Allergy. 2012 Mar;67(3):353-61.

Prenatal allergen exposures prevent allergen-induced sensitization and airway inflammation in young mice.

Gerhold K, Avagyan A, Reichert E, Seib C, Van DV, Luger EO, Hutloff A, Hamelmann E.

Department of Pediatric Pneumology and Immunology, Charité, Universitätsmedizin Berlin, Germany.

 

Abstract

BACKGROUND:

Immune-modulation such as tolerance induction appears to be an upcoming concept to prevent development of atopic diseases. Pregnancy might present a critical period for preventing allergic sensitization of the progeny. We investigated the effect of maternal allergen exposures during pregnancy on allergen-induced sensitization and airway inflammation in the offspring in a murine model.

METHODS:

BALB/c mice were exposed to aerosolized ovalbumin (OVA) three times per week from day 7 of pregnancy until delivery (day 0). Offspring were systemically sensitized by six intraperitoneal injections with OVA between postnatal days 21 and 35, prior to airway allergen challenges on days 48, 49, and 50. Analyses were performed on day 52. To examine long-lasting effects of maternal OVA exposures some offspring were sensitized between days 115 and 129; analyses took place on day 147.

RESULTS:

Compared to maternal placebo exposures, maternal OVA exposures suppressed OVA-specific IgE serum levels and inhibited development of allergen-induced airway inflammation in the OVA-sensitized offspring on both days 52 and 147. This protective effect was associated with a shift from a predominant Th2 immune response toward a predominant production of the cytokines IFN-γ and IL-10. Further, maternal OVA exposures were associated with development of CD25(+) Foxp3(+) regulatory T cells (T(regs)) in the OVA-sensitized offspring. Depletion of T(regs) or neutralization of IL-10 prior to allergen sensitization re-established OVA-induced sensitization and eosinophilic airway inflammation in the OVA-sensitized offspring.

CONCLUSIONS:

In our model, maternal allergen exposures during pregnancy prevented later allergen-mediated sensitization and airway inflammation by allergen-specific tolerance induction in the offspring.

PMID: 22229690

 

Supplements:

The maternal status of atopy has a strong effect on the development of allergic sensitization of the children (1). Beyond genetic determinants, maternal-fetal interaction at the placental barrier such as transfer of allergens (2) or antibodies (3) may prime the fetal immune system to develop sensitization or tolerance. In accordance, animal models have shown that maternal predominant T helper 2 (Th2) immune responses enhance allergen-mediated Th2 immune responses in the offspring (4), and that maternal allergen-specific T cells transmit increased asthma risk to the offspring, most likely via placental transfer of cytokines (5). Moreover, we found that prenatal initiated exposure to an unspecific immune modulator, lipopolysaccharides (LPS), prevented allergen-mediated sensitization and airway inflammation in young mice (6). The natural mechanism to acquire immune tolerance most likely starts with priming of local dendritic cells by environmental antigens via mucosal barriers of the gastrointestinal or respiratory tract (7,8). In the present study we therefore investigated whether allergen-specific mucosal tolerance induction by means of repetitive airway allergen exposures during pregnancy prevents allergen-induced sensitization and airway inflammation in the very young offspring in a short-term prevention model.

Maternal OVA exposures during pregnancy: Pregnant mice were exposed to aerosolized OVA (10mg/ml, Sigma, USA) for 20min three times per week from day 7 of gestation time until delivery. Pregnant controls were placebo-exposed to aerosolized PBS. Allergen sensitization and airway challenges of the offspring in the short-term prevention model: The offspring were systemically sensitized by six i.p. injections of 10µg OVA between days 21 and 35. Respective controls were placebo-sensitized with PBS. On days 48, 49 and 50, mice of all groups were exposed to aerosolized OVA (10mg/ml, 20min/day) prior to tests on day 52. Long-term prevention model: Some offspring were systemically sensitized with OVA between postnatal days 115 and 129 prior to OVA airway challenges on days 143, 144, and 145. Analyses were performed on day 147. Treatment with rat anti-mouse IL-10R or rat anti-mouse CD25 monoclonal antibodies (mAbs): Offspring were treated i.p. either with 500µg anti-CD25 or 500µg anti-IL-10R two days prior to the first and fourth systemic OVA sensitizations. Respective controls received placebo treatment with polyclonal rat IgG (Sigma, USA). Study groups: Study groups are named by two codes according to maternal exposures (PBSmat, OVAmat) and sensitization procedures in offspring (PBSoffsp, OVAoffsp, OVAoffsp-late). If (m)Abs were applied prior to sensitization, groups are named by maternal exposure/(m)Ab treatment/sensitization procedure in offspring.

