Allergy Immunity And Tolerance In Early Childhood

Allergy, Immunity and Tolerance in Early Childhood: The First Steps of the Atopic March provides valuable insights on the atopic diseases, including asthma, allergic rhinitis, atopic dermatitis, and food allergies, which have developed into major health problems in most parts of the world. As the natural history of these chronic diseases has been extensively studied, including their major genetic, environmental, and lifestyle determinants and potential protective factors, the book presents tactics on how pediatric allergists can provide early intervention. In addition, the book unites key, global experts in the field who summarize their collective, and current, knowledge of the early stage of the "Atopic March", along with novel ideas for potential options of prevention. Summarizes the current knowledge of the epidemiological, genetic, and cellular basis of allergic diseases Ideal reference for the study of allergies in young children, atopic dermatitis, allergic rhinitis, childhood asthma, and food allergies Provides landmark findings in the field of immunology and allergy development Fulfills the need for a book that focuses on primary and secondary allergy prevention, especially during the first years of life Unites key, global experts in the field who summarize their collective, and current, knowledge, along with novel ideas for potential options of prevention

During the last two decades the increase in allergic diseases in children, such as atopic dermatitis and asthma, has been drastic. However, this is not true for the entire world: the incidence of allergies in children has risen only in developed countries. The observation of this socio-geographic discrepancy has led to careful study of the environmental differences that exist between the diverse settings in which children are born and has resulted in the so-called 'hygiene hypothesis': the 'sterility' of modern hospitals and birth places in the developed world might lead to a lack of microbial stimulation required for the development of a balanced mucosal immune response, including expansion of T-helper (Th) cell subsets that can mediate immune responses. Therefore, this workshop was held to consider in depth the environmental factors that influence the changing pattern of worldwide childhood allergy. This publication is a valuable source of knowledge and update for nutritionists, pediatricians, immunologists, microbiologists, as well as professionals concerned with preventive medicine.

The prevalence of allergic diseases has in the past century increased among children in affluent societies. Underlying causes are incompletely disentangled, but decreased diversity in environmental and microbial exposures could drive allergy development. Allergic individuals possess imbalanced immune responses, skewed in favour of Th2 cells along with lesser Th1 and Treg responses. As allergy development early in life increases the risk of developing further allergic manifestations later, early prevention is key. Thus, interventions in pregnancy, early life and childhood may modulate immunity towards tolerance, although underpinnings of immune maturation and modulation in allergy prevention throughout childhood are not entirely understood. In this thesis, these questions are addressed in children with a high propensity of developing allergic disease or who already have manifested allergies. Chemokines are crucial for immune cell recruitment to the allergic reaction site, and associate with allergy development in childhood. In Paper I, circulating levels of the allergy-related chemokines CCL17, CCL18, CCL22, CXCL10 and CXCL11 were studied in the natural course of allergic disease. Elevated levels of the Th2/Treg-regulated chemokine CCL18 in infancy and childhood associated with development of asthma and/or sensitisation. Moreover, this finding conferred higher odds of developing asthma and sensitisation from early school age until adolescence. Additionally, increased levels of the Th1-associated chemokines CXCL10 after birth, and decreased levels of CXCL11 at birth, preceded asthma development later in life. Hence, Paper I showed that circulating chemokine levels in different ways precede allergy development. Epigenetic modifications, such as DNA methylation, comprise a link between the genetic setup and environmental exposures, and regulate processes such as Th cell differentiation. Perinatal treatment with Lactobacillus reuteri and ?-3 fatty acids prevent development of some IgE-mediated manifestations. However, the drivers of the immunostimulating and pro-resolving effects of these treatments are sparsely examined. In Papers II and III, epigenome-wide DNA methylation patterns in CD4+ cells upon pre-and postnatal L. reuteri supplementation alone or in combination with ?