Asthma: an epidemic in the absence of infection?

Factors associated with asthma in Albania

BACKGROUND

This study was undertaken to see whether asthma in Albania (where it is particularly uncommon) is associated with certain 'western' characteristics, and with dietary and lifestyle factors that affect its occurrence elsewhere.

METHODS

A screening survey was conducted among 2653 persons aged 20-44 years. A more detailed enquiry was conducted among a random subsample plus all others whose response indicated possible asthma. Three groups were compared: 495 probable nonasthmatics ('nonsymptomatics'); 106 with asthma-like symptoms and positive skin tests ('possible allergic asthmatics'); and 116 with similar symptoms and negative skin tests ('other symptomatics').

RESULTS

The possible allergic asthmatics were less likely than the nonsymptomatics to have attended school or nursery under the age of 5 years or to have shared a bedroom with an older child before that age. Continued education after the age of 18 years also appeared to be protective. Allowing for other factors, a strong negative relation was found with fruit and vegetable consumption, and weak positive relations with prepackaged food and fizzy drinks. Symptoms in skin prick test-negative subjects were associated with personal and parental smoking habit.

CONCLUSIONS

This survey provides limited evidence linking asthma with aspects of western lifestyle. It supports the hypothesis that opportunities for infection during early childhood and the consumption of fruit and vegetables protect against asthma.

IL-4 signaling, gene transcription regulation, and the control of effector T cells

The central goal of our laboratory is to understand the regulation of lymphoid cells through molecular mechanisms of signal transduction and transcriptional control. A long-standing focus has been on changes that influence the effector function of mature lymphocytes. Work in the laboratory is oriented toward the identification of new regulatory mechanisms using cell lines and primary cells, and the validation of these in vitro findings in mouse models of immune responses and diseases. In this review, we summarize key insights into the regulation of T helper cell function during the phase of immunity where effector responses arise de novo. Particular interest has been centered on cytokine gene regulation as part of T cell differentiation into the Th1 and Th2 subsets. Information on IL-4 receptor signaling and the role of NF-kappaB transcription factors is reviewed. Our more recent work is designed to understand how regulation at the Th1/2 effector stages is related to the control of memory T cell survival, immune recall responses, and the role of these responses in immune-mediated disease.

Efficacy of recombinant adenovirus as vector for allergen gene therapy in a mouse model of type I allergy

DNA-based immunization represents an attractive alternative approach to the current treatment of allergic diseases by specific immunotherapy with allergen extracts. In this study, we used a replication-deficient adenovirus vector (AdCMV), to examine the in vivo efficacy of preventive and therapeutic genetic immunization in a mouse model of type I allergy. Primary immunization with a recombinant adenovirus expressing the model antigen beta-galactosidase (AdCMV-(beta)gal) induced a Th1 immune response (predominance of IgG2a antibodies, high frequency of IFN-gamma producing T cells) and large numbers of cytotoxic T lymphocytes. Prophylactic vaccination with AdCMV-(beta)gal abolished the production of specific IgE following subsequent immunization with (beta)gal-protein, and skewed the Th2-biased immune response to a Th1-orientated response. In contrast, therapeutic administration of AdCMV-(beta)gal after priming with (beta)gal-protein neither significantly inhibited ongoing IgE production nor modulated a manifest Th2 immune response. Thus, allergen gene transfer via recombinant adenovirus represents an effective method to establish protection against the development of allergic disorders, but does not qualify as a therapeutic tool to interfere with ongoing high IgE production.

Chlamydia trachomatis infection inhibits airway eosinophilic inflammation induced by ragweed

While much progress has been achieved in controlling infectious diseases, there is a startling increase in the prevalence of allergic disorders in developed countries. Previous studies using experimental murine models of asthma have demonstrated that mycobacterial infections are capable of suppressing asthma-like reactions induced by ovalbumin (OVA). Using a different intracellular bacterium, Chlamydia trachomatis mouse pneumonitis (MoPn), we examined the effect of infection on the development of allergic responses to a common natural airborne allergen, ragweed (RW). The data showed that airway eosinophilia induced by ragweed sensitization/challenge was significantly reduced in MoPn-infected mice. MoPn-infected mice also exhibited significantly lower levels of allergen-driven Th2 cytokine production, namely IL-4, IL-5, IL-10, and IL-13, following ragweed exposure in comparison with those treated with ragweed only. Additionally, the production of eotaxin, a C-C chemokine for eosinophil chemoattraction following RW exposure, was significantly reduced in the lungs of MoPn-infected mice. However, MoPn infection did not reduce the levels of RW-specific IgE and IgG1 production in the sera, nor did it diminish the level of total serum IgE. These data provide evidence that the suppression of the allergic airway inflammation induced by a common environmental allergen is attainable through intracellular bacterial infection.

CpG ODN can re-direct the Th bias of established Th2 immune responses in adult and young mice

Induction of an appropriate immune response is essential for successful immunization. For example, Th1 type immune responses are necessary for the control of intracellular infections whereas Th2 type responses are more useful for the control of extracellular infections. Immunostimulatory CpG ODN (oligonucleotides containing unmethylated cytosine and guanine dinucleotides in specific base contexts) act as potent adjuvants and have been shown to induce Th1 type immune responses with a number of different antigens. This study investigates the effect of CpG ODN on the Th bias of immune responses generated against the hepatitis B major surface antigen (HBsAg) in adult (6-8 weeks old) and young (<1 week old) BALB/c mice. It also investigates the potential of CpG DNA to reverse a pre-established Th2 response generated as an adult or as a neonate, following re-exposure to HBsAg in adult life. Both adult and young mice immunized with HBsAg/CpG ODN had a Th1 biased immune response (strong cytotoxic T-lymphocyte (CTL) induction, IgG2a>>IgG1). In contrast, mice immunized with HBsAg/alum had a Th2 type immune response (poor CTL, IgG1>>IgG2a). More importantly, when animals were immunized with HBsAg/alum and boosted with HBsAg/CpG ODN, the CpG ODN were able to re-direct the Th2 response pre-established by alum, whereas the animals receiving the primary immunization with HBsAg/CpG ODN and later boosted with HBsAg/alum maintained their Th1 bias, even after the boost with alum. These data suggest that CpG ODN have the ability to augment both humoral and cell mediated immune responses and override the Th2 bias created by alum, even in very young animals, which are known to have a Th2 biased immune system.

Asthma, smoking and chronic cough in rural and urban adult communities in The Gambia

BACKGROUND

Asthma is reported to be rare in traditional rural communities, but is thought to be increasing as lifestyles become more urbanized or 'western'.

