Type I interferon as a powerful adjuvant for monocyte-derived dendritic cell development and activity in vitro and in Hu-PBL-SCID mice

Mediation of nonerosive arthritis in a mouse model of lupus by interferon-alpha-stimulated monocyte differentiation that is nonpermissive of osteoclastogenesis

OBJECTIVE

In contrast to rheumatoid arthritis (RA), the joint inflammation referred to as Jaccoud's arthritis that occurs in systemic lupus erythematosus (SLE) is nonerosive. Although the mechanism responsible is unknown, the antiosteoclastogenic cytokine interferon-alpha (IFNalpha), whose transcriptome is present in SLE monocytes, may be responsible. This study was undertaken to examine the effects of IFNalpha and lupus on osteoclasts and erosion in the (NZB x NZW)F(1) mouse model of SLE with K/BxN serum-induced arthritis.

METHODS

Systemic IFNalpha levels in (NZB x NZW)F(1) mice were elevated by administration of AdIFNalpha. SLE disease was marked by anti-double-stranded DNA (anti-dsDNA) antibody titer and proteinuria, and Ifi202 and Mx1 expression represented the IFNalpha transcriptome. Microfocal computed tomography was used to evaluate bone erosions. Flow cytometry for CD11b and CD11c was used to evaluate the frequency of circulating osteoclast precursors (OCPs) and myeloid dendritic cells (DCs) in blood.

RESULTS

Administration of AdIFNalpha to (NZB x NZW)F(1) mice induced osteopetrosis. (NZB x NZW)F(1) mice without autoimmune disease were fully susceptible to focal erosions in the setting of serum-induced arthritis. However, (NZB x NZW)F(1) mice with high anti-dsDNA antibody titers and the IFNalpha transcriptome were protected against bone erosions. AdIFNalpha pretreatment of NZW mice before K/BxN serum administration also resulted in protection against bone erosion (r(2) = 0.4720, P < 0.01), which was associated with a decrease in the frequency of circulating CD11b+CD11c- OCPs and a concomitant increase in the percentage of CD11b+CD11c+ cells (r(2) = 0.6330, P < 0.05), which are phenotypic of myeloid DCs.

CONCLUSION

These findings suggest that IFNalpha in SLE shifts monocyte development toward myeloid DCs at the expense of osteoclastogenesis, thereby resulting in decreased bone erosion.

Rift Valley fever virus immunity provided by a paramyxovirus vaccine vector

Rift Valley fever virus (RVFV) causes recurrent large outbreaks among humans and livestock. Although the virus is currently confined to the African continent and the Arabian Peninsula, there is a growing concern for RVFV incursions into countries with immunologically naïve populations. The RVFV structural glycoproteins Gn and Gc are preferred targets in the development of subunit vaccines that can be used to control future outbreaks. We here report the production of Gn and Gc by a recombinant vaccine strain of the avian paramyxovirus Newcastle disease virus (NDV) and demonstrate that intramuscular vaccination with this experimental NDV-based vector vaccine provides complete protection in mice. We also demonstrate that a single intramuscular vaccination of lambs, the main target species of RVFV, is sufficient to elicit a neutralizing antibody response.

Gene expression profiling in autoantibody-positive patients with arthralgia predicts development of arthritis

OBJECTIVE

To identify molecular features associated with the development of rheumatoid arthritis (RA), to understand the pathophysiology of preclinical development of RA, and to assign predictive biomarkers.

METHODS

The study group comprised 109 anti-citrullinated protein antibody (ACPA)- and/or rheumatoid factor-positive patients with arthralgia who did not have arthritis but were at risk of RA, and 25 patients with RA. The gene expression profiles of blood samples obtained from these patients were determined by DNA microarray analysis and quantitative polymerase chain reaction.

RESULTS

In 20 of the 109 patients with arthralgia who were at risk of RA, arthritis developed after a median of 7 months. Gene expression profiling of blood cells revealed heterogeneity among the at-risk patients, based on differential expression of immune-related genes. This report is the first to describe gene signatures relevant to the development of arthritis. Signatures significantly associated with arthritis development were involved in interferon (IFN)-mediated immunity, hematopoiesis, and chemokine/cytokine activity. Logistic regression analysis revealed that the odds ratio (OR) for developing arthritis within 12 months was 21.0 (95% confidence interval [95% CI] 2.8-156.1 [P = 0.003]) for the subgroup characterized by increased expression of genes involved in IFN-mediated immunity and/or cytokine/chemokine-activity. Genes involved in B cell immunology were associated with protection against progression to arthritis (OR 0.38, 95% CI 0.21-0.70 [P = 0.002]). These processes were reminiscent of those in patients with RA, implying that the preclinical phase of disease is associated with features of established disease.

CONCLUSION

The results of this study indicate that IFN-mediated immunity, hematopoiesis, and cell trafficking specify processes relevant to the progression of arthritis independent of ACPA positivity. These findings strongly suggest that certain gene signatures have value for predicting the progression to arthritis, which will pave the way to preventive medicine.

Impairment of in vitro generation of monocyte-derived human dendritic cells by inactivated human immunodeficiency virus-1: Involvement of type I interferon produced from plasmacytoid dendritc cells

In an attempt to simplify the protocol of DC generation in vitro, studies conducted herein show that functional DCs could be generated from bulk peripheral blood mononuclear cells (PBMCs) in media containing GM-CSF and IL-4. Interestingly, when PBMCs, but not purified monocytes, were exposed to either CCR5- or CXCR4-tropic inactivated HIV-1 isolates (iHIV-1) at the initiation of the culture, DC yields were significantly reduced in a dose-dependent manner because of monocyte apoptosis. Similar impairment of DC generation was noted using type I IFNs and poly IC not only in cultures of PBMCs but also using highly enriched monocytes. This effect was reversed by antihuman type I IFN receptor, but not by anti-FasL, anti-TRAIL, anti-TNF, or a mixture of these antibodies. iHIV-1-exposed PBMCs, but not monocytes, produced high levels of IFN-alpha but not IFN-beta. PBMCs depleted of CD123(+) plasmacytoid DCs produced low levels of IFN-alpha and were resistant to iHIV-1-mediated DC impairment. Interestingly, exogenously added TNF reversed the impairment by iHIV-1 in the PBMC cultures. In conclusion, the present results indicate that iHIV-1 impairs the in vitro generation of functional DCs from PBMCs through the induction of IFN-alpha from plasmacytoid DCs in a CD4-dependent fashion in the absence of TNF.

