Secretion of interferon-gamma by human macrophages demonstrated at the single-cell level after costimulation with interleukin (IL)-12 plus IL-18

Molecular cloning and characterisation of in vitro immune response against astacin-like metalloprotease Ace-MTP-2 from Ancylostoma ceylanicum

Ancylostoma ceylanicum belongs to the group of parasites commonly known as hookworms, blood-sucking nematodes which infect around 576 million people and hundreds of millions of animals. The interactions between these parasites and host immune systems are complicated and yet to be determined. Hookworm infections are usually long lasting and recurrent, due in part to their ability to synthesize macromolecules capable of modulating the host immune response. The interaction of parasite proteins with host immune systems has been proven, but so far there is no data describing the influence of astacin-like metalloproteases (expressed among different parasitic nematodes) on the human immune system. The cDNA encoding A. ceylanicum metalloprotease 2 (Ace-mtp-2) was cloned using RACE-PCR. Computational analysis was used to examine the immunogenicity and recombinant Ace-MTP-2 was used to investigate its influence on human THP-1 monocytes and macrophages. The Ace-mtp-2 gene encodes an astascin-like metalloprotease, with a theoretical molecular mass of 26.7 kDa. The protease has a putative signal peptide, 11 potential phosphorylation sites, and two disulfide bridges revealed by computational analysis. Maximal expression of Ace-mtp-2 by A. ceylanicum occurs in the adult stage of the parasite, and Western blot indicates the secretory nature of the protease. This suggests the protease is working at the host-parasite interface and would likely be exposed to the hosts immune response. Recombinant protein were expressed in Escherichia coli and Pichia pastoris. Recombinant Ace-MTP-2 amplified the in vitro release of TNFα and induced release of IFNγ by lipopolysaccharide activated THP-1 macrophages. The presence of Ace-MTP-2 in secretory products of the adult parasite and the induction of IFNγ release may suggest an important role for Ace-MTP-2 in host-parasite interactions since IFNγ is suggested to be responsible for the protective immune response against adult hookworms.

Targeting macrophages in the tumour environment to enhance the efficacy of αOX40 therapy

The treatment of high-grade tumours must consider a tumour environment dominated by cells that support cancer growth. In addition to directing angiogenesis and invasion, alternatively activated macrophages in the tumour provide protection from adaptive immunity and permit tumour growth. Agonist antibodies to the tumour necrosis factor receptor family member OX40 are an effective therapy for cancer in a range of murine models; however, as with many immune therapies, αOX40 therapy is less effective as the tumour grows and develops an immune suppressive environment. We demonstrate that αOX40 directly activates T cells and that this T-cell activation alters macrophage differentiation in the tumour environment. We demonstrate that macrophages in the tumour limit the efficacy of αOX40 therapy, and that combining αOX40 therapy with inhibitors of arginase significantly enhances survival of tumour-bearing mice. These data demonstrate that macrophages in the tumour environment limit the effectiveness of OX40-based immunotherapy, and combination therapies that target both the cell-mediated immune response and the suppressive tumour environment will be required for translation of effective immunotherapies to patients with established tumours.

A protective role for interleukin 18 in interferon γ-mediated innate immunity to Cryptosporidium parvum that is independent of natural killer cells

Innate immunity against some intracellular parasitic protozoa involves interleukin 18 (IL-18)-mediated interferon γ (IFN-γ) production by natural killer (NK) cells, but the role of IL-18 in innate resistance to Cryptosporidium infection is unknown. Adult Rag2(-/-)γc(-/-) mice that lack NK cells, T cells, and B cells demonstrated resistance to Cryptosporidium parvum infection that was IFN-γ dependent. Treatment with anti-IL-18-neutralizing antibodies resulted in loss of resistance correlating with reduced intestinal IFN-γ expression. Intestinal mature IL-18 expression increased in vivo during infection and also in the intestinal epithelial cell line CMT-93 following combined IFN-γ treatment/infection. Peritoneal macrophages produced IFN-γ when stimulated with IL-18 combined with interleukin 12, and the latter was expressed in vivo during infection. Macrophage depletion in infected mice caused a rapid growth of infection with no increase in IFN-γ expression. These findings provide evidence of an NK cell-independent, IFN-γ-mediated innate immune pathway against C. parvum in which IL-18 and macrophages play prominent parts.

Cytokines profiling by multiplex analysis in experimental arthritis: which pathophysiological relevance for articular versus systemic mediators?

INTRODUCTION

We have taken advantage of the large screening capacity of a multiplex immunoassay to better define the respective contribution of articular versus systemic cytokines in experimental arthritis.