OBJECTIVES

A community-based survey of non-communicable diseases was conducted from October 1996 to June 1997, and included comparison of the prevalence of asthma, smoking and chronic cough in rural and urban Gambia.

METHODS

A cluster sample survey was conducted in a random sample of rural and urban adults (> or = 15 years of age). Subjects were asked about respiratory symptoms using a locally adapted version based on the IULTD questionnaire. Spirometry (basal, methacholine provocation and reversibility with a bronchodilator) and skin prick tests were performed on a randomly selected subsample of all subjects and those who, when interviewed, said they wheezed or had been diagnosed as asthmatic by a doctor.

RESULTS

Out of 2166 participants in the urban population, 4.1% reported having had wheezing or whistling in the chest in the previous 12 months, 3.6% reported doctor-diagnosed asthma, and 0.6% chronic cough. In the rural population with 3223 participants these figures were 3.3%, 0.7% and 1.2%, respectively. Wheeze was more common in women, cough for 3 months of the year was more common in the age-groups 45+. Those who reported that they currently smoked accounted for 34% in urban and 42% in rural men. Figures were much lower for women (1.5% and 6.0%). Seven out of 574 randomly selected subjects (1.4%) exhibited bronchial hyper-responsiveness to methacholine challenge. Four of 133 (3.0%) people with self-reported wheeze and 3/69 (4.3%) participants with doctor-diagnosed asthma reacted positively on bronchial provocation with methacholine. There was a remarkably high prevalence of positive skin prick tests to aeroallergens: 38% in participants with a history of wheeze and 27% in those without.

CONCLUSION

The prevalence of wheeze (particularly in association with bronchial hyper-responsiveness) was low in both rural and urban Gambia. This is in contrast to the relatively high prevalence of positive skin prick tests to aeroallergens (in both wheezers and non-wheezers), questioning the mechanisms of interaction between allergy and asthma and the presence of protective factors against asthma in this West African population. The high smoking rates justify international concern about tobacco marketing in developing societies.

The prevalence of parasite infestation and house dust mite sensitization in Gabonese schoolchildren

BACKGROUND

Allergic diseases seem less prevalent in communities in less developed parts of the world, where parasite infections are highly prevalent. Altogether not much is known about the association between chronic infections with tissue and blood-dwelling parasites and atopy.

METHODS

In an area in Gabon endemic for blood and tissue parasites, 520 schoolchildren were parasitologically examined and skin prick-tested for a set of common environmental aeroallergens. Levels of allergen-specific IgE and polyclonal IgE were measured.

RESULTS

In schoolchildren schistosome and filarial infections increased with age, whereas malaria was more prevalent in younger children. In contrast to allergen sensitization that increased with age, skin test reactivity tended to decline. The number of children with mite-specific IgE antibodies (47%) by far exceeded the number responding to skin prick testing (11%). Mite sensitization was found to be the highest in children infected with schistosomes and/or filariae whereas skin test reactivity was lowest. The multiple logistic regression showed that the risk of a positive skin test was 8-fold higher with increasing levels of mite-specific IgE but was reduced by 72% when infected with blood stage helminths.

CONCLUSIONS

Chronic blood and tissue parasite infections that are often capable of modulating immune responses in the host are negatively associated with skin test reactivity in a sensitized population.

Relationship between asthma medication and antibiotic use

STUDY OBJECTIVES

Increasing morbidity due to asthma and antimicrobial resistance among human pathogens are both major public-health concerns. Numerous studies describe the overuse of antibiotics in general populations and underuse of anti-inflammatory medications by asthmatic patients. However, little is known about the relationship between asthma medication and antibiotic use in asthmatics. Specifically, we tested the hypothesis that higher use of bronchodilator and anti-inflammatory medication by asthmatics, as a marker of problematic asthma, is associated with greater antibiotic use. We also test the hypothesis that physicians who are low prescribers of anti-inflammatory medications are high prescribers of antibiotics.

DESIGN

We conducted a retrospective cohort study evaluating asthma medication and antibiotic use by children and adults with asthma and the prescribing of these medications by primary-care physicians.

SETTING/PATIENTS

Subjects were continuously enrolled asthma patients aged 6 to 55 years receiving care in an urban, group-model, health maintenance organization.

INTERVENTIONS

None.

MEASUREMENT AND RESULTS

Main outcome measures were (1) antibiotic use by asthmatics stratified by low, moderate, and high bronchodilator use; (2) antibiotic use by asthmatics stratified by no, intermittent, and long-term anti-inflammatory use; and (3) correlation between physician-level anti-inflammatory agent to bronchodilator ratio (AIF:BD) and their rate of antibiotic prescribing. We found that (1) high bronchodilator users received 1.72 antibiotics per person-year (95% confidence interval [CI], 1.62 to 1.83), whereas low bronchodilator users received 1.23 antibiotics per person-year (95% CI, 1.19 to 1.27; p < 0.0001); (2) long-term users of anti-inflammatory agents received 1.85 antibiotics per person-year (95% CI, 1.76 to 1.95), whereas those not receiving an anti-inflammatory agent received 0.95 antibiotics per person-year (95% CI, 0.90 to 1.00; p < 0.0001); and (3) despite variations in physician AIF:BDs and antibiotic prescribing, respectively, these measures were not correlated.

CONCLUSIONS

Antibiotic use and asthma medication use are positively associated in a cohort of asthma patients. Greater effort is needed to define the appropriate role of antibiotics in asthma management.

Family history and the risk of early-onset persistent, early-onset transient, and late-onset asthma

Family history of asthma and allergies strongly influences asthma risk in children, but the association may differ for early-onset persistent, early-onset transient, and late-onset asthma. We analyzed the relation between family history and these types of asthma using cross-sectional data from a school-based study of 5,046 Southern California children. Parental and/or sibling history of asthma and allergy were generally more strongly associated with early-onset persistent asthma compared with early-onset transient or late-onset asthma. For children with two asthmatic parents relative to those with none, the prevalence ratio for early-onset persistent asthma was 12.1 [95% confidence interval (CI) = 7.91-18.7] compared with 7.51 (95% CI = 2.62-21.5) for early-onset transient asthma and 5.38 (95% CI = 3.40-8.50) for late-onset asthma. Maternal smoking in pregnancy was predominantly related to the risk of early-onset persistent asthma in the presence of parental history of allergy and asthma, and the joint effects were more than additive (interaction contrast ratio = 3.10, 95% CI = 1.45-4.75). Our results confirm earlier data that parental history of asthma and allergy is most strongly associated with early-onset persistent asthma and suggest that among genetically predisposed children, an early-life environmental exposure, maternal smoking during pregnancy, favors the development of early-onset asthma that persists into later early childhood.

