Natural killer (NK) cell stimulatory factor increases the cytotoxic activity of NK cells from both healthy donors and human immunodeficiency virus-infected patients

Lymph node CXCR5+ NK cells associate with control of chronic SHIV infection

The persistence of virally infected cells as reservoirs despite effective antiretroviral therapy is a major barrier to an HIV/SIV cure. These reservoirs are predominately contained within cells present in the B cell follicles (BCFs) of secondary lymphoid tissues, a site that is characteristically difficult for most cytolytic antiviral effector cells to penetrate. Here, we identified a population of NK cells in macaque lymph nodes that expressed BCF-homing receptor CXCR5 and accumulated within BCFs during chronic SHIV infection. These CXCR5+ follicular NK cells exhibited an activated phenotype coupled with heightened effector functions and a unique transcriptome characterized by elevated expression of cytolytic mediators (e.g., perforin and granzymes, LAMP-1). CXCR5+ NK cells exhibited high expression of FcγRIIa and FcγRIIIa, suggesting a potential for elevated antibody-dependent effector functionality. Consistently, accumulation of CXCR5+ NK cells showed a strong inverse association with plasma viral load and the frequency of germinal center follicular Th cells that comprise a significant fraction of the viral reservoir. Moreover, CXCR5+ NK cells showed increased expression of transcripts associated with IL-12 and IL-15 signaling compared with the CXCR5- subset. Indeed, in vitro treatment with IL-12 and IL-15 enhanced the proliferation of CXCR5+ granzyme B+ NK cells. Our findings suggest that follicular homing NK cells might be important in immune control of chronic SHIV infection, and this may have important implications for HIV cure strategies.

Brief in vitro IL-12 conditioning of CD8 + T Cells for anticancer adoptive T cell therapy

Cancer immunotherapy represents a potential treatment approach through non-specific and specific enhancement of the immune responses. Adoptive cell therapy (ACT) is a potential modality of immunotherapy that depends on harvesting T cells from the tumor-bearing host, activating them in vitro and infusing them back to the same host. Several cytokines, in particular IL-2, IL-7 and IL-15, have been used to enhance survival T cells in vitro. Although effective, conditioning of T cells in vitro with these cytokines requires long-term culture which results in the loss of expression of their trafficking receptors mainly CD62L. It also results in exhaustion of the activated T cells and reduction in their functions upon adoptive transfer in vivo. Our recent studies and those of other groups showed that brief (3 days) conditioning of CD8⁺ T cells by IL-12 in vitro can result in enhancing function of tumor-reactive CD8⁺ T cells. Adoptive transfer of these IL-12-conditioned CD8⁺ T cells into tumor-bearing mice, preconditioned with cyclophosphamide, 1 day before ACT, induced tumor eradication that was associated with generation of tumor-specific memory response. In this review, we summarize studies that indicated to the superiority of IL-12 as a potential cytokine for conditioning T cells for ACT. In addition, we discuss some of the cellular and molecular mechanisms that govern how IL-12 programs CD8⁺ T cells to enhance their functionality especially in vitro and its implication in combination with other ACT modalities, opening a avenue for the clinical application of this cytokine.

Bracing NK cell based therapy to relegate pulmonary inflammation in COVID-19

The contagiosity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has startled mankind and has brought our lives to a standstill. The treatment focused mainly on repurposed immunomodulatory and antiviral agents along with the availability of a few vaccines for prophylaxis to vanquish COVID-19. This seemingly mandates a deeper understanding of the disease pathogenesis. This necessitates a plausible extrapolation of cell-based therapy to COVID-19 and is regarded equivalently significant. Recently, correlative pieces of clinical evidence reported a robust decline in lymphocyte count in severe COVID-19 patients that suggest dysregulated immune responses as a key element contributing to the pathophysiological alterations. The large granular lymphocytes also known as natural killer (NK) cells play a heterogeneous role in biological functioning wherein their frontline action defends the body against a wide array of infections and tumors. They prominently play a critical role in viral clearance and executing immuno-modulatory activities. Accumulated clinical evidence demonstrate a decrease in the number of NK cells in circulation with or without phenotypical exhaustion. These plausibly contribute to the progression of pulmonary inflammation in COVID-19 pneumonia and result in acute lung injury. In this review, we have outlined the present understanding of the immunological response of NK cells in COVID-19 infection. We have also discussed the possible use of these powerful biological cells as a therapeutic agent in view of preventing immunological harms of SARS-CoV-2 and the current challenges in advocating NK cell therapy for the same.

Exploring the Pivotal Immunomodulatory and Anti-Inflammatory Potentials of Glycyrrhizic and Glycyrrhetinic Acids

Licorice extract is a Chinese herbal medication most often used as a demulcent or elixir. The extract usually consists of many components but the key ingredients are glycyrrhizic (GL) and glycyrrhetinic acid (GA). GL and GA function as potent antioxidants, anti-inflammatory, antiviral, antitumor agents, and immuneregulators. GL and GA have potent activities against hepatitis A, B, and C viruses, human immunodeficiency virus type 1, vesicular stomatitis virus, herpes simplex virus, influenza A, severe acute respiratory syndrome-related coronavirus, respiratory syncytial virus, vaccinia virus, and arboviruses. Also, GA was observed to be of therapeutic valve in human enterovirus 71, which was recognized as the utmost regular virus responsible for hand, foot, and mouth disease. The anti-inflammatory mechanism of GL and GA is realized via cytokines like interferon-γ, tumor necrotizing factor-α, interleukin- (IL-) 1β, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, and IL-17. They also modulate anti-inflammatory mechanisms like intercellular cell adhesion molecule 1 and P-selectin, enzymes like inducible nitric oxide synthase (iNOS), and transcription factors such as nuclear factor-kappa B, signal transducer and activator of transcription- (STAT-) 3, and STAT-6. Furthermore, DCs treated with GL were capable of influencing T-cell differentiation toward Th1 subset. Moreover, GA is capable of blocking prostaglandin-E2 synthesis via blockade of cyclooxygenase- (COX-) 2 resulting in concurrent augmentation nitric oxide production through the enhancement of iNOS2 mRNA secretion in Leishmania-infected macrophages. GA is capable of inhibiting toll-like receptors as well as high-mobility group box 1.

Single injection of IL-12 coacervate as an effective therapy against B16-F10 melanoma in mice

Melanoma is the deadliest type of skin cancer with one of the fastest increasing incidence rates among solid tumors. The use of checkpoint inhibitors (e.g. αPD-1 antibody) has recently emerged as a viable alternative to conventional modes of therapy. However, increasing evidence points towards the need for a tumor priming step to improve intratumoral immune cell infiltration. IL-12 is an immune-activating cytokine with such potential and was explored in earlier clinical trials as a highly concentrated systemic infusion. This unfortunately led to severe adverse effects. From this perspective, the localization and gradual release of such a potent immunotherapeutic agent in the tumor microenvironment is desired. This manuscript reports the use of a heparin-based complex coacervate to deliver IL-12, in which heparin-binding motifs on IL-12 allow for its effective encapsulation. IL-12-encapsulated complex coacervates significantly improved the bioactivity of IL-12 and provided protection from proteolytic cleavage in-vitro. Indeed, a single injection of IL-12 coacervate significantly inhibits the in-vivo growth of treated and untreated, contralateral tumor growth in a syngeneic B16F10 mouse melanoma model. Furthermore, tumors in mice receiving IL-12 complex coacervate treatment displayed increased infiltration by natural killer (NK) cells and CD8α+ T cells, and a decreased presence of CD4+Foxp3+ regulatory T cells. This study provides proof-of-concept data supporting the use of complex coacervates for sustained delivery of immunostimulatory proteins as an effective therapeutic strategy against disseminated tumors.

