Impact of genetic variants in IL-4, IL-4 RA and IL-13 on the anti-pneumococcal antibody response

BACKGROUND

Significant differences in immune responses upon vaccination have been described, suggesting genetics are important in determining the magnitude of vaccine responses. The interleukin (IL)-4 pathway, including IL-4, IL-13 and the IL-4 receptor alpha chain (IL-4 Ralpha), is central to humoral responses and therefore could have an impact on vaccine responsiveness.

OBJECTIVE

To investigate whether single nucleotide polymorphisms (SNPs) in the IL-4, IL-13 and IL-4 RA genes influence pneumococcal serotype-specific IgG antibody responses.

METHODS

SNPs in the IL-4 gene (C -589T, G2979T), the IL-13 gene (G -1112A, Arg130Gln) and in the IL-4 RA gene (Ile50Val, Gln551Arg) were investigated in isolation and in combination, for their influence on serotype-specific IgG antibody responses upon combined pneumococcal conjugate and polysaccharide vaccinations in children with a history of recurrent otitis media.

RESULTS

Lower antibody responses were observed for alleles previously associated with atopy, IL-4 -589T, IL-4 2979T and IL-4 Ralpha 551Gln. Effects were stronger in gene haplotype combinations or in multiple haplotype combination analyses.

CONCLUSION

This study highlights the importance of host genetic factors in vaccine responses. Furthermore, it supports the approach of studying the effect of combinations of multiple alleles, in haplotypes or in combinations of haplotypes, on complex phenotypes within a biological pathway.

Associations of a novel IL4RA polymorphism, Ala57Thr, in Greenlander Inuit

BACKGROUND

A novel IL4RA polymorphism, Ala57Thr, was identified in Greenlander Inuit.

OBJECTIVE

We sought to determine whether the novel Thr57 allele is population specific and to assess the associations of Ala57Thr and Ile50Val with atopy in 2 Inuit populations.

METHODS

Ala57Thr and Ile50Val were genotyped in 651 Inuit living in Denmark, 1295 Inuit living in Greenland, and 1329 individuals from 7 populations from widely differing global locations. In Inuit the polymorphisms were evaluated for associations with atopy, rhinitis, asthma, and pulmonary function.

RESULTS

Thr57 was in linkage disequilibrium with Ile50 (D' = 1, r(2) = 0.13) and was common (33%) in the Inuit but rare (<0.6%) in all other populations. In Inuit living in Denmark, the Thr57 allele (in a dose-dependent manner) and the Ile50/Thr57 haplotype were associated with lower risk of atopy (P(linear) = .003 and P = .034, respectively), with similar trends observed for atopic rhinitis and atopic asthma. In Inuit living in Greenland, Thr57 was not associated with atopy or atopic diseases, but Ile50 was weakly associated with lower risk of atopy.

CONCLUSION

The novel IL4RA Ala57Thr was common in and population specific to Greenlander Inuit, with Thr57 associated with a lower risk of atopy in those living in Denmark. Hence a full investigation of genotype-phenotype relationships in a given population can only be achieved if each gene is screened for novel polymorphisms in that population.

CLINICAL IMPLICATIONS

Clinical risk attributable to variations in a gene in an ethnic group requires that all variations of the gene are known for that group.

IgE and IgG anti-house dust mite specificities in allergic disease

BACKGROUND

There are few studies that quantitatively compare IgE and IgG antibody binding to the major and minor house dust mite allergens.

OBJECTIVE

To measure the IgE and IgG antibody specificities produced by adults and children, including children admitted to an emergency department for asthma.

METHODS

Antibodies were measured by solid-phase microtiter assays.

RESULTS

Children recruited from the emergency department had similar titers and patterns of IgE antibody binding compared with children without acute disease. Der p 1 and 2 bound 50% to 65% of the IgE antibody, and most of the remaining binding was to Der p 4, 5, and 7. Der p 3, 8, 10, and 20 induced low titers. The pattern was similar across a wide range of antihouse dust mite titers. IgG(1) and IgG(4) antibodies predominantly bound the major and midrange allergens and were mainly found in children with allergy. Children recruited in the emergency department had lower titers.

CONCLUSION

The same IgE antibody-binding pattern and predominant contribution of Der p 1 and 2 was found across a wide range of total IgE antibody titers and for children admitted to an emergency department. IgG(1) and IgG(4) antibodies bound to the more allergenic specificities and were largely found in children with allergy. The IgG antibody titers were lower in sera from children admitted to the emergency department for asthma exacerbations.

CLINICAL IMPLICATIONS

Der p 1 and 2 and possibly Der p 4, 5, and 7 provide a formulation suitable for immunotherapy and diagnosis. Low IgG antibodies were a feature of acute disease.

Can asthma be predicted from an early age?

PURPOSE OF REVIEW

The ability to identify risk factors for asthma as early as possible in life would be valuable as it would allow accurate prognoses to be made and interventional therapies to be tested. The aim of this article is to review the most important approaches made in this area and to consider their relevance.

