Mycobacterium bovis Bacillus Calmette-Guérin suppresses inflammatory Th2 responses by inducing functional alteration of TSLP-activated dendritic cells

Interleukin-32 induced thymic stromal lymphopoietin plays a critical role in the inflammatory response in human corneal epithelium

Interleukin (IL)-32, a novel cytokine, participates in a variety of inflammatory disorders. Thymic stromal lymphopoietin (TSLP) plays important roles in mucosal epithelial cells, especially in allergy-induced inflammation, through the TSLP-TSLPR (thymic stromal lymphopoietin receptor) signalling pathway. However, the association of IL-32 with TSLP on the ocular surface remains unclear. The present work aimed to assess the functional association of IL-32 with TSLP in the control of pro-inflammatory cytokine levels in the corneal epithelium. Human corneal tissue specimens and human corneal epithelial cells (HCECs) were administered different concentrations of IL-32 in the presence or absence of various inhibitors to assess TSLP levels and localization, as well as the molecular pathways that control pro-inflammatory cytokine production. TSLP mRNA levels were determined by real time RT- PCR, while protein levels were quantitated by ELISA and immunohistochemical staining. TSLP protein expression was examined in donor corneal epithelium samples. IL-32 significantly upregulated TSLP and pro-inflammatory cytokines (TNFα and IL-6) in HCECs at the gene and protein levels. The production of pro-inflammatory molecules by IL-32 was increased by recombinant TSLP. Interestingly, both NF-κB (quinazoline) and caspase-1 (VX-765) inhibitors suppressed the IL-32-related upregulation of pro-inflammatory cytokines (TNFα and IL-6). These findings demonstrate that IL-32 and IL-32-induced-TSLP are critical cytokines that participate in inflammatory responses through the caspase-1 and NF-κB signalling pathways in the corneal epithelium, suggesting new molecular targets for inflammatory diseases of the ocular surface. The effects of IL-32 on cell proliferation and apoptosis were investigated by MTT assays and RT-PCR,respectively. The results demonstrated that IL-32 inhibits cells apoptosis in HCECs.

Enhanced expression of PD-L1 and IFN-γ on dendritic cells is associated with BCG-induced Th2 inhibition

Accumulating evidence indicates that the exposure to Mycobacterium bovis bacillus Calmette-Guérin (BCG) prevents the development of allergy and the airway dendritic cells (DCs) may be involved in this protective effect. However, studies to better characterize the specific interactions between BCG and DCs and their role in this mycobacteria-mediated Th2 cell suppression are still ongoing. This study aimed to evaluate the effect of the neonatal BCG vaccination in the innate immune response in a mouse model of ovalbumin (OVA)-induced airway inflammation. BCG treated neonatal BALB/c mice were sensitized and challenged with aerosolized OVA. Twenty-four hours after the last challenge, samples were collected for analysis. The intranasal BCG treatment inhibited the allergic Th2-response by decreasing the allergen-induced eosinophilic inflammation, EPO activity, CCL11, IL-25, TSLP, IL-4 and IL-5 lung levels, and serum levels of IgE. Mycobacteria treatment increased lung levels of IL-10 and TGF-β, and the TLR2 and TLR4 expressions by pulmonary CD11c⁺CD103⁺CD8α⁺ DCs. Additionally an enhanced expression of PD-L1 was observed besides an increased production of IFN-γ by these cells. These results indicated that neonatal BCG vaccination inhibits key features of allergic airway inflammation, probably by promoting T regulatory immune response via an enhanced expression of TLR2, TLR4 and PD-L1 on DCs.

