Interleukin-4 Receptor Alpha: From Innate to Adaptive Immunity in Murine Models of Cutaneous Leishmaniasis

The wide spectrum anti-inflammatory activity of andrographolide in comparison to NSAIDs: A promising therapeutic compound against the cytokine storm

The challenges of the COVID-19 pandemic have highlighted an increasing clinical demand for safe and effective treatment options against an overzealous immune defence response, also known as the "cytokine storm". Andrographolide is a naturally derived bioactive compound with promising anti-inflammatory activity in many clinical studies. However, its cytokine-inhibiting activity, in direct comparison to commonly used nonsteroidal anti-inflammatory drugs (NSAIDs), has not been extensively investigated in existing literature. The anti-inflammatory activities of andrographolide and common NSAIDs, such as diclofenac, aspirin, paracetamol and ibuprofen were measured on lipopolysaccharide (LPS) and interferon-γ induced RAW264.7 cells. The levels of PGE2, nitric oxide (NO), TNF-α & LPS-induced release of pro-inflammatory cytokines on differentiated human macrophage THP-1 cells were measured against increasing concentrations of andrographolide and aforementioned NSAIDs. The associated mechanistic pathway was examined on NFκB using flow cytometry on the human endothelial-leukocyte adhesion molecule (ELAM9) (E-selectin) transfected RAW264.7 cells with green fluorescent protein (GFP). Andrographolide exhibited broad and potent anti-inflammatory and cytokine-inhibiting activity in both cell lines by inhibiting the release of IL-6, TNF-α and IFN-γ, which are known to play a key role in the etiology of cytokine storm and the pathogenesis of inflammation. In comparison, the tested NSAIDs demonstrated weak or no activity against proinflammatory mediators except for PGE2, where the activity of andrographolide (IC50 = 8.8 μM, 95% CI = 7.4 to 10.4 μM) was comparable to that of paracetamol (IC50 = 7.73 μM, 95% CI = 6.14 to 9.73 μM). The anti-inflammatory action of andrographolide was associated with its potent downregulation of NFκB. The wide-spectrum anti-inflammatory activity of andrographolide demonstrates its therapeutic potential against cytokine storms as an alternative to NSAIDs.

Radiological Versus Clinical 1-Year Outcomes of Dupilumab in Refractory CRSwNP: A Real-Life Study

OBJECTIVE

To provide real-life evidence on long-term radiological changes in patients with severe chronic rhinosinusitis with nasal polyps (CRSwNP) treated with dupilumab, and to assess possible differences between radiological and clinical results in terms of endoscopic findings and Patient-Reported-Outcomes (PROs).

METHODS

Consecutive patients treated with dupilumab for recalcitrant CRSwNP were required to undergo CT scan at baseline (T0) and after 12 (T1) since first administration. A group of patients also performed CT scan at 52 weeks (T2) to assess long-term outcomes. At each timepoint, patients underwent nasal endoscopy, assessment of Nasal-Polyp-Score (NPS), Lund-Kennedy-Score (LKS), and had to fill in the 22-item Sinonasal-Outcome-Test (SNOT-22) and Visual-Analogue-Scales (VAS) for sinonasal symptoms.

RESULTS

In fifty-three included patients, from T0 to T1 we detected a significant reduction in mean Lund-Mackay score (LM), PROs (SNOT-22, VAS) and endoscopic (NPS, LKS) scores (p < 0.05). In the subset of patients that reached T2 (n = 30), compared to T1, we observed a further significant decrease in mean LM, SNOT-22, VAS, and NPS scores, but not in LKS (p = 0.420). At T1, the highest improvement was observed in PROs (SNOT-22: 56.26%), and polyp size (NPS: 49.83%). Conversely, between T1 and T2, sinus opacification was shown to be the most improved outcome (LM: 36.86%).

CONCLUSIONS

Our experience showed that poorly controlled CRSwNP patients treated with dupilumab experienced significant improvement in radiologic, endoscopic and clinical disease severity. While in the initial 3 months, PROs garnered attention for showing earlier effectiveness, radiological outcomes revealed sustained and gradual efficacy in a longer term.

LEVEL OF EVIDENCE

Level 4. According to the Oxford Center for Evidence-Based Medicine 2011 level of evidence guidelines, this non-randomized retrospective cohort study is classified as level 4 evidence Laryngoscope, 134:2626-2633, 2024.

