficient in Il2rg and Flt3l (Flt3l(-/-) Il2rg(-/-)), we demonstrate that FLT3L is important for IL2Rg-independent maintenance of both immature BM as well as peripheral NK cells. In contrast to IL-7, which is dispensable for BM but important for thymic NK cells, IL-15 has a direct and important role in both thymic and BM NK cell compartments. Although thymic NK cells were not affected in Flt3l(-/-) mice, Flt3l(-/-)Il2rg(-/-) mice lacked detectable thymic NK cells, suggesting that FLT3L is also important for IL-2Rg-independent maintenance of thymic NK cells. Thus, IL-2Rg cytokines and FLT3L play complementary roles and are indispensable for homeostasis of both BM and thymic dependent NK cell development, suggesting that the cytokine pathways crucial for these two distinct NK cell pathways are largely overlapping.

Interferon-alpha-associated presumed ocular sarcoidosis

BACKGROUND

Interferon alpha, used in the treatment of different viral, autoimmune and malignant diseases, is known to induce a variety of side effects. Recently, induction of sarcoidosis during interferon therapy has been reported. We analyzed patients for uveitis, possibly induced by interferon alpha.

METHODS

We report on three patients who had developed typical signs of ocular sarcoidosis under treatment with interferon alpha for chronic hepatitis C virus infection. In two patients, conventional interferon alpha was used and in another one, pegylated interferon alpha-2b. All patients additionally received ribavirin.

RESULTS

In all three cases, panuveitis was diagnosed. The mean duration of interferon treatment before development of uveitis was 10 months. Clinically, all patients demonstrated granulomatous panuveitis with choroidal granulomas of various sizes. In one case, the uveitis developed together with renal failure, fever and malaise. In this patient, an elevated ACE level was detected. In another patient, the diagnosis of sarcoid induced uveitis was confirmed by positive chest CT scan. The intraocular inflammation was managed with a reduction of the interferon dosage. The therapy with ribavirin was not changed. All patients received topical steroids. Systemic steroids were applied only in the case with systemic disease manifestations.

CONCLUSIONS

Uveitis can be a sign of sarcoidosis induced by interferon alpha. Further studies are required to support the observation that with early diagnosis the prognosis of uveitis seems to be good.

Field production and functional evaluation of chloroplast-derived interferon-alpha2b

Type I interferons (IFNs) inhibit viral replication and cell growth and enhance the immune response, and therefore have many clinical applications. IFN-alpha2b ranks third in world market use for a biopharmaceutical, behind only insulin and erythropoietin. The average annual cost of IFN-alpha2b for the treatment of hepatitis C infection is $26,000, and is therefore unavailable to the majority of patients in developing countries. Therefore, we expressed IFN-alpha2b in tobacco chloroplasts, and transgenic lines were grown in the field after obtaining United States Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS) approval. Stable, site-specific integration of transgenes into chloroplast genomes and homoplasmy through several generations were confirmed. IFN-alpha2b levels reached up to 20% of total soluble protein, or 3 mg per gram of leaf (fresh weight). Transgenic IFN-alpha2b had similar in vitro biological activity to commercially produced PEG-Introntrade mark when tested for its ability to protect cells against cytopathic viral replication in the vesicular stomatitis virus cytopathic effect (VSV CPE) assay and to inhibit early-stage human immunodeficiency virus (HIV) infection. The antitumour and immunomodulating properties of IFN-alpha2b were also seen in vivo. Chloroplast-derived IFN-alpha2b increased the expression of major histocompatibility complex class I (MHC I) on splenocytes and the total number of natural killer (NK) cells. Finally, IFN-alpha2b purified from chloroplast transgenic lines (cpIFN-alpha2b) protected mice from a highly metastatic tumour line. This demonstration of high levels of expression of IFN-alpha2b, transgene containment and biological activity akin to that of commercial preparations of IFN-alpha2b facilitated the first field production of a plant-derived human blood protein, a critical step towards human clinical trials and commercialization.

The antitumor effects of interferon: A personal history

Early experiments showed that administration of mouse interferon preparations inhibited the development of viral-induced or spontaneous viral associated leukemias in mice. Interferon alpha/beta was also shown to inhibit the growth of transplantable tumors of different origins in all strains of mice tested. The finding that interferon alpha/beta inhibited the growth of sublines of tumors selected for resistance to interferon alpha/beta indicated the role of interferon induced host mechanisms in the antitumor effects observed. The different host antitumor mechanisms and especially the interaction of interferon alpha/beta with the immune system have been briefly discussed. Injection of mice with a neutralizing antibody to interferon alpha/beta demonstrated the essential role of endogenous interferon alpha/beta in the defense of the mouse against the development of syngeneic, allogeneic and xenogeneic tumors.

Dendritic cells prime natural killer cells by trans-presenting interleukin 15

Natural killer (NK) cells are important effector cells in the control of infections. The cellular and molecular signals required for NK cell activation in vivo remain poorly defined. By using a mouse model for the inducible ablation of dendritic cells (DCs), we showed that the in vivo priming of NK cell responses to viral and bacterial pathogens required the presence of CD11c(high) DCs. After peripheral Toll-like receptor (TLR) stimulation, NK cells were recruited to local lymph nodes, and their interaction with DCs resulted in the emergence of effector NK cells in the periphery. NK cell priming was dependent on the recognition of type I IFN signals by DCs and the subsequent production and trans-presentation of IL-15 by DCs to resting NK cells. CD11c(high) DC-derived IL-15 was necessary and sufficient for the priming of NK cells. Our data define a unique in vivo role of DCs for the priming of NK cells, revealing a striking and previously unappreciated homology to T lymphocytes of the adaptive immune system.

A Polysaccharide Extracted from Rice Bran Fermented with Lentinus edodes Enhances Natural Killer Cell Activity and Exhibits Anticancer Effects

The objective of this study was to investigate the activation of natural killer (NK) cells and anticancer effects of exo-biopolymer from rice bran cultured with Lentinus edodes [rice bran exo-biopolymer (RBEP)]. Oral administration of RBEP induced the activation of NK cells in a dose-dependent manner. RBEP also prolonged the life spans of mice transplanted with Sarcoma-180 cells and inhibited growing Sarcoma-180 cells in intraperitoneum. Solid tumor growth was also suppressed by oral administration of RBEP in C57/Bl6 mice transplanted with B16/Bl6 melanoma. Intraperitoneal injection of RBEP was more effective than oral administration at the same dosage in mice with transplanted tumor cells. According to this result, when RBEP directly contacts immune cells, the anticancer activity is higher than by indirectly inducing an immune response through oral administration. Therefore, we suggest that the administration of RBEP may be effective for preventing and/or treating cancer through NK cell activation. However, further studies are needed to elucidate the possible mechanisms of the anticancer activity and to investigate the other beneficial effects of RBEP for the development of a new biological response modifier.