Down-regulation of IgE and IgG4 antibodies to tetanus toxoid and diphtheria toxoid by covaccination with cellular Bordetella pertussis vaccine

Pertussis (P) toxin acts as adjuvant for IgE formation against simultaneously administered Ags in animal models. P vaccination may also have an adjuvant impact on IgE formation against coadministered diphtheria (D) and tetanus (T) Ags in humans. Sera of 103 D-T-P-immunized and 319 D-T-immunized children aged 2 years were analyzed for IgE, IgG4, and IgG to D and T (radioallergosorbent test), total IgE and IgE against common inhalant allergens (CAP radioallergosorbent test fluoroenzyme immunoassay). Fewer D-T-P- than D-T-immunized children had sera positive for T-IgE (12.6 vs 53.6%, p < 0.001), T-IgG4 (71.6 vs 89.2%, p < 0.001), D-IgE (31.0 vs 70.5%, p < 0.001), and D-IgG4 (85.2 vs 93.4%, p = 0.039). Suppression of T-IgE was not dependent on the cutoff chosen for a positive test result, but was dependent on the proportion of D-T immunizations given with P. The risk for sensitization to common environmental allergens did not differ (odds ratio 0.953, 95% confidence interval 0.815-1.114). No significant differences between D-T- and D-T-P-immunized children were found with regard to T-IgG or D-IgG. In summary, IgE and IgG4 (but not IgG) serum levels to coadministered D- and T-Ags are suppressed among P-immunized children as compared with nonimmunized children. These results suggest that the presence of a microbial product during Ag exposure can down-regulate an IgE/IgG4 response in humans.

Th2 responses without atopy: immunoregulation in chronic helminth infections and reduced allergic disease

The immune response to helminth infections has long been known to share key features with the allergic response. In particular, both are typified by enhanced T helper 2 (Th2) responses with high levels of interleukin-4 (IL-4), IL-5 and IL-13, accompanied by eosinophilia and abundant IgE production. Paradoxically, the geographical distribution of helminth parasitism and allergic disease is complementary rather than coincident. Thus, the question arises does the Th2 response to parasites protect or pre-empt the host from developing Th2-linked allergic manifestations? It is suggested that downregulatory immune mechanisms, which dampen the anti-parasite response, might benefit the host by blocking progression to atopic reactions. This is of relevance in explaining how the "hygiene hypothesis" might operate immunologically and in the design of therapeutics.

Environmental exposure to Toxocara as a possible risk factor for asthma: a clinic-based case-control study

The zoonotic ascarid Toxocara has been suggested as a possible etiologic agent of asthma. We conducted a clinic-based case-control study to examine whether the zoonotic infection acquired by ingesting Toxocara eggs is associated with asthma in children. Blood samples were collected from children aged 2-15 years, 95 of whom had asthma and 229 of whom did not have asthma. Risk factors for asthma and Toxocara infection were assessed by a questionnaire given to each child's parent or legal guardian. Blood samples were tested for the presence of Toxocara antibodies, using an enzyme-linked immunosorbent assay. No significant association was found between Toxocara infection and asthma. Significant associations were found between asthma and risk factors and between Toxocara infection and risk factors. High prevalence of Toxocara infection was noted among Hispanic children of Puerto Rican descent.

Childhood risk factors for atopy and the importance of early intervention

The increasing prevalence of atopic diseases, particularly atopy-associated asthma, has become a major challenge for allergists and public health authorities in many countries. The understanding of the natural history of the atopic march, including the determinants that are modifiable and might become candidates for preventive intervention, is still very limited. Information provided by cross-sectional studies can only generate hypotheses, which need to be supported by prospective, longitudinal, cohort studies. Ultimately, it will depend on the results of well-controlled intervention studies to identify which nutritional, environmental, or lifestyle-related factors should be considered for early intervention and might be useful to reverse the epidemiologic trend.

Intradermal administration of a killed Mycobacterium vaccae suspension (SRL 172) is associated with improvement in atopic dermatitis in children with moderate-to-severe disease

BACKGROUND

Although a doubling in the prevalence of atopic disease, including atopic dermatitis, in the Western world over the last few generations has been paralleled by a marked reduction in infectious diseases, especially tuberculosis, it is unclear whether this increase in atopy is causally related to reduced exposure to mycobacteria.

OBJECTIVES

The aim of this study was to determine whether administration of mycobacterial antigens to atopic individuals might ameliorate their disease.

METHODS

Forty-one children aged 5 to 18 years with moderate-to-severe atopic dermatitis were enrolled in a randomized, double-blind, placebo-controlled trial, where they were given either one intradermal injection of killed Mycobacterium vaccae (SRL 172) or buffer solution (placebo). Changes in skin surface area affected by dermatitis and dermatitis severity score were assessed before treatment and at 1 and 3 months after treatment.

RESULTS

Children treated with SRL 172 showed a mean 48% (95% CI, 32%-65%) reduction in surface area affected by dermatitis compared with a mean 4% (95% CI, -29% to 22%) reduction for the placebo group (P <.001) and a median 68% (interquartile range, 46%-85%) reduction in dermatitis severity score compared with 18% (interquartile range, -2% to 34%) for the placebo group (P <.01) at 3 months after treatment. There were no untoward effects of the treatment, apart from a local reaction in 13 of the 21 children, which occurred 1 month after SRL 172 administration and settled spontaneously.

CONCLUSION

SRL 172 was associated with an improvement in the severity of the dermatitis in children with moderate-to-severe disease.

Use of transgenic animals to investigate drug hypersensitivity

Hypersensitivity reactions to drugs and environmental agents are often due to exaggerated humoral (Th(2)) or cell mediated (Th(1)) immune responses with typical cytokine profiles. Overexpression of Th(2) cytokines, such as IL-4, IL-5 or IL-13 in mice, enhances an IgE antibody mediated response, while deletion of these cytokines attenuates and/or prevents allergic responses. Conversely, modulation of Th(1) cytokine gene expression may affect cell-mediated immune responses. Therefore, cytokine transgenic mice are used as investigative tools to study potential chemicals and/or drug allergies. In addition to cytokines and chemokines, other factors are important for the development of allergic responses, such as IgE, Fc receptors, vasopressin and several other factors, which can be tested in transgenic mice.

