Immunoprophylaxis of atopy: light at the end of the tunnel?

Molecular diagnosis for allergen immunotherapy

The extensive use of allergen molecules in birth cohort studies revealed that atopic sensitization is a sequential IgE response to distinct non-cross-reacting molecules from the same allergenic source (ie, molecular spreading), starting with an initiator molecule. This phenomenon reaches different degrees of progression (monomolecular, oligomolecular, and polymolecular) according to the individual atopic propensity and allergen exposure, thus producing an extreme heterogeneity of IgE sensitization profiles in patient populations. In patients with allergic rhinitis, the broader the IgE molecular sensitization profile, the greater is the risk of asthma and other allergic comorbidities, such as oral allergy syndrome. Hence it has been proposed to anticipate immunologic intervention at disease onset (early allergen immunotherapy) or even earlier during the preclinical sensitization stage (allergen immunoprophylaxis). Diagnostic algorithms based on singleplex or multiplex molecular IgE tests allow the discrimination of genuine from cross-reacting sensitization and the selection of the right extracts for allergen immunotherapy composition. Patients with extreme molecular poly-sensitization and greater risk of asthma or other IgE-mediated comorbidities, can be easily identified by means of allergen microarray or macroarray procedures and might benefit from anti-IgE treatment. IgE molecular tests have opened the era of precision allergology, and their routine use should aim at cost-effectiveness, according to the principles of the Choosing Wisely initiative.

Efficacy and safety of sublingual immunotherapy in children

Allergen immunotherapy (AIT) is currently the only available disease-modifying and aetiological treatment of IgE-mediated diseases. Sublingual allergen immunotherapy (SLIT) constitutes the preferred route of administration of AIT for respiratory allergies in Europe. Recently it has also been approved in the US. Further applications are currently under evaluation, such as IgE-mediated food allergy and IgE-mediated atopic dermatitis. The SLIT safety profile is overall favourable, although local adverse events, usually mild, are described. Most of the meta-analyses confirmed the efficacy of SLIT in reducing symptoms and medication intake in children with allergic diseases. AIT, as an immune-modulating treatment, can modify the natural history of the allergic diseases: reduction of the risk of development of asthma and bronchial hyperreactivity in patients with allergic rhinitis, and reduction of the onset of new sensitizations. A great interest is now devoted to the preventive effects of AIT and, consequently, to the optimal time of initiation.

Administration of antibiotics during infancy promoted the development of atopic dermatitis-like skin lesions in NC/Nga mice

This study aimed to determine whether oral antibiotic administration during infancy is associated with the spontaneous development of atopic dermatitis-like skin lesions by modulating intestinal microbiota. Female NC/Nga mice at 3 weeks of age were orally administered kanamycin or polymyxin B. Clinical symptoms, scratching behavior, and serum antibody levels were evaluated. Changes in intestinal microbiota were determined by culture-independent analysis and cultural analysis. The kanamycin-treated mice showed higher clinical scores and scratching frequency than the control mice. IgE levels were significantly higher in the kanamycin-treated mice than in the control mice. Transient changes in intestinal microbiota were observed under kanamycin treatment. Polymyxin B treatment failed to affect scratching behavior. These results suggest that oral administration of kanamycin during infancy promoted the development of atopic dermatitis-like skin lesions in NC/Nga mice and was associated with a transient change in intestinal microbiota.

Are we getting enough allergens?

This paper proposes that reduced allergen exposure is one of the factors underlying the higher risk of IgE-mediated allergic disease in populations with an urbanized, westernized, and affluent lifestyle. This lower allergen exposure results in the failure to induce and maintain immune tolerance to common environmental allergens. The paper summarizes different lines of evidence that may support or contradict this hypothesis and points to areas where more knowledge is needed.

Immunology

The concept of forbidden foods that should not be eaten goes back to the Garden of Eden and apart from its religious meanings it may also have foreshadowed the concept of foods that can provoke adverse reactions. Thus we could say that allergic diseases have plagued mankind since the beginning of life on earth. The prophet Job was affected by a condition that following the rare symptoms described by the Holy Bible might be identified as a severe form of atopic dermatitis (AD). The earliest record of an apparently allergic reaction is 2621 B.C., when death from stinging insects was first described by hieroglyphics carved into the walls of the tomb of Pharaoh Menes depicting his death following the sting of a wasp. In 79 A.D., the death of the Roman admiral Pliny the Elder was ascribed to the SO₂-rich gases emanating from the eruption of Mount Vesuvius. Hippocrates (460–377 B.C.) was probably the first to describe how cow’s milk (CM) could cause gastric upset and hives, proposing dietetic measures including both treatment and prevention for CM allergy.

Immunological mechanisms of sublingual immunotherapy

Administration of allergen-specific immunotherapy by the oral route, sublingual immunotherapy (SLIT), has been shown to be effective, with an improved safety profile compared with subcutaneous administration. However, the precise mechanisms underlying the induction of immune tolerance by SLIT remain unclear. Contact of the allergen with the antigen-presenting cells in oral mucosa is likely to be critical. Mucosal Langerhans cells can capture the allergen and transport it to local lymph nodes, which may favour the induction of T lymphocytes that suppress the allergic response. In addition, the production of blocking IgG4 antibodies and the involvement of mucosal B cells appear to play a role. There is a growing evidence to support the role of regulatory T cells in controlling the development of asthma and allergic disease. Nevertheless, there remains a lack of firm evidence that SLIT induces regulatory T cells, although preliminary in vitro data suggest that SLIT may increase interleukin-10, which has a clear role in suppressing the allergic immune response. Further studies are required to determine the involvement of regulatory T cells, the role of different dendritic cell subsets, mucosal B cells as well as the potential use of adjuvants during SLIT.

