Enhanced Th17 differentiation and aggravated arthritis in IEX-1-deficient mice by mitochondrial reactive oxygen species-mediated signaling

CD4(+) Th1 and Th17 cells both can cause autoimmune diseases, either alone or collaboratively, if left unchecked. However, what determines the dominant Th effector phenotype in a specific autoimmune disease remains poorly understood. Our present investigation shows that null mutation of IEX-1 promotes differentiation of Th17 cells but compromises the survival of Th1 cells. The differential effect gave rise to a greater number of Th17 cells, a higher level of IL-17 production, and more severe arthritis in IEX-1 knockout mice than in wild-type mice after immunizations with collagen. IEX-1 deficiency-facilitated Th17 cell differentiation was mediated by the increased formation of reactive oxygen species (ROS) at mitochondria following T cell activation, as suggested by marked inhibition of Th17 induction with ROS scavenger N-acetylcysteine or mitoquinone, a specific inhibitor for mitochondrial ROS production. Mitochondrial ROS augmented the expression of B cell-activating transcription factor, which may contribute to increased IL-17 production in the absence of IEX-1, in light of its importance in IL-17 transcription. The results demonstrate that mitochondrial ROS contribute significantly to the dominant Th effector phenotype in autoimmunity in addition to the cytokine milieu.

Resistance of Sézary cells to TNF-α-induced apoptosis is mediated in part by a loss of TNFR1 and a high level of the IER3 expression

Failure to execute an apoptotic programme is one of the critical steps and a common mechanism promoting tumorogenesis. Immediate early responsive gene 3 (IER3) has been shown to be upregulated in several cancers. IER3 is a stress-induced gene, which upregulation leads to reduction in production of reactive oxygen species (ROS) protecting malignant cells from apoptosis. We observed that malignant lymphocytes from patients with Sézary syndrome (SzS) were resistant to pro-apoptotic dose of tumour necrosis factor-α (TNF-α). The aim of this study was to investigate the role of IER3 in the mechanism of such resistance. CD4+ CD26- lymphocytes from the peripheral blood of patients with SzS and healthy controls were negatively selected using CD4 and CD26 magnetic beads and analysed for expression of TNFR1, TNFR2, IER3 expression, and ROS production in response to TNF-α at an apoptotic dose. Sézary cells with a higher level of IER3 expression retained their viability to TNF-α. IER3 upregulation correlated with a decrease level of intracellular ROS and low TNFR1 expression on malignant cells. Targeting IER3 could be of interest for the development of future therapeutic strategies for patients with SzS.

Immediate early response gene X-1, a potential prognostic biomarker in cancers

INTRODUCTION

The immediate early response gene X-1 (IEX-1) plays a pivotal role in the regulation of cell apoptosis, proliferation, differentiation and metabolism. Deregulation of IEX-1 expression has been confirmed in multiple cancers in humans, in association with either poor or better prognosis depending on the type and progression stages of the cancer.

AREAS COVERED

This review summarizes clinical studies of altered IEX-1 expression in ovarian, pancreatic, blood, breast and colorectal cancers, lymphoma and myeloma. The authors also outline the current understandings of the complex functions of IEX-1 gained from studies with animal models and tumor cell lines so as to help us comprehend the significance of the clinical findings.

EXPERT OPINION

IEX-1 holds great promise to be a valuable biomarker, either alone or in combination with other genes, for monitoring progression of some cancers. IEX-1 expression is highly sensitive to environmental cues and distinct between normal and cancer cells. However, use of IEX-1 as a biomarker remains a significant challenge because too little is understood about the mechanism underlying the diverse activities of IEX-1 and a standardized clinical assay for IEX-1 detection and validation of clinical results across different studies are still critically lacking.