Effects of Mycobacterium bovis BCG on the development of allergic inflammation and bronchial hyperresponsiveness in hyper-IgE BP2 mice vaccinated as newborns

Asthma may result from excessive Th-2 response in children not previously exposed to Th-1-inducing infections. We tested the hypothesis that BCG vaccination in Th-2-susceptible newborn BP2 mice blocks allergic inflammation and bronchial hyperreactivity (BHR). Ten day-old BP2 mice received 10(5) CFU of BCG 1173P2 intranasally (IN), and 6, 10 or 14 weeks thereafter were sensitized with 100 microg ovalbumin (OVA) in aluminium hydroxide twice subcutaneously (SC) at 1 week interval, and challenged 1 week after the second sensitization with 10 microg OVA IN. Compared to OVA-challenged unvaccinated mice, those that received BCG 8 weeks before challenge developed intense bronchial inflammation, BHR, and high IgE titers. Inflammation involved T cells, macrophages, dendritic cells and was accompanied by increased levels of Interleukin-5 (IL-5) in the bronchoalveolar lavages (BAL). However, animals challenged 16 weeks after BCG vaccination did not develop BHR nor bronchial hypereosinophilia, and showed reduced IgE levels. Bronchial infiltration by immunocompetent cells was also significantly reduced. Increased levels of gamma-interferon (IFN-gamma) after in vitro stimulation of tracheo-bronchial lymph node cells accompanied this blockage, but levels of IL-5 remained high. We demonstrate that 16 weeks after vaccination with BCG in newborn BP2 mice which have a high Th-2 background, allergic inflammation and BHR were blocked, even though a clear Th-1 shift was not achieved.

Delayed infection, family size and malignant lymphomas

BACKGROUND

The annual incidence of non-Hodgkin's lymphomas (NHL) is increasing by 3%-4% in different parts of the developed world. Excesses of NHL have been observed in populations exposed to immunosuppressants and to HIV, but these causes do not explain the increasing trends. It is suggested that delayed infection could explain NHL trends, through an impairment of the Th1/Th2 lymphocyte patterns.

METHODS

In a population-based study on 1388 patients with NHL, 354 with Hodgkin's disease (HD) and 1718 healthy controls, the age of first occurrence of bacterial and viral diseases was investigated. Clinical records were perused in one centre to check the anamnestic data.

FINDINGS

The age of occurrence of bacterial and viral diseases was significantly higher among NHL patients than in the controls. The association between later age at first bacterial or viral disease was limited to small families (OR= 1.95; 95% confidence intervals 1.26, 3.00, for age 4-8 at first infection; OR=1.91; 1.19, 3.06, for age 9+, compared with less than 4). The association was more obvious for bacterial diseases (possibly for the lower degree of misclassification). High grade lymphomas showed the strongest association. The later age of occurrence of bacterial or viral diseases in NHL patients is consistent with a higher incidence of lymphomas observed in higher social groups. No clear association was found between HD and age at first bacterial or viral diseases.

INTERPRETATION

It is proposed that delayed infection could explain the increasing NHL trends, through an impairment of the Th1/Th2 lymphocyte patterns. The model of delayed infection has been proposed also to explain increasing prevalence rates of asthma.

Socioeconomic status is a risk factor for allergy in parents but not in their children

BACKGROUND

Allergic diseases are more prevalent in affluent countries, which has been attributed to life-style factors. Life-style habits may also differ between socioeconomic (SES) classes. The objective of this paper therefore was to evaluate if SES had an impact on the development of atopic disorders.

METHODS

A total of 1314 German children were followed-up in an observational birth cohort study to 6 years of age. Parents filled in questionnaires, and had multi-allergen screening tests for sensitization. Indoor allergen concentrations were determined by ELISA. Children were examined regularly up to 6 years, specific serum IgE values were determined by CAP-Rast-Feia.

RESULTS

The risk of aeroallergen sensitization (odds ratio 1.76; 95% CI 1.30-2.37), and the lifetime prevalence of hay fever (2.36; 1.76-3.17), and asthma (1.74; 1.08-2.80), but not of atopic dermatitis (AD: 0.90; 0. 54-1.51) was elevated in parents of high compared to low SES. With high SES the risk of smoking in pregnancy (0.35; 0.23-0.51), in the home (0.31; 0.21-0.46), pet ownership (0.37; 0.26-0.55), high mite (0.42; 0.25-0.74), and high cat (0.38; 0.18-0.82) allergen concentration in house dust was reduced, but elevated for breastfeeding over more than 6 months (4.67; 2.9-7.48). In children, even after controlling for other risk factors, only the risk of AD from 3 to 6 years (2.42; 1.42-4.14) was elevated in families with high SES, but not of AD in infancy or of any other atopic disorder.

CONCLUSIONS

While parents of high SES have a higher prevalence of inhalative allergies, their favourable life-style prevents the development of atopic disorders in their children, except for AD beyond infancy.

Decreased atopy in children infected with Schistosoma haematobium: a role for parasite-induced interleukin-10

BACKGROUND

Most of the effort directed at understanding the role infections have in preventing allergy has focused on bacteria and viruses and their ability to divert the immune system towards T-helper-1 responses and away from proallergic T-helper-2 responses. However, helminth infections, highly prevalent in large parts of the developing world, where allergy is uncommon, stimulate strong T-helper-2 responses. We investigated the influence of chronic helminth infections on the prevalence of atopy and aimed to understand the relation at a detailed immunological level.

METHODS

520 Gabonese schoolchildren were tested for skin reaction to house-dust mite and other allergens, for Schistosoma haematobium eggs in urine, and for microfilariae in blood samples. Total and mite-specific IgE antibodies were measured. A subsample selected on the basis of their skin test to house-dust mite received detailed immunological investigations.

FINDINGS

Children with urinary schistosomiasis had a lower prevalence of a positive skin reaction to house-dust mite than those free of this infection (odds ratio 0.32 [95% CI 0.16-0.63]). The degree of sensitisation to house-dust mite could not explain this difference in skin-prick positivity. Schistosome-antigen-specific concentrations of interleukin-10 were significantly higher in infected children, and higher specific concentrations of this anti-inflammatory cytokine were negatively associated with the outcome of skin-test reactivity to mite (0.53 [0.30-0.96]). No association between polyclonal IgE antibodies and skin-test results was found.

INTERPRETATION

The anti-inflammatory cytokine, interleukin-10, induced in chronic schistosomiasis, appears central to suppressing atopy in African children.

Probiotics in the management of atopic eczema

BACKGROUND

Over the last two decades the incidence of allergic diseases has increased in industrialized countries, and consequently new approaches have to be explored.

OBJECTIVE

The potential of probiotics to control allergic inflammation at an early age was assessed in a randomized double-blind placebo-controlled study.