Optimal stimulation for CD70 induction on human monocyte-derived dendritic cells and the importance of CD70 in naive CD4(+) T-cell differentiation

Studies in mice have shown that CD70 on dendritic cells (DCs) is sufficient to convert T-cell tolerance into immunity and hence induce anti-tumour immune responses. Therefore, it is important to investigate (i) optimal stimuli to induce CD70 on human monocyte-derived DCs (MoDCs), which are widely used for tumour immunotherapy, and (ii) the role of CD70 in functional differentiation of naive CD4(+) and CD8(+) T cells stimulated with MoDCs. We show that interferon-alpha (IFN-alpha) is a key cytokine to differentiate monocytes into DCs with the capacity to express CD70 upon maturation. CD70 expression on IFN-alpha-induced MoDCs was elicited by different categories of maturation-inducing factors (Toll-like receptor ligands, CD40 ligand and pro-inflammatory mediators), among which prostaglandin E(2) was most effective. Naive T cells stimulated with MoDCs also expressed CD70. Stimulation with MoDCs promoted naive CD4(+) T cells to acquire the ability to produce T helper type 1 and 2 cytokines in a CD70-dependent manner. In contrast, the CD70-CD27 interaction diminished the production of an immunoregulatory cytokine IL-10. The CD27 signal did not play a dominant role in the induction of effector molecules in naive CD8(+) T cells during the stimulation with MoDCs. This study adds a novel function to the versatile cytokines, type I IFNs, that is, the induction of CD70 on MoDCs. CD70 promotes naive CD4(+) T cells to acquire immunostimulatory activity through the DC-T-cell and T-cell-T-cell interactions during the stimulation with MoDCs. Hence, the CD70-CD27 interaction may play an important role in inducing effective immune responses in DC-based immunotherapy.

Intramuscular inoculation of calves with an experimental Newcastle disease virus-based vector vaccine elicits neutralizing antibodies against Rift Valley fever virus

In the past decade, the use of Newcastle disease virus (NDV) as a vaccine vector for the prevention of economically important livestock diseases as well as for human diseases has been extensively explored. In this study, we have constructed a recombinant NDV vaccine virus, named NDFL-Gn, that produces the Rift Valley fever virus (RVFV) Gn glycoprotein. Calves were immunized via either the intranasal route or the intramuscular route. Delivery via the intranasal route elicited no detectable antibody responses, whereas delivery via the intramuscular route elicited antibodies against both NDV and the Gn protein. The RVFV-neutralizing activity of the antisera from intramuscularly vaccinated calves was demonstrated, suggesting that NDV is a promising vaccine vector for the prevention of RVF in calves.

Short-term cultured, interleukin-15 differentiated dendritic cells have potent immunostimulatory properties

Background

Optimization of the current dendritic cell (DC) culture protocol in order to promote the therapeutic efficacy of DC-based immunotherapy is warranted. Alternative differentiation of monocyte-derived DCs using granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-15 has been propagated as an attractive strategy in that regard. The applicability of these so-called IL-15 DCs has not yet been firmly established. We therefore developed a novel pre-clinical approach for the generation of IL-15 DCs with potent immunostimulatory properties.

Methods

Human CD14⁺ monocytes were differentiated with GM-CSF and IL-15 into immature DCs. Monocyte-derived DCs, conventionally differentiated in the presence of GM-CSF and IL-4, served as control. Subsequent maturation of IL-15 DCs was induced using two clinical grade maturation protocols: (i) a classic combination of pro-inflammatory cytokines (tumor necrosis factor-α, IL-1β, IL-6, prostaglandin E₂) and (ii) a Toll-like receptor (TLR)7/8 agonist-based cocktail (R-848, interferon-γ, TNF-α and prostaglandin E₂). In addition, both short-term (2-3 days) and long-term (6-7 days) DC culture protocols were compared. The different DC populations were characterized with respect to their phenotypic profile, migratory properties, cytokine production and T cell stimulation capacity.

Results

The use of a TLR7/8 agonist-based cocktail resulted in a more optimal maturation of IL-15 DCs, as reflected by the higher phenotypic expression of CD83 and costimulatory molecules (CD70, CD80, CD86). The functional superiority of TLR7/8-activated IL-15 DCs over conventionally matured IL-15 DCs was evidenced by their (i) higher migratory potential, (ii) advantageous cytokine secretion profile (interferon-γ, IL-12p70) and (iii) superior capacity to stimulate autologous, antigen-specific T cell responses after passive peptide pulsing. Aside from a less pronounced production of bioactive IL-12p70, short-term versus long-term culture of TLR7/8-activated IL-15 DCs resulted in a migratory profile and T cell stimulation capacity that was in favour of short-term DC culture. In addition, we demonstrate that mRNA electroporation serves as an efficient antigen loading strategy of IL-15 DCs.

Conclusions

Here we show that short-term cultured and TLR7/8-activated IL-15 DCs fulfill all pre-clinical prerequisites of immunostimulatory DCs. The results of the present study might pave the way for the implementation of IL-15 DCs in immunotherapy protocols.

LOX-1 as a natural IFN-alpha-mediated signal for apoptotic cell uptake and antigen presentation in dendritic cells

The identification of molecules responsible for apoptotic cell (AC) uptake by dendritic cells (DCs) and induction of T-cell immunity against AC-associated antigens is a challenge in immunology. DCs differentiated in the presence of interferon-alpha (IFN-alpha-conditioned DCs) exhibit a marked phagocytic activity and a special attitude in inducing CD8(+) T-cell response. In this study, we found marked overexpression of the scavenger receptor oxidized low-density lipoprotein receptor 1 (LOX-1) in IFN-alpha-conditioned DCs, which was associated with increased levels of genes belonging to immune response families and high competence in inducing T-cell immunity against antigens derived from allogeneic apoptotic lymphocytes. In particular, the capture of ACs by IFN-alpha DCs led to a substantial subcellular rearrangement of major histocompatibility complex class I and class II molecules, along with enhanced cross-priming of autologous CD8(+) T cells and CD4(+) T-cell activation. Remarkably, AC uptake, CD8(+) T-cell cross-priming, and, to a lesser extent, priming of CD4(+) T lymphocytes were inhibited by a neutralizing antibody to the scavenger receptor LOX-1 protein. These results unravel a novel LOX-1-dependent pathway by which IFN-alpha can, under both physiologic and pathologic conditions, render DCs fully competent for presenting AC-associated antigens for cross-priming CD8(+) effector T cells, concomitantly with CD4(+) T helper cell activation.