The Prognostic Role of Peripheral Lymphocyte Subsets in Patients With Acute Pancreatitis

BACKGROUND

The prognostic role of peripheral lymphocyte subsets in early stage of acute pancreatitis (AP) is unknown.

METHODS

After enrollment, blood samples were collected in the first 24 hours of the onset of AP in 164 patients. The lymphocyte count and the percentage of CD3⁺, CD3⁺CD4⁺, CD3⁺CD8⁺, CD3^-CD19⁺and CD3^-CD (16 + 56)⁺ cells were assessed.

RESULTS

Reduction of the lymphocyte count and the percentage of CD3⁺CD8⁺ and CD3^-CD (16 + 56)⁺ cells within 24 hours of the onset of AP as well as an increase in the percentage of CD3⁺ and CD3⁺CD4⁺ cells were observed. The percentage of CD3^-CD (16 + 56)⁺ cells had the highest accuracy in prediction of AP severity.

CONCLUSIONS

Marked changes of the percentages of lymphocyte subset were found in peripheral blood in the early stage of AP. The percentage of CD3^-CD (16 + 56)⁺ cells in peripheral blood could be a potent prognostic predictor.

Tumor-Derived α-Fetoprotein Directly Drives Human Natural Killer-Cell Activation and Subsequent Cell Death

Hepatocellular carcinoma (HCC) patients with reduced natural killer (NK)-cell numbers and function have been shown to have a poor disease outcome. Mechanisms underlying NK-cell deficiency and dysfunction in HCC patients remain largely unresolved. α-Fetoprotein (AFP) is an oncofetal antigen produced by HCC. Previous studies demonstrated that tumor-derived AFP (tAFP) can indirectly impair NK-cell activity by suppressing dendritic cell function. However, a direct tAFP effect on NK cells remains unexplored. The purpose of this study was to examine the ability of cord blood-derived AFP (nAFP) and that of tAFP to directly modulate human NK-cell activity and longevity in vitro Short-term exposure to tAFP and, especially, nAFP proteins induced a unique proinflammatory, IL2-hyperresponsive phenotype in NK cells as measured by IL1β, IL6, and TNF secretion, CD69 upregulation, and enhanced tumor cell killing. In contrast, extended coculture with tAFP, but not nAFP, negatively affected long-term NK-cell viability. NK-cell activation was directly mediated by the AFP protein itself, whereas their viability was affected by hydrophilic components within the low molecular mass cargo that copurified with tAFP. Identification of the distinct impact of circulating tAFP on NK-cell function and viability may be crucial to developing a strategy to ameliorate HCC patient NK-cell functional deficits. Cancer Immunol Res; 5(6); 493-502. ©2017 AACR.

Cardiac Arrest Disrupts Caspase-1 and Patterns of Inflammatory Mediators Differently in Skin and Muscle Following Localized Tissue Injury in Rats: Insights from Data-Driven Modeling

BACKGROUND

Trauma often cooccurs with cardiac arrest and hemorrhagic shock. Skin and muscle injuries often lead to significant inflammation in the affected tissue. The primary mechanism by which inflammation is initiated, sustained, and terminated is cytokine-mediated immune signaling, but this signaling can be altered by cardiac arrest. The complexity and context sensitivity of immune signaling in general has stymied a clear understanding of these signaling dynamics.

METHODOLOGY/PRINCIPAL FINDINGS

We hypothesized that advanced numerical and biological function analysis methods would help elucidate the inflammatory response to skin and muscle wounds in rats, both with and without concomitant shock. Based on the multiplexed analysis of inflammatory mediators, we discerned a differential interleukin (IL)-1α and IL-18 signature in skin vs. muscle, which was suggestive of inflammasome activation in the skin. Immunoblotting revealed caspase-1 activation in skin but not muscle. Notably, IL-1α and IL-18, along with caspase-1, were greatly elevated in the skin following cardiac arrest, consistent with differential inflammasome activation.

CONCLUSION/SIGNIFICANCE

Tissue-specific activation of caspase-1 and the NLRP3 inflammasome appear to be key factors in determining the type and severity of the inflammatory response to tissue injury, especially in the presence of severe shock, as suggested via data-driven modeling.

Lysis of HIV-1-infected autologous CD4+ primary T cells by interferon-alpha-activated NK cells requires NKp46 and NKG2D

OBJECTIVE

Autologous HIV-1-infected CD4 primary T cells (aHIVCD4) have been shown to be largely resistant to natural killer (NK)-cell-mediated lysis because of viral strategies of immune evasion. We have previously shown that a preactivation of NK cells with plasmacytoid dendritic cells can significantly augment lysis of aHIVCD4 through a mechanism dependent on interferon-alpha (IFN-α).

DESIGN

The goal of the present study is to identify the specific NK-activating receptors involved in NK lysis of aHIVCD4 following IFN-α activation.

METHODS

Peripheral blood mononuclear cells (PBMC) were incubated with aHIVCD4 to induce the secretion of endogenous levels of IFN-α and drive NK activation. We then utilized a standard chromium lysis assay to assess the degree of IFN-α-activated lysis of aHIVCD4 in the presence or absence of masking antibodies to a panel of NK-activating receptors and co-receptors.

RESULTS

Direct recognition of HIV-1-infected, but not uninfected, autologous CD4 primary T cells by PBMC induced the secretion IFN-α (median 2280 pg/ml, P < 0.001, n = 9) that, in turn, activated NK cells (P < 0.001, n = 12) and significantly increased their cytolytic potential against aHIVCD4 (P < 0.01, n = 12). The masking of NKp46 (P < 0.01, n = 8) and NKG2D (P < 0.05, n = 8), but not 2B4, NTBA, NKp30 or NKp44, significantly reduced IFN-α-activated lysis of aHIVCD4.

CONCLUSIONS

Taken together, these results demonstrate that endogenous levels of IFN-α secreted by plasmacytoid dendritic cells induce NK cells to lyse aHIVCD4 via the engagement of NKp46 and NKG2D.

The natural product phyllanthusmin C enhances IFN-γ production by human NK cells through upregulation of TLR-mediated NF-κB signaling

Natural products are a major source for cancer drug development. NK cells are a critical component of innate immunity with the capacity to destroy cancer cells, cancer-initiating cells, and clear viral infections. However, few reports describe a natural product that stimulates NK cell IFN-γ production and unravel a mechanism of action. In this study, through screening, we found that a natural product, phyllanthusmin C (PL-C), alone enhanced IFN-γ production by human NK cells. PL-C also synergized with IL-12, even at the low cytokine concentration of 0.1 ng/ml, and stimulated IFN-γ production in both human CD56(bright) and CD56(dim) NK cell subsets. Mechanistically, TLR1 and/or TLR6 mediated PL-C's activation of the NF-κB p65 subunit that in turn bound to the proximal promoter of IFNG and subsequently resulted in increased IFN-γ production in NK cells. However, IL-12 and IL-15Rs and their related STAT signaling pathways were not responsible for the enhanced IFN-γ secretion by PL-C. PL-C induced little or no T cell IFN-γ production or NK cell cytotoxicity. Collectively, we identify a natural product with the capacity to selectively enhance human NK cell IFN-γ production. Given the role of IFN-γ in immune surveillance, additional studies to understand the role of this natural product in prevention of cancer or infection in select populations are warranted.

Cytokines in cancer immunotherapy

Cytokines are molecular messengers that allow the cells of the immune system to communicate with one another to generate a coordinated, robust, but self-limited response to a target antigen. The growing interest over the past two decades in harnessing the immune system to eradicate cancer has been accompanied by heightened efforts to characterize cytokines and exploit their vast signaling networks to develop cancer treatments. The goal of this paper is to review the major cytokines involved in cancer immunotherapy and discuss their basic biology and clinical applications. The paper will also describe new cytokines in pre-clinical development, combinations of biological agents, novel delivery mechanisms, and potential directions for future investigation using cytokines.

