Interferon alpha augments activation-induced T cell death by upregulation of Fas (CD95/APO-1) and Fas ligand expression

The dawn of a new Era: mRNA vaccines in colorectal cancer immunotherapy

Colorectal cancer (CRC) is a typical cancer that accounts for 10% of all new cancer cases annually and nearly 10% of all cancer deaths. Despite significant progress in current classical interventions for CRC, these traditional strategies could be invasive and with numerous adverse effects. The poor prognosis of CRC patients highlights the evident and pressing need for more efficient and targeted treatment. Novel strategies regarding mRNA vaccines for anti-tumor therapy have also been well-developed since the successful application for the prevention of COVID-19. mRNA vaccine technology won the 2023 Nobel Prize in Physiology or Medicine, signaling a new direction in human anti-cancer treatment: mRNA medicine. As a promising new immunotherapy in CRC and other multiple cancer treatments, the mRNA vaccine has higher specificity, better efficacy, and fewer side effects than traditional strategies. The present review outlines the basics of mRNA vaccines and their advantages over other vaccines and informs an available strategy for developing efficient mRNA vaccines for CRC precise treatment. In the future, more exploration of mRNA vaccines for CRC shall be attached, fostering innovation to address existing limitations.

CD8+ T cells in the cancer-immunity cycle

CD8+ T cells are end effectors of cancer immunity. Most forms of effective cancer immunotherapy involve CD8+ T cell effector function. Here, we review the current understanding of T cell function in cancer, focusing on key CD8+ T cell subtypes and states. We discuss factors that influence CD8+ T cell differentiation and function in cancer through a framework that incorporates the classic three-signal model and a fourth signal-metabolism-and also consider the impact of the tumor microenvironment from a T cell perspective. We argue for the notion of immunotherapies as "pro-drugs" that act to augment or modulate T cells, which ultimately serve as the drug in vivo, and for the importance of overall immune health in cancer treatment and prevention. The progress in understanding T cell function in cancer has and will continue to improve harnessing of the immune system across broader tumor types to benefit more patients.

Anti-cancer immune responses to DNA damage response inhibitors: Molecular mechanisms and progress toward clinical translation

DNA damage response inhibitors are widely used anti-cancer agents that have potent activity against tumor cells with deficiencies in various DNA damage response proteins such as BRCA1/2. Inhibition of other proteins in this pathway including PARP, DNA-PK, WEE1, CHK1/2, ATR, or ATM can sensitize cancer cells to radiotherapy and chemotherapy, and such combinations are currently being tested in clinical trials for treatment of many malignancies including breast, ovarian, rectal, and lung cancer. Unrepaired DNA damage induced by DNA damage response inhibitors alone or in combination with radio- or chemotherapy has a direct cytotoxic effect on cancer cells and can also engage anti-cancer innate and adaptive immune responses. DNA damage-induced immune stimulation occurs by a variety of mechanisms including by the cGAS/STING pathway, STAT1 and downstream TRAIL pathway activation, and direct immune cell activation. Whether or not the relative contribution of these mechanisms varies after treatment with different DNA damage response inhibitors or across cancers with different genetic aberrations in DNA damage response enzymes is not well-characterized, limiting the design of optimal combinations with radio- and chemotherapy. Here, we review how the inhibition of key DNA damage response enzymes including PARP, DNA-PK, WEE1, CHK1/2, ATR, and ATM induces innate and adaptive immune responses alone or in combination with radiotherapy, chemotherapy, and/or immunotherapy. We also discuss current progress in the clinical translation of immunostimulatory DNA-damaging treatment regimens and necessary future directions to optimize the immune-sensitizing potential of DNA damage response inhibitors.

Rotavirus-Induced Expansion of Antigen-Specific CD8 T Cells Does Not Require Signaling via TLR3, MyD88 or the Type I Interferon Receptor

Rotavirus (RV) infection induces strong adaptive immunity. While protection from reinfection requires humoral immunity, initial clearance of infection depends on cytotoxic CD8 T cells. Type I classical dendritic cells (cDC1) excel at CD8 T cell induction through cross-presentation and are essential for optimal cytotoxicity towards RV. Upon sensing of infection-induced innate immune signals through pattern recognition receptors (PRRs), cumulating in autocrine type I interferon (IFN) signaling, cDC1 mature and migrate to the draining lymph nodes (LNs), where they prime adaptive immune cells. To analyze which PRR pathways lead to robust cytotoxicity in the context of RV infection, we measured RV-specific CD8 T cell priming in mice deficient for Toll-like receptor 3 (TLR3), recognizing double-stranded RNA, or for MyD88, the adapter for all other TLRs and IL-1 family cytokines. Individual TLR3- and MyD88-mediated signaling was not required for the priming of CD8 T cell responses to RV and neither deficiency impacted on RV clearance. Surprisingly, the accumulation of RV-specific CD8 T cells was also not altered in the absence of type I IFN signaling, while their ability to produce IFNγ and granzyme were blunted. Together, this suggests a substantial level of redundancy in the sensing of RV infection and the translation of signals into protective CD8 T cell immunity.

Stimulatory and inhibitory activity of STING ligands on tumor-reactive human gamma/delta T cells

Ligands for Stimulator of Interferon Genes (STING) receptor are under investigation as adjuvants in cancer therapy. Multiple effects have been described, including induction of immunogenic cell death and enhancement of CD8 T-cell mediated anti-tumor immunity. However, the potential effects of STING ligands on activation and effector functions of tumor-reactive human γδ T cells have not yet been investigated. We observed that cyclic dinucleotide as well as novel non-dinucleotide STING ligands diABZI and MSA-2 co-stimulated cytokine induction in Vδ2 T cells within peripheral blood mononuclear cells but simultaneously inhibited their proliferative expansion in response to the aminobisphosphonate Zoledronate and to γδ T-cell specific phosphoantigen. In purified γδ T cells, STING ligands co-stimulated cytokine induction but required the presence of monocytes. STING ligands strongly stimulated IL-1β and TNF-α secretion in monocytes and co-stimulated cytokine induction in short-term expanded Vδ2 γδ T-cell lines. Simultaneously, massive cell death was triggered in both cell populations. Activation of STING as revealed by TBK1/IRF3 phosphorylation and IP-10 secretion varied among STING-expressing tumor cells. STING ligands modulated tumor cell killing by Vδ2 T cells as analyzed in Real-Time Cell Analyzer to variable degree, depending on the tumor target and time course kinetics. Our study reveals complex regulatory effects of STING ligands on human γδ T cells in vitro. These results help to define conditions where STING ligands might boost the efficacy of γδ T cell immunotherapy in vivo.

Hepatitis-D Virus Infection Is Not Impaired by Innate Immunity but Increases Cytotoxic T-Cell Activity

Approximately 70 million humans worldwide are affected by chronic hepatitis D, which rapidly leads to liver cirrhosis and hepatocellular carcinoma due to chronic inflammation. The triggers and consequences of this chronic inflammation, induced by co-infection with the hepatitis D virus (HDV) and the hepatitis B virus (HBV), are poorly understood. Using CRISPR technology, we characterized the recognition of HDV mono- and co-infection by intracellular innate immunity and determined its influence on the viral life cycle and effector T-cell responses using different HBV and HDV permissive hepatoma cell lines. We showed that HDV infection is detected by MDA5 and -after a lag phase -induces a profound type I interferon response in the infected cells. The type I interferon response, however, was not able to suppress HDV replication or spread, thus providing a persistent trigger. Using engineered T-cells directed against the envelope proteins commonly used by HBV and HDV, we found that HDV immune recognition enhanced T-cell cytotoxicity. Interestingly, the T-cell effector function was enhanced independently of antigen presentation. These findings help to explain immune mediated tissue damage in chronic hepatitis D patients and indicate that combining innate triggers with T-cell activating therapies might allow for a curative approach.