Clinical efficacy and safety of preseasonal sublingual immunotherapy with grass pollen carbamylated allergoid in rhinitic patients. A double-blind, placebo-controlled study

BACKGROUND

The aim of this study was to confirm the clinical efficacy and safety of a preseasonal sublingual immunotherapy (SLIT) in a group of allergic patients with seasonal rhinoconjunctivitis with or without mild intermittent or mild persistent asthma. The immunotherapy was administered through the oral mucosa with a monomeric carbamylated allergoid (allergoid SLIT) for grass pollens. A secondary endpoint was to evaluate the effect of the allergoid SLIT on nasal reactivity.

METHODS AND RESULTS

A single-center, randomized, double-blind, placebo-controlled study was performed. Patients were selected and randomly allocated to two groups: one group received active treatment (allergoid SLIT) for 2 years and the other received placebo. Both groups received the necessary drug treatment throughout the trial. Thirty-three outpatients (20 men and 13 women, mean age: 30 years; range: 19-43) attending our center were enrolled in the study. Symptoms and medications were scored on diary cards during the pollen season. An allergen nasal challenge was performed at baseline and after 2 years of SLIT to evaluate nasal reactivity. Because the clinical scores were non-normally distributed, the Mann-Whitney and the Chi-square tests for intergroup comparisons and the Wilcoxon test for intragroup comparisons were used. The results were evaluated after 1 and 2 years of treatment. Between the first and second years of treatment, no changes in the scores for the placebo group were found, while for the active vaccine group significant decreases were found in rhinorrhea (p < 0.03), sneezing (p < 0.03), and conjunctivitis (p < 0.02). Symptom scores after nasal challenge decreased (p < 0.03) after 2 years' treatment. Nasal steroid use significantly decreased in the active treatment group during May and June in both the years of treatment (p < 0.02). Only two mild local adverse events were reported in the active group and none was reported in the placebo group.

CONCLUSIONS

The results of this study show that the allergoid SLIT is safe and effective in decreasing symptom scores and drug use in rhinitic patients allergic to grass pollen.

A differing pattern of association between dietary fish and allergen-specific subgroups of atopy

BACKGROUND

We examined the role of fish intake in the development of atopic disease with particular reference to the possibility of differential effects on allergen-specific subgroups of sensitization.

METHODS

The exposure of interest was parental report of fish intake by children aged 8 years at the 1997 Childhood Allergy and Respiratory Health Study (n = 499). The outcomes of interest were subgroups of atopy: house dust mite (HDM)-pure sensitization [a positive skin-prick test (SPT) > or = 2 mm to Der p or Der f only], ryegrass-pure sensitization (a positive SPT > or = 2 mm to ryegrass only); asthma and hay fever by allergen-specific sensitization.

RESULTS

A significant association between fish intake and ryegrass-pure [adjusted odds ratio (AOR) 0.37 (0.15-0.90)] but not HDM-pure sensitization [AOR 0.87 (0.36-2.13)] was found. Fish consumption significantly decreased the risk for ryegrass-pure sensitization in comparison with HDM-pure sensitization [AOR 0.20 (0.05-0.79)].

CONCLUSIONS

We have demonstrated a differential effect of fish intake for sensitization to different aeroallergens. This may be due to the different timing of allergen exposure during early life. Further investigation of the causes of atopic disease should take into account allergen-specific subgroups.

Impact of sublingual immunotherapy on specific antibody levels in asthmatic children allergic to house dust mites

OBJECTIVE

To evaluate the clinical outcome and changes in allergen-specific antibodies during sublingual immunotherapy (SLIT) in house dust mite (HDM)-allergic asthma patients and to compare levels of allergen-specific antibodies in HDM-allergic patients before and after treatment with that of healthy controls.

METHOD

Thirty-one asthma patients allergic to HDM were studied. Patients in groups I (n=17) and II (n=14) received SLIT with a standardized Dermatophagoides pteronyssinus plus Dermatophagoides farinae 50/50 extract for 6 and 12 months, respectively. A group of healthy children (n=8) were enrolled as controls. Patients in both groups were evaluated at the start and at the end of treatment according to daily symptom and medication scores, lung function and skin prick tests, PC20, blood eosinophil count, and Der-p-1-specific IgE, IgA, IgG1 and IgG4 levels.

RESULTS

Drug consumption decreased significantly in both groups. Furthermore, PC20 and forced expiratory flow between 25 and 75% of vital capacity of patients in group II improved significantly. Although specific IgA, IgG1 and IgG4 levels did not change throughout the treatment period, total eosinophil count and specific IgE decreased significantly in both groups. According to baseline measurements, specific IgA levels of patients in groups I and II were significantly lower than that of controls. This difference disappeared at the end of the treatment period in both groups.

CONCLUSION

SLIT seems to be effective in ameliorating clinical symptoms, drug consumption and bronchial hyperreactivity, and results in downregulation of Der-p-1-specific IgE production. Furthermore, at the end of SLIT, specific IgA levels, which were decreased compared to healthy controls initially, did no longer differ between patients and controls.

Bacillus Calmette-Guérin-induced interleukin-12 did not additionally improve clinical and immunologic parameters in asthmatic children treated with sublingual immunotherapy

OBJECTIVE

To evaluate the effect of bacillus Calmette-Guérin (BCG) as an adjuvant to specific sublingual immunotherapy (SLIT) on the cytokine profile of peripheral blood mononuclear cells (PBMCs) and clinical outcome.