Selective serotonin reuptake inhibitor suppression of HIV infectivity and replication

OBJECTIVE

To test the hypothesis that the selective serotonin reuptake inhibitor (SSRI) citalopram would down-regulate human immunodeficiency virus (HIV) infectivity and that the greatest effects would be seen in people with depression. Depression is a risk factor for morbidity and mortality in HIV/acquired immune deficiency syndrome. Serotonin (5-HT) neurotransmission has been implicated in the pathobiology of depression, and pharmacologic therapies for depression target this system. The 5-HT transporter and 5-HT receptors are widely distributed throughout the central nervous and immune systems. Depression has been associated with suppression of natural killer cells and CD8(+) lymphocytes, key regulators of HIV infection.

METHODS

Ex vivo models for acute and chronic HIV infection were used to study the effects of citalopram on HIV viral infection and replication in 48 depressed and nondepressed women. For both the acute and chronic infection models, HIV reverse transcriptase activity was measured in the citalopram treatment condition and the control condition.

RESULTS

The SSRI significantly down-regulated the reverse transcriptase response in both the acute and chronic infection models. Specifically, citalopram significantly decreased the acute HIV infectivity of macrophages. Citalopram also significantly decreased HIV viral replication in the latently infected T-cell line and in the latently infected macrophage cell line. There was no difference in down-regulation by depression status.

CONCLUSIONS

These studies suggest that an SSRI enhances natural killer/CD8 noncytolytic HIV suppression in HIV/acquired immune deficiency syndrome and decreases HIV viral infectivity of macrophages, ex vivo, suggesting the need for in vivo studies to determine a potential role for agents targeting serotonin in the host defense against HIV.

PRDM1/Blimp-1 controls effector cytokine production in human NK cells

NK cells are major effectors of the innate immune response through cytolysis and bridge to the adaptive immune response through cytokine release. The mediators of activation are well studied; however, little is known about the mechanisms that restrain activation. In this report, we demonstrate that the transcriptional repressor PRDM1 (also known as Blimp-1 or PRDI-BF1) is a critical negative regulator of NK function. Three distinct PRDM1 isoforms are selectively induced in the CD56(dim) NK population in response to activation. PRDM1 coordinately suppresses the release of IFN-γ, TNF-α, and TNF-β through direct binding to multiple conserved regulatory regions. Ablation of PRDM1 expression leads to enhanced production of IFN-γ and TNF-α but does not alter cytotoxicity, whereas overexpression blocks cytokine production. PRDM1 response elements are defined at the IFNG and TNF loci. Collectively, these data demonstrate a key role for PRDM1 in the negative regulation of NK activation and position PRDM1 as a common regulator of the adaptive and innate immune response.

IL-23 and IL-12p70 production by monocytes and dendritic cells in primary HIV-1 infection

IL-12 enhances protective responses against HIV replication. Its production after in vitro stimulation is defective in chronic HIV infection, but higher responses can be found. IL-23 shares the p40 chain and some properties with IL-12 and enhances Th17 responses, but its role in HIV infection is unknown. The production of IL-12 and IL-23 and the respective contribution of monocytes and myeloid conventional DC (cDCs) during primary HIV infection were determined. Sixteen patients included in the French PRIMO-ANRS Cohort without antiretroviral treatment were followed prospectively and compared with uninfected donors. Intracellular p40 expression by monocytes and cDCs, analyzed by flow cytometry, was transiently increased in monocytes and cDCs in response to LPS and more consistently, in monocytes in response to LPS + IFN-gamma. IL-23 production, measured by ELISA after PBMC stimulation, was induced by LPS in strong correlation with VLs. IL-12p70 production required the addition of IFN-gamma and was transiently increased in patients compared with controls in correlation with VLs, whereas IL-23 was increased sustainedly. Therefore, an apparent domination of IL-23 over IL-12 responses occurred throughout primary HIV infection, and a potential restoration of IL-12 responses might be expected from a treatment mimicking activated T cell signals.

Inability of plasmacytoid dendritic cells to directly lyse HIV-infected autologous CD4+ T cells despite induction of tumor necrosis factor-related apoptosis-inducing ligand

The function of plasmacytoid dendritic cells (PDC) in chronic human immunodeficiency virus type 1 (HIV-1) infection remains controversial with regard to its potential for sustained alpha interferon (IFN-alpha) production and induction of PDC-dependent tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-mediated cytotoxicity of HIV-infected cells. We address these areas by a study of chronically HIV-1-infected subjects followed through antiretroviral therapy (ART) interruption and by testing PDC cytolytic function against autologous HIV-infected CD4(+) T cells. Rebound in viremia induced by therapy interruption showed a positive association between TRAIL and viral load or T-cell activation, but comparable levels of plasma IFN-alpha/beta were found in viremic ART-treated and control subjects. While PDC from HIV-infected subjects expressed less interferon regulator factor 7 (IRF-7) and produced significantly less IFN-alpha upon Toll-like receptor 7/9 (TLR7/9) engagement than controls, membrane TRAIL expression in PDC from HIV(+) subjects was increased. Moreover, no significant increase in death receptor 5 (DR5) expression was seen in CD4(+) T cells from viremic HIV(+) subjects compared to controls or following in vitro infection/exposure to infectious and noninfectious virus or exogenous IFN-alpha, respectively. Although activated PDC killed the DR5-expressing HIV-infected Sup-T1 cell line, PDC did not lyse primary autologous HIV(+) CD4(+) T cells yet could provide accessory help for NK cells in killing HIV-infected autologous CD4(+) T cells. Taken together, our data show a lack of sustained high levels of soluble IFN-alpha in chronic HIV-1 infection in vivo and document a lack of direct PDC cytolytic activity against autologous infected or uninfected CD4(+) T cells.

Immune activation and IL-12 production during acute/early HIV infection in the absence and presence of highly active, antiretroviral therapy

Suppressed IL-12 production and maladaptive immune activation, both of which are ameliorated by successful highly active antiretroviral therapy (HAART), are thought to play important roles in the immunopathogenesis of chronic HIV infection. Despite the important effects of the immunological and virological events of early HIV infection on subsequent disease progression, IL-12 production and immune activation in early infection remain under-defined. To quantify IL-12 production and immune activation during acute/early HIV infection, in the presence and absence of HAART, we performed a prospective, longitudinal study of participants in the Baltimore site of the Acute Infection and Early Disease Research Program, with cross-sectional comparison to healthy control subjects. PBMC cytokine productive capacity and plasma immune activation markers [soluble CD8 (sCD8), sCD4, granzyme B, neopterin, beta2-microglobulin, sIL-2R, sTNFRI, sTNFRII, and IL-12p70] were quantified by ELISA. Notably, PBMC from patients with acute/early HIV infection exhibited in vivo IL-12p70 production along with increased, maximal in vitro IL-12 production. Further, despite evidence from plasma markers of generalized immune activation, no elevation in plasma levels of sCD4 was observed, suggesting relative blunting of in vivo CD4+ T cell activation from the beginning of HIV infection. Finally, despite successful virological responses to HAART, heightened in vivo CD8+ T cell activation, IL-12 production, and IFN activity were sustained for at least 6 months during primary HIV infection. These data underscore the need for comparative mechanistic analysis of the immunobiology of early and chronic HIV infection.

A randomized clinical trial of alternative stress management interventions in persons with HIV infection

Research in psychoneuroimmunology suggests that immunosuppression associated with perceived stress may contribute to disease progression in persons with HIV infection. While stress management interventions may enhance immune function, few alternative approaches have yet been tested. This randomized clinical trial was conducted to test effects of three 10-week stress management approaches--cognitive-behavioral relaxation training (RLXN), focused tai chi training (TCHI), and spiritual growth groups (SPRT)--in comparison to a wait-listed control group (CTRL) among 252 individuals with HIV infection. Using repeated measures mixed modeling, the authors found that in comparison to the CTRL group, (a) both the RLXN and TCHI groups used less emotion-focused coping, and (b) all treatment groups had augmented lymphocyte proliferative function. Despite modest effects of the interventions on psychosocial functioning, robust findings of improved immune function have important clinical implications, particularly for persons with immune-mediated illnesses.

