Reduced IL-12 level correlates with decreased IFN-gamma secreting T cells but not natural killer cell activity in asthmatic children

TLR9-IL-2 axis exacerbates allergic asthma by preventing IL-17A hyperproduction

Allergic asthma is one of most famous allergic diseases, which develops lung and airway inflammation. Recent studies have revealed the relationship between the pathology of allergic asthma and the increase of host-derived DNA in inflamed lung, but the role of the DNA-recognizing innate immune receptor for the inflammation is unknown well. Here we investigated the role of Toll-Like Receptor 9 in the pathogenesis of allergic asthma without synthesized CpG-ODNs. To examine that, we analyzed the pathology and immunology of house-dust-mite (HDM)-induced allergic asthma in Tlr9^–/– mice and TLR9-inhibitory-antibody-treated mice. In Tlr9^–/– mice, airway hyperresponsiveness (AHR) and the number of eosinophils decreased, and production of the Th2 cytokines IL-13, IL-5, and IL-4 was suppressed, compared with in wild-type mice. Interestingly, unlike Th2 cytokine production, IL-17A production was increased in Tlr9^–/– mice. Furthermore, production of IL-2, which decreases IL-17A production, was reduced in Tlr9^–/– mice. Blockade of TLR9 by treatment with TLR9-inhibitory-antibody, NaR9, effectively suppressed the development of allergic asthma pathology. IL-17A production in NaR9-treated mice was enhanced, which is comparable to Tlr9^-/- mice. These results suggest that the TLR9–IL-2 axis plays an important role in Th2 inflammation by modulating IL-17A production in HDM-induced allergic asthma and that targeting of TLR9 might be a novel therapeutic method for allergic asthma.

Unique cytokine secretion profile in children with both type I diabetes and asthma distinct from that of solely diabetic or asthmatic children

Asthma and type I diabetes are major causes of chronic illness in childhood which, according to the current paradigm, have mutually antagonistic immunopathologies. Nonetheless, the disorders appear to preferably coexist both on population and individual levels. To assess whether children with asthma and type I diabetes might have a common immunoregulatory defect. The spontaneous and anti-CD3+ anti-CD28-stimulated cytokine production patterns by peripheral blood mononuclear cells of 13 children with both asthma and diabetes, nine children with diabetes, 11 children with asthma and nine healthy children were assessed using cytometric bead assay. The spontaneous production of IFN-gamma, TNF-alpha and IL-10 by mononuclear cells in children with both asthma and diabetes was elevated compared to the other study groups (p=0.02, p=0.001 and p=0.04, respectively). Stimulation in vitro increased IL-10 secretion in solely diabetic (p=0.008), asthmatic (p=0.008) and healthy children (p=0.01), but not in children with both diseases (p=0.22). Children suffering from both diabetes and asthma display a unique cytokine secretion pattern, distinct from those of solely diabetic, asthmatic and healthy children. In particular, these children appear to have a defect in regulation of IL-10 secretion.

Viral infections, cytokine dysregulation and the origins of childhood asthma and allergic diseases

BACKGROUND

The origins of asthma and allergic disease begin in early life for many individuals. It is vital to understand the factors and/or events leading to their development.

METHODS

The Childhood Origins of Asthma project evaluated children at high risk for asthma to study the relationships among viral infections, environmental factors, immune dysregulation, genetic factors, and the development of atopic diseases. Consequently wheezing illnesses, viral respiratory pathogen identification, and in vitro cytokine response profiles were comprehensively evaluated from birth to 3 years of age, and associations of the observed phenotypes with genetic polymorphisms were investigated.

RESULTS

For the entire cohort, cytokine responses did not develop according to a strict T helper cell 1 or T helper cell 2 polarization pattern during infancy. Increased cord blood mononuclear cell phytohemagglutin-induced interferon-gamma responses of mononuclear cells were associated with decreased numbers of moderate to severe viral infections during infancy, especially among subjects with the greatest exposure to other children. In support of the hygiene hypothesis, an increased frequency of viral infections in infancy resulted in increased mitogen-induced interferon-gamma responses at 1 year of age. First year wheezing illnesses caused by respiratory viral infection were the strongest predictor of subsequent third year wheezing. Also, genotypic variation interacting with environmental factors, including day care, was associated with clinical and immunologic phenotypes that may precede the development of asthma.