METHODS

We performed a follow up (from 7 hours to 14 days) multiplex analysis of 24 cytokines in synovial fluid and sera of rats developing Antigen-Induced Arthritis (AIA) and confronted their protein level changes with molecular, biochemical, histological and clinical events occurring in the course of the disease.

RESULTS

The time-scheduled findings in arthritic joints correlated with time-dependent changes of cytokine amounts in joint effusions but not with their blood levels. From seven hours after sensitization, high levels of chemokines (MCP-1, MIP1α, GRO/KC, RANTES, eotaxin) were found in synovial fluid of arthritic knees whereas perivascular infiltration occurred in the synovium; local release of inflammatory cytokines (IFNγ, IL-1β, IL-6) preceded the spreading of inflammation and resulted in progressive degradation of cartilage and bone. Finally a local overexpression of several cytokines/adipocytokines poorly described in arthritis (IL-13, IL-18, leptin) was observed.

CONCLUSIONS

Distinct panels of cytokines were found in arthritic fluid during AIA, and the expected effect of mediators correlated well with changes occurring in joint tissues. Moreover, multiplex analysis could be helpful to identify new pathogenic mediators and to elucidate the mechanisms supporting the efficacy of putative targeted therapies.

In vitro differentiation of human macrophages with enhanced antimycobacterial activity

Mycobacterium tuberculosis causes widespread, persistent infection, often residing in macrophages that neither sterilize the bacilli nor allow them to cause disease. How macrophages restrict growth of pathogens is one of many aspects of human phagocyte biology whose study relies largely on macrophages differentiated from monocytes in vitro. However, such cells fail to recapitulate the phenotype of tissue macrophages in key respects, including that they support early, extensive replication of M. tuberculosis and die in several days. Here we found that human macrophages could survive infection, kill Mycobacterium bovis BCG, and severely limit the replication of M. tuberculosis for several weeks if differentiated in 40% human plasma under 5%-10% (physiologic) oxygen in the presence of GM-CSF and/or TNF-α followed by IFN-γ. Control was lost with fetal bovine serum, 20% oxygen, M-CSF, higher concentrations of cytokines, or premature exposure to IFN-γ. We believe that the new culture method will enable inquiries into the antimicrobial mechanisms of human macrophages.

Macrophage Colony Stimulating Factor-Induced Macrophage Differentiation Influences Myotube Elongation

Background:

Unaccustomed exercise, high-intensity dynamic sports activities, or the resumption of normal weight-bearing after a period of disuse can induce skeletal muscle injury, which activates an inflammatory response followed by muscle regeneration. Specific subsets of macrophages are involved in muscle regeneration. But the exact role of macrophage differentiation during muscle regeneration remains to be elucidated.

Objective:

The objective of the study was to examine the effect of macrophage colony stimulating factor (M-CSF)-differentiated, lipopolysaccharides (LPS)-stimulated-macrophage-conditioned medium on muscle-cell proliferation, fusion, and elongation, which are key events during muscle regeneration and myogenesis.

Method:

Murine C2C12 myoblasts were cultured in conditioned medium obtained from PU5-1R macrophages that were (a) undifferentiated, unstimulated; (b) M-CSF-differentiated, unstimulated; (c) undifferentiated, LPS-stimulated; or (d) M-CSF-differentiated, LPS-stimulated. Myoblast proliferation ratio, nuclei number, and length were measured.

Results:

C2C12 cells cultured in conditioned medium from M-CSF-differentiated, LPS-stimulated macrophages had significantly more nuclei and greater length than cells cultured in conditioned medium from undifferentiated, LPS-stimulated macrophages. Dilution and denaturization of the M-CSF-differentiated, LPS-stimulated-macrophage medium prevented a marked increase in C2C12 nuclei number and length. However, the C2C12 myoblast proliferation ratio was significantly greater in conditioned medium from undifferentiated, LPS-stimulated macrophages than in conditioned medium from M-CSF-differentiated, LPS-stimulated macrophages.

Conclusions:

M-CSF-differentiated, LPS-stimulated macrophages may influence myogenesis and the early and terminal stages of muscle regeneration. This knowledge may aid in developing therapies that will directly expedite muscle repair and lead to faster rehabilitation and reduced rehabilitation costs.