The two faces of interleukin 12: a pro-inflammatory cytokine and a key immunoregulatory molecule produced by antigen-presenting cells

Interleukin 12 (IL-12) is produced by phagocytic cells, antigen-presenting cells and B lymphocytes in response to bacteria or intracellular parasites. IL-12 acts on T and natural killer (NK) cells inducing: production of cytokines, particularly gamma-interferon (IFN-gamma); proliferation; and enhancement of cell-mediated cytotoxicity. Early in infection, IL-12 acts as a proinflammatory cytokine and induces IFN-gamma production by NK and T cells. IFN-gamma activates the phagocytes and increases their ability to produce IL-12. Unlike IFN-gamma, IL-10, IL-4, IL-13 and transforming growth factor beta are negative regulators of the production and activity of IL-12. IL-12 sets the stage for the ensuing adaptive immune response by stimulating the generation of T helper 1 (Th1) cells. It is likely that the balance between IL-12 (favouring a Th1 response) and IL-4 (favouring a Th2 response) determines the eventual outcome of the Th1/Th2 dichotomy during an immune response. HIV-infected patients have a deficient production of IL-12, even at early stages of the disease. However, exogenous IL-12 can improve the deficient immune responsiveness of these patients' T and NK cells in vitro, suggesting a possible role of the IL-12 deficiency in HIV disease pathogenesis and a potential therapeutic role of IL-12 both against opportunistic pathogens and HIV infection itself.

Baseline Viral Load and Immune Activation Determine the Extent of Reconstitution of Innate Immune Effectors in HIV-1-Infected Subjects Undergoing Antiretroviral Treatment

We analyzed dendritic cell (DC) and NK cell compartments in relation to CD4 recovery in 21 HIV-infected subjects followed to <50 copies/ml once starting antiretroviral therapy (ART) and observed for 52 wk of sustained suppression. Although CD4 counts increased in all subjects in response to ART, we observed a restoration of functional plasmacytoid DC (PDC) after 52 wk of sustained suppression under ART (from 1850 cells/ml to 4550 cells/ml) to levels comparable to controls (5120 cells/ml) only in subjects with a low baseline viral load, which also rapidly suppressed to <50 copies/ml upon <or=60 days from ART initiation. Recovery of PDC at week 52 correlates with level of CD95 expression on CD8 T cells and PDC frequency following first ART suppression. NK cytotoxic activity increased rapidly upon viral suppression (VS) and correlated with PDC function at week 52. However, restoration of total NK cells was incomplete even after 52 wk on ART (73 cells/mul vs 122 cells/mul in controls). Direct reconstitution experiments indicate that NK cytotoxic activity against virally infected target cells requires DC/NK cooperation, and can be recovered upon sustained VS and recovery of functional PDC (but not myeloid DC) from ART-suppressed subjects. Our data indicate that viremic HIV-infected subjects may have different levels of reconstitution of DC and NK-mediated function following ART, with subjects with lower initial viremia and the greatest reduction of baseline immune activation at VS achieving the greatest level of innate effector cell reconstitution.

Single-Stranded RNA Derived from HIV-1 Serves as a Potent Activator of NK Cells

Persistent immune activation is a hallmark of chronic viremic HIV-1 infection. Activation of cells of the innate immune system, such as NK cells, occurs rapidly upon infection, and is sustained throughout the course of the disease. However, the precise underlying mechanism accounting for the persistent HIV-1-induced activation of NK cells is poorly understood. In this study, we assessed the role of uridine-rich ssRNA derived from the HIV-1 long terminal repeat (ssRNA40) on activation of NK cells via TLR7/8. Although dramatic activation of NK cells was observed following stimulation of PBMC with ssRNA40, negligible activation was observed following stimulation of purified NK cells despite their expression of TLR8 mRNA and protein. The functional activation of NK cells by this HIV-1-encoded TLR7/8 ligand could not be reconstituted with exogenous IL-12, IFN-alpha, or TNF-alpha, but was critically dependent on the direct contact of NK cells with plasmacytoid dendritic cells or CD14(+) monocytes, indicating an important level of NK cell cross-talk and regulation by accessory cells during TLR-mediated activation. Coincubation of monocyte/plasmacytoid dendritic cells, NK cells, and ssRNA40 potentiated NK cell IFN-gamma secretion in response to MHC-devoid target cells. Studies using NK cells derived from individuals with chronic HIV-1 infection demonstrated a reduction of NK cell responsiveness following stimulation with TLR ligands in viremic HIV-1 infection. These data demonstrate that HIV-1-derived TLR ligands can contribute to the immune activation of NK cells and may play an important role in HIV-1-associated immunopathogenesis and NK cell dysfunction observed during acute and chronic viremic HIV-1 infection.

IL-28 elicits antitumor responses against murine fibrosarcoma

IL-28 is a recently described antiviral cytokine. In this study, we investigated the biological effects of IL-28 on tumor growth to evaluate its antitumor activity. IL-28 or retroviral transduction of the IL-28 gene into MCA205 cells did not affect in vitro growth, whereas in vivo growth of MCA205IL-28 was markedly suppressed along with survival advantages when compared with that of controls. When the metastatic ability of IL-28-secreting MCA205 cells was compared with that of controls, the expression of IL-28 resulted in a potent inhibition of metastases formation in the lungs. IL-28-mediated suppression of tumor growth was mostly abolished in irradiated mice, indicating that irradiation-sensitive cells, presumably immune cells, are primarily involved in the IL-28-induced suppression of tumor growth. In vivo cell depletion experiments displayed that polymorphonuclear neutrophils, NK cells, and CD8 T cells, but not CD4 T cells, play an equal role in the IL-28-mediated inhibition of in vivo tumor growth. Consistent with these findings, inoculation of MCA205IL-28 into mice evoked enhanced IFN-gamma production and cytotoxic T cell activity in spleen cells. Antitumor action of IL-28 is partially dependent on IFN-gamma and is independent of IL-12, IL-17, and IL-23. IL-28 increased the total number of splenic NK cells in SCID mice and enhanced IL-12-induced IFN-gamma production in vivo and expanded spleen cells in C57BL/6 mice. Moreover, IL-12 augmented IL-28-mediated antitumor activity in the presence or absence of IFN-gamma. These findings indicate that IL-28 has bioactivities that induce innate and adaptive immune responses against tumors.

Vaccination with novel combinations of anti-HER2/neu cytokines fusion proteins and soluble protein antigen elicits a protective immune response against HER2/neu expressing tumors

We have previously demonstrated that anti-HER2/neu IgG3-(IL-2), (IL-12)-IgG3, or IgG3-(GM-CSF) antibody fusion proteins (mono-AbFPs) elicit anti-tumor activity against murine tumors expressing HER2/neu when used as adjuvants of extracellular domain of HER2/neu (ECD(HER2)) protein vaccination. We have now studied the effect of combinations of IL-2 and IL-12 or IL-12 and GM-CSF mono-AbFPs during vaccination with ECD(HER2). In addition, we developed two novel anti-HER2/neu IgG3-cytokine fusion proteins in which IL-2 and IL-12 or IL-12 and GM-CSF were fused to the same IgG3 molecule (bi-AbFPs). (IL-12)-IgG3-(IL-2) and (IL-12)-IgG3-(GM-CSF) were properly assembled and retained both cytokine activity and the ability to bind antigen. Vaccination of mice with ECD(HER2) and a combination of cytokines as either bi-AbFPs or two mono-AbFPs activated both Thl and Th2 immune responses and resulted in significant protection against challenge with a HER2/neu expressing tumor. Our results suggest that this approach will be effective in the prevention and/or treatment of HER2/neu expressing tumors.