Fas/FasL Signaling Regulates CD8 Expression During Exposure to Self-Antigens

Activation of self-reactive CD8+ T cells induces a peripheral tolerance mechanism that involves loss of CD8 expression. Because genetic deficiency of Fas and Fasl causes the accumulation of double-negative (DN; CD3+ TCR-αβ+ CD4- CD8-) T cells that have been proposed to derive from CD8+ cells, we decided to explore the role of Fas and FasL in self-antigen-induced CD8 downregulation. To this end, we quantified Fas and FasL induction by different stimuli and analyzed the effects of Fas/FasL deficiency during a protective immune response and after exposure to self-antigens. Our data describes how Fas and FasL upregulation differs depending on the setting of CD8 T cell activation and demonstrates that Fas/FasL signaling maintains CD8 expression during repetitive antigen stimulation and following self-antigen encounter. Together, our results reveal an unexpected role of Fas/FasL signaling and offer a new insight into the role of these molecules in the regulation of immune tolerance.

CD8 T Cell Exhaustion During Chronic Viral Infection and Cancer

Exhausted CD8 T (Tex) cells are a distinct cell lineage that arise during chronic infections and cancers in animal models and humans. Tex cells are characterized by progressive loss of effector functions, high and sustained inhibitory receptor expression, metabolic dysregulation, poor memory recall and homeostatic self-renewal, and distinct transcriptional and epigenetic programs. The ability to reinvigorate Tex cells through inhibitory receptor blockade, such as αPD-1, highlights the therapeutic potential of targeting this population. Emerging insights into the mechanisms of exhaustion are informing immunotherapies for cancer and chronic infections. However, like other immune cells, Tex cells are heterogeneous and include progenitor and terminal subsets with unique characteristics and responses to checkpoint blockade. Here, we review our current understanding of Tex cell biology, including the developmental paths, transcriptional and epigenetic features, and cell intrinsic and extrinsic factors contributing to exhaustion and how this knowledge may inform therapeutic targeting of Tex cells in chronic infections, autoimmunity, and cancer.

A genetic IFN/STAT1/FAS axis determines CD4 T stem cell memory levels and apoptosis in healthy controls and Adult T-cell Leukemia patients

Adult T-cell leukemia (ATL) is an aggressive, chemotherapy-resistant CD4+CD25+ leukemia caused by HTLV-1 infection, which usually develops in a minority of patients several decades after infection. IFN + AZT combination therapy has shown clinical benefit in ATL, although its mechanism of action remains unclear. We have previously shown that an IFN-responsive FAS promoter polymorphism in a STAT1 binding site (rs1800682) is associated to ATL susceptibility and survival. Recently, CD4 T stem cell memory (TSCM) Fashi cells have been identified as the hierarchical cellular apex of ATL, but a possible link between FAS, apoptosis, proliferation and IFN response in ATL has not been studied. In this study, we found significant ex vivo antiproliferative, antiviral and immunomodulatory effects of IFN-α treatment in short-term culture of primary mononuclear cells from ATL patients (n = 25). Bayesian Network analysis allowed us to integrate ex vivo IFN-α response with clinical, genetic and immunological data from ATL patients, thereby revealing a central role for FAS -670 polymorphism and apoptosis in the coordinated mechanism of action of IFN-α. FAS genotype-dependence of IFN-induced apoptosis was experimentally validated in an independent cohort of healthy controls (n = 20). The same FAS -670 polymorphism also determined CD4 TSCM levels in a genome-wide twin study (p = 7 × 10-11, n = 460), confirming a genetic link between apoptosis and TSCM levels. Transcriptomic analysis and cell type deconvolution confirmed the FAS genotype/TSCM link and IFN-α-induced downregulation of CD4 TSCM-specific genes in ATL patient cells. In conclusion, ex vivo IFN-α treatment exerts a pleiotropic effect on primary ATL cells, with a genetic IFN/STAT1/Fas axis determining apoptosis vs. proliferation and underscoring the CD4 TSCM model of ATL leukemogenesis.

Type 1 Interferon in the Human Intestine-A Co-ordinator of the Immune Response to the Microbiota

The human gut is in constant complex interaction with the external environment. Although much is understood about the composition and function of the microbiota, much remains to be learnt about the mechanisms by which these organisms interact with the immune system in health and disease. Type 1 interferon (T1IFN), a ubiquitous and pleiotropic family of cytokines, is a critical mediator of the response to viral, bacterial, and other antigens sampled in the intestine. Although inflammation is enhanced in mouse model of colitis when T1IFN signaling is lost, the action of T1IFN is context specific and can be pro- or anti-inflammatory. In humans, T1IFN has been used to treat inflammatory diseases, including multiple sclerosis and inflammatory bowel disease but intestinal inflammation can also develop after the administration of T1IFN. Recent findings indicate that "tonic" or "endogenous" T1IFN, induced by signals from the commensal microbiota, modulates the local signaling environment to prime the intestinal mucosal immune system to determine later responses to pathogens and commensal organisms. This review will summarize the complex immunological effects of T1IFN and recent the role of T1IFN as a mediator between the microbiota and the mucosal immune system, highlighting human data wherever possible. It will discuss what we can learn from clinical experiences with T1IFN and how the T1IFN pathway may be manipulated in the future to maintain mucosal homeostasis.

The Impact of the Interferon/TNF-Related Apoptosis-Inducing Ligand Signaling Axis on Disease Progression in Respiratory Viral Infection and Beyond

Interferons (IFNs) are well described to be rapidly induced upon pathogen-associated pattern recognition. After binding to their respective IFN receptors and activation of the cellular JAK/signal transducer and activator of transcription signaling cascade, they stimulate the transcription of a plethora of IFN-stimulated genes (ISGs) in infected as well as bystander cells such as the non-infected epithelium and cells of the immune system. ISGs may directly act on the invading pathogen or can either positively or negatively regulate the innate and adaptive immune response. However, IFNs and ISGs do not only play a key role in the limitation of pathogen spread but have also been recently found to provoke an unbalanced, overshooting inflammatory response causing tissue injury and hampering repair processes. A prominent regulator of disease outcome, especially in-but not limited to-respiratory viral infection, is the IFN-dependent mediator TRAIL (TNF-related apoptosis-inducing ligand) produced by several cell types including immune cells such as macrophages or T cells. First described as an apoptosis-inducing agent in transformed cells, it is now also well established to rapidly evoke cellular stress pathways in epithelial cells, finally leading to caspase-dependent or -independent cell death. Hereby, pathogen spread is limited; however in some cases, also the surrounding tissue is severely harmed, thus augmenting disease severity. Interestingly, the lack of a strictly controlled and well balanced IFN/TRAIL signaling response has not only been implicated in viral infection but might furthermore be an important determinant of disease progression in bacterial superinfections and in chronic respiratory illness. Conclusively, the IFN/TRAIL signaling axis is subjected to a complex modulation and might be exploited for the evaluation of new therapeutic concepts aiming at attenuation of tissue injury.

