Maternal allergen immunization during pregnancy in a mouse model reduces adult allergy-related antibody responses in the offspring

Closer and closer? Maternal immunization: current promise, future horizons

This state-of-the art manuscript highlights our current understanding of maternal immunization-the practice of vaccinating pregnant women to confer protection on them as well as on their young infants, and thereby reduce vaccine-preventable morbidity and mortality. Advances in our understanding of the immunologic processes that undergird a normal pregnancy, studies from vaccines currently available and recommended for pregnant women, and vaccines for administration in special situations are beginning to build the case for safe scale-up of maternal immunization. In addition to well-known diseases, new diseases are emerging which pose threats. Several new vaccines are currently under development and increasingly include pregnant women. In this manuscript, targeted at clinicians, vaccinologists, scientists, public health practitioners, and policymakers, we also outline key considerations around maternal immunization introduction and delivery, discuss noninfectious horizons for maternal immunization, and provide a framework for the clinician faced with immunizing a pregnant woman.

Maternal Vaccination as an Essential Component of Life-Course Immunization and Its Contribution to Preventive Neonatology

Maternal immunisation schedules are increasingly coming under the spotlight as part of the development of lifetime immunisation programmes for the role that they play in improving maternal, foetal, and neonatal health. Maternally-acquired antibodies are critical in protecting infants during the first months of their lives. Maternal immunisation was previously overlooked owing to concerns regarding vaccinations in this untested and high-risk population but is now acknowledged for its potential impact on the outcomes in many domains of foetal and neonatal health, aside from its maternal benefits. This article highlights the role that maternal immunisation may play in reducing infections in preterm and term infants. It explores the barriers to antenatal vaccinations and the optimisation of the immunisation uptake. This review also probes the part that maternal immunisation may hold in the reduction of perinatal antimicrobial resistance and the prevention of non-infectious diseases. Both healthcare providers and expectant mothers should continue to be educated on the importance and safety of the appropriate immunizations during pregnancy. Maternal vaccination merits its deserved priority in a life-course immunization approach and it is perhaps the only immunization whereby two generations benefit directly from a single input. We outline the current recommendations for antenatal vaccinations and highlight the potential advances in the field contributing to “preventive neonatology”.

Maternal Immunization: New Perspectives on Its Application Against Non-Infectious Related Diseases in Newborns

The continuous evolution in preventive medicine has anointed vaccination a versatile, human-health improving tool, which has led to a steady decline in deaths in the developing world. Maternal immunization represents an incisive step forward for the field of vaccination as it provides protection against various life-threatening diseases in pregnant women and their children. A number of studies to improve prevention rates and expand protection against the largest possible number of infections are still in progress. The complex unicity of the mother-infant interaction, both during and after pregnancy and which involves immune system cells and molecules, is an able partner in the success of maternal immunization, as intended thus far. Interestingly, new studies have shed light on the versatility of maternal immunization in protecting infants from non-infectious related diseases, such as allergy, asthma and congenital metabolic disorders. However, barely any attempt at applying maternal immunization to the prevention of childhood cancer has been made. The most promising study reported in this new field is a recent proof of concept on the efficacy of maternal immunization in protecting cancer-prone offspring against mammary tumor progression. New investigations into the possibility of exploiting maternal immunization to prevent the onset and/or progression of neuroblastoma, one of the most common childhood malignancies, are therefore justified. Maternal immunization is presented in a new guise in this review. Attention will be focused on its versatility and potential applications in preventing tumor progression in neuroblastoma-prone offspring.

Maternal Antiasthma Simplified Herbal Medicine Intervention therapy prevents airway inflammation and modulates pulmonary innate immune responses in young offspring mice

BACKGROUND

Maternal asthma is a risk factor for asthma in offspring; however, transmission of the risk for allergic asthma without direct offspring sensitization has not been explored.