METHODS

Thirty-two children with asthma and rhinitis allergic to house dust mite (HDM) with negative purified protein derivative (PPD) skin test response were enrolled. After a run-in period of 8 weeks, patients were randomized to receive either SLIT only (n=16) or one dose of BCG immunization before initiation of SLIT (n=16) with a standardized Dermatophagoides pteronyssinus (D. pteronyssinus)+D. farinea 50/50 extract. PPD-negative asthmatics (n=5) allergic to HDM receiving inhaled therapy only were included for comparison of cytokine levels in PBMC cultures. Efficacy was assessed both at the end of run-in and 6 months of treatment periods with criteria including symptom, medication and quality-of-life (QoL) scores, IgE levels, lung function, provocation concentration (PC20), eosinophil count and skin prick tests. IL-4, IL-5, IL-10, IL-12, IL-13 and IFN-gamma levels were determined in antigen specifically and polyclonally stimulated PBMC cultures.

RESULTS

Both treatment groups showed significant improvement at the end of 6 months for asthma and rhinitis scores and QoL, number of asthma attacks, amount of beta2-agonists, inhaled and intranasal steroids, blood eosinophil counts and PC20. Interestingly, phytohaemagglutinin (PHA)-stimulated IL-12 and D. pteronyssinus-stimulated IFN-gamma in PBMC were significantly higher in the treatment groups than controls. In addition, IL-12 levels in response to D. pteronyssinus and PHA stimulation were significantly higher in the SLIT+BCG group than the SLIT alone group and controls.

CONCLUSION

The present study demonstrates that successful SLIT is parallel to increased IFN-gamma production by PBMC. Although simultaneous BCG vaccination enhanced IL-12 production, it did not additionally improve the clinical outcome.

Possible modes of allergen-specific sensitization and boosting in an atopic child

Several studies document that allergen-specific IgE levels are boosted by allergen contact via the respiratory tract in allergic patients. Only few data are available on whether other routes of allergen contact have an influence on systemic IgE responses. We report the case of a boy who developed egg allergy after heavy consumption of eggs by the mother during pregnancy and breast feeding. In contrast to other children who outgrow egg allergy during the first years of life, the boy experienced further dramatic increases in hen egg-specific IgE antibodies after prolonged consumption of ostrich eggs containing cross-reactive allergens. IgE antibodies to most of the important respiratory allergens remained either low or not detectable. The dramatic increases in hen egg-specific IgE antibody levels after oral intake of allergens demonstrate that systemic IgE responses in allergic patients can be strongly boosted by allergen contact via routes other than the respiratory tract.

Development of sensitisation or tolerance following repeated OVA inhalation in BALB/cJ mice. Dose-dependency and modulation by the Al(OH)3 adjuvant

Anthropogenically induced exposures may, due to their adjuvant effect, promote development of sensitisation to commonly occurring aeroallergens. No generally accepted model exists for determination of adjuvant effect of airborne substances. Therefore, BALB/cJ mice were exposed for 10 consecutive days with ovalbumin (OVA) solution, 25 mg/l-10 g/l (0.0025-1%) for 20 min/day, with and without the Al(OH)(3) adjuvant (0.5%). Four days after the last aerosol exposure, no OVA specific IgE and only low IgG1 were produced. Subsequent parenteral OVA administration showed that the 10 g/l solution induced full tolerance of the IgE response, whereas only partial tolerance was apparent with 25 mg/l OVA. The Al(OH)(3) adjuvant counteracted development of tolerance that was fully prevented at the 25 mg/l OVA concentration. Development of IgG1 was increased in a concentration-dependent manner with 500 mg/l-10 g/l OVA. No increase occurred at the 25 mg/l level, but addition of Al(OH)(3) increased IgG1 production to the same level as the higher OVA concentrations. Concentrations from 1.25 mg/l to 10 g/l OVA were studied with ten exposures followed by once-weekly aerosol exposure for uptil 6 weeks. In the range from 1.25 mg/l to 10 g/l, IgE production was time- and concentration-dependent. Both the IgE and IgG1 production were markedly promoted by Al(OH)(3). However, with aerosol exposures, the IgE antibody productions were not sufficient to increase the level of inflammatory cells in broncho-alveolar lavage fluid. Overall, this study showed that airborne Al(OH)(3) was able to counteract tolerance and increase specific IgE and IgG1 production.

An oral introduction of intestinal bacteria prevents the development of a long-term Th2-skewed immunological memory induced by neonatal antibiotic treatment in mice

BACKGROUND

Recent epidemiological studies indicate that antibiotic use in infancy may be associated with an increased risk of developing atopy. Our previous work on animals demonstrated that kanamycin use during infancy promotes a shift in the Th1/Th2 balance towards a Th2-dominant immunity.

OBJECTIVE

The first purpose of this study is to clarify whether or not the supplementation of intestinal bacteria can reverse such a Th2-skewed response induced by neonatal antibiotic use. The second objective is to elucidate the contribution of genetic factors to antibiotic-induced immune-deviation.

METHODS

BALB/c or C57BL/6 mice at 3 weeks of age were orally administered 600 microg/day of kanamycin sulphate for seven consecutive days. Thereafter, the mice were inoculated with one type of intestinal bacterial species: Enterococcus faecalis, Lactobacillus acidophilus or Bacteroides vulgatus. Blood samples were collected 10 weeks after the cessation of kanamycin treatment, and the effect of the kanamycin treatment on Th1/Th2 balance was evaluated based on in vivo antibody levels.

RESULTS

A kanamycin-induced elevation of the serum IgE levels was reversed by the supplementation with Enterococcus faecalis, and to a lesser extent by that with Lactobacillus acidophilus. The IgE/IgG2a ratio in the mice supplemented with Enterococcus faecalis significantly decreased in comparison with that in the kanamycin-treated mice without any bacterial supplementation, while such a ratio was enhanced in the mice inoculated with Bacteroides vulgatus. No antibiotic-induced Th2-skewed response was seen in C57BL/6 mice that are genetically biased towards Th1-dominant immunity.