CONCLUSIONS

Associations between clinical wheezing, viral identification, specific cytokine responses and genetic variation provide insight into the immunopathogenesis of childhood asthma and allergic diseases.

Current and emerging nonsteroidal anti-inflammatory therapies targeting specific mechanisms in asthma and allergy

Today inhaled corticosteroids (ICS) are regarded as the first-line controller anti-inflammatory treatment in the management of asthma. However, there is an increasing awareness of the risk of long-term adverse effects of ICS and that asthma is not only an organ-specific disease but also a systemic and small airway disease. This thinking has called for systemic treatment alternatives to treat asthma targeting more disease-specific mechanisms without influencing normal physiologic functions. Blocking of disease-specific mediators is a mechanism utilized by anti-leukotrienes and anti-immunoglobulin E treatment, each proven to be effective in both asthma and allergic rhinitis.Different cytokine-modifying strategies have been tested in clinical trials with variable results, some disappointing and some encouraging. Anti-interleukin (IL)-5 monoclonal antibody treatment effectively reduces the number of eosinophils locally in the airways and in peripheral blood in asthmatic patients. Unfortunately, this marked effect on eosinophils was not associated with an improvement in bronchial hyperresponsiveness and/or symptoms. Clinical trials with a recombinant soluble IL-4 receptor have been somewhat more successful at improving asthma control and allowing reduction of ICS therapy in asthma. Treatment with recombinant IL-12 had an effect on bronchial hyperresponsiveness and eosinophilic response, but was associated with unacceptable adverse effects. Other interesting cytokine-modulating treatments include those targeting IL-9, IL-10, IL-12 and IL-13.Immune-modulating treatment with bacterial antigens represents another strategy, originating from the hypothesis that some bacterial infections guide the immune system towards a T helper (Th) type 1 immune response. Mycobacterium vaccae, Bacille Calmette-Guerin (BCG) and immunostimulatory DNA sequences have all been tested in clinical trials, with encouraging results. Future asthma and allergy treatment will probably include not only one but also two or more disease-modifying agents administered to the same patient.

Genetic approaches to assessing evidence for a T helper type 1 cytokine defect in adult asthma

Recent evidence suggests that deficiency in the Th1 cytokine pathway may underlie the susceptibility to allergic asthma. This study examined whether (1) single-nucleotide polymorphisms exist in the promoter region of the two interleukin (IL)-12 subunit genes in patients with asthma; (2) messenger RNA and protein expressions of signal transducers and activators of transcription, IL-12, IFN-gamma, and their receptors are altered in asthma; and (3) linkage to genes in the Th1 pathway is present in families with asthma in Iceland. The promoter regions of the IL-12 subunit genes were sequenced in 94 patients with asthma and 94 control subjects without asthma. Linkage was examined in 169 families that included over 570 patients with asthma and 950 of their unaffected relatives. The results demonstrate no evidence of linkage to microsatellite markers in close association with genes within the Th1 pathway, and no polymorphism was detected in the promoter regions of the two IL-12 subunit genes in the cohort with asthma patients. Moreover, we found no differences in the messenger RNA or protein expression signals of genes in the IL-12 pathway between the patients and control subjects. We conclude that decrease in Th1 type cytokine response is unlikely to present a primary event in asthma.

Interleukin-12: potential role in asthma therapy

Asthma is an inflammatory disease of the airways leading to significant morbidity and mortality. With advances in the understanding of the molecular and cellular mechanisms involved in the asthmatic response, researchers have identified specific mediators that may be targeted to control the inflammatory state of asthma. The Th2 hypothesis proposes that the inflammation in asthma arises from an imbalance between the two CD4+ T lymphocyte subsets, T helper (Th) type 1 and Th2. Th2 cells release many cytokines that have been shown to regulate the inflammatory response, while the Th1 cytokines counteract this response. The Th1 cytokine, interleukin (IL)-12, has been a target of intense study because it mediates the Th1 response and offers a means of modifying the asthmatic inflammatory response. Numerous murine studies have shown that this cytokine can potently inhibit allergic airway inflammation in asthma. Inhalation of IL-12 has been shown to increase its efficacy in inhibiting allergic inflammation in murine models while decreasing adverse effects seen with systemic administration of this cytokine. However, an initial study of inhaled IL-12 in humans with asthma was terminated because of adverse effects. The use of systemically administered IL-12 in patients with asthma has been limited due to cytokine toxicity. Another treatment option that has the potential of inducing a Th1 cytokine response is the use of IL-12 linked to polyethylene glycol (PEG) moieties. This mode of administration is likely to enhance cytokine delivery to the target organ, while decreasing its toxicity. IL-12 gene therapy has also been examined as a means of suppressing airway hyperreactivity in murine asthma, but its potential in human asthma has not been explored. Several recent studies have investigated the role of CpG DNA motifs as endogenous inducers of IL-12 with encouraging results in both mice and humans. These studies may result in novel Th1- inducing CpG-based immunotherapies for asthma.