Type I Interferons Modulate CD8+ T Cell Immunity to mRNA Vaccines

mRNA vaccines have emerged as potent tools to elicit antitumor T cell immunity. They are characterized by a strong induction of type I interferons (IFNs), potent inflammatory cytokines affecting T cell differentiation and survival. Recent reports have attributed opposing roles for type I IFNs in modulating CD8+ T cell immunity to mRNA vaccines, from profoundly stimulatory to strongly inhibitory. The mechanisms behind this duality are unclear. Disentangling the factors governing the beneficial or detrimental impact of type I IFNs on CD8+ T cell responses is vital to the design of mRNA vaccines of increased potency. In light of recent advancements regarding the complex role of type I IFNs in regulating CD8+ T cell immunity to infectious diseases, we posit that the dual outcome of type I IFNs on CD8+ T cell responses to mRNA vaccination is determined by the timing and intensity of type I IFN induction relative to T cell receptor (TCR) activation.

Absence of autophagy promotes apoptosis by modulating the ROS-dependent RLR signaling pathway in classical swine fever virus-infected cells

A growing number of studies have demonstrated that both macroautophagy/autophagy and apoptosis are important inner mechanisms of cell to maintain homeostasis and participate in the host response to pathogens. We have previously reported that a functional autophagy pathway is trigged by infection of classical swine fever virus (CSFV) and is required for viral replication and release in host cells. However, the interplay of autophagy and apoptosis in CSFV-infected cells has not been clarified. In the present study, we demonstrated that autophagy induction with rapamycin facilitates cellular proliferation after CSFV infection, and that autophagy inhibition by knockdown of essential autophagic proteins BECN1/Beclin 1 or MAP1LC3/LC3 (microtubule-associated protein 1 light chain 3) promotes apoptosis via fully activating both intrinsic and extrinsic mechanisms in CSFV-infected cells. We also found that RIG-I-like receptor (RLR) signaling was amplified in autophagy-deficient cells during CSFV infection, which was closely linked to the activation of the intrinsic apoptosis pathway. Moreover, we discovered that virus infection of autophagy-impaired cells results in an increase in copy number of mitochondrial DNA and in the production of reactive oxygen species (ROS), which plays a significant role in enhanced RLR signaling and the activated extrinsic apoptosis pathway in cultured cells. Collectively, these data indicate that CSFV-induced autophagy delays apoptosis by downregulating ROS-dependent RLR signaling and thus contributes to virus persistent infection in host cells.

Usp5 links suppression of p53 and FAS levels in melanoma to the BRAF pathway

Usp5 is a deubiquitinase (DUB) previously shown to regulate unanchored polyubiquitin (Ub) chains, p53 transcriptional activity and double-strand DNA repair. In BRAF mutant melanoma cells, Usp5 activity was suppressed by BRAF inhibitor (vemurafenib) in sensitive but not in acquired or intrinsically resistant cells. Usp5 knockdown overcame acquired vemurafenib resistance and sensitized BRAF and NRAS mutant melanoma cells to apoptosis initiated by MEK inhibitor, cytokines or DNA-damaging agents. Knockdown and overexpression studies demonstrated that Usp5 regulates p53 (and p73) levels and alters cell growth and cell cycle distribution associated with p21 induction. Usp5 also regulates the intrinsic apoptotic pathway by modulating p53-dependent FAS expression. A small molecule DUB inhibitor (EOAI3402143) phenocopied the FAS induction and apoptotic sensitization of Usp5 knockdown and fully blocked melanoma tumor growth in mice. Overall, our results demonstrate that BRAF activates Usp5 to suppress cell cycle checkpoint control and apoptosis by blocking p53 and FAS induction; all of which can be restored by small molecule-mediated Usp5 inhibition. These results suggest that Usp5 inhibition can provide an alternate approach in recovery of diminished p53 (or p73) function in melanoma and can add to the targeted therapies already used in the treatment of melanoma.

Type I interferons regulate eomesodermin expression and the development of unconventional memory CD8(+) T cells

CD8(+) T-cell memory phenotype and function are acquired after antigen-driven activation. Memory-like cells may also arise in absence of antigenic exposure in the thymus or in the periphery. Eomesodermin (Eomes) is a key transcription factor for the development of these unconventional memory cells. Herein, we show that type I interferon signalling in CD8(+) T cells directly activates Eomes gene expression. Consistent with this observation, the phenotype, function and age-dependent expansion of 'virtual memory' CD8(+) T cells are strongly affected in absence of type I interferon signalling. In addition, type I interferons induce a sustained expansion of 'virtual memory' CD8(+) T cells in an Eomes-dependent fashion. We further show that the development of 'innate thymic' CD8(+) T cells is dependent on the same pathway. In conclusion, we demonstrate that type I interferon signalling in CD8(+) T cells drives Eomes expression and thereby regulates the function and homeostasis of memory-like CD8(+) T cells.

Type I interferons in infectious disease

Type I interferons (IFNs) have diverse effects on innate and adaptive immune cells during infection with viruses, bacteria, parasites and fungi, directly and/or indirectly through the induction of other mediators. Type I IFNs are important for host defence against viruses. However, recently, they have been shown to cause immunopathology in some acute viral infections, such as influenza virus infection. Conversely, they can lead to immunosuppression during chronic viral infections, such as lymphocytic choriomeningitis virus infection. During bacterial infections, low levels of type I IFNs may be required at an early stage, to initiate cell-mediated immune responses. High concentrations of type I IFNs may block B cell responses or lead to the production of immunosuppressive molecules, and such concentrations also reduce the responsiveness of macrophages to activation by IFNγ, as has been shown for infections with Listeria monocytogenes and Mycobacterium tuberculosis. Recent studies in experimental models of tuberculosis have demonstrated that prostaglandin E2 and interleukin-1 inhibit type I IFN expression and its downstream effects, demonstrating that a cross-regulatory network of cytokines operates during infectious diseases to provide protection with minimum damage to the host.

Interferon regulatory factor 3 in adaptive immune responses

Interferon regulatory factor (IRF) 3 plays a key role in innate responses against viruses. Indeed, activation of this transcription factor triggers the expression of type I interferons and downstream interferon-stimulated genes in infected cells. Recent evidences indicate that this pathway also modulates adaptive immune responses. This review focuses on the different mechanisms that are implicated in this process. We discuss the role of IRF3 within antigen-presenting cells and T lymphocytes in the polarization of the cellular immune response and its implication in the pathogenesis of immune disorders.

Attenuation of pathogenic immune responses during infection with human and simian immunodeficiency virus (HIV/SIV) by the tetracycline derivative minocycline

HIV immune pathogenesis is postulated to involve two major mechanisms: 1) chronic innate immune responses that drive T cell activation and apoptosis and 2) induction of immune regulators that suppress T cell function and proliferation. Both arms are elevated chronically in lymphoid tissues of non-natural hosts, which ultimately develop AIDS. However, these mechanisms are not elevated chronically in natural hosts of SIV infection that avert immune pathogenesis despite similarly high viral loads. In this study we investigated whether minocycline could modulate these pathogenic antiviral responses in non-natural hosts of HIV and SIV. We found that minocycline attenuated in vitro induction of type I interferon (IFN) and the IFN-stimulated genes indoleamine 2,3-dioxygenase (IDO1) and TNF-related apoptosis inducing ligand (TRAIL) in human plasmacytoid dendritic cells and PBMCs exposed to aldrithiol-2 inactivated HIV or infectious influenza virus. Activation-induced TRAIL and expression of cytotoxic T-lymphocyte antigen 4 (CTLA-4) in isolated CD4+ T cells were also reduced by minocycline. Translation of these in vitro findings to in vivo effects, however, were mixed as minocycline significantly reduced markers of activation and activation-induced cell death (CD25, Fas, caspase-3) but did not affect expression of IFNβ or the IFN-stimulated genes IDO1, FasL, or Mx in the spleens of chronically SIV-infected pigtailed macaques. TRAIL expression, reflecting the mixed effects of minocycline on activation and type I IFN stimuli, was reduced by half, but this change was not significant. These results show that minocycline administered after infection may protect against aspects of activation-induced cell death during HIV/SIV immune disease, but that in vitro effects of minocycline on type I IFN responses are not recapitulated in a rapid progressor model in vivo.