Interleukin-17-mediated protective cytokine signaling against degeneration of the retinal pigment epithelium

Injuries to the retinal pigment epithelium (RPE) and outer retina often result in the accumulation of retinal microglia within the subretinal space. These subretinal microglia play crucial roles in inflammation and resolution, but the mechanisms governing their functions are still largely unknown. Our previous research highlighted the protective functions of choroidal γδ T cells in response to RPE injury. In the current study, we employed single-cell RNA sequencing approach to characterize the profiles of immune cells in mouse choroid. We found that γδ T cells were the primary producer of interleukin-17 (IL-17) in the choroid. IL-17 signaled through its receptor on the RPE, subsequently triggering the production of interleukin-6. This cascade of cytokines initiated a metabolic reprogramming of subretinal microglia, enhancing their capacity for lipid metabolism. RPE-specific knockout of IL-17 receptor A led to the dysfunction of subretinal microglia and RPE pathology. Collectively, our findings suggest that responding to RPE injury, the choroidal γδ T cells can initiate a protective signaling cascade that ensures the proper functioning of subretinal microglia.

Therapeutic Targets and Precision Medicine in COPD: Inflammation, Ion Channels, Both, or Neither?

The development of a wider range of therapeutic options is a key objective in drug discovery for chronic obstructive pulmonary disease (COPD). Fundamental advances in lung biology have the potential to greatly expand the number of therapeutic targets in COPD. The recently reported successful Phase 3 clinical trial of the first biologic agent for COPD, the monoclonal antibody dupilumab, adds additional support to the importance of targeting inflammatory pathways in COPD. However, numerous other cellular mechanisms are important targets in COPD therapeutics, including airway remodeling, the CFTR ion channel, and mucociliary function. Some of these emerging targets can be exploited by the expanded use of existing COPD drugs, such as roflumilast, while targeting others will require the development of novel molecular entities. The identification of additional therapeutic targets and agents has the potential to greatly expand the value of using clinical and biomarker data to classify COPD into specific subsets, each of which can be predictive of an enhanced response to specific subset(s) of targeted therapies. The author reviews established and emerging drug targets in COPD and uses this as a framework to define a novel classification of COPD based on therapeutic targets. This novel classification has the potential to enhance precision medicine in COPD patient care and to accelerate clinical trials and pre-clinical drug discovery efforts.

CXCR5 and TIM-3 expressions define distinct exhausted T cell subsets in experimental cutaneous infection with Leishmania mexicana

T-cell exhaustion is a key stage in chronic infections since it limits immunopathology, but also hinders the elimination of pathogens. Exhausted T (Tex) cells encompass dynamic subsets, including progenitor cells that sustain long-term immunity through their memory/stem like properties, and terminally-differentiated cells, resembling the so-called Tex cells. The presence of Tex cells in chronic leishmaniasis has been reported in humans and murine models, yet their heterogeneity remains unexplored. Using flow cytometry, we identified Tex cells subtypes based on PD-1, CXCR5 and TIM-3 expressions in draining lymph nodes (dLNs) and lesion sites of C57BL/6 mice infected with L. mexicana at 30-, 60- and 90-days post-infection. We showed that infected mice developed a chronic infection characterized by non-healing lesions with a high parasite load and impaired Th1/Th2 cytokine production. Throughout the infection, PD-1+ cells were observed in dLNs, in addition to an enhanced expression of PD-1 in both CD4+ and CD8+ T lymphocytes. We demonstrated that CD4+ and CD8+ T cells were subdivided into PD-1+CXCR5+TIM-3- (CXCR5+), PD-1+CXCR5+TIM-3+ (CXCR5+TIM-3+), and PD-1+CXCR5-TIM-3+ (TIM-3+) subsets. CXCR5+ Tex cells were detected in dLNs during the whole course of the infection, whereas TIM-3+ cells were predominantly localized in the infection sites at day 90. CXCR5+TIM-3+ cells only increased at 30 and 60 days of infection in dLNs, whereas no increase was observed in the lesions. Phenotypic analysis revealed that CXCR5+ cells expressed significantly higher levels of CCR7 and lower levels of CX3CR1, PD-1, TIM-3, and CD39 compared to the TIM-3+ subset. CXCR5+TIM-3+ cells expressed the highest levels of all exhaustion-associated markers and of CX3CR1. In agreement with a less exhausted phenotype, the frequency of proliferating Ki-67 and IFN-γ expressing cells was significantly higher in the CXCR5+ subset within both CD4+ and CD8+ T cells compared to their respective TIM-3+ subsets, whereas CD8+CXCR5+TIM-3+ and CD8+TIM-3+ subsets showed an enhanced frequency of degranulating CD107a+ cells. In summary, we identified a novel, less-differentiated CXCR5+ Tex subset in experimental cutaneous leishmaniasis caused by L. mexicana. Targeting these cells through immune checkpoint inhibitors such as anti-PD-1 or anti PD-L1 might improve the current treatment for patients with the chronic forms of leishmaniasis.