-3 fatty acids were studied. In Paper II, the greatest epigenome wide differential methylation was evident at birth, mainly directed towards hypomethylation, indicating transcriptional availability of affected genes. Network analyses revealed several immune related pathways, and a relationship of differentially methylated genes to allergy development. Thus, prenatal L. reuteri treatment seemingly poises Th cells towards immune activation at birth, possibly influencing immune maturation as well as allergy development in the child. In Paper III, epigenome-wide DNA methylation patterns were surveyed at birth. In this on-going trial, mothers are treated during the latter half of pregnancy with a combination of L. reuteri and ?-3 fatty acids. Four different treatment groups were studied, and the largest differential methylation was seen in the double active treatment group. In contrast to Paper II, most CpGs and genes were hypermethylated, indicating repressed gene transcription. In line with Paper II, network analyses showed that T cell and immune mediated pathways were affected by treatment, and synergistic effects of the double treatment were indicated. Taken together, prenatal treatment with L. reuteri and/or ?-3 fatty acids altered the epigenome to different extents at birth, mainly towards hypermethylation, and often affected immune related pathways. Immunomodulatory effects of sublingual immunotherapy in children and adolescents are scarcely investigated. In Paper IV, circulating and salivary immune mediators were investigated in timothy grass-pollen allergic children treated with sublingual immunotherapy. Actively treated children had elevated levels of timothy grass pollen-specific IgA antibodies in saliva, along with increased circulating levels of the Th1-associated chemokines CXCL10 and CXCL11, both after treatment ending and two years later. Taken together, sublingual immunotherapy modulates local and peripheral immune responses in children with timothy grass pollen-induced allergy, by augmenting Th1-responses, lessening Th2-responses and inducing immunomodulatory responses, suggesting induction of tolerance, also partly in the long-term. Altogether, the studies in this thesis have shown altered immune regulation in children developing allergies. Moreover, immunomodulatory effects of prenatal treatment with probiotics and ?-3 fatty acids, and sublingual immunotherapy in children with grass pollen-induced allergic disease, were revealed. DNA methylation patterns and immunologic mediators in blood and saliva could potentially serve as appropriate biomarkers for allergic disease. Long term health benefits can be reached by intervening early in life, and further knowledge about the mechanisms behind this could promote the prevention of allergic diseases and hence improve the quality of life for children and adolescents. Förekomsten av allergiska sjukdomar, som böjveckseksem, hösnuva och astma, har under det senaste århundradet ökat markant bland barn i industrialiserade samhällen. De bakomliggande orsakerna är inte helt klarlagda, men samhälleliga förändringar har minskat vår mångfaldiga exponering för bakterier, virus och parasiter. Detta skulle kunna ligga till grund för immunförsvarets felaktiga reaktion mot egentligen ofarliga ämnen som ses vid allergier. Hos allergiska individer är immunförsvaret obalanserat, med en relativ övervikt av det så kallade Thjälpar- 2 (Th2)-svaret gentemot Th1- och det regulatoriska T-cells (Treg)-svaret. Allergiska sjukdomar utvecklas ofta tidigt i livet, vilket ökar risken för att utveckla vidare allergier senare i livet. Därför är det viktigt att motverka den allergiska marschens framfart tidigt genom förebyggande behandlingar. Ett tillvägagångsätt är att påbörja behandling under graviditeten och tidiga barndomen hos barn med hög risk för att bli allergiska, då grunden för immunsystemet läggs redan under fosterlivet. För redan utvecklade allergier är det tänkbart att omforma dessa immunsvar med immunterapi, som kan minska symptom av befintliga allergier samtidigt som det är möjligt att motverka utvecklingen av senare allergier. Det är dock inte helt klarlagt hur immunutmognaden under barndomen är reglerad, eller hur dessa typer av behandlingar skulle kunna påverka allergiutveckling under den perioden. I denna avhandling undersöks immunutmognad vid allergiutveckling hos barn, och möjliga immunmodulerande förebyggande behandlingar hos barn med genetisk benägenhet att bli allergiska eller som redan utvecklat allergisk sjukdom. För att celler ska rekryteras till platsen för en allergisk reaktion krävs bland annat s.k. kemokiner. I det första arbetet undersöktes dessa lockelseämnen, då våra tidigare studier visat att nivåerna av vissa kemokiner vid födseln förutspår utvecklingen av allergi hos barn. De allergirelaterade kemokinerna CCL17, CCL18, CCL22, CXCL10 och CXCL11 analyserades i blodprover vid födseln, 1 och 8 års ålder hos barn från en populationsbaserad observationsstudie. Förhöjda nivåer av CCL18, ett kemokin under reglering av både Th2- och Treg-svar, uppmättes vid 1 och/eller 8 års ålder hos barn som hade astma (särskilt svår astma) och/eller var sensibiliserade. De ökade nivåerna associerade också till högre odds för utveckling av astma från tidig skolålder upp till övre tonåren, med liknande resultat för sensibilisering. Även