Doxycycline Treatment of Mansonella perstans-Infected Individuals Affects Immune Cell Activation and Causes Long-term T-cell Polarization

BACKGROUND

Doxycycline is used for treatment of Mansonella perstans infection. Immune modulatory effects of both M. perstans and doxycycline have been described but long-term implications on host immune response are not defined. Here we determined multiple immune parameters of M. perstans-infected individuals before and after doxycycline treatment to characterize doxycycline effects on host T-cell immunity.

METHODS

Immune characterization of doxycycline-treated M. perstans-infected individuals was performed as part of an open-label randomized clinical trial. Immune cell population phenotyping by flow cytometry and functional in vitro T-cell assays were performed at baseline, 6 months, and "long term" (18-24 months) after treatment start. Treatment efficacy, based on peripheral blood microfilaria (mf) burden, was correlated with immune parameters and effects on immune response against concomitant Mycobacterium tuberculosis infection were determined.

RESULTS

Immune population phenotyping indicated changes in functional T-cell responses after doxycycline treatment. Constitutive and superantigen-induced T-cell activation and polarization towards T-helper type (TH) 1 phenotype at baseline declined after doxycycline treatment, whereas low proportions of TH17 and TH1* cells at baseline increased significantly at follow-up. In accordance, long-term decline in antigen-specific TH1 responses against concomitant M. tuberculosis infection was seen. Notably, only TH17 and TH1* changes after 6 months and TH17 at baseline were negatively correlated with M. perstans microfilaria burden or reduction, whereas long-term changes were not associated with treatment efficacy.

CONCLUSIONS

We found long-term immune modulatory effects of doxycycline treatment leading to decreased constitutive T-cell activation, polarization towards TH17/TH1*, and impaired immune response against concomitant M. tuberculosis infection.

FRTX-02, a selective and potent inhibitor of DYRK1A, modulates inflammatory pathways in mouse models of psoriasis and atopic dermatitis

Dual-specificity tyrosine phosphorylation-regulated kinase 1 A (DYRK1A) has been proposed as a novel regulator of adaptive immune homeostasis through modulating T cell polarization. Thus, DYRK1A could present a potential target in autoimmune disorders. Here, we identify FRTX-02 as a novel compound exhibiting potent and selective inhibition of DYRK1A. FRTX-02 induced transcriptional activity of the DYRK1A substrate NFAT in T cell lines. Correspondingly, FRTX-02 promoted ex vivo CD4⁺ polarization into anti-inflammatory Tregs and reduced their polarization into pro-inflammatory Th1 or Th17 cells. We show that FRTX-02 could also limit innate immune responses through negative regulation of the MyD88/IRAK4-NF-κB axis in a mast cell line. Finally, in mouse models of psoriasis and atopic dermatitis, both oral and topical formulations of FRTX-02 reduced inflammation and disease biomarkers in a dose-dependent manner. These results support further studies of DYRK1A inhibitors, including FRTX-02, as potential therapies for chronic inflammatory and autoimmune conditions.

Prenatal Exposure to Di-Ethyl Phthalate (DEP) Is Related to Increasing Neonatal IgE Levels and the Altering of the Immune Polarization of Helper-T Cells

