Measles and atopy in Guinea-Bissau

Age at childhood infections and risk of atopy

BACKGROUND

It has been proposed that early age at exposure to common childhood infections is associated with a decreased risk of allergy. Previous studies on the possible association between allergy and infection with measles, mumps, rubella, and varicella have not been conclusive as most did not include information on exact age at exposure. The objective of our study was to investigate whether early age at exposure to these infections was associated with a decreased risk of atopy using information on exact age at infection.

METHODS

The study population consisted of 889 pregnant women who participated in a national birth cohort study in Denmark and for whom detailed information on history of measles, rubella, varicella, and mumps before school entry (age 7 years) was available from school health records from Copenhagen. Atopic status was assessed serologically by a specific response to 11 common inhalant allergens using serum samples obtained from the women during pregnancy.

RESULTS

Measles in the first year of life was associated with a higher risk of atopy than no measles before age 7 years (OR 3.36, 95% CI 1.47 to 7.68). There was no association between atopy and mumps, rubella, or varicella in the first 7 years of life or with measles acquired after the first year of life. The risk of atopy increased significantly with increasing number of childhood infections in the first 2 years of life (p(trend)=0.01).

CONCLUSIONS

These findings do not support the suggestion that childhood exposure to measles, rubella, varicella, or mumps protects against atopy, even if acquired very early in life.

The impact of in vivo Calmette-Guérin Bacillus administration on in vitro IgE secretion in atopic children

To investigate whether a preexisting T helper (T(H)) 2 type immune response could be suppressed by Calmette-Guérin Bacillus (BCG) immunization in atopic children with asthma, we determined interferon (IFN)-gamma, interleukin (IL)-2, IL-4, and IL-5 and total IgE level in the supernatant of peripheral blood mononuclear cells (PBMC) of six atopic and five nonatopic children in response to phytohemagglutinin A (PHA), purified protein derivate (PPD), and Dermatophagoides pteronyssinus II allergen (Der p II) both before and after BCG vaccination. IL-5 level in response to Der p II was significantly higher in the atopic group than in the nonatopic group both before and after BCG vaccination (p = 0.004, p = 0.009, respectively). In the atopic group, IgE levels determined in PPD and Der p II stimulated and unstimulated culture supernatants decreased significantly after BCG vaccination (p = 0.028, p = 0.026, p = 0.046, respectively), whereas in the nonatopic group (p = 0.041) BCG vaccination resulted in a significant decrease in IgE level only in response to Der p II stimulation. We concluded that in vivo BCG administration can downregulate both spontaneous and stimulated in vitro IgE secretion from PBMC of atopic children.

Allergy, parasites, and the hygiene hypothesis

The increase of allergic diseases in the industrialized world has often been explained by a decline in infections during childhood. The immunological explanation has been put into the context of the functional T cell subsets known as T helper 1 (TH1) and T helper 2 (TH2) that display polarized cytokine profiles. It has been argued that bacterial and viral infections during early life direct the maturing immune system toward TH1, which counterbalance proallergic responses of TH2 cells. Thus, a reduction in the overall microbial burden will result in weak TH1 imprinting and unrestrained TH2 responses that allow an increase in allergy. This notion is contradicted by observations that the prevalence of TH1-autoimmune diseases is also increasing and that TH2-skewed parasitic worm (helminth) infections are not associated with allergy. More recently, elevations of anti-inflammatory cytokines, such as interleukin-10, that occur during long-term helminth infections have been shown to be inversely correlated with allergy. The induction of a robust anti-inflammatory regulatory network by persistent immune challenge offers a unifying explanation for the observed inverse association of many infections with allergic disorders.

Lactobacillus casei strain Shirota suppresses serum immunoglobulin E and immunoglobulin G1 responses and systemic anaphylaxis in a food allergy model

BACKGROUND

Our previous study using allergen-sensitized murine splenocyte cultures has shown that Lactobacillus casei strain Shirota (LcS), a lactic acid bacterium widely used as a starter for fermented milk products, suppresses IgE production through promoting a dominant Th1-type response mediated by IL-12 induction.

OBJECTIVE

We tried to evaluate the ability of LcS to suppress both IgE response and allergic reactions in vivo using a food allergy model with ovalbumin-specific T cell receptor transgenic (OVA-TCR-Tg) mice.

METHODS

The ability of heat-killed LcS to induce IL-12 in serum was tested. OVA-TCR-Tg mice were fed a diet containing OVA for 4 weeks and injected with LcS intraperitoneally three times in the first week of this period. Cytokine and antibody secretion by splenocytes, and serum IgE and IgG1 responses were examined. The inhibitory effect of LcS on systemic anaphylaxis induced by intravenous challenge of OVA-fed OVA-TCR-Tg mice with OVA was also tested.

RESULTS

Intraperitoneal injection of LcS induced an IL-12 response in the serum of OVA-TCR-Tg mice. In the food allergy model, LcS administration skewed the pattern of cytokine production by splenocytes toward Th1 dominance, and suppressed IgE and IgG1 secretion by splenocytes. The ability of LcS to modulate cytokine production was blocked by anti-IL-12 antibody treatment. LcS also inhibited serum OVA-specific IgE and IgG1 responses and diminished systemic anaphylaxis.