Interleukin-15 enhances cytotoxicity, receptor expression, and expansion of neonatal natural killer cells in long-term culture

Newborn infants have a higher susceptibility to various pathogens due to developmental defects in their host defense system, including deficient natural killer (NK) cell function. In this study, the effects of interleukin-15 (IL-15) on neonatal NK cells was examined for up to 12 weeks in culture. The cytotoxicity of fresh neonatal mononuclear cells (MNC) as assayed by K562 cell killing is initially much less than that of adult MNC but increases more than eightfold after 2 weeks of culture with IL-15 to a level equivalent to that of adult cells. This high level of cytotoxicity was maintained for up to 12 weeks. In antibody-dependent cellular cytotoxicity (ADCC) assays using CEM cells coated with human immunodeficiency virus gp120 antigen, IL-15 greatly increased ADCC lysis by MNC from cord blood. IL-15 increased expression of the CD16+ CD56+ NK markers of cord MNC fivefold after 5 weeks of incubation. Cultures of neonatal MNC with IL-15 for up to 10 weeks resulted in a unique population of CD3- CD8+ CD56+ cells (more than 60%), which are not present in fresh cord MNC. These results show that IL-15 can stimulate neonatal NK cells and sustain their function for several weeks, which has implications for the clinical use of IL-15.

Interleukin-12 therapy reduces the number of immune cells and pathology in lungs of mice infected with Mycobacterium tuberculosis

Alternate modalities for the treatment of Mycobacterium tuberculosis are needed due to the rise in numbers of immunosuppressed individuals at risk for serious disease and the increasing prevalence of multidrug-resistant isolates. Interleukin-12 (IL-12) has been shown to improve immune responses against M. tuberculosis infection in both humans and mice. Previous studies using high-dose IL-12 in various disease models reported a paradoxical immunosuppression. We demonstrate here that exogenous administration of IL-12 for 8 weeks after an aerosolized low dose of M. tuberculosis results in increased survival and decreased pulmonary bacterial loads for CD4-T-cell-deficient mice, most likely due to an early increase in gamma interferon. IL-12 treatment did not impair or enhance the ability of the wild-type mice to control infection, as measured by bacterial numbers. Two novel findings are reported here regarding exogenous IL-12 therapy for M. tuberculosis infections: (i). IL-12 treatment resulted in decreased numbers of immune cells and reduced frequencies of lymphocytes (CD8(+), CD4(+), and NK cells) in the lungs of infected mice and (ii). IL-12 therapy reduced the pathology of M. tuberculosis-infected lungs, as granulomas were smaller and less numerous. These studies support an immunoregulatory role for IL-12 in tuberculosis.

What Is Going on with Natural Killer Cells in HIV Infection?

Natural killer (NK) cells represent 10-15% of circulating lymphocytes and are important mediators of both natural and adaptive immunity. They participate in immune surveillance against malignancies and virus infection and are involved in the complex immune responses of transplantation, autoimmune diseases and immunosuppression. They can also mediate physiological regulation of hematopoiesis, homeostasis of reproduction and placentation. In recent years new advances have been achieved in understanding the mechanisms whereby NK cells exert their cytotoxic and regulatory roles. Here, we review the physiology of NK cells with special attention to its role in HIV infection.

The use of growth factors and cytokines to treat opportunistic infections in HIV-1 disease

The success of highly active antiretroviral therapy (HAART) in reducing AIDS-related mortality means that in regions where HAART is available, HIV infection may now be regarded as a chronic disease. However the inability of HAART to eliminate HIV-1 from various anatomical and cellular reservoirs within the body means that HIV-infected individuals require life-long treatment with therapy that can have significant side effects. Management of HIV disease is therefore increasingly focused on drug-related toxicities and the improvement of current HAART regimens. Here we review the potential use of immunomodulatory cytokines to directly or indirectly stimulate the mononuclear phagocyte system as adjuncts to current HIV treatment as well as their use in the management of opportunistic infections in individuals who develop immunodeficiency. We argue that cytokines, which stimulate mononuclear phagocyte activity against opportunistic pathogens, may be useful for the treatment of individuals who develop recurrent opportunistic infections. Cytokines may act synergistically with antimicrobial agents to improve outcomes, which is of particular importance since recurrent infections frequently result in resistance to standard antimicrobial treatments. Before their use can be advocated however, given their toxicity and significant cost, the potential benefits of cytokines must be demonstrated in larger clinical trials.

Proinflammatory Cytokines in the Treatment of Bacterial and Fungal Infections

Mortality due to severe bacterial infections has not been markedly effected by the introduction of new antimicrobial drugs over the last 30-40 years. This has emphasized the need for development of new therapeutic strategies to combat sepsis. The outcome of an infection depends on two factors: the growth of the microorganisms (including the effect of antibacterial drugs), and the host's defensive response to the invading organism. It is known that injection of bacterial products into experimental animals leads to enhanced nonspecific resistance to a variety of microorganisms. The discovery of the specific mediators responsible for modulation of host defense has created new possibilities for the development of alternative treatment strategies. Molecules such as interleukins, interferons, tumor necrosis factors and hematopoietic growth factors have become available in recombinant form, and their therapeutic potential in various infectious diseases has been tested in various experimental models of infections. Initial data in various patient groups indicate that adjunctive therapy with recombinant proinflammatory cytokines may have beneficial effects in the treatment of bacterial and fungal infections.

Association of depression, CD8+ T lymphocytes, and natural killer cell activity: implications for morbidity and mortality in Human immunodeficiency virus disease

A heightened risk of mood disorders, such as major depression, and acute depressive symptoms has been observed among HIV-seropositive individuals since the start of the AIDS epidemic, and an accumulating body of data now shows that depression may have an impact on morbidity and mortality among individuals with HIV disease. Although the specific physiologic mechanisms involved in this process have not been delineated, there is some evidence to suggest that certain components of innate immunity, including killer lymphocytes such as CD8+ T lymphocytes and natural killer cells, may represent key pathways through which depression affects HIV disease progression. This paper reviews some of the main studies examining the effects of depression on immunity and HIV disease progression and discusses the potential role of killer lymphocytes as an underlying mechanism by which depression may impact morbidity and mortality.

Effects of stress management on PNI-based outcomes in persons with HIV disease

A pretest-posttest, repeated-measures design was used to evaluate the effects of two stress management interventions on a battery of outcomes derived from a psychoneuroimmunological (PNI) framework. The effects of cognitive-behavioral relaxation training groups (CBSM) and social support groups (SSG) were compared with a WAIT-listed control group on the outcomes of psychosocial functioning, quality of life, neuroendocrine mediation, and somatic health. Participants were 148 individuals (119 men, 29 women), diagnosed with HIV disease; 112 (76%) completing the study groups. Using analysis of covariance, the CBSM group was found to have significantly higher postintervention emotional well-being and total quality-of-life scores than did either the SSG or WAIT groups. SSG participants had significantly lower social/family well-being scores immediately postintervention and lower social support scores after 6 months. The findings point to a pressing need for further, well-controlled research with these common intervention modalities.