CONCLUSION

These results suggest that adequate probiotic intervention after antibiotic treatment may improve the intestinal ecosystem, and thereby prevent the Th2-shifted immunity induced by neonatal antibiotic use. In addition, the difference of genetic backgrounds also contributes to such an antibiotic-induced Th2-skewed response.

Probiotics: potential pharmaceutical applications

Realisation of the importance of human gut microbiota in health restoration and maintenance has kindled an interest in probiotics. Probiotics are defined as the microbial food supplements, which beneficially affect the host by improving its intestinal microbial balance. Probiotics are the health enhancing functional food ingredients used therapeutically to prevent diarrhea, improve lactose tolerance and modulate immunity. They may also have potential to prevent cancer and lower serum cholesterol levels. Lactobacillus, Bifidobacterium and several other microbial species are perceived to exert such effects by changing the composition of the gut microbiota. However, it is important that exogenously administered bacteria reach and establish themselves in the large intestine in an intact form. The use of non-digestible oligosaccharides ('prebiotics') can fortify intestinal microflora and stimulate their growth. The present review encompasses information regarding the probiotics and their proposed uses. It addresses the concepts of prebiotics and synbiotics, the application of genetic engineering to produce newer probiotics. Finally, the list of commercially available products are reviewed with discussion of questions regarding the reliability, utility and the safety of these products.

Understanding airway wall remodeling in asthma: a basis for improvements in therapy?

Current strategies for the management of asthma focus on suppressing airway inflammation. Other characteristic features of human asthma, such as airway hyperreactivity and the structural changes collectively referred to as airway remodeling, are largely ignored in existing guidelines for monitoring the effectiveness of treatment. Evidence is accumulating that pharmacologic therapy targeting airway wall remodeling may be valuable in treating asthma. However, development of appropriate therapeutic agents will require a better understanding of the pathogenesis of remodeling, which appears to be regulated by a variety of cytokines and growth factors produced by inflammatory, epithelial, and stromal cells. Furthermore, testing the effectiveness of novel agents that specifically target the process of remodeling will require appropriate experimental models, but most currently available animal models of asthma have major limitations. A recently described murine model of chronic human asthma offers considerable potential for dissection of the mechanisms of airway wall remodeling, as well as for investigation of the therapeutic potential of drugs that can modulate chronic inflammation and remodeling.

Suppression of specific and bystander IgE responses in a mouse model of oral sensitization to beta-lactoglobulin

BACKGROUND

Mechanisms of systemic IgE suppression by oral tolerance have been extensively studied, but less is known about oral tolerance induction in mice challenged at mucosal sites. We have previously shown in systemically challenged mice that high-dose tolerance suppressed specific but not bystander IgE. In an attempt to mimic oral tolerance in food-allergic patients, we have investigated how IgE suppression could be induced in mice sensitized orally against beta-lactoglobulin (BLG).

METHODS

Mice were immunized orally against BLG using cholera toxin as adjuvant. Before oral sensitization, mice were administered milk whey proteins, either in the form of a single high-dose gavage, or by prolonged ad libitum administration of various doses.

RESULTS

Orally sensitized mice mounted a BLG-specific IgE response. In contrast to systemically challenged mice, a single high-dose gavage of whey protein given prior to the onset of oral sensitization resulted in the suppression of both specific and bystander IgE. When mice were fed moderate to low doses of milk whey proteins daily ad libitum in the drinking water during 3 weeks prior to oral sensitization, all doses effectively suppressed antigen-specific IgE. However, bystander IgE suppression was observed only at the lowest doses. When mice were tolerized during 4 days instead of 3 weeks, IgE titers remained unchanged.

CONCLUSIONS

In orally sensitized mice, bystander IgE suppression depended on the dose of tolerogen, but also on its mode of administration. Mucosally induced IgE responses were suppressed by a mechanism that was distinct from that operating in the periphery.

BCG infection in allergen-presensitized rats suppresses Th2 immune response and prevents the development of allergic asthmatic reaction

Recent investigations demonstrate that bacille Calmette-Guerin (BCG), a potent inducer of Th1 response, infection prior to allergen sensitization inhibits Th2 immune responses to the allergen. However, it is not clear whether BCG infection in allergen-presensitized rats switches off Th2 response and prevents allergic asthmatic reaction to the subsequent allergen exposure. In this study we investigate whether BCG infection in ovalbumin (OVA)-presensitized Sprague-Dawley rats suppresses airway hyperresponsiveness and eosinophilic inflammation induced by OVA and Th2 cytokine production. BCG infection in OVA-presensitized rats significantly inhibited not only the sensitivity of airway smooth muscle to electrical field stimulation and acetylcholine but also absolute eosinophil counts in bronchoalveolar lavage fluid. As a correlate, interleukin-4 (IL-4) production significantly decreased and interferon-gamma (IFN-gamma) slightly increased, resulting in a markedly decreased ratio of IL-4-IFN-gamma in OVA-presensitized rats with BCG infection. These results indicate that BCG infection in pre-sensitized rats suppresses allergic asthmatic reaction and Th2 immune response. It is possible from these findings that BCG vaccine may be used as an immunomodulating agent for the sensitized host with preestablished Th2 memory.

Importance of intestinal colonisation in the maturation of humoral immunity in early infancy: a prospective follow up study of healthy infants aged 0-6 months

AIM

To evaluate the role of intestinal microflora and early formula feeding in the maturation of humoral immunity in healthy newborn infants.