The VP35 protein of Ebola virus impairs dendritic cell maturation induced by virus and lipopolysaccharide

Ebola virus causes rapidly progressive haemorrhagic fever, which is associated with severe immuosuppression. In infected dendritic cells (DCs), Ebola virus replicates efficiently and inhibits DC maturation without inducing cytokine expression, leading to impaired T-cell proliferation. However, the underlying mechanism remains unclear. In this study, we report that Ebola virus VP35 impairs the maturation of mouse DCs. When expressed in mouse immature DCs, Ebola virus VP35 prevents virus-stimulated expression of CD40, CD80, CD86 and major histocompatibility complex class II. Further, it suppresses the induction of cytokines such as interleukin (IL)-6, IL-12, tumour necrosis factor alpha and alpha/beta interferon (IFN-alpha/beta). Notably, Ebola VP35 attenuates the ability of DCs to stimulate the activation of CD4(+) T cells. Addition of type I IFN to mouse DCs only partially reverses the inhibitory effects of VP35. Moreover, VP35 perturbs mouse DC functions induced by lipopolysaccharide, an agonist of Toll-like receptor 4. Deletion of the amino terminus abolishes its activity, whereas a mutation in the RNA binding motif has no effect. Our work highlights a critical role of VP35 in viral interference in DC function with resultant deficiency in T-cell function, which may contribute to the profound virulence of Ebola virus infection.

Temporal analysis of early immune responses in patients with acute hepatitis B virus infection

BACKGROUND & AIMS

Hepatitis B virus (HBV) causes more than 1 million deaths annually from immune-mediated liver damage. The long incubation period has been difficult to study; by the time most patients present, massive viremia and the majority of viral clearance have already occurred. The aim of this study was to investigate the contribution of innate and adaptive immune mechanisms in early acute HBV through access to an unusual cohort of patients sampled in the preclinical phase and followed up to resolution of their infection.

METHODS

Twenty-one patients with acute HBV were studied, 8 of them from before the peak of viremia. Circulating innate cytokines were quantitated by enzyme-linked immunosorbent assay and natural killer (NK) and T-cell effector function by flow cytometry. Results were correlated with temporal changes in viral load, serology, and liver inflammation and compared with healthy controls.

RESULTS

Type I interferon (IFN) remained barely detectable throughout, with concentrations no higher than those found in healthy controls. Similarly, interleukin-15 and IFN-lambda1 were not induced during peak viremia. NK cell activation and capacity for IFN-gamma production were reduced at peak viremia. Early functional HBV-specific CD4 and CD8 T-cell responses were attenuated as viral load increased and recovered again as infection resolved. The transient inhibition of NK and T-cell responses coincided with a surge in the immunosuppressive cytokine interleukin-10 accompanying HBV viremia.

CONCLUSIONS

The early stages of acute HBV are characterized by induction of interleukin-10 rather than type I IFN, accompanied by a temporary attenuation of NK and T-cell responses.

Type I IFN regulate DC turnover in vivo

DC are the most potent antigen-presenting cells that recognise signs of infection and serve as the main activators of naïve T cells. We have previously shown that type I IFN (IFN-I) are produced by DC and can act in an autocrine manner to activate DC. In the present study, we have investigated the role of IFN-I in regulating the turnover and lifespan of DC. We found that DC, especially the CD8alpha(+) subset, from type I IFN receptor knock out (IFNAR KO) mice, display a reduced turnover rate when compared with DC from WT mice, as revealed by BrdU labelling kinetics. In vitro, IFNAR KO BM precursor cells cultured in the presence of GM-CSF generated CD11c(+) DC less efficiently than WT BM, and the IFNAR KO DC that arose displayed reduced migratory ability. Interestingly, splenic DC from IFNAR KO mice exhibited a higher survival rate in short-term culture compared with control DC. Exposure to IFN-I in vivo markedly increased the turnover rate of splenic DC, particularly CD8alpha(+) DC, which was preceded by a transient induction of apoptosis. In accordance with this, IFN-I stimulated the apoptosis of splenic DC in vitro. Overall, our data indicate that IFN-I are important regulators of DC turnover in vivo and suggest that these cytokines may exert this function through the modulation of multiple processes involving DC apoptosis, proliferation and migration.

CD56+ human blood dendritic cells effectively promote TH1-type gammadelta T-cell responses

CD56+ human dendritic cells (DCs) have recently been shown to differentiate from monocytes in response to GM-CSF and type 1 interferon in vitro. We show here that CD56+ cells freshly isolated from human peripheral blood contain a substantial subset of CD14+CD86+HLA-DR+ cells, which have the appearance of intermediate-sized lymphocytes but spontaneously differentiate into enlarged DC-like cells with substantially increased HLA-DR and CD86 expression or into fully mature CD83+ DCs in response to appropriate cytokines. Stimulation of CD56+ cells containing both DCs and abundant gammadelta T cells with zoledronate and interleukin-2 (IL-2) resulted in the rapid expansion of gammadelta T cells as well as in IFN-gamma, TNF-alpha, and IL-1beta but not in IL-4, IL-10, or IL-17 production. IFN-gamma, TNF-alpha, and IL-1beta production were almost completely abolished by depleting CD14+ cells from the CD56+ subset before stimulation. Likewise, depletion of CD14+ cells dramatically impaired gammadelta T-cell expansion. IFN-gamma production could also be blocked by neutralizing the effects of endogenous IL-1beta and TNF-alpha. Conversely, addition of recombinant IL-1beta, TNF-alpha, or both further enhanced IFN-gamma production and strongly up-regulated IL-6 production. Our data indicate that CD56+ DCs from human blood are capable of stimulating CD56+ gammadelta T cells, which may be harnessed for immunotherapy.

CD20-targeted tetrameric interferon-alpha, a novel and potent immunocytokine for the therapy of B-cell lymphomas

Interferon-alpha (IFN-alpha) has direct inhibitory effects on some tumors and is a potent stimulator of both the innate and adaptive immune systems. A tumor-targeting antibody-IFN-alpha conjugate (mAb-IFN-alpha) could kill by direct actions of the monoclonal antibody (mAb) and IFN-alpha on tumor cells and also potentiate a tumor-directed immune response. The modular Dock-and-Lock method (DNL) was used to generate 20-2b, the first immunocytokine having 4 cytokine (IFN-alpha2b) groups that are fused to the humanized anti-CD20 mAb, veltuzumab. Additional mAb-IFN-alpha constructs, each retaining potent IFN-alpha2b biologic activity, also were produced by DNL. The 20-2b shows enhanced antibody-dependent cellular cytotoxicity compared with veltuzumab but lacks complement-dependent cytotoxicity. The 20-2b inhibits in vitro proliferation of lymphoma cells and depletes them from whole human blood more potently than the combination of veltuzumab and a nontargeting, irrelevant, mAb-IFN-alpha. The 20-2b demonstrated superior therapeutic efficacy compared with veltuzumab or nontargeting mAb-IFN-alpha in 3 human lymphoma xenograft models, even though mouse immune cells respond poorly to human IFN-alpha2b. Targeting IFN-alpha with an anti-CD20 mAb makes the immunocytokine more potent than either agent alone. These findings suggest that 20-2b merits clinical evaluation as a new candidate antilymphoma therapeutic.