Interleukin 12-augmented T cell proliferation of peripheral blood mononuclear cells from HIV-seropositive individuals is associated with interleukin 12 receptor beta 2 upregulation

Interleukin 12 (IL-12) production is believed to be impaired in individuals with HIV infection and this impairment manifests early in disease, when the CD4(+) cell counts are within normal values. The reduced antigen-specific and mitogen-stimulated T cell-proliferative responses that occur in HIV infection can be corrected by the addition of recombinant human interleukin 12 (rhIL-12). As the IL-12 receptor (IL-12R) is central to the IL-12 signaling pathway, we examined whether the augmentation of antigen-specific proliferation of HIV(+) peripheral blood mononuclear cells (PBMCs) related to altered IL-12R expression. rhIL-12 augmented antigen-specific proliferation of HIV(+) PBMCs but not of HIV(-) PBMCs. Examination of resting PBMCs from HIV(+) and HIV(-) donors showed that neither of these populations expressed IL-12R beta 1 or IL-12R beta 2 chains on their cell surface as detected by flow cytometry. However, examination of mRNA showed that both IL-12R beta 1 and IL-12R beta 2 mRNAs were markedly reduced in HIV(+) PBMCs when compared with HIV(-) PBMCs. After mitogen activation there was an increase in IL-12R beta 1 expression on the cell surface of HIV(+) and HIV(-) PBMCs and this level was not altered by coculture with rhIL-12 or interferon gamma (IFN-gamma). However, coculture of phytohemagglutinin (PHA)-activated HIV(+) or HIV(-) PBMCs with rhIL-12 (but not IFN-gamma) increased IL-12R beta 2 expression on the cell surface of both populations. Examination at the message level showed a correction of IL-12R beta 1 to normal levels with activation that was further enhanced by rhIL-12 coculture for both the HIV(+) and HIV(-) PBMCs. However, although the level of IL-12R beta 2 for the HIV(+) PBMCs was normalized by PHA, rhIL-12 caused a further augmentation. This information provides a strong link between IL-12R upregulation, and the significant improvement in antigen-specific HIV-proliferative responses seen with the addition of rhIL-12. It also reveals that the dysfunction in IL-12R expression seen in cells from HIV(+) patients occurs at the transcriptional level. In addition, we provide further evidence that IL-12R beta 1 and IL-12R beta 2 regulation in human PBMCs is independent of IFN-gamma.

Depression and HIV infection: impact on immune function and disease progression

Can psychological factors, such as depression, affect human immunodeficiency virus progression? HIV infection is viewed as a chronic illness in which those infected often confront a number of emotional challenges and physical health and disease-related issues. Over the past 20 years, there has been increasing evidence that depression and other mood-related disturbances are commonly observed among HIV-positive individuals. There is also mounting data showing that depressive symptoms might further impact upon specific elements of immune system functioning and influence quality of life and health status. This paper will highlight studies examining the prevalence of depression during HIV infection and review some of the evidence examining the impact of depressive symptoms on immune function and HIV disease progression.

Enhanced interleukin-12 and CD40 ligand activities but reduced Staphylococcus aureus Cowan 1-induced responses suggest a generalized and progressively impaired type 1 cytokine pattern for human schistosomiasis

Whole-blood-cell cultures from schistosomiasis patients were stimulated with a variety of T-cell-dependent and T-cell-independent stimuli to determine whether the defect in type 1 cytokine expression observed following helminth infection is associated with alterations in interleukin-12 (IL-12) or CD40 ligand (CD40L) responsiveness. Cultures from uninfected individuals produced abundant gamma interferon in response to Staphylococcus aureus Cowan 1 (SAC), while patients with intestinal and hepatosplenic disease displayed intermediate and weak responses, respectively. Importantly, the decrease in type 1 cytokine expression was not attributed to defects in IL-12- or CD40L-induced activity. Indeed, schistosomiasis patients displayed heightened responses and even produced more biologically active IL-12 when stimulated with SAC and CD40L than did uninfected controls. Finally, additional studies suggested only a partial role for IL-10, since intestinal patients were the only group that overproduced this downregulatory cytokine. Together, these studies demonstrate that the type 1 deficiency in chronic hepatosplenic schistosomiasis is not related to specific defects in IL-12, IL-10, or CD40L activity, although changes in the functional status of antigen-presenting cells appear to be involved.

Enhancement of natural killer cell activation and antibody-dependent cellular cytotoxicity by interferon-alpha and interleukin-12 in vaginal mucosae Sivmac251-infected Macaca fascicularis

We studied the innate immune system of Cynomolgus monkeys (Macaca fascicularis) experimentally infected via the vaginal mucosae with a virulent simian immunodeficiency virus isolate SIVmac251. Animals were evaluated for their natural killer (NK) cell activity, and for their antibody-dependent cellular cytotoxicity. NK cells from SIVmac251-infected macaques show impaired NK cell activity compared to cells from uninfected animals. Subsequent treatment of NK cells with interferon-a (IFN-alpha) or interleukin-12 (IL-12) alone partially restored the NK activity. However, either treatment of NK cells with both IFN-alpha and IL-12 completely reversed the impairment of cytotoxicity induced by simian immunodeficiency virus (SIV) infection. Incubation of NK cells from infected but not from uninfected monkeys with IFN-alpha and IL-12 for 8 days increased the percentage of CD16+/CD56+ cells twofold to five-fold and enhanced antibody-dependent cellular cytotoxicity (ADCC) activity. Thus IFN-alpha and IL-12 greatly enhance both the NK cell and ADCC activities of peripheral blood cells from SIVmac251-infected animals and increase the number of NK cells in longer term culture. The combined effect of IFN-alpha and IL-12 in enhancing NK cell activity may provide a novel therapeutic approach for the restoration of depressed NK cell activity observed in human immunodeficiency virus (HIV)-infected patients.

Flow cytometry--a rapid tool to correlate functional activities of human peripheral blood lymphocytes with their corresponding phenotypes after in vitro stimulation

BACKGROUND

While dealing with mixed in vitro lymphocyte cultures one is faced with the problem of relative contributions of different populations to the activity being studied. This is especially true in the controversy relating to the contributions of lymphocyte sub-populations to the Lymphokine Activated Killer (LAK) phenomenon. Flowcytometry can be used to highlight relative contributions of lymphocyte subpopulations towards LAK activity without resorting to difficult purification strategies. We set up long-term in vitro lymphocyte cultures, stimulated them with cytokines IL-2/IL-12, recorded their phenotypic changes and cytotoxic activity against U-937 tumor targets.

RESULTS

The results indicated that natural killer cells (NK) constituted the predominant proliferating cell population in the cytokine stimulatedcultures. Flowcytometric evidence revealed that CD56+ T cells contributed little to LAK activity against U937 target cells as compared to cells with NK phenotype which were predominantly responsible for spontaneous killing of the tumor targets. The two cytokines, IL-2 and IL-12, had an additive effect on cell proliferation and spontaneous cytotoxicity.

CONCLUSION

Flowcytometry can be used to rapidly delineate phenotypic changes in immune cells after stimulation and simultaneously correlate them with corresponding functional activity. This approach may find application as a initial screening tool for studying different types of cells in mixed cultures and their respective activities under stimulatory / inhibitory conditions.

Developmental and functional defects of thymic and epidermal V gamma 3 cells in IL-15-deficient and IFN regulatory factor-1-deficient mice

In this study, the role of IL-15 and its regulation by the transcription factor IFN regulatory factor-1 (IRF-1) in murine V gamma 3 T cell development and activity is assessed. Compared with wild-type (WT) mice, reduced numbers of mature V gamma 3 cells were found in the fetal thymus of IL-15(-/-) mice, while IRF-1(-/-) mice displayed normal frequencies. V gamma 3(+) dendritic epidermal T cells (DETCs) were absent in IL-15(-/-) mice but present in IRF-1(-/-) mice. DETCs from IRF-1(-/-) mice displayed morphologically a less mature phenotype and showed different emergence kinetics during ontogeny. This corresponded with lower IL-15 mRNA levels in the skin epidermis. Comparable levels of IL-7 were found in the skin of WT and IL-15(-/-) mice. Adoptive transfer experiments of WT fetal thymocytes into IL-15(-/-) mice did not result in the development of V gamma 3(+) DETCs, confirming the nonredundant role of IL-15 in the skin during DETC development. In vitro, cytolytic activity of IL-15(-/-) V gamma 3 cells was normal after stimulation with IL-15 and was further enhanced by addition of IL-12. In contrast, cytolytic activity of IRF-1(-/-) V gamma 3 cells remained defective after stimulation with IL-15 in combination with IL-12. These data suggest that IL-15 is redundant for the development and/or survival of mature V gamma 3 cells in the fetal thymus, whereas it is essential for the localization of V gamma 3 cells in the skin. Furthermore, a possible role for IRF-1 in inducing morphological maturation of DETCs and cytolytic capacity of V gamma 3 cells is suggested.

