Speaker: Ruby Pawankar

The Asia Pacific Association of Allergy, Asthma and Clinical Immunology (APAAACI) was established in 1989, represents over 18 countries, and is present in 59 countries. It comprises national member societies and individual members that aim to enhance excellence in science, clinical practice, education, and training in allergy, asthma, and clinical immunology. APAAACI activities include publishing white papers, guidelines, and manifestos; conducting research collaborations, patient documentation, masterclasses, webinars, online modules, case-based studies, training schools, and surveys; and further collaborating with several organizations such as YACI, WHO, American Academy etc. Furthermore, it also offers fellowships to young individuals and recognizes centres of excellence. The organization also has a published journal and conducts theme-based symposia, outreach programs and training through an online platform.

Environmental factors such as lifestyle risk factors are crucial as they directly influence the exposome, which subsequently dictates the disease factors. Factors influencing allergic disease include genetics, pollutants (outdoor and indoor), biodiversity loss, urbanization, industrialization, Western diets, reduced vitamin D levels, and disturbances in microbiota composition and diversity. Research has demonstrated that the body harbours more microbiota than cells, with diversity differing among organs and extraction methods. The speaker further elaborated on data from Microbiome and Allergy/Asthma-2023, emphasizing key findings such as dysbiosis in both qualitative and quantitative forms, depleted diversity preceding the onset of allergies and asthma, direct and indirect evidence suggesting the support for a cause-effect relationship, inconsistent findings regarding affected microbial species, elusive mechanisms of host-microbe induction, and the potential existence of a life window for future exploration, including probiotics, prebiotics, and symbiotics. The session further outlined the impact of microbial diversity on health, noting historical trends of robust vertical and horizontal transmission leading to a balanced ancestral microbiota and mature immune responses. However, modern trends indicate decreased transmission (both vertical and horizontal) and maintenance, resulting in depleted microbiota diversity, altered adaptive immune maturation, and increased autoimmune and allergic diseases. Factors such as delivery method, including vaginal and C-section, influence early-life microbiota composition and diversity, with C-section significantly altering the abundance of diverse bacterial taxa over time, especially in the first year of life. Additionally, antibiotic exposure during early childhood, often administered for fever or illness, decreases microbiota maturation during the first six to twelve months of life. High dietary fat in animal experiments demonstrated increased susceptibility to food allergies. However, microbiota transfer from high-fat diet-fed animals to germ-free recipients did not induce obesity but heightened food allergy susceptibility due to reduced intestinal diversity.

The session further discussed data on the preterm gut microbiota's impact on allergic diseases, highlighting delays in bifidobacterium-dominated intestinal flora in preterm infants, correlating with lower birth weight and gestational age. Preterm infants with lower bifidobacterium and bacterial abundance showed reduced birth weight and gestational age and predominantly affected infants with both conditions than a single condition. Bifidobacterium and Bacteroides were less ingrafted in preterm infants compared to full-term infants, thus indicating early microbial diversity's impact on health, with further studies suggesting maternal factors influencing infant microbiota. At one-month-old, full-term infants had 8.4 operational taxonomic units (OTUs) compared to 4.8 OTUs in preterm infants. The abundance of the bacterial types in preterm infants correlated positively with gestational age and birth weight; however, specific bacteria were not detected, and there was no significant difference in complication or prevalence of allergic diseases until 18 months. Subsequent follow-up at 7 years of age showed a tendency to develop allergic diseases. Intestinal engraftment of Bifidobacterium and Bacteroides was associated with immaturity, and further, to achieve an increase in diversity, engraftment of Bacteroides may be performed.

Postnatal factors contributing to allergy and asthma development include early viral infections, antibiotic use, western lifestyle, small family size, absence of older siblings, passive smoking, high-fat consumption, obesity, western diet, indoor pollution, low-dose allergen exposure, and delayed introduction of foods. Different types of food allergies may exhibit unique microbial signatures, suggesting the need for multinational studies to validate and intervene with probiotics, prebiotics, or symbiotics. Factors like delivery mode, antibiotic use, and exposure to synthetic chemicals impact gut microbiota and lead to allergy development. Specific gut microbiome signatures associated with pro-inflammatory functions, such as butyrate & propionate-producing bacteria, are downregulated in paediatric food and respiratory allergies, particularly in cases where both coexist. The maturation of the gut microbiome in infancy contributes to protective effects against childhood asthma, with studies suggesting that the estimated 12-month microbiome age was associated with previous farm exposure and can provide potential asthma protection through metabolites, supporting the gut-lung axis concept. The speaker further discussed the relationship between dysbiosis and decreased levels of butyrate-producing bacteria is linked to the onset of allergic diseases, suggesting that various factors, including maternal microbiome, mode of delivery, drugs, and nutrition, resulting in downregulation of regulatory and tolerogenic cytokines and cells, and further, leading to an excessive immune response. Children with food allergies show lower levels of butyric acid-producing bacteria (BAPB) compared to healthy controls. The session further focused on the gut-brain axis, with changes in gut microbial composition associated with control over food intake, obesity, and irritable bowel syndrome. Pathways responsible for gut-brain axis interactions include the vagus nerve, enteric nervous system, immune system, and tryptophan metabolism, which involve microbial metabolites such as short-chain fatty acids. Factors such as diet and environmental stresses impact human health and contribute to early ageing, with childhood and maternal nutrition and environmental conditions programming future immune diseases.

The speaker addressed the substantial increase in allergies and non-communicable diseases in recent years, which can be attributed to various factors such as environmental factors, reduced biodiversity, the Western lifestyle, and the diet change- epithelial barrier hypothesis that adversely affects immune health. Dysbiosis in the gut microbiota, influenced by factors like caesarean delivery, antibiotic use before 3 years of age, and early environmental exposures, increases the risk of allergic and immune diseases. Specific microbial signatures are associated with the risk of allergies and immune tolerance, with dysbiosis characterized by reduced BAPB related to allergic disease onset. 

European Academy of Allergy and Clinical Immunology (EAACI), 2024 31st May-3rd June, Valencia