METHODS

A total of 27 infants, mean age 4.6 months, who manifested atopic eczema during exclusive breast-feeding and who have had no exposure to any infant or substitute formula were weaned to probiotic-supplemented, Bifidobacterium lactis Bb-12 or Lactobacillus strain GG (ATCC 53103), extensively hydrolysed whey formulas or to the same formula without probiotics. The extent and severity of atopic eczema, the growth and nutrition of infants, and concentrations of circulating cytokines/chemokines and soluble cell surface adhesion molecules in serum and methyl-histamine and eosinophilic protein X in urine were determined.

RESULTS

The SCORAD score reflecting the extent and severity of atopic eczema was 16 (7-25) during breast-feeding, median (interquartile range). After 2 months, a significant improvement in skin condition occurred in patients given probiotic-supplemented formulas, as compared to the unsupplemented group; chi(2) = 12.27, P = 0.002. SCORAD decreased in the Bifidobacterium lactis Bb-12 group to 0 (0-3.8), and in the Lactobacillus GG group to 1 (0.1-8.7), vs unsupplemented 13.4 (4.5-18.2), median (interquartile range), in parallel with a reduction in the concentration of soluble CD4 in serum and eosinophilic protein X in urine.

CONCLUSION

The results provide the first clinical demonstration of specific probiotic strains modifying the changes related to allergic inflammation. The data further indicate that probiotics may counteract inflammatory responses beyond the intestinal milieu. The combined effects of these probiotic strains will guide infants through the weaning period, when sensitization to newly encountered antigens is initiated. The probiotic approach may thus offer a new direction in the search for future foods for allergy treatment and prevention strategies.

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.

Diesel exhaust, carbon black, and silica particles display distinct Th1/Th2 modulating activity

Certain particulate air pollutants may play an important role in the increasing prevalence of respiratory allergy by stimulating T helper 2 cell (Th2)-mediated immune responses to common antigens. The study described here examined different particles, diesel exhaust particles (DEP), carbon black particles (CBP), and silica particles (SIP) for their immunomodulating capacity in both primary and secondary immune responses in female BALB/C mice. The primary response was studied after subcutaneous injection of 1 mg of particle together with 10 microgram of reporter antigen TNP-OVA (2,4,6-trinitrophenyl coupled to ovalbumin) into the hind paw. Interferon-gamma (IFN-gamma) and interleukin 4 (IL-4) production was assessed in the popliteal lymph node (PLN) at Day 2 and Day 5 after injection by flow cytometry and ELISA. The number of IL-4-containing CD4(+) T cells increased between Day 2 and Day 5 in DEP- and CBP-exposed mice, in contrast to SIP-treated animals. IL-4 production by cultured PLN cells was also significantly increased for DEP- and CBP-treated animals. The secondary response was studied in different organs after an intranasal challenge with TNP-OVA (50 microgram), which was given 4 weeks after the initial subcutaneous injection. Five days after challenge the number of antibody-forming cells (AFCs) was assessed in peribronchial lymph nodes (PBLN), spleen, bone marrow, and PLN, and antibody levels were determined in weekly obtained blood samples. It appeared that all particles acted as adjuvant, but the different particles stimulated distinct types of immune responses to TNP-OVA. DEP-treated animals show high IgG1 and IgE levels in serum and high IgG1 and IgE-forming AFC numbers in PBLN, bone marrow, and spleen. CBP-treated animals show even higher IgG1 and IgE levels and AFC numbers, and in addition display IgG2a production. SIP-injected animals display predominantly IgG2a responses. It is concluded that DEP are able to skew the immune response toward the T helper 2 (Th2) side, whereas SIP stimulate a Th1 response and CBP have a mixed activity, stimulating both Th1 and Th2 responses in this model.

Prevention of asthma morbidity: recent advances

Asthma prevalence has risen substantially in recent decades and is an increasing cause of disability for American children. Concern about the rise in morbidity has led to treatment guidelines and a growing body of clinical research. Recent trials continue to support the role of inhaled corticosteroids as the most effective therapy to control airway inflammation associated with persistent asthma. Growth suppression due to inhaled corticosteroids has also been well documented, although the long-term effects and relative potencies of different agents require further study. Other anti-inflammatory agents such as cromolyn and the new class of leukotriene receptor antagonists have demonstrated benefit in milder patients. Leukotriene receptor antagonists and long-acting beta2-agonists may allow for reduction of inhaled steroid doses. Control of environmental allergens and irritants is essential. New evidence suggests an increasingly important role for allergen immunotherapy.

Prevalence and aetiology of hypothyroidism in the young

AIMS

To define the prevalence of hypothyroid disease in children and young people, and describe its aetiology.

METHODS

We identified all patients on the Medicines Monitoring Unit (MEMO) database in the Tayside region of Scotland who had received two or more prescriptions for thyroxine during the study period (January 1993 to December 1995). Using this as a surrogate marker of hypothyroidism, we calculated the prevalence of hypothyroidism in those aged less than 22 years. Main outcome measures were prevalence of thyroxine prescription, estimated prevalence of hypothyroidism, and aetiology of the hypothyroidism (determined from case records, and biochemistry and immunology databases).

RESULTS

Of 103,500 residents aged less than 22 years, 140 were identified as receiving thyroxine on prescription, giving a population prevalence of 0.135%. The ratio of male to female was 1:2.8. Acquired hypothyroidism was the commonest aetiology found in 73%, 66% of which had an autoimmune basis. The prevalence of congenital hypothyroidism was 0.027%. Seven had received treatment for malignancy (two primary thyroid). Fifteen per cent of patients had no record of secondary care follow up in Tayside.

CONCLUSIONS

The overall prevalence of hypothyroidism in young people less than 22 years of age is 0.135%, and in the group aged 11-18 years it is 0.113%; these values are at least twice those of previous estimates. This suggests an increase in autoimmune thyroid disease, similar to the rising prevalence of type 1 diabetes, possibly indicating a rising incidence of autoimmunity in young people.

Daycare attendance, asthma and atopy

The objective of this article is to review studies that have examined the relation of daycare to asthma and atopy. In order to identify studies for inclusion, abstracts of all studies referenced in Medline from January 1966 to January 2000 and in BIBSYS were searched and extracted if they included 'asthma' or 'atopy' combined with words such as 'daycare', 'nursery' or 'kindergarten'. Eight studies fulfilled the criteria of inclusion. The outcomes were asthma, skin prick test (SPT) reactivity, a positive radioallergosorbent test (RAST), hay fever, and eczema. Daycare attendance was positively associated with asthma in five of six studies including asthma. In three of these studies there was no statistically significant association between daycare and asthma. Early start in daycare protected against later asthma in one study. There was a weak, but not a statistically significant positive relation between daycare and atopy in two of three studies when SPT reactivity was used as the outcome. In children of small families early start in daycare protected against atopy. The quality of the studies varies, and they are not directly comparable. The relation between daycare attendance and asthma and atopy is unclear, and further studies designed to answer this specific research question are needed.