After Bone Marrow Transplantation, the Cell-Intrinsic Th2 Pathway Promotes Recipient T Lymphocyte Survival and Regulates Graft-versus-Host Disease

Recipient T cells can aggravate or regulate lethal and devastating graft-versus-host disease (GVHD) after bone marrow transplantation (BMT). In this context, we have shown before that intestinal immune conditioning with helminths is associated with survival of recipient T cells and Th2 pathway-dependent regulation of GVHD. We investigated the mechanism of survival of recipient T cells and their contribution to GVHD pathogenesis in this helminth infection and BMT model after myeloablative preparation with total body irradiation in mice. Our results indicate that the helminth-induced Th2 pathway directly promotes the survival of recipient T cells after total body irradiation. Th2 cells also directly stimulate recipient T cells to produce TGF-β, which is required to regulate donor T cell-mediated immune attack of GVHD and can thereby contribute to recipient T cell survival after BMT. Moreover, we show that recipient T cells, conditioned to produce Th2 cytokines and TGF-β after helminth infection, are fundamentally necessary for GVHD regulation. Taken together, reprogrammed or immune-conditioned recipient T cells after helminth infection are crucial elements of Th2- and TGF-β-dependent regulation of GVHD after BMT, and their survival is dependent on cell-intrinsic Th2 signaling.

IL-4 induces reparative phenotype of RPE cells and protects against retinal neurodegeneration via Nrf2 activation

Retinal degeneration is a kind of neurodegeneration characterized by progressive neuronal death and dysfunction of retinal pigment epithelium (RPE) cells, leading to permanent visual impairment. It still lacks effective therapeutic options and new drugs are highly warranted. In this study, we found the expression of IL-4, a critical regulator of immunity, was reduced in both patients and mouse models. Importantly, exogenous intravitreal IL-4 application could exert a novel neuroprotective effect, characterized by well-preserved RPE layer and neuroretinal structure, as well as amplified wave-amplitudes in ERG. The RNA-seq analysis revealed that IL-4 treatment suppressed the essential oxidative and pro-inflammatory pathways in the degenerative retina. Particularly, IL-4 upregulated the IL-4Rα on RPE cells and induced a reparative phenotype via the activation of Nrf2 both in vitro and in vivo. Furthermore, the Nrf2-/- mice displayed no recovery in response to IL-4 application, highlighting a significant role of Nrf2 in IL-4-mediated protection. Our data provides evidence that IL-4 protects against retinal neurodegeneration by its antioxidant and anti-inflammatory property through IL-4Rα upregulation and Nrf2 activation in RPE cells. The IL-4/IL-4Rα-Nrf2 axis maybe the potential targets for the development of novel therapies for neurodegenerative diseases.

T-helper 2 mechanisms involved in human rhinovirus infections and asthma

Human rhinovirus (HRV) is the most common causative agent for the common cold and its respiratory symptoms. For those with asthma, cystic fibrosis, or chronic obstructive pulmonary disease, HRVs can lead to severe and, at times, fatal complications. Furthermore, an array of innate and adaptive host immune responses leads to varying outcomes ranging from subclinical to severe. In this review, we discuss the viral pathogenesis and host immune responses associated with this virus. Specifically, we focus on the immune responses that might skew a T-helper type 2 response, including alarmins, in those with allergic asthma. We also discuss the role of a poor innate immune response with interferons. Finally, we consider therapeutic options for HRV-associated exacerbations of asthma, including biologics and intranasal sprays on the basis of the current literature.

An integrated cytokine and kynurenine network as the basis of neuroimmune communication

Two of the molecular families closely associated with mediating communication between the brain and immune system are cytokines and the kynurenine metabolites of tryptophan. Both groups regulate neuron and glial activity in the central nervous system (CNS) and leukocyte function in the immune system, although neither group alone completely explains neuroimmune function, disease occurrence or severity. This essay suggests that the two families perform complementary functions generating an integrated network. The kynurenine pathway determines overall neuronal excitability and plasticity by modulating glutamate receptors and GPR35 activity across the CNS, and regulates general features of immune cell status, surveillance and tolerance which often involves the Aryl Hydrocarbon Receptor (AHR). Equally, cytokines and chemokines define and regulate specific populations of neurons, glia or immune system leukocytes, generating more specific responses within restricted CNS regions or leukocyte populations. In addition, as there is a much larger variety of these compounds, their homing properties enable the superimposition of dynamic variations of cell activity upon local, spatially limited, cell populations. This would in principle allow the targeting of potential treatments to restricted regions of the CNS. The proposed synergistic interface of 'tonic' kynurenine pathway affecting baseline activity and the superimposed 'phasic' cytokine system would constitute an integrated network explaining some features of neuroimmune communication. The concept would broaden the scope for the development of new treatments for disorders involving both the CNS and immune systems, with safer and more effective agents targeted to specific CNS regions.