STUDY DESIGN

Sixty four healthy infants were studied. Faecal colonisation with Bacteroides fragilis group, Bifidobacterium-like, and Lactobacillus-like bacteria was examined at 1, 2, and 6 months of age, and also the number of IgA-secreting, IgM-secreting, and IgG-secreting cells (detected by ELISPOT) at 0, 2, and 6 months of age.

RESULTS

Intestinal colonisation with bacteria from the B fragilis group was more closely associated with maturation of IgA-secreting and IgM-secreting cells than colonisation with the other bacterial genera studied or diet. Infants colonised with B fragilis at 1 month of age had more IgA-secreting and IgM-secreting cells/10(6) mononuclear cells at 2 months of age (geometric mean (95% confidence interval) 1393 (962 to 2018) and 754 (427 to 1332) respectively) than infants not colonised (1015 (826 to 1247) and 394 (304 to 511) respectively); p = 0.04 and p = 0.009 respectively.

CONCLUSIONS

The type of bacteria colonising the intestine of newborns and the timing may determine the immunomodulation of the naive immune system.

Recombinant allergens for diagnosis and therapy of allergic disease

Many of the problems associated with using natural allergenic products for allergy diagnosis and treatment can be overcome with use of genetically engineered recombinant allergens. Over the past 10 years, the most important allergens from mites, pollens, animal dander, insects, and foods have been cloned, sequenced, and expressed. In many cases the three-dimensional allergen structure has been determined and B-cell and T-cell epitopes have been mapped. These studies show that allergens have diverse biologic functions (they may be enzymes, enzyme inhibitors, lipocalins, or structural proteins) and that as a rule the allergen function is unrelated to its ability to cause IgE antibody responses. High-level expression systems have been developed to produce recombinant allergens in bacteria, yeast, or insect cells. Recombinant allergens show comparable IgE antibody binding to their natural counterparts (where available) and show excellent reactivity on skin testing and in in vitro diagnostic tests. Cocktails of recombinant allergens can be formulated with predetermined and uniform allergen levels, which could replace natural allergens and result in the development of innovative, patient-based tests for allergy diagnosis. Recombinant allergens also offer the exciting possibility of developing new forms of allergen immunotherapy, including the use of hypoallergens, allergens coupled to IgE suppressive adjuvants, and peptide-based therapies. The production of recombinant allergens as defined molecular entities makes it feasible to consider the possibility of developing prophylactic allergen vaccines. The introduction of recombinant allergens in research and in clinical trials should lead to significant improvements in allergy diagnosis and treatment.

Mechanisms preventing allergen-induced airways hyperreactivity: role of tolerance and immune deviation

BACKGROUND

Aeroallergens continuously enter the respiratory tract of atopic individuals and provoke the development of asthma characterized by airway hyperreactivity (AHR) and inflammation. By contrast, nonatopic individuals are exposed to the same aeroallergens, but airway inflammation does not develop. However, the mechanisms that prevent allergen-induced respiratory diseases in nonatopic subjects are poorly characterized.

OBJECTIVE

In this study we compared the role of allergen-specific T-cell tolerance and immune deviation in conferring protection against the development of allergen-induced AHR.

METHODS

We exposed mice to intranasal ovalbumin (OVA) to induce T-cell tolerance and examined its effects on the subsequent development of AHR and inflammation.

RESULTS

We demonstrated that exposure of mice to intranasal OVA resulted in peripheral CD4(+) T-cell unresponsiveness that very efficiently prevented not only the development of AHR but also greatly inhibited airway inflammation and OVA-specific IgE production. The induction of peripheral T-cell tolerance and protection against AHR were not dependent on the presence of IFN-gamma or IL-4. The development of AHR was also prevented by an OVA-specific T(H)1-biased immune response induced by inhalation of OVA in the presence of IL-12. However, the OVA-specific T(H)1 response was associated with a significant degree of pulmonary inflammation.

CONCLUSION

These results indicate that both allergen-specific T-cell tolerance and T(H)1-biased immune deviation prevent the development of AHR, but T(H)1 responses are associated with significantly greater inflammation in the lung than is associated with T-cell unresponsiveness. Therefore CD4(+) T-cell unresponsiveness critically regulates immune responses to aeroallergens and protects against the development of allergic disease and asthma.

Dietary nucleic acids promote a shift in Th1/Th2 balance toward Th1-dominant immunity

BACKGROUND

Dietary sources of nucleic acids and their relative components are known to affect host immune function; however, it has not yet been clarified whether such dietary nucleic acids influence the pathogenesis of allergic reaction.

OBJECTIVE

The purpose of this study is to elucidate the effect of dietary nucleic acids on Th1/Th2 balance.

METHODS

Both human flora-associated and specific pathogen-free BALB/c mice were maintained on either nucleic acid-free, or -supplemented diets. The effects of nucleic acids on both in vivo antibody levels and in vitro splenocyte cytokine production were compared using these mice.

RESULTS

Supplementation of nucleic acids caused a reduction in the serum antibody levels of total IgM, IgG, IgG1, and IgE in the human flora-associated mice without affecting the composition of intestinal flora. In contrast, there was no significant difference of the serum IgG2a levels between nucleic acid-free and -supplemented mice. Such a phenomenon as that, the supplementation of dietary nucleic acids reduces the serum IgE or IgG1 levels, but not the IgG2a level, was also seen in the specific pathogen free mice. Moreover, when the mice were systematically challenged with ovalbumin, the supplementation of nucleic acids also suppressed the serum ovalbumin-specific IgE and IgG1 antibody levels as well as in vitro IL-4 and IL-10 secretion, while enhancing both the serum ovalbumin-specific IgG2a antibody levels and in vitro IFN gamma secretion.

