Evidence for the genetic control of immunoglobulin E reactivity to the allergens of Alternaria alternata

Exploring the origins of asthma: Lessons from twin studies

This thesis explores the contribution of twin studies, particularly those studies originating from the Danish Twin Registry, to the understanding of the aetiology of asthma. First, it is explored how twin studies have established the contribution of genetic and environmental factors to the variation in the susceptibility to asthma, and to the variation in several aspects of the clinical expression of the disease such as its age at onset, its symptomatology, its intermediate phenotypes, and its relationship with other atopic diseases. Next, it is explored how twin studies have corroborated theories explaining asthma's recent increase in prevalence, and last, how these fit with the explanations of the epidemiological trends in other common chronic diseases of modernity.

Mold allergen sensitization in adult asthma according to integrin β3 polymorphisms and Toll-like receptor 2/+596 genotype

BACKGROUND

Integrin β3 (ITGB3) and Toll-like receptor 2 (TLR2) are candidate genes for asthma and sensitization to mold allergens. Integrin β3 forms a complex with TLR2, and this biological interaction is required for the response of monocytes to TLR2 agonists such as fungal glucan.

OBJECTIVE

To study whether genetic interaction between single nucleotide polymorphisms (SNPs) in genes encoding the TLR2-ITGB3 complex enhances susceptibility to mold sensitization.

METHODS

Association analysis was conducted in 1243 adults (524 with asthma) who participated in the follow-up of the Epidemiological Study on the Genetics and Environment of Asthma. Allergic sensitization to mold allergens was determined by skin prick testing. Association of mold sensitization with 14 ITGB3 SNPs was tested under an additive genetic model. Interaction between ITGB3 SNPs and TLR2/+596, which was previously shown to be associated with asthma, was studied.

RESULTS

A positive skin prick test to mold was found in 115 subjects with asthma (22.0%) and in 61 subjects without asthma (8.5%). The ITGB3 rs2056131 A allele was associated with mold sensitization in subjects with asthma with an odds ratio (95% CI) of 0.60 (0.43-0.83; P = .001). Ten other ITGB3 SNPs were significantly associated with mold sensitization in TLR2/+596TT subjects with asthma (P = .03-.002), whereas much weaker associations were found in carriers of the TLR2/+596 C allele (P = .60-.04). Interaction between TLR2/+596 and these ITGB3 SNPs was statistically significant (P interaction = .05-.001).

CONCLUSION

TLR2/+596 genotype may influence the association between ITGB3 SNPs and mold sensitization in adults with asthma.

Alternaria alternata TCTP, a novel cross-reactive ascomycete allergen

Defining more comprehensively the allergen repertoire of the ascomycete Alternaria alternata is undoubtedly of immense medical significance since this mold represents one of the most important, worldwide occurring fungal species responsible for IgE-mediated hypersensitivity reactions ranging from rhinitis and ocular symptoms to severe involvement of the lower respiratory tract including asthma with its life-threatening complications. Performing a hybridization screening of an excised A. alternata cDNA library with a radioactively labeled Cladosporium herbarum TCTP probe, we were able to identify, clone and purify the respective A. alternata homologue of TCTP which again represents a multifunctional protein that has been evolutionarily conserved from unicellular eukaryotes like yeasts to humans and appears, summarizing current literature, to be involved in housekeeping processes such as cell growth as well as cell-cycle progression, the protection of cells against various stress conditions including for instance apoptosis, and in higher organisms even in the allergic response. In this context, our present study characterizes recombinant A. alternata TCTP as a novel minor allergen candidate that displays a prevalence of IgE reactivity of approximately 4% and interestingly shares common, cross-reactive IgE epitopes with its C. herbarum and human counterparts as determined via Western blotting and in vitro inhibition approaches.

Specific allergic sensitization in parents and their 18-year-old offspring in the Suburban Detroit Childhood Allergy Study

BACKGROUND

Allergic sensitization is increased among offspring of sensitized parents.

OBJECTIVE

We sought to evaluate whether 18-year-old offspring are likely to have the same allergic sensitizations as their parents.

METHODS

Eighteen-year-old participants in an unselected birth cohort and their parents were tested for total and increased (>0.35 kU/L) levels of allergen-specific IgE to 6 allergens: Dermatophagoides farinae, dog, cat, grass, ragweed, and Alternaria alternata.

RESULTS

In 316 parent-teen triads parental sensitization to any of 6 allergens was associated with teen sensitization to any of those same allergens. An increased risk of matched sensitization (ie, a teen has an increased risk of being sensitized to the same specific allergen as their parent) was found after adjusting for the spouse's sensitivities and adjusting for other allergens (ie, the parent had an allergic sensitization but not to the particular allergen under analysis). Risk of maternal matched sensitization with their teen to cat (adjusted odds ratio [aOR], 2.1; 95% CI, 1.0-4.5), grass (aOR, 2.5; 95% CI, 1.2-5.2), and A alternata (aOR, 2.4; 95% CI, 1.1-5.5) was increased when compared with that seen in teens without parental allergen-specific sensitization. Similarly, a higher than expected risk of paternal matched sensitization with their teen to dog (aOR, 2.7; 95% CI, 1.3-5.9), D farinae (aOR, 2.7; 95% CI, 1.4-5.1), and grass (aOR, 2.7; 95% CI, 1.5-5.9) was observed.