Introduction: Phthalates are substances that are added to plastic products to increase their plasticity. These substances are released easily into the environment and can act as endocrine disruptors. Epidemiological studies in children have showed inconsistent findings regarding the relationship between prenatal or postnatal exposure to phthalates and the risk of allergic disease. Our hypothesis is that prenatal exposure to phthalates may contribute to the development of allergies in children. Material and methods: The objective of this study was to determine the associations between urinary phthalate metabolite concentrations in pregnant women, maternal atopic diathesis, maternal lifestyle, and cord blood IgE. Pregnant mothers and paired newborns (n = 101) were enrolled from an antenatal clinic. The epidemiologic data and the clinical information were collected using standard questionnaires and medical records. The maternal blood and urine samples were collected at 24–28 weeks gestation, and cord blood IgE, IL-12p70, IL-4, and IL-10 levels were determined from the newborns at birth. The link between phthalates and maternal IgE was also assessed. To investigate the effects of phthalates on neonatal immunity, cord blood mononuclear cells (MNCs) were used for cytokine induction in another in vitro experiment. Results: We found that maternal urine monoethyl phthalate (MEP) (a metabolite of di-ethyl phthalate (DEP)) concentrations are positively correlated with the cord blood IgE of the corresponding newborns. The cord blood IL-12p70 levels of mothers with higher maternal urine MEP groups (high DEP exposure) were lower than mothers with low DEP exposure. In vitro experiments demonstrated that DEP could enhance IL-4 production of cord blood MNCs rather than adult MNCs. Conclusion: Prenatal DEP exposure is related to neonatal IgE level and alternation of cytokines relevant to Th1/Th2 polarization. This suggests the existence of a link between prenatal exposure to specific plasticizers and the future development of allergies.

Modulation of CD4 T cell function via CD6-targeting

In recent years molecules involved on the immune synapse became successful targets for therapeutic immune modulation. CD6 has been extensively studied, yet, results regarding CD6 biology have been controversial, in spite of the ubiquitous presence of this molecule on virtually all CD4 T cells. We investigated the outcome of murine and human antibodies targeting CD6 domain 1. We found that CD6-targeting had a major impact on the functional specialization of CD4 cells, both human and murine. Differentiation of CD4 T cells towards a Foxp3⁺ Treg fate was prevented with increasing doses of anti-CD6, while Th1 polarization was favoured. No impact was observed on Th2 or Th17 specialization. These in vitro results provided an explanation for the dose-dependent outcome of in vivo anti-CD6 administration where the anti-inflammatory action is lost at the highest doses. Our data show that therapeutic targeting of the immune synapse may lead to paradoxical dose-dependent effects due to modification of T cell fate.

Loss of GTPase of immunity-associated protein 5 (Gimap5) promotes pathogenic CD4+ T-cell development and allergic airway disease

BACKGROUND

GTPase of immunity-associated protein 5 (GIMAP5) is essential for lymphocyte homeostasis and survival. Recently, human GIMAP5 single nucleotide polymorphisms have been linked to an increased risk for asthma, whereas loss of Gimap5 in mice has been associated with severe CD4+ T cell-driven immune pathology.

OBJECTIVE

We sought to identify the molecular and cellular mechanisms by which Gimap5 deficiency predisposes to allergic airway disease.

METHODS

CD4+ T-cell polarization and development of pathogenic CD4+ T cells were assessed in Gimap5-deficient mice and a human patient with a GIMAP5 loss-of-function (LOF) mutation. House dust mite-induced airway inflammation was assessed by using a complete Gimap5 LOF (Gimap5sph/sph) and conditional Gimap5fl/flCd4Cre/ert2 mice.

RESULTS

GIMAP5 LOF mutations in both mice and human subjects are associated with spontaneous polarization toward pathogenic TH17 and TH2 cells in vivo. Mechanistic studies in vitro reveal that impairment of Gimap5-deficient TH cell differentiation is associated with increased DNA damage, particularly during TH1-polarizing conditions. DNA damage in Gimap5-deficient CD4+ T cells could be controlled by TGF-β, thereby promoting TH17 polarization. When challenged with house dust mite in vivo, Gimap5-deficient mice displayed an exacerbated asthma phenotype (inflammation and airway hyperresponsiveness), with increased development of TH2, TH17, and pathogenic TH17/TH2 cells.

CONCLUSION

Activation of Gimap5-deficient CD4+ T cells is associated with increased DNA damage and reduced survival that can be overcome by TGF-β. This leads to selective survival of pathogenic TH17 cells but also TH2 cells in human subjects and mice, ultimately promoting allergic airway disease.