A single, low dose of a cGMP recombinant BCG vaccine elicits protective T cell immunity against the human respiratory syncytial virus infection and prevents lung pathology in mice

Human respiratory syncytial virus (hRSV) is a major health burden worldwide, causing the majority of hospitalizations in children under two years old due to bronchiolitis and pneumonia. HRSV causes year-to-year outbreaks of disease, which also affects the elderly and immunocompromised adults. Furthermore, both hRSV morbidity and epidemics are explained by a consistently high rate of re-infections that take place throughout the patient life. Although significant efforts have been invested worldwide, currently there are no licensed vaccines to prevent hRSV infection. Here, we describe that a recombinant Bacillus Calmette-Guerin (BCG) vaccine expressing the nucleoprotein (N) of hRSV formulated under current good manufacture practices (cGMP rBCG-N-hRSV) confers protective immunity to the virus in mice. Our results show that a single dose of the GMP rBCG-N-hRSV vaccine retains its capacity to protect mice against a challenge with a disease-causing infection of 1×10⁷ plaque-forming units (PFUs) of the hRSV A2 clinical strain 13018-8. Compared to unimmunized infected controls, vaccinated mice displayed reduced weight loss and less infiltration of neutrophils within the airways, as well as reduced viral loads in bronchoalveolar lavages, parameters that are characteristic of hRSV infection in mice. Also, ex vivo re-stimulation of splenic T cells at 28days post-immunization activated a repertoire of T cells secreting IFN-γ and IL-17, which further suggest that the rBCG-N-hRSV vaccine induced a mixed, CD8⁺ and CD4⁺ T cell response capable of both restraining viral spread and preventing damage of the lungs. All these features support the notion that rBCG-N-hRSV is a promising candidate vaccine to be used in humans to prevent the disease caused by hRSV in the susceptible population.

The expanding role of IL-7 and thymic stromal lymphopoietin as therapeutic target for rheumatoid arthritis

INTRODUCTION

The discovery of IL-7 and thymic stromal lymphopoietin (TSLP) has been a major step in the understanding of arthritis. IL-7 amplifies the inflammation induced by other cytokines, primarily TNF. In animal models of arthritis, inhibition of IL-7 limits inflammation and joint erosion. TSLP is an IL-7-like cytokine that triggers dendritic cell-mediated Th2-type inflammatory responses and is considered as a master switch for allergic inflammation. TSLP is a downstream molecule of TNF-α and as such may be involved in the pathophysiology of inflammatory arthritis.

AREAS COVERED

This review summarizes current knowledge of the role of IL-7 and TSLP derived from both animal models and studies in patients with rheumatoid arthritis (RA). The emergence of IL-7 blockade as a future therapy in RA is highlighted, along with the potential goals and limitations of this therapeutic approach. The write-up also highlights the functional capacities of TSLP in arthritis.

EXPERT OPINION

Evidences suggest important roles for IL-7 and TSLP in the pathogenesis of RA and can be viewed as potential therapeutic targets. Regulation of these at genetic level is a promising investigational area. Given the difficulty in reconstituting T cells in patients with RA, therapeutic approaches that minimize the elimination of T cells are likely to be more desirable.

Allergen-specific immunotherapy in asthmatic children: from the basis to clinical applications

Atopic asthma in childhood with the tendency to persist into adult life is an important issue in pediatrics. Allergen-specific immunotherapy (SIT) is the only curative treatment option for these children, being directed to the causes of the disease. The Th2 phenotype is a predominant immunological pattern in atopic asthma and SIT leads to apoptosis/anergy of T cells and induces immune-regulatory responses and immune deviation towards Th1. Many factors can affect the safety and efficacy of SIT, such as pattern of sensitization, allergy vaccine (allergen extracts, adjuvants and conjugated molecules), route of administration (subcutaneous or sublingual) and different treatment schedules. Overall, asthma symptoms and medication scores usually decrease following a SIT course and the most common observed side effects are restricted to local swelling, erythema and pruritus. Compared with conventional pharmacotherapy, SIT may be more cost effective, providing a benefit after discontinuation and a steroid-sparing effect. In addition, it can prevent new sensitizations in monosensitized asthmatic children. Microbial supplements such as probiotics, immunomodulatory substances like anti-IgE/leukotrienes, antibodies and newer allergen preparations such as recombinant forms have been tested to improve the efficacy and safety of SIT with inconclusive results. In conclusion, SIT provides an appropriate solution for childhood asthma that should be employed more often in clinical practice. Further studies are awaited to improve current knowledge regarding the mechanisms behind SIT and determine the most appropriate materials and schedule of immunotherapy for children with asthma.