Type I IFN signature in primary Sjögren's syndrome patients

Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease characterized by lymphocytic infiltrates in salivary and lacrimal glands. Clinical manifestations range from ocular and oral dryness to vasculitis and severe fatigue. pSS is a disease with heterogeneous symptoms and a variable response to the available treatment. Recently, a key role for Interferon (IFN) type I has been implicated in the pathogenesis of pSS. As type I IFN consists of 17 different subtypes, it cannot be easily assessed using a conventional ELISA. Therefore the expression of type I IFN inducible genes--the so-called type I IFN signature--is assessed in salivary gland tissue and blood from patients as a readout for type I IFN activity. In this review we discuss the potential of type I IFN as a novel biomarker for disease activity, subclassification of patients, prediction of therapy response and most importantly as a target for therapeutic intervention.

Type-I interferon is critical for FasL expression on lung cells to determine the severity of influenza

Infection of influenza A virus in mammals induces hyper lung pneumonia, which often causes lethal diseases. FasL is a specific ligand of Fas, which is a type-I transmembrane protein to induce cell death. Previously, it has been reported that the hyper induction of gene expression associated with Fas signal is observed in lethal influenza A virus infection. More importantly, it was also reported that functional mutation of the FasL gene protects the host against influenza A virus infection. These observations suggest that induction of FasL signal is functionally associated with the severity of influenza. However, regulation of the induction of FasL or Fas by influenza A virus infection is still unknown. Here, we demonstrated that FasL is induced after the viral infection, and inhibition of the Fas/FasL signal by treatment with a recombinant decoy receptor for FasL (Fas-Fc) increases the survival rate of mice after lethal infection of influenza A virus as well as functional mutation of the FasL gene in gld/gld mice. In addition, the induction level of FasL gene expression in the lung was correlated with the severity of influenza. We also showed that a variety of types of cells in the lung express FasL after the viral infection. Furthermore, type-I interferon induced by the viral infection was shown to be critical for induction of FasL protein expression in the lung. These findings suggested that expression of FasL protein induced by type-I IFN on the lung cell surface is critical to determine the severity of influenza.

CD4+ CD25+ Foxp3+ IFNγ+ CD178+ human induced Treg (iTreg) contribute to suppression of alloresponses by apoptosis of responder cells

Induced Treg with the phenotype CD4(+)CD25(+)Foxp3(+)IFNγ(+) were shown to be associated with good long-term graft outcome in renal transplant recipients and inhibition of allogeneic T-cell responses in vitro. In the present study, we investigated whether apoptosis and Fas/FasL-dependent pathways contribute to the inhibition of T-cell activation. Early apoptosis and necrosis rates as well as co-expression of immunostimulatory and immunosuppressive proteins in/on CD4(+)CD25(+)Foxp3(+), CD4(+)IFNγ(+)Foxp3(+) and CD4(+)CD25(+)IFNγ(+) PBL were analyzed using cells from healthy controls and four-color flow cytometry, PMA/Ionomycin-stimulated PBL, and MLC. Sixteen hours PMA/Ionomycin stimulation induced iTreg subsets with the phenotype CD4(+)CD25(+)Foxp3(+), CD4(+)IFNγ(+)Foxp3(+) and CD4(+)CD25(+)IFNγ(+) co-expressing CD95, CD152, CD178, CD279, Granzyme A, Granzyme B, Perforin, IL-10, and TGFβ(1). CD178(+) iTreg increased within 3h after PMA/Ionomycin stimulation in parallel to early apoptotic Annexin(+)/PI(-) PBL, suggesting CD178-mediated apoptosis of responder cells by CD4(+)CD25(+)Foxp3(+)IFNγ(+)CD178(+) iTreg. CD4(+)CD25(+)IFNγ(+) and CD4(+)CD25(+)CD178(+) PBL separated from primary cell cultures and added to autologous PMA/Ionomycin stimulated secondary cell cultures induced apoptosis immediately. Early apoptosis was not antigen-specific as shown in secondary MLC with separated CD4(+)CD25(+)IFNγ(+) and CD4(+)CD25(+)CD178(+) PBL and third-party cells as stimulator. CD4(+)CD25(+)Foxp3(+)IFNγ(+)CD178(+) iTreg differentiate after cell stimulation and induce antigen-unspecific apoptosis of activated CD95(+) responder/effector cells in vitro that might contribute to iTreg-mediated inhibition of T-cell activation.

Pathogen-induced proapoptotic phenotype and high CD95 (Fas) expression accompany a suboptimal CD8+ T-cell response: reversal by adenoviral vaccine

MHC class Ia-restricted CD8⁺ T cells are important mediators of the adaptive immune response against infections caused by intracellular microorganisms. Whereas antigen-specific effector CD8⁺ T cells can clear infection caused by intracellular pathogens, in some circumstances, the immune response is suboptimal and the microorganisms survive, causing host death or chronic infection. Here, we explored the cellular and molecular mechanisms that could explain why CD8⁺ T cell-mediated immunity during infection with the human protozoan parasite Trypanosoma cruzi is not optimal. For that purpose, we compared the CD8⁺ T-cell mediated immune responses in mice infected with T. cruzi or vaccinated with a recombinant adenovirus expressing an immunodominant parasite antigen. Several functional and phenotypic characteristics of specific CD8⁺ T cells overlapped. Among few exceptions was an accelerated expansion of the immune response in adenoviral vaccinated mice when compared to infected ones. Also, there was an upregulated expression of the apoptotic-signaling receptor CD95 on the surface of specific T cells from infected mice, which was not observed in the case of adenoviral-vaccinated mice. Most importantly, adenoviral vaccine provided at the time of infection significantly reduced the upregulation of CD95 expression and the proapoptotic phenotype of pathogen-specific CD8⁺ cells expanded during infection. In parallel, infected adenovirus-vaccinated mice had a stronger CD8 T-cell mediated immune response and survived an otherwise lethal infection. We concluded that a suboptimal CD8⁺ T-cell response is associated with an upregulation of CD95 expression and a proapoptotic phenotype. Both can be blocked by adenoviral vaccination.

Killer lymphocytes are important mediators of the immunological resistance against infections caused by virus, bacteria and parasites. In some circumstances, however, these lymphocytes are unable to properly eliminate the microorganisms which survive, causing death or establishing chronic infections. The purpose of our study was to understand why these killer cells do not succeed during infection with a human protozoan parasite. For that purpose, we compared the immune responses in animals infected or vaccinated. Many characteristics of these killer cells were similar. Among few exceptions was an accelerated immune response in vaccinated animals when compared to infected ones. Also, we observed on the surface of the killer lymphocytes from infected, but not from vaccinated animals, an increased expression of a protein involved in signaling cell death. Most importantly, vaccine significantly reduced the higher expression of this cell-death receptor. In parallel, these animals had a stronger immune response and cured infection. We concluded that a deficient killer cell response observed during infection was associated with an upregulation of this cell-death receptor and it was changed by vaccination.

