Biological activity of interleukins-28 and -29: comparison with type I interferons

IFNalpha and IFNlambda differ in their antiproliferative effects and duration of JAK/STAT signaling activity

Interferon (IFN)lambda, also known as IL-28A, IL-28B or IL-29, is a new type III IFN, which like type I IFN(alpha/beta), activates common elements of the JAK/STAT signaling pathway and exhibits antiproliferative activity. Currently, IFNalpha is used in the treatment of certain forms of cancer, but its antitumor effects are limited and associated with high toxicity. In this study, we determined whether IFNlambda induced the same level of cell growth inhibition relative to IFNalpha. To this effect HaCaT cells, which are typically growth inhibited by IFNalpha, underwent apoptosis in response to IFNlambda. Next, in contrast to IFNalpha stimulation, IFNlambda prolonged the duration of activated STAT1 and STAT2. Furthermore, the kinetics of IFN-stimulated genes was different as IFNlambda induced a delayed but stronger induction of IFN-responsive genes. Components of the JAK/STAT pathway remained essential for the antiproliferative effects of IFNalpha and IFNlambda. IFNlambda-induced persistence of STAT activation required de novo protein synthesis and was in part due to a delay in STAT2 inactivation. Thus our data demonstrate that the duration of IFNlambda signaling is different from that of IFNalpha, and that IFNlambda could be a suitable cytokine to evaluate for cancer therapy.

Antagonizing activity of vaccinia virus E3L against human interferons in Huh7 cells

The E3L protein of vaccinia virus (VV) is well known for its capacity to evade cellular innate antiviral immunity related to interferon (IFN), for example PKR and RNaseL mediated antiviral activities. However, due to the limited range of cells that support VV E3L deletion mutant replication, the full capacity of E3L inhibiting the innate immune response induced by IFNs remains to be examined. In this report, the inhibition activity of VV E3L against a wide spectrum of human IFNs, including type I IFNs (12 IFN-alpha subtypes, IFN-beta, and IFN-omega), and type II IFN (gamma), was comparatively examined using the Copenhagen strain E3L deletion mutant and its revertant control virus in a human hepatoma cell line, Huh7. Deletion of the E3L open reading frame rendered the mutant VV sensitive to all types of IFNs, while the revertant VV was strongly resistant to these treatments. Furthermore, we show that the inhibition of VV E3L deletion mutant by IFN occurs at the stage of intermediate gene translation, while the expression of early genes and transcription of intermediate genes are largely unaffected. Using specific siRNAs to suppress the classical IFN-induced antiviral pathways, we found that PKR is the key factor modulated by E3L, while the RNaseL and MxA pathways play limited roles in this Huh7 cell system. Thus, our data demonstrates that VV E3L can mediate strong inhibition activity against all human type I and type II IFNs, mainly through modulation of the PKR pathway in Huh7 cells.

Biological characterisation of a recombinant Atlantic salmon type I interferon synthesized in Escherichia coli

Type I (alpha/beta) interferons (IFNs) are a family of cytokines that stimulate the expression of numerous proteins that mediate an antiviral state in uninfected cells. Two Atlantic salmon (Salmo salar) IFN-alpha (SasaIFN-alpha1 & 2) genes have previously been cloned and both were found to contain a putative N-linked glycosylation site. Recombinant SasaIFN-alpha1 (rSasaIFN-alpha1) produced in eukaryotic systems has repeatedly been shown to confer antiviral properties. However, different IFN-alpha subtypes may exhibit differential antiviral activities and be subject to glycosylation. To evaluate the potential therapeutic impact of a rSasaIFN-alpha, the mature form of the SasaIFN-alpha2 protein was produced in a high-level Escherichia coli expression system. Expression of the rSasaIFN-alpha2 was detected by SDS-PAGE and Western blot, and its identity was confirmed by mass spectrometry. In the homologous Chinook salmon embryonic (CHSE-214) cell line, the rSasaIFN-alpha2 incited early expression of the IFN-induced Mx protein and exhibited high antiviral activity of about 2.8 x 10(6) U mg(-1) against infectious pancreatic necrosis virus (IPNV). Conversely, antiviral protection by rSasaIFN-alpha2 was not observed in a heterologous Japanese flounder embryo (HINAE) cell line. Hence, a biologically active form of rSasaIFN-alpha2 was successfully produced using a glycosylation-deficient prokaryotic system and purified to homogeneity, suggesting that glycosylation is not required for its antiviral activity.