Pathophysiology and Therapeutic Approaches for Spinal Cord Injury

Spinal cord injury (SCI) is a disabling condition that disrupts motor, sensory, and autonomic functions. Despite extensive research in the last decades, SCI continues to be a global health priority affecting thousands of individuals every year. The lack of effective therapeutic strategies for patients with SCI reflects its complex pathophysiology that leads to the point of no return in its function repair and regeneration capacity. Recently, however, several studies started to uncover the intricate network of mechanisms involved in SCI leading to the development of new therapeutic approaches. In this work, we present a detailed description of the physiology and anatomy of the spinal cord and the pathophysiology of SCI. Additionally, we provide an overview of different molecular strategies that demonstrate promising potential in the modulation of the secondary injury events that promote neuroprotection or neuroregeneration. We also briefly discuss other emerging therapies, including cell-based therapies, biomaterials, and epidural electric stimulation. A successful therapy might target different pathologic events to control the progression of secondary damage of SCI and promote regeneration leading to functional recovery.

Interleukin 4/13 signaling in cardiac regeneration and repair

Interleukin 4 (IL4) and interleukin 13 (IL13) are closely related cytokines that have been classically attributed to type II immunity, namely, differentiation of T-helper 2 (TH2) cells and alternative activation of macrophages. Although the role of IL4/13 has been well described in various contexts such as defense against helminth parasites, pathogenesis of allergic disease, and several models of wound healing, relatively little is known about the role of IL4/13 in the heart following injury. Emerging literature has identified various roles for IL4/13 in animal models of cardiac regeneration as well as in the adult mammalian heart following myocardial injury. Notably, although IL4 and IL13 signal to hematopoietic cell types following myocardial infarction (MI) to promote wound healing phenotypes, there is substantial evidence that these cytokines can signal directly to non-hematopoietic cell types in the heart during development, homeostasis, and following injury. Comprehensive understanding of the molecular and cellular actions of IL4/13 in the heart is still lacking, but overall evidence to date suggests that activation of these cytokines results in beneficial outcomes with respect to cardiac repair. Here, we aim to comprehensively review the role of IL4 and IL13 and their prospective mechanisms in cardiac regeneration and repair.

Orally administered solasodine, a steroidal glycoalkaloid, suppresses ovalbumin-induced exaggerated Th2-immune response in rat model of bronchial asthma

Bronchial asthma is a chronic lung disorder, that affects an estimated 262 million people worldwide, thereby, causing a large socio-economic burden. Drug molecules from natural sources have exhibited a good promise in providing an alternative therapy in many chronic ailments. Solasodine, a glycoalkaloid has received an immense interest due to its large pharmacological and industrial value, however, its usefulness in asthma control has not been investigated till date. In this work, solasodine was tested for its ability to reverse several characteristics of bronchial asthma induced by intraperitoneal injection of ovalbumin (OVA) and aluminium hydroxide in experimental rats. Treating asthmatic animals with solasodine (1 mg/kg b.w. or 10 mg/kg b.w.) or dexamethasone (2.5 mg/kg b.w.) reversed OVA-induced airway hyperresponsiveness, infiltration of inflammatory cells and histamine levels in the airways. Furthermore, as compared to OVA-control rats, allergen-induced elevated levels of IgE, nitrites, nitric oxide, and pro-inflammatory mediators, including TNF-α, IL-1β, LTD-4, and Th2-cytokines, particularly, IL-4, IL-5 were remarkably reduced in both bronchoalveolar lavage fluid and blood. These findings are supported by significant protection offered by various treatments against OVA-induced airway inflammation and mast cell degranulation in mesenteric tissues. Further, In-silico molecular docking studies performed to determine inhibitory potential of solasodine at IL-4 and IL-5, demonstrated strong affinity of phytocompound for these receptors than observed with antagonists previously reported. Results of current study imply that solasodine has therapeutic promise in allergic asthma, presumably due to its ability to prevent mast cell degranulation and consequent generation of histamine and Th2-associated cytokines in airways.

Investigation of the mechanisms and experimental verification of Shao yao gan cao decoction against Sphincter of Oddi Dysfunction via systems pharmacology

This study explored the chemical and pharmacological mechanisms of Shao Yao Gan Cao decoction (SYGC) in the treatment of Sphincter of Oddi Dysfunction (SOD) through ultra-high-performance liquid chromatography coupled with Quadrupole Exactive-Orbitrap high-resolution mass spectrometry (UHPLC-Q Exactive-Orbitrap HR-MS), network pharmacology, transcriptomics, molecular docking and in vivo experiments. First, we identified that SYGC improves SOD in guinea pigs by increased c-kit expression and decreased inflammation infiltration and ring muscle disorders. Then, a total of 649 SOD differential genes were found through RNA sequencing and mainly enriched in complement and coagulation cascades, the B cell receptor signaling pathway and the NF-kappa B signaling pathway. By combining UHPLC-Q-Orbitrap-HRMS with a network pharmacology study, 111 chemicals and a total of 52 common targets were obtained from SYGC in the treatment of SOD, which is also involved in muscle contraction, the B cell receptor signaling pathway and the complement system. Next, 20 intersecting genes were obtained among the PPI network, MCODE and ClusterOne analysis. Then, the molecular docking results indicated that four active compounds (glycycoumarin, licoflavonol, echinatin and homobutein) and three targets (AURKB, KIF11 and PLG) exerted good binding interactions, which are also related to the B cell receptor signaling pathway and the complement system. Finally, animal experiments were conducted to confirm the SYGC therapy effects on SOD and verify the 22 hub genes using RT-qPCR. This study demonstrates that SYGC confers therapeutic effects against an experimental model of SOD via regulating immune response and inflammation, which provides a basis for future research and clinical applications.