Increased serum IL-10/IL-12 ratio in wheezing infants

To investigate the association between various serum markers and atopic symptoms in the first year of life, and to evaluate the prognostic value of these markers for the development of wheezing and skin rash in the second year of life. Data of 86 children on the development of wheezing and skin rash in the first 2 years of life were collected prospectively, making use of parental completed questionnaires, weekly symptom cards, structured interview and physical examination. Serum markers (IL-10, IL-12, IL-13, eotaxin, sE-selectin, sICAM-1, sIL-2R) and total and specific IgE were determined at age 1. Children who developed wheezing in the first year of life had lower serum levels of IL-12 than children without symptoms (median 40.3 pg/ml vs. 49.0 pg/ml, p = 0.01) and a higher serum IL-10/IL-12 ratio (0.41 vs. 0.31, p = 0.001) at age 1. The IL-10/IL-12 ratio increased with an increasing number of wheezing episodes. Levels of sE-selectin in children with wheezing and in children with itchy skin rash in the first year of life were higher than in symptom free children (6.1 ng/ml and 5.9 ng/ml vs. 4.9 ng/ml, p = 0.01 and p = 0.03, respectively). Children who developed wheezing in the second year of life already had increased sICAM-1 levels at age 1. Children who developed wheezing in the first year of life showed a serum cytokine response that is skewed towards a T-helper 2 profile, with lower IL-12 levels and an increased IL-10/IL-12 ratio. Children who developed wheezing in the second year of life had elevated sICAM-1 levels at age 1. Follow-up of the children is needed to evaluate the prognostic value of various serum markers for the development of allergic disease in later childhood.

Intranasal IL-12 produces discreet pulmonary and systemic effects on allergic inflammation and airway reactivity

IL-12 modulates T cell responses between helper T cells Th2 and Th1; however, the therapeutic potential of IL-12 for allergic diseases either directly or as an adjuvant in allergen therapy has been controversial. The role of intranasal IL-12 as an adjuvant in modulating the grass pollen allergen (GAL) therapy-induced systemic immune response and lung-specific inflammation and airway reactivity was examined in this study using a mouse model of established allergic asthma. The effects of intranasal or nebulized IL-12 with or without intranasal anti-IFN-gamma antibody were examined in groups of control and allergen-sensitized or -challenged mice. T cell cytokine patterns, antibody response profiles, pulmonary inflammation and airway reactivity were examined. Intranasal IL-12 was found to be more effective in the Th2-Th1 shifting of immune response and anti-inflammatory activity in the lung compared to nebulized IL-12 at the given doses. Intranasal IL-12 significantly decreased production of IFN-gamma, eotaxin and LTC4/D4/E4 in the lung and decreased eosinophil infiltration, resulting in attenuated airway hyper-responsiveness in GAL-sensitized (GS) mice. In contrast, intranasal IL-12 significantly increased IFN-gamma production in the thoracic lymph node cultures and decreased the IL-5/IFN-gamma ratio, suggesting a Th2-Th1 shift. Also, intranasal IL-12 increased GAL-specific IgG2a antibody response, while the IgE response remained unaffected. The systemic effects of IL-12 were IFN-gamma dependent. IL-12 induces differential expression of its own receptor beta1 and beta2 subunits in the lung tissues to augment IL-12 responsiveness. Together, these results demonstrate that intranasal IL-12 is effective in shifting the systemic immune response in the direction of Th1 in IFN-gamma-dependent manner, while decreasing pulmonary inflammation and airway reactivity independent of IFN-gamma. Thus, intranasal delivery of IL-12 may provide an approach for the treatment of asthma and may be useful as an adjuvant in local nasal immunotherapy (IT) and in asthma.