CONCLUSION

These results suggested that dietary nucleic acids may play an important role in promoting a shift in Th1/Th2 balance toward Th1-dominant immunity.

Mechanisms and advances in allergic diseases

There have been many attempts to explain the increases in the incidence of allergic diseases, including hay fever and allergic asthma, that have been documented worldwide in recent decades. Epidemiologic studies offer rich opportunities to uncover sometimes unexpected correlations between lifestyle, environmental exposures, temporal development of the immune system, and genetics. Examples include the differing prevalence of atopy, bronchial hyperresponsiveness, and asthma in East and West Germany around the time of reunification, which suggests that a "western lifestyle presents a greater risk for the development of allergic responses than the more traditionally suspected factor of outdoor air pollutant levels. Other epidemiologic studies suggest how infections may interface with an atopic patterning: Evidence from natural measles exposure and nonwheeze-inducing lower respiratory tract infections in young children implicate early childhood viral infections as protective against the development of atopy and airway allergic sensitivity, although in later life viral airway infections exacerbate asthma symptoms. These studies and others involving the scrutiny of lymphocyte subtypes in atopic individuals, notably T(H1) and T(H2) cells, are helping to formulate a theory of interdependence between the early development of the immune system, allergen exposure, and the diverse community of airway cells whose secretory products generate the final physiologic response pattern.

A parental history of asthma is a risk factor for wheezing and nonwheezing respiratory illnesses in infants younger than 18 months of age

The relationship between respiratory infection and allergy as risk factors for the development of wheezing illnesses in infants has been in dispute. We hypothesized that a parental history of allergic diseases would be associated with an increased rate of respiratory infections as well as an increased rate of wheezing during infectious episodes. We prospectively evaluated 1,193 infants from birth to 18 mo of age, using bi-weekly telephone surveillance to document all respiratory events. The overall rate of respiratory illness (all RI) increased to a maximum of 10.6 illnesses/infant/year in the 7- to 9-mo age group and then leveled off in the older infants. Multivariable models adjusting for demographic variables, breast feeding, month of illness, number of siblings, and attendance at day care showed an increase in the rate of all RI in infants older than 7 mo of age who had a parental history of asthma (OR = 1.24, CI = 1.09 to 1.41) or a parental history of atopy (OR = 1.14, CI = 1.03 to 1.26). The rate of lower respiratory illnesses accompanied by wheezing was related only to a parental history of asthma (OR = 2.06, CI = 1.36 to 3.11). We conclude that all RI, most of which represent viral infections, are increased in otherwise normal infants with a parental history of asthma or atopy, whereas wheezing is related only to a parental history of asthma.

Airborne endotoxin exposure and the development of airway antigen-specific allergic responses

BACKGROUND AND OBJECTIVE

Repeated exposure of aerosolized antigen via respiratory tract can induce immunoglobulin (Ig) E isotype-specific tolerance to this antigen. However, the atopic individuals often produce a higher titre of IgE in response to airborne environmental allergens. The mechanisms of this differential regulation of airway allergen-specific immune responses are not fully understood. This study investigated the role of airborne endotoxin on the initiation of antigen-specific airway allergic responses.

METHODS

ELISA methods for detection of isotypes of antigen-specific antibodies and competitive reverse transcription polymerase chain reaction for detection mRNA of cytokines were used. In addition, Liu stain method was used to analyse the amounts of eosinophils in bronchoalveolar lavage fluid.

RESULTS

Mice pre-exposed with airborne endotoxin mounted significantly higher amounts of OVA-specific IgE antibody responses to inhaled OVA than those OVA-only sensitized mice. Inhaled endotoxin could downregulate repeated airway antigen exposure-induced IgE isotype-specific tolerance and increase antigen-induced lung eosinophils infiltration.

CONCLUSIONS

These data show that airborne endotoxin exposure could potentiate allergen-specific airway inflammation. The results should have potential implications for understanding the development of allergen-induced airway allergic responses.

Mimicking microbial 'education' of the immune system: a strategy to revert the epidemic trend of atopy and allergic asthma?

Deficient microbial stimulation of the immune system, caused by hygiene, may underly the atopy and allergic asthma epidemic we are currently experiencing. Consistent with this 'hygiene hypothesis', research on immunotherapy of allergic diseases also centres on bacteria-derived molecules (eg DNA immunostimulatory sequences) as adjuvants for allergen-specific type 1 immune responses. If we understood how certain microbes physiologically 'educate' our immune system to interact safely with environmental nonmicrobial antigens, we might be able to learn to mimic their beneficial actions. Programmed 'immunoeducation' would consist of safe administration, by the correct route, dose and timing, of those microbial stimuli that are necessary to 'train' the developing mucosal immune system and to maintain an appropriate homeostatic equilibrium between its components. Overall, this would result in a prevention of atopy that is not limited to certain specific allergens. Although such a strategy is far beyond our present potential, it may in principle revert the epidemic trend of atopy and allergic asthma without jeopardizing the fight against infectious diseases.

Mononuclear cell reactivity to food allergens in neonates, children and adults

A model of antigen-specific T-cell proliferative responses based on reciprocal patterns of responses to dietary and inhalant allergens has been suggested, the former being frequent in infancy but rare in adults, whereas the latter are preserved and expand between infancy and adulthood. We have evaluated the age-related variations of mononuclear cell reactivity to food allergens. The cord blood mononuclear cells (CBMC) of 30 neonates without family history of atopy and the peripheral blood mononuclear cells (PBMC) of 20 healthy children and of 40 healthy adults were stimulated in vitro with beta-lactoglobulin (BLG) or ovalbumin (OVA) and the cultures were harvested after 7 days. Neonates, children and adults were compared for the percentages of positive responses and for the magnitude of response. Adult subjects showed significantly lower percentages of positive responses and reduced magnitude of response than those observed in neonates and children either in BLG or in OVA cultures. We have not observed a decrease of food allergen mononuclear cell reactivity between neonates and children for the frequency of positive responses. The magnitude of response of neonates was significantly lower than that of children in BLG cultures. Our results seem to confirm the loss of mononuclear cell reactivity to food allergens in adult age. However, other reports show conflicting data. We suggest that a rigorous standardization of the methodological steps of in vitro mononuclear cell stimulation with allergen is necessary.