Interferons and viruses: an interplay between induction, signalling, antiviral responses and virus countermeasures

The interferon (IFN) system is an extremely powerful antiviral response that is capable of controlling most, if not all, virus infections in the absence of adaptive immunity. However, viruses can still replicate and cause disease in vivo, because they have some strategy for at least partially circumventing the IFN response. We reviewed this topic in 2000 [Goodbourn, S., Didcock, L. & Randall, R. E. (2000). J Gen Virol 81, 2341-2364] but, since then, a great deal has been discovered about the molecular mechanisms of the IFN response and how different viruses circumvent it. This information is of fundamental interest, but may also have practical application in the design and manufacture of attenuated virus vaccines and the development of novel antiviral drugs. In the first part of this review, we describe how viruses activate the IFN system, how IFNs induce transcription of their target genes and the mechanism of action of IFN-induced proteins with antiviral action. In the second part, we describe how viruses circumvent the IFN response. Here, we reflect upon possible consequences for both the virus and host of the different strategies that viruses have evolved and discuss whether certain viruses have exploited the IFN response to modulate their life cycle (e.g. to establish and maintain persistent/latent infections), whether perturbation of the IFN response by persistent infections can lead to chronic disease, and the importance of the IFN system as a species barrier to virus infections. Lastly, we briefly describe applied aspects that arise from an increase in our knowledge in this area, including vaccine design and manufacture, the development of novel antiviral drugs and the use of IFN-sensitive oncolytic viruses in the treatment of cancer.

Type III and I interferons increase HIV uptake and replication in human cells that overexpress CD4, CCR5, and CXCR4

The newly discovered type III interferon lambda (IFN-lambda) has antiviral activity against a broad spectrum of viruses and potent immune-related activities. Its major producers are peripheral blood mononuclear cells (PBMCs) and dendritic cells. The above functions and cells are deeply involved in AIDS pathogenesis, but there is no information so far on IFN-lambda effects on HIV. Therefore we addressed the sensitivity of HIV-1 replication to cell exposure to human IFN-lambda2. Human PBMCs and C8166 T cells were treated with human Type III or Type I IFNs, and the ability of HIV-1 to bind and replicate in untreated and IFN-treated cells was investigated. Virus amounts were quantified by infectivity and p24 assays. In parallel, we evaluated the possible antiproliferative effects of IFN-lambda2 and the expression of CD4, CXCR4, and CCR5 genes, whose transcripts were quantified by real time RT-PCR. Data showed increased adsorption of HIV to IFN-treated cells in a dose-dependent fashion. Virus yields increased accordingly. In both systems the accumulation of CD4, CXCR4, and CCR5 transcripts was increased, particularly in PBMCs. Antiproliferative activity and classical antiviral state were instead detected on PBMCs, but not on C8166 cells. We concluded that pretreatment of PBMCs and C8166 cells with Type III and Type I IFNs causes increased HIV binding and replication. These effects are likely to be due to increased expression of HIV receptors and coreceptors on the plasma membrane. These findings indicate another mechanism utilized by HIV for subversion of host defenses.

Purification and characterization of prokaryotically expressed human interferon-lambda2

A system for the production of soluble interferon (IFN)-lambda2 was developed by fusing the IFN-lambda2, NusA protein, polyhistidine and S peptide genes and then expressing the fused product (Nus-His-S-tagged IFN-lambda2) in Escherichia coli. The expressed fusion protein was purified by Ni-NTA affinity chromatography. The fusion tag was removed from recombinant IFN-lambda2 by cleavage with enterokinase. N-Terminal sequencing confirmed the identity of the purified protein. When compared with commercial IFN-alpha2b, IFN-lambda2 had similar antiviral activity. The production and characterization of biologically active IFN-lambda2 will be beneficial for its potential role in clinical applications.