CONCLUSION

LcS administration suppresses IgE and IgG1 responses and systemic allergic reactions in a food allergy model, suggesting a possible use of this lactic acid bacterium in preventing food allergy.

Increase of allergen-specific immunoglobulin E antibodies from 1973 to 1994 in a Finnish population and a possible relationship to Helicobacter pylori infections

BACKGROUND

The prevalence of atopic diseases--hayfever, asthma and eczema--has increased over the past decades. The increase may be associated with decreased rates of infections such as measles, hepatitis A, tuberculosis, toxoplasmosis, and, as recently suggested, Helicobacter pylori gastritis.

OBJECTIVE

Since the increase of atopy has been mainly based on clinical studies, we wanted to study the prevalence of allergen-specific Immunoglobulin (Ig)E antibodies in two cross-sectional, adult population-based serum samples two decades apart. Since the sera had been tested for H. pylori antibodies, we also had a chance to look for a possible relationship between these two findings.

METHODS

We determined the prevalence rate of allergen-specific serum IgE antibodies against birch and timothy pollen, and cat and dog epithelium allergens by the radioallergosorbent test in a 15-54-years-old Finnish population using 326 sera collected in 1973 and 319 sera collected in 1994 from randomly selected subjects.

RESULTS

From 1973 to 1994 allergen-specific IgE prevalence rates and IgE antibody levels rose. In 1994, the prevalence rate of positive findings in 15-24-year-old population had increased from 11 to 38% (3.5-fold increase, P = 0.0001, OR 5.12, CI 95% 2.32-11.3). In older 10-year age groups similar trends did not reach significance, but the overall change was significant with all three cut-off levels of allergen-specific IgE analysed. The percentage of IgE-positive persons rose mainly in the subgroup with no H. pylori antibodies. In 1994 21% of the H. pylori-negative subjects had IgE antibodies compared with 5% of the H. pylori-positive subjects (in 1973 11% in both subgroups).

CONCLUSIONS

IgE-based evidence for an increase in IgE-mediated allergy was uncovered. The increase occurred mainly in the subgroup with no antibodies to H. pylori, which support the hypothesis that H. pylori could be one of the microbes counteracting atopy.

Endotoxin exposure in allergy and asthma: reconciling a paradox

Well-established evidence links endotoxin exposure, especially in the workplace, to airways disease. Endotoxin can increase disease severity by acting as a natural adjuvant to augment asthma and atopic inflammation. Recent studies suggest that it can even act on its own, causing a distinct endotoxic form of asthma. Other studies, however, contradict the paradigm that endotoxin's influence is solely a negative one. Epidemiologic associations of environmental endotoxin exposure with allergy and asthma prevention are consistent with hygiene hypothesis associations of other microbial exposures or infections with a lower incidence of atopic disease. Currently, microbe-derived products are being developed as potential therapies for allergy and asthma. Thus it is an ideal time to consider endotoxin as a prototype of a natural intervention with microbial components. Nature's ongoing experiment with endotoxin can provide clues for the development of effective and safe microbe-based products for disease treatment and prevention. This article will discuss (1) conventional paradigms in which endotoxin-induced immune modulation by T(H)1-type induction leads to mitigation of T(H)2-type immune development, allergen sensitization, and atopic inflammation; (2) newer concepts of T(H)1-type immune responses that may provide additional asthma-protective effects by preventing airways remodeling; (3) home and environmental features that significantly contribute to endotoxin exposure; (4) different aspects of asthma mediated by endotoxin exposure; and (5) how to understand endotoxin's paradoxical nature of serving as both friend and foe.

Common respiratory infections early in life may reduce the risk of atopic dermatitis

Infections that occur early in life may protect against atopic disease later in life. To investigate the relationship between common acute respiratory infections and atopic dermatitis in early childhood, we closely observed a cohort of 329 children from the ages of 2 to 24 months. We assessed the effect of proven viral infections and acute otitis media on the occurrence of atopic dermatitis. If the child had his or her first respiratory infection before the age of 6 months, the child's remaining risk of developing atopic dermatitis was reduced by 49% (95% confidence interval, -24% to 79%). The individual risk of developing atopic dermatitis was similarly reduced after infection experienced at >/=6 months of age, but the remaining risk was low, because most cases of atopic dermatitis had manifested by this time. Our results are consistent with the hypothesis that early infections may reduce the risk of atopic disease.

Malaria infection does not appear to modify the risk of bronchiolitis early in life

BACKGROUND

The observation of an increased prevalence of allergic disorders coinciding with a decreasing frequency of infectious diseases in early childhood has led to the speculation that infections may prevent allergic sensitization. Information on the role of parasites in this context is limited. Bronchiolitis in infancy has been linked with asthmatic symptoms later in childhood, although the underlying cause of this association is unknown.

METHODS

To test the hypothesis that early parasitic infections in infancy might prevent the development of allergic manifestations later in life, the effect of malaria infections during the first year of life on the risk of bronchiolitis was studied in 675 Tanzanian children at 18 months of age. The study was conducted as part of an intervention trial of malaria chemoprophylaxis and/or iron supplementation for the prevention of malaria and anemia in infants.