RECENT FINDINGS

Epidemiological studies have started to include genetic analyses and this combined approach has provided new information on genetic susceptibility to disease and its interactions with the environment. For example, genetic variations in innate immunity genes may explain why particular individuals are substantially less likely to develop asthma when exposed to farm animals in early life. Another example is using populations with long-term, longitudinal databases to determine the age relationships of specific genetic susceptibilities. Furthermore, genetic studies have started to provide new explanations for the known relationship between maternal smoking during pregnancy and adverse respiratory outcomes in the offspring. Genetic studies have also provided new insights into the latest physiological studies reporting that the level of infant respiratory function is associated with respiratory outcomes in the second decade of life. Finally, important advances continue to be made in our understanding of the immunological processes relevant to early life and their influence on the development of atopy and asthma.

SUMMARY

Progress in defining early risk factors for asthma has been made in several areas. The most important findings have come from studies combining epidemiological, genetic and immunological assessments.

Association between asthma-related phenotypes and the CC16 A38G polymorphism in an unselected population of young adult Danes

The gene for Clara cell 16-kDa (CC16) protein is a promising candidate for asthma susceptibility. The CC16 38A allele has been associated with decreased CC16 plasma levels and increased incidence of asthma in Australian children. To date these results have not been replicated in adults. Therefore, potential links between CC16 A38G, asthma and atopy were investigated in an unselected population of young adult Danes. Four hundred sixty-four Danes, aged 19-29 years, from Copenhagen participated in an asthma and allergy phenotype-genotype study. Genotyping was done by Sau96I restriction digestion of PCR products spanning the A38G polymorphism. Potential A38G genotype and asthma-related phenotype associations were investigated using regression analysis, adjusting for potential confounders where appropriate. Adults with the 38AA genotype had higher odds of current asthma (OR 3.2, P=0.013) and ever asthma (OR 2.2, P=0.045) compared with those with the 38GG genotype. Adjusting for atopy had minimal effect on this relationship. A positive linear trend was evident between the 38A allele and atopic dermatitis (OR 1.67, P=0.02). No associations were found between the A38G polymorphism and rhinitis, atopy, forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC), airway responsiveness (AR) to histamine or peripheral blood eosinophil level (PBEL). An atopy-independent association between CC16 38AA and asthma prevalence was identified, suggesting the CC16 38A allele predisposes to adult asthma independent of Th1/Th2 processes. This finding is consistent with previous studies in children, but is the first reported association between CC16 A38G and asthma in adults. CC16 38A also displayed a positive linear trend with atopic dermatitis.

Measuring exhaled nitric oxide levels in adults: the importance of atopy and airway responsiveness

BACKGROUND

Raised exhaled nitric oxide (Feno) levels have been associated with asthma. However, we have found that in children, Feno was increased in atopic children with increased airway responsiveness (AR), and this was independent of a diagnosis of asthma.

STUDY OBJECTIVES

The current study was designed to test the hypothesis that in adults there is no association between Feno and asthma after controlling for atopy and AR.

MEASUREMENTS

One hundred fifteen adults (77 women; mean age, 41 years) underwent an assessment that included Feno measurements, spirometry, skin-prick testing, blood eosinophil count, and inhaled histamine challenge (results are expressed as a dose-response slope [DRS]).

RESULTS

When only atopic individuals were considered (n = 73), Feno was positively associated with the DRS (p = 0.003), male gender (0.02), and negatively associated with current smoking (p = 0.09). Only male gender (p = 0.03) was associated with Feno among nonatopic individuals (n = 36). In multivariate analysis, there was no association between Feno and current asthma, current wheeze, or asthma ever.

CONCLUSIONS

We conclude that in adult subjects, elevated Feno measurements are associated with a phenotype characterized by atopy and increased AR regardless of the presence of asthma or asthma-like symptoms.

The role of parasites in genetic susceptibility to allergy: IgE, helminthic infection and allergy, and the evolution of the human immune system

There have been numerous studies in the mouse illustrating the dichotomy of T cell responses, with the common classification orchestrated around Th1 vs. Th2 responses. This classification is now widely applied to human disease as well and the generic conclusion is that the Th1 responses are more likely to occur secondary to specific microbiologic insult but also inflammatory responses. In contrast, the Th2 response is the prevalent response in subjects with atopy and allergic disease but is also the mechanism for protection against helminthic infections. Unfortunately, the paradigm of Th1 vs. Th2 is not as clear in the human as it is in mouse models. Even so, the immunological mechanisms responsible for IgE production that are protective in helminthic infections, i.e. Schistosoma, are similar to those for the production of specific IgE against allergens. In fact, there also appear to be associations in the memory T cell subpopulation CD4+CD45RO+ and the elicitation of IgE against both parasites and allergens. In this review, we present the overall contemporary scheme on the role of parasites in genetic susceptibility to allergic IgE, helminthic infections with specific discussion of its implications for the evolution of the human immune system.

