Incidence of atopic disease in a tropical environment: partial independence from intestinal helminthiasis

Lack of iron, zinc, and vitamins as a contributor to the etiology of atopic diseases

Micronutritional deficiencies are common in atopic children suffering from atopic dermatitis, food allergy, rhinitis, and asthma. A lack of iron, in particular, may impact immune activation with prolonged deficiencies of iron, zinc, vitamin A, and vitamin D associated with a Th2 signature, maturation of macrophages and dendritic cells (DCs), and the generation of IgE antibodies. In contrast, the sufficiency of these micronutrients establishes immune resilience, promotion of regulatory cells, and tolerance induction. As micronutritional deficiencies mimic an infection, the body's innate response is to limit access to these nutrients and also impede their dietary uptake. Here, we summarize our current understanding of the physiological function of iron, zinc, and vitamins A and D in relation to immune cells and the clinical consequences of deficiencies in these important nutrients, especially in the perinatal period. Improved dietary uptake of iron is achieved by vitamin C, vitamin A, and whey compounds, whereas zinc bioavailability improves through citrates and proteins. The addition of oil is essential for the dietary uptake of beta-carotene and vitamin D. As for vitamin D, the major source comes via sun exposure and only a small amount is consumed via diet, which should be factored into clinical nutritional studies. We summarize the prevalence of micronutritional deficiencies of iron, zinc, and vitamins in the pediatric population as well as nutritional intervention studies on atopic diseases with whole food, food components, and micronutrients. Dietary uptake via the lymphatic route seems promising and is associated with a lower atopy risk and symptom amelioration. This review provides useful information for clinical studies and concludes/emphasizes that a healthy, varied diet containing dairy products, fish, nuts, fruits, and vegetables as well as supplementing foods or supplementation with micronutrients as needed is essential to combat the atopic march.

The impact of modernization on allergy and asthma development

Background: In recent years, an increase of allergies and asthma has been observed throughout the world, more so in Western countries than in less developed ones. Although genetics may play a role in this increase, there are many other factors that may have contributed to the upsurge. Objective: The purpose of the present report was to review the many factors associated with modernization and lifestyle that may have contributed to the allergy and/or asthma epidemic, with a particular focus on those aspects that have particular relevance for the allergist/immunologist. Results: The marked rise in allergy and asthma has been significantly seen in more-developed countries, greater in urban than in rural areas, more pronounced in affluent than in poorer societies, and in individuals who have migrated from developing countries to industrialized countries. A widely accepted explanation for this rise is the "hygiene hypothesis," which postulates a critical dependence on microbial infection for maintenance of a healthy balanced immune system and that extremely clean external environments, often found in the developed world, can derail equilibrated immune development. With the control of infectious diseases, the immune system shifts from a balanced equilibrated immunologic structure to a more Th2 driven proinflammatory state often associated with IgE and eosinophil-related disorders. Conclusion: Modernization has been associated with increased development of allergies and asthma through a cleaner environment and more exposure to allergens and to multiple other contributory factors. The marked reduction in infectious diseases in recent decades permitted the immune system to switch from fighting infectious disease agents and parasites to reacting adversely (hypersensitivity) to benign environmental agents (allergens) and even to self-antigens (autoimmunity).

Urbanisation and asthma in low-income and middle-income countries: a systematic review of the urban-rural differences in asthma prevalence

BACKGROUND

Urbanisation has been associated with temporal and geographical differences in asthma prevalence in low-income and middle-income countries (LMICs). However, little is known of the mechanisms by which urbanisation and asthma are associated, perhaps explained by the methodological approaches used to assess the urbanisation-asthma relationship.

OBJECTIVE

This review evaluated how epidemiological studies have assessed the relationship between asthma and urbanisation in LMICs, and explored urban/rural differences in asthma prevalence.

METHODS

Asthma studies comparing urban/rural areas, comparing cities and examining intraurban variation were assessed for eligibility. Included publications were evaluated for methodological quality and pooled OR were calculated to indicate the risk of asthma in urban over rural areas.

RESULTS

Seventy articles were included in our analysis. Sixty-three compared asthma prevalence between urban and rural areas, five compared asthma prevalence between cities and two examined intraurban variation in asthma prevalence. Urban residence was associated with a higher prevalence of asthma, regardless of asthma definition: current-wheeze OR:1.46 (95% CI:1.22 to 1.74), doctor diagnosis OR:1.89 (95% CI:1.47 to 2.41), wheeze-ever OR:1.44 (95% CI:1.15 to 1.81), self-reported asthma OR:1.77 (95% CI:1.33 to 2.35), asthma questionnaire OR:1.52 (95% CI:1.06 to 2.16) and exercise challenge OR:1.96 (95% CI:1.32 to 2.91).