Oncolytic adenovirus co-expressing IL-12 and IL-18 improves tumor-specific immunity via differentiation of T cells expressing IL-12Rβ2 or IL-18Rα

The oncolytic adenovirus (Ad) is currently being advanced as a promising antitumor remedy as it selectively replicates in tumor cells and can transfer and amplify therapeutic genes. Interleukin (IL)-12 induces a potent antitumor effect by promoting natural killer (NK) cell and cytotoxic T cell activities. IL-18 also augments cytotoxicity of NK cells and proliferation of T cells. This effect further enhances the function of IL-12 in a synergistic manner. Therefore, we investigated for the first time an effective cancer immunogene therapy of syngeneic tumors via intratumoral administration of oncolytic Ad co-expressing IL-12 and IL-18, RdB/IL-12/IL-18. Intratumoral administration of RdB/IL-12/IL-18 improved antitumor effects, as well as increased survival, in B16-F10 murine melanoma model. The ratio of T-helper type 1/2 cytokine as well as the levels of IL-12, IL-18, interferon-γ and granulocyte–macrophage colony-stimulating factor was markedly elevated in RdB/IL-12/IL-18-treated tumors. Mice injected with RdB/IL-12/IL-18 also showed enhanced cytotoxicity of tumor-specific immune cells. Consistent with these results, immense necrosis and infiltration of NK cells, as well as CD4⁺ and CD8⁺ T cells, were observed in RdB/IL-12/IL-18-treated tumor tissues. Importantly, tumors treated with RdB/IL-12/IL-18 showed an elevated number of T cells expressing IL-12Rβ2 or IL-18Rα. These results provide a new insight into therapeutic mechanisms of IL-12 plus IL-18 and provide a potential clinical cancer immunotherapeutic agent for improved antitumor immunity.

Interferon-γ links ultraviolet radiation to melanomagenesis in mice

Cutaneous malignant melanoma is a highly aggressive and frequently chemoresistant cancer, whose incidence continues to rise. Epidemiological studies reveal that the major etiological melanoma risk factor is ultraviolet (UV) solar radiation, with the highest risk associated with intermittent burning doses, especially during childhood1,2. We have experimentally validated these epidemiological findings using the hepatocyte growth factor/scatter factor (HGF/SF) transgenic mouse model, which develops lesions in stages highly reminiscent of human melanoma with respect to biological, genetic and etiologic criteria, but only when irradiated as neonatal pups with UVB, not UVA3,4. However, mechanisms underlying UVB-initiated, neonatal-specific melanomagenesis remain largely unknown. Here we introduce a mouse model permitting fluorescence-aided melanocyte imaging and isolation following in vivo UV irradiation. We use expression profiling to show that activated neonatal skin melanocytes isolated following a melanomagenic UVB dose bear a distinct, persistent interferon response signature, including genes associated with immunoevasion. UVB-induced melanocyte activation, characterized by aberrant growth and migration, was abolished by antibody-mediated systemic blockade of interferon-γ (IFN-γ), but not type-I interferons. IFN-γ was produced by macrophages recruited to neonatal skin by UVB-induced ligands to the chemokine receptor Ccr2. Admixed recruited skin macrophages enhanced transplanted melanoma growth by inhibiting apoptosis; notably, IFN-γ blockade abolished macrophage-enhanced melanoma growth and survival. IFN-γ-producing macrophages were also identified in 70% of human melanomas examined. Our data reveal an unanticipated role for IFN-γ in promoting melanocytic cell survival/immunoevasion, and suggest that IFN-γ-R signaling represents a novel therapeutic melanoma target.

Mouse bone marrow-derived mesenchymal stromal cells turn activated macrophages into a regulatory-like profile

In recent years it has become clear that the therapeutic properties of bone marrow-derived mesenchymal stromal cells (MSC) are related not only to their ability to differentiate into different lineages but also to their capacity to suppress the immune response. We here studied the influence of MSC on macrophage function. Using mouse thioglycolate-elicited peritoneal macrophages (M) stimulated with LPS, we found that MSC markedly suppressed the production of the inflammatory cytokines TNF-α, IL-6, IL-12p70 and interferon-γ while increased the production of IL-10 and IL-12p40. Similar results were observed using supernatants from MSC suggesting that factor(s) constitutively released by MSC are involved. Supporting a role for PGE₂ we observed that acetylsalicylic acid impaired the ability of MSC to inhibit the production of inflammatory cytokines and to stimulate the production of IL-10 by LPS-stimulated M. Moreover, we found that MSC constitutively produce PGE2 at levels able to inhibit the production of TNF-α and IL-6 by activated M. MSC also inhibited the up-regulation of CD86 and MHC class II in LPS-stimulated M impairing their ability to activate antigen-specific T CD4+ cells. On the other hand, they stimulated the uptake of apoptotic thymocytes by M. Of note, MSC turned M into cells highly susceptible to infection with the parasite Trypanosoma cruzi increasing more than 5-fold the rate of M infection. Using a model of inflammation triggered by s.c. implantation of glass cylinders, we found that MSC stimulated the recruitment of macrophages which showed a low expression of CD86 and the MHC class II molecule Ia^b and a high ability to produce IL-10 and IL-12p40, but not IL-12 p70. In summary, our results suggest that MSC switch M into a regulatory profile characterized by a low ability to produce inflammatory cytokines, a high ability to phagocyte apoptotic cells, and a marked increase in their susceptibility to infection by intracellular pathogens.