3,4-Dichloropropionaniline Suppresses Normal Macrophage Function

Macrophages are a critical part of the innate immune response and natural surveillance mechanisms. As such, proper macrophage function is crucial for engulfing bacterial pathogens through phagocytosis and destroying them by generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). The production of a number of cytokines by macrophages, such as tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-6, plays an important role in the initiation of the acquired immune response creating an inflammatory environment favorable for fighting a bacterial infection. 3,4-Dichloropropionaniline (DCPA) suppresses several inflammatory parameters, including TNF-alpha production through a mechanism where nuclear factor-kappaB (NF-kappaB)-DNA binding is inhibited but not entirely abrogated. The goal of the present study was to evaluate the effects of DCPA on the inflammatory mediators of macrophages, including ROS and RNS in both murine peritoneal exudate cells and the human monocytic cell line, THP-1. The ability to perform phagocytosis and directly kill Listeria monocytogenes was also assessed. The results indicate that DCPA decreases the ability of both types of macrophages to phagocytize beads and generate both types of reactive species, which was correlated with a decrement in listericidal activity. These results demonstrate that DCPA has profound effects on macrophage function and provide insight into the potential mechanisms of immunosuppression by DCPA.

Modulating temporal control of NF-kappaB activation: implications for therapeutic and assay selection

The activation of transcription factor NF-kappaB (nuclear factor-kappaB) plays a central role in the induction of many inflammatory response genes. This process is characterized by either oscillations or stable induction of NF-kappaB nuclear binding. Changes in dynamics of binding result in the expression of distinct subsets of genes leading to different physiological outcomes. We examined NF-kappaB DNA binding activity in lipopolysaccharide (LPS)-stimulated IC-21 cells by electromobility shift assay and nonradioactive transcription factor assay and interpreted the results using a kinetic model of NF-kappaB activation. Both assays detected damped oscillatory behavior of NF-kappaB with differences in sensitivity and reproducibility. 3,4-Dichloropropionaniline (DCPA) was used to modulate the oscillatory behavior of NF-kappaB after LPS stimulation. DCPA is known to inhibit the production of two NF-kappaB-inducible cytokines, IL-6 and tumor necrosis factor alpha, by reducing but not completely abrogating NF-kappaB-induced transcription. DCPA treatment resulted in a potentiation of early LPS-induced NF-kappaB activation. The nonradioactive transcription factor assay, which has a higher signal/noise ratio than the electromobility shift assay, combined with in silico modeling, produced results that revealed changes in NF-kappaB dynamics which, to the best of our knowledge, have never been previously reported. These results highlight the importance of cell type and stimulus specificity in transcription factor activity assessment. In addition, assay selection has important implications for network inference and drug discovery.

Enhanced susceptibility to Leishmania infection in resistant mice in the absence of immediate early response gene X-1

Immediate early response gene X-1 (IEX-1) is a stress-inducible gene abundantly expressed in macrophages and T cells following various stimuli. To explore a potential role for IEX-1 in control of the susceptibility to Leishmania major infection, the inflammatory response during cutaneous leishmaniasis was evaluated in 129Sv/C57BL/6-resistant mice in the presence or absence of IEX-1. Null mutation of IEX-1 enhanced the susceptibility of the mice to L. major infection, and aggravated inflammatory responses in comparison with wild-type control mice. The excessive inflammation was not ascribed to a Th2-biased immune response or a defect in Th1 polarization, but rather to an elevated level of IL-17 production by both gammadelta T and CD4(+) cells, concomitant with an increase of the neutrophil recruitment early in the infection. The lack of IEX-1 also suppressed TNF-alpha production in both macrophages and T cells, resulting in a high intralesional load of parasites and delayed healing of the lesion, both of which were reversed by TNF-alpha treatment. These findings indicate the crucial role of IL-17 and TNF-alpha in determining the outcome of L. major infection beyond a balance between Th1- and Th2-mediated immune responses.

Reciprocal regulation of the survival and apoptosis of Th17 and Th1 cells in the colon

BACKGROUND

The immediate early response gene X-1 (IEX-1) is a stress-inducible gene involved in the regulation of cell growth, apoptosis and inflammation.

METHODS

Acute colitis was induced by treatment of IEX-1 knockout (KO) and wild type (WT) control mice with dextran sulfate sodium (DSS), whereas chronic colitis was induced in Rag-/- mice by adoptive transfer of CD4(+) CD45RB(hi) T cells isolated from the two strains of mice. The diseases and responses of lamina propria lymphocytes were analyzed in the mice.