RESULTS

The incidence of bronchiolitis up to 18 months of age in the 675 children was 0.58 episode per child per year. The risk factors analysis was based on 470 children with complete data. There was no difference in the incidence of bronchiolitis between those who had received malaria chemoprophylaxis during the first year of life and those who had not. However, the proportion of children who had bronchiolitis was lower among those who had had malaria episodes than among those who had not (48% vs. 55%, P = 0.05).

CONCLUSIONS

This study does not support the hypothesis that reduced exposure to parasites may modulate the development of bronchiolitis early in life.

Does a higher number of siblings protect against the development of allergy and asthma? A review

STUDY OBJECTIVE

To review the "protective" effects of having a higher number of siblings for the risk of atopic eczema, asthma wheezing, hay fever, and allergic sensitisation.

METHOD

Review of the literature (Medline since 1965 and references).

MAIN RESULTS

53 different studies were identified. For eczema, 9 of 11 studies reported an inverse relation with number of siblings; for asthma and wheezing, 21 of 31 reported the inverse association; for hay fever, all 17 studies showed the effect; for allergic sensitisation or immunoglobulin E reactivity 14 of 16 studies supported the "protective" effect of a higher number of siblings. The studies emphasise a "theory" that is based exclusively on epidemiological associations.

CONCLUSIONS

Research has not yet answered the question of which causal factors explain the sibling effect. Causal factors must meet two criteria; they must vary with sibship size and they must protect against atopic manifestations. The prevailing "hygiene hypothesis" failed to explain the findings adequately. Alternative explanations include in utero programming or endocrine explanatory models. The epidemiology research into siblings and atopic disorders has entered an intellectually challenging phase. Possessing sufficient knowledge about the causal factors might prevent at least 30% of all cases of asthma, eczema, and hay fever.

Application of heat killed Mycobacterium bovis-BCG into the lung inhibits the development of allergen-induced Th2 responses

We have previously reported that an infection of the lung with BCG-inhibited ovalbumin (OVA)-induced airway eosinophilia. In the current study, we investigated if the intranasal application of heat killed (HK)-BCG or purified protein derivative (PPD) from Mycobacterium tuberculosis had the same effect. For this purpose we treated mice intranasally with either live BCG, HK-BCG or PPD and analyzed if the mice developed airway eosinophilia after immunization and intranasal challenge with OVA. Our results clearly showed that an intranasal vaccination with live and HK-BCG but not PPD, given 4 or 8 weeks prior to allergen airway challenge, resulted in a strong suppression of airway eosinophilia. The inhibition of airway eosinophilia correlated with reduced levels of IL-5 production by T cells from the lymph node of the lungs and a strong reduction in Th2 cell numbers present in the airways of OVA-challenged mice. Furthermore, HK-BCG-induced suppression of airway eosinophilia was strongly reduced in IFN-gamma deficient mice. HK-BCG in contrast to live BCG may also be a promising candidate for a prospective asthma vaccine in humans since negative side effects due to mycobacterial infection can be ruled out.

What is the evidence for a causal link between hygiene and infections?

Even in an era in which access to personal "cleanliness" and a public health infrastructure are readily available in developed countries, illnesses associated with day care centres and homes continue to be a problem. The inhabitants of less developed countries, on the other hand, must contend with an inadequate public health infrastructure, lack of education programmes, and economic limitations in obtaining hygiene products. Therefore, less developed countries carry a greater burden of morbidity and mortality from infectious illnesses. The objective of this review is to examine and assess the epidemiological evidence for a causal relation between hygiene practices and infections. The Medline database was searched from January 1980 to June 2001 and studies were included if the outcome(s) was infection or symptoms of infection, and if the independent variable(s) was one or more hygiene measures. The strength of the association as measured by the relative reduction in risk of illness was appreciable and generally greater than 20%. Despite methodological strengths and limitations of the studies assessed, the weight of evidence collectively suggests that personal and environmental hygiene reduces the spread of infection. The results from this review demonstrate that there is a continued, measurable, positive effect of personal and community hygiene on infections.

Relationship of viral infections to wheezing illnesses and asthma

Viral infections can influence both the development and the severity of asthma. In early life, viral infections can either increase or, remarkably, decrease the risk of subsequent asthma. In children and adults with existing asthma, viral respiratory infections frequently cause acute airway obstruction and wheezing. This article discusses the influence of viral infections on mechanisms of virus-induced airway inflammation in relationship to the development, persistence and severity of asthma.

Early exposure to infections and antibiotics and the incidence of allergic disease: a birth cohort study with the West Midlands General Practice Research Database

BACKGROUND

It has been suggested that the rise in prevalence of allergic disease in westernized countries is due in part to a decrease in exposure to infections and an increase in the use of antibiotics early in life.

OBJECTIVE

The purpose of this investigation was to quantify the relationships between (1) exposure to personal infections, infections in siblings, and use of antibiotics in early life and (2) the incidence of allergic disease.

METHODS

Using the West Midlands section of the UK General Practice Research Database, we established a historical birth cohort of children (N = 29,238). For each child, we identified all personal infections and infections in siblings and determined the use of antibiotics in early life; we also noted incident diagnoses of asthma, eczema, and hay fever. The data were analyzed through use of Cox regression.