Altered thymic function during interferon therapy in HCV-infected patients

Interferon alpha (IFNα) therapy, despite good efficacy in curing HCV infection, leads to major side effects, in particular inducement of a strong peripheral T-cell lymphocytopenia. We here analyze the early consequences of IFNα therapy on both thymic function and peripheral T-cell homeostasis in patients in the acute or chronic phase of HCV-infection as well as in HIV/HCV co-infected patients. The evolution of T-cell subsets and T-cell homeostasis were estimated by flow cytometry while thymic function was measured through quantification of T-cell receptor excision circles (TREC) and estimation of intrathymic precursor T-cell proliferation during the first four months following the initiation of IFNα therapy. Beginning with the first month of therapy, a profound lymphocytopenia was observed for all T-cell subsets, including naïve T-cells and recent thymic emigrants (RTE), associated with inhibition of intrathymic precursor T-cell proliferation. Interleukin (IL)-7 plasma concentration rapidly dropped while lymphocytopenia progressed. This was neither a consequence of higher consumption of the cytokine nor due to its neutralization by soluble CD127. Decrease in IL-7 plasma concentration under IFNα therapy correlated with the decline in HCV viral load, thymic activity and RTE concentration in blood. These data demonstrate that IFNα-based therapy rapidly impacts on thymopoiesis and, consequently, perturbs T-cell homeostasis. Such a side effect might be detrimental for the continuation of IFNα therapy and may lead to an increased level of infectious risk, in particular in HIV/HCV co-infected patients. Altogether, this study suggests the therapeutic potential of IL-7 in the maintenance of peripheral T-cell homeostasis in IFNα-treated patients.

Modulation of T-cell function by type I interferon

Production of type I interferon (IFN-α/β) is a common cellular response to virus infection. IFN-α/β has a dual role in combating infection, triggering innate antiviral mechanisms and stimulating the generation of an adaptive immune response. This review focuses on the effects of IFN-α/β on one particular immune cell type, the T cell, and the impact of IFN-α/β-mediated signalling in T cells on the immune response. The critical role of T-cell responsiveness to IFN-α/β for the generation of productive T-cell responses after infections with certain viruses in vivo is discussed in the context of in vitro experiments investigating the mechanisms by which IFN-α/β modifies T-cell function. These studies reveal complex effects of IFN-α/β on T cells, with the consequences of exposure to IFN-α/β depending on the context of other signals received by the T cell.

Anchoring interferon alpha to apolipoprotein A-I reduces hematological toxicity while enhancing immunostimulatory properties

Interferon alpha (IFNα) is widely used for the treatment of viral hepatitis but substantial toxicity hampers its clinical use. In this work, we aimed at improving the efficacy of IFNα therapy by increasing the IFNα half-life and providing liver tropism. We selected apolipoprotein A-I (ApoA-I) as the stabilizing and targeting moiety. We generated plasmids encoding IFNα, albumin bound to IFNα (ALF), or IFNα linked to ApoA-I (IA) and mice were treated either by hydrodynamic administration of the plasmids or by injection of the corresponding recombinant proteins or high-density lipoproteins containing IA. The plasma half-life of IA was intermediate between IFNα and ALF. IA was targeted to the liver and induced higher hepatic expression of interferon-stimulated genes than IFNα or even ALF. IA exhibits stronger in vivo antiviral activity than IFNα and the hematologic cytopenic effects of IA are milder than those observed when using IFNα or ALF. In contrast to IFNα, IA does not cause activation-dependent cell death of lymphocytes in vitro. Accordingly, in vivo studies showed that IA boosts T-cell immune responses more efficiently than IFNα or ALF. The difference in immunostimulatory activity between IFNα and IA disappears in scavenger receptor class B type I (SR-BI) knockout mice, suggesting that crosstalk between SR-BI and IFNα receptor is essential for enhanced induction of cytotoxic T cells by IA.

CONCLUSION

Anchoring IFNα to ApoA-I prolongs the half-life of IFNα and promotes targeting to the liver. Importantly, the fusion protein shows increased immunostimulatory properties and lower hematological toxicity.

Inflammatory cytokines determine the susceptibility of human CD8 T cells to Fas-mediated activation-induced cell death through modulation of FasL and c-FLIP(S) expression

The nature of inflammatory signals determines the outcome of T cell responses. However, little is known about how inflammatory cytokines provided to human CD8 T cells during activation affects their susceptibility to post-activation cell death. We have examined and compared the effects of the inflammatory cytokine IL-12, as well as the combination of IL-1, IL-6, and IL-23 (IL-1/6/23) on the susceptibility of primary human CD8 T cells to post-activation cell death. Human CD8 T cells activated in the presence of IL-1/6/23 underwent significantly less cell death after activation as compared with those activated in IL-12. This was due to reduced susceptibility to Fas-mediated activation-induced cell death (AICD). Mechanistically, the reduced level of cell death in CD8 T cells activated in IL-1/6/23 was a result of a low level of FasL expression and high level of c-FLIP(S) expression. When the effect of IL-1, IL-6, and IL-23 individually was examined, IL-1 or IL-6 alone was sufficient to inhibit CD8 T cell death that occurs after activation in IL-12. IL-1, but not IL-6, inhibited expression of FasL, whereas IL-6, but not IL-1, increased c-FLIP(S) expression. Our findings show that the presence of IL-1 and/or IL-6 during activation of human CD8 T cells attenuates Fas-mediated AICD, whereas IL-12 increases the susceptibility of activated CD8 T cells to this form of cell death.

Effects of IFN-α as a signal-3 cytokine on human naïve and antigen-experienced CD8(+) T cells

IFN-α/β link innate and adaptive immune responses by directly acting on naïve CD8(+) T cells. This concept unveiled in mice remains unexplored in humans. To investigate that, human CD8(+) CD45RO(-) cells were stimulated with beads coated with anti-CD3 and anti-CD28 mAb, mimicking Ag (type-1) and co-stimulatory (type-2) signals, in the presence or absence of IFN-α and their transcriptional profiles were defined by cDNA-microarrays. We show that IFN-α provides a strong third signal directly to human CD8(+) T cells resulting in regulation of critical genes for their overall activation. This transcriptional effect was substantiated at the protein level and verified by functional assays. Interestingly, the biological effects derived from this stimulation vary depending on the CD8(+) T-cell population. Thus, whereas IFN-α increases the proliferative capacity of naïve CD8(+) T cells, it inhibits or does not affect the proliferation of Ag-experienced cells, such as memory and effector CTL, including CMV-specific lymphocytes. Cytolysis and IFN-γ-secretion of all these populations are enhanced by IFN-α-derived signals, which are critical in naïve CD8(+) T cells for acquisition of effector functions. Our findings in human CD8(+) T cells are informative to understand and improve IFN-α-based therapies for viral and malignant diseases.

Type I interferon modulates the battle of host immune system against viruses

Type I interferon (IFN), as its name implies, 'interferes' with virus replication by activating numerous genes. Further, virus-induced type I IFN regulates the magnitude and functions of cells directing the host immune system. Importantly, recent exploration into how type I IFN operates following virus infection has advanced our understanding of its role with respect to modulation of host innate and adaptive immune responses. Such activities include the activation of antigen-presenting dendritic cells and the localization, expansion or differentiation of virus-specific T lymphocytes and antibody-producing B lymphocytes. However, type I IFN not only benefits the host but can also induce unnecessary or extremely pathogenic immune responses. This review focuses on such interactions and the manner in which type I IFN induces dynamic changes in the host immune network, particularly adaptive immune responses to viral invasion. Manipulating the type I IFN-mediated host immune response during virus infections could provide new immunotherapeutic interventions to remedy viral diseases and implement more effective and sustainable type I IFN therapy.