Self-RNA-antimicrobial peptide complexes activate human dendritic cells through TLR7 and TLR8

Dendritic cell (DC) responses to extracellular self-DNA and self-RNA are prevented by the endosomal seclusion of nucleic acid–recognizing Toll-like receptors (TLRs). In psoriasis, however, plasmacytoid DCs (pDCs) sense self-DNA that is transported to endosomal TLR9 upon forming a complex with the antimicrobial peptide LL37. Whether LL37 also interacts with extracellular self-RNA and how this may contribute to DC activation in psoriasis is not known. Here, we report that LL37 can bind self-RNA released by dying cells, protect it from extracellular degradation, and transport it into endosomal compartments of DCs. In pDC, self-RNA–LL37 complexes activate TLR7 and, like self-DNA–LL37 complexes, trigger the secretion of IFN-α without inducing maturation or the production of IL-6 and TNF-α. In contrast to self-DNA–LL37 complexes, self-RNA–LL37 complexes also trigger the activation of classical myeloid DCs (mDCs). This occurs through TLR8 and leads to the production of TNF-α and IL-6, and the differentiation of mDCs into mature DCs. We also found that self-RNA–LL37 complexes are present in psoriatic skin lesions and are associated with mature mDCs in vivo. Our results demonstrate that the cationic antimicrobial peptide LL37 converts self-RNA into a trigger of TLR7 and TLR8 in human DCs, and provide new insights into the mechanism that drives the auto-inflammatory responses in psoriasis.

Survival and migration of human dendritic cells are regulated by an IFN-alpha-inducible Axl/Gas6 pathway

Axl, a prototypic member of the transmembrane tyrosine kinase receptor family, is known to regulate innate immunity. In this study, we show that Axl expression is induced by IFN-alpha during human dendritic cell (DC) differentiation from monocytes (IFN/DC) and that constitutively Axl-negative, IL-4-differentiated DC (IL-4/DC) can be induced to up-regulate Axl by IFN-alpha. This effect is inhibited by TLR-dependent maturation stimuli such as LPS, poly(I:C), TLR7/8 ligand, and CD40L. LPS-induced Axl down-regulation on the surface of human IFN-alpha-treated DC correlates with an increased proteolytic cleavage of Axl and with elevated levels of its soluble form. GM6001 and TAPI-1, general inhibitors of MMP and ADAM family proteases, restored Axl expression on the DC surface and diminished Axl shedding. Furthermore, stimulation of Axl by its ligand, Gas6, induced chemotaxis of human DC and rescued them from growth factor deprivation-induced apoptosis. Our study provides the first evidence that Gas6/Axl-mediated signaling regulates human DC activities, and identifies Gas6/Axl as a new DC chemotaxis pathway. This encourages one to explore whether dysregulation of this novel pathway in human DC biology is involved in autoimmunity characterized by high levels of IFN-alpha.

Role of Natural Interferon-α Producing Cells (Plasmacytoid Dendritic Cells) in Autoimmunity

The type I interferons (IFNs) have antiviral, cytostatic and prominent immunomodulatory effects, which all are of great importance during viral infections. However, prolonged exposure of the immune system to type I IFN can break tolerance and initiate an autoimmune reaction, eventually leading to autoimmune disease. Recent observations in patients with systemic lupus erythematosus (SLE) have revealed that such individuals have endogenous IFN-alpha inducers, causing an ongoing IFN-alpha production and consequently a continuous stimulation of the immune system. These IFN-alpha inducers consist of small immune complexes (IC) containing DNA or RNA and act on the principal IFN-alpha producing cell, the natural IFN-alpha producing cell (NIPC), also termed the plasmacytoid dendritic cell (PDC). The NIPC/PDC is a key cell in both the innate and adaptive immune response but can also, either directly or via produced IFN-alpha, have a pivotal role in autoimmunity. In this review we summarize recent data concerning NIPC/PDC, including their activation, regulation, function and possible role in autoimmune diseases, especially SLE.

Type I Interferon as a Link Between Innate and Adaptive Immunity through Dendritic Cell Stimulation

Type I interferon (IFN-alpha/beta) is expressed rapidly after infection and plays a key role in innate defense against pathogens. Recent studies have shown that a connection exists between IFN-alpha/beta and antigen-presenting dendritic cells (DCs) at two levels. Firstly, a specific DC precursor, the plasmacytoid pre-DC (p-preDC), was identified as a cell type able to secrete very high amounts of IFN-alpha/beta following stimulation with infectious agents. Secondly, IFN-alpha/beta has been shown to act as a differentiation/maturation factor for DCs. These findings will be discussed in association with evidence indicating that IFN-alpha/beta can enhance and modulate immune responses in vivo. Taken together, the available data suggest that IFN-alpha/beta serves as a link between the innate response to infection and the adaptive immune response.

Inflammatory signals in dendritic cell activation and the induction of adaptive immunity

Pathogen invasion induces a rapid inflammatory response initiated through the recognition of pathogen-derived molecules by pattern recognition receptors (PRRs) expressed on both immune and non-immune cells. The initial wave of pro-inflammatory cytokines and chemokines limits pathogen spread and recruits and activates immune cells to eradicate the invaders. Dendritic cells (DCs) are responsible for initiating a subsequent phase of immunity, dominated by the action of pathogen-specific T and B cells. As for the early pro-inflammatory response, DC activation is triggered by PRR signals. These signals convert resting DCs into potent antigen-presenting cells capable of promoting the expansion and effector differentiation of naive pathogen-specific T cells. However, it has been argued that signals from PRRs are not a prerequisite for DC activation and that pro-inflammatory cytokines have the same effect. Although this may appear like an efficient way to expand the number of DCs that initiate adaptive immunity, evidence is accumulating that DCs activated indirectly by inflammatory cytokines are unable to induce functional T-cell responses. Here, we review the differences between PRR-triggered and cytokine-induced DC activation and speculate on a potential role for DCs activated by inflammatory signals in tolerance induction rather than immunity.

Deconvolution of blood microarray data identifies cellular activation patterns in systemic lupus erythematosus

Systemic Lupus Erythematosus (SLE) is a systemic autoimmune disease with a complex spectrum of cellular and molecular characteristics including several dramatic changes in the populations of peripheral leukocytes. These changes include general leukopenia, activation of B and T cells, and maturation of granulocytes. The manifestation of SLE in peripheral blood is central to the disease but is incompletely understood. A technique for rigorously characterizing changes in mixed populations of cells, microarray expression deconvolution, has been applied to several areas of biology but not to SLE or to blood. Here we demonstrate that microarray expression deconvolution accurately quantifies the constituents of real blood samples and mixtures of immune-derived cell lines. We characterize a broad spectrum of peripheral leukocyte cell types and states in SLE to uncover novel patterns including: specific activation of NK and T helper lymphocytes, relationships of these patterns to each other, and correlations to clinical variables and measures. The expansion and activation of monocytes, NK cells, and T helper cells in SLE at least partly underlie this disease's prominent interferon signature. These and other patterns of leukocyte dynamics uncovered here correlate with disease severity and treatment, suggest potential new treatments, and extend our understanding of lupus pathology as a complex autoimmune disease involving many arms of the immune system.

