Comment

Revising the immunological theories of asthma and allergy

House dust mite extract–based allergen immunotherapy (AIT) to treat house dust mite allergy is substantially effective but still presents some safety and efficacy concerns that warrant improvement. Several major allergen-based approaches to increase safety and efficacy of AIT have been proposed. One of them is the use of the group 2 allergen, Der p 2.

We sought to investigate the immunomodulatory effects of sialic acid–modified major allergen recombinant Der p 2 (sia-rDer p 2) on PBMCs from healthy volunteers.

We activated PBMCs with anti-CD3/CD28 antibodies and incubated them at 37°C for 6 days in the presence or absence of either native rDer p 2 or α2-3 sialic acid–modified rDer p 2 (sia-rDer p 2). We assessed the changes in CD4⁺ T-cell activation and proliferation by flow cytometry and changes in T-lymphocyte cytokine production in cell culture supernatant by ELISA.

We observed that PBMCs treated with sia-rDer p 2 presented with a markedly decreased expression of CD69 and an increased abundance of LAG-3⁺ lymphocytes compared with cells treated with rDer p 2. Moreover, PBMCs treated with sia-rDer p 2 showed a reduced production of IL-4, IL-13, and IL-5 and displayed a higher IL-10/IL-5 ratio compared with rDer p 2–treated PBMCs.

We demonstrate that sia-rDer p 2 might be a safer option than native rDer p 2 for Der p 2–specific AIT. This is most relevant in the early phase of AIT that is often characterized by heightened T_H2 responses, because sia-rDer p 2 does not enhance the production of T_H2 cytokines.

Recent research has emphasized the need to better discriminate asthma phenotypes and consider underlying mechanistic endotypes in epidemiologic and clinical studies. Although allergic asthma and nonallergic asthma are frequently combined into 1 disease category in observational research and clinical trials, few studies have investigated the extent to which these 2 separate phenotypes are associated with distinct cytokine immunologic profiles in a representative young adult population.

To investigate the cytokine production-based endotypes underlying the clinical phenotypes of allergic and nonallergic asthma in a population-based birth cohort evaluated as young adults.

Participants included 18- to 21-year-old members (n = 540) of a suburban Detroit birth cohort study, the Childhood Allergy Study. Phorbol myristate acetate–stimulated whole blood interleukin (IL)-4, IL-5, IL-10, IL-12, IL-13, IL-17A, IL-17F, IL-22, and interferon-γ secretory responses were analyzed for associations comparing participants with allergic vs nonallergic asthma phenotypes with those without asthma.

T-helper cell type (T_H) 2-polarized responses, measured as higher mean IL-5 and IL-13 secretions and lower ratios of interferon-γ and IL-12 to 3 T_H2 cytokines (IL-4, IL-5, or IL-13), were observed only in participants with allergic asthma. Nonallergic asthma was associated with T_H1-polarized responses, including higher adjusted interferon-γ secretion compared with participants with allergic asthma and, surprisingly, those without asthma (odds ratio 2.5, confidence interval 1.2–5.1, P < .01).

As expected, young adults with a history of an allergic asthma phenotype exhibited a T_H2–polarized cytokine response after polyclonal stimulation. However, T_H1 polarization was observed in patients with a history of nonallergic asthma. Allergic and nonallergic asthma are associated with etiologically distinct immune endotypes, underscoring the importance of discriminating these endotypes in research analyses and clinical management.

Immunologic responses at birth likely relate to subsequent risks for allergic diseases and wheezing in infancy; however, the influences of parental characteristics and prenatal factors on neonatal immune responses are incompletely understood.

This study investigates potential correlations between urban parental, prenatal, and perinatal factors on innate and adaptive stimuli-induced cytokine responses.

Five hundred sixty and 49 children of parents with and without allergic disease or asthma, respectively, were enrolled into a prospective birth cohort study (Urban Environment and Childhood Asthma). Cord blood mononuclear cells were incubated with innate and adaptive immune stimuli, and cytokine responses (ELISA) were compared with season of birth, parental characteristics, in utero stressors, and fetal growth.

Many cytokine responses varied by season of birth, including 2-fold to 3-fold fluctuations with specific IFN-α and IFN-γ responses. Birth weight was inversely associated with IFN-γ responses to respiratory syncytial virus (R = −0.16), but positively associated with IL-8 responses to a variety of innate stimuli (R = 0.08-0.12). Respiratory syncytial virus–induced cytokine responses were 21% to 54% lower in children of mothers with asthma. Cytokine responses were generally lower in babies born to parents with allergy/asthma.

Innate cytokine responses are associated with parental allergic or airway disease, somatic fetal growth, ethnicity, and season of birth. Collectively, these findings suggest that urban prenatal exposures and familial factors affect the development of the fetal immune system.

There is uncertainty about the nature of the relationship between mite allergen exposure during infancy and the expression of allergic diseases in childhood.