CONCLUSIONS

Most evidence for the relationship between urbanisation and asthma in LMICs comes from studies comparing urban and rural areas. These studies tend to show a greater prevalence of asthma in urban compared to rural populations. However, these studies have been unable to identify which specific characteristics of the urbanisation process may be responsible. An approach to understand how different dimensions of urbanisation, using contextual household and individual indicators, is needed for a better understanding of how urbanisation affects asthma.

PROSPERO REGISTRATION NUMBER

CRD42017064470.

Soil-transmitted helminth parasites and allergy: Observations from Ecuador

There is considerable interest as to potential protective effects of soil-transmitted helminths (STH) against allergy and allergic diseases. Here, we discuss findings of studies done of the effects of STH parasites on atopy and allergic diseases in Ecuador. While cross-sectional studies have consistently shown a reduced prevalence of allergen skin prick test (SPT) reactivity among infected schoolchildren, the removal of these infections by repeated deworming did not affect SPT prevalence over the short-term (ie, 12 months) but may have increased SPT prevalence over the long-term (ie, 15-17 years). In the case of allergic symptoms, cross-sectional studies have generally not shown associations with STH and intervention studies showed no impact on prevalence. However, a birth cohort suggested that early STH infections might reduce wheeze by 5 years. Allergic sensitization to Ascaris, however, explained a significant proportion of wheezing among rural schoolchildren. Studies of the effects of STH on immune and inflammatory responses indicated a potential role of STH in contributing to more robust regulation. The effects of STH on allergy are likely to be determined by history of exposure over the life-course and by interactions with a wide variety of other infectious and non-infectious factors.

Childhood Asthma Prevalence among Puerto Ricans and Mexican Americans: Implications for Behavioral Intervention Research

Parental management is the least understood, but often a vital, element of treatment effectiveness in childhood asthma. This study identifies individual, household, and community-level variables relevant to home treatment effectiveness among two Hispanic groups: Mexican Americans and Puerto Ricans. The relationship between these variables and lifetime prevalence of childhood asthma (LTP) are examined with data in the Hispanic Health and Nutrition Examination Survey, 1982-84 (HHANES), a mixed cross-sectional retrospective national survey. Unadjusted estimates indicate that Puerto Rican ethnicity, poverty, urban residence, and single parenthood are positively associated with LTP. Children born outside the mainland United States, children of low weight for age, and males show an increased risk of LTP In a multiple logistic regression model, Puerto Rican ethnicity, low weight for age, and male gender remain positively associated, and poverty becomes negatively associated, with LTP Implications are discussed for programs designed to assist children of Hispanic origin with asthma.

The interplay between diet and emerging allergy: what can we learn from Indigenous Australians?

The pathophysiology of atopic diseases, including asthma and allergy, is the result of complex gene-environment interactions. Since European colonization the Indigenous population of Australia has undergone significant changes with respect to their lifestyle as hunter-gatherers. These changes have had a detrimental effect on Aboriginal health, in part due to immunological modification. This review provides a comparative look at both the traditional Aboriginal/Indigenous diet and modern Western diets, examines some common allergies increasingly reported in contemporary Indigenous populations, and reviews concepts such the effect of vitamin deficiencies and changes in gut microbiota on immune function.

Mast cells as cellular sensors in inflammation and immunity

Mast cells are localized in tissues. Intense research on these cells over the years has demonstrated their role as effector cells in the maintenance of tissue integrity following injury produced by infectious agents, toxins, metabolic states, etc. After stimulation they release a sophisticated array of inflammatory mediators, cytokines, and growth factors to orchestrate an inflammatory response. These mediators can directly initiate tissue responses on resident cells, but they have also been shown to regulate other infiltrating immune cell functions. Research in recent years has revealed that the outcome of mast cell actions is not always detrimental for the host but can also limit disease development. In addition, mast cell functions highly depend on the physiological context in the organism. Depending on the genetic background, strength of the injurious event, the particular microenvironment, mast cells direct responses ranging from pro- to anti-inflammatory. It appears that they have evolved as cellular sensors to discern their environment in order to initiate an appropriate physiological response either aimed to favor inflammation for repair or at the contrary limit the inflammatory process to prevent further damage. Like every sophisticated machinery, its dysregulation leads to pathology. Given the broad distribution of mast cells in tissues this also explains their implication in many inflammatory diseases.