RESULTS

IEX-1 KO mice produced IL-17 in the colon significantly greater than WT control mice following DSS treatment owing to better survival and differentiation of both IL-17-secreting γδ T cells and Th17 cells. The altered level of IL-17 production contributed critically to the reduced colon inflammation in IEX-1 KO mice, and administration of neutralizing anti-IL-17 antibody increased susceptibility of the animal to the disease. Strikingly, in contrast to the better survival of T cells producing IL-17, lack of IEX-1 enhanced apoptosis in proinflammatory T cells producing interferon gamma (IFN-γ). Enhanced apoptosis in Th1 cells and better survival of Th17 cells may both result in a delayed onset of colitis in Rag-/- mice receiving pathogenic CD4(+) CD45RB(hi) T cells isolated from IEX-1 KO animals compared to those mice transferred with WT counterparts

CONCLUSIONS

The present study demonstrates the refractoriness of IEX-1 knockout (KO) mice to DSS-induced colitis and diminished pathogenesis of IEX-1-deficient CD4(+) CD45RB(hi) T cells. These data demonstrate that IEX-1 reciprocally regulates T-cell survival and apoptosis in a subset-dependent fashion. Inhibition of IEX-1 may thus offer novel strategies for colitis treatment by simultaneous induction of apoptosis in proinflammatory Th1 cells while promoting the survival and differentiation of a protective T-cell subset.

IEX-1 deficiency protects against colonic cancer

The immediate early response gene X-1 (IEX-1) is involved in regulation of various cellular processes including proliferation, apoptosis in part by controlling homeostasis of reactive oxygen species (ROS) at mitochondria. The present study shows reduced inflammatory responses and colorectal cancer in IEX-1 knockout (KO) mice treated with azoxymethane/dextran sulfate sodium (DSS). However, DSS induced worse colitis in RAG(-/-)IEX-1(-/-) double KO mice than in RAG and IEX-1 single KO mice, underscoring an importance of T cells in IEX-1 deficiency-induced protection against colon inflammation. Lack of IEX-1 promoted the differentiation of interleukin (IL)-17-producing T cells, concomitant with upregulation of Gαi2 expression, a gene that is well-documented for its role in the control of inflammation in the colon. In accordance with this, T-helper 17 (T(H)17) cell differentiation was compromised in the absence of Gαi2, and deletion of Gαi2 in T cells alone aggravated colon inflammation and colorectal cancer development after azoxymethane/DSS treatment. Null mutation of IEX-1 also enhanced both proliferation and apoptosis of intestinal epithelial cells (IEC) after injury. A potential impact of this altered IEC turnover on colon inflammation and cancer development is discussed. These observations provide a linkage of IEX-1 and Gαi2 expression in the regulation of T(H)17 cell differentiation and suggest a previously unappreciated role for IEX-1 in the control of colon epithelial homeostasis.

A review of the immunotoxicity of the pesticide 3,4-dichloropropionanalide

The pesticide 3,4-dichloropropionanilide (propanil or, alternatively, DCPA) is a member of the acetanilide chemical family and is predominantly used for the control of weeds on commercial rice crops worldwide. This article was written to provide a brief review of the general toxicity of propanil followed by a detailed summary of the immunotoxicity studies that were performed to date in mammalian in vivo and in vitro models. Propanil affects the immune system at organ, cellular, and molecular levels. Studies demonstrated that it produces thymic atrophy and splenomegaly and decreases developing T- and B-cell populations in the thymus and bone marrow. Natural killer (NK) cells and macrophages are critical components of the innate immune system. NK cell cytotoxicity and the ability of macrophages to phagocytose, kill pathogenic bacteria, and produce inflammatory cytokines are suppressed by propanil. Propanil also affects the respiratory burst of macrophages, inhibiting reactive oxygen and nitrogen species production. Molecular mechanisms responsible for propanil's effects have begun to be elucidated and include alterations in nuclear factor (NF)-kappaB transcription factor activity and intracellular Ca(2+) signaling. Propanil exposure alters a number of functions of mature T lymphocytes and B lymphocytes that impacts the adaptive immune response. T-cell cytotoxic activity and cytokine production are major T-cell functions inhibited by propanil. The humoral antibody response to model antigens and intact bacteria is differentially affected after propanil exposure. How these changes in innate and adaptive immune responses impact the host response to bacterial challenge or vaccination has begun to be examined.