Serum levels of total and OVA-specific Ig were measured by means of ELISA. In BAL fluids cells were counted and differentiated due to morphological criteria; levels of IL-5 and IL-12 were assessed by means of ELISA. Allergen-specific cellular reactivity of spleen MNCs cultured with OVA in vitro was determined by 3H-thymidine incorporation. Levels of IL-5, IL-10, IL-13 and IFN-g in supernatants of spleen MNCs cultured with OVA in vitro were assessed by means of ELISA. Flow cytometry was used to assess frequencies of maternal Tregs in spleens on postnatal day 21, frequencies of Tregs in bronchial lymph nodes in the offspring on day 52, and frequencies of Tregs in spleens, bronchial lymph nodes and lung tissues in the offspring of Thy-1.1+ male and Thy-1.2+ female mice on day 52.

In conclusion, repeated maternal allergen exposures during pregnancy mediated expansion of Tregs in the offspring inducing allergen-specific tolerance and inhibiting the development of allergen-induced sensitization and airway inflammation. Prenatal mucosal tolerance induction might thus provide an innovative concept for primary prevention of atopic diseases, at least in high-risk families. 

 

Gerhold_Figure_1_short_term_prevention_model_revisedFigure 1: Short-term prevention model. Following OVA exposures during pregnancy, offspring were sensitized (days 21-35) and challenged with OVA. On day 52, serum levels of OVA-specific IgE (A), the cellular influx into the airways (B/C) and local IL-5 levels in BAL fluids (D) were analyzed. p<0.025 (Mann-Whitney-U test).

 

Gerhold_Figure_2_cytokines_revisedFigure 2: Cytokines in the short-term prevention model. Following maternal OVA exposures, offspring were sensitized (days 21-35) and challenged with OVA. On day 52, levels of IL-5 (A), IL-13 (B), IL-10 (C), and IFN-g (D) were measured in supernatants of spleen cells cultured with OVA in vitro. p<0.025 (Mann-Whitney-U test).

 

Gerhold_Figure_3_Tregs_revisedFigure 3: Tregs. In OVA-exposed mothers splenic Tregs (A) and OVA-specific IL-10 production (B) were quantified on day 21; p<0.05 (p versus PBSmat, Mann-Whitney-U test). Tregs in bronchial lymph nodes of OVA-sensitized offspring were counted (C), and IL-10- and IFN-g-producing lung Tregs of maternal and fetal origins were analyzed in OVA-sensitized offspring of Thy-1.1+ male and Thy‑1.2+ female mice (D).

 

Gerhold_Figure_4_role_of_Tregs_revisedFigure 4: Role of Tregs. Offspring of OVA-exposed mothers were sensitized and challenged with OVA. On day 52, OVA-specific cellular reactivity by spleen MNCs was analyzed (A). Following treatment with mAbs against CD25 or IL-10R prior to and during OVA sensitization, OVA-specific IgE serum levels (B) and airway inflammation (C,D) were examined on day 52. p<0.025 (Mann-Whitney-U test)

 

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Prof. Dr. Eckard Hamelmann
University Children’s Hospital,
Ruhr-University Bochum
Alexandrinenstraße 5, D-44791 Bochum
Tel: +49 (0)234 509-2610
Fax: +49 (0)234 509-2612
š e.hamelmann@klinikum-bochum.de

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