OBJECTIVE

To determine whether offspring from mothers with ovalbumin (OVA)-sensitized asthma would develop airway disease at first-ever exposure to OVA and whether preconception maternal treatment with the Antiasthma Simplified Herbal Medicine Intervention (ASHMI) or dexamethasone (DEX) could modify this risk in offspring.

METHODS

Female BALB/c mice (F0) with OVA-induced asthma were generated using established protocols. Mice with asthma were treated with ASHMI, DEX, or water for 6 to 7 weeks. Naive mice served as controls. Subsequently, mice were mated. Twelve-day-old F1 offspring received 3 consecutive intranasal low- or high-dose OVA exposures without sensitization. Forty-eight hours later, airway inflammation, mucus hypersecretion, serum antibodies, and cytokines were evaluated.

RESULTS

Offspring from OVA-sensitized mothers, but not naive mothers, showed eosinophilic and neutrophilic airway inflammation, and mucus hyperplasia after OVA exposure and he presence of OVA-specific IgG1 and IgG2a. Offspring of ASHMI- and DEX-treated mothers showed decreased airway inflammation and mucus hypersecretion after low-dose OVA (P < .05-.001 for the 2 comparisons vs offspring of OVA/Sham mothers). Offspring of ASHMI-treated, but not DEX-treated, mothers were protected after the high-dose OVA challenge (P < .05-.01 vs offspring OVA/Sham). Maternal ASHMI therapy was associated with increased IgG2a (P < .01 vs offspring of OVA/Sham mothers) and decreased bronchoalveolar lavage fluid CXCL-1 and eotaxin-1 levels (P < .01 and P < .05, respectively, vs offspring of OVA/Sham mothers).

CONCLUSION

Offspring of mothers with OVA-induced asthma developed airway inflammation and mucus to first-ever OVA exposure without prior sensitization. Maternal therapy with ASHMI was superior to DEX in decreasing offspring susceptibility to airway disease and could be a strategy to lower asthma prevalence.

Offspring IgE responses are influenced by levels of maternal IgG transferred in early life

PROBLEM

Maternal immune responses may interfere with offspring allergy development as maternal immunization may suppress IgE development, while maternal allergy may promote allergy. Therefore, we investigated the effect of two different maternal treatments on airway allergy in female and male offspring.

METHOD OF STUDY

Pregnant mice were immunized (IMM) with ovalbumin (OVA) or immunized and airway-challenged (IMM+AI). At different ages, airway allergy to OVA was induced in offspring by intranasal sensitization.

RESULTS

Maternal IgG1 was found at higher levels in IMM+AI than in IMM offspring. After sensitization, the suppression of OVA-specific IgE and IgG1 was complete in juvenile offspring but waned with age concurrently with maternal IgG1 levels. Cytokine secretion, lung inflammation, and B cell priming were not suppressed although IgE responses were.

CONCLUSIONS

High compared with low levels of maternal IgG1 were associated with lower TH 2 antibody production after adult offspring were re-exposed to OVA. Thus, offspring allergy-related responses appeared to be shaped by maternal antibody levels.

Suppression of allergen-specific IgE in offspring after preconceptional immunisation: maternal, paternal and genetic influences

Immunisation of female mice with the allergen ovalbumin (OVA) during pregnancy reduces the OVA-specific IgE response in adult offspring. To approach primary prevention strategies for allergy, we investigated to what extent genetic, paternal and maternal factors influence this suppressive effect on allergic sensitisation in offspring and investigated the possibility of pregestational immunisation. Maternal allergen immunisation reduced OVA-specific IgE levels in immunised offspring, even after maternal immunisation up to 8 weeks before conception without further allergen exposure. Immunisation of immunodeficient BALB/c severe combined immune deficiency (SCID) dams mated with wild type males did not lead to IgE suppression in offspring, indicating the importance of a functional maternal immune system. Immunisation of male mice before the relevant spermatogenesis did not cause antibody suppression in offspring. OVA-specific IgG1, presumably of maternal origin, was present in naïve offspring only from immunised dams and was associated with suppressed IgE responses after offspring immunisation. The IgE-suppressive effect of maternal immunisation was demonstrated in all three immunocompetent strains tested (NIH/OlaHsd, BALB/cA and C57BL/6 mice). In conclusion, suppression of allergen-specific IgE production in offspring could not be induced by paternal immunisation, and genetic factors were of minor importance. In contrast, we demonstrate the necessity of maternal factors, possibly allergen-specific IgG1, resulting from a functional adaptive immune response, for the IgE-suppressive effect in offspring. These maternal factors could be induced by immunisation of female mice even before conception.