Effects of interferon-alpha on thymidine phosphorylase expression and apoptosis in human hepatocellular carcinoma SMMC-7721 cells

AIM: To investigate the effects of interferon-alpha (IFN-α) on thymidine phosphorylase (TP) expression and apoptosis in human hepatocellular carcinoma SMMC-7721 cells.

METHODS: The expression of TP mRNA was detected by reverse transcription-polymerase chain reaction (RT-PCR). The expression of TP protein was evaluated by immunocytochemistry. The percentage of apoptotic cells was measured by flow cytometry.

RESULTS: IFN-α upregulated the expression of TP mRNA in a dose-dependent manner in SMMC-7721 cells. IFN-α at a dose of 5000 or 10 000 kU/L induced a 3-fold upregulation of TP mRNA compared to non-treated cells (P < 0.05). Compared with non-treated cells, the intensity of TP staining and the number of TP-positive cells significantly increased in IFN-α treated cells (5000 or 10 000 kU/L). However, no significant difference was found in the percentage of apoptotic cells between IFN-α (10 000 kU/L)-treated cells and non-treated cells (6.42% ± 3.66% vs 7.19% ± 2.76%, P > 0.05).

CONCLUSION: IFN-α at appropriate doses may upregulate the expression of TP mRNA and protein and antagonize TP-induced inhibition of apoptosis in human hepatocellular carcinoma cells.

Clinical and immunologic effects of intranodal autologous tumor lysate-dendritic cell vaccine with Aldesleukin (Interleukin 2) and IFN-{alpha}2a therapy in metastatic renal cell carcinoma patients

PURPOSE

To evaluate the clinical and immunologic outcomes of DC (dendritic cell) vaccine with interleukin (IL)-2 and IFN-alpha 2a in metastatic renal cell carcinoma patients.

EXPERIMENTAL DESIGN

Eighteen consented and eligible patients were treated. Peripheral blood monocytes were cultured ex vivo into mature DCs and loaded with autologous tumor lysate. Treatment consisted of five cycles of intranodal vaccination of DCs (1 x 10(7) cells/1 mL Lactated Ringer's solution), 5-day continuous i.v. infusion of IL-2 (18MiU/m2), and three s.c. injections of IFN-alpha 2a (6MiU) every other day. Response Evaluation Criteria in Solid Tumors criteria were used for disease assessment. Correlative immunologic end points included peripheral blood lymphocyte cell phenotype and function as well as peripheral blood anti-renal cell carcinoma antibody and cytokine levels.

RESULTS

All patients received between two and five treatment cycles. Toxicities consisted of known and expected cytokine side effects. Overall objective clinical response rate was 50% with three complete responses. Median time to progression for all patients was 8 months, and median survival has not been reached (median follow up of 37+ months). Treatment-related changes in correlative immunologic end points were noted and the level of circulating CD4(+) T regulatory cells had a strong association with outcome. Pre-IP-10 serum levels approached significance for predicting outcome.

CONCLUSIONS

The clinical and immunologic responses observed in this trial suggest an interaction between DC vaccination and cytokine therapy. Our data support the hypothesis that modulation of inflammatory, regulatory, and angiogenic pathways are necessary to optimize therapeutic benefit in renal cell carcinoma patients. Further exploration of this approach is warranted.

Apoptosis of murine lupus T cells induced by the selective cyclooxygenase-2 inhibitor celecoxib: Molecular mechanisms and therapeutic potential

Upregulation of cyclooxygenase (COX)-2 in T cells from patients with systemic lupus erythematosus (SLE) is associated with their resistance to functional inactivation (anergy) and to activation-induced cell death through apoptosis. It has been demonstrated that celecoxib, a selective COX-2 inhibitor, can enhance apoptosis of human lupus T cells. The present study was undertaken to investigate whether COX-2 expression is also upregulated in T cells from the lupus-prone BXBS strain of mice and if murine lupus is modified by celecoxib. COX-2 expression was detected in splenic T cells from 6 month-old male BXSB mice (murine lupus T cells) but not in T cells from 2 month-old male or 6-month-old female BXSB or in 6-month-old male C57BL/6 mice, indicating a strong correlation between COX-2 expression in T cells and lupus manifestation in mice. Celecoxib treatment induced apoptosis of murine lupus T cells in vitro, which was inhibited by z-VAD-fmk, a pan-caspase inhibitor. In the murine lupus T cells treated with celecoxib, procaspases 3 and 9, but not procaspase 8, were activated. In addition, celecoxib treatment decreased the mitochondrial membrane potential of murine lupus T cells. These data combine to suggest that celecoxib mainly uses the mitochondrial pathway rather than FADD pathway to trigger apoptosis of COX-2 expressing murine lupus T cells. Intragastric administration of celecoxib (40 mg/kg/day for 60 days) in 6-month-old male BXSB mice effectively limited the production of serum antibodies against dsDNA. Our data suggest that celecoxib may have a beneficial effect in treating autoimmune diseases such as SLE through inducing apoptosis of autoreactive T cells.

Human CD5 protects circulating tumor antigen-specific CTL from tumor-mediated activation-induced cell death

We previously characterized several tumor-specific T cell clones from PBL and tumor-infiltrating lymphocytes of a lung cancer patient with identical TCR rearrangements and similar lytic potential, but with different antitumor response. A role of the TCR inhibitory molecule CD5 to impair reactivity of peripheral T cells against the tumor was found to be involved in this process. In this report, we demonstrate that CD5 also controls the susceptibility of specific T cells to activation-induced cell death (AICD) triggered by the tumor. Using a panel of tumor-infiltrating lymphocytes and PBL-derived clones expressing different levels of CD5, our results indicate that T lymphocyte AICD in response to the cognate tumor is inversely proportional to the surface expression level of CD5. They also suggest a direct involvement of CD5 in this process, as revealed by an increase in tumor-mediated T lymphocyte AICD following neutralization of the molecule with specific mAb. Mechanistically, our data indicate that down-regulation of FasL expression and subsequent inhibition of caspase-8 activation are involved in CD5-induced T cell survival. These results provide evidence for a role of CD5 in the fate of peripheral tumor-specific T cells and further suggest its contribution to regulate the extension of CTL response against tumor.

HIV-1 immunopathogenesis: how good interferon turns bad

The hallmark of acquired immunodeficiency syndrome (AIDS) is the progressive loss of CD4+ T cells that results from infection with human immunodeficiency virus type-1 (HIV-1). Despite 25 years of AIDS research, questions remain concerning the mechanisms responsible for HIV-induced CD4+ T cell depletion. Here we briefly review the in vitro and in vivo literature concerning the protective role of interferon-alpha (IFN-alpha) in HIV/AIDS. We then develop a laboratory- and clinically supported model of CD4+ T cell apoptosis in which either infectious or noninfectious HIV-1 induces the production of type I interferon by plasmacytoid dendritic cells (pDC). The interferon produced binds to its receptor on primary CD4+ T cells resulting in membrane expression of the TNF-related apoptosis-inducing ligand (TRAIL) death molecule. The binding of infectious or noninfectious HIV-1 to CD4 on these T cells results in expression of the TRAIL death receptor 5 (DR5), leading to the selective death of HIV-exposed CD4+ T cells.