IL-28 and IL-29: newcomers to the interferon family

IL-28 and IL-29 were recently described as members of a new cytokine family that shares with type I interferon (IFN) the same Jak/Stat signalling pathway driving expression of a common set of genes. Accordingly, they have been named IFN lambda. IFNs lambda exhibit several common features with type I IFNs: antiviral activity, antiproliferative activity and in vivo antitumour activity. Importantly, however, IFNs lambda bind to a distinct membrane receptor, composed of IFNLR1 and IL10R2. This specific receptor usage suggests that this cytokine family does not merely replicate the type I IFN system and justifies its designation as type III IFN by the nomenclature committee of the International Society of Interferon and Cytokine Research.

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.

Type III interferon (IFN) induces a type I IFN-like response in a restricted subset of cells through signaling pathways involving both the Jak-STAT pathway and the mitogen-activated protein kinases

Type III interferon (IFN) is a novel member of the interferon family. Type III IFN utilizes a receptor complex different from that of type I IFN, but both types of IFN induce STAT1, STAT2, and STAT3 activation. Here we describe a detailed comparison of signal transduction initiated by type I and type III IFN. Gene expression array analysis showed that IFN types I and III induced a similar subset of genes. In particular, no genes were induced uniquely by type III IFN. Next, we used chromatin immunoprecipitation (ChIP) analysis to investigate the promoter activation by types I and III IFN. The ChIP assays demonstrated that stimulation of cells with both type I and type III IFN resulted in the recruitment of ISGF3 transcription factor components to the promoter region of responsive genes and in an increase of polymerase II loading and histone acetylation. Whereas IFN type I signaling was observed for a broad spectrum of cell lines, type III IFN signaling was more restricted. The lack of IFN type III signaling was correlated with a low expression of the IL28Ra component of the IFN type III receptor, and IL28Ra overexpression was sufficient to restore IFN type III signaling. We also tested the activation of mitogen-activated protein (MAP) kinases by type III IFN and found that type III IFN relies strongly upon both p38 and JNK MAP kinases for gene induction.

Induction of MxA gene expression by influenza A virus requires type I or type III interferon signaling

The human MxA gene belongs to the class of interferon (IFN)-stimulated genes (ISGs) involved in antiviral resistance against influenza viruses. Here, we studied the requirements for MxA induction by influenza A virus infection. MxA is transcriptionally upregulated by type I (alpha and beta) and type III (lambda) IFNs. Therefore, MxA is widely used in gene expression studies as a reliable marker for IFN bioactivity. It is not known, however, whether viruses can directly activate MxA expression in the absence of secreted IFN. By using an NS1-deficient influenza A virus and human cells with defects in IFN production or the STAT1 gene, we studied the induction profile of MxA by real-time reverse transcriptase PCR. The NS1-deficient virus is known to be a strong activator of the IFN system because NS1 acts as a viral IFN-antagonistic protein. Nevertheless, MxA gene expression was not inducible by this virus upon infection of IFN nonproducer cells and STAT1-null cells. Likewise, neither IFN-alpha nor IFN-lambda had a sizeable effect on the STAT1-null cells, indicating that MxA expression requires STAT1 signaling and cannot be triggered directly by virus infection. In contrast, the expression of the IFN-stimulated gene ISG56 was induced by influenza virus in these cells, confirming that ISG56 differs from MxA in being directly inducible by viral triggers in an IFN-independent way. In summary, our study reveals that MxA is a unique marker for the detection of type I and type III IFN activity during virus infections and IFN therapy.

Dendritic cells and interferon-mediated autoimmunity

Dendritic cells (DCs) are central cells of the immune responses. They can be considered as the most influential antigen-presenting cells in the body because of their unique role in initiating immunity against most types of antigens. Recent studies have clearly established that the state of maturation of DC can be crucial for the ability of these antigen-presenting cells to inhibit or induce T-cell-mediated autoimmune diseases. Type I interferon has been shown to be produced at very high amounts by a specific type of DC (pDC). In recent years, the study of multiple autoimmune diseases has pointed to a central role for type I interferon (IFN-I) in disease pathogenesis, in particular through the IFN-molecular signature deciphered in some of these diseases. One hypothesis would be that IFN directly affects multiple actors of the immune reaction such as T cells and B cells and that it can induce the unabated activation of peripheral dendritic cells. On the other hand, type II IFN has been considered as pathogenic in multiple autoimmune diseases leading to the paradigm of TH-1 type autoimmune diseases. The discovery of the TH-17 type of cells and the protective role IFN-gamma can exert on particular phases of these diseases urge one to re-evaluate this assumption.