Developmental changes in interleukin-12-producing ability by monocytes and their relevance to allergic diseases

BACKGROUND

The T helper type-2 (Th2)-dominated situation can be observed in allergic diseases such as asthma or atopic dermatitis. A reduced ability to produce IL-12, which is a key cytokine for the induction of Th1 responses, has been proposed to lead to aberrant Th2 development in these disease conditions.

OBJECTIVE

This study was intended to examine how IL-12-producing ability might associate with allergic diseases as a function of age.

METHODS

IL-12 production by monocytes at various ages was assessed in patients with bronchial asthma and/or atopic dermatitis (n = 100) in comparison with non-allergic control subjects (n = 144). Whole blood cells were stimulated with lipopolysaccharide (LPS) after priming with IFN-gamma, then intracellular cytokine expression of IL-12 and IL-8 as a control cytokine of CD14-positive cells was assessed by flow cytometric analysis.

RESULTS

In the control subjects, the ability of monocytes to produce IL-12 was negligible at birth and gradually increased with advancing age, whereas IL-8 production was intense throughout the human life. At more than 7 years of age, IL-12 production of patients with allergic diseases was significantly lower compared with that of control subjects. The unexpected finding was that infants and children below 6 years of age with allergic diseases tended to produce more IL-12 compared with age-matched controls. In this young group, it was noted that enhanced IL-12 production by monocytes was especially observed in allergic patients with specific IgE antibodies against some food allergens. Significant inverse relationships between serum IgE levels and IL-12-producing ability were found in the teenage and adult groups, but not in the younger children.

CONCLUSION

IL-12 appeared to play different roles in the pathogenesis of allergic diseases between younger and older ages.

Decreased intercellular adhesion molecule-1 (CD54) and L-selectin (CD62L) expression on peripheral blood natural killer cells in asthmatic children with acute exacerbation

BACKGROUND

The capacity of inflammatory cells to adhere involves an array of adhesion molecules, and is critical to the inflammatory responses seen in childhood asthma. We aimed to determine the changes of intercellular adhesion molecule-1 (ICAM-1) and L-selectin expressed on peripheral blood (PB) T lymphocytes and natural killer (NK) cells in asthmatic children with acute exacerbation and after prednisolone therapy.

METHODS

Flow cytometric analysis was performed to determine the expression of ICAM-1 (CD54) and L-selectin (CD62L) on T (CD3+) cells and NK (CD3-/CD56+) cells of PB from children with allergic asthma with acute exacerbation and in a stable condition after prednisolone therapy. Atopic subjects without asthma and age-matched controls were also included for comparison.

RESULTS

Percentages of PB non-CD3, CD56+ NK cells, but not CD3+ T cells, increased in asthmatic children with acute exacerbation, compared to those assessed in a stable condition after a course of prednisolone. However, significant decrease of ICAM-1 (P = 0.01) and L-selectin (P = 0.01) expression on PB NK cells, but not on T cells, were found in children with acute asthma compared to those in a stable condition. NK cells in children with acute asthma showed minimal expression of CD69 and CD25.

CONCLUSIONS

Results suggests that either NK cells expressing ICAM-1 and L-selectin selectively migrated into inflamed lung tissues, or subsets of NK cells not expressing ICAM-1/L-selectin were expanded during acute exacerbation of childhood asthma.

Asthma: future directions

Asthma continues to be a significant health care problem, as reflected by the increasing rise in disease morbidity and mortality. Because steroids are relatively safe, clinically effective, and easy to administer, they remain the gold standard of treatment. After many decades of use, however, it is apparent that inhaled corticosteroids have failed to halt the progression of the asthma epidemic. Newer, more effective drugs are being developed to combat this disease, and the interest in developing new medications to treat allergic disease and asthma has increased exponentially. The financial burden of asthma has also been a significant motivating factor in the development of new medications. It is estimated that in 1998 the total cost of asthma on society was $11 billion [175]. This consideration has further intensified the quest to develop more effective asthma medications. Table 1 reviews the wide array of drugs currently being investigated. With the development and approval of novel asthma treatments, millions of asthma sufferers will undoubtedly have increased therapeutic options for control of their disease in the near future.