Intranasal Exposure to Protein Antigen Induces Immunological Tolerance Mediated by Functionally Disabled CD4+ T Cells

In this study we examined the immunological parameters underlying the natural immunity to inhaled nonpathogenic proteins. We addressed this question by examining the effect of intranasal exposure to OVA in both wild-type mice and mice reconstituted with OVA-TCR transgenic CD4+ T cells. Intranasal administration of OVA induced an initial phase of activation during which CD4+ T cells were capable of proliferating and producing cytokines. Although many of the OVA-specific CD4+ T cells were subsequently depleted from the lymphoid organs, a stable population of such T cells survived but remained refractory to antigenic rechallenge. The unresponsive state was not associated with immune deviation due to selective secretion of Th1- or Th2-type cytokines, and the presence of regulatory CD8+ T cells was not required. Moreover, neutralization of the immunosuppressive cytokines IL-10 and TGF-β did not abrogate the induction of tolerance. Inhibition of the interaction of T cells with CD86, but not CD80, at the time of exposure to intranasal Ag prevented the development of unresponsiveness, while selective blockade of CTLA-4 had no effect. Our results suggest that intranasal exposure to Ags results in immunological tolerance mediated by functionally impaired CD4+ T cells via a costimulatory pathway that requires CD86.

An airbone mold-derived product, beta-1,3-D-glucan, potentiates airway allergic responses

Repeated inhalation of allergen leads to the down-regulation of allergen-specific IgE responses in non-atopic individuals as well as in mice. This phenomenon is named inhalation-induced IgE tolerance. In contrast, inhaled allergen causes significant IgE and allergic responses in atopic persons. The mechanisms involved in this differential regulation of airway allergen-specific immune responses remain unclear. Besides the allergen exposure of genetically susceptible individuals, environmental contamination is considered to play a role as an initiating factor for airway allergic responses. Using a murine model, we demonstrate here that airborne beta-1, 3-D-glucan, which exists frequently in our environment, particularly in highly humid areas, can abrogate inhalation-induced IgE isotype-specific down-regulation and promote airway eosinophil infiltration to inhaled antigen.

Development of immunoglobulin G and immunoglobulin E antibodies to cow's milk proteins and ovalbumin after a temporary neonatal exposure to hydrolyzed and whole cow's milk proteins

The ingestion of food antigens usually results in the induction of oral tolerance, but the clinical and immunologic consequences of brief exposure to cow's milk proteins during the neonatal period are not well-documented. The aim of this work was to study immunoglobulin (Ig)E and IgG responses to cow's milk proteins and ovalbumin after exposure during the first three days of life in infants who were otherwise exclusively breast-fed. A group of 129 infants was randomly assigned at birth to one of three feeding regimens: human milk (HM), cow's milk formula (CMF), or a casein hydrolysate formula (CHF), during the first three days of life. They were then all exclusively breast-fed for a varying period of time and followed for two years. Serum IgG and IgE antibodies to cow's milk proteins and ovalbumin (OVA) were analyzed in blood samples obtained at birth, at 4 days and at 2, 4, 8, 12 and 24 months of age. The levels of IgG antibodies to beta-lactoglobulin (IgG-BLG) and bovine serum albumin (IgG-BSA) were higher in the CMF and the HM groups than in the CHF group for up to two years. This was particularly obvious for IgG-BLG in infants who started weaning before two months. The levels of IgG antibodies to casein (IgG-CAS) were higher in the CMF group, as compared with the CHF group at 8 and 12 months. The levels of IgG antibodies to OVA were similar in all three feeding groups. The levels of IgE antibodies to CAS or OVA were similar in the three feeding groups. Exposure to cow's milk during the first three days of life stimulated IgG antibody production to cow's milk proteins and this was still obvious at 2 years of age, while feeding with a casein hydrolysate during the first three days of life was associated with low levels of IgG antibodies to cow's milk proteins.

The pathogenesis and control of diarrhoea and breech soiling in adult Merino sheep

Diarrhoea and soiling of the breech with faeces ('winter scours') is a serious problem in adult Merino sheep grazing improved pastures in south-eastern Australia during winter and spring. This occurs even on farms where gastro-intestinal nematodes are effectively controlled. It was shown that winter scours was associated with the ingestion of trichostrongylid larvae, and that host factors were important in determining susceptibility to this syndrome. No differences were detected in the protective immune response of affected and unaffected sheep to gut nematodes. However, affected sheep had a hypersensitive inflammatory reaction in the pylorus and upper jejunum, characterised by the infiltration of significantly more eosinophils and changed lymphocyte populations. The changes in the lymphocyte populations included a reduced number of CD8+ cells, increased CD4+:CD8+ T-cell ratio, and significantly reduced numbers of cells reacting to interferon-gamma. High doses of infective larvae (20,000/week of Ostertagia circumcincta and Trichostrongylus vitrinus) did not induce diarrhoea in sheep not susceptible to winter scours. In contrast, only low doses (2000/week) initiated scouring in sheep selected as being susceptible to winter scours. Therefore, even considerably improved worm control programmes, including the selection of sheep with increased resistance to gut nematodes, will not prevent winter scours. Rather, phenotypic culling and genetic selection, to remove sheep susceptible to the hypersensitivity inflammatory response, is proposed as the most suitable long-term control strategy.