CONCLUSION

Parental allergen-specific IgE increases the likelihood of sensitization to the same allergen in young adult offspring.

Total and specific IgE associations between New York City Head Start children and their parents

BACKGROUND

Allergy and asthma risk share strong inherited components; however, the relative importance of maternal and paternal atopy in predicting child atopy remain unclear.

OBJECTIVE

We sought to identify relationships between parents' and children's total and specific IgE levels within family units as predictors of allergic risk in children.

METHODS

Total and allergen-specific IgE (to dust mite, cockroach, mouse, and cat) were determined by means of ImmunoCap (Phadia, Inc, Portage, Mich) in a sample of families participating in New York City Head Start programs. Regression models were developed to determine the associations of parents' and children's total IgE levels and sensitization patterns.

RESULTS

Blood specimens were collected from 161 family triads of mother, father, and child (83 boys and 78 girls). At a mean age of 4 years, boys had significantly higher total IgE levels than girls. Boys' total IgE levels were highly correlated with both mothers' (P < .002) and fathers' (P = .002) total IgE levels; girls' total IgE levels were not. Unlike total IgE levels, specific IgE levels among both boys and girls were associated with their mothers' specific IgE levels. Dust mite sensitization among mothers was predictive of children's sensitization to each of the 4 aeroallergens.

CONCLUSION

The strong associations between parents' and children's IgE levels suggest that assessment of parents' total and locally relevant allergen-specific IgE levels might have value in predicting atopy in children of preschool age.

Halogen immunoassay, a new method for the detection of sensitization to fungal allergens; comparisons with conventional techniques

BACKGROUND

Accurate diagnosis of allergy to specific fungal species is confounded by the variability in allergens occurring with different diagnostic systems. We compared the halogen immunoassay (HIA), which uses allergens expressed by freshly germinated spores that are bound to protein binding membranes (PBM), with the commercial Pharmacia UniCap assay (CAP) and with skin prick tests (SPT).

METHODS

Serum from 60 subjects was used; 30 were SPT positive and sensitized to at least one of Alternaria alternata or Aspergillus fumigatus and the other 30 were SPT negative to these fungi but known to be sensitized to non-fungal allergens. All sera were analyzed by CAP against A. alternata, A. fumigatus, Cladosporium herbarum and Epicoccum purpurascens. For HIA, spores from reference cultures belonging to these four species were germinated on PBM, laminated and then probed with each serum. Two independent observers using an ordinal ranking system quantified the intensity and occurrence of the resultant immunoglobulin E (IgE) immunostained haloes around spores and this was statistically compared with the results of the two conventional immunodiagnostic techniques.

RESULTS

Germinated conidia of each species expressed detectable allergen in the HIA. The agreement between the ordinal rank scores assigned by the pair of observers was very good (k >or= 0.8) and only differed for A. fumigatus (k = 0.66) . Between 3% and 7% of SPT negative sera was identified by HIA to have specific IgE towards A. fumigatus and A. alternata. For all four species tested there were strong correlations between HIA and CAP (P < 0.0001). However the correlation of both HIA and CAP to SPT was weaker for A. alternata (r(s) = 0.44, P < 0.0153) and absent for A. fumigatus.

CONCLUSIONS

Overall, the HIA is a new immunodiagnostic technique for the detection of sensitization to fungal allergens that correlates significantly with CAP and to a lesser extent with SPT. This may be due to extract variability and system differences. The significance of this derives from the unique ability of the HIA to measure IgE antibodies to the undegraded allergens that are actively secreted by germinating conidia and hyphae. These are the natural agents of exposure to fungi, and as such, are most likely to be relevant to clinical disease.

Clustering of allergic outcomes within families and households in areas endemic for helminth infections

BACKGROUND

Allergy and helminth infections share key immunological features in terms of Th2 responses. Although in industrialized countries clustering of allergic disorders within families has been frequently reported, such information is lacking from areas where helminth infections are endemic.

METHODS

A total of 466 subjects from 29 families and 112 households participated in this study. Filarial infection, skin test reactivity and IgE to mite as well as total IgE were measured in all samples. Clustering of the allergy-related outcomes due to genetic and household factors was tested.

RESULTS

Genetic factors contributed significantly to the clustering of total IgE and allergen-specific IgE, whereas only household factors contributed to the clustering of SPT positivity.

CONCLUSION

Similar to several studies conducted in western populations, total IgE and allergen-specific IgE are influenced by genetic factors in a population resident in a helminth endemic area. However, clustering of SPT positivity due to genetic factors was not significant in the current study raising the question of whether the presence of helminth infections may override genes that are associated with the expression of tissue reactivity to allergens in the west.