Mother to child transfer of IgG and IgA antibodies against Dermatophagoides pteronyssinus

There is strong evidence from animal models that placental and/or breast milk-mediated transfer of maternal allergen-specific IgG prevents allergic immune responses in the progeny. Both human and animal data also point to IgA as having an important regulatory role. In contrast, little is known about maternal transfer of IgG and IgA specific for respiratory allergens in humans. Dermatophagoides pteronyssinus (Der p) is an indoor allergen that is a major cause of asthma worldwide. We analysed maternal to child Der p-specific IgG and IgA transfer in a cohort of 77 paired maternal and child samples. We found Der p-specific IgG and its IgG1, IgG2 and IgG4 subclasses in all cord blood samples. Except for IgG1, cord levels were higher in newborns from atopic mothers (n = 29) compared to non-atopic mothers (n = 48). Der p-specific IgA was found in all colostrum samples and levels were independent of maternal atopic status. Notably, anti-Der p IgG was also found in colostrum and levels were higher in atopic mothers. We believe that our work is a critical first step in the identification of early factors that may impact asthma development and should guide the development of clinical studies that assess whether Der p-specific IgG and IgA protect children from allergy as demonstrated in animal models.

Maternal immunization to modulate the development of allergic response and pathogen infections

This article reviews recent experimental approaches of preventive strategies regarding allergy and infections by pathogens, particularly in early childhood, by targeting maternal immunomodulation. Basic research is essential to understand maternal vaccination as a strategy to control allergic disease and bacterial and viral infections; thus, providing support for future translational research. The environmental stimuli and host genetic factors, along with maternal influences in early life when immune systems are developing and during postnatal life, are essential for the decision between tolerance induction or allergen sensitization. Maternal immunomodulation strategies should serve as a challenge when attempting to halt the spread of allergy responses and viral infections, until the innate and adaptive arms of the immune system of the neonates are competent.

Preclinical animal models of asthma and chronic obstructive pulmonary disease

Animal models of disease serve a vital function in the search for novel therapeutic approaches. While these systems cannot replicate human disease, they can be used to mimic and investigate mechanisms believed to be central to disease pathogenesis. In this review, we discuss the most relevant and commonly used animal models for asthma and chronic obstructive pulmonary disease (COPD); specifically, models developed for the mouse, rat and guinea pig. Allergens, such as ovalbumin, can be used to induce an IgE-dependent response characterized by early- and late-phase bronchoconstriction, inflammation and airway hyper-responsiveness similar to what occurs in asthmatics. Similarly, elastase and cigarette smoke can be used to replicate steroid-insensitive and progressive inflammation, which leads to lung pathologies that are observed in COPD patients. We also discuss how these models are developing in new ways to more closely reflect the clinical disease. Unfortunately, these models have limitations due to differences in genetics, anatomy and physiology among the species, many of which we have highlighted; however, understanding these differences, careful characterization of these models and parallel in vitro or ex vivo studies using human and relevant animal tissues will overcome some of these issues. In spite of these limitations, as long as studies are designed and interpreted appropriately, in vivo models will continue to be vital for furthering our understanding of disease pathogenesis and for developing new therapies.