Immune dysfunction in inflammatory bowel disease

Ulcerative colitis (UC) and Crohn's disease (CD) are idiopathic inflammatory bowel diseases (IBDs) that are characterized by chronic periods of exacerbation and remission. Research into the immunopathogenesis of IBD adds support to the theory that the disease results from a dysfunctional regulation of the immune system that leads to the polarization of intestinal immune cells toward a Th1 (T helper) response. The immunologic factors that mediate alterations in intestinal homeostasis and the development of intestinal mucosal inflammation have been at the forefront of IBD research. Cytokines, which are important regulators of leukocyte trafficking and apoptotic cell death, have emerged as essential immune molecules in the pathogenesis of IBD. In this study, recent advances in the understanding of the dynamism of cytokines and the consequences for mucosal immunity and inflammation in IBD are discussed. Furthermore, this study highlights the potential use of cytokines, anti-cytokine antibodies, and cytokine-related biologic therapies as novel targets for the treatment of IBD.

Role of the Fas/FasL pathway in combination therapy with interferon-alpha and fluorouracil against hepatocellular carcinoma in vitro

BACKGROUND/AIMS

Several studies have reported the efficacy of combination therapy of interferon (IFN) alpha and 5-fluorouracil (5-FU) for hepatocellular carcinoma (HCC). However, the mechanism underlying the clinical anti-tumor effects of this treatment is not well understood. The aim of this study was to determine the role of Fas/FasL signaling in the anti-tumor effect of this combination therapy.

METHODS AND RESULTS

We used six human hepatoma cell lines, three of which are known Fas-expressing cells. Growth of Fas-positive hepatoma cell lines was inhibited by an agonistic anti-Fas antibody in a dose-dependent manner, and these effects were enhanced by IFNalpha or 5-FU alone, but even more so by combination therapy using both agents. Annexin-V assay implicated apoptosis as the main mechanism underlying these growth inhibitory effects, although changes in Fas expression regulated by IFNalpha and/or 5-FU did not correlate with increased apoptosis. Caspase-3 activation was exclusively increased by IFNalpha/5-FU combination treatment, which was compatible with enhancement of the synergistic apoptotic effect, and other caspases and apoptotic factors (FLIP, BCL-xl, and Bax) were also regulated by IFNalpha/5-FU. 51Cr-release assay revealed that pretreatment with IFN activated cytotoxicity of peripheral blood mononuclear cells (PBMCs) against HCC cells. The largest interaction was observed when both PBMC and HCC cells were pretreated with the combination of IFNalpha/5-FU. These cytotoxicities were markedly inhibited by a neutralizing anti-Fas antibody.

CONCLUSIONS

Our results indicated that IFNalpha/5-FU combination treatment enhances the induction of apoptosis and the cytotoxic effect of PBMCs via the Fas/FasL pathway. The Fas/FasL pathway seems, at least in part, to contribute to the anti-tumor effects of IFNalpha/5-FU against HCCs.

Variation in the type I interferon gene cluster on 9p21 influences susceptibility to asthma and atopy

A genome-wide screen for asthma and atopy susceptibility alleles conducted in the Hutterites, a founder population of European descent, reported evidence of linkage with a short tandem repeat polymorphism (STRP) within the type I interferon (IFN) gene cluster on chromosome 9p21. The goal of this study was to identify variation within the IFN gene cluster that influences susceptibility to asthma and atopic phenotypes. We screened approximately 25 kb of sequence, including the flanking sequence of all 15 functional genes and the single coding exon in 12, in Hutterites representing different IFNA-STRP genotypes. We identified 78 polymorphisms, and genotyped 40 of these (in 14 genes) in a large Hutterite pedigree. Modest associations (0.003<P<0.05) with asthma, bronchial hyper-responsiveness (BHR), and atopy were observed with individual variants or genes, spanning the entire 400 kb region. However, pairwise combinations of haplotypes between genes showed highly significant associations with different phenotypes (P<10(-5)) that were localized to specific pairs of genes or regions of this cluster. These results suggest that variation in multiple genes in the type I IFN cluster on 9p22 contribute to asthma and atopy susceptibility, and that not all genes contribute equally to all phenotypes.

CD8 T cells specific for lymphocytic choriomeningitis virus require type I IFN receptor for clonal expansion

The role of type I IFN signaling in CD8 T cells was analyzed in an adoptive transfer model using P14 TCR transgenic CD8 T cells specific for lymphocytic choriomeningitis virus (LCMV) but deficient in type I IFNR. In the present study, we demonstrate severe impairment in the capacity of P14 T cells lacking type I IFNR to expand in normal type I IFNR wild-type C57BL/6 hosts after LCMV infection. In contrast, following infection of recipient mice with recombinant vaccinia virus expressing LCMV glycoprotein, P14 T cell expansion was considerably less dependent on type I IFNR expression. Lack of type I IFNR expression by P14 T cells did not affect cell division after LCMV infection but interfered with clonal expansion. Thus, direct type I IFN signaling is essential for CD8 T cell survival in certain viral infections.

Direct Stimulation of T Cells by Type I IFN Enhances the CD8+T Cell Response during Cross-Priming

Type I IFN (IFN-alphabeta), which is produced rapidly in response to infection, plays a key role in innate immunity and also acts as a stimulus for the adaptive immune response. We have investigated how IFN-alphabeta induces cross-priming, comparing CD8+ T cell responses generated against soluble protein Ags in the presence or absence of IFN-alphabeta. Injection of IFN-alpha was found to prolong the proliferation and expansion of Ag-specific CD8+ T cells, which was associated with marked up-regulation of IL-2 and IL-15 receptors on Ag-specific cells and expression of IL-15 in the draining lymph node. Surprisingly, neither IL-2 nor IL-15 was required for IFN-alpha-induced cross-priming. Conversely, expression of the IFN-alphabetaR by T cells was shown to be necessary for effective stimulation of the response by IFN-alpha. The finding that T cells represent direct targets of IFN-alphabeta-mediated stimulation reveals an additional mechanism by which the innate response to infection promotes adaptive immunity.

Modifications of T-lymphocyte subsets before and during interferon and ribavirin treatment for chronic hepatitis C infection

Our purpose was to determine in HCV-infected patients whether T-lymphocyte sub-populations were modified before and during interferon-alpha and ribavirin treatment, and whether this correlated with virological response. Twenty-two naive patients were given IFN-alpha 3 Million Units three times per week for 24 or 48 weeks and ribavirin. Sustained virological response corresponded to undetectable serum HCV RNA at treatment completion and 6 months later. Total blood lymphocyte counts and CD3(+)CD4(+), CD3(+)CD8(+), CD3(+)CD4(+)HLA-DR(+), and CD3(+)CD8(+)HLA-DR(+) lymphocyte subsets evaluated before, during, and after treatment were compared to values from 37 healthy subjects. At inclusion, patients and controls had similar total lymphocyte counts. CD3(+)CD4(+) counts and percentages were significantly higher in HCV patients. HLA-DR expression was also increased in CD4(+) (p < 0.0001) and CD8(+) T-cells (p = 0.0008) as compared with controls. During treatment, all lymphocyte subset counts and percentage decreased except the CD3(+)CD4(+) T-cell percentage which increased. Moreover, after 1 month of treatment, virological responders exhibited higher CD4(+) counts than nonresponders (p = 0.025), whereas they did not differ at inclusion or during the 2nd to 6th months of treatment. After treatment completion, all populations returned to baseline values. These results suggest that CD3(+)CD4(+) T-lymphocyte percentage increase under treatment could be related to IFN immunomodulation and associated with virological response.