Exogenous IL-13 exacerbates Leishmania major infection and abrogates acquired immunity to re-infection

Cutaneous leishmaniasis is a major global health issue, affecting more than 88 countries with 0.7-1.2 million new cases per year. T helper polarization plays a significant role in disease outcome, with Th1 responses being associated with resistance and Th2 responses being associated with susceptibility. IL-13 is an important Th2 cytokine with structural and functional similarities to IL-4. In this study, we demonstrate that administering exogenous IL-13 to Leishmania major-infected BALB/c mice increases parasite load in the infected paw and decreases tissue levels of the key Th1/Th2 cytokines IFN-γ and IL-4, respectively. Infecting BALB/c mice with a low dose of L. major has previously been shown to confer resistance to re-infection with a higher dose. In this study, we demonstrate that administration of exogenous IL-13 early in the course of the initial low-dose infection abrogates acquired resistance to high-dose re-infection, as measured by infected paw thickness.

Anti-Irritant Strategy against Retinol Based on the Genetic Analysis of Korean Population: A Genetically Guided Top-Down Approach

Retinol, one of the most powerful cosmetic materials for anti-aging supported by a solid scientific background, exhibits a wide range of type and severity of irritation while showing limited user compliance. The lack of understanding of the mechanism of retinol-induced irritation has been the main hurdle in the development of anti-irritation strategies. Here, we identified 30 genetic markers related to the susceptibility to retinol-induced irritation in the Korean population. Based on the genetic analysis, a novel formula against retinol-induced irritation was developed, which mitigated the molecular pathogenesis—as indicated by the genetic markers—of the retinol-induced irritation. In human tests, this formula effectively decreased retinol-induced irritation. Furthermore, a polygenic risk score model for irritation was constructed and validated. Our comprehensive approach for the analysis of retinol-induced irritation will not only aid the development of anti-irritation strategies to ensure higher user compliance but also contribute to improving the current knowledge about the biological effects of retinoids.

Immunological role of keratinocytes in leishmaniasis

Following inoculation of Leishmania, a protozoan parasite, into the skin of a mammal, the epidermal keratinocytes recognize the parasite and influence the local immune response that can give rise to different outcomes of leishmaniasis. The early keratinocyte-derived cytokines and keratinocytes-T cells interactions shape the anti-leishmanial immune responses that contribute to the resistance or susceptibility to leishmaniasis. The keratinocyte-derived cytokines can directly potentiate the leishmanicidal activity of monocytes and macrophages. As keratinocytes express MHC-II and enhance the expression of costimulatory molecules, these cells act as antigen-presenting cells (APCs) in cutaneous leishmaniasis (CL). Depending on the epidermal microenvironment, the keratinocytes induce various types of effector CD4⁺ T cells. Keratinocyte apoptosis and necrosis have been also implicated in ulceration in CL. Further, keratinocytes contribute to the healing of Leishmania-related cutaneous wounds. However, keratinocyte-derived IL-10 may play a key role in the development of post-kala-azar dermal leishmaniasis (PKDL). In this review, a comprehensive discussion regarding the multiple roles played by keratinocytes during leishmaniasis was provided, while highlighting novel insights concerning the immunological and pathological roles of these cells.

Unravelling the unsolved paradoxes of cytokine families in host resistance and susceptibility to Leishmania infection

Leishmaniasis is a neglected disease caused by protozoan parasites of the genus Leishmania. Successful clearance of Leishmania relies on a robust human immune response and various cytokines have been implicated in resistance and susceptibility to Leishmania infection. Accordingly, various immunotherapeutic approaches involving cytokines and cytokine receptors are being considered as novel avenues of treatment given the limited efficacy of current anti-leishmanial drugs. These approaches target canonical T helper (Th)1/Type 1 cytokines as intended mediators of host-protection to infection whilst concomitantly suppressing Th2/Type 2 cytokines and their anticipated disease-promoting roles. However, the use of cytokine and cytokine receptor gene-deficient mice over the years has challenged this simplistic view of Th1/Type 1-mediated resistance and Th2/Type 2-mediated susceptibility. Indeed, contribution to susceptibility vs resistance is only a partial consequence to cytokine action as the overall response is multi-faceted due to the pleiotropic, redundant, antagonistic and synergistic action of cytokines and interactions with immune cells in the diseased state. Notably, while the responses of certain cytokines are selectively host-protective or characteristic disease-enhancers, some ligands exert a response depending on the parasite-species initiating infection. Paradoxically, others play dual or contradictory roles in different Leishmania immunopathologies. Hence, cytokines in disease is an unsolved paradox and a comprehensive knowledge of cytokine interplay is important to guide the development of novel immunotherapeutics against leishmaniasis. In this review, we characterize various cytokine families in persistence and clearance of the Leishmania parasite and particularly elucidate unsolved cytokine puzzles in leishmaniasis based on information acquired from "gain of knowledge by loss of function" studies in cytokine and cytokine receptor gene-deficient mice.