Effects of arsenic on porcine dendritic cells in vitro

Exposure to arsenic (As) is an ongoing, and in some places increasing, health problem. Still, however, the effects of As exposure on the immune system are not well understood. Dendritic cells (DC) are a critical immune cell that bridges the innate and adaptive immune systems. To determine the impact of inorganic (i)As exposure on DC, the effects of (geo)anthropogenically relevant levels of NaAsO₂ on the function of porcine monocyte-derived DC (MoDC) were evaluated in an in vitro model. The results showed a low dose of iAs reduced the phagocytic capacity of MoDC. Furthermore, although surface expression of DC activation markers, such as major histocompatibility complex (MHC)-II, CD80/86, CD40 and CD25, were only slightly changed, MoDC T-cell proliferation-inducing capacity was remarkably diminished by iAs treatment. Additionally, iAs induced significant interleukin (IL)-6 secretion by MoDC after 12- or 24-h incubation, whereas IL-1β secretion was only significantly up-regulated after 12 h. The secretion patterns of IL-8, tumor necrosis factor α (TNFα and IL-10 by iAs-treated MoDC were almost similar to that by mock-treated MoDC. Considering the broad roles of DC in immunobiology, this finding deepens the understanding of molecular mechanisms/functional consequences underpinning the immunopathology, inflammation, and increases in infection arising from As exposure.

T-cell polarization: Potential serological markers in preterm and term infants

BACKGROUND

The immaturity of immune system characterizes newborn infants. Possible serological markers of Th1 and Th2 immune response are the lymphocyte activation gene-3 (CD223) and soluble CD30, respectively (sCD30).

AIMS

The aim of our study was to evaluate the relationship between Th1 and Th2 immune response and gestational age (GA), comparing data in preterm and term neonates.

STUDY DESIGN

Cord blood from 20 preterm (GA: 33±2weeks, BW 1950±490g) and 20 term infants (GA: 38±1weeks, BW: 3177±330g) were tested for sCD30 and CD223 levels by ELISA. IFNγ levels produced by cord blood lymphocytes were also analyzed, both before and after stimulation with phytohaemagglutinin (PHA).

RESULTS

sCD30 resulted significantly higher in preterm neonates when compared with term neonates (60±7.6 vs 42.6±3.9U/ml p<0.05). CD223 was undetectable in preterm neonates while resulting at a level of 176.1±112.6ng/ml in term neonates. After stimulation with PHA, a significant increase in IFNγ levels was only observed in term neonates (326.6±72.7pg/ml p<0.05).

CONCLUSIONS

Our findings show that sCD30 is present and measurable in term and preterm infants, while CD223 is detectable only in term infants and that Th-cell polarization could also depend on gestational age. Our data suggest that a Th2 immune response seems predominant in preterm neonates.

Engagement of distinct epitopes on CD43 induces different co-stimulatory pathways in human T cells

Co‐receptors, being either co‐stimulatory or co‐inhibitory, play a pivotal role in T‐cell immunity. Several studies have indicated that CD43, one of the abundant T‐cell surface glycoproteins, acts not only as a potent co‐receptor but also as a negative regulator for T‐cell activation. Here we demonstrate that co‐stimulation of human peripheral blood (PB) T cells through two distinct CD43 epitopes recognized by monoclonal antibodies (mAb) CD43‐6E5 (T_6E5‐act) and CD43‐10G7 (T_10G7‐act) potently induced T‐cell proliferation. However, T‐cell co‐stimulation through two CD43 epitopes differentially regulated activation of nuclear factor of activated T cells (NFAT) and nuclear factor‐κB (NF‐κB) transcription factors, T‐cell cytokine production and effector function. T_6E5‐act produced high levels of interleukin‐22 (IL‐22) and interferon‐γ (IFN‐γ) similar to T cells activated via CD28 (T_CD28‐act), whereas T_10G7‐act produced low levels of inflammatory cytokines but higher levels of regulatory cytokines transforming growth factor‐β (TGF‐β) and interleukin‐35 (IL‐35). Compared with T_6E5‐act or to T_CD28‐act, T_10G7‐act performed poorly in response to re‐stimulation and further acquired a T‐cell suppressive function. T_10G7‐act did not directly inhibit proliferation of responder T cells, but formed stable heterotypic clusters with dendritic cells (DC) via CD2 to constrain activation of responder T cells. Together, our data demonstrate that CD43 is a unique and polarizing regulator of T‐cell function.