RESULTS

There was no clear protective effect of exposure to either personal infections or infections in siblings with respect to the incidence of allergic disease. Antibiotic exposure was associated with an increased risk of developing allergic disease in a dose-related manner: having 4 or more courses of antibiotics in the first year of life was associated with an increased incidence of asthma (hazard ratio [HR], 3.13; 95% CI, 2.75-3.57), eczema (HR, 1.48; 95% CI, 1.31-1.68), and hay fever (HR, 2.12; 95% CI, 1.68-2.66). However, adjusting for consulting behavior reduced these effects (adjusted HR [95% CI]: asthma, 1.99 [1.72-2.31]; eczema, 1.01 [0.88-1.17]; hay fever, 1.14 [0.88-1.47]).

CONCLUSIONS

We found no evidence that exposure to infections reduced the incidence of allergic disease, and infections did not explain the previous findings of a strong birth order effect in this cohort. The use of antibiotics might be associated with early diagnoses of allergic disease.

Viruses in asthma

Current evidence suggests that the overall load of infectious agents, including respiratory viruses, encountered early in life is an important factor influencing maturation of the immune system from a type 2 bias at birth towards predominantly type 1 responses, thus avoiding atopic diseases. The 'hygiene hypothesis' proposes that the relatively sterile environment present in industrialised Western countries has contributed to the recent epidemic of asthma and atopy. Whether specific infections are of greater or lesser protective value is an important question if strategies are to be derived to mimic the beneficial effects of childhood infection whilst avoiding morbidity and potential mortality of the natural pathogens. Infection by respiratory viruses is a major trigger of wheezing in infants and of exacerbations of asthma in older children. Viruses are detected in up to 85% of such episodes. Rhinovirus is common in all age groups; respiratory syncytial virus (RSV) is most important in infants and young children. Knowledge of the immunopathogenetic mechanisms of virus infection in the asthmatic airway will lead to the development of new treatments for virus-induced asthma.

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.

Wheezing lower respiratory disease and vaccination of full-term infants

PURPOSE

There have been speculations that increases in vaccinations have caused recent increases in wheezing lower respiratory disease during infancy. We assess possible associations between vaccines and incidence of wheezing in full-term infants.

METHODS

We conducted a matched case-control study of full-term infants born into the Kaiser Permanente Northwest health plan during 1991-1994 and continuously enrolled for at least 12 months (n = 1366 case-control pairs). Potential cases of wheeze were ascertained from medical care databases and verified by chart review. Vaccinations, demographic factors, and wheeze risk factors were abstracted from charts. Adjusted relative risks of first onset of wheeze during post-vaccination exposure windows were estimated by conditional logistic regression. We also conducted case-series analyses of wheeze onsets.

RESULTS

We found no evidence that risk of wheeze during infancy is associated with recency of vaccination with whole-cell pertussis (DTP), hepatitis b (HBV), Haemophilus influenzae type b (HIB), oral polio (OPV), or measles, mumps and rubella (MMR) vaccines. We also found no evidence that risk of first wheeze is associated with exposure to HBV or MMR.

CONCLUSIONS

Recent increases in wheezing during infancy do not appear to be related to increases in vaccinations of full-term infants.

Why are allergies increasing?

The incidence of atopic allergy is increasing in certain 'Western' countries but this remains unexplained. Various hypotheses with differing amounts of evidence and/or relevance have been assessed, including increased awareness of the diseases, improved diagnostics, genetic susceptibility, psycho-social influences, allergen exposure, decreased immune-system stimulation, underlying disease, anti-allergic therapy and pollution.

Do early childhood immunizations influence the development of atopy and do they cause allergic reactions?

Concerns about allergic side-effects of vaccines and about a possible promotion of allergic diseases contribute to incomplete vaccination rates in childhood. This article reviews the current understanding of these issues. There is evidence that pertussis and diphtheria/tetanus antigens elicit immunoglobulin E (IgE) antibody formation as part of the immune response. In murine models, pertussis toxin is an effective adjuvant for IgE formation against simultaneously administered antigens. In children, however, sensitization to unrelated antigens or development of allergic diseases do not seem to be augmented. In contrast, bacille Calmette-Guérin (BCG) and measles vaccination have been proposed as suppressors of allergy because of their T helper 1 (Th1)-fostering properties. In the murine system, BCG inhibits allergic sensitization and airway hyper-reactivity. Some epidemiological studies in humans suggest an inhibitory effect of tuberculosis on allergy. BCG vaccination in children, however, has no or merely a marginal suppressive effect on atopy. Other vaccine components such as egg proteins, gelatin, and antibiotics are a potential hazard to children with severe clinical reactions to these allergens. These rare children should be vaccinated under special precautions. In conclusion, vaccination programs do not explain the increasing prevalence of allergic diseases, but individual children may uncommonly develop an allergic reaction to a vaccine. The risks of not vaccinating children, however, far outweigh the risk for allergy. Therefore, childhood vaccination remains an essential part of child health programs and should not be withheld, even from children predisposed for allergy.