On-column refolding purification and characterization of recombinant human interferon-lambda1 produced in Escherichia coli

Interferon-lambda1 (IFN-lambda1) is a member of the recently discovered type III IFNs (IFN-lambda), which possesses antiviral, antitumor, and immunomodulatory activities. In this study, the recombinant human IFN-lambda1 containing a hexahistidine tag was expressed in Escherichia coli. IFN-lambda1 was overexpressed under the control of T7 promoter and most of the protein existed in the form of inclusion bodies. The expressed insoluble protein was solubilized with urea, purified and refolded by one-step immobilized metal-ion affinity chromatography using Ni(2+)-nitrilotriacetic acid agarose. The purified IFN-lambda1 appeared as a single band on SDS-PAGE and the purity was more than 95%. The yield was 86 mg IFN-lambda1 from 1L of bacterial culture. Western blotting and N-terminal sequencing confirmed the identity of the purified protein. The purified IFN-lambda1 exhibited specific antiviral activity as demonstrated by a cytopathic effect reduction assay. Thus, this on-column refolding method provides an efficient way to obtain an active IFN-lambda1 with high yield and high purity.

Human interferon lambda-1 (IFN-lambda1/IL-29) modulates the Th1/Th2 response

Interferon lambda-1 (IFN-lambda1/IL-29) is a member of the Type-III interferon family, which contains three ligands: IFN-lambda1, 2 and 3. These three ligands use the same unique heterodimeric receptor composed of CRF2-12 (IFN-lambda-R1/IL-28Ralpha) and CRF2-4 (IL10-R-beta) chains. Like their close relatives, the Type-I interferons, IFN-lambda1, 2 and 3, promote the phosphorylation of STAT1 and STAT2, induce the ISRE3 complex, elevate OAS and MxA expression and exhibit antiviral activity in vitro. Their use of the IL10-R-beta chain and their ability to phosphorylate STAT3, STAT4 and STAT5 suggested that they may also exhibit immunomodulatory activity; their antiviral action led us to hypothesize that this activity might be directed toward the Th1/Th2 system. Here, we have demonstrated that IFN-lambda1 altered the activity of Th cells in three separate experimental systems: (i) mitogen stimulation, (ii) mixed-lymphocyte reaction (MLR) and (iii) stimulation of naive T cells by monocyte-derived dendritic cells (mDC). In Con-A stimulation assays, the inclusion of IFN-lambda1 consistently led to markedly diminished levels of secreted interleukin (IL-13) with occasional coincident, modest elevation of secreted IFN-gamma. IL-13 secretion was 100-fold more sensitive to IFN-lambda1 than was IFN-gamma secretion. These observations were also made in the allogeneic two-way MLR. IFN-lambda1 was able to alter cytokine-mediated Th biasing and when naive T cells were exposed to allogeneic mDC that had been matured in the presence of IFN-lambda1, secreted IL-13 was again markedly and consistently reduced, whereas secreted IFN-gamma was largely unaltered. These functions were independent of IL-10. Our data support a hitherto unsuspected role for IFN-lambda1 in modulating the development of Th1 and Th2 cells, with an apparent emphasis on the diminution of IL-13 secretion.

Interferon lambda-1 (IFN-lambda1/IL-29) induces ELR(-) CXC chemokine mRNA in human peripheral blood mononuclear cells, in an IFN-gamma-independent manner

Interferon lambda-1 (IFN-lambda1), the prototype Type-III interferon, has antiviral functions similar to those of the Type-I interferons, IFN-alpha and IFN-beta. However, IFN-lambda1 is capable of signaling through almost all STAT molecules and so it is possible that it may have novel immunoregulatory functions in addition to antiviral ones. From a range of chemokines tested, IFN-lambda1 elevated mRNA levels of only 'Monokine induced by IFN-gamma' (MIG/CXCL9), 'IFN-gamma inducible protein-10' (IP-10/CXCL10) and 'IFN-gamma inducible T-cell alpha chemoattractant' (I-TAC/CXCL11) from human peripheral blood mononuclear cells. As their names suggest, these chemokines are also induced by IFN-gamma, the only member of the Type-II interferon family. This action of IFN-lambda1 did not depend on intermediate induction of IFN-gamma and is therefore, likely to be independent of IFN-gamma. Further, our results suggest that donors responded to IFN-lambda1 stimulation either 'early' or 'late'. Overall the action of IFN-lambda1 was similar to that previously reported for IFN-gamma and may invite more detailed investigation of the role of IFN-lambda1 at the innate/adaptive interface.