Correlation between atopic diseases and tuberculin responses

BACKGROUND

In recent decades, the prevalence of atopic diseases has risen steadily in developed countries. The reasons for this increase are not clear. It has been hypothesized that a reduction in infections and immunization programs may contribute to the increase in the prevalence of atopic diseases. We investigated the relationship between tuberculin response and atopic disease.

METHODS

A total of 538 (73.0%) atopic and 198 (27.0%) nonatopic children vaccinated with BCG were included in the study. All the children included in the study had neither been given BCG nor tuberculin skin-tested in the previous 6 months, nor did they have a condition known to cause anergy. All the children were given five tuberculin units PPD, and PPD indurations were recorded after 48 h.

RESULTS

The PPD induration size was 6.8 +/- 5.6 mm (mean +/- SD) in atopic children and 7.4 +/- 5.9 mm in nonatopic children. The difference between the two groups was not significant (P > 0.05). The PPD induration sizes of children with asthma, rhinitis, and atopic dermatitis were found to be similar. The children with atopic dermatitis had lower PPD induration size, but this was not statistically significant (P> 0.05). The rates of negative (< 5 mm skin induration) and intermediate (5-9 mm) responses were 32.6% and 30.5% in atopic children and 30.2% and 32.4% in nonatopic children, respectively. Positive tuberculin responses (PPD > 10 mm) were recorded in 36.9% of atopic children and 37.4% of nonatopic children. Total serum IgE levels of atopic and nonatopic children were 623.35 and 46.78 IU/ml, respectively. There was no correlation between serum total IgE level and PPD induration size (r = - 0.0012, P = 0.737).

CONCLUSIONS

We did not find any relationship between tuberculin response and atopy status later in life in BCG-immunized subjects. We need further studies to clarify the effect of BCG on the development of atopy.

Is primary prevention of asthma possible?

The increased prevalence of asthma over the past quarter century has become a major public health problem for the industrialized world. Asthma is a disease process which has a strong heritable component which is impacted by multiple environmental factors. Given the rapid increase in asthma prevalence, it is difficult to ascribe the change to a genetic alteration. Therefore, the focus for understanding the changing prevalence of asthma must be on environmental factors. This article reviews factors which may contribute, in whole or in part, to the development of the disease process. In questioning whether it is possible to prevent development of a disease (primary prevention), it is critical to understand these factors. The environment may even have an impact on the fetus during intrauterine life. There does appear to be a "window of opportunity" in early life where a variety of factors, including food and inhalant allergen exposure, exposure to pollutants, and infection with both viral and bacterial agents, may be important in initiating the development of asthma and allergy. Potential approaches to primary prevention of asthma and allergy must consider each of these important factors. Given that asthma is a multifactorial disease with both complex genetic and environmental components, it is unlikely that any single intervention will significantly decrease the prevalence of asthma.

Urbanization and the risk of asthma among schoolchildren in the Palestinian Authority

The aim of the present survey was to compare the prevalence of symptoms suggestive of asthma in boys and girls aged 6-7 and 13-14 years in a rural and an urban area in the West Bank. For this purpose, the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire was issued to 970 schoolchildren in the two regions. The response rate was 92.2%. The prevalences of ever wheezing in the urban and rural areas were 16.4% and 12.0%, respectively (p < 0.05); the 12-month prevalences of wheezing were 10.5% and 5.5%, respectively (p < 0.05); the prevalences of more severe wheeze were 4.5% and 1.7%, respectively (p < 0.05); and prevalences of diagnosed asthma were 4.2% and 2.8%, respectively (p = NS). When controlling for age by stratification, the significant association between prevalence rates and place of residence persisted in the 13-14-year age group. These results also show that the prevalence of asthma among Palestinian children is moderately high in comparison with that reported from developing countries, but lower than those reported from Western countries. This survey, the first epidemiological survey on asthma in the West Bank, demonstrates a marked difference between urban and rural areas. The findings emphasize the need for further study of the environmental determinants of the disease among Palestinian children.

International patterns of tuberculosis and the prevalence of symptoms of asthma, rhinitis, and eczema

BACKGROUND

An ecological analysis was conducted of the relationship between tuberculosis notification rates and the prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and atopic eczema in 85 centres from 23 countries in which standardised data are available. These essentially comprised countries in Europe as well as the USA, Canada, Australia, and New Zealand.

METHODS

Tuberculosis notification rates were obtained from the World Health Organization. Data on the prevalence of symptoms of asthma, rhinitis, and eczema in 235 477 children aged 13-14 years were based on the responses to the written and video questionnaires from the International Study of Asthma and Allergies in Childhood (ISAAC). The analysis was adjusted for gross national product (GNP) as an estimate of the level of affluence.

RESULTS

Tuberculosis notification rates were significantly inversely associated with the lifetime prevalence of wheeze and asthma and the 12 month period prevalence of wheeze at rest as assessed by the video questionnaire. An increase in the tuberculosis notification rates of 25 per 100 000 was associated with an absolute decrease in the prevalence of wheeze ever of 4.7%. Symptoms of allergic rhinoconjunctivitis in the past 12 months were inversely associated with tuberculosis notification rates, but there were no other significant associations with other ISAAC questions on allergic rhinoconjunctivitis or atopic eczema.

CONCLUSIONS

These findings are consistent with recent experimental evidence which suggests that exposure to Mycobacterium tuberculosis may reduce the risk of developing asthma.

Absence of relationship between tuberculin reactivity and atopy in BCG vaccinated young adults

BACKGROUND

An inverse association between tuberculin responses and atopy has been observed in Japanese children, indicating that BCG immunisation, subclinical exposure to Mycobacterium tuberculosis without clinical disease, or host characteristics may influence the T helper (Th) lymphocyte balance with decreased atopy as a result. This study was undertaken to determine whether tuberculin reactivity is inversely related to atopy in young adults vaccinated with BCG at the age of 14.

METHODS

Men and women aged 20-44 years were tested using the adrenaline-Pirquet test with Norwegian produced synthetic medium tuberculin (n = 891). In addition, their serum total and specific IgE antibodies against mite, cat, timothy grass, mould and birch were measured.