Characterizing the composition of intestinal microflora as a prospective treatment target in infant allergic disease

We assessed the fecal microflora of 10 healthy infants and 27 infants with atopic eczema during breast-feeding and after weaning. The atopic infants had less frequently Gram-positive species among the most predominant aerobes and smaller total cell counts. Further differences were associated with more extensive manifestations, seen as higher bacteroides and lower bifidobacteria counts. Weaning resulted in decreased bacteroides counts in atopic and total cell counts in healthy infants and diminished predominance by bifidobacteria in both. In conclusion, the most prominent question raised by these data is whether Gram-positive bacteria may have distinctive importance in protection against atopic sensitization. Further studies aiming to answer this question are warranted.

Atopic disorders: a vaccine around the corner?

The incidence and severity of atopic disorders, in particular asthma, is steadily increasing at an alarming rate. Furthermore, no primary prevention measure exists to date. However, recent results obtained from numerous animal studies suggest that primary prevention in humans might be possible in the near future. The most promising approaches include the induction of systemic or local allergen-dependent or -independent T helper 1 (Th1) immune responses, through the use of killed bacteria (or components derived from them), CpG oligodeoxynucleotides or plasmid DNA, and the induction of allergen-specific T-cell tolerance. Here, we review the data showing that animals can be protected from developing allergic Th2 responses by vaccination. Possible future use in humans and potential side-effects of the described vaccination strategies are discussed also.

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.

Atopy, intestinal helminth infection and total serum IgE in rural and urban adult Gambian communities

BACKGROUND

The rarity of atopy in traditional societies has been attributed to high parasite-driven blocking IgE concentrations. Information is lacking on the relationship between atopy, IgE and intestinal helminth infection in African populations.

OBJECTIVE

To determine the prevalence of atopy and intestinal helminth infection and to relate these to wheeze history and serum total IgE in a community sample of adults from an urban (Banjul) and a rural (Farafenni) area of the Gambia.

METHODS

Six hundred and ninety-three adults were interviewed about respiratory symptoms using a modified version of the IUTLD questionnaire, and had skin prick testing using four allergens. Stools were examined after formol-ether concentration. Total serum IgE concentration was measured in a subset of participants.

RESULTS

The prevalence of atopy (mean weal diameter > or = 3 mm) in the urban and rural area was 35.3% and 22.5% (P = 0.05); D. pteronyssinus and Mold mix being the common sensitizing allergens. Prevalence of wheeze in the previous 12 months was 4.4% and 3.5% for the urban and rural areas, respectively. Wheezing was not significantly associated with atopy. Seventeen per cent of urban and 8.2% of rural subjects had helminths detected in stools. There was an inverse association between atopy and intestinal helminth infection; 7% of atopic subjects had helminths, compared to 13% of non-atopic subjects (unadjusted odds ratio 0.51, 95%CI 0.24-1.1, P = 0.09; adjusted odds ratio 0.37, 95%CI 0.15-0.92, P = 0.03). Non-atopics had total serum IgE concentrations about 2.5 times the upper limit of the reference range in non-atopic Western populations. Geometric mean total serum IgE concentration was significantly higher among atopic subjects (570 IU/mL, IQR 91-833) than non-atopic subjects (259 IU/mL, IQR 274-1303) (P < 0.001). IgE concentration was not associated with the presence of helminth infection.

CONCLUSION

Further studies are needed to clarify why asthma is still relatively uncommon in spite of the prevalence of atopy in Gambian adults. Our data are also compatible with the idea that atopy might protect against helminth infection.

Do hepatitis B virus carriers develop atopic diseases?

The prevalence of allergic disorders, such as asthma, hay fever, and atopic dermatitis, has increased dramatically over the past few decades. Although the important inherited component in these diseases is well established, the role of environmental factors in relation to allergic disorders has become increasingly topical in the last decade. Immunologic data show that different infections can either promote atopy (as in respiratory syncytial virus infections) or inhibit it (as in measles, hepatitis A, and tuberculosis). Although there are 400 million hepatitis B virus (HBV) carriers around the world, and asymptomatic HBV carriers with a high level of virus replication are characterized by Th2-type immune reactions, the relationship between HBV carriers and atopic disorders has not been studied.

The germless theory of allergic disease: revisiting the hygiene hypothesis

Rising rates of allergic disease accompany the healthier benefits of a contemporary westernized lifestyle, such as low infant mortality. It is likely that these twinned phenomena are causally related. The hygiene hypothesis states that allergy and increased longevity are both consequences of reducing infectious stressors during early childhood for millennia. Mechanistic explanations for the hygiene hypothesis have typically invoked the T-helper-type 1/2 (T(H)1/T(H)2) model. Here, we discuss why we favour a broader 'counter-regulatory' model--one that might also explain the increasing incidence of autoimmune disease in westernized countries.