Modulation of the human cytokine response by interferon lambda-1 (IFN-lambda1/IL-29)

The interferon lambda family (IFN-lambda1/2/3) is a newly described group of cytokines that are related to both the type-1 interferons and IL-10 family members. These novel cytokines are induced during viral infection and, like type-1 interferons, display significant anti-viral activity. In order to understand their function in more depth, we have examined the ability of IFN-lambda1/IL-29 to regulate cytokine production by human immune cells. Whole peripheral blood mononuclear cells (PBMC) exposed to IFN-lambda1 specifically upregulated IL-6, -8 and -10 but there were no visible effects on TNF or IL-1. This response was produced in a dose-dependant fashion and was inhibited by IL-10. Examination of purified cell populations isolated from PBMC demonstrated that monocytes, rather than lymphocytes, were the major IFN-lambda1-responsive cellular subset, producing IL-6, -8 and -10 in response to IFN-lambda1. Monocyte responses induced by low-level LPS stimulation were also synergistically enhanced by the presence of IFN-lambda1. Human macrophages were also shown to react to IFN-lambda1 similarly to monocytes, by producing the cytokines IL-6, -8 and -10. In conclusion, we have shown that IFN-lambda1, a cytokine produced in response to viral infection, activates both monocytes and macrophages producing a restricted panel of cytokines and may therefore be important in activating innate immune responses at the site of viral infection.

Thermal stability of the WHO international standard of interferon alpha 2b (IFN-alpha 2b): application of new reporter gene assay for IFN-alpha 2b potency determinations

A World Health Organization requirement for biological standards is that they should exhibit long-term stability at their recommended storage temperature. Thermal stability is usually predicted in accelerated thermal degradation studies, where ampoules of the lyophilized standard are stored at elevated temperatures for relatively short times before testing. To confirm the predicted thermal stability of the 2nd international standard of human interferon alpha 2b (IFN-alpha2b; 95/566), we tested the potency of the ampouled contents of this standard after 9 years storage at the customary storage temperature of -20 degrees C in comparison with ampoules of the IS which had been stored continuously at temperatures ranging from -150 degrees C to 56 degrees C. Since IFN-alpha2b potency estimates derived from the results of antiviral assays (AVA) showed high within-assay variability, we investigated a novel reporter gene assay (RGA) based on induction of secreted alkaline phosphatase (SEAP) for comparability and precision of such estimations. We show that this RGA generated comparable estimates with overall lower variation. Additionally, the SEAP conversion of p-nitrophenyl phosphate to yellow product could be followed kinetically. Absorbance readings were shown to increase with time in proportion with increasing concentration of IFN-alpha2b. When the time-dependent increments of absorbance were plotted graphically, the slopes of lines corresponded to concentration. This approach enabled single dilutions of IFN samples, identical in molecular structure to an IFN-alpha2b standard, to be used for potency estimates by interpolation of slope value against those of the standard at fixed concentrations. It appears attractive for high through-put potency testing of various R&D IFN-alpha2b samples.