IgE cross-reactivity between Ascaris lumbricoides and mite allergens: possible influences on allergic sensitization and asthma

Nematode infections such as Ascariasis are important health problems in underdeveloped countries, most of them located in the tropics where environmental conditions also promote the perennial co-exposure to high concentrations of domestic mite allergens. Allergic diseases are common, and most of patients with asthma exhibit a predominant and strong IgE sensitization to mites. It is unknown whether co-exposure to Ascaris lumbricoides and the domestic mites Blomia tropicalis and Dermatophagoides pteronyssinus potentiates Th2 responses and IgE sensitization, thereby modifying the natural history of allergy. Recently, we obtained experimental evidence of a high cross-reactivity between the allergenic extracts of these invertebrates, involving well-known allergens such as tropomyosin and glutathione transferases. There is indirect evidence suggesting that the clinical impact of these findings may be important. In this review, we discuss the potential role of this cross-reactivity on several aspects of allergy in the tropics that have been a focus of a number of investigations, some of them with controversial results.

Reduced helminth burden increases allergen skin sensitization but not clinical allergy: a randomized, double-blind, placebo-controlled trial in Vietnam

BACKGROUND

Observational evidence suggests that infection with helminths protects against allergic disease and allergen skin sensitization. It is postulated that such effects are mediated by helminth-induced cytokine responses, in particular IL-10.

OBJECTIVE

We tested this hypothesis in a rural area of central Vietnam where hookworm infection is endemic.

METHODS

One thousand five hundred and sixty-six schoolchildren aged 6-17 were randomly allocated to receive either anti-helminthic therapy or a placebo at 0, 3, 6, and 9 months. We compared changes in the prevalence of exercise-induced bronchoconstriction, allergen skin sensitization, flexural eczema on skin examination, questionnaire-reported allergic disease (wheeze and rhinitis symptoms), and immunological parameters (hookworm-induced IFN-gamma, IL-5, IL-10) between 0 and 12 months.

RESULTS

One thousand four hundred and eighty-seven children (95% of these randomized) completed the study. The most common helminth infections were hookworm (65%) and Ascaris lumbricoides (7%). There was no effect of the therapy on the primary outcome, exercise-induced bronchoconstriction (within-participant mean percent fall in peak flow from baseline after anti-helminthic treatment 2.25 (SD 7.3) vs. placebo 2.19 (SD 7.8, P=0.9), or on the prevalence of questionnaire-reported wheeze [adjusted odds ratio (OR)=1.16, 95% confidence interval (CI) 0.35-3.82, P=0.8] and rhinitis (adjusted OR=1.39, 0.89-2.15, P=0.1), or flexural dermatitis on skin examination (adjusted OR=1.15, 0.39-3.45, P=0.8). However, anti-helminthic therapy was associated with a significantly higher allergen skin sensitization risk (adjusted OR=1.31, 1.02-1.67, P=0.03). This effect was particularly strong for children infected with A. lumbricoides at baseline (adjusted OR=4.90, 1.48-16.19, P=0.009). Allergen skin sensitization was inversely related to hookworm-specific IL-10 at baseline (adjusted OR=0.76, 0.59-0.99, P=0.04). No cytokine tested, including IL-10, changed significantly after the anti-helminthic therapy compared with the placebo.

CONCLUSION

A significant reduction in worm burden over a 12-month period in helminth-infected children increases the risk of allergen skin sensitization but not of clinical allergic disease. The effect on skin sensitization could not be fully explained by any of the immunological parameters tested.

Respiratory atopic disease, Ascaris-immunoglobulin E and tuberculin testing in urban South African children

BACKGROUND

Epidemiological relation of intestinal helminth infection and atopic disease, both associated with a T-helper (Th) 2 immune response, is controversial, as it has been reported that helminth infection may either suppress or pre-dispose to atopic disease. This relation has not been tested in an area with a high burden of Mycobacterium tuberculosis (MTB) infection, a known Th1-stimulating infection.

OBJECTIVE

To study the association of intestinal helminth infection and atopic disease in a community where helminth infection is endemic and MTB infection is high.

METHODS

Three-hundred and fifty-nine randomly selected children aged 6-14 years from a poor urban suburb were tested with allergy questionnaire, skin prick test (SPT) to common aeroallergens, Ascaris-specific IgE (Ascaris-sIgE), fecal examination for pathogenic intestinal helminths and tuberculin skin testing (TST). Histamine bronchoprovocation was tested in the group of children aged 10 years and older.

RESULTS

were corrected for demographic variables, socioeconomic status, parental allergy, environmental tobacco smoke (ETS) exposure in the household, recent anthelminthic treatment and for clustering in the sampling unit. Results Ascaris-sIgE was elevated in 48% of children, Ascaris eggs were found in 15% and TST was positive in 53%. Children with elevated Ascaris-sIgE had significantly increased risk of positive SPT to aeroallergens, particularly house dust mite, atopic asthma (ever and recent), atopic rhinitis (ever and recent) and increased atopy-related bronchial hyper-responsiveness. In children with negative TST (<10 mm), elevated Ascaris-sIgE was associated with significantly increased risk of atopic symptoms (adjusted odds ratio (OR(adj)) 6.5; 95% confidence interval (CI) 1.9-22.4), whereas in those with positive TST (>/=10 mm) this association disappeared (OR(adj) 0.96; 95% CI 0.4-2.8).