Impaired 3',5'-cyclic adenosine monophosphate-mediated signaling in immediate early responsive gene X-1-deficient vascular smooth muscle cells

Gene-targeted deletion of the immediate early responsive gene X-1 (IEX-1) results in a significant increase in systemic arterial blood pressure, but the underlying mechanism is not understood. Studies of arterial reactivity in isolated aortas revealed normal endothelium-dependent and -independent vasorelaxation and vasoconstriction but reduced cAMP-dependent vasorelaxation in the absence of IEX-1. This defect in cAMP signaling was also evident in endothelium-denuded aortic rings, consistent with the enhancement of mitochondrial O2·- production only in IEX-1-deficient vascular smooth muscle cells, not in endothelial cells. Excessive production of reactive oxygen species at mitochondria augmented the expression of Gα(i2), suppressing cAMP production in vascular smooth muscle cells. The role of mitochondrial reactive oxygen species in the upregulation of Gα(i2) leading to the development of hypertension was supported by the ability of antioxidant or pertussis toxin to restore the cAMP-dependent vasorelaxation to a normal level and reverse established hypertension in IEX-1 homozygous knockout mice. Our results suggest that hypertension in IEX-1 knockout mice may arise primarily from impaired cAMP signaling induced by overproduction of mitochondrial reactive oxygen species in vascular smooth muscle cells and demonstrate a causal relationship between mitochondrial dysfunction and cAMP-dependent vasorelaxation.

Influenza vaccination in the elderly boosts antibodies against conserved viral proteins and egg-produced glycans

Seasonal influenza vaccination elicits a diminished adaptive immune response in the elderly, and the mechanisms of immunosenescence are not fully understood. Using Ig-Seq, we found a marked increase with age in the prevalence of cross-reactive (CR) serum antibodies that recognize both the H1N1 (vaccine-H1) and H3N2 (vaccine-H3) components of an egg-produced split influenza vaccine. CR antibodies accounted for 73% ± 18% of the serum vaccine responses in a cohort of elderly donors, 65% ± 15% in late middle-aged donors, and only 13% ± 5% in persons under 35 years of age. The antibody response to non-HA antigens was boosted by vaccination. Recombinant expression of 19 vaccine-H1+H3 CR serum monoclonal antibodies (s-mAbs) revealed that they predominantly bound to non-HA influenza proteins. A sizable fraction of vaccine-H1+H3 CR s-mAbs recognized with high affinity the sulfated glycans, in particular sulfated type 2 N-acetyllactosamine (Galβ1-4GalNAcβ), which is found on egg-produced proteins and thus unlikely to contribute to protection against influenza infection in humans. Antibodies against sulfated glycans in egg-produced vaccine had been identified in animals but were not previously characterized in humans. Collectively, our results provide a quantitative basis for how repeated exposure to split influenza vaccine correlates with unintended focusing of serum antibody responses to non-HA antigens that may result in suboptimal immunity against influenza.

Nitrates/nitrites alter human lymphocyte proliferation and cytokine production

Nitrate from drinking water is converted in the body to nitrite by bacteria in the gut. This project examined effects of nitrate/nitrite on immune functions, i.e., human lymphocyte proliferation and cytokine production. Nitrate had no effect on lymphocyte growth, but nitrite decreased proliferation. Neither inhibited fibroblast growth. In 1/3 to 2/3 of the subjects tested, sodium nitrate or nitrite decreased production of Th1 cytokines (interleukin-2, interferon-gamma, and tumor necrosis factor-beta). Nitrate and nitrite either increased or had no effect on the production of the Th2 cytokine interleukin-10. A Th1 immune response is associated with resistance to a variety of infectious diseases; a Th2 response is associated with disease susceptibility. Because nitrate/nitrite shifted the balance from a Th1 to a Th2 response in some individuals, exposure to these compounds may decrease these persons' responsiveness to infectious diseases. The levels of nitrate used in this study are relevant to human health because they are present in the liquid portion (nonbreastfed) of some 2-month-old infants' diets in rural Romania.