The contribution of non-conventional T cells and NK cells in the mycobacterial-specific IFNγ response in Bacille Calmette-Guérin (BCG)-immunized infants

BACKGROUND

The Mycobacterium bovis Bacille Calmette-Guérin (BCG) vaccine is given to >120 million infants each year worldwide. Most studies investigating the immune response to BCG have focused on adaptive immunity. However the importance of TCR-gamma/delta (γδ) T cells and NK cells in the mycobacterial-specific immune response is of increasing interest.

METHODS

Participants in four age-groups were BCG-immunized. Ten weeks later, in vitro BCG-stimulated blood was analyzed for NK and T cell markers, and intracellular IFNgamma (IFNγ) by flow cytometry. Total functional IFNγ response was calculated using integrated median fluorescence intensity (iMFI).

RESULTS

In infants and children, CD4 and CD4-CD8- (double-negative (DN)) T cells were the main IFNγ-expressing cells representing 43-56% and 27-37% of total CD3+ IFNγ+ T cells respectively. The iMFI was higher in DN T cells compared to CD4 T cells in all age groups, with the greatest differences seen in infants immunized at birth (p=0.002) or 2 months of age (p<0.0001). When NK cells were included in the analysis, they accounted for the majority of total IFNγ-expressing cells and, together with DN Vδ2 γδ T cells, had the highest iMFI in infants immunized at birth or 2 months of age.

CONCLUSION

In addition to CD4 T cells, NK cells and DN T cells, including Vδ2 γδ T cells, are the key populations producing IFNγ in response to BCG immunization in infants and children. This suggests that innate immunity and unconventional T cells play a greater role in the mycobacterial immune response than previously recognized and should be considered in the design and assessment of novel tuberculosis vaccines.

Advances in understanding respiratory syncytial virus infection in airway epithelial cells and consequential effects on the immune response

This article reviews aspects of respiratory syncytial virus (RSV) infection in airway epithelial cells (AECs), including cytopathogenesis, entry, replication and the induction of immune response to the virus, including a new role for thymic stromal lymphopoietin in RSV immunopathology.

Thymic stromal lymphopoietin: a promising therapeutic target for allergic diseases

Thymic stromal lymphopoietin (TSLP), an interleukin 7-like cytokine, can trigger dendritic cell (DC)-mediated T-helper type 2 (Th2) inflammatory responses. Recent evidence demonstrates that cytokines TSLP and OX40 (CD134)/OX40 ligand seem to be important players in the maintenance of Th2 memory pool in the pathogenesis of asthma. Accumulating data reveal that the pathogenic T cells involved in asthma are likely to be inflammatory Th2 cells. TSLP is involved in the development of asthma through crosstalk with nuclear factor NF-ĸB. Progression of skin fibrosis in atopic dermatitis occurs via TSLP/TSLP receptor. TSLP-mediated dermal inflammation aggravates experimental allergic asthma. Also, TSLP polymorphisms are associated with susceptibility to asthma, atopic dermatitis, and eczema herpeticum. These findings suggest a master switch of TSLP in the initiation of allergic and adaptive inflammation through innate pathways at the epithelial cell-DC interface. The TSLP pathway is therefore a promising target for immunotherapy of allergic diseases.

Th2 responses in OVA-sensitized BALB/c mice are down-modulated by Mycobacterium bovis BCG treatment

Objective

This study aimed to determine whether Mycobacterium bovis Bacillus Calmette-Guérin (BCG) treatment can reverse an established allergic airway inflammation in a BALB/c mouse model of ovalbumin (OVA)-induced airway inflammation.