Maternal respiratory sensitization and gestational allergen exposure does not affect subsequent pup responses to homologous or heterologous allergen

Evidence suggests that the predisposition towards atopy begins early in life. Maternal allergy has been associated with an increased risk of the development of allergic disease in offspring. Some studies suggest that the development of childhood atopy may also be influenced by prenatal allergen exposure. In this study, a respiratory allergen exposure model was used to determine the impact of maternal sensitization (with or without additional exposures during pregnancy) on subsequent pup responses to homologous or heterologous allergen. Female BALB/c mice received two intratracheal aspiration (IA) exposures to Metarhizium anisopliae crude antigen (MACA) or Hank's buffered salt solution (HBSS) prior to breeding. Some mice also received three additional exposures during pregnancy. Control mothers did not receive treatment. Young adult offspring received three IA exposures to MACA, house dust mite extract (HDM) or HBSS. Offspring sensitized as young adults to either HDM or MACA developed an airway inflammatory response, including increased bronchoalveolar lavage fluid lactate dehydrogenase activity, total protein and total and differential cell counts compared to offspring exposed to HBSS. Increased airway responsiveness to methacholine was observed in pups treated with HDM but not with MACA. Maternal sensitization status (with or without gestational allergen exposure) had no effect on offspring response to either MACA or HDM. In conclusion, this study demonstrates that IA administration of MACA or HDM extract to young adult BALB/c mice induces the development of an inflammatory airway response. In contrast to previous reports, neither maternal sensitization nor gestational allergen exposure could be demonstrated to have a clear effect on offspring sensitization. This discrepancy may be a function of the respiratory sensitization and exposure protocol used in this study, which mimics natural sensitization more closely than do parenteral routes of exposure.

The transfer of maternal antigen-specific IgG regulates the development of allergic airway inflammation early in life in an FcRn-dependent manner

Asthma is a chronic inflammatory airway disease characterized by airway hyperreactivity, increased mucus production, and reversible airway contraction. Asthma is a complex genetic trait caused by environmental factors in genetically predisposed individuals. The transportation of maternal antigen-specific IgG via amniotic fluid, placenta and breast milk plays an important role in passive immunity. First, to examine whether maternal passive immunity by the transportation of antigen-specific IgG via FcRn regulates allergic airway inflammation, ovalbumin-immunized FcRn(+/-) female mice were bred with FcRn(-/-) male mice to evaluate the degree of ovalbumin-induced allergic airway inflammation of FcRn(-/-) offspring. Maternal passive immunity regulated allergic airway inflammation in an FcRn-dependent manner. Second, to examine the role of maternal antigen-specific IgG1 injection into mothers, we intravenously injected ovalbumin-specific IgG1 into wild-type or FcRn(+/-) mice immediately after they gave birth. The offspring were sensitized and challenged with ovalbumin. Antigen-specific IgG1 administered to lactating mice reduced allergic airway inflammation in their offspring in an FcRn-dependent manner. Last, to exclude the factor of maternal passive immunity other than ovalbumin-specific IgG1, we administered ovalbumin-specific IgG1 orally to offspring after birth. Oral administration of ovalbumin-specific IgG1 to offspring during the lactating period prevented the development of allergic airway inflammation in an FcRn-dependent manner. These data show that the transfer of maternal antigen-specific IgG regulates the development of allergic airway inflammation early in life in an FcRn-dependent manner.

Maternal allergen immunisation to prevent sensitisation in offspring: Th2-polarising adjuvants are more efficient than a Th1-polarising adjuvant in mice

Background

Allergy has been an increasing problem in several parts of the world. Prenatal exposure to allergen and microbial components may affect the development of allergies in childhood, as indicated by epidemiological and experimental studies. We investigated the capacity for allergic sensitisation in offspring after induction of a Th1- or a Th2-polarised immune response to the same allergen in mothers during pregnancy.