AF03 adjuvant improves anti-hemagglutinin and anti-neuraminidase immune responses induced by licensed seasonal quadrivalent influenza vaccines in mice

Seasonal influenza remains a serious public health concern as the viral infection spreads easily from person to person and due to antigenic drift of neutralizing epitopes. Vaccination is the best method for disease prevention, however current seasonal influenza vaccines stimulate antibodies which are often effective against only antigenically similar strains. To boost the immune responses and increase vaccine effectiveness, adjuvants have been used for the past 20 years. The current study explores the use of oil-in-water adjuvant, AF03 to improve an immunogenicity of 2 licensed vaccines. A standard-dose inactivated quadrivalent influenza vaccine (IIV4-SD), containing both hemagglutinin (HA) and neuraminidase (NA) antigens, and recombinant quadrivalent influenza vaccine (RIV4), containing only HA-antigen were adjuvanted with AF03 in naïve BALB/c mouse model. Functional HA-specific antibody titers against all four homologous vaccine strains were enhanced by AF03, indicating potential increase in protective immunity. An increase in HA-specific total immunoglobulin G (IgG) binding titers were detected against homologous HAs, heterologous panel of 30 H3 HAs and seven Influenza B HAs. The neuraminidase inhibition (NAI) activity was significantly higher in IIV4-SD-AF03 group. Use of AF03 adjuvant improved the immune response to two influenza vaccines in a mouse model via an increase in functional and total antibodies against NA and a broad panel of HA-antigens.

Application of replication-defective West Nile virus vector to non-flavivirus vaccine targets

The RepliVax vaccine platform(RV) is based on flavivirus genomes that are rationally attenuated by deletion. The self-limiting infection provided by RV has been demonstrated to be safe, highly immunogenic and efficacious for several vaccine candidates against flaviviruses. Here respiratory syncytial virus (RSV) F, influenza virus HA, and simian immunodeficiency virus (SIV) Env proteins were expressed in place of either prM-E or C-prM-E gene deletions of the West Nile (WN) virus genome. The resulting RV-RSV, -influenza and -SIV vaccine prototypes replicated efficiently in complementing helper cells expressing the WN structural proteins in trans. Expressed antigens exhibited correct post-translational processing and the RV recombinants were shown to be highly attenuated and immunogenic in mice, eliciting strong antigen-specific antibodies as well as detectable T-cell responses. These data support the utility of RV vectors for development of vaccines against non-flavivirus targets including rabies and HIV.

Formulation development of a stable influenza recombinant neuraminidase vaccine candidate

Current influenza vaccines could be augmented by including recombinant neuraminidase (rNA) protein antigen to broaden protective immunity and improve efficacy. Toward this goal, we investigated formulation conditions to optimize rNA physicochemical stability. When rNA in sodium phosphate saline buffer (NaPBS) was frozen and thawed (F/T), the tetrameric structure transitioned from a "closed" to an "open" conformation, negatively impacting functional activity. Hydrogen deuterium exchange experiments identified differences in anchorage binding sites at the base of the open tetramer, offering a structural mechanistic explanation for the change in conformation and decreased functional activity. Change to the open configuration was triggered by the combined stresses of acidic pH and F/T. The desired closed conformation was preserved in a potassium phosphate buffer (KP), minimizing pH drop upon freezing and including 10% sucrose to control F/T stress. Stability was further evaluated in thermal stress studies where changes in conformation were readily detected by ELISA and size exclusion chromatography (SEC). Both tests were suitable indicators of stability and antigenicity and considered potential critical quality attributes (pCQAs). To understand longer-term stability, the pCQA profiles from thermally stressed rNA at 6 months were modeled to predict stability of at least 24-months at 5°C storage. In summary, a desired rNA closed tetramer was maintained by formulation selection and monitoring of pCQAs to produce a stable rNA vaccine candidate. The study highlights the importance of understanding and controlling vaccine protein structural and functional integrity.