Hyaluronan synthesis is necessary for autoreactive T-cell trafficking, activation, and Th1 polarization

The extracellular matrix polysaccharide hyaluronan (HA) accumulates at sites of autoimmune inflammation, including white matter lesions in multiple sclerosis (MS), but its functional importance in pathogenesis is unclear. We have evaluated the impact of 4-methylumbelliferone (4-MU), an oral inhibitor of HA synthesis, on disease progression in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. Treatment with 4-MU decreases the incidence of EAE, delays its onset, and reduces the severity of established disease. 4-MU inhibits the activation of autoreactive T cells and prevents their polarization toward a Th1 phenotype. Instead, 4-MU promotes polarization toward a Th2 phenotpye and induction of Foxp3(+) regulatory T cells. Further, 4-MU hastens trafficking of T cells through secondary lymphoid organs, impairs the infiltration of T cells into the CNS parenchyma, and limits astrogliosis. Together, these data suggest that HA synthesis is necessary for disease progression in EAE and that treatment with 4-MU may be a potential therapeutic strategy in CNS autoimmunity. Considering that 4-MU is already a therapeutic, called hymecromone, that is approved to treat biliary spasm in humans, we propose that it could be repurposed to treat MS.

Seeing through the dark: New insights into the immune regulatory functions of vitamin A

The importance of vitamin A for host defense is undeniable and the study of its mechanisms is paramount. Of the estimated 250 million preschool children who are vitamin A-deficient (VAD), 10% will die from their increased susceptibility to infectious disease. Vitamin A supplementation was established in the 1980s as one of the most successful interventions in the developing world. Understanding how vitamin A controls immunity will help curb the mortality and morbidity associated with vitamin A deficiency and exploit the immune-enhancing capacity of vitamin A to heighten host resistance to infectious disease. The discoveries that retinoic acid (RA) imprints the homing of leukocytes to the gut and enhances the induction of regulatory T cells, highlighted a potential role for RA in mucosal tolerance. However, more recently emerging data tell of a more profound systemic impact of RA on leukocyte function and commitment. In animal models using genetic manipulation of RA signaling, we learned when and how RA controls T cell fate. Here, we review the role for RA as a critical checkpoint regulator in the differentiation of CD4(+) T cells within the immune system.

DRB1*0402 may influence arthritis by promoting naive CD4+ T-cell differentiation in to regulatory T cells

HLA-DRB1*0401 expression in humans has been associated with a predisposition to developing rheumatoid arthritis (RA) and collagen-induced arthritis (CIA), while HLA-DRB1*0402 is not associated with susceptibility. Here, we determined if mice transgenic (Tg) for human *0401 have a CD4+ T-cell repertoire that predetermines proinflammatory cytokine production. The data show that both *0401 and *0402 Tg mice can produce TH1/TH17 cytokines, although the kinetics of response may be different. However, in the context of antigen-specific responses in a CIA model, *0402 Tg mice generate a TH2 response that may explain their resistance to developing arthritis. In addition, a significant subset of naïve CD4+ T cells from *0402 Tg mice can be activated in polarizing conditions to differentiate into Treg cells that produce IFN-γ. *0401 Tg mice harbor memory CD4+ T cells that differentiate into IL-17(+) cells in various polarizing conditions. Our data suggest that *0401 Tg mice generate a strong immune response to lipopolysaccharide and may be efficient in clearing infection, and may *0401 have been evolutionarily selected for this ability. Autoimmunity, such as RA, could likely be a bystander effect of the cytokine storm that, along with the presence of low Treg-cell numbers in *0401 Tg mice, causes immune dysregulation.