Immunomodulatory effects of selective leucocytapheresis as a new adjunct to interferon-alpha2b plus ribavirin combination therapy: a prospective study in patients with high plasma HCV viraemia

Efficacy of interferon-alpha2b (IFN) + ribavirin (IFN/RBV) combination in patients with high plasma hepatitis C virus (HCV) is very poor. Dysregulated CD4+ /CD8+ T cells is involved in both impaired cell-mediated immunity and resistance to IFN. Adsorptive granulocytes and monocytes apheresis (GMA) can remove infected leucocytes which are extrahepatic HCV reservoirs and also has been associated with intriguing immunomodulation and increases in CD4+ T cells. Our aim was to see if GMA enhances the efficacy of IFN/RBV. Twenty-four patients, 13 IFN resistant and 11 IFN naive were enrolled. Seventeen were genotype 1b and 7 were 2a or 2b. Mean plasma HCV-RNA was 612.9 (100-850) kIU/mL and alanine aminotransferase, 108 (41-373) U/L. GMA was performed with Adacolumn at one session/day for five consecutive days and IFN/RBV was started within 24 h after the last GMA session. Daily 6 million units of IFN, six times/week for 2 weeks and then three times/week for 22 weeks were given with RBV (600-800 mg/day/patient). Patients were followed for 6 months. GMA was associated with a significant increase in lymphocyte counts, complement activation fragment C3a and falls in tissue necrosis factor-alpha, and IL-8 produced by peripheral blood leucocytes. At week 24, 20 of 24 patients (83%) were HCV negative and by end of follow-up (week 49), the remission was sustained in 14 of 24 patients (58%) including 100% of patients with 2a or 2b. In conclusion, enhanced efficacy of IFN/RBV following GMA might be attributed to a more efficient immune function and a renewed IFN signaling towards HCV.

Role of Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand in Interferon-Induced Apoptosis in Human Bladder Cancer Cells

Immunomodulators such as Bacillus Calmette-Guerin and interferon are clinically active in transitional cell carcinoma of the bladder, but their mechanisms of action remain unclear. Here we investigated the effects of IFNalpha on tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) expression and apoptosis in a panel of 20 human bladder cancer cell lines. Six (30%) displayed significant DNA fragmentation in response to increasing concentrations of IFNalpha (10-100,000 units/mL). In these lines IFNalpha induced early activation of caspase-8, and DNA fragmentation was blocked by a caspase-8-selective inhibitor (IETDfmk), consistent with the involvement of death receptor(s) in cell death. IFNalpha stimulated marked increases in TRAIL mRNA and protein in the majority of IFN-sensitive and IFN-resistant cell lines. A blocking anti-TRAIL antibody significantly inhibited IFN-induced DNA fragmentation in four of six IFN-sensitive cell lines, confirming that TRAIL played a direct role in cell death. Bortezomib (PS-341, Velcade), a potent TRAIL-sensitizing agent, increased sensitivity to IFNalpha in two of the IFN-resistant cell lines that produced large amounts of TRAIL in response to IFN treatment. Our data show that IFN-induced apoptosis in bladder cancer cells frequently involves autocrine TRAIL production. Combination therapy strategies aimed at overcoming TRAIL resistance may be very effective in restoring IFN sensitivity in a subset of human bladder tumors.

A dual role of IFN-alpha in the balance between proliferation and death of human CD4+ T lymphocytes during primary response

Type I IFNs (IFN-alphabeta) enhance immune responses, notably T cell-mediated responses, in part by promoting the functional activities of dendritic cells. In this study, we analyzed the direct impact of IFN-alpha on proliferative and apoptotic signals upon in vitro activation of human naive CD4+ T lymphocytes. We demonstrate that IFN-alpha protects T cells from the intrinsic mitochondrial-dependent apoptosis early upon TCR/CD28 activation. IFN-alpha acts by delaying entry of cells into the G1 phase of the cell cycle, as well as by increasing Bcl-2 and limiting Bax activation. Later, upon activation, T cells that were exposed to IFN-alpha showed increased levels of surface Fas associated with partially processed caspase-8, a key component of the extrinsic apoptotic pathway. Caspase-8 processing was augmented furthermore by Fas ligation. Overall, these findings support a model whereby IFN-alpha favors an enhanced clonal expansion, yet it sensitizes cells to the Ag-induced cell death occurring at the end of an immune response. These observations point to a complex role of type I IFN in regulating the magnitude of proliferation and survival of naive CD4+ T cells during primary response and underline how crucial could be the timing of exposure to this cytokine.

Type I interferons and their therapeutic role in Th2-regulated inflammatory disorders

Cytokines are pleiotropic molecules showing a wide variety of biological functions on various cells and tissues. Several different cytokines exert similar and overlapping functions on certain cells. Interferons (IFNs) play a crucial role in human disease and consist of type I IFNs (IFN-alpha and IFN-beta) and type II IFN (IFN-gamma). The importance of type I IFNs in inflammation, immunoregulation and T cell responses has been recognised, and dendritic cells have recently been identified as the major source of type I IFNs. Type I IFNs are multifunctional immunomodulatory cytokines with profound effects on the cytokine cascade, including several anti-inflammatory properties. They favour both the induction of T helper (Th) 1 cytokines as well as the suppression of Th2 cytokines such as IL-13. Therefore, it is not unexpected that type I IFNs show promising clinical effects in Th2-dominated diseases such as ulcerative colitis and allergic asthma. These newly identified immunoregulatory and anti-inflammatory functions of type I IFNs may be of importance in the treatment of various chronic inflammatory disorders.

Increased production of TGF-beta and apoptosis of T lymphocytes isolated from peripheral blood in COPD

Chronic obstructive pulmonary disease (COPD) is associated with inflammation of airway epithelium, including an increase in the number of intraepithelial T cells. Increased apoptosis of these T cells has been reported in the airways in COPD, and although this process is critical for clearing excess activated T cells, excessive rates of apoptosis may result in unbalanced cellular homeostasis, defective clearance of apoptotic material by monocytes/macrophages, secondary necrosis, and prolongation of the inflammatory response. Lymphocytes are known to traffic between the airway and the peripheral circulation, thus we hypothesized that in COPD, circulating T cells may show an increased propensity to undergo apoptosis. We analyzed phytohemagglutinin (PHA)-stimulated peripheral blood T cells from COPD patients and controls for apoptosis using flow cytometry and staining with annexin V and 7-aminoactinomycin D. As several pathways are involved in induction of apoptosis of T cells, including transforming growth factor (TGF)-beta/TGF receptor (TGFR), TNF-alpha/TNFR1, and Fas/Fas ligand, these mediators were also investigated in peripheral blood samples from these subject groups. Significantly increased apoptosis of PHA-stimulated T cells was observed in COPD (annexin positive 75.0 +/- 14.7% SD vs. control 50.2 +/- 21.8% SD, P = 0.006), along with upregulation of TNF-alpha/TNFR1, Fas, and TGFR. Monocyte production of TGF-beta was also increased. In conclusion we have demonstrated the novel finding of increased apoptosis of stimulated T cells in COPD and have also shown that the increased T-cell death may be associated with upregulation of apoptotic pathways, TGF-beta, TNF-alpha, and Fas in the peripheral blood in COPD.