The antigenic landscape of human influenza N2 neuraminidases from 2009 until 2017

Human H3N2 influenza viruses are subject to rapid antigenic evolution which translates into frequent updates of the composition of seasonal influenza vaccines. Despite these updates, the effectiveness of influenza vaccines against H3N2-associated disease is suboptimal. Seasonal influenza vaccines primarily induce hemagglutinin-specific antibody responses. However, antibodies directed against influenza neuraminidase (NA) also contribute to protection. Here, we analysed the antigenic diversity of a panel of N2 NAs derived from human H3N2 viruses that circulated between 2009 and 2017. The antigenic breadth of these NAs was determined based on the NA inhibition (NAI) of a broad panel of ferret and mouse immune sera that were raised by infection and recombinant N2 NA immunisation. This assessment allowed us to distinguish at least four antigenic groups in the N2 NAs derived from human H3N2 viruses that circulated between 2009 and 2017. Computational analysis further revealed that the amino acid residues in N2 NA that have a major impact on susceptibility to NAI by immune sera are in proximity of the catalytic site. Finally, a machine learning method was developed that allowed to accurately predict the impact of mutations that are present in our N2 NA panel on NAI. These findings have important implications for the renewed interest to develop improved influenza vaccines based on the inclusion of a protective NA antigen formulation.

Boosting neuraminidase immunity in the presence of hemagglutinin with the next generation of influenza vaccines

Neuraminidase (NA), the second most abundant surface glycoprotein on the influenza virus, plays a key role in viral replication and propagation. Despite growing evidence showing that NA-specific antibodies correlate with resistance to disease in humans, current licensed vaccines focus almost entirely on the hemagglutinin (HA) antigen. Here, we demonstrate that recombinant NA (rNA) protein is highly immunogenic in both naïve mice and ferrets, as well as in pre-immune ferrets, irrespective of the level of match with preexisting immunity. Ferrets vaccinated with rNA developed mild influenza disease symptoms upon challenge with human H3N2 influenza virus, and anti-NA antibody responses appeared correlated with reduction in disease severity. The addition of rNA to a quadrivalent HA-based vaccine induced robust NA-specific humoral immunity in ferrets, while retaining the ability to induce HA-specific immunity. These results demonstrate that the addition of rNA is a viable option to increase immunogenicity and potentially efficacy versus currently licensed influenza vaccines by means of boosting NA immunity.

A phase I study of the safety, reactogenicity and immunogenicity of two quadrivalent seasonal influenza vaccines (Fluzone® or Flublok®) with or without one of two adjuvants (AF03 or Advax-CpG55.2) in healthy adults 18-45 years of age

Seasonal influenza continues to cause significant morbidity and mortality, particularly for the elderly and immunocompromised. Current licensed influenza vaccines provide only partial protection even for immunocompetent hosts. Vaccine adjuvants can improve the magnitude and breadth of immune responses and there is considerable interest in identifying new adjuvants that can improve immune responses to seasonal influenza vaccines. This phase I, randomized, double-blind trial evaluated the safety and immunogenicity of one dose of 2018/2019 quadrivalent influenza vaccine (either Fluzone® or Flublok®) administered intramuscularly with or without one of two adjuvants (AF03 or Advax-CpG55.2). A total of 241 healthy adults aged 18-45 years were enrolled and randomized to 1 of 6 groups. Groups 1-3 received one dose of Fluzone® QIV 2018/2019 administered alone or with AF03 or Advax-CpG55.2 and Groups 4-6 received one dose of Flublok® QIV 2018/2019 alone or with one of these two adjuvants. All participants received Fluzone® or Flublok® QIV 2019/2020 ninety days later. Primary objectives were to evaluate safety and reactogenicity along with changes in hemagglutinin inhibition (HAI), neuraminidase inhibition (NAI) and neutralizing antibodies to 2018/2019 seasonal influenza antigens, comparing Day 1 and Day 29 titers. Secondary objectives evaluated the impact of adjuvants on immune responses after subsequent doses of unadjuvanted seasonal influenza vaccine and immunologic responses to heterologous influenza H1 and H3 antigens. Overall, the adjuvanted vaccines were safe and generated robust immune responses against both homologous and heterologous strains. Similar responses were seen across all six study arms. Both adjuvants were associated with qualitatively improved immune responses against some strains at varying timepoints, but results were inconsistent. There were no substantial differences in safety or reactogenicity identified between the study groups and all vaccine formulations were well tolerated. In this highly immunologically-experienced cohort, neither AF03 nor Advax-CpG55.2 demonstrated notable benefit when added to the seasonal influenza vaccine. (ClinicalTrials.gov ID# NCT03945825).