Ontogeny of Th1 memory responses against a Brucella abortus conjugate

Protective immune responses to intracellular pathogens such as Brucella abortus are characteristically Th1-like. Recently we demonstrated that heat-killed B. abortus (HKBa), a strong Th1 stimulus, conjugated to ovalbumin (HKBA-OVA), but not B. abortus alone, can alter the antigen-specific cytokine profile from Th2- to Th1-like. In this report we study the ability of a single injection of B. abortus to switch a Th2 to a Th1 response in immature mice. One-day- and 1-week-old mice were given a single injection of B. abortus in the absence or presence of OVA, and at maturity mice were challenged with an allergenic preparation, OVA with alum (OVA-A). B. abortus given without OVA did not diminish the subsequent Th2 response in either age group. In contrast, mice receiving a single injection of B. abortus-OVA at the age of 1 week, but not those injected at the age of 1 day, had reversal of the ratio of OVA-specific Th1 to Th2 cells and decreased immunoglobulin E levels after allergen challenge as adults. Within 6 h both 1-day- and 1-week-old mice expressed interleukin-12 p40 mRNA following either B. abortus or B. abortus-OVA administration. However, only the 1-week-old mice exhibited increased expression of gamma interferon (IFN-gamma) mRNA. The absence of the early IFN-gamma response in 1-day-old mice may explain their inability to generate a Th1 memory response. These results suggest that at early stages of immune development, responses to intracellular bacteria may be Th2- rather than Th1-like. Furthermore, they suggest that the first encounter with antigen evokes either a Th1- or a Th2-like response which becomes imprinted, so that subsequent memory responses conform to the original Th bias. This has implications for protection against infectious agents and development of allergic responses.

Allergic rhinoconjunctivitis, eczema, and sensitization in two areas with differing climates

In this 5-year follow-up study we compared the prevalence of allergic rhinoconjunctivitis, eczema, and sensitization, in relation to several background factors, in two Swedish regions (Göteborg and Kiruna). In Göteborg, a city on the southwest coast, the climate is mild and humid. Kiruna is a town north of the Arctic Circle. Questionnaire replies and results of interviews were collected from all 412 7-8-year-old children of a population-based sample (203 in Göteborg and 209 in Kiruna); in addition, 192 children from Göteborg and 205 from Kiruna were skin-prick tested for sensitization to common aero-allergens. After 5 years, at 12-13 years of age, almost all of the initial study cohort were re-investigated. At follow-up the prevalence of allergic rhinoconjunctivitis was 17%, eczema 23%, and sensitization 32%. Allergic rhinoconjunctivitis and eczema were as common in Göteborg as in Kiruna, whereas sensitization was far more common in Kiruna. Children born during the pollen season had allergic rhinoconjunctivitis less often -- and were sensitized to pollen and animal protein less often -- than those born during the rest of the year. Sensitization to birch pollen, cat protein, and horse protein was less common in children living in Göteborg, the region with the highest frequency of cat ownership and horseback riding, and with the longest birch-pollen season. The girls were more commonly horseback riders but the boys were more often sensitized to horses. The results reinforce our previous findings: indoor climate may affect the development of sensitization and allergic diseases, to some extent independently; and if exposure to antigen is unavoidable, high doses might be better than low doses.

Immunization and symptoms of atopic disease in children: results from the International Study of Asthma and Allergies in Childhood

OBJECTIVES

This study tested the hypothesis that immunization is related to the prevalence of atopic disease in childhood.

METHODS

We used data from the International Study of Asthma and Allergies in Childhood to perform an ecologic analysis of national and local immunization rates for tuberculosis, diphtheria and tetanus toxoids and pertussis (DTP), and measles and prevalence of atopic disease symptoms (asthma, allergic rhinoconjunctivitis, and atopic eczema).

RESULTS

In 13- to 14-year-old children, there were significant negative associations with local birth-year immunization rates for DTP and measles but none with rates for tuberculosis. No associations were found in 6- to 7-year-old children. No associations with national immunization rates were found.

CONCLUSIONS

International variations in childhood atopic diseases are unlikely to be explained by variations in immunization.

Pathophysiological mechanisms of asthma. Application of cell and molecular biology techniques

Asthma is a common increasing and relapsing disease that is associated with genetic and environmental factors such as respiratory viruses and allergens. It causes significant morbidity and mortality. The changes occurring in the airways consist of a chronic eosinophilic and lymphocytic inflammation, together with epithelial and structural remodeling and proliferation, and altered matrix proteins, which underlie airway wall narrowing and bronchial hyperresponsiveness (BHR). Several inflammatory mediators released from inflammatory cells such as histamine and cysteinyl-leukotrienes induce bronchoconstriction, mucus production, plasma exudation, and BHR. Increased expression of T-helper 2 (Th2)-derived cytokines such as interleukin-4 and 5 (IL-4, 5) have been observed in the airway mucosa, and these may cause IgE production and terminal differentiation of eosinophils. Chemoattractant cytokines (chemokines) such as eotaxin may be responsible for the chemoattraction of eosinophils to the airways. The initiating events are unclear but may be genetically determined and may be linked to the development of a Th2-skewed allergen-specific immunological memory. The use of molecular biology techniques on tissues obtained from asthmatics is increasing our understanding of the pathophysiology of asthma. With the application of functional genomics and the ability to transfer or delete genes, important pathways underlying the cause if asthma will be unraveled. The important outcome of this is that new preventive and curative treatments may ensue.