CONCLUSIONS

These results suggest that immune response to Ascaris (Ascaris-sIgE) may be a risk factor of atopic disease in populations exposed to mild Ascaris infection and that MTB infection may be protective against this risk, probably by stimulation of anti-inflammatory networks.

The role of parasitic infections in atopic diseases in rural schoolchildren

BACKGROUND

There is increasing evidence that the farming environment has a protective effect as regards allergic diseases. Exposure to animal parasites, particularly helminth infections, is common in the farming environment. However, the role of helminths in this environment is not well determined to date.

METHODS

This analysis focuses on 613 children 6-13 years of age from rural areas of Austria, Germany and Switzerland, who took part in the Allergy and Endotoxin (ALEX) study. Allergic diseases and farming characteristics were assessed by a standardized questionnaire and as a crude measure of possible exposure to helminths, IgG antibodies to Ascaris lumbricoides were measured.

RESULTS

Exposure to nematodes, as determined by the levels of antibody to A. lumbricoides, was more frequent among farmers' children than non-farmers' children (39.8%vs 31.1%, P = 0.03). This positive serology was found to be significantly associated with high total IgE levels [odds ratio (OR) = 3.05, 95% confidence interval (CI) = 1.81-5.12] and eosinophilia (OR = 2.84, 95% CI = 1.66-4.84). However, no association between anti-nematode serology and the prevalences of asthma, wheeze, hay fever or atopy was found. A weak association for atopy was observed after adjustment for total IgE.

CONCLUSION

Immunoglobulin G antibodies to A. lumbricoides, as a crude measure of possible exposure to helminths, did not indicate any protective effect against allergic diseases in this population. Although farmers' children had increased antibody levels reactive to helminth parasites indicating exposure, this did not explain the protective effect of farming against atopic diseases.

The role of helminth infections in protection from atopic disorders

PURPOSE OF REVIEW

The observation that allergies are less prevalent in developing countries, especially in rural areas, has stimulated considerable research to identify environmental factors associated with protection against allergic disorders. Here, we review recent studies conducted in developing countries.

RECENT FINDINGS

Epidemiological studies conducted in South America, Asia and Africa have attempted to identify factors associated with differences in prevalence of atopy, asthma and atopic dermatitis. Particular attention is given to the complex relationship between helminth infections and allergies. In answer to the question of whether helminth infections are associated with protection against allergic disorders, conflicting data have been generated. In addition to epidemiological studies, animal models have been utilized to gain insight into the immunological mechanisms involved in the interaction between helminth infections and allergies. These animal studies are discussed. The possible explanations for discrepancies found within both human and murine studies have been considered, highlighting the need for further research.

SUMMARY

An in-depth understanding of the relevant protective mechanisms against allergic disorders will open the possibility of developing novel therapeutics to prevent the allergic march worldwide.

Toxocara infection seroprevalence and its relationship with atopic features in a general adult population

BACKGROUND

The relationship of helminth infection with atopy is controversial. Toxocariasis is the most common helminth infection in industrialized countries. The study aimed to investigate the association between Toxocara exposure and atopic features.

METHODS

The study is based on a cross-sectional survey of 463 subjects, randomly selected (stratified by decades of age) from a general adult population. Toxocara exposure was defined by the presence of serum Toxocara antibodies. Main outcome measures included total serum IgE levels, skin prick tests (SPT) to a panel of 13 relevant aeroallergens, specific IgE to aeroallergens (Phadiatop test), and respiratory symptoms evaluated by means of a questionnaire.

RESULTS

A total of 134 subjects (weighted proportion 28.6%, 95% CI 26.5-30.7%) showed Toxocara exposure. Pet ownership, rural habitat, farming, and low educational level were associated with Toxocara exposure. Toxocara exposure was associated with both positive SPT (particularly to mites) and positive specific IgE (Phadiatop test) after adjusting for potential confounders. The effect of Toxocara exposure on total serum IgE levels and blood eosinophil count was different in SPT-positive subjects and SPT-negative individuals. In SPT-negative individuals, Toxocara exposure was associated with an increase in both serum IgE levels and eosinophil counts, whereas an opposite trend was observed in SPT-positive individuals. Toxocara exposure was not associated with respiratory symptoms.

CONCLUSIONS

In this adult population, Toxocara exposure is associated with allergic sensitization, particularly to mites. There is evidence of an intriguing interaction between Toxocara exposure and allergic sensitization for both total serum IgE levels and blood eosinophil counts.

