Changes in allergy manifestations, sensitization and gut microbiota in Estonian children   A.LARIONOVA1, K.JULGE1,2, T.REBANE3 K.HEILMAN4, E.SEPP5, T.VOOR 1,2 1 Children' s Clinic of Tartu University Hospital, Tartu, Estonia 2 University of Tartu, Faculty of Medicine, Department of Pediatrics, Tartu, Estonia 3 United Laboratories of Tartu University Hospital, Tartu, Estonia 4 Tallinn Children’s Hospital, Tallinn, Estonia 5 University of Tartu, Faculty of Medicine, Department of Microbiology, Tartu, Estonia INTRODUCTION Allergic diseases have shown a great increase in industrialized countries (1). After regaining independence in 1991 Estonia has rapidly moved to industrialization and caught up the average European living standards (2). Following different birth cohorts it has become available to compare allergic sensitization and allergy manifestations in children born in early 90s compared to those born in late 90s. Using metagenomic analysis it is possible to evaluate gut microbiota in a more detailed way. Results CONCLUSIONS We did not confirm our hypothesis that allergic diseases in Estonia have increased over time. However the pattern of atopic sensitization has changed. Children born in early 90s were more sensitized to food whereas later born children to inhalant allergens. Sensitization to aeroallergens according to SPTs in group II might refer to the increase of allergic diseases in the future. Diversity of faecal microbiota has diminished and dominating phyla have changed over time, shifted from Firmicutes to Bacteroidetes. These two phyla constitute the majority of the dominant human gut microbiota (5). In murine model it has been shown that animals without allergic airway inflammation have gut microbiome enriched in members of the Firmicutes (6). Further investigation is needed to explore whether diminished bacterial diversity and less Firmicutes could lead to higher prevalence of allergy. As seen on Figure 1, the prevalence of atopic dermatitis (AD), bronchial asthma (BA) and allergic rhinitis (AR) do not differ significantly comparing two study groups. According to positive skin prick test (SPT), we found no statistical difference in atopic sensitization at the ages 6 mo, 1y and 2y. At the ages 5y and 10 years children born in 1997-1998 tended to have more positive skin test to house dust mite (HDM), dog and mugwort allergens (p=0.02 , p=0.03 and p=0.01, respectively) (Figure 2). However children born in early 90s had significantly more positive sIgE antibodies to cow’s milk during first two years of life and at the age of five they had higher prevalence of sIgE antibodies to egg, cow´s milk (CM), HDM and cat. Children born in 97/98 had more positive sIgE to egg at the age of 6 mo and HDM at age of 10 (Figure 3). The analysis of faecal specimen revealed that bacterial diversity did differ between two subset of children from group I and II based on Shannon diversity index (Figure 4). The taxonomic composition was different between these groups, being dominated by Firmicutes in group I and Bacteroidetes in group II (Figure 5). Whereas to compare allergic and non-allergic children within the group the microbiota at phylum level did not differ. AIM Our hypothesis: allergic diseases in Estonia are increasing over time and Estonian children become more sensitized to different allergens post Soviet Union times in 1990-s. The other aim: to compare the gut microbiota of children born in early and late 90s. ACKnowledgements The study was supported by Estonian Research Council grant No. 7418 Method Comparison of two different birth cohorts from 2 prospective allergy studies (3,4); Children born in Women’s Clinic of Tartu University Hospital Group I: 274 children born in 1993 - 1994 Group II: 111 children born in 1997 - 1998 Followed up to the age of 10 years Study plan: At 6 months (mo), 1 year (y), 2 y, 5 y, 10 y clinical examination skin prick test (SPT) allergenspecific immunoglobulin E (sIgE) antibodies in sera At 10 y subset of children (I group n=26, II group n=27) stool sample: microbiota composition by pyrosequencing technique (454 pyroseq. of the 16S rRNA gene) Statistical methods: Statistical package SAS version 9.2 Χ2 or Fisher’s exact and Wilcoxon tests were used References 1. Ring J. et al. Global Allergy Forum and Second Davos Declaration 2013 Allergy: Barriers to cure – challenges and actions to be taken. Allergy 2014;69 (8):978-982. 2. Laar M. The Estonian Economic Miracle. The Heritage Foundation Report. Backgrounder (no. 2060) 2007. 3. Julge K. Humoral immune responses to allergens in early childhood. Medical dissertation of Tartu University No. 41 and of Linköping University No. 558, 1998 Tartu University press; p 30-36. 4. Voor T. Microorganisms in infancy and development of allergy: comparison of Estonian and Swedish children. Medical dissertation of Tartu University No. 115, 2005 Tartu University press; p 27-33. 5. Arumugam M. et al. Enterotypes of the human gut microbiome. Nature 2011, 473 (7346); 174-180. 6. Fujimura KE. et al. House dust exposure mediates gut microbiome Lactobacillus enrichment and airway immune defense against allergens and virus infection. Proc Natl Acad Sci USA. 2014, 14;111(2):805-10. Figure 1. Prevalence of allergic diseases Figure 2. Prevalence of positive skin prick tests Figure 3. Prevalence of IgE antibodies CONTACT INFORMATION Children’s Clinic of Tartu University Hospital, Lunini 6, Tartu, Estonia e-mail: anneli.larionova@kliinikum.ee Figure 4. Distribution of Shannon diversity index Figure 5. Bacterial phyla in group I and II