Intratumoral interferon-alpha gene transfer enhances tumor immunity after allogeneic hematopoietic stem cell transplantation

One of the major challenges in the treatment of solid cancers by allogenic hematopoietic stem cell transfer (alloHSCT) is the specific enhancement of antitumor immunity. Interferon (IFN) is a cytokine with pleiotropic biological functions including an immunomoduration, and our preclinical studies have shown that an intratumoral IFN-alpha gene transfer induced strong local tumor control and systemic tumor-specific immunity. In the present study, we examined whether the IFN-alpha gene transfer could enhance recognition of tumor-associated antigens by donor T cells and augment the antitumor activity of alloHSCT. First, when a mouse IFN-alpha adenovirus vector (Ad-mIFN) was injected into subcutaneous xenografts of syngeneic renal and colon cancer cells, tumor growth was significantly suppressed in a dose-dependent manner. A significant tumor cell death and infiltration of immune cells was recognized in the Ad-mIFN-injected tumors, and the dendritic cells isolated from the tumors showed a strong Th1-oriented response. The antitumor effect of Ad-mIFN was then examined in a murine model of minor histocompatibility antigen-mismatched alloHSCT. The intratumoral IFN-alpha gene transfer caused significant tumor suppression in the alloHSCT recipients, and this suppression was evident not only in the gene-transduced tumors but also in simultaneously inoculated distant tumors which did not receive the vector injection. A cytotoxicity assay showed specific tumor cell lysis by donor T cells responding to IFN-alpha. Graft-versus-host disease was not exacerbated serologically or clinically in the mice treated with IFN-alpha. This combination strategy deserves evaluation in future clinical trials for human solid cancers.

Dendritic cells require a systemic type I interferon response to mature and induce CD4+ Th1 immunity with poly IC as adjuvant

Relative to several other toll-like receptor (TLR) agonists, we found polyinosinic:polycytidylic acid (poly IC) to be the most effective adjuvant for Th1 CD4⁺ T cell responses to a dendritic cell (DC)–targeted HIV gag protein vaccine in mice. To identify mechanisms for adjuvant action in the intact animal and the polyclonal T cell repertoire, we found poly IC to be the most effective inducer of type I interferon (IFN), which was produced by DEC-205⁺ DCs, monocytes, and stromal cells. Antibody blocking or deletion of type I IFN receptor showed that IFN was essential for DC maturation and development of CD4⁺ immunity. The IFN-AR receptor was directly required for DCs to respond to poly IC. STAT 1 was also essential, in keeping with the type I IFN requirement, but not type II IFN or IL-12 p40. Induction of type I IFN was mda5 dependent, but DCs additionally used TLR3. In bone marrow chimeras, radioresistant and, likely, nonhematopoietic cells were the main source of IFN, but mda5 was required in both marrow–derived and radioresistant host cells for adaptive responses. Therefore, the adjuvant action of poly IC requires a widespread innate type I IFN response that directly links antigen presentation by DCs to adaptive immunity.

How the study of children with rheumatic diseases identified interferon-alpha and interleukin-1 as novel therapeutic targets

SUMMARY

Our studies in children with rheumatic diseases have led to the identification of two of the oldest cytokines, type I interferon (IFN) and interleukin 1 (IL-1), as important pathogenic players in systemic lupus erythematosus (SLE) and systemic onset juvenile arthritis (SoJIA), respectively. These findings were obtained by studying the transcriptional profiles of patient blood cells and by assessing the biological and transcriptional effect(s) of active patient sera on healthy blood cells. We also identified a signature that can be used to promptly diagnose SoJIA from other febrile conditions. Finally, our pilot clinical trials using IL-1 blockers have shown remarkable clinical benefits in SoJIA patients refractory to other medications.

Dendritic cell-based cancer immunotherapies

Because of their unique role in linking the innate and adaptive immune systems, dendritic cells (DCs) have been a logical focus for novel immunotherapies. However, strategies employing active immunization with ex vivo generated and antigen-pulsed DCs have shown limited efficacy in clinical trials. These past approaches did not take into account the complex interactions between cells of the innate immune system and DCs during DC maturation, antigen processing, and presentation to naïve T cells. By better understanding the natural sequence of events occurring in vivo during an effective immune response, we can tailor antitumor immunotherapeutic strategies to augment aspects of this response from the activation of innate immune cells to antigen uptake and DC maturation to priming of naïve T cells and, ultimately, to the establishment of antitumor immunity. Current DC vaccination strategies utilize a number of methods to recapitulate the cascade of events that culminate in a protective antitumor immune response.

Addition of interferon-alpha to a standard maturation cocktail induces CD38 up-regulation and increases dendritic cell function

Monocyte-derived dendritic cells (DCs) are used as adjuvant cells in cancer immunotherapy and have shown promising results. In order to obtain full functional capacity, these DCs need to be maturated, and the current "gold standard" for this process is maturation with TNF-alpha, IL-1beta, IL-6 and PGE(2) used for generating standard DCs (sDC). Several studies indicate that IFN-alpha might also be important for DC differentiation and maturation. In this study, we tested the effect of IFN-alpha alone or as addition to the gold standard sDC cocktail. We observed that maturation by IFN-alpha differs from sDC maturation: The major phenotypic change after IFN-alpha maturation was dose-dependent up-regulation of CD38 but not CD83, while sDCs expressed the opposite profile with low CD38 and high CD83 expression. Similarly, maturation by Poly I:C leads to CD38high, CD83low DCs indicating a functional relationship between CD38, IFN-alpha and TLR3. Thus, CD38 appear to be a relevant marker for activation by TLR3 or IFN-alpha. Addition of IFN-alpha to the sDC cocktail results in up-regulation of both CD38 and CD83 and improved capacity for induction of autologous T-cell responses despite few other changes in DC phenotype and cytokine secretion. Our observations suggest that IFN-alpha could be included in maturation protocols for clinical grade DCs used for immunotherapy against cancer and should be included if DCs are used for CD8+ T-cell stimulation in vitro.

Generation in vivo of peptide-specific cytotoxic T cells and presence of regulatory T cells during vaccination with hTERT (class I and II) peptide-pulsed DCs

Background

Optimal techniques for DC generation for immunotherapy in cancer are yet to be established. Study aims were to evaluate: (i) DC activation/maturation milieu (TNF-α +/- IFN-α) and its effects on CD8+ hTERT-specific T cell responses to class I epitopes (p540 or p865), (ii) CD8+ hTERT-specific T cell responses elicited by vaccination with class I alone or both class I and II epitope (p766 and p672)-pulsed DCs, prepared without IFN-α, (iii) association between circulating T regulatory cells (Tregs) and clinical responses.