A population genetics study of single nucleotide polymorphisms in the interleukin 4 receptor alpha (IL4RA) gene

Interleukin 4 (IL4) plays a critical role in T helper 2 (Th2) immune responses. Here we report a population genetics study of variation in the gene encoding the alpha-chain of the IL4 receptor (IL4RA) in three ethnic groups: African Americans, European Americans and East Asians. A 2941-bp region spanning exon 12 of IL4RA gene was sequenced in 12 individuals from each group. A total of 24 single nucleotide polymorphisms (SNPs) were identified in the combined sample. The genetic variation of the coding region of exon 12 is two to three times higher than in other reported genes. A significant departure from the expectation of evolutionary neutrality was observed, suggesting that natural selection may have influenced the evolution of this gene. We propose a model in which past selection by pathogens contributed to the increasing prevalence of atopic disorders in Western societies.

Probiotics in primary prevention of atopic disease: a randomised placebo-controlled trial

BACKGROUND

Reversal of the progressive increase in frequency of atopic disease would be an important breakthrough for health care and wellbeing in western societies. In the hygiene hypothesis this increase is attributed to reduced microbial exposure in early life. Probiotics are cultures of potentially beneficial bacteria of the healthy gut microflora. We assessed the effect on atopic disease of Lactobacillus GG (which is safe at an early age and effective in treatment of allergic inflammation and food allergy).

METHODS

In a double-blind, randomised placebo-controlled trial we gave Lactobacillus GG prenatally to mothers who had at least one first-degree relative (or partner) with atopic eczema, allergic rhinitis, or asthma, and postnatally for 6 months to their infants. Chronic recurring atopic eczema, which is the main sign of atopic disease in the first years of life, was the primary endpoint.

FINDINGS

Atopic eczema was diagnosed in 46 of 132 (35%) children aged 2 years. Asthma was diagnosed in six of these children and allergic rhinitis in one. The frequency of atopic eczema in the probiotic group was half that of the placebo group (15/64 [23%] vs 31/68 [46%]; relative risk 0.51 [95% CI 0.32-0.84]). The number needed to treat was 4.5 (95% CI 2.6-15.6).

INTERPRETATIONS

Lactobacillus GG was effective in prevention of early atopic disease in children at high risk. Thus, gut microflora might be a hitherto unexplored source of natural immunomodulators and probiotics, for prevention of atopic disease.

The coming-of-age of the hygiene hypothesis

The hygiene hypothesis, as originally proposed, postulated an inverse relation between the incidence of infectious diseases in early life and the subsequent development of allergies and asthma. New evidence from epidemiological, biological and genetic studies has significantly enlarged the scope of the hypothesis. It now appears probable that environmental 'danger' signals regulate the pattern of immune responses in early life. Microbial burden in general, and not any single acute infectious illness, is the main source of these signals. The latter interact with a sensitive and complex receptor system, and genetic variations in this receptor system may be an important determinant of inherited susceptibility to asthma and allergies.

Environmental associations with eczema in early life

BACKGROUND

Although atopic eczema (AE) is a common disease, little is known about its causes.

OBJECTIVES

To investigate the role of dietary and environmental factors associated with the development of AE by the age of 2 years.

METHODS

A cohort of children was recruited before birth from a consecutive series of newly pregnant mothers presenting for antenatal care at three general practices in Ashford, Kent, U.K. Data up to the age of 2 years were available for 624 (97%) of the original cohort. AE was defined using components of the U.K. diagnostic criteria for AE, maternal report of doctor-diagnosed eczema and maternally reported eczema. Exposures of interest were family history of allergic disease, dietary and breastfeeding patterns, family size and exposure to indoor domestic allergens.

RESULTS

The cumulative prevalence of AE using the U.K. diagnostic criteria was 14% (95% confidence interval, CI 11-17%). The prevalence of maternally reported doctor-diagnosed eczema was much higher (31%, 95% CI 27-35%) and almost half (45%) the mothers reported that their child had ever had eczema (95% CI 41-49%). The relationship between parental atopy, parental history of allergic disease and the child's eczema was consistently stronger for the mothers than the fathers. There was a marked increase in the prevalence of eczema with increasing maternal education and in less crowded homes, associations that remained significant after controlling for other factors.

CONCLUSIONS

The associations with environmental factors are consistent with the hypothesis that more crowded houses, increased family size and birth order, which may possibly increase early exposure to infections, may offer protection from subsequent development of eczema.

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.

Allergy markers in respiratory epidemiology

Assessing allergy by measurement of serum immunoglobulin (Ig) E antibodies is fast and safe to perform. Serum antibodies can preferably be assessed in patients with dermatitis and in those who regularly use antihistamines and other pharmacological agents that reduce skin sensitivity. Skin tests represent the easiest tool to obtain quick and reliable information for the diagnosis of respiratory allergic diseases. It is the technique more widely used, specific and reasonably sensitive for most applications as a marker of atopy. Measurement of serum IgE antibodies and skin-prick testing may give complimentary information and can be applied in clinical and epidemiological settings. Peripheral blood eosinophilia is less used, but is important in clinical practice to demonstrate the allergic aetiology of disease, to monitor its clinical course and to address the choice of therapy. In epidemiology, hypereosinophilia seems to reflect an inflammatory reaction in the airways, which may be linked to obstructive airflow limitation.