Atopy is a risk factor for non-steroidal anti-inflammatory drug sensitivity

BACKGROUND

There is scarce information in the literature about a possible association between atopy and certain clinical manifestations of NSAID sensitivity.

OBJECTIVES

(1) To evaluate the prevalence of atopy in patients proved to be sensitive to cyclooxygenase inhibitors. (2) To assess cross-reactivity to two alternative NSAIDs, paracetamol (acetaminophen) and nimesulide.

METHODS

NSAID-sensitive patients attending an allergy clinic and unselected controls were prick tested with inhalant allergens. Oral challenges with NSAIDs were carried out by the single-blinded (SBOC) method. Clinical data about personal and family history of allergic and atopic diseases were obtained by a careful review of the medical records and by direct questioning by experienced allergists.

RESULTS

Fifty patients had positive SBOCs to the suspected NSAID and only these were studied. A personal history of atopic diseases was present in 41 patients (82%) and 7 controls (14.5%), and a family history in 24 patients (48%) and 6 controls (12.5%). Prick skin tests with aeroallergens were positive in 39 of 45 patients tested (86.6%) and in 14 of 48 controls (29.1%), (P = .0001). Skin test positivity rates were higher in patients with cutaneous challenge reactions who responded to only one NSAID (single reactors) in comparison to cross-reactors (P = .04). The most frequent clinical manifestations of NSAID sensitivity were (1) cutaneous (angioedema, urticaria) in 34 patients, (2) blended (cutaneous plus respiratory) in 12, (3) respiratory in 3, and (4) anaphylactoid in 1. Aspirin, pyrazolone, paracetamol, and ibuprofen were the drugs more frequently implicated in these reactions. Cross-sensitivity with paracetamol and nimesulide were 32% and 25%, respectively.

CONCLUSIONS

The prevalence of atopy is increased in challenge-proven NSAID-intolerant patients. The atopic condition may represent an important risk factor for developing reactions to these drugs. Paracetamol and nimesulide are relatively safe alternative choices in those patients, although their use still carries some risk of unwanted reactions.

Allergic disease in teenagers in relation to urban or rural residence at various stages of childhood

BACKGROUND

Higher prevalences of allergic diseases and IgE antibodies to inhalant allergens have been reported for persons living in urban areas than for persons living in rural areas.

METHODS

Associations between cumulative incidences of allergic diseases in 1878 children aged 13-14 years and their place of residence (urban, semiurban, or rural) from birth were assessed by questionnaire (ISAAC), in order to find out whether there is a period of increased sensitivity to external influences during the first few years of life. Family history and exposure to pets, tobacco smoke, and damp were considered in multiple regression.

RESULTS

There was a significantly higher prevalence of allergic diseases with urban residence than with rural residence during the first 2 years of life (e.g., for bronchial asthma, relative risk (RR) for the first year 2.1, 95% CI 1.2-3.7). An increased risk was still found after multiple regression (RR=1.7). Semiurban residence was associated with an intermediate cumulative incidence of allergic diseases. Maternal smoking during pregnancy was associated with asthma (RR=1.4, 95% CI 1.0-2.0).

CONCLUSIONS

The findings support a period of increased susceptibility during the first years of life. Whether rural lifestyle protects against allergy or whether urban pollutants contribute to allergy has to be elucidated [corrected].

Differences of genetic effects for the development of allergic diseases in two cities of Japan

BACKGROUND

Differences in the effects of genetic factors on allergic diseases in two areas of the same race within the same country have not been studied with multiple logistic regression.

OBJECTIVE

To determine whether the effects of genetic factors on allergic diseases differ between two areas.

METHODS

A questionnaire provided information about family histories of allergic diseases and environmental factors was distributed to children attending kindergarten, elementary, or junior high school in two Japanese cities: Gifu, with a temperate climate, and Itoman, with a subtropical one. The number of subjects analyzed were 1,243 in Gifu and 1,953 in Itoman. Multiple logistic regression analysis was performed with SAS.

RESULTS

Multiple logistic regression analysis showed that in both cities children of families with allergic histories have significantly higher risk of contracting allergic disease and atopic dermatitis, even after being controlled for environmental factors. In Gifu, in families where both parents suffered from allergy, there was a higher incidence of allergic diseases than when only one of the parents was suffering from it. On the other hand, in Itoman there were no differences of relative risk between paternal history and maternal history.

CONCLUSIONS

We speculated that there are some differences of genetic factors between different areas of the same country, and these differences of genetic effects may influence on the difference of the prevalence of allergic diseases as well as the environmental factors.

Ascaris-specific IgE and allergic sensitization in a cohort of school children in the former East Germany

BACKGROUND

Helminthic infections induce an IL-4-dependent polyclonal stimulation of IgE synthetization. It is still unclear, however, what role helminths play in allergic sensitization.