We sought to explore the relationships between repeated measurements of mite allergen exposure during the first 5 years of life and clinical allergic disease outcomes at age 5 years.

In a birth cohort of 516 at-risk children, 13 bed dust samples were collected between birth and 5 years of age and analyzed for mite allergen. At age 5 years, the presence of mite atopy was assessed based on skin prick test results, and clinical assessments for asthma, eczema, and wheeze were conducted. The association of allergen exposure with each clinical outcome was examined by means of logistic regression, with adjustments for potential confounders.

The lowest and highest mite exposure quintiles, expressed as mean allergen concentration averaged over 0 to 5 years, were associated with a lower prevalence of mite atopy and of asthma compared with intermediate levels of exposure. These relationships, when determined by using average allergen concentration over 0 to 18 months, were weaker.

This study demonstrates a nonlinear relationship between mite allergen exposure and clinical outcomes in this generally high mite allergen environment.

Uteroglobin-related protein 1 (UGRP1) is a secretory protein expressed in the airways and is speculated to have anti-inflammatory activity. In the mouse, its gene expression is down-regulated by inter-leukin (IL)-5 and -9, and up-regulated by IL-10. However, the precise role of UGRP1 in human inflammatory airway diseases such as asthma has not been clarified. The objectives of this study were to establish an ELISA system to quantify UGRP1 protein, and to examine whether plasma UGRP1 levels are associated with the G-112A polymorphism, asthma susceptibility, and its severity.

152 asthma patients and 103 normal controls were involved in this study. Mice were immunized with recombinant UGRP1 and hybridoma cell lines were established. A sandwich ELISA system was established by using two monoclonal antibodies recognizing different epitopes. Plasma UGRP1 levels were measured with the ELISA system and the G-112A allele was detected by using real-time PCR.

An ELISA system was established that allowed determination of UGRP1 levels within the range of 9.6–1250 pg/ml. The mean plasma UGRP1 levels for subjects with -112A allele were significantly lower than those without it (p = 0.025). Although there was no significant difference in the plasma UGRP1 levels between asthma patients and controls (p = 0.13), severe asthma patients without oral corticosteroid had significantly lower plasma UGRP1 levels compared to mild- or moderate-asthma patients and controls (p = 0.004, 0.03 and 0.003, respectively).

The ELISA system for quantifing UGRP1 protein was established, and plasma UGRP1 levels were associated with the G-112A UGRP1 gene promoter polymorphism and the severity of asthma.

Epidemiological evidence, in vitro studies and animal models suggest that exposure to the bacterial endotoxin lipopolysaccharide (LPS) can influence the development and severity of asthma. Although it is known that signaling through Toll-like receptors (TLR) is required for adaptive T helper cell type 1 and 2 responses, it is unclear whether the LPS ligand TLR 4 is expressed on CD4⁺ and CD8⁺ T-lymphocytes and if so, whether LPS could modulate the T_H1 or T_H2 response in this context.

The present authors have, therefore, examined the expression of TLR 4 on peripheral blood CD4⁺ and CD8⁺ T-lymphocytes using RT-PCR method and FACS analyses. Furthermore, the authors have studied the IL-12-induced expression of the T_H1-associated cytokine INF-γ and the IL-4-induced expression of the T_H2-specific cytokine IL-5 in the presence of LPS using ELISA and compared nine atopic asthmatic subjects and eleven nonatopic normal volunteers.

There was an increased anti-CD3/anti-CD28-induced IL-5 expression in T cells of asthmatics compared with normals (p < 0.01). In the presence of IL-4 (10 ng/ml), there was an additional increase in IL-5 expression and this additional increase was greater in T cells of normals compared with asthmatics (p < 0.05). There was an expression of INF-γ in anti-CD3/anti-CD28-induced T-lymphocytes without differences between both groups (NS). In the presence of IL-12 (10 ng/ml), there was an increase in INF-γ release without differences between normals and asthmatics (NS).

In the presence of different concentrations of LPS (10 ng/ml, 1 μg/ml), there was a decrease in IL-4-induced IL-5 expression without differences in both groups, indicating an intact T_H2 response to bacterial endotoxin LPS in asthma. Interestingly, LPS increased the IL-12-induced INF-γ release in a concentration-dependent manner in T-lymphocytes of normals but this could not be found in T cells of asthmatics, indicating an impaired T_H1 response to bacterial endotoxin LPS in asthma.

In addition, there was a TLR 4 expression on CD4⁺ T-lymphocytes of normals and to a lesser extent in asthmatics but this TLR 4 expression could not be found on CD8⁺ T cells of both groups.

In conclusion, there may be an impaired concentration-dependent LPS-induced T_H1 rather than a T_H2 response in allergic adult asthmatics compared with normal volunteers. One reason for this could be a reduced TLR 4 expression on CD4⁺ T-lymphocytes of asthmatic subjects.