Sustained impairment of IFN-gamma secretion in suppressed HIV-infected patients despite mature NK cell recovery: evidence for a defective reconstitution of innate immunity

The impairment of NK cell functions in the course of HIV infection contributes to a decreased resistance against HIV and other pathogens. We analyzed the proportion of mature and immature NK cell subsets, and measured subsets of IFN-gamma and TNF-alpha-producing NK and T cells in viremic or therapy-suppressed HIV-infected subjects, and noninfected control donors. Viremic HIV(+) individuals had significantly lower proportions of mature CD3(-)/CD161(+)/CD56(+) NK cells and of IFN-gamma-producing NK cells compared with noninfected donors, independent of CD4(+) T cell counts. HIV-infected subjects with undetectable viral load recovered mature CD3(-)/CD161(+)/CD56(+) NK cells and cytotoxicity against tumor (K562) and HSV-infected target cells to percentages comparable with those of uninfected individuals, but their NK cells remained impaired in their ability to produce IFN-gamma. In parallel to these ex vivo findings, in vitro NK cell differentiation of CD34-positive cord blood precursors in the presence of R5 or X4 HIV-1 resulted in the production of NK cells with a normal mature phenotype, but lacking the ability to produce IFN-gamma, whereas coculture of uninfected PBMC with HIV failed to affect mature NK cell properties or IFN-gamma secretion. Altogether, our findings support the hypothesis that mature NK cell phenotype may be uncoupled from some mature functions following highly active antiretroviral therapy-mediated suppression of HIV-1, and indicate that relevant innate immune functions of NK cell subsets may remain altered despite effective viral suppression following antiretroviral treatment.

Combined IL-12 and GM-CSF gene therapy for murine hepatocellular carcinoma

Among various immunotherapeutic approaches, interleukin-12 (IL-12) is particularly appealing because of its superior antitumor effects, which have been demonstrated in preclinical as well as clinical studies. However, IL-12 therapy was often accompanied by severe side effects due mainly to the supranormal induction of interferon-gamma. To optimize the therapeutic efficacy and lower the side effects of IL-12, we have investigated the antitumor activity of combined IL-12 and granulocyte-macrophage colony-stimulating factor (GM-CSF) gene therapy in a highly malignant and poorly immunogenic murine hepatocellular carcinoma model. Using a versatile hydrodynamics-based DNA delivery method, we showed that the combined gene delivery of IL-12 and GM-CSF induced very strong antitumor cellular immunity and achieved significant therapeutic efficacy, whereas each cytokine gene alone yielded appreciable but less effects. We also observed that the combined therapy induced lower levels of interferon-gamma than did IL-12 alone. These results suggest that combined IL-12 and GM-CSF therapy can render a stronger antitumor effect as well as lowering potential side effects.

Glycyrrhizin enhances interleukin-12 production in peritoneal macrophages

Interleukin-12 (IL-12) is a monocyte/macrophage-derived cytokine that plays a prominent role in the development of T helper type 1 (Th1) cell-mediated immune responses. Glycyrrhizin (GL), an aqueous extract of liquorice root, used as Chinese medicine, is known to have various immunomodulating activities. In this study, GL showed a dose-dependent priming effect on lipopolysaccharide (LPS)-induced IL-12 p40 and IL-12 p70 (heterodimer of p40 and p35) protein production by peritoneal macrophages (PM). The maximal effect was observed when GL was intraperitoneally administered 12 hr before the PM were harvested and stimulated in vitro with LPS. The increases in IL-12 p70 and p40 protein production were primarily due to up-regulated transcription of IL-12 p35 and p40 messenger RNAs (mRNAs), as demonstrated by RNase protection assay. The augmentation of IL-12 p40 mRNA expression induced by GL pretreatment was associated with increased NF-kappaB activation. Moreover, GL exhibited the same priming effect on IL-12 production in interferon-gamma knockout (IFN-gamma-/-) mice. The production of granulocyte-macrophage colony-stimulating factor (GM-CSF) was not induced at any time point after GL pretreatment. These findings demonstrated the ability of GL to enhance LPS-induced IL-12 production by peritoneal macrophages, and indicated that the priming effect of GL on IL-12 production was independent of both IFN-gamma and GM-CSF.

In vitro HIV-specific CTL activity from HIV-seropositive individuals is augmented by interleukin-12 (IL-12)

IL-12 production is reduced in HIV infection, and recombinant human IL-12 (rhIL-12) augments in vitro HIV-specific proliferative responses in PBMC from HIV-seropositive individuals. To determine whether rhIL12 could also augment HIV-specific CTL responses we studied 41 HIV-seropositive individuals. Recombinant hIL-12 increased the detectable in vitro HIV-specific CD8 CTL activity of PBMC taken from HIV-seropositive individuals with CD4 counts >500 cells/microl and from some individuals with lower CD4 counts. IL-12 increased cell recovery in cultures of PBMC from HIV-seropositive individuals with CD4 counts >500 cells/microl and also increased the precursor CTL frequency. However, the increase in HIV-specific CTL activity was not due to IL-2 or IFN-gamma production or an increase in the number of cells with surface markers characteristic of CTL effector cells. This study demonstrates that rhIL-12 augments in vitro HIV-specific CTL activity and provides evidence to justify further investigation within clinical trials of this cytokine in HIV infection.

Interleukin 12 gene transfer into skin distant from the tumor site elicits antimetastatic effects equivalent to local gene transfer

We have reported that particle-mediated interleukin 12 (IL-12) gene transfer into the skin overlying the local tumor inhibits systemic metastases. To further characterize this effect, we compared the antitumor and antimetastatic effects of IL-12 cDNA delivered at the local tumor site versus at a site distant from the primary tumor, in a spontaneous metastasis model of LLC-F5 tumor. Local IL-12 gene delivery into the skin overlying the intradermal tumor (local IL-12 treatment) on days 7, 9, and 11 after tumor implantation resulted in the most suppression of the growth of the primary LLC-F5 tumor, whereas IL-12 gene transfer into the skin distant from the tumor (distant IL-12 treatment) was less effective. In contrast, both local IL-12 and distant IL-12 treatment, followed by tumor excision, inhibited lung metastases to a similar extent, resulting in significantly extended survival of test mice. The results of in vivo studies using depleting anti-asialo GM1 antibody and anti-CD4/anti-CD8 monoclonal antibodies, or neutralizing anti-interferon gamma (IFN-gamma) monoclonal antibody demonstrated that natural killer (NK) cells, CD8(+) T cells, and IFN-gamma contributed to the antimetastatic effects in both treatment groups. Furthermore, the levels of mRNA expression of vascular endothelial growth factor and matrix methalloproteinase 9 at the tumor microenvironment were suppressed after both local and distant IL-12 treatment. These results suggest that the current particle-mediated IL-12 gene delivery in the spontaneous LLC-F5 metastasis model can confer antimetastatic activities, irrespective of the gene transfection site, via a combination of several mechanisms involving CD8(+) T cells, NK cells, IFN-gamma, and antiangiogenesis.