OBJECTIVE

We sought to determine the relationship between Ascaris-specific IgE and allergic sensitization in a nontropical country.

METHODS

In 2 consecutive cross-sectional surveys in 1992-1993 and 1995-1996, data from school entrants (age range, 5 to 7 years), third graders (age range, 8 to 10 years), and sixth graders (age range, 11 to 14 years) were collected. The 2 younger groups were reexamined in the second survey. Data for about 2300 children, including a cohort of 700 subjects, were analyzed. Ascaris IgE and total and specific IgE to inhalant allergens were measured, and skin prick tests were performed. Information about asthma and allergic rhinitis was collected by a questionnaire.

RESULTS

Children who were Ascaris-IgE seropositive (>0.35 IU/mL) in both surveys had 10-fold higher levels of total IgE (451 IU/mL vs 45 IU/mL, P < .001) and higher prevalence rates of allergen-specific IgE seropositivity (56.3% vs 26.6%, P < .001). They also had a higher prevalence of allergic rhinitis (12.6% vs 3.7%, P < .001) and asthma (5.7% vs 1.6%, P < .05). In subjects who were Ascaris-seronegative in the first survey but seropositive in the second survey, total and specific IgE increased markedly. Sensitization to Dermatophagoides pteronyssinus increased nearly 3-fold in this group. In contrast, in children who became Ascaris-seronegative, total and specific IgE decreased.

CONCLUSIONS

Contact with low doses of helminthic antigen is associated with an increase of total and specific IgE production. Helminthic infections in East German children are not the cause for a low prevalence of allergies in the former East Germany.

The development of atopic sensitization in Estonian infants

In a prospective study, 251 infants were followed from birth up to 12 months of age, recording manifestations of allergy by questionnaires at 3, 6, 9 and 12 months and by clinical examinations at 6 and/or 12 months. Blood samples were obtained at birth and at 6 and 12 months and analysed for serum IgE levels. The children were skin-prick tested with foods at 6 and 12 months of age and with inhalant allergens at 12 months. Blood samples from SPT-positive individuals and controls were analysed for the presence of IgE antibodies to common inhalant allergens and their cord sera for the presence of IgE antibodies to cow's milk and egg. Twelve infants (7%) were sensitized against foods [3 to cow's milk (CM) and 9 to egg white (EW)] at 6 months and 11 (5%) (2 to CM and 9 to EW) at 12 months. Seventeen infants (7%) had IgE antibodies against inhalant allergens at 6 and/or 12 months, as determined by either SPT and/or the demonstration of circulating IgE antibodies. Out of 30 children with positive SPT and/or circulating IgE antibodies against foods and inhalant allergens at any age, 6 had atopic dermatitis, 4 gastrointestinal food allergy, 1 urticaria and 4 probable allergy, while 15 had no clinical manifestation of allergy. Immunoglobulin E antibodies against Ascaris were detected in 17% of the infants with S-IgE levels > 20 kU/l. The study indicates that the incidence of sensitization and manifestations of allergic disease is similar among Estonian and Scandinavian infants during the first year of life. Given earlier findings indicating a significantly higher prevalence of atopic disease in Scandinavian school-children relative to their counterparts in Eastern Europe, the present study suggests that the key events which determine disease expression do not occur exclusively during the first year of life.

Asthma, allergy and atopy in Asian immigrants in Melbourne

OBJECTIVES

To compare the prevalence of asthma, hay fever and atopy in Asian immigrants in Melbourne with that in Australian-born non-Asians and Australian-born Asians, and to investigate the association of these conditions with atopic status, length of stay in Australia and IgE levels in Asian immigrants.

DESIGN

We performed a cross-sectional study by telephone interviews, using standard questionnaire items on respiratory and allergic symptoms. A random sample of 636 recent Asian immigrants of ethnic Chinese origin, 109 Australian-born Asians and 424 Australian-born non-Asians were selected from the 1991 Melbourne Telephone Directory, using a presumptive surname list. Skin tests to determine atopic status were performed on 269 Asian immigrants and 167 of these also had serum levels of total and specific IgE estimated.