The NS2 protein of human respiratory syncytial virus suppresses the cytotoxic T-cell response as a consequence of suppressing the type I interferon response

The NS1 and NS2 proteins of human respiratory syncytial virus (HRSV) have been shown to antagonize the type I interferon (IFN) response, an effect subject to host range constraints. We have now found that the HRSV NS2 protein strongly controls IFN induction in mouse cells in vitro, validating the use of the mouse model to study the consequences of these gene deletions on host immunity. We evaluated the effects of deleting the NS1 and/or NS2 gene on the induction of HRSV-specific pulmonary cytotoxic T lymphocytes (CTL) in BALB/c and 129S6 mice in response to intranasal infection with HRSV lacking the NS1 and/or NS2 gene and subsequent challenge with wild-type (wt) HRSV. In mice infected with HRSV lacking the NS2 gene (DeltaNS2) or lacking the NS2 gene in combination with the NS1 gene (DeltaNS1/2 HRSV), the magnitude of the pulmonary CTL response was substantially elevated compared to that of mice infected with wt HRSV or the DeltaNS1 mutant, whether measured by binding of CD8(+) cells to an HRSV-specific major histocompatibility complex class I tetramer, by measurement of CD8(+) cells secreting gamma interferon (IFN-gamma) in response to specific in vitro stimulation, or by a standard chromium release cell-killing assay. In contrast, in STAT1 knockout mice, which lack responsiveness to type I IFN, the level of IFN-gamma-secreting CD8(+) cells was not significantly different for HRSV lacking the NS2 gene, suggesting that the increase in CTL observed in IFN-responsive mice is type I IFN dependent. Thus, the NS2 protein of HRSV suppresses the CTL component of the adaptive immune response, and this appears to be a consequence of its suppression of type I IFN.

IFN-lambda: novel antiviral cytokines

The first line of defense against viral infections is mediated by interferons (IFN)s, which are produced rapidly by the infected host. Type I IFNs (IFN-alpha/beta) are known to combat viruses both directly by inhibiting viral replication in the cells and indirectly by stimulating the innate and adaptive immune responses. Recently, a novel class of cytokines was discovered and named IFN-lambda (alternatively type III IFN or interleukin-28/29 [IL- 28/29]), based on IFN-like antiviral activity and induction of typical IFN-inducible genes. Here, we review the literature on IFN-lambda and discuss the current knowledge of the functions and mechanisms of action of IFN-lambda.

Anti-interferon autoantibodies in autoimmune polyendocrinopathy syndrome type 1

BACKGROUND

The autoimmune regulator (AIRE) gene influences thymic self-tolerance induction. In autoimmune polyendocrinopathy syndrome type 1 (APS1; OMIM 240300), recessive AIRE mutations lead to autoimmunity targetting endocrine and other epithelial tissues, although chronic candidiasis usually appears first. Autoimmunity and chronic candidiasis can associate with thymomas as well. Patients with these tumours frequently also have high titre immunoglobulin G autoantibodies neutralising type I interferon (IFN)-alpha and IFN-omega, which are secreted signalling proteins of the cytokine superfamily involved in both innate and adaptive immunity.

METHODS AND FINDINGS

We tested for serum autoantibodies to type I IFNs and other immunoregulatory cytokines using specific binding and neutralisation assays. Unexpectedly, in 60/60 Finnish and 16/16 Norwegian APS1 patients with both AIRE alleles mutated, we found high titre neutralising immunoglobulin G autoantibodies to most IFN-alpha subtypes and especially IFN-omega (60% homologous to IFN-alpha)-mostly in the earliest samples. We found lower titres against IFN-beta (30% homologous to IFN-alpha) in 23% of patients; two-thirds of these (from Finland only) also had low titres against the distantly related "type III IFN" (IFN-lambda1; alias interleukin-29). However, autoantibodies to the unrelated type II IFN, IFN-gamma, and other immunoregulatory cytokines, such as interleukin-10 and interleukin-12, were much rarer and did not neutralise. Neutralising titres against type I IFNs averaged even higher in patients with APS1 than in patients with thymomas. Anti-type I IFN autoantibodies preceded overt candidiasis (and several of the autoimmune disorders) in the informative patients, and persisted for decades thereafter. They were undetectable in unaffected heterozygous relatives of APS1 probands (except for low titres against IFN-lambda1), in APS2 patients, and in isolated cases of the endocrine diseases most typical of APS1, so they appear to be APS1-specific. Looking for potentially autoimmunising cell types, we found numerous IFN-alpha(+) antigen-presenting cells-plus strong evidence of local IFN secretion-in the normal thymic medulla (where AIRE expression is strongest), and also in normal germinal centres, where it could perpetuate these autoantibody responses once initiated. IFN-alpha2 and IFN-alpha8 transcripts were also more abundant in antigen-presenting cells cultured from an APS1 patient's blood than from age-matched healthy controls.