Methods

Autologous DCs were generated from 10 patients (HLA-0201) with advanced cancer by culturing CD14+ blood monocytes in the presence of GM-CSF and IL-4 supplemented with TNF-α [DCT] or TNF-α and IFN-α [DCTI]. The capacity of the DCs to induce functional CD8+ T cell responses to hTERT HLA-0201 restricted nonapeptides was assessed by MHC tetramer binding and peptide-specific cytotoxicity. Each DC preparation (DCT or DCTI) was pulsed with only one type of hTERT peptide (p540 or p865) and both preparations were injected into separate lymph node draining regions every 2–3 weeks. This vaccination design enabled comparison of efficacy between DCT and DCTI in generating hTERT peptide specific CD8+ T cells and comparison of class I hTERT peptide (p540 or p865)-loaded DCT with or without class II cognate help (p766 and p672) in 6 patients. T regulatory cells were evaluated in 8 patients.

Results

(i) DCTIs and DCTs, pulsed with hTERT peptides, were comparable (p = 0.45, t-test) in inducing peptide-specific CD8+ T cell responses. (ii) Class II cognate help, significantly enhanced (p < 0.05, t-test) peptide-specific CD8+T cell responses, compared with class I pulsed DCs alone. (iii) Clinical responders had significantly lower (p < 0.05, Mann-Whitney U test) T regs, compared with non-responders. 4/16 patients experienced partial but transient clinical responses during vaccination. Vaccination was well tolerated with minimal toxicity.

Conclusion

Addition of IFN-α to ex vivo monocyte-derived DCs, did not significantly enhance peptide-specific T cell responses in vivo, compared with TNF-α alone. Class II cognate help significantly augments peptide-specific T cell responses. Clinically favourable responses were seen in patients with low levels of circulating T regs.

The gamma 1 34.5 protein of herpes simplex virus 1 is required to interfere with dendritic cell maturation during productive infection

The gamma(1)34.5 protein of herpes simplex virus 1 is an essential factor for viral virulence. In infected cells, this viral protein prevents the translation arrest mediated by double-stranded RNA-dependent protein kinase R. Additionally, it associates with and inhibits TANK-binding kinase 1, an essential component of Toll-like receptor-dependent and -independent pathways that activate interferon regulatory factor 3 and cytokine expression. Here, we show that gamma(1)34.5 is required to block the maturation of conventional dendritic cells (DCs) that initiate adaptive immune responses. Unlike wild-type virus, the gamma(1)34.5 null mutant stimulates the expression of CD86, major histocompatibility complex class II (MHC-II), and cytokines such as alpha/beta interferon in immature DCs. Viral replication in DCs inversely correlates with interferon production. These phenotypes are also mirrored in a mouse ocular infection model. Further, DCs infected with the gamma(1)34.5 null mutant effectively activate naive T cells whereas DCs infected with wild-type virus fail to do so. Type I interferon-neutralizing antibodies partially reverse virus-induced upregulation of CD86 and MHC-II, suggesting that gamma(1)34.5 acts through interferon-dependent and -independent mechanisms. These data indicate that gamma(1)34.5 is involved in the impairment of innate immunity by inhibiting both type I interferon production and DC maturation, leading to defective T-cell activation.

Plasmacytoid dendritic cells in the skin: to sense or not to sense nucleic acids

Plasmacytoid dendritic cells (pDCs) are specialized sensors of viral nucleic acids that initiate protective immunity through the production of type I interferons (IFNs). Normally, pDCs fail to sense host-derived self-nucleic acids but do so when self-nucleic acids form complexes with endogenous antimicrobial peptides produced in damaged skin. Whereas regulated expression of antimicrobial peptides may lead to pDC activation and protective immune responses to skin injury, overexpression of antimicrobial peptides in psoriasis drives excessive sensing of self-nucleic acids by pDCs resulting in IFN-driven autoimmunity. In skin tumors, pDCs are unable to sense self-nucleic acids; however, therapeutic activation of pDCs by synthetic nucleic acids or analogues can be exploited to generate antitumor immunity.

Transcriptional re-programming of primary macrophages reveals distinct apoptotic and anti-tumoral functions of IRF-3 and IRF-7

The immunoregulatory transcriptional modulators - IFN-regulatory factor (IRF)-3 and IRF-7 - possess similar structural features but distinct gene-regulatory potentials. For example, adenovirus-mediated transduction of the constitutively active form of IRF-3 triggered cell death in primary human MPhi, whereas expression of active IRF-7 induced a strong anti-tumoral activity in vitro. To further characterize target genes involved in these distinct cellular responses, transcriptional profiles of active IRF-3- or IRF-7-transduced primary human MPhi were compared and used to direct further mechanistic studies. The pro-apoptotic BH3-only protein Noxa was identified as a primary IRF-3 target gene and an essential regulator of IRF-3, dsRNA and vesicular stomatitis virus-induced cell death. The critical role of IRF-7 and type I IFN production in increasing the immunostimulatory capacity of MPhi was also evaluated; IRF-7 increased the expression of a broad range of IFN-stimulated genes including immunomodulatory cytokines and genes involved in antigen processing and presentation. Furthermore, active IRF-7 augmented the cross-presentation capacity and tumoricidal activity of MPhi and led to an anti-tumor response against the B16 melanoma model in vivo. Altogether, these data further highlight the respective functions of IRF-3 and IRF-7 to program apoptotic, immune and anti-tumor responses.

Inhibition of human immunodeficiency virus (HIV-1) infection in human peripheral blood leucocytes-SCID reconstituted mice by rapamycin

The capacity of the immunomodulatory drug rapamycin (RAPA) to inhibit replication of the CCR5 strain of human immunodeficiency virus (HIV) in vitro prompted us to test its effects in a murine preclinical model of HIV infection. RAPA (0.6 or 6 mg/kg body weight) or its vehicle were administered daily, per os, to SCID mice reconstituted with human peripheral blood leucocytes (hu-PBL) starting 2 days before the intraperitoneal challenge with the R5 tropic SF162 strain of HIV-1 (1000 50% tissue culture infective dose/ml). Relative to hu-PBL-SCID mice that received no treatment, HIV-infected hu-PBL-SCID mice treated with the vehicle control for 3 weeks exhibited a severe depletion of CD4(+) cells (90%), an increase in CD8(+) cells and an inversion of the CD4(+)/CD8(+) cell ratio. In contrast, treatment of HIV-infected mice with RAPA prevented a decrease in CD4(+) cells and the increase of CD8(+) cells, thereby preserving the original CD4(+):CD8(+) cell ratio. Viral infection also resulted in the detection of HIV-DNA within peritoneal cells and spleen, and lymph node tissues of the vehicle-treated mice within 3 weeks of the viral challenge. In contrast, treatment with RAPA decreased cellular provirus integration and reduced HIV-RNA levels in the blood. Furthermore, in co-cultivation assays, spleens from RAPA-treated mice exhibited a reduced capacity for infecting allogeneic T cells which was dose-dependent. These data show that RAPA possesses powerful anti-viral activity against R5 strains of HIV in vivo and support the use of additional studies to evaluate the potential application of this drug in the management of HIV patients.