Antileishmanial activity of a new chloroquine analog in an animal model of Leishmania panamensis infection

Leishmania panamensis is a relevant causative agent of tegumentary leishmaniasis in several Latin American countries. Available antileishmanial drugs have several limitations including relatively high toxicity, difficult administration, high production costs and the emergence of resistance in circulating strains. Therefore, the identification of new molecules as potential therapeutics for leishmaniasis is of great relevance. Here, we developed a murine model of L. panamensis infection and evaluated the effect of a new compound in vivo. After treatment of animals with the compound, we observed a significant reduction of inflammation and parasite load at the inoculation site, in a dose-dependent manner. We observed a reduction in IL-10 production by popliteal lymph nodes cells of infected mice. These results pave the way for future evaluation of this compound as a potential antileishmanial drug or as a suitable scaffold for lead optimization strategies.

Can We Harness Immune Responses to Improve Drug Treatment in Leishmaniasis?

Leishmaniasis is a vector-borne parasitic disease that has been neglected in priority for control and eradication of malaria, tuberculosis, and HIV/AIDS. Collectively, over one seventh of the world’s population is at risk of being infected with 0.7–1.2 million new infections reported annually. Clinical manifestations range from self-healing cutaneous lesions to fatal visceral disease. The first anti-leishmanial drugs were introduced in the 1950′s and, despite several shortcomings, remain the mainstay for treatment. Regardless of this and the steady increase in infections over the years, particularly among populations of low economic status, research on leishmaniasis remains under funded. This review looks at the drugs currently in clinical use and how they interact with the host immune response. Employing chemoimmunotherapeutic approaches may be one viable alternative to improve the efficacy of novel/existing drugs and extend their lifespan in clinical use.

Th1-Th2 Cross-Regulation Controls Early Leishmania Infection in the Skin by Modulating the Size of the Permissive Monocytic Host Cell Reservoir

The impact of T helper (Th) 1 versus Th2 immunity on intracellular infections is attributed to classical versus alternative activation of macrophages leading to resistance or susceptibility. However, observations in multiple infectious settings demonstrate deficiencies in mediators of Th1-Th2 immunity, which have paradoxical or no impact. We report that prior to influencing activation, Th1/Th2 immunity first controls the size of the permissive host cell reservoir. During early Leishmania infection of the skin, IFN-γ- or STAT6-mediated changes in phagocyte activation were counteracted by changes in IFN-γ-mediated recruitment of permissive CCR2⁺ monocytes. Monocytes were required for early parasite expansion and acquired an alternatively activated phenotype despite the Th1 dermal environment required for their recruitment. Surprisingly, STAT6 did not enhance intracellular parasite proliferation, but rather modulated the size and permissiveness of the monocytic host cell reservoir via regulation of IFN-γ and IL-10. These observations expand our understanding of the Th1-Th2 paradigm during infection.

Inflammatory Dendritic Cells, Regulated by IL-4 Receptor Alpha Signaling, Control Replication, and Dissemination of Leishmania major in Mice

Leishmaniasis is a vector-borne disease caused by Leishmania parasites. Macrophages are considered the primary parasite host cell, but dendritic cells (DCs) play a critical role in initiating adaptive immunity and controlling Leishmania infection. Accordingly, our previous study in CD11c^creIL-4Rα^−/lox mice, which have impaired IL-4 receptor alpha (IL-4Rα) expression on CD11c⁺ cells including DCs, confirmed a protective role for IL-4/IL-13-responsive DCs in replication and dissemination of parasites during cutaneous leishmaniasis. However, it was unclear which DC subset/s was executing this function. To investigate this, we infected CD11c^creIL-4Rα^−/lox and control mice with L. major GFP⁺ parasites and identified subsets of infected DCs by flow cytometry. Three days after infection, CD11b⁺ DCs and CD103⁺ DCs were the main infected DC subsets in the footpad and draining lymph node, respectively and by 4 weeks post-infection, Ly6C⁺ and Ly6C⁻ CD11b⁺ DCs were the main infected DC populations in both the lymph nodes and footpads. Interestingly, Ly6C⁺CD11b⁺ inflammatory monocyte-derived DCs but not Ly6C⁻CD11b⁺ DCs hosted parasites in the spleen. Importantly, intracellular parasitism was significantly higher in IL-4Rα-deficient DCs. In terms of DC effector function, we found no change in the expression of pattern-recognition receptors (TLR4 and TLR9) nor in expression of the co-stimulatory marker, CD80, but MHCII expression was lower in CD11c^creIL-4Rα^−/lox mice at later time-points compared to the controls. Interestingly, in CD11c^creIL-4Rα^−/lox mice, which have reduced Th1 responses, CD11b⁺ DCs had impaired iNOS production, suggesting that DC IL-4Rα expression and NO production is important for controlling parasite numbers and preventing dissemination. Expression of the alternative activation marker arginase was unchanged in CD11b⁺ DCs in CD11^creIL-4Rα^−/lox mice compared to littermate controls, but RELM-α was upregulated, suggesting IL-4Rα-independent alternative activation. In summary, L. major parasites may use Ly6C⁺CD11b⁺ inflammatory DCs derived from monocytes recruited to infection as “Trojan horses” to migrate to secondary lymphoid organs and peripheral sites, and DC IL-4Rα expression is important for controlling infection.