Methods

OVA sensitized BALB/c mice were challenged with aerosolized OVA on days 28 to 30, 34, 41 and 63. Mice were intranasal treated with BCG on days 35 and 42. Twenty-four hours after the last challenge, blood samples were collected to detect anti-OVA immunoglobulin isotypes, and bronchoalveolar lavage (BAL) was harvested for cell count. Additionally, lungs were collected for histological analysis, detection of the eosinophil peroxidase (EPO) activity and measurement of cytokines and CCL11. The expression of CTLA-4, Foxp3 and IL-10 was also determined in lung tissue by flow cytometry.

Results

BCG treatment was able to inhibit an established allergic Th2-response, by decreasing the allergen-induced eosinophilic inflammation, EPO activity, levels of CCL11 and IL-4, serum levels of IgE and IgG1. Mycobacteria treatment increased lung levels of IFN-γ, IL-10 and TGF-β, and expressions of Foxp3 and CTLA-4 in CD4⁺T cells. Additionally, an increased production of IL-10 by CD8⁺ T cells was observed, even though no detectable changes in CD4⁺IL-10⁺ was noticed.

Conclusion

BCG treatment inhibits features of allergic airway inflammation and the results suggest that the mechanism underlying the down-regulatory effects of BCG on OVA-induced airway inflammation appear to be associated with the induction of both Th1 and T regulatory immune responses.

Cellular and molecular mechanisms of TSLP function in human allergic disorders--TSLP programs the "Th2 code" in dendritic cells

Thymic stromal lymphopoietin (TSLP) has been recently implicated as a key molecule for initiating allergic inflammation at the epithelial cell-dendritic cell (DC) interface. In humans, aberrant TSLP expression is observed in allergic tissues, such as lesional skins of atopic dermatitis, lungs of asthmatics, nasal mucosa of atopic rhinitis and nasal polyps, and ocular surface of allergic keratoconjunctivitis. TSLP is produced predominantly by damaged epithelial cells and stimulates myeloid DCs (mDCs). TSLP-activated mDCs can promote the differentiation of naïve CD4(+) T cells into a Th2 phenotype and the expansion of CD4(+) Th2 memory cells in a unique manner dependent on OX40L, one of the tumor necrosis factor superfamily members with Th2-promoting function, and lack of production of IL-12. From a genetic point of view, multiple genome-wide association studies have repeatedly identified the TSLP gene as one of the loci associated with susceptibility to allergic diseases. Thus, TSLP is a rational therapeutic target for the treatment of allergic disorders. Elucidating the mechanisms that regulate TSLP expression and the effects of TSLP on orchestrating the immune response toward a Th2 phenotype is essential for developing anti-TSLP therapy.

OX40 ligand fusion protein delivered simultaneously with the BCG vaccine provides superior protection against murine Mycobacterium tuberculosis infection

Mycobacterium tuberculosis infection claims approximately 2 million lives per year, and improved efficacy of the BCG vaccine remains a World Health Organization priority. Successful vaccination against M. tuberculosis requires the induction and maintenance of T cells. Targeting molecules that promote T-cell survival may therefore provide an alternative strategy to classic adjuvants. We show that the interaction between T-cell-expressed OX40 and OX40L on antigen-presenting cells is critical for effective immunity to BCG. However, because OX40L is lost rapidly from antigen-presenting cells following BCG vaccination, maintenance of OX40-expressing vaccine-activated T cells may not be optimal. Delivering an OX40L:Ig fusion protein simultaneously with BCG provided superior immunity to intravenous and aerosol M. tuberculosis challenge even 6 months after vaccination, an effect that depends on natural killer 1.1(+) cells. Attenuated vaccines may therefore lack sufficient innate stimulation to maintain vaccine-specific T cells, which can be replaced by reagents binding inducible T-cell costimulators.