The relationship between infant airway function, childhood airway responsiveness, and asthma

The relationship between reduced pulmonary function in early life and persistent wheeze (PW) in school-aged children remains uncertain. In this study, VmaxFRC was assessed at 1 month of age, and the presence of wheeze up to 11 years of age was prospectively identified. At 11 years of age, airway responsiveness (AR) to inhaled histamine and atopy were assessed. Recent wheeze at 11 years of age was associated with a reduced mean z score for VmaxFRC at 1 month of age (-0.41 [SD 0.91], n = 31) compared with no recent wheeze (0.04 [SD 1.00], n = 153, p = 0.03). Wheeze between 4 and 6 years that persisted at 11 years (PW) was most prevalent among those with reduced VmaxFRC at 1 month and atopy aged 11 years (p = 0.002) or reduced VmaxFRC and increased AR aged 11 years (p = 0.015). When all factors were considered, reduced VmaxFRC at 1 month (p = 0.03) and increased AR aged 11 years (p < 0.001) were independently associated with PW (n = 17) compared with other outcomes (n = 129). Reduced airway function present in early infancy is associated with PW at 11 years of age, and this relationship is independent of the effect of increased AR and atopy in childhood.

Age-specific relationship between CD14 and atopy in a cohort assessed from age 8 to 25 years

CD14 influences postnatal switching of T helper cell responses. CD14 C-159T has been associated with altered CD14 and IgE levels in cross-sectional studies. Identifying whether associations vary with age requires data from children of the same age followed longitudinally over many years. In this study, an unselected population with extensive longitudinal data was used to test the hypothesis that CD14 C-159T was associated with early-onset atopy. A total of 305 subjects were assessed on up to seven occasions between ages 8 and 25 years by questionnaire, histamine challenge, and skin prick test. For atopy, airway hyperresponsiveness (AHR), and wheeze, each subject was classified as having early onset, late onset, or no disease onset during follow-up. Compared with subjects with -159CT and -159TT, subjects with -159CC had an odds ratio of 2.2 (p = 0.018) for early-onset atopy and an odds ratio of 2.6 (p = 0.019) for early-onset AHR. Cross-sectional analysis showed increased prevalence of -159CC in subjects with atopy and AHR in childhood but not adulthood. These data suggest that the influence of CD14 -159C on the atopic phenotype may be age specific, exerting an effect during midchildhood, which is no longer apparent by early adulthood.

Risk factors and epidemiology

What we know: No one gene is a major cause of asthma. Some racial groups are more at risk of asthma than others. Early exposure to domestic animals appears to reduce the chance of developing asthma. Good hygiene may increase the likelihood of asthma. Impaired early airway function predisposes to asthma. What we need to know: How do several minor genetic factors combine to increase the risk of asthma in individuals and in population groups? Does early exposure to allergens promote sensitisation or tolerance? How do viruses precipitate asthma? Can acute asthma be treated by treating viral respiratory infections? Does impaired early airway function predispose to asthma throughout childhood?

Drug delivery

What we know: In preschool children, small-volume spacers perform better than large-volume spacers. Detergent is the best antistatic agent for spacers, increasing lung delivery two- to threefold, but it must not be rinsed off. A mouthpiece should be used in children aged 2-3 years or older, as lung delivery is two- to threefold higher for oral inhalation than nasal inhalation (ie, by mask). Inhaled drug doses do not generally need to be reduced in infants and young children owing to inefficiencies of delivery in younger patients. Nebulisers are "dinosaurs" and not needed for most children with asthma. What we need to know: What is the best inhalation technique for spacers? How long should children breathe, how many breaths should they take, and at what age should they breath-hold? How should children, parents and doctors be instructed to achieve optimal levels of electrostatic charge reduction for spacers? How much should inhaled steroid dose be reduced when a spacer is used optimally? What dosing instructions should be given for beta(2)-agonists delivered by spacer?

Infants with flow limitation at 4 weeks: outcome at 6 and 11 years

Within a longitudinal study of lung function in 243 infants, we identified a group of 23 individuals with flow limitation in tidal expiration. In infancy, flow-limited children have reduced lung function and increased airway responsiveness (AR), and at 2 years of age they are diagnosed with asthma more frequently. We hypothesized that these observations would persist throughout childhood. Data from ages 3 to 11 years were analyzed. Only at 4 years of age did the flow-limited group have increased wheeze compared with other cohort members (odds ratio, 4.25; 95% confidence interval [CI], 1.11 to 16.2; p = 0.04; n = 114). At 6 years of age, 117 cohort members were seen. The flow-limited group (n = 14) had greater AR (p = 0.009) and reduced mean FEV(1) (131 ml; 95% CI, 16 to 246; p = 0.03) and FEF(25-75) (0.28 L/second; 95% CI, 0.05 to 0.52; p = 0.02). At 11 years of age, 183 children were seen and the flow-limited group (n = 18) had greater AR (p = 0.02) and a trend toward reduced mean FEF(25-75) (0.24 L/second; 95% CI, -0.02 to 0.49; p = 0.08). Atopy and parental asthma were not increased in the flow-limited group. We suggest that the physiologic abnormality that causes flow limitation in early infancy may identify an at-risk group, different from asthma, who have reduced lung function and increased airway responsiveness in later life.