RESULTS

In the under 20 years age group the prevalence of wheeze or asthma ever was higher in Australian-born non-Asians and Australian-born Asians than in Asian immigrants (P < 0.001), and the prevalence of hay fever was higher in Asian immigrants and Australian-born Asians than in Australian-born non-Asians. In those older than 20 years, hay fever was almost twice as common in Asian immigrants as in Australian-born non-Asians (P < 0.001 for 20-40 years age group; P < 0.01 for > 40 years). The prevalence of hay fever and, to a lesser degree, asthma in Asian immigrants increased significantly with length of stay in Australia, independent of age at arrival, sex and atopic status (trend test: P < 0.001 for hay fever; P = 0.05 for asthma). Atopy was more common in Asian immigrants and Australian-born Asians than in Australian-born non-Asians (P < 0.001) and was very strongly associated with both hay fever and asthma, irrespective of length of stay. Pollen and mite sensitivities were more common in Asian subjects (twice as common for Asian-born and 1.5 times for Australian-born) than non-Asian subjects (P < 0.01). Among Asian immigrants, elevated total IgE level (> 100 IU/mL) was strongly associated with a history of hay fever (P < 0.01) and wheeze or asthma ever (P < 0.05), atopy (P < 0.001) and the presence of specific IgE antibodies to grass pollen, dust mite, cockroach and Ascaris antigens (P < 0.05 for all).

CONCLUSION

We found substantial differences in the prevalence of asthma, hay fever and atopy between Asian immigrants, Australian-born Asians and non-Asians. The prevalence of hay fever and asthma in Asian immigrants was strongly associated with length of stay in Australia, suggesting that environmental factors are important in the pathogenesis of these diseases.

Personal NO2 exposure monitoring shows high exposure among ice-skating schoolchildren

A method for measuring personal nitrogen dioxide (NO2) exposure, using passive samplers, was tested among schoolchildren. Activity patterns and NO2 exposure levels were studied in relation to urban and rural living. Stationary air monitoring data indicated that the urban children were supposed to be exposed to NO2 levels that were among the highest in Sweden. It was shown that NO2 levels measured at the stationary air monitoring station were not representative for the children's exposure. The children spent 90% of their time indoors; only a small percentage of their time was spent in transit. The median daily NO2 exposure level in the urban area (13 micrograms NO2/m3, 7 ppb) was significantly higher (p < .001) than in the rural area (7 micrograms NO2/m3, 4 ppb). The most important source of exposure was the indoor ice-skating arenas, where levels up to 8,000 micrograms NO2/m3 (4 240 ppb) were measured during 1-h periods.

An epidemiological study of atopy in children

A sample of 930 children, between 9 years and 15 years old from six Italian towns, were studied. Their family history of allergy, personal allergy and medical history, current allergy symptoms, exposure to environmental allergens, feeding as infants, and their parents' occupations were recorded. They were skin-prick tested (SPT) with a range of common allergens. A subject was defined as atopic if at least one SPT caused a weal greater than 3 mm diameter. The association between the recorded information and atopy was investigated by logistic multiple regression. Atopy was positively associated with: high density housing; medium or high exposure to environmental allergens; a history of rhinitis, asthma or atopic eczema; male gender; and a history of breastfeeding. It was independent of infectious diseases, vaccinations and operations, social class and family history. Thus, there was no evidence of a genetic factor in atopy, other than sex.

Specificity of Toxocara ELISA in tropical populations

The diagnosis of human infection by Toxocara canis relies heavily upon serological tests, the specificity of which can be inadequate in regions of endemic helminthiasis. When different population groups of tropical Venezuela were evaluated using ELISA based upon Toxocara excretory-secretory antigen (TcESA), solid-phase adsorption of the sera with extracts of a wide variety of non-homologous parasites revealed the existence of significant cross-reactivity. This was effectively and conveniently overcome when the test sera were incubated in the presence of the soluble parasite extracts in a competitive inhibition ELISA. The mean reduction of ELISA values caused by pre-adsorption of the sera tested was 32.2%, and that caused by competitive inhibition was 42.3%, the effects of these two procedures being strongly correlated (r = 0.83). The magnitude of the reduction was inversely proportional to the actual ELISA value (r = -0.55), and ranged from a mean of 68.0% in sera from apparently healthy individuals of medium-high socio-economic level, down to 28.1% in heavily parasitized Amazon indians. Ascaris showed the greatest degree of cross-reactivity in these tests, although under conditions of competitive inhibition even sera with high levels of antibody against this parasite could be negative in Toxocara ELISA. Western blotting revealed a major 81,400 D component that was shared between Ascaris and TcESA. Our results indicate that the competitive inhibition of cross-reactivity by soluble non-homologous parasite extracts provides a convenient and economical means of increasing the specificity of ELISA for the determination of the seroprevalence of toxocariasis in tropical populations.

Xenogeneic antibodies and atopic disease

Xenogeneic antibodies can survive food processing procedures with their biological activity intact and even enhanced. These antibodies can be absorbed from the human gut, and will function both as antigens and antibodies in the human immune system. Antibodies to bovine gamma globulins (BGG) have been detected in human sera and the family of anti-BGG antibodies must include anti-idiotypic antibodies, very low doses of which can influence the immune response. The hypothesis is that the human immune system may be primed by low-level exposure to xenogeneic antibodies specific for those human allergens which are ubiquitous in the farm environment, such as pollens, mites, and moulds, the result being a deleterious and inappropriate response on subsequent exposure to these allergens. Dairy products are the most important source of xenogeneic antibodies in the western diet, and the hypothesis may partly explain the association between cow's milk and allergies to substances other than milk proteins.