RESULTS

Of the 574 subjects with complete examinations, 64% had a positive adrenaline-Pirquet tuberculin test (> or =4 mm) and 27% exhibited IgE antibodies (> or =0.35 kU/l) to one or more of the five specific allergens. The geometric mean of total serum IgE in the population was 30.2 kU/l. Tuberculin reactivity and log IgE were not correlated (r = 0.043, p = 0.30). The mean tuberculin reactivity was 4.6 mm, 4.9 mm, and 5.0 mm in the lower, middle and upper tertile of IgE distribution (<14 kU/l, 14-61 kU/l, >61 kU/l). The prevalence of atopy, as assessed by either the presence of any of the five specific IgE antibodies or by each specific IgE antibody separately, did not differ between subjects with a positive and those with a negative tuberculin test. These results persisted after adjustment for age, sex, and smoking status in multivariate logistic regression analyses.

CONCLUSIONS

In this young adult population, BCG vaccinated at the age of 14, no significant relationship between a positive tuberculin reaction and atopy was observed. If a true relationship had been found, our study suggests that it may be limited to populations immunised in early childhood when a substantial modulation of the immune system can occur.

Development of an asthma vaccine: research into BCG

Asthma is an atopic disorder characterised by the activation and recruitment of eosinophils to the lung resulting in chronic swelling and inflammation of the airways. Allergic disorders such as atopic asthma and dermatitis have been increasingly prevalent in developed countries, and the inverse correlation between exposure to major diseases such as tuberculosis and atopy prevalence has been reported. Intranasal administration of Mycobacterium bovis-Bacillus Calmette-Guerin (BCG) has been demonstrated to suppress airway eosinophilia in a model of atopic asthma. This immunomodulation is attributed to the ability of interferon (IFN)-gamma produced by BCG-specific T(H)1 lymphocytes to inhibit the development of lung T(H)2 responses such as airway eosinophilia. The mechanism of IFNgamma-induced inhibition is yet to be defined, but could involve activation of macrophages, direct suppression of developing T(H)2 lymphocytes, or altered dendritic cell activation and antigen presentation. Mycobacteria such as BCG and certain mycobacterial fractions are strong inducers of a T(H)1 immune response. The effectiveness of BCG in inhibiting atopic airway eosinophilia suggests its potential as a useful therapeutic agent in the treatment of atopic asthma.

NOVEL THERAPEUTIC APPROACHES FOR ALLERGIC RHINITIS

The last 2 decades have witnessed enormous changes in our understanding of allergic rhinitis. As we have begun to unravel the complex underlying immunologic and inflammatory pathophysiology of the disease, new therapeutic strategies as well as specific molecular and cellular constituents have emerged as potential targets for clinical intervention. These efforts also have shed light on the mechanisms by which current antiallergy medications act—or sometimes fail to be effective.7, 31, 51, 89 The similar pathophysiologic basis for allergic rhinitis and the often comorbid condition, asthma, was underscored in the recently published American Thoracic Society Workshop Summary on the Immunobiology of Asthma and Rhinitis: Pathogenic Factors and Therapeutic Options.¹⁸ In his conclusion, workshop chair, Thomas Casale,¹⁸ counsels readers to consider that “…allergic asthma and rhinitis represent a systemic disease affecting two organs, the lung and the nose. Asthma and allergic rhinitis share many of the same pathogenic factors, but they operate in different parts of the airway. Inflammatory cells and mediators are often the same, and there may be common alterations that occur in the immune system.” Thus, therapeutic strategies and potential therapeutic agents found to be beneficial in the treatment of one airway target may show similar effects in the other. For this reason, and because many of the therapies now being developed are at early stages in their evolution, physicians interested in rhinitis therapy also must examine what is known about these agents in asthma.

One avenue of active research has been the role of leukotrienes and other mediators in the pathophysiology of asthma and rhinitis. Three leukotriene modifiers now have been approved for the treatment of asthma in the United States; their potential use in the treatment of rhinitis has been a focus of considerable speculation and investigation. An early “day in the park” study showed that with antileukotriene therapy, patients with rhinitis had demonstrable improvements in their rhinitic symptoms.²⁹ Roquet et al⁸³ reported that in the treatment of asthma, there was a synergistic effect when an antileukotriene agent and an antihistamine were used, compared with either drug alone. A product combining an antileukotriene with an antihistamine is currently under development.

The most exciting developments, however, may be in the immunology arena. As described by Baraniuk elsewhere in this issue, the pathophysiology of allergic rhinitis is highly complex. Multiple interacting, interdependent, and redundant pathways and molecular and cellular constituents are involved in the pathogenesis of allergic rhinitis.

Briefly, exposure of the nasal mucosa to allergen in a sensitized individual leads to the release and further production of inflammatory mediators and the release of cytokines.⁵ These released cytokines activate endothelial cells, thereby inducing expression of adhesion receptors on the cell surface and initiating a cascade of events that facilitates transendothelial migration of inflammatory cells. T lymphocytes also are activated by these cytokines. Within a given tissue, specific patterns of cytokines are released, dependent on the dominant subset of local T lymphocytes. These, in turn, lead to the preferential activation and recruitment of specific inflammatory cells and the characteristic cellular inflammation observed in allergic rhinitis.

Early BCG vaccination and reduction in atopy in Guinea-Bissau

BACKGROUND

It has been proposed that certain viral and bacterial infections in early childhood may prevent allergic sensitization, by inducing Th1-type immune responses. This has led to speculation that mycobacterial vaccines might, through their Th1-stimulating properties, also protect against atopy.

OBJECTIVE

To investigate whether the prevalence of atopy is lower in children who have been vaccinated with BCG in infancy than in children who have not been vaccinated.

METHODS

We measured skin test reactivity to three allergens (Dermatophagoides pteronyssinus, D. farinae and cockroach) in 400 children, aged 3-14 years, as part of a follow-up study to examine the immune sequelae of measles in an urban area of Bissau, the capital of Guinea-Bissau in west Africa. Information on childhood vaccinations, including BCG in infancy, was available from child records. Of these children, 271 had been vaccinated with BCG (according to records) and 53 had not been vaccinated (no record and no BCG scar). Atopy was defined in two ways, according to the presence of any allergen reaction > or = 2 mm and any reaction > or = 3 mm.

RESULTS

Of the children who had received BCG vaccine, 57 (21%) were atopic (any reaction > or = 2 mm), compared with 21 (40%) of the unvaccinated children [odds ratio, after controlling for potential confounding factors, 0.19 (95% CI 0.06-0.59)]. When atopy was defined using the 3-mm criterion, the reduction in atopy associated with BCG was greater the earlier the age at vaccination, and the largest reduction was seen in children vaccinated in the first week of life.