ökade nivåer av de Th1-associerade kemokinerna CXCL10 efter födseln och minskade nivåer av CXCL11 vid födseln föregick utvecklingen av astma senare i livet. Det första arbetet visade alltså på att cirkulerande kemokiner på olika vis föregår utvecklingen av allergier hos barn och ungdomar. Som länk mellan arv och miljö står s.k. epigenetiska modifieringar, vilka reglerar genaktiviteten utan att förändra den genetiska koden i arvsmassan. Till dessa modifieringar räknas DNAmetylering, en process som bl.a. styr utmognad av de allergirelaterade T-hjälparcellerna. Vi har i tidigare separata studier med den probiotiska stammen Lactobacillus reuteri och omega-3- behandling visat förebyggande av vissa IgE-medierade allergier. Vad som föranleder de immunstimulerande och immunmodulerande effekterna av behandlingarna är dock otillräckligt undersökt. I det andra och tredje arbetet undersöktes hur L. reuteri separat eller i kombination med omega-3-fettsyror påverkar DNA-metyleringsmönster i CD4+ Th-celler hos barn som behandlats före och efter födseln. I det andra arbetet undersöktes DNA-metyleringsmönster både lokalt och i hela genomet vid födseln, ett och två års ålder. Behandling med L. reuteri förändrade DNA-metyleringsmönster i allergirelaterade T-hjälparceller mest vid födseln mot s.k. hypometylering, vilket pekar på ökad tillgänglighet av generna för proteinuttryck. Vidare nätverksanalyser visade att flera immunrelaterade processer påverkades av behandlingen. Därtill var generna från nätverket till stor del associerade med allergiutveckling. Maternell behandling med L. reuteri under den sista graviditetsmånaden tycks alltså förändra DNA-metyleringsmönster i T-hjälparceller hos fostret mot ökad immunaktivering vid födseln, vilket i sin tur skulle kunna påverka både immunutmognad och allergiutveckling hos barnet. I likhet med det andra arbetet undersöktes i det tredje arbetet DNA-metyleringsmönster i hela epigenomet, fast endast vid födseln. I denna pågående studie behandlas mödrarna under den andra halvan av graviditeten med en kombination av L. reuteri och omega-3-fettsyror. Fyra olika behandlingsgrupper undersöktes och den största förändringen i DNA-metylering återfanns i den kombinerade aktiva behandlingsgruppen. I motsats till det andra arbetet var dock de flesta CpG positionerna och generna hypermetylerade, vilket tyder på att genernas tillgänglighet för proteinuttryck hämmas. I linje med det andra arbetet framkom T-cells- och immunrelaterade signalvägar i nätverksanalyser på dessa gener, och det fanns indikationer på synergistiska effekter mellan behandlingarna. Det tredje arbetet visade att behandling med L. reuteri och/eller omega- 3-fettsyror under senare delen av graviditeten förändrar T-hjälparcellernas epigenom i olika grad främst mot hypermetylering, och ofta påverkar immunrelaterade signalvägar. Relevansen av dessa fynd kommer i framtida studier att undersökas på proteinnivå och i relation till allergiutveckling. Med allergenspecifik immunterapi är det möjligt att modulera immunsvaret hos allergiska individer mot ett tolerant immunsvar, men effekter av sublingual immunterapi på immunförsvaret hos barn och ungdomar är knapphändigt undersökta. I det fjärde arbetet undersöktes olika immunologiska mediatorer i blod och saliv hos barn med gräspollenallergi, som deltagit i en studie med sublingual immunterapi. Nivåerna av allergirelaterade cytokiner och kemokiner undersöktes i blodprover från inklusionstillfället, efter tre år med behandling samt två år efter avslutad behandling i plasmaprov och allergenstimulerade blodceller. Dessutom mättes total-IgA, sekretoriskt IgA och gräspollenspecifikt IgA i saliv vid samma tillfällen. Barn som fått aktiv behandling hade högre nivåer av gräspollenspecifika IgA-antikroppar i saliv både när behandlingen avslutades och två år efter. Därtill ökade nivåerna av de Th1-associerade kemokinerna CXCL10 och CXCL11 i blodet vid samma tidpunkter. Sammantaget visade resultaten från det fjärde arbetet att behandlingen med sublingual immunterapi hos barn med gräspollenallergi modulerar immunsvaret både lokalt och i cirkulationen genom att öka Th1- svar, minska Th2-svar och inducera immunreglerande svar, vilket indikerar att tolerans har utvecklats hos dessa barn, delvis även på lång sikt. Sammanfattningsvis har studierna i denna avhandling visat på förändrad immunreglering hos barn som utvecklar allergi. Dessutom påvisades immunmodulerande effekter av prenatal behandling med probiotika och omega-3-fettsyror samt av sublingual immunterapi hos barn med gräspollenallergi. DNA-metyleringsmönster och immunologiska mediatorer i blod och saliv skulle kunna fungera som lämpliga biomarkörer för allergisk sjukdom, vilket är ett viktig led i att kunna förutsäga allergiutveckling och förbättra den kliniska behandlingen av allergier bland barn och ungdomar. Långsiktiga hälsofördelar kan uppnås genom att ingripa tidigt i livet, och vidare kunskap om mekanismerna bakom detta skulle kunna främja förebyggandet av allergiska sjukdomar och således kunna förbättra livskvaliteten för barn och ungdomar.