Results

During pregnancy, mice were immunised with ovalbumin (OVA) given with either one of the Th2-adjuvants pertussis toxin (PT) or Al(OH)₃ (aluminium hydroxide), or with the Th1 adjuvant CpG. Offspring were immunised with OVA in Al(OH)₃ as young adults. Serum and supernatants from ex vivo stimulated or non-stimulated spleen cells from mothers and offspring were analysed for OVA-specific antibodies and cytokines, respectively. Mothers immunised with OVA together with either Al(OH)₃ or PT had increased levels of OVA-specific IgE and IgG1 compared to naive mothers, whereas mothers immunised with OVA together with CpG had increased levels of OVA-specific IgG2a compared to naive mothers. In general the highest levels of IL-5, IL-10, and IFNγ were observed in spleen cells from mothers immunised with PT and OVA. Upon immunisation, offspring from mothers immunised with OVA and either PT or Al(OH)₃ showed reduced levels of OVA-specific IgE and IgG1 and increased levels of OVA-specific IgG2a antibodies compared to offspring from naive mothers. Maternal immunisation with CpG and OVA did not affect antibody responses in offspring.

Conclusion

Allergic sensitisation in the offspring was affected by the type of adjuvant used for immunisation of the mothers with the same allergen. Th2 polarisation of the immune response in the mothers was found to give reduced IgE levels upon sensitisation of the offspring, whereas no reduction was achieved with Th1 polarisation in the mothers.

Maternal peanut exposure during pregnancy and lactation reduces peanut allergy risk in offspring

BACKGROUND

Maternal allergy is believed to be a risk factor for peanut allergy (PNA) in children. However, there is no direct evidence of maternal transmission of PNA susceptibility, and it is unknown whether maternal peanut exposure affects the development of PNA in offspring.

OBJECTIVE

To investigate the influence of maternal PNA on offspring reactions to the first peanut exposure, and whether maternal low-dose peanut exposure during pregnancy and lactation influences these reactions and peanut sensitization in a murine model.

METHODS

Five-week-old offspring of PNA C3H/HeJ mothers (PNA-Ms) were challenged intragastrically with peanut (first exposure), and reactions were determined. In a subset of the experiment, PNA-Ms were fed a low dose of peanut (PNA-M/PN) or not fed peanut (PNA-M/none) during pregnancy and lactation. Their 5-week-old offspring were challenged intragastrically with peanut, and reactions were determined. In another subset of the experiment, offspring of PNA-M/PN or PNA-M/none were sensitized with peanut intragastrically for 6 weeks, and serum peanut-specific antibodies were determined.

RESULTS

PNA-M offspring exhibited anaphylactic reactions at first exposure to peanut that were associated with peanut-specific IgG(1) levels and prevented by a platelet activation factor antagonist. In a subset experiment, PNA-M/PN offspring showed significantly reduced first-exposure peanut reactions, increased IgG(2a), and reduced mitogen-stimulated splenocyte cytokine production compared with PNA-M/none offspring. In an additional experiment, PNA-M/PN offspring showed reduction of peanut-specific IgE to active peanut sensitization.

CONCLUSION

We show for the first time maternal transmission of susceptibility to first-exposure peanut reactions and active peanut sensitization. Low-dose peanut exposure during pregnancy and lactation reduced this risk.

Animal models of asthma

Animal models of asthma are a tool that allows studies to be conducted in the setting of an intact immune and respiratory system. These models have highlighted the importance of T-helper type 2 driven allergic responses in the progression of asthma and have been useful in the identification of potential drug targets for interventions involving allergic pathways. However, a number of drugs that have been shown to have some efficacy in animal models of asthma have shown little clinical benefit in human asthmatics. This may be due to a number of factors including the species of animal chosen and the methods used to induce an asthmatic phenotype in animals that do not normally develop a disease that could be characterized as asthma. The range of animal models available is vast, with the most popular models being rodents (inbred mice and rats) and guinea-pigs, which have the benefit of being easy to handle and being relatively cost effective compared with other models that are available. The recent advances in transgenic technology and the development of species-specific probes, particularly in mice, have allowed detailed mechanistic studies to be conducted. Despite these advances in technology, there are a number of issues with current animal models of asthma that must be recognized including the disparity in immunology and anatomy between these species and humans, the requirement for adjuvant during senitization in most models, the acute nature of the allergic response that is induced and the use of adult animals as the primary disease model. Some larger animal models using sheep and dogs have been developed that may address some of these issues but they also have different biology from humans in many ways and are extremely costly, with very few probes available for characterizing allergic responses in the airway in these species. As research in this area continues to expand, the relative merits and limitations of each model must be defined and understood in order to evaluate the information that is obtained from these models and to extrapolate these findings to humans so that effective drug therapies can be developed. Despite these issues, animal models have been, and will continue to be, vital in understanding the mechanisms that are involved in the development and progression of asthma.