Seroprevalence of Toxocara canis infection in tropical Venezuela

An enzyme-linked immunosorbent assay (ELISA) was used to determine the seroprevalence of Toxocara canis infection in different socio-economic groups of the tropical population of Venezuela. The lack of definitive independent diagnostic criteria for toxocariasis required the establishment of operational upper limits of normality for Toxocara ELISA values, based upon their log-normalized distribution in a presumptive "non-toxocariasis" sub-population. Only 1.8% of urban subjects of medium-high socio-economic level were considered to be clearly positive in Toxocara ELISA, compared to 20.0% of urban slum dwellers, 25.6% rural subsistence farmers and 34.9% Amazon Indians. As the test was performed using excretory-secretory antigen, and under conditions of competitive inhibition by soluble extracts of non-homologous parasites, co-infection by common intestinal helminths, protozoa or other organisms did not give rise to false positive results. However, strong cross-reactivity with Onchocerca volvulus may have influenced the prevalence figure obtained for the Amazon Indians. These results indicate that T. canis is yet another parasite that is widely distributed in economically underprivileged tropical populations.

Allergic reactivity and socio-economic level in a tropical environment

As some factors associated with the tropical environment can modify the expression of atopic disease, various indicators of allergic reactivity were compared between allergic and non-allergic subjects of different socio-economic level in Caracas, Venezuela (Lat. 10 degrees N). The socio-economic levels considered were high (HSEL), medium-high (MSEL) or low (LSEL). As generally found in temperature climates, in the HSEL the total serum IgE levels of allergic patients were significantly greater than those of non-allergic individuals (geometric means of 274 vs 126 IU/ml, respectively), as were also the specific serum IgE antibody levels (55.6 vs 23.8% positive, respectively, for house dust). These results correlated closely with the skin-test reactivity of these subjects (60.3 vs 17.5% positive for house dust). In this group, the degree of intestinal helminthic infection was low (5.6% positive for Ascaris). In contrast, for the MSEL where the degree of parasitic infection was higher (13.0%), the total serum IgE levels were elevated in both allergic and non-allergic subjects (602 vs 363 IU/ml). Similarly, positivity for specific IgE antibody was high, and comparable between allergics and non-allergics of this group (61.5 vs 54.2%), as was also the case for skin-test reactivity (71.9 vs 60.4%). In the LSEL, parasitic infection was prevalent (47.6%), and the total serum IgE levels were markedly elevated, with little difference occurring between allergic and non-allergic individuals (2269 vs 1981 IU/ml). The positivity for specific IgE antibody was high, and effectively independent of the allergic state (75.6 vs 53.7%), but in contrast the skin test reactivity was relatively low (22.0 vs 9.8%).(ABSTRACT TRUNCATED AT 250 WORDS)

Preventive role of atopy in lung cancer

Incidence of atopic disease, serum and sputum IgE, and sputum IgA levels were studied in lung cancer patients, and compared with those in lung benign disease patients and normal controls. A significantly lower prevalence of personal atopic history was observed in the cancer group in comparison with the other two experimental groups. Patients with lung cancer showed significantly higher serum IgE levels than benign-disease and normal control individuals. At the same time, patients with epidermoid lung carcinoma had significantly increased levels of serum IgE and sputum IgA than those with lung adenocarcinoma.

IgE antibody against surface antigens of Leishmania promastigotes in American cutaneous leishmaniasis

As IgE-mediated immune mechanisms participate in the host defence against some types of parasites, we evaluated sera from American cutaneous leishmaniasis (ACL) patients for the presence of this antibody against Leishmania. Using monoclonal antibodies against human IgE and an immunoperoxidase staining technique, 48% of the patients sera tested were found to contain IgE antibody that bound strongly to Leishmania promastigotes. A much lower proportion of sera from non-symptomatic subjects from either endemic or non-endemic areas of the disease contained significant levels of anti-Leishmania IgE antibody (6.5% and 0% respectively). The results indicated that the IgE antibody bound predominantly to surface components of the promastigotes, and reactivity against the intracellular amastigote form of the parasite was rarely detected. Somewhat unexpectedly, in a small proportion of the sera, the IgE antibody showed apparent specificity for L. mexicana or L. braziliensis. This study demonstrates that ACL patients can develop anti-Leishmania IgE antibody responses, that seem to be directed preferentially against surface antigens of promastigotes, and that can be strain specific. This raises the question as to the possible contribution of this antibody to the immune defence mechanisms against the parasite.