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Mechanisms for control of skin immune function by the microbiome. Curr Opin Immunol 2021; 72:324-330. [PMID: 34537476 DOI: 10.1016/j.coi.2021.09.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 09/07/2021] [Indexed: 11/22/2022]
Abstract
The skin represents the largest area for direct contact between microbes and host immunocytes and is a site for constant communication between the host and this diverse and essential microbial community. Coagulase-negative staphylococci are an abundant bacterial genus on the human skin and are regulated through various mechanisms that include the epidermal barrier environment and innate and adaptive immune systems within the epidermis and dermis. In turn, some species and strains of these bacteria produce beneficial products that augment host immunity by exerting specifically targeted antimicrobial, anti-inflammatory, or anti-neoplastic activity while also promoting broad innate and adaptive immune responses. The use of selected skin commensals as a therapeutic has shown promise in recent human clinical trials. This emerging concept of bacteriotherapy is defining mechanisms of action and validating the dependence on the microbiome for maintenance of immune homeostasis.
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Chinnappan M, Harris-Tryon TA. Novel mechanisms of microbial crosstalk with skin innate immunity. Exp Dermatol 2021; 30:1484-1495. [PMID: 34252227 DOI: 10.1111/exd.14429] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 06/28/2021] [Accepted: 07/06/2021] [Indexed: 12/12/2022]
Abstract
Skin is an organ with a dynamic ecosystem that harbours pathogenic and commensal microbes, which constantly communicate amongst each other and with the host immune system. Evolutionarily, skin and its microbiota have evolved to remain in homeostasis. However, frequently this homeostatic relationship is disturbed by a variety of factors such as environmental stress, diet, genetic mutations, and the microbiome itself. Commensal microbes also play a major role in the maintenance of microbial homeostasis. In addition to their ability to limit pathogens, many skin commensals such as Staphylococcus epidermidis and Cutibacterium acnes have recently been implicated in disease pathogenesis either by directly modulating the host immune components or by supporting the expansion of other pathogenic microbes. Likewise, opportunistic skin pathogens such as Staphylococcus aureus and Staphylococcus lugdunensis are able to breach the skin and cause disease. Though much has been established about the microbiota's function in skin immunity, we are in a time where newer mechanistic insights rapidly redefine our understanding of the host/microbial interface in the skin. In this review, we provide a concise summary of recent advances in our understanding of the interplay between host defense strategies and the skin microbiota.
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Affiliation(s)
- Mahendran Chinnappan
- Department of Dermatology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Tamia A Harris-Tryon
- Department of Dermatology, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX, USA
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53
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Schäbitz A, Eyerich K, Garzorz-Stark N. So close, and yet so far away: The dichotomy of the specific immune response and inflammation in psoriasis and atopic dermatitis. J Intern Med 2021; 290:27-39. [PMID: 33428274 DOI: 10.1111/joim.13235] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 10/13/2020] [Accepted: 12/09/2020] [Indexed: 12/11/2022]
Abstract
Characterization of the complex interplay between cytokines, chemokines and microorganisms has led to a better understanding of the pathogenesis of both psoriasis and AD and resulted in new therapeutics targeting distinct immune responses. Psoriasis and AD share many characteristics: they are highly prevalent, chronic, cause primarily skin inflammation, but are associated with comorbidities, and come with a devastating quality of life due to itch and stigmatization. However, the pathogenesis of psoriasis and AD is opposing - psoriasis is dominated by a Th17 immune response that causes neutrophil migration, induction of innate immunity and exaggerated epithelial metabolism. Leading cytokines of this Th17 immune response are IL-17A and F, IL-22 and TNF-a. AD is characterized by Th2 immunity characterized by the signature cytokines IL-4 and IL-13 leading to an impaired epidermal barrier, dampened innate immunity and eosinophil migration. This review compares genetics, microbiome and T-cell infiltrate and resulting epithelial response in psoriasis and AD. Whilst the antagonistic course of psoriasis and AD is confirmed by response to specific biologics targeting the key cytokines of inflammation in psoriasis and AD, respectively, clinically overlapping phenotypes are challenging in our daily clinical practice. We conclude this review by summarizing what is known about these mixed phenotypes and how the identification of clinically relevant endotypes and molecular-driven decision-making is the next step in the field of dermato-immunology.