CONCLUSIONS

These apparently spontaneous autoantibody responses to IFNs, particularly IFN-alpha and IFN-omega, segregate like a recessive trait; their high "penetrance" is especially remarkable for such a variable condition. Their apparent restriction to APS1 patients implies practical value in the clinic, e.g., in diagnosing unusual or prodromal AIRE-mutant patients with only single components of APS1, and possibly in prognosis if they prove to predict its onset. These autoantibody responses also raise numerous questions, e.g., about the rarity of other infections in APS1. Moreover, there must also be clues to autoimmunising mechanisms/cell types in the hierarchy of preferences for IFN-omega, IFN-alpha8, IFN-alpha2, and IFN-beta and IFN-lambda1.

Novel interferon-lambdas induce antiproliferative effects in neuroendocrine tumor cells

Interferon-alpha (IFN-alpha) is used for biotherapy of neuroendocrine carcinomas. The interferon-lambdas (IL-28A/B and IL-29) are a novel group of interferons. In this study, we investigated the effects of the IFN-lambdas IL-28A and IL-29 on human neuroendocrine BON1 tumor cells. Similar to IFN-alpha, incubation of BON1 cells with IL-28A (10 ng/ml) and IL-29 (10 ng/ml) induced phosphorylation of STAT1, STAT2, and STAT3, significantly decreased cell numbers in a proliferation assay, and induced apoptosis as demonstrated by poly(ADP-ribose) polymerase (PARP)-cleavage, caspase-3-cleavage, and DNA-fragmentation. Stable overexpression of suppressor of cytokine signaling proteins (SOCS1 and SOCS3) completely abolished the aforementioned effects indicating that SOCS proteins act as negative regulators of IFN-lambda signaling in BON1 cells. In conclusion, the novel IFN-lambdas IL-28A and IL-29 potently induce STAT signaling and antiproliferative effects in neuroendocrine BON1 tumor cells. Thus, IFN-lambdas may hint a promising new approach in the antiproliferative therapy of neuroendocrine tumors.

Interferon-lambda-treated dendritic cells specifically induce proliferation of FOXP3-expressing suppressor T cells

The lambda interferons (IFN-lambdas), also known as IL-28 and IL-29, are coexpressed with IFN-beta after Toll-like-receptor (TLR) stimulation in human monocyte-derived dendritic cells (DCs). IFN-lambda shares with type I IFNs an intracellular signaling pathway that drives the expression of a common set of genes. However, IFN-lambda signaling is initiated through a membrane receptor system distinct from that of type I IFNs. Because IFNs produced by DCs in response to TLR stimulation are critical in the differentiation and maturation of DCs, we sought to investigate whether IFN-lambda exhibits specific effects on DC differentiation. In this work, we show that DCs acquire IFN-lambda responsiveness through the expression of the specific IFN-lambda receptor chain during their differentiation from monocytes. IFN-lambda-treated DCs express high levels of major histocompatibility complex class I (MHC class I) and MHC class II but low levels of costimulatory molecules. However, they express CCR7 and acquire the ability to migrate to lymph nodes when intravenously injected into SCID/Bg mice. In mixed lymphocyte reaction (MLR) cultures, IFN-lambda-treated DCs specifically induced IL-2-dependent proliferation of a CD4(+)CD25(+)Foxp3(+) T-cell subset with contact-dependent suppressive activity on T-cell proliferation initiated by fully mature DCs. IFN-lambdas are thus able to generate tolerogenic DCs, an activity that could thwart IFN-beta functions.