Infection of mice with the helminth Strongyloides stercoralis suppresses pulmonary allergic responses to ovalbumin

Asthma and helminth infections induce similar immune responses characterized by the presence of peripheral blood eosinophilia and elevated serum IgE levels. Epidemiological surveys have reported either increases or decreases in the development of atopic diseases and asthma based on the prevalence of helminth infections in the population. The aim of this study was to determine if a pre-existing helminth infection would increase or decrease subsequent allergic responses to an unrelated allergen in the lungs. BALB/cByJ mice were infected with the nematode parasite Strongyloides stercoralis prior to ovalbumin (OVA) immunization and intratracheal challenge. Bronchoalveolar lavage (BAL) and fluid (BALF) were collected 3 days post-challenge and cellular and humoral immune responses were measured. Intracellular cytokine staining revealed increased IL-4 and IL-5 producing cells in BAL from mice infected with S. stercoralis before OVA sensitization. Increased IL-5 protein levels and decreased IFN-gamma protein levels were also observed in the BALF. There was, however, no increase in airway eosinophil accumulation in mice infectd with parasites before sensitization with OVA as compared to mice exposed to OVA alone. Furthermore, eotaxin levels in the lungs induced by OVA was suppressed in mice infected with the parasite before OVA sensitization. The development of OVA specific IgE responses in BALF was also impaired in mice infected with the parasite before sensitization with OVA. These results suggest that a pre-existing helminth infection may potentiate a systemic Type 2-type response yet simultaneously suppress in the lungs allergen-specific IgE responses and eotaxin levels in response to subsequent exposure to allergens.

Interference between host resistance to Listeria monocytogenes infection and ovalbumin-induced allergic responses in mice

Listeria monocytogenes promotes the induction of the T-helper 1 (Th1) cell response, while ovalbumin (OVA) induces a Th2 cell response and allergic reactions, such as airway hyperreactivity and immunoglobulin E (IgE) production. When mice were immunized with OVA on day 7 after L. monocytogenes infection, eosinophilia in bronchoalveolar lavage and the production of total IgE, OVA-specific IgE, interleukin-4 (IL-4), and IL-5 in the circulation were markedly suppressed. Cytokine responses, including IL-4, IL-5, IL-10, IL-13, and gamma interferon, to OVA were decreased in the spleen cell cultures obtained from OVA-immunized mice that had been infected with L. monocytogenes. Conversely, when OVA-immunized mice were infected with L. monocytogenes, conversion from the nonlethal infection to the lethal infection occurred. Host resistance to L. monocytogenes infection in OVA-immunized mice was enhanced by the administration of anti-IL-10 monoclonal antibody. The present study indicates that striking interference is observed between Th1-inducing L. monocytogenes infection and Th2-driven OVA-induced airway hyperreactivity.

Early childhood infectious diseases and the development of asthma up to school age: a birth cohort study

OBJECTIVE

To investigate the association between early childhood infections and subsequent development of asthma.

DESIGN

Longitudinal birth cohort study.

SETTING

Five children's hospitals in five German cities.

PARTICIPANTS

1314 children born in 1990 followed from birth to the age of 7 years.

MAIN OUTCOME MEASURES

Asthma and asthmatic symptoms assessed longitudinally by parental questionnaires; atopic sensitisation assessed longitudinally by determination of IgE concentrations to various allergens; bronchial hyperreactivity assessed by bronchial histamine challenge at age 7 years.

RESULTS

Compared with children with /=2 episodes were less likely to have a doctor's diagnosis of asthma at 7 years old (odds ratio 0.52 (95% confidence interval 0.29 to 0.92)) or to have wheeze at 7 years old (0.60 (0.38 to 0.94)), and were less likely to be atopic before the age of 5 years. Similarly, having >/=1 viral infection of the herpes type in the first 3 years of life was inversely associated with asthma at age 7 (odds ratio 0.48 (0.26 to 0.89)). Repeated lower respiratory tract infections in the first 3 years of life showed a positive association with wheeze up to the age of 7 years (odds ratio 3.37 (1.92 to 5.92) for >/=4 infections v

CONCLUSION

Repeated viral infections other than lower respiratory tract infections early in life may reduce the risk of developing asthma up to school age.

Collapse

Key Words Collapse

MESH Headings

• Antibodies/blood
• Asthma/etiology
• Asthma/immunology
• Bronchial Hyperreactivity
• Bronchial Provocation Tests
• Chi-Square Distribution
• Child
• Child, Preschool
• Common Cold/complications
• Herpesviridae Infections/complications
• Humans
• Immunoglobulin E/blood
• Infant
• Infant, Newborn
• Likelihood Functions
• Logistic Models
• Longitudinal Studies
• Odds Ratio
• Prevalence
• Recurrence
• Respiratory Sounds
• Respiratory Tract Infections/complications

Collapse

Grants Collapse

Affiliation(s)

S Illi Department of Pulmonology and Allergology, University Children's Hospital, Lindwurmstrasse 4, 80337 Munich, Germany.
E von Mutius
S Lau
R Bergmann
B Niggemann
C Sommerfeld
U Wahn

Collapse