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Affiliation(s)
- A Schäbitz
- From the, Division of Dermatology and Venereology, Department of Medicine Solna, and Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
| | - K Eyerich
- From the, Division of Dermatology and Venereology, Department of Medicine Solna, and Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden.,Department of Dermatology and Venereology, Unit of Dermatology, Karolinska University Hospital, Stockholm, Sweden.,Department of Dermatology and Allergy, Technical University of Munich, Munich, Germany
| | - N Garzorz-Stark
- From the, Division of Dermatology and Venereology, Department of Medicine Solna, and Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden.,Department of Dermatology and Allergy, Technical University of Munich, Munich, Germany
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Abstract
The skin microbiome is an ecosystem comprised of a multitude of microbial species interacting with their surroundings, including other microbes and host epithelial and immune cells. These interactions are the basis of important roles within the skin microbiome that provide benefit to the host, boosting multiple aspects of barrier function, a critical function of this essential organ. However, with reward always comes risk; resident skin microbes function in a context-dependent manner, set on the backdrop of a dynamic host and microbial milieu. Here, we discuss the reward of hosting a microbial ecosystem on the skin, including protection from pathogens and tuning of the skin microenvironment. We also give consideration to how these skin residents, often termed "commensals" can cause disorder, damage, and promote skin disease.
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Affiliation(s)
- Laurice Flowers
- Department of Dermatology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
| | - Elizabeth A Grice
- Department of Dermatology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA.
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55
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Hendriks A, Mnich ME, Clemente B, Cruz AR, Tavarini S, Bagnoli F, Soldaini E. Staphylococcus aureus-Specific Tissue-Resident Memory CD4 + T Cells Are Abundant in Healthy Human Skin. Front Immunol 2021; 12:642711. [PMID: 33796109 PMCID: PMC8008074 DOI: 10.3389/fimmu.2021.642711] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 02/18/2021] [Indexed: 12/12/2022] Open
Abstract
The skin is an immunocompetent tissue that harbors several kinds of immune cells and a plethora of commensal microbes constituting the skin microbiome. Staphylococcus aureus is a prominent skin pathogen that colonizes a large proportion of the human population. We currently have an incomplete understanding of the correlates of protection against S. aureus infection, however genetic and experimental evidence has shown that CD4+ T cells play a key role in orchestrating a protective anti-S. aureus immune response. A high S. aureus-specific memory CD4+ T cell response has been reported in the blood of healthy subjects. Since T cells are more abundant in the skin than in blood, we hypothesized that S. aureus-specific CD4+ T cells could be present in the skin of healthy individuals. Indeed, we observed proliferation of tissue-resident memory CD4+ T cells and production of IL-17A, IL-22, IFN-γ and TNF-β by cells isolated from abdominal skin explants in response to heat-killed S. aureus. Remarkably, these cytokines were produced also during an ex vivo epicutaneous S. aureus infection of human skin explants. These findings highlight the importance of tissue-resident memory CD4+ T cells present at barrier sites such as the skin, a primary entry site for S. aureus. Further phenotypical and functional characterization of these cells will ultimately aid in the development of novel vaccine strategies against this elusive pathogen.
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Affiliation(s)
- Astrid Hendriks
- GSK, Siena, Italy.,Medical Microbiology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Malgorzata Ewa Mnich
- GSK, Siena, Italy.,Medical Microbiology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | | | - Ana Rita Cruz
- GSK, Siena, Italy.,Medical Microbiology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
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56
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Cau L, Williams MR, Butcher AM, Nakatsuji T, Kavanaugh JS, Cheng JY, Shafiq F, Higbee K, Hata TR, Horswill AR, Gallo RL. Staphylococcus epidermidis protease EcpA can be a deleterious component of the skin microbiome in atopic dermatitis. J Allergy Clin Immunol 2021; 147:955-966.e16. [PMID: 32634452 PMCID: PMC8058862 DOI: 10.1016/j.jaci.2020.06.024] [Citation(s) in RCA: 77] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 05/19/2020] [Accepted: 06/09/2020] [Indexed: 12/20/2022]
Abstract
BACKGROUND Staphylococcus aureus and Staphylococcus epidermidis are the most abundant bacteria found on the skin of patients with atopic dermatitis (AD). S aureus is known to exacerbate AD, whereas S epidermidis has been considered a beneficial commensal organism. OBJECTIVE In this study, we hypothesized that S epidermidis could promote skin damage in AD by the production of a protease that damages the epidermal barrier. METHODS The protease activity of S epidermidis isolates was compared with that of other staphylococcal species. The capacity of S epidermidis to degrade the barrier and induce inflammation was examined by using human keratinocyte tissue culture and mouse models. Skin swabs from atopic and healthy adult subjects were analyzed for the presence of S epidermidis genomic DNA and mRNA. RESULTS S epidermidis strains were observed to produce strong cysteine protease activity when grown at high density. The enzyme responsible for this activity was identified as EcpA, a cysteine protease under quorum sensing control. EcpA was shown to degrade desmoglein-1 and LL-37 in vitro, disrupt the physical barrier, and induce skin inflammation in mice. The abundance of S epidermidis and expression of ecpA mRNA were increased on the skin of some patients with AD, and this correlated with disease severity. Another commensal skin bacterial species, Staphylococcus hominis, can inhibit EcpA production by S epidermidis. CONCLUSION S epidermidis has commonly been regarded as a beneficial skin microbe, whereas S aureus has been considered deleterious. This study suggests that the overabundance of S epidermidis found on some atopic patients can act similarly to S aureus and damage the skin by expression of a cysteine protease.