Lambda interferon (IFN-lambda), a type III IFN, is induced by viruses and IFNs and displays potent antiviral activity against select virus infections in vivo

Type III interferons (IFNs) (interleukin-28/29 or lambda interferon [IFN-lambda]) are cytokines with IFN-like activities. Here we show that several classes of viruses induce expression of IFN-lambda1 and -lambda2/3 in similar patterns. The IFN-lambdas were-unlike alpha/beta interferon (IFN-alpha/beta)-induced directly by stimulation with IFN-alpha or -lambda, thus identifying type III IFNs as IFN-stimulated genes. In vitro assays revealed that IFN-lambdas have appreciable antiviral activity against encephalomyocarditis virus (EMCV) but limited activity against herpes simplex virus type 2 (HSV-2), whereas IFN-alpha potently restricted both viruses. Using three murine models for generalized virus infections, we found that while recombinant IFN-alpha reduced the viral load after infection with EMCV, lymphocytic choriomeningitis virus (LCMV), and HSV-2, treatment with recombinant IFN-lambda in vivo did not affect viral load after infection with EMCV or LCMV but did reduce the hepatic viral titer of HSV-2. In a model for a localized HSV-2 infection, we further found that IFN-lambda completely blocked virus replication in the vaginal mucosa and totally prevented development of disease, in contrast to IFN-alpha, which had a more modest antiviral activity. Finally, pretreatment with IFN-lambda enhanced the levels of IFN-gamma in serum after HSV-2 infection. Thus, type III IFNs are expressed in response to most viruses and display potent antiviral activity in vivo against select viruses. The discrepancy between the observed antiviral activity in vitro and in vivo may suggest that IFN-lambda exerts a significant portion of its antiviral activity in vivo via stimulation of the immune system rather than through induction of the antiviral state.

Purification and characterization of recombinant human interleukin-29 expressed in Escherichia coli

Human interleukin (IL)-29 is the latest member of the class II cytokine family. However, as a result of lacking efficient method to generate relatively large quantity of IL-29, little is known of its functions in man. In the present study, an Escherichia coli expression system for the rapid expression of the human IL-29 gene was developed. It involved of cloning IL-29 gene into the pET-44 Ek/LIC vector, which allowed expression of IL-29 with a fusion tag consisting of the NusA protein, polyhistidine and S peptide (Nus-His-S-tag), and introducing a thrombin recognition site between the fusion tag and IL-29. The expressed fusion protein was purified by S-protein agarose affinity chromatography, and the fusion tag was removed from recombinant IL-29 by cleavage with thrombin. The purified IL-29 appeared a single band on SDS-PAGE, and the yield of IL-29 was 60 mg from 1 l of bacterial culture. N-terminal sequencing confirmed the identity of the purified protein. The recombinant IL-29 showed specific antiviral activity that was comparable to the commercially available IFN alfa-2b preparation.

Liposome-mediated IL-28 and IL-29 expression in A549 cells and anti-viral effect of IL-28 and IL-29 on WISH cells

AIM

To construct the recombinant vectors carrying interleukin (IL)-28A, IL-28B and IL-29 cDNAs and express them in human A549 cells, and analyze their antiviral activity in vesicular stomatitis virus (VSV)-infected human immortalized amnion epithelial cell line (WISH cells).

METHODS

Total cell RNA was extracted from human peripheral blood mononuclear cells (PBMC) activated with poly I:C. The cDNAs encoding human IL-28A, IL-28B, and IL-29 were amplified by reverse-transcription polymerase chain reaction (RT-PCR) and inserted into pcDNA3.1/V5-His-TOPO vectors. These recombinant vectors were transfected into human A549 cells by a liposome-mediated gene transfer method. Semiquantitative RT-PCR and Western blotting were used to detect the mRNA and protein expression of IL-28A, IL-28B, and IL-29. The antiviral activity of IL-28A, IL-28B, and IL-29 was determined by a cytopathic effect reduction assay on WISH cells using VSV as a challenge virus.

RESULTS

The DNA sequences of the inserts were identical to the published sequences encoding IL-28A, IL-28B, and IL-29 in GenBank. It was demonstrated that IL-28A, IL-28B, and IL-29 genes were markedly transcribed in transfected cells. Expression of all 3 interleukins in A549 cells was confirmed by Western blot analysis. IL-28 and IL-29 expressed by A549 cells, like interferon (IFN) alpha-2b, were able to protect WISH cells against VSV infection.

CONCLUSION

IL-28 and IL-29 cDNAs were successfully cloned and expressed in eukaryotic cells via transfection with pcDNA3.1/V5-His-TOPO-IL-28/IL-29. Transfection with this vector produced a specific antiviral activity similar to that of IFN-alpha, which will provide a new tool for the functional study of these cytokines in humans.