Leishmania amazonensis resistance in murine macrophages: Analysis of possible mechanisms

Leishmaniasis encompass a group of infectious parasitic diseases occurring in 97 endemic countries where over one billion people live in areas at risk of infection. It is in the World Health Organization list of neglected diseases and it is considered a serious public health problem, with more than 20,000 deaths a year and high morbidity. Infection by protozoa from the genus Leishmania can cause several forms of the disease, which may vary from a self-healing ulcer to fatal visceral infection. Leishmania species, as well as host immune response and genetics can modulate the course of the disease. Leishmania sp are obligatory intracellular parasites that have macrophages as their main host cell. Depending on the activation phenotype, these cells may have distinct roles in disease development, acting in parasite control or proliferation. Therefore, the purpose of this work was to analyze Leishmania amazonensis infection in primary macrophage cells obtained from mice with two distinct genetic backgrounds, ie. different susceptibility to the infection; evaluating the cause for that difference. After infection, peritoneal macrophages from the resistant C3H/He strain presented lower parasite load when compared to susceptible BALB/c macrophages. The same was also true when cells received a Th2 stimulus after infection, but the difference was abrogated under Th1 stimulus. Nitric oxide production and arginase activity was different between the strains under Th1 or Th2 stimulus, respectively, but iNOS inhibition was unable to suppress C3H/He resistance. Hydrogen peroxide production was also higher in C3H/He than BALB/c under Th1 stimulus, but it could not account for differences in susceptibility. These results led us to conclude that, although they have an important role in parasite control, neither NO nor H2O2 production can explain C3H/He resistance to infection. Other studies are needed to uncover different mechanisms of resistance/susceptibility to L. amazonensis.

Aerosol Inhalation-mediated Delivery of an Adeno-associated Virus 5-expressed Antagonistic Interleukin-4 Mutant Ameliorates Experimental Murine Asthma

BACKGROUND

T helper 2 (Th2) lymphocytes and associated interleukin (IL) 4 and IL-13 play crucial roles in asthma pathogenesis. In this study, we explored an adeno-associated virus 5 (AAV5) based gene therapy by delivering truncated IL-4 protein to antagonize IL-4 receptor α chain and interrupt asthmatic signal pathway.

RESULTS

A recombinant adeno-associated virus 5 (AAV5) vector harboring a truncated mouse IL-4 gene (AAV5-mIL-4ΔC22) was prepared. Western blotting showed that the IL-4 mutant protein lacking the C-terminal 22 amino acids was expressed well in AAV5-mIL-4ΔC22 infected 16HBE and BEAS-2B cells. AAV5-drivn green fluorescent protein (AAV5-GFP) served as a control. The biodistribution of vector DNA after AAV5 vector aerosol inhalation was examined by PCR and the result showed that foreign DNA was detectable in the lungs but not in other organs including gonads. The aerosol inhalation-mediated delivery of AAV5-expressed antagonistic IL-4 mutant protein improved the lung function of ovalbumin-induced asthma mice.

CONCLUSIONS

The inhalation of aerosolized AAV5-mIL-4ΔC22 significantly improved the lung function and modulated the immune cell infiltration and associated cytokine expression in the bronchoalveolar lavage fluid (BALF) of ovalbumin-induced asthma mice.

IL-4 Mediated Resistance of BALB/c Mice to Visceral Leishmaniasis Is Independent of IL-4Rα Signaling via T Cells

Previous studies infecting global IL-4Rα^−/−, IL-4^−/−, and IL-13^−/−mice on a BALB/c background with the visceralizing parasite Leishmania donovani have shown that the T helper 2 cytokines, IL-4, and IL-13, play influential but not completely overlapping roles in controlling primary infection. Subsequently, using macrophage/neutrophil-specific IL-4Rα deficient BALB/c mice, we demonstrated that macrophage/neutrophil unresponsiveness to IL-4 and IL-13 did not have a detrimental effect during L. donovani infection. Here we expand on these findings and show that CD4⁺ T cell-(Lck^cre), as well as pan T cell-(iLck^cre) specific IL-4Rα deficient mice, on a BALB/c background, unlike global IL-4Rα deficient mice, are also not adversely affected in terms of resistance to primary infection with L. donovani. Our analysis suggested only a transient and tissue specific impact on disease course due to lack of IL-4Rα on T cells, limited to a reduced hepatic parasite burden at day 30 post-infection. Consequently, the protective role(s) demonstrated for IL-4 and IL-13 during L. donovani infection are mediated by IL-4Rα-responsive cell(s) other than macrophages, neutrophils and T cells.