Most indigenous microbes occur in the intestinal tract, and their interactions with the host are largely unknown. Current understanding of host-microbe interactions links early microbial contact to the origin of disease, a theory that has its roots in the hygiene hypothesis. Modern life style appears to deprive the infant of conditions that provide adequate anti-inflammatory or tolerogenic stimuli upon antigen encounter. Thus, maturational signals from the environment and the diet are insufficient to adequately shape the immune system. This publication deals with the relationship between the gut microbiota as well as altered pattern of early microbial contact and the origin of human disease. New aspects of the original hygiene hypothesis are discussed in relation to disorders spanning from allergy and autoimmunity to obesity.The results presented suggest that all these disorders may be linked to aberrant antigen absorption and immune responses associated with dysfunction of mucosal defense. Researchers, clinicians and students interested in the interaction of the host with indigenous gut bacteria and the consequences for human health will find this publication of utmost interest.

Considerable advances have been made in science in order to understand the varied mixture of bioactive components in human milk. The 94th Nestlé Nutrition Institute Workshop was designed to provide a comprehensive overview of the latest findings in human milk research and its potential to modulate mucosal immunity, the microbiome, and its impact on the neonate. The publication provides a balanced state-of-the-art update on the current knowledge about milk, mucosal immunity, and the microbiome as well as their impact on breastfeeding in mammalian neonates. The first part reviews data on the immunology of milk and lactation from a historical perspective to the latest scientific findings. The second part discusses the microbiology of human milk and lactation in detail, with a focus on premature infants and necrotizing enterocolitis. And finally, in the third part, light is shed on the protective factors in human milk and their role in influencing the neonate’s immune system. Important new insights will provide great scientific support for all people seeking a deeper understanding of human milk and its immunological properties and will enlarge the knowledge of those who have already specialized in human milk research.

Over the past 20 years, public concerns have grown in response to the apparent rising prevalence of food allergy and related atopic conditions, such as eczema. Although evidence on the true prevalence of food allergy is complicated by insufficient or inconsistent data and studies with variable methodologies, many health care experts who care for patients agree that a real increase in food allergy has occurred and that it is unlikely to be due simply to an increase in awareness and better tools for diagnosis. Many stakeholders are concerned about these increases, including the general public, policy makers, regulatory agencies, the food industry, scientists, clinicians, and especially families of children and young people suffering from food allergy. At the present time, however, despite a mounting body of data on the prevalence, health consequences, and associated costs of food allergy, this chronic disease has not garnered the level of societal attention that it warrants. Moreover, for patients and families at risk, recommendations and guidelines have not been clear about preventing exposure or the onset of reactions or for managing this disease. Finding a Path to Safety in Food Allergy examines critical issues related to food allergy, including the prevalence and severity of food allergy and its impact on affected individuals, families, and communities; and current understanding of food allergy as a disease, and in diagnostics, treatments, prevention, and public policy. This report seeks to: clarify the nature of the disease, its causes, and its current management; highlight gaps in knowledge; encourage the implementation of management tools at many levels and among many stakeholders; and delineate a roadmap to safety for those who have, or are at risk of developing, food allergy, as well as for others in society who are responsible for public health.