Maternal transmission of resistance to development of allergic airway disease

Parental phenotype is known to influence the inheritance of atopic diseases, such as allergic asthma, with a maternal history being a more significant risk factor for progeny than paternal history. We hypothesized that recall Th1- or Th2-type immune responses during pregnancy would result in transfer of maternal factors that would differentially impact development of immune responsiveness in offspring. Following weaning, susceptibility and severity of allergic airway disease (a murine model of human asthma) was evaluated in progeny, disease being elicited by immunization with OVA-Al(OH)(3) and challenge with aerosolized OVA. We found that progeny of mothers with Th1-biased immunity to OVA subjected to recall aerosol challenge during pregnancy had reduced levels of Ag-specific IgE and airway eosinophilia compared with progeny of mothers with Th2-biased immunity to OVA or naive mothers. Interestingly, progeny of mothers with Th1-type immunity to a heterologous albumin, BSA, were not protected from developing OVA-induced allergic airway disease. These findings demonstrated that maternal transfer of protection from development of allergic airway disease to offspring in this model of maternal Th1-type immunity was Ag specific.

Maternal-fetal interaction: preconception immunization in mice prevents neonatal sensitization induced by allergen exposure during pregnancy and breastfeeding

Allergen exclusion measures during pregnancy and lactation have been given consideration in studies of primary allergy prevention but complete avoidance of mother/neonatal allergen exposure has proven to be a difficult procedure. To evaluate a strategy to prevent allergen sensitization in early life in mice, we first established a neonatal model with ovalbumin sensitization through maternal allergen exposure during pregnancy or breastfeeding. The modulatory potential of preconception immunization was investigated on the neonatal development of subsequent allergic responses to maternal allergen exposure. Herein, we demonstrate that immunized mothers exposed to antigen during pregnancy or breastfeeding underwent intense vertical transmission of antibodies, including immunoglobulin G (IgG) in complex with ovalbumin and IgG1 antibody with anaphylactic function. It was further shown that maternal immunization efficiently decreased the passage of free antigens through breastfeeding and inhibited the enhanced IgE antibody response after postnatal antigen exposure. In addition, antenatal immunization decreased the antigen-specific proliferative response of immunized neonates, in parallel with profound downmodulatory effects on both the activation and differentiation of T and B cells after a non-specific stimulus and cytokine production. These findings showed that early life sensitization, subsequent to maternal allergen exposure during both the prenatal and postnatal periods, could be avoided by preventive vaccination of the mother.

Can allergic diseases be prevented prenatally?

Allergic diseases continue to increase in prevalence, and now affect over a third of the population in many countries. There is evidence that the increase in such diseases has its origins in early life exposures. Pregnancy or early childhood may therefore be critical periods for preventing the onset of allergic disease, and prenatal interventions are an attractive possibility for a population-based preventive approach. Here we review the data suggesting that prenatal exposures are important in the development of allergic disease, and that interventions during this time might be effective in prevention. We find evidence from both animal and human studies that prenatal interventions can influence the future development of allergic disease. There are a number of mechanisms through which such interventions may act to prevent allergic sensitization. We conclude that prenatal interventions have the potential to reduce the burden of allergic disease, and merit continued investigation. Further research in this area may lead to significant public health initiatives.