Directs effects of granulocyte-macrophage colony stimulating factor (GM-CSF) on adaptive immunogenesis

Background: We studied direct effects of human granulocyte-macrophage colony stimulating factor (GM-CSF) on phenotypical characteristics and cytokine-production of non-activated and activated human monocytes/macrophages (Mc/Mphs) and T cells.Methods: Purified Mc/Mphs were activated by bacterial lipopolysaccharide (LPS, 1 μg/ml) for 24 h, while T cells were activated by particles conjugated and antibodies (Abs) against human CD2, CD3, and CD28 for 48 h.Results: GM-CSF treatment (0.01-10 ng/ml) was shown to reduce percentages of CD197 (CCR7)-positive cells in non-activated Mph cultures, without affecting significantly CD14⁺ (LPS co-receptor), CD16⁺ (FcγRIII, low-affinity Fc-receptor), CD119⁺ (interferon-gamma receptor 1), and CD124⁺ (IL4 receptor α-subunit) cells. In addition, GM-CSF reduced relative numbers of CD197⁺ cells, as well as CD14⁺, CD16⁺, and CD119⁺ cells in activated Mph cultures without affecting CD124⁺ cell distribution. GM-CSF at the highest dose of 10 ng/ml enhanced TNF-α and IL-6 (but not IL-1β and IL-10) production in activated Mc/Mphs. In activated T cell cultures, GM-CSF at 0.1-1.0 ng/ml augmented CD38⁺ cell numbers in naïve СD45RA⁺/СD197⁺ and central memory СD45RA^-/СD197⁺ cell subsets, with no effect on effector СD45RA^-/СD197^- and terminally differentiated effector СD45RA⁺/СD197^- cells. GM-CSF at a low dose (0.01 ng/ml) down-regulated INF-γ production, while at a high dosage (10.0 ng/ml) up-regulated IL-2 and IL-4 production.Conclusion: In general, the results suggest that GM-CSF is able to facilitate the implication of both Mph and T cells in the adaptive immunogenesis.

Feasibility Analysis of Interleukin-13 as a Target for a Therapeutic Vaccine

BACKGROUND

The development of therapeutic vaccines requires thorough knowledge of potential hazards associated with long-term inactivation of self-proteins. Among potential targets, interleukin 13 (IL-13) merits consideration, as monoclonal antibodies disrupting IL-13 signaling are proving to be exceedingly effective in common conditions such as atopic dermatitis.

OBJECTIVE

Given the mass publication of scientific data, an appraisal of safety aspects is challenging.

METHODS

We here provide a three-fold approach to survey clinically relevant information on off-target effects, both adverse and beneficial, that may potentially be encountered in patients undergoing long-term IL-13 inactivation. First, we review non-clinical data in vivo and in vitro. Second, we summarize safety data accumulating from patients dosed with anti-IL-13 drugs. Third, we exploit human mutation data as well as emerging large-scale genetic datasets (global exome data from 60,000 patients) to obtain information on any association of IL-13-inactivating genetic variants with disease states. In addition, we: (1) dissect the precise efficacy signals obtained with various drugs targeting IL-13 and/or IL-4, and (2) summarize unintended, but potentially beneficial effects of prolonged IL-13 inactivation on several functional systems.

RESULTS

Prolonged repression of IL-13 in several thousand patients so far has not uncovered any non-redundant functions of IL-13 in immune defense. Furthermore, missense mutations in the key genes IL-13, IL-13Rα1, IL-13Rα2, IL-4, IL-4Rα are common, while no case reports have been published on any immune deficiency or increased risk of neoplastic disease associated with such mutations, suggesting that these genes do not harbor non-redundant roles in adult outbred humans. In terms of efficacy, data from clinically used drugs strongly suggest that targeting IL-13 only, as opposed to IL-13 and IL-4, may be effective in eczema while being more selective. Importantly, several lines of evidence suggest that inhibition of IL-13 may in fact harbor potentially beneficial effects on non-targeted systems, including glucose metabolism, hepatic fibrosis, and atherosclerosis, suggesting that respective outcomes should be systematically captured in patients dosed with IL-13 interfering drugs. Collectively, available evidence suggests that IL-13 may fulfill safety requirements required for the target of a therapeutic vaccine.