CONCLUSION

BCG vaccination given early in infancy may prevent the development of atopy in African children.

Use of CpG DNA for enhancing specific immune responses

CpG ODN, owing to its wide range of immunostimulatory effects has been found to be a potent Th1-type adjuvant that is effective with virtually any type of antigen, although responses are less impressive with PS than protein antigens. The use of CpG ODN as an adjuvant may allow the development of vaccines against a wider range of diseases, which could include therapeutic vaccines for chronic infections or cancer, effective pediatric vaccines for newborns, and easily delivered mucosal vaccines.

Immune responses against replication-deficient adenovirus inhibit ovalbumin-specific allergic reactions in mice

Replication-deficient adenovirus vector (Ad) is one of the most efficient gene transfer vehicles for human gene therapy. However, Ad is antigenic, known to evoke prominent inflammatory responses in vivo, and there are concerns that using Ad in patients with immune-mediated disorders (allergy and autoimmune diseases) may affect the status of the diseases. To evaluate this concept in a manner close to clinical scenarios, a mouse model of airway eosinophilic inflammation was developed by administering intraperitoneal injections and inhalations of chicken ovalbumin (OA), with Ad administered intranasally 5 days after the OA sensitization. The administration of Ad resulted in a significant suppression of eosinophil counts in peripheral blood as well as in the bronchoalveolar lavage fluid (BALF), and a decrease in OA-specific IgE. The decrease in the number of eosinophils in BALF was associated with a marked upregulation of interferon gamma (IFN-gamma) expression. In contrast, the Ad-specific, delayed-type hypersensitivity response and efficacy of reporter gene expression mediated by Ad were only marginally affected in animals sensitized with OA. Together, these data support the idea that Ad administration in patients with Th2-mediated immune disorders does not exacerbate the parameters of ongoing inflammations or gene transfer efficiency, and with its ability to induce prominent type 1 immune response to the antigen in vivo, Ad could potentially be used as an efficient adjuvant to control immune disorders where Th2 cell-mediated mechanisms are involved.

CpG DNA induces stronger immune responses with less toxicity than other adjuvants

The ability to augment protective immune responses with minimal side effects is quintessential for a good adjuvant. This study has compared various adjuvants that are used in animal research (Freund's complete and incomplete adjuvants, Titermax Gold), are licensed for human use (alum), or are in clinical testing for humans (monophosphoryl lipid, CpG DNA), for their ability to augment humoral responses to a model antigen (hepatitis B surface antigen) and for the degree of damage they caused in the injected muscle. According to the data, the adjuvant combination CpG DNA+alum had the greatest potential to augment immune responses with minimal side effects at the injection site. Evaluation of antibody isotypes indicated Th2 responses (no IgG2a) with all adjuvants except monophosphoryl lipid and CpG DNA, which gave mixed Th1/Th2 responses (IgG1 and IgG2a). Strong Th1 responses (predominantly IgG2a) were obtained with combinations of CpG DNA with other adjuvants.

The polyprotein lipid binding proteins of nematodes

The nematode polyprotein allergens/antigens (NPAs) are specific to nematodes, and are synthesised as tandemly repetitive polypeptides comprising 10 or more repeated units. The polyproteins are post-translationally cleaved at consensus sites to yield multiple copies of the approximately 15-kDa NPA units. These units can be highly diverse in their amino acid sequences, but absolutely conserved signature amino acid positions are identifiable. NPA units are helix-rich and possibly fold as four helix bundle proteins. The NPA units have relatively non-specific lipid binding activities, binding fatty acids and retinoids, with dissociation constants similar to those of lipid transport proteins of vertebrates. Fluorescence-based analysis has indicated that, like most lipid transport proteins, the ligand is taken into the binding site in its entirety, but the binding site environment is unusual. NPAs are synthesised in the gut of nematodes, and presumably act to distribute small lipids from the gut, via the pseudocoelomic fluid, to consuming tissues (muscles, gonads, etc.). In some species, one of the units has a histidine-rich extension peptide which binds haems and certain divalent metal ions. NPAs appear to be released by parasitic nematodes, and may thereby be involved in modification of the local inflammatory and immunological environment of the tissues they inhabit by delivering or sequestering pharmacologically active lipids - they are known to bind arachidonic acids and some of its metabolites, lysophospholipids, and retinoids. NPAs are the only known lipid binding protein made as polyproteins, and are exceptions to the rule that repetitive polyproteins are only produced by cells undergoing programmed cell death and producing specialist products.

Urbanization and childhood asthma: an African perspective

The increasing prevalence of childhood asthma in the developed world is a cause for concern. Much research is currently being conducted in an attempt to identify possible reasons for this occurrence. A so-called Western lifestyle has been the factor most commonly cited to explain this worrying increase in asthma prevalence. In essence, this implies a way of life where children are exposed from early infancy to a wide range of foods, infections, indoor and outdoor allergens, and irritants and to the effects of motor vehicle pollution. Until fairly recently, children in many African countries lived mainly in rural areas and were not exposed to the effects of a Western lifestyle. Early studies in a limited number of African countries showed a very low rural prevalence of childhood asthma, especially where children lived according to a traditional lifestyle. These same studies showed that asthma was not uncommon in urbanized African children. There has been an increasing tendency over the past 20 years for those in rural communities to move to the large urban centers. More recent childhood asthma prevalence studies, especially those from Kenya and Ghana, have confirmed the urban-rural differences but have shown a much narrower gap. In part this may be the result of exposure of rural children to agricultural pesticides and irritants as well as of an increasing tendency to adopt a more Westernized lifestyle such as the use of beds with mattresses, pillows, and blankets. These circumstances on the African continent provide a natural laboratory in the quest for factors that influence the development of asthma in susceptible children. Once more fully elucidated, it is possible that much valuable information will be available to combat the relentless increase in childhood asthma both here as well as in the developed world.

Bronchial asthma: information on phytotherapy with essential fatty acids. Interactions between essential fatty acids and steroid hormones

The pharmacological treatment of bronchial asthma is based on the inhalation of bronchodilative beta2 agonists and steroid hormones. In view of the therapeutic successes obtained with evening primrose oil in the treatment of neurodermatitis in children, the question arises whether this phytotherapeutic substitution therapy could at least partly replace symptomatic pharmacotherapy in bronchial asthma. It is shown that this will only be successful if one dispenses with the anti-inflammatory effect of the treatment with steroid hormones.

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.