Differential expression of constitutive and inducible proteasome subunits in human monocyte-derived DC differentiated in the presence of IFN-alpha or IL-4

Several studies strongly suggest that DC differentiated in vitro in the presence of type I IFN acquire more potent immune stimulatory properties, compared with DC differentiated in vitro with IL-4. However, little is known about the molecular mechanisms underlying this phenomenon. To address this question, we compared the Ag-processing machinery (APM) profile in human DC grown in the presence of IFN-alpha ((IFN)DC) or IL-4 ((IL-4)DC). Using a panel of APM component-specific mAb in Western blot experiments, we found that (IFN)DC preferentially express inducible proteasome subunits (LMP2, LMP7, and MECL1) both at immature and mature stages. In contrast, immature (IL-4)DC co-express both constitutive (beta1, beta2, and beta5) and inducible subunits, as shown by Western blotting analysis. In addition, immature (IFN)DC express higher levels of TAP1, TAP2, calnexin, calreticulin, tapasin, and HLA class I molecules than (IL-4)DC. The different proteasome profiles of (IFN)DC and (IL-4)DC were associated with a greater ability of (IFN)DC to present an immunodominant epitope that requires LMP7 expression for its processing. In general, these data show the impact of cytokines on APM component expression and hence the Ag-processing ability of DC.

Treatment failure in hepatitis C: mechanisms of non-response

Hepatitis C virus (HCV) has evolved remarkable mechanisms that favor viral persistence by interfering with host innate and adaptive immune responses. These same mechanisms are likely to contribute to resistance to exogenously administered interferon used for HCV treatment. We review the host innate and adaptive immune responses in the context of HCV infection as well as the strategies by which these responses are subverted by the virus. In addition, the contribution of host factors, such as race and insulin resistance, to interferon non-responsiveness is discussed. Our progress in understanding the molecular underpinnings of interferon treatment failure in HCV infection has resulted in several promising and novel treatment strategies for HCV treatment non-responders.

Physiological role of plasmacytoid dendritic cells and their potential use in cancer immunity

Dendritic cells (DCs) play a pivotal role in the control of innate and adaptive immune responses. They are a heterogeneous cell population, where plasmacytoid dendritic cells (pDCs) are a unique subset capable of secreting high levels of type I IFNs. It has been demonstrated that pDCs can coordinate events during the course of viral infection, atopy, autoimmune diseases, and cancer. Therefore, pDC, as a main source of type I IFN, is an attractive target for therapeutic manipulations of the immune system to elicit a powerful immune response against tumor antigens in combination with other therapies. The therapeutic vaccination with antigen-pulsed DCs has shown a limited efficacy to generate an effective long-lasting immune response against tumor cells. A rational manipulation and design of vaccines which could include DC subsets outside “Langerhans cell paradigm” might allow us to improve the therapeutic approaches for cancer patients.

Chemotherapy enhances vaccine-induced antitumor immunity in melanoma patients

Combination of chemotherapy with cancer vaccines is currently regarded as a potentially valuable therapeutic approach for the treatment of some metastatic tumors, but optimal modalities remain unknown. We designed a phase I/II pilot study for evaluating the effects of dacarbazine (DTIC) on the immune response in HLA-A2(+) disease-free melanoma patients who received anticancer vaccination 1 day following chemotherapy (800 mg/mq i.v.). The vaccine, consisting of a combination of HLA-A2 restricted melanoma antigen A (Melan-A/MART-1) and gp100 analog peptides (250 microg each, i.d.), was administered in combination or not with DTIC to 2 patient groups. The combined treatment is nontoxic. The comparative immune monitoring demonstrates that patients receiving DTIC 1 day before the vaccination have a significantly improved long-lasting memory CD8(+) T cell response. Of relevance, these CD8(+) T cells recognize and lyse HLA-A2(+)/Melan-A(+) tumor cell lines. Global transcriptional analysis of peripheral blood mononuclear cells (PBMC) revealed a DTIC-induced activation of genes involved in cytokine production, leukocyte activation, immune response and cell motility that can favorably condition tumor antigen-specific CD8(+) T cell responses. This study represents a proof in humans of a chemotherapy-induced enhancement of CD8(+) memory T cell response to cancer vaccines, which opens new opportunities to design novel effective combined therapies improving cancer vaccination effectiveness.

Signalling pathways leading to IFN-alpha production in human plasmacytoid dendritic cell and the possible use of agonists or antagonists of TLR7 and TLR9 in clinical indications

Plasmacytoid dendritic cells (PDC) are highly specialized immune cells capable of producing large amounts of type I and III IFN in response to viral infection. This response is mediated through TLR7 and TLR9 signalling pathways. In addition, PDC can differentiate into fully mature dendritic cells able to efficiently crosspresent viral antigens, thus playing an important role in adaptive immunity. This dual property of PDC is being used in clinical settings where synthetic TLR7 and TLR9 ligands are currently evaluated in clinical trials for the treatment of viral infections, allergies and cancers. Interestingly, there is evidence suggesting that chronic activation of PDC by endogenous RNA and DNA containing immune complexes maybe an important mechanism of driving autoimmunity and significant efforts to develop bi-functional antagonists of TLR7 and TLR9 are currently underway.

Antiviral-activated dendritic cells: a paracrine-induced response state

Infection of immature dendritic cells (DCs) by virus stimulates their maturation into APC. Infected DCs can also expose uninfected DCs to a panoply of cytokines/chemokines via paracrine signaling. Mathematical modeling suggests that a high rate of paracrine signaling is likely to occur among DCs located in three-dimensional space. Relatively little is known about how secreted factors modify the early response to virus infection. We used a transwell experimental system that allows passage of secreted factors, but not direct contact, between virus-infected DCs and uninfected DCs to investigate paracrine signaling responses. Paracrine signaling from infected DCs induced an antiviral-primed DC state distinct from that of mature virus-infected DCs that we refer to as antiviral-activated DCs (AVDCs). AVDCs had increased surface MHC class II and CD86 levels, but in contrast to virus-infected DCs, their MHC class I levels were unchanged. Imaging flow cytometry showed that AVDCs had an increased rate of phagocytosis compared with naive DCs. Experiments with IFN-beta cytokine indicated that it may be responsible for CD86, but not MHC class II regulation in AVDCs. Both IFN-inducible and IFN-independent genes are up-regulated in AVDCs. Notably, AVDCs are relatively resistant to virus infection in comparison to naive DCs and achieve accelerated and augmented levels of costimulatory molecule expression with virus infection. AVDCs show a distinct antiviral-primed state of DC maturation mediated by DC paracrine signaling. Although further in vivo study is needed, the characteristics of the AVDC suggest that it is well suited to play a role in the early innate-adaptive transition of the immune system.