Interleukin-2 enhances the response of natural killer cells to interleukin-12 through up-regulation of the interleukin-12 receptor and STAT4

Interleukin (IL)-12 plays a critical role in modulating the activities of natural killer (NK) cells and T lymphocytes. In animal models, IL-12 has potent antitumor effects that are likely mediated by its ability to enhance the cytotoxic activity of NK cells and cytotoxic T lymphocytes, and to induce the production of interferon (IFN)-γ by NK and T cells. In addition to IL-12, NK cells are responsive to IL-2, and may mediate some of the antitumor effects of IL-2. In this study, we examine the interaction between IL-2 and the signaling events induced by IL-12 in NK cells. We find that IL-2 not only up-regulates the expression of IL-12Rβ1 and IL-12Rβ2, it also plays an important role in up-regulating and maintaining the expression of STAT4, a critical STAT protein involved in IL-12 signaling in NK cells. In contrast to the effects of IL-2 alone, expression of IL-12 receptors and STAT4 are unaffected or decreased by IL-12 or the combination of IL-2 and IL-12. Through expression of high levels of IL-12 receptors and STAT4, IL-2–primed NK cells show enhanced functional responses to IL-12 as measured by IFN-γ production and the killing of target cells. NK cells from cancer patients who received low-dose IL-2 treatment also exhibited increased expression of IL-12 receptor chains, suggesting that IL-2 may enhance the response to IL-12 in vivo. These findings provide a molecular framework to understand the interaction between IL-2 and IL-12 in NK cells, and suggest strategies for improving the effectiveness of these cytokines in the immunotherapy of cancer.

Interleukin-2 enhances the response of natural killer cells to interleukin-12 through up-regulation of the interleukin-12 receptor and STAT4

Interleukin (IL)-12 plays a critical role in modulating the activities of natural killer (NK) cells and T lymphocytes. In animal models, IL-12 has potent antitumor effects that are likely mediated by its ability to enhance the cytotoxic activity of NK cells and cytotoxic T lymphocytes, and to induce the production of interferon (IFN)-γ by NK and T cells. In addition to IL-12, NK cells are responsive to IL-2, and may mediate some of the antitumor effects of IL-2. In this study, we examine the interaction between IL-2 and the signaling events induced by IL-12 in NK cells. We find that IL-2 not only up-regulates the expression of IL-12Rβ1 and IL-12Rβ2, it also plays an important role in up-regulating and maintaining the expression of STAT4, a critical STAT protein involved in IL-12 signaling in NK cells. In contrast to the effects of IL-2 alone, expression of IL-12 receptors and STAT4 are unaffected or decreased by IL-12 or the combination of IL-2 and IL-12. Through expression of high levels of IL-12 receptors and STAT4, IL-2–primed NK cells show enhanced functional responses to IL-12 as measured by IFN-γ production and the killing of target cells. NK cells from cancer patients who received low-dose IL-2 treatment also exhibited increased expression of IL-12 receptor chains, suggesting that IL-2 may enhance the response to IL-12 in vivo. These findings provide a molecular framework to understand the interaction between IL-2 and IL-12 in NK cells, and suggest strategies for improving the effectiveness of these cytokines in the immunotherapy of cancer.

Monocytes secrete interleukin-6 when co-cultured in vitro with benign or malignant autologous fragment spheroids from squamous cell carcinoma patients

Biopsies from tumour and benign mucosa were removed from patients with head and neck squamous-cell carcinoma (HNSCC), chopped into cubes and transferred to a nonadhesive culture system where in vitro fragment (F)-spheroids were established. The F-spheroids stabilized within 14 days of culture in vitro with epithelial cells and fibroblasts on the surface. F-spheroids were co-cultured with freshly isolated autologous monocytes. The monocytes of 10 of 11 patients secreted interleukin (IL)-6 at a level similar to that of the average monocyte endotoxin-stimulated response. Secreted IL-1beta or tumour necrosis factor-alpha (TNF-alpha) levels greater than 0.1 times the endotoxin-stimulated secretion were determined in one and two of the 11 co-culture experiments, respectively. This different monocyte response to F-spheroids compared with endotoxin stimulation was also present at the mRNA expression level. HNSCC monocytes secreted no IL-6 after co-culture with autologous fibroblasts. When monocytes and F-spheroids were cultured separated by a semipermeable membrane, the IL-6 supernatant level was only approximately 25% of that observed during co-culture with direct contact. F-spheroids secreted only trace amounts of IL-6. In conclusion, monocytes of HNSCC patients generally secrete IL-6, but not IL-1beta or TNF-alpha, after stimulation with epithelial-associated components of F-spheroids upon direct contact and in part by a soluble substance.

An acidic microenvironment inhibits antitumoral non-major histocompatibility complex-restricted cytotoxicity: implications for cancer immunotherapy

Local immunosuppression may explain the failure of an effective immune response against solid tumors. Although it is well known that the interstitial pH is significantly lower in solid tumors than in normal tissue, only a few studies in the mouse system have investigated the influence of this acidic milieu on the anti-tumoral cytotoxic response. Here the authors report the suppression of human non-major histocompatibility complex (MHC)-restricted cytotoxicity against tumor cells by an acidic extracellular pH (pHe). Unstimulated peripheral blood mononuclear cells, lymphokine-activated killer (LAK) cells, and natural killer cell clones were used as effector cells. According to pH measurements in solid tumors, representative pH values of 7.2 to 5.3 were chosen during the cytotoxic assays. Target cell lysis was measured using two nonradioactive fluorometric methods, namely two-color flow cytometry and a modified calcein-release assay, which allowed cell-mediated cytotoxicity to be measured and compared with that in adherent targets. Using K562, Daudi, or Raji as suspended target cell lines, the cytotoxic activity of unstimulated peripheral blood mononuclear cells and of LAK cells was markedly reduced by a decreasing pHe. An extracellular pH of 5.8 to 5.3 resulted in a nearly complete loss of the cytotoxic response. This pHe-dependent impairment of the killing activity could also be shown for killer cells stimulated with interleukins-7 and -12, phytohemagglutinin, or lipopolysaccharide. The lytic potential of homogeneous natural killer cell clones as effectors was also strictly influenced by the surrounding pH. The pHe dependence of the non-MHC-restricted killer cell functions against tumor cells seems to be a general phenomenon, because the cytolytic activity of LAK cells against six human adherent tumor cell lines (HeLa, HepG2, LS174T, LS174Te, MCF-7, and RT112) was also clearly reduced under acidic conditions. To initiate the killing process, adhesion molecules play an important role in recognition and binding of the target cell. However, flow cytometric analysis revealed that the expression pattern of relevant adhesion molecules was unaffected by acidic pHe. In conclusion, these data clearly indicate an inhibition of non-MHC-restricted cytotoxicity against tumor cells by an acidic pHe, which may contribute to the failure of immunosurveillance against solid tumors. Consequently, efforts to enhance the anti-tumoral cytotoxicity by immunotherapies may have limited success.

Involvement of granzyme B expression in the enhancement of natural killer activity by beta-endorphin

Beta-Endorphin has been reported to enhance natural killer (NK) activity in vitro. However, few studies have examined the precise regulation of the cytolytic stage of NK cells. We therefore investigated the regulation by beta-endorphin of cytotoxicity-associated molecules such as granzyme B, perforin, and Fas ligand (FasL) in human CD16(+) NK cells. On semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) assay, the granzyme B mRNA level apparently increased in CD16(+) NK cells from high responding subjects having ratios >1.5 for the LU(30) ratio. An increase in intracellular granzyme B molecules was also detected in CD16(+) NK cells by flow cytometry. On the other hand, perforin and FasL appeared not to be involved in regulation by beta-endorphin. These findings suggest that up-regulation of granzyme B expression may be involved in the enhancement of NK activity by beta-endorphin.