Mode of delivery directs the phagocyte functions of infants for the first 6 months of life

Factors that direct the immune responsiveness of the newborn beyond the immediate post-natal period are not known. We investigated the influence of mode of delivery and type of feeding on the phagocyte activity during the first 6 months of life. Sixty-four healthy infants (34 delivered vaginally and 30 by elective Caesarean section) were studied at birth and at the ages of 2 and 6 months. Phagocyte functions were studied by measuring the chemiluminescence (CL) activity of whole blood and isolated leucocytes and by investigating the expression of phagocyte receptors (FcgammaRI (CD64), FcgammaRII (CD32), FcgammaRIII (CD16), CR1 (CD35), CR3 (CD11b) and FcalphaR (CD89)) on neutrophils, monocytes and eosinophils by using receptor-specific MoAbs and immunofluorescence flow cytometry. Infants born by elective Caesarean section had significantly higher CL activity than those delivered vaginally during the entire 6-month follow up. In addition, infants who received formula feeds had significantly higher CL activity at 6 months of age and higher expression of FcgammaRI-, Fcalpha- and CR3-receptors on neutrophils than infants exclusively breast-fed. We suggest that stress reaction associated with labour influences the phagocytic activity measured in the cord blood but later during infancy the intraluminal antigens, gut microflora and diet, become important determinants in immune programming of human individuals.

Safety of inhaled proteins for therapeutic use

The use of the inhalation route for delivery of inhaled proteins has received increasing attention recently. The purpose of this article is to review the available information related to the safety aspects of inhaled proteins. The review focuses primarily on possible toxicity to the respiratory tract, because usually one is either considering an agent to treat the lung or an agent for which the systemic toxicity has been investigated following subcutaneous (s.c.) administration in its clinical use as a therapeutic agent. Some background is provided on mechanisms of absorption and reasons why inhalation delivery is considered for many proteins. Available data are summarized from clinical trials of proteins and protein-like biomolecules, generally showing minimal, if any, adverse respiratory effects. The results of the animal toxicology studies that have been published are presented. In general, the observed lung toxicity has been relatively low, and it has been difficult to interpret in cases where the animal protein differs considerably from the human protein. Discussion is presented on the possibility of adverse immune reactions, suggesting that this is not likely to be any greater issue than it is for subcutaneously injected materials. Although the safety information is relatively sparse at present, the available data suggest that the inhalation route can be an attractive route to consider for many therapeutic proteins.

Expression of the T-cell markers CD3, CD4 and CD8 in healthy and atopic children during the first 18 months of life

BACKGROUND

There is little information available about the development of T-cell immunity in healthy and atopic children. We have studied prospectively the mean fluorescence intensity of the T-cell receptor complex-associated CD3, CD4 and CD8 in relation to atopic family history (AFH) and the development of atopic disease.

METHODS

Children with a defined AFH (n = 172) were followed from birth to 18 months and the cumulative history of atopic disease was recorded. Blood samples were obtained at birth and at 18 months, and in a subgroup of 78 children also at 3, 6 and 12 months. Multicolour flow cytometry was used to analyse pan T-cells (CD3+CD45+CD14-), T-helper-(CD3+CD4+) and T-cytotoxic-(CD3+CD8+) cells.

RESULTS

At 18 months, 31 children were atopic and 118 non-atopic. Children who developed atopic disease had a higher CD4 expression (mean fluorescence intensity, MFI) on CD4+CD3+ lymphocytes at birth and at 3 months, particularly as compared with non-atopic children without AFH. Furthermore, the CD3 expression on CD3+CD45+CD14- lymphocytes increased more slowly with age in children with double atopic heredity, as compared with children with no or only one atopic family member.

CONCLUSIONS

The higher expression of the CD4 receptor in early infancy in children who developed atopic disease compared with non-atopics suggests a delayed expression in T-helper cells. Children with a strong AFH had a slower increase in the expression of CD3, indicating a delayed T-cell maturation.

A Polymorphism* in the 5' flanking region of the CD14 gene is associated with circulating soluble CD14 levels and with total serum immunoglobulin E

Total serum immunoglobulin (Ig)E levels are genetically regulated, but the mechanism of inheritance is not well understood. Cytokines produced by T-helper (Th)1 and Th2 lymphocytes control IgE synthesis. Bacterial antigens may favor the development of Th1 cells from naive CD4-positive T cells through a CD14-dependent pathway. CD14 is constitutively expressed on the surface of monocytes and macrophages, and is also present in serum in a soluble form (sCD14). The CD14 gene maps to chromosome 5q31.1, a candidate region for loci regulating total serum IgE. We hypothesized that genetic variants in the CD14 gene could influence Th-cell differentiation and thus total serum IgE. We identified a C-to-T transition at base pair -159 from the major transcription start site (CD14/-159). Among 481 children recruited from a general population sample, frequency of allele C was 51.4%. TT homozygotes had significantly higher sCD14 levels than did carriers of both the CC and CT genotypes (P = 0.01). TT homozygotes also had significantly lower levels of IgE than did carriers of the other two genotypes, but differences were significant only among children who were skin test-positive to local aeroallergens (P = 0.004). There was no association between CD14/-159 and either interleukin (IL)-4 or interferon (IFN)-gamma responses by peripheral blood mononuclear cells. However, IFN-gamma and IL-4 responses were positively and negatively correlated, respectively, with serum sCD14 levels. We conclude that CD14/-159 plays a significant role in regulating serum sCD14 levels and total serum IgE levels.