IFN-alpha in the generation of dendritic cells for cancer immunotherapy

Dendritic cells (DCs) play a crucial role in linking innate and adaptive immunity, by virtue of their unique ability to take up and process antigens in the peripheral blood and tissues and, upon migration to draining lymph nodes, to present antigen to resting lymphocytes. Notably, these DC functions are modulated by cytokines and chemokines controlling the activation and maturation of these cells, thus shaping the response towards either immunity or tolerance.An ensemble of recent studies have emphasized an important role of type I IFNs in the DC differentiation/activation, suggesting the existence of a natural alliance between these cytokines and DCs in linking innate and adaptive immunity. Herein, we will review how type I IFNs can promote the ex vivo differentiation of human DCs and orient DC functions towards the priming and expansion of protective antitumor immune responses. We will also discuss how the knowledge on type I IFN-DC interactions could be exploited for the design of more selective and effective strategies of cancer immunotherapy.

Optimization of human immunodeficiency virus gag expression by newcastle disease virus vectors for the induction of potent immune responses

One attractive strategy for the development of a human immunodeficiency virus (HIV) vaccine is the use of viral vectors with a proven safety profile and an absence of preexisting immunity in humans, such as Newcastle disease virus (NDV). Several NDV vaccine vectors have been generated, and their immunogenicities have been investigated with different animal models. However, a systematic study to evaluate the optimal insertion site of the foreign antigens into NDV that results in enhanced immune responses specific to the antigen has not yet been conducted. In this article, we describe the ability of NDV expressing HIV Gag to generate a Gag-specific immune response in mice. We also have determined the optimal insertion site into the NDV genome by generating recombinant NDV-HIVGag viruses in which HIV gag was located at different transcriptional positions throughout the NDV viral genome. All recombinant viruses were viable, grew to similar titers in embryonated chicken eggs, and expressed Gag in a stable manner. Our in vivo experiments revealed that higher HIV Gag protein expression positively correlates with an enhanced CD8(+) T-cell-mediated immune response and protective immunity against challenge with vaccinia virus expressing HIV Gag. We also inserted a codon-optimized version of HIV gag in the described best location, between the P and M genes. Virus expressing the codon-optimized version of HIV gag induced a higher expression of the protein and an enhanced immune response against HIV Gag in mice. These results indicate that strategies directed toward increasing antigen expression by NDV result in enhanced immunogenicity and vaccine efficacy.

Dendritic cell-based cancer vaccination: quo vadis?

Dendritic cells (DCs) play a central role in the initiation and regulation of primary immune responses. DCs loaded with tumor-associated antigens induce anti-tumoral cytotoxic T cells in vitro and in vivo. However, clinical trials using ex vivo-generated DCs have failed to demonstrate clinical efficacy. This review summarizes recent advances in concepts and techniques that are providing new impulses to DC-based cancer vaccination. Improvements in protocols for ex vivo-generation of DCs, innovations in immunomonitoring, strategies to overcome tumor-induced immunosuppression and insights into the mutual beneficial effects of vaccines and chemotherapy are all considered. Furthermore, we highlight novel developments in cell-free vaccines targeting DCs in vivo.

CXCL10/CXCR3-mediated responses promote immunity to respiratory syncytial virus infection by augmenting dendritic cell and CD8(+) T cell efficacy

The induction of inflammatory cytokines during respiratory viral infections contributes to both disease pathogenesis and resolution. The present studies investigated the role of the chemokine CXCL10 and its specific receptor, CXCR3, in the host response to pulmonary respiratory syncytial virus (RSV) infection. Antibody-mediated neutralization of CXCL10 resulted in a significant increase in disease pathogenesis, including airway hyperresponsiveness (AHR), mucus gene expression, and impaired viral clearance. When the pulmonary cytokine levels were examined, only type I IFN and IL-12p70 were significantly reduced. These latter observations were reflected in reduced dendritic cell (DC) numbers and DC maturation in the lungs of RSV-infected mice treated with anti-CXCL10. Neutralization of the only known receptor for CXCL10, CXCR3, resulted in similar increases in pathogenic responses. When bone marrow-derived DC were incubated with CXCL10 and RSV, an up-regulation of type I IFN was observed. In addition, T lymphocytes were also examined and a significant decrease in the number of RSV M2 peptide-specific CD8(+) T cells was identified. These findings highlight a previously unappreciated role for the CXCL10:CXCR3 signaling axis in RSV-infected animals by recruiting virus-specific T cells into the lung and promoting viral clearance.

Induction of CD83+CD14+ nondendritic antigen-presenting cells by exposure of monocytes to IFN-alpha

IFN-alpha is a well-known agent for treatment of viral and malignant diseases. It has several modes of actions, including direct influence on the immune system. We investigated IFN-alpha effects on PBMC in terms of dendritic cell (DC) differentiation, as PBMC are exposed to high IFN-alpha levels during treatment of infections and cancers. We show that in vitro IFN-alpha exposure induced rapid and strong up-regulation of the DC-maturation markers CD80, CD86, and CD83 in bulk PBMC. Consistently, IFN-alpha induced up-regulation of these molecules on purified monocytes within 24 h. Up-regulation of CD80 and CD83 expression was IFN-alpha concentration-dependent. In contrast to GM-CSF + IL-4-generated DCs, most of the IFN-alpha-challenged CD83(+) cells coexpressed the monocyte marker CD14. Despite a typical mature DC immunophenotype, IFN-alpha-treated monocytes conserved phagocytic activity and never acquired a dendritic morphology. In mixed lymphocyte reactions IFN-alpha-treated monocytes were less potent than GM-CSF + IL-4-generated DCs but significantly more potent than untreated monocytes to induce T cell proliferation in bulk PBMC. However, only GM-CSF + IL-4-generated DCs were able to induce a significant proliferation of naive CD4(+) T cells. Notably, autologous memory CD4(+) T cells proliferated when exposed to tetanus toxoid-pulsed IFN-alpha-treated monocytes. At variance with untreated or GM-CSF + IL-4-exposed monocytes, those challenged with IFN-alpha showed long-lasting STAT-1 phosphorylation. Remarkably, CD83(+)CD14(+) cells were present in varicella skin lesions in close contact with IFN-alpha-producing cells. The present findings suggest that IFN-alpha alone promptly generates nondendritic APCs able to stimulate memory immune responses. This may represent an additional mode of action of IFN-alpha in vivo.