Treatment of allergic asthma: modulation of Th2 cells and their responses

Atopic asthma is a chronic inflammatory pulmonary disease characterised by recurrent episodes of wheezy, laboured breathing with an underlying Th2 cell-mediated inflammatory response in the airways. It is currently treated and, more or less, controlled depending on severity, with bronchodilators e.g. long-acting beta agonists and long-acting muscarinic antagonists or anti-inflammatory drugs such as corticosteroids (inhaled or oral), leukotriene modifiers, theophyline and anti-IgE therapy. Unfortunately, none of these treatments are curative and some asthmatic patients do not respond to intense anti-inflammatory therapies. Additionally, the use of long-term oral steroids has many undesired side effects. For this reason, novel and more effective drugs are needed. In this review, we focus on the CD4+ Th2 cells and their products as targets for the development of new drugs to add to the current armamentarium as adjuncts or as potential stand-alone treatments for allergic asthma. We argue that in early disease, the reduction or elimination of allergen-specific Th2 cells will reduce the consequences of repeated allergic inflammatory responses such as lung remodelling without causing generalised immunosuppression.

Thymic stromal lymphopoietin plays an adjuvant role in BCG-mediated CD8(+) cytotoxic T cell responses through dendritic cell activation

Although Bacillus Calmette-Guérin (BCG) has historically emerged as a potent adjuvant in cancer immunization through dendritic cell (DC) activation, the efficacy of its antitumor effect has been limited. Therefore, the strategy of adjuvant therapy using BCG needs to be improved by adding enhancers. Here we found that thymic stromal lymphopoietin (TSLP) acts as an enhancer for the BCG-mediated antitumor effect. While BCG-stimulated DCs induced CD8(+) T cell production of IFN-gamma without strong cell expansion, TSLP-stimulated DCs induced robust CD8(+) T cell expansion without high quantities of IFN-gamma production. Notably, DCs stimulated with both BCG and TSLP induced robust expansion of CD8(+) T cells that produced a large amount of IFN-gamma with a potent cytolytic activity related to granzyme B expression. Our data suggest that TSLP is a good adjuvant to enhance the BCG-mediated cytotoxic T cell effect through DC activation, and provide a functional basis for a novel strategy for antitumor immune-based therapy.

The role of thymic stromal lymphopoietin in allergic inflammation and chronic obstructive pulmonary disease

Thymic stromal lymphopoietin (TSLP) primes dendritic cells to promote a Th2 inflammatory response. Its action is mediated by a heterodimeric receptor which consists of the interleukin-7 receptor alpha chain and the TSLP receptor chain (TSLPR). TSLPR resembles the common gamma chain subunit utilized by many type 1 cytokine receptors. Normal epithelial cells, keratinocytes, and stromal cells constitutively express TSLP. Dendritic cells that are activated by TSLP promote the development of CD4(+) T cells into pro-inflammatory Th2 cells. TSLP thus plays a potentially important role in the pathogenesis of allergic inflammation in asthma and atopic dermatitis. TSLP also has direct effects on other types of cells in the bronchial mucosa. It is over-expressed in the bronchial mucosa in chronic obstructive pulmonary disease (COPD), which is traditionally described as a Th1-related disease, as well as severe asthma, which is traditionally described as a Th2-related disease. In this review we will discuss TSLP expression, function, and available and potential mechanisms in both allergic inflammation and COPD.

In vitro end points for the assessment of cellular immune response-modulating drugs

BACKGROUND

The concept of immunotoxicology and the development of a battery of immune-function assays to screen potential immunotoxic compounds have been increasingly used in the past. Immunotoxic outcome generally seems appropriate to evaluate the risk in drug development. Improving this approach is possible, by using methods now available, to study the effect of a chemical compound on the immune system.

OBJECTIVE

The goal of this review is to provide an overview of the current and recent methodologies for testing the immunological effect and immunotoxic risks in drug candidates.

METHODS

The methodological details here discussed include a synthetic description of the immunocompetent cells in cell-mediated immunity and the choice of the most appropriate assay (bioassays, immunoassays, molecular biology techniques, flow cytometry).

CONCLUSION

This review offers an assessment of in vitro models to study the toxic impact of (bio)pharmaceuticals on cellular immune system and aid drug scientists in understanding the significance and the methods to approach immunotoxicology.