Cytokines involved in interferon-gamma production by human macrophages

Interferon (IFN)-gamma is important to the immune defense against intracellular pathogens and specifically the ability of macrophages to control Mycobacterium tuberculosis (MTB). Increasing evidence has accumulated to support the idea that macrophages produce IFN-gamma. We describe here the cytokine interactions that determine IFN-gamma expression and secretion during MTB infection of human macrophages. Detection of biologically important IFN-gamma levels in culture supernatants of MTB-infected human macrophages requires the addition of interleukin (IL)-12. IL-18 augmented IFN-gamma production from human macrophages in response to the combination of MTB and supplemental IL-12. Although IL-18 gene expression was generally unchanged, IL-18 protein secretion was enhanced by the combination of MTB and IL-12, and functioned primarily to stimulate IFN-gamma release. Importantly, IL-27 induced by MTB infection opposed IFN-gamma production by antagonizing IL-18 activity in human macrophages. Neutralization of IL-27 increased the expression of the IL-18 receptor beta-chain. Additionally, IL-27 blocked NF-kappaB activation in response to IL-18. These results define the signals required for IFN-gamma production by human macrophages and highlight the interactions between cytokines produced during MTB infection. Together, they identify a novel role for IL-27 in regulating macrophage function by disrupting IL-18 activity.

Depot-specific differences in inflammatory mediators and a role for NK cells and IFN-gamma in inflammation in human adipose tissue

BACKGROUND

Adipose tissue is a primary in vivo site of inflammation in obesity. Excess visceral adipose tissue (VAT), when compared to subcutaneous adipose tissue (SAT), imparts an increased risk of obesity-related comorbidities and mortality, and exhibits differences in inflammation. Defining depot-specific differences in inflammatory function may reveal underlying mechanisms of adipose-tissue-based inflammation.

METHODS

Stromovascular cell fractions (SVFs) from VAT and SAT from obese humans undergoing bariatric surgery were studied in an in vitro culture system with transcriptional profiling, flow cytometric phenotyping, enzyme-linked immunosorbent assay and intracellular cytokine staining.

RESULTS

Transcriptional profiling of SVF revealed differences in inflammatory transcript levels in VAT relative to SAT, including elevated interferon-gamma (IFN-gamma) transcript levels. VAT demonstrated a broad leukocytosis relative to SAT that included macrophages, T cells and natural killer (NK) cells. IFN-gamma induced a proinflammatory cytokine expression pattern in SVF and adipose tissue macrophages (ATM). NK cells, which constitutively expressed IFN-gamma, were present at higher frequency in VAT relative to SAT. Both T and NK cells from SVF expressed IFN-gamma on activation, which was associated with tumor necrosis factor-alpha expression in macrophages.

CONCLUSION

These data suggest involvement of NK cells and IFN-gamma in regulating ATM phenotype and function in human obesity and a potential mechanism for the adverse physiologic effects of VAT.

Toxoplasma gondii cyclophilin 18-mediated production of nitric oxide induces Bradyzoite conversion in a CCR5-dependent manner

Toxoplasma gondii modulates pro- and anti-inflammatory responses to regulate parasite multiplication and host survival. Pressure from the immune response causes the conversion of tachyzoites into slowly dividing bradyzoites. The regulatory mechanisms involved in this switch are poorly understood. The aim of this study was to investigate the immunomodulatory role of T. gondii cyclophilin 18 (TgCyp18) in macrophages and the consequences of the cellular responses on the conversion machinery. Recombinant TgCyp18 induced the production of nitric oxide (NO), interleukin-12 (IL-12), and tumor necrosis factor alpha through its binding with cysteine-cysteine chemokine receptor 5 (CCR5) and the production of gamma interferon and IL-6 in a CCR5-independent manner. Interestingly, the treatment of macrophages with TgCyp18 resulted in the inhibition of parasite growth and an enhancement of the conversion into bradyzoites via NO in a CCR5-dependent manner. In conclusion, T. gondii possesses sophisticated mechanisms to manipulate host cell responses in a TgCyp18-mediated process.