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Research > Portfolio > Funded Research

Charlotte Hurabielle-Claverie, M.D., M.Sc., PhD Studemsnt, National Institute of Allergy and Infectious Diseases, Laboratory of Parasitic Diseases, Mucosal Immunology Section, National Institute of Health, Bethesda, MD, USA

Early Career Research Grant
2018

Defining the Role of Commensal-Specific Immunity in the Etiology of Psoriasis

Psoriasis
Active
Supported by Karen and Dale White Research Center of Excellence
 
Layman's Statement: The skin is the largest barrier surface with the environment. It is also a dynamic ecosystem that is inhabited mainly by bacteria and fungi. These resident skin microbes play a fundamental role in skin physiology and immunity. Preliminary data from Dr. Belkaid’s laboratory, where I am a PhD student after completing my training in dermatology as a resident, suggests that certain skinresident bacteria and fungi can activate specific immune cells in the skin in experimental psoriasis model in mice. These specific immune cells increase skin inflammation and thus participate to the development of psoriasis inflammation.
 
I hypothesize that aberrant immune responses to skin bacteria and fungi may contribute to skin inflammation in human psoriasis. To address this, I propose to isolate and characterize bacteria and fungi from the skin of patients with psoriasis. I will then determine how these microbes stimulate immune cells in both psoriasis patients and healthy donors. It will thus allow to assess immune reactivity of patients with psoriasis to their own microbes and to test the possibility that these responses represent an important aspect of the etiology of the disease.
 

 

Grant Abstract: The skin is the body’s most exposed environmental interface and acts as a first line of physical and immunological defense. The skin is a complex and dynamic ecosystem that is inhabited by bacteria, archaea, fungi, and viruses. These microbes—collectively referred to as the skin microbiota—are fundamental to skin physiology and immunity. Notably, it has previously been shown that defined commensals such as Staphylococcus epidermidis or Candida albicans can promote skin T cell responses, particularly IL-17A production. These findings have obvious relevance to the etiology of psoriasis, a disease characterized by a massive influx of lymphocytes and in which IL-17A acts as the central inflammatory cytokine. This disease is also characterized by major defects in barrier integrity and function, a phenomenon that can have a profound impact on the sensing of otherwise innocuous microbes. Furthermore, alteration of the microbiota composition has been observed during psoriatic flares. Of particular interest, studies focusing on skin fungal species in psoriasis have shown distinct composition of the fungal microbiome on lesional skin of psoriasis patients compared to healthy controls. Together these observations support the idea that defined skin microbes, particularly those that promote IL-17 production, such as fungi, may play an important role in the etiology of psoriasis. Supporting this hypothesis, our preliminary data obtained in mice revealed that defined members of the skin microbiota promote inflammation during experimental psoriasis. Notably, we found that the presence of C. albicans prior to the induction of skin inflammation was associated with aberrant anti-fungal Th17 responses and these responses promoted massive neutrophil recruitment and activation.

The aim of the proposed project is to assess aberrant responses to the skin microbiota during psoriasis with the ultimate goal to understand the role of commensal-specific immunity in the etiology of human psoriasis. We hope that this work will not only validate, in humans, our hypothesis based on experimental models, but will also allow the development of novel therapies directed toward the management of the microbiota.