Bibliographic updates

The Monthly Choice
January 2015
Claude Molina, Jacques Gayraud

The Microbiota/Microbiome in Allergic diseases and Asthma
1 - The Gut Microbiota
2 - The human microbiome in immune cell development    
3 - The microbiome in Asthma
4 - Skin Microbiome and Atopic diseases
5 - Modulation of Gut Microbiota in Prevention and Treatment of Allergy

1.    The Gut Microbiota
P. Debré et J.Y Le Gall : Rapport à l’Académie Nationale de Médecine 2014 (sous presse)
C.E.West et coll.
The gut microbiota and inflammatory non communicable diseases J.A.C.I 2015 January 135 1 3-13  

Theme: Immunology
Key words: Microbiota – Microbiome.

Accelerating development of molecular biology methods and next generation sequencing associated with bioinformatics gave a detailed description of both the microbiota, without requiring growth or isolation and its genome: the microbiome. It appears that an adult harbors as many 100 trillion resident microbes and the microbiome contains 150 fold more genes than the host genome. All the methods for investigation on the role of this gut microbiota in immune development are well documented. The changes in microbial composition and diversity are implicated in large series of non communicable diseases including allergic diseases and asthma. Studies in animal models, establishment of gut microbiota in infants, environmental factors (mode of delivery, nutritional patterns, antibiotics, climate) account for dramatic increase in allergic manifestations. Modulation of this microbiota for the treatment and prevention of these diseases is well exposed in these two articles.

2.    The human microbiome in immune cell development    
N.H.Salzman 18 September 2014 Annals of Allergy Asthma Immun. 1-5        

Theme: Immunology
Key words: Microbiome – Immunity – dysbiosis – Hygiene hypothesis.

The author analyzes the post natal immune development in animals (germ-free) and in neonates, with impact on innate then adaptive immunity and the respective role of B cells and IgA, Regulatory T cells (Treg) TH 17. Immune response is carried out at local and distant sites. Disruption of homeostasis (dysbiosis) results in inflammatory processes such allergy and asthma. The hygiene hypothesis which is now discussed, suggests that the lack of environmental microbial exposure causes immune dysregulation and increases Th2 response. Gut Microbiota is an essential force in immune development.

3.    The microbiome in Asthma
Y.J.Huang and Homer.A.Boushey JACI 2015 135 25-30                          

Theme: Immunology - Asthma
Key words: Microbiome – Asthma.

Although most work were initially focused on gut microbiota, interest has expanded to include study of relationships between the airway microbiome and asthma with its phenotypes. The authors provide their perspective on differences in the airway microbiome between asthmatic and healthy subjects as well as relationships between environmental, gut microbiota, immune function and asthma development. They underline approaches involving directed manipulation of the gut and airway microbiomes for the treatment and prevention of allergic asthma.

4.    Skin Microbiome and Atopic diseases
A.Salava et A.Lauerma : Role of the skin microbiome in atopic dermatatis Clin.and Translat. Allergy 2014 4 33doi10.                                    
L.Nylund : The severity of atopic disease inversely correlates with intestinal microbiota diversity Allergy 2014 Nov 21 ahead of print         
N.Fyrhrquist et al   Acinetobacter species in the skin microbiota protects again allergic sensitization and inflammation JACI 2014 134 1301-9  

Theme: Immunology – Skin allergy
Key words: Skin Microbiome – Atopy – Dysbiosis.

Molecular genetics have dramatically changed our vision of the skin microbiome and its role in atopic dermatitis (AD). Additionally to the known dysfunction in barrier of the skin (filaggrin mutations) evidence is rising that AD is connected with dysbiosis of the microbial community. In severe forms of AD, an active treatment has been associated with recolonisation and higher cutaneous and gut microbial diversity.

Furthermore in the skin microbiota of 118 atopic subjects analyzed by 16S RNA sequencing and in vitro assays on skin cells, it was shown that incubation with Acinetobacter species (Proteobacteria), induced a strong TH1 and anti-inflammatory responses by immune cells and skin cells and protected against allergic sensitization and lung inflammation through the skin. The same results were obtained in a mouse model. So the skin commensals play a key role in tuning the balance of TH1/TH2 response to environmental allergens.              

On practical point of view, we must remember that abundances of Proteobacteria are associated with much forest and agricultural lands which enrich the microbiota, with far reaching consequences for public health.

5.    Modulation of Gut Microbiota in Prevention and Treatment of Allergy

Theme: Immunology – Allergy treatment
Key words: Gut Microbiota – Probiotics – Prebiotics – Fecal Transplantation.

Probiotics, Prebiotics and dietary fibers, are approaches widely used to favorably modulate the disruption of host-microorganism homeostasis, but, apart from experimental models, the results are generally modest in humans.              

As for Antibiotics, there is evidence, in animal models, of their role in increased lung inflammation: vancomycin treated mice revealed an increase of Lactobacillacae family members and reduction in Bacteroides, directing the immune response towards an allergic phenotype and in neonates towards asthma. But other antibiotics, such as streptomycin do not show this effect.      

Fecal Transplantation is rather used for the treatment of Intestinal Bowel diseases.

Manipulation of the microbiota with specific microbial groups to favour the growth of particular bacteria, begin to be tested as strategies to prevent allergic diseases

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Last updated 26 May 2015