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Affiliation(s)
- Laura Cau
- Department of Dermatology, University of California San Diego, San Diego, Calif; R&D Department, SILAB, Brive, France
| | - Michael R Williams
- Department of Dermatology, University of California San Diego, San Diego, Calif
| | - Anna M Butcher
- Department of Dermatology, University of California San Diego, San Diego, Calif
| | - Teruaki Nakatsuji
- Department of Dermatology, University of California San Diego, San Diego, Calif
| | - Jeffrey S Kavanaugh
- Department of Immunology and Microbiology, University of Colorado Anschutz, Medical Campus, Aurora, Colo
| | - Joyce Y Cheng
- Department of Dermatology, University of California San Diego, San Diego, Calif
| | - Faiza Shafiq
- Department of Dermatology, University of California San Diego, San Diego, Calif
| | - Kyle Higbee
- Department of Dermatology, University of California San Diego, San Diego, Calif
| | - Tissa R Hata
- Department of Dermatology, University of California San Diego, San Diego, Calif
| | - Alexander R Horswill
- Department of Immunology and Microbiology, University of Colorado Anschutz, Medical Campus, Aurora, Colo; Department of Veterans Affairs Eastern Colorado Health Care System, Aurora, Colo
| | - Richard L Gallo
- Department of Dermatology, University of California San Diego, San Diego, Calif; Center for Microbiome Innovation, University of California San Diego, San Diego, Calif.
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Moosbrugger-Martinz V, Hackl H, Gruber R, Pilecky M, Knabl L, Orth-Höller D, Dubrac S. Initial Evidence of Distinguishable Bacterial and Fungal Dysbiosis in the Skin of Patients with Atopic Dermatitis or Netherton Syndrome. J Invest Dermatol 2021; 141:114-123. [PMID: 32553662 DOI: 10.1016/j.jid.2020.05.102] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 04/29/2020] [Accepted: 05/18/2020] [Indexed: 02/07/2023]
Abstract
Atopic dermatitis (AD) is an inflammatory skin disease in which epidermal barrier impairment, often owing to FLG null mutations, precedes immune hyperresponsiveness. Ichthyosis vulgaris is characterized by FLG null mutations and noninflamed dry skin. Netherton syndrome (NS), caused by SPINK5 null mutations, is characterized by generalized erythroderma with scaling and atopic manifestations. The goal of this work was to evaluate associations between specific skin disease features, such as ichthyotic and/or atopic manifestations, and the skin bacterial and fungal microbiota. Taxon diversity showed greater variation in the bacterial microbiota than in the fungal microbiota in the skin diseases. The relative abundances of Firmicutes (Staphylococcus) and Actinobacteria (Corynebacterium) were augmented in ichthyosis vulgaris, AD, and NS, whereas those of Proteobacteria/Enhydrobacter and Bacteroidetes were reduced, regardless of body site. Furthermore, proportions of Staphylococcus were correlated with transepidermal water loss and serum IgE levels. Nevertheless, the skin of patients with low to mild AD was overcolonized with Staphylococcus epidermidis and not with Staphylococcus aureus. Ascomycota were increased in both AD and NS, but from expansion of different fungal species. Finally, the expansion of pathologic bacteria in AD and NS might be supported by surrounding fungi. Thus, distinguishable bacterial and fungal skin dysbiosis in AD, NS, and ichthyosis vulgaris emphasizes disease-specific pathomechanisms.
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Affiliation(s)
- Verena Moosbrugger-Martinz
- Department of Dermatology, Venereology and Allergology, Medical University of Innsbruck, Innsbruck, Austria
| | - Hubert Hackl
- Division of Bioinformatics, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Robert Gruber
- Department of Dermatology, Venereology and Allergology, Medical University of Innsbruck, Innsbruck, Austria
| | - Matthias Pilecky
- Center for Biomedical Technology