Microbiota and A llergy

1. Microbiota and Allergy Rose Kamenwa Department of Pediatrics and Child Health Aga Khan University Hospital, Nairobi KPA, 10TH April, 2019 Whitesands Hotel, Mombasa

2. Outline • Childhood allergy on the rise • Link to microbiome • Hygiene hypothesis versus Microbiome hypothesis • Microbiota and Immune system

3. The Increase in Childhood Allergy is Paralleled by Increases in other Maladies and Practices in Western Societies in the Last 60 Years Changing Practices Increase in Caesarian deliveries Use of antibiotics Decrease in breast-feeding or duration of breast-feeding Use of antibiotic growth promoters in food animal production Urbanization Maternal antibiotic use during pregnancy The Increase in Disease temporally parallels these changing practices and in the rate of antibiotic prescriptions [Obesity, IBD, Autism, Gastrointestinal reflux disease (GERD) childhood & adolescent allergy and asthma] Red =Relative Prescriptions Green= Asthma Blue= Autism

4. Studies Implicate Antibiotics, an Unhealthy Microbiome and the failure of Tregs Mouse studies correlate IBD and food allergy with an unhealthy microbiome: GF mice cannot develop oral tolerance until colonized with Clostridium Non-tolerant mice have very few Tregs Oral tolerance can be transferred to GF mice with the microbiome from conventionally-reared mice Tolerance is associated with production of SCFA that appear necessary for Treg development and healthy tight junctions Mice lacking the TLR receptor for endotoxin/ LPS are highly susceptible to food allergy Antibiotics contribute since mice given a broad-spectrum antibiotic to reduce/eliminate their microbiome: 1.Develop elevated levels of food allergy compared to controls 2.Show poor development of Tregs 3. Develop airway inflammation and hyperactive airways when aerosol challenged with house dust The microbiome of allergic children shows: 1. An over-representation of Enterobacteria (Proteobacteria) and a lower proportion of Bacteriodetes 2. The feces of allergic children contain lower levels of SCFA produced by Bacteriodes 3. Resolution of food allergy is associated with an enrichment of Firmicutes, e.g. Clostridium Megan Scudellari, News Feature: Cleaning up the hygiene hypothesis Proc Natl AcadSci U S A. 2017 Feb 14; 114(7): 1433–1436.

5. Studies in humans which support Hygiene hypothesis • Allergy and asthma lower in European farm children • Larger families with greater exposure to infectious disease have less allergy • Early helminthes or H. pylori infections associated with less allergy • Farm children raised with animals have less allergy • The Amish- Hutterite experiment Asthma and allergy is 4-6 fold lower in Amish children Dust from Amish households suppressed airway hypersensitivity when transferred to mice Growing up on Amish farms protects children against asthma. New England Journal of Medicine

6. Hygiene hypothesis is being replaced by “Microbiome Hypothesis” • 14 of 17 studies supporting the hygiene hypothesis show a link between the gut microbiota and atopy • Allergic children have a lower microbiome diversity before they develop allergy • Allergic children have higher levels of Enterococcus, Clostridia and lower levels of Lactobacilli Linda Brookes, Laurence E. Cheng. The Hygiene Hypothesis -- Redefine, Rename, or Just Clean It Up?, Medscape Gastroenterology, April 06, 2015 Vatanen T, et al., DIABIMMUNE Study Group. Variation in microbiome LPS immunogenicity contributes to autoimmunity in humans. 2016, Cell 165(4):842–853

7. “Microbiome Hypothesis”……. “We know an awful lot now about why our immune system’s regulation is not in terribly good shape, and it’s got absolutely nothing to do with hygiene,” says Graham Rook, an emeritus professor of medical microbiology at University College London. Today, epidemiological, experimental, and molecular evidence support a different hypothesis: Early exposure to a diverse range of “friendly” microbes—not infectious pathogens—is necessary to train the human immune system to react appropriately to stimuli Bloomfield SF, et al.(2016) Time to abandon the hygiene hypothesis: New perspectives on allergic disease, the human microbiome, infectious disease prevention and the role of targeted hygiene. Perspect Public Health 136(4):213–224

8. Time to abandon Hygiene Hypothesis? • Rook proposed that exposure to nonpathogenic microbes activates a variety of immune processes, including Treg cells, to regulate the immune system appropriately. So, with fewer old friends to learn from, our immune systems grow up to be trigger-happy. • Rook likens the immune system to a computer: It has software, but it needs data—in the form of exposure to a diverse set of microbes—to train it to identify threats appropriately. • “It’s not about just learning what to attack, but learning what to tolerate,” says Bloomfield. “The problem comes when our immune system meets an allergen like pollen or peanuts and doesn’t know that is harmless.” Megan Scudellari, News Feature: Cleaning up the hygiene hypothesis Proc Natl AcadSci U S A. 2017 Feb 14; 114(7): 1433–1436.

9. Interaction between Gut microbiota and immune system • Gut microbiota metabolites and dietary factors constitute the main antigen load of the GIT • Metabolic products such as short chain fatty acid stimulate - macrophages and dendritic cells - T regulatory cells are activated • Follicular T cells activate B cells inducing the production of IgA antibodies

10. What causes dysbiosis? Dysbiosis induce qualitative and quantitative changes in the microbiota that directly affect immunological mechanisms leading to allergic diseases

11. Literature Review Microbiota and Immunity Clinical & Experimental AllergyVolume 38, Issue 4, pages 629-633, 22 JUL 2007 DOI: 10.1111/j.1365-2222.2007.02780.xhttp://onlinelibrary.wiley.com/doi/10.1111/j.1365-2222.2007.02780.x/full#f1

12. Asthmatics have an altered lung microbiota

13. Asthma and Microbes • early microbial colonization is required in order to control the invariant natural killer T cells in lung, which are capable of producing IL-4 and IL-13 and contribute to TH2-mediated asthma. • Infants with lower abundance of Bifidobacterium, Akkermansia and Faecalibacterium incurred a higher relative risk of asthma by promoting adaptive immune dysfunctions, featured by increased proportion of IL-4+ TH2 cells and reduced percentage of CD25+ Foxp3+ Regulatory CD4+ T (Treg) cells. • higher risk of asthma is associated with the lower abundance of genera such as Faecalibacterium, Lachnospira, Veillonella and Rothia in infants despite of similar abundance of dominant Bifidobacterium. Furthermore, • Supplementing with microbes abundant in healthy controls into GF mice previously colonized with fecal microbiota from infants of high risk for asthma reduced severity of allergic airway inflammation. It was also reported that • Bifidobacteriumis decreased in adult asthma patients • It seems that Faecalibacterium, especially subspecies producing SCFAs, and Bifidobacterium provides benefi-cial effect for preventing asthma

14. Skin microbiome and AD • Skin microbiomes can influence the skin barrier by controlling ecological factors, such as humidity, temperature, pH, and lipid content • Compositional change in the skin microbiome influences the development and degree of symptoms of AD via allergic inflammation • Dysbiosisof the skin commensal microbiome may contribute to the disruption of immune homeostasis in the skin and promote the development of skin diseases, such as AD • Skin microbiome plays a role in the initiation of AD could help reduce its development SeiteS, Bieber T. Barrier function and microbioticdysbiosis in atopic dermatitis. ClinCosmetInvestigDermatol 2015;8:479–483 Kennedy EA, Connolly J, Hourihane JO, Fallon PG, McLean WH, Murray D, et al. Skin microbiome before development of atopic dermatitis: early colonization with commensal staphylococci at 2 months is associated with a lower risk of atopic dermatitis at 1 year. J Allergy ClinImmunol 2017;139:166–172 Grice EA, Kong HH, Conlan S, Deming CB, Davis J, Young AC, et al. Topographical and temporal diversity of the human skin microbiome. Science 2009;324:1190–1192

16. The Influence of the Microbiome on Allergic Sensitization to FoodCatherine H. Plunkett and Cathryn R. NaglerJ Immunol January 15, 2017, 198 (2) 581-589 • Induction of tolerance to food and bacterial Ags in the intestine: food Ag is taken up by DCs in the small intestine that migrate to the proximal mLN. TGF-β and RA, produced by LN stromal cells and DCs respectively, induce the differentiation of naive T cells to food Ag–specific Tregs. RA and TGF-β also induce upregulation of gut-homing receptors on these newly differentiated Tregs to recruit them back to the lamina propria. TLR signaling by bacterial products induces the production of IL-10 by CX3CR1 macrophages resident in the lamina propria, supporting Treg expansion in this site. Bacterial products are also taken up by colonic DCs that migrate to the distal mLN and caudal LN to induce differentiation of bacterial-specific Tregs. Although predominant in the colon, bTregs also migrate to the small intestine where they release IL-10 to maintain the tolerogenic immune environment. Fermentation of dietary fiber to SCFAs may enhance RA production by DCs and promote Treg differentiation. TLR signaling by bacterial products, such as LPS, induces a tolerogenic phenotype in colonic and small intestinal DCs that promotes differentiation of Tregs.

17. Conclusion • Better understanding of how microbes influence allergic disease will have potential for effective methods of prevention and treatment by either restoring altered microbiome functionality or boosting immunological system in specific immunotherapy • This field is still relatively new and we expect many key findings to be made in the next few years. Detailed prospective, randomized, placebo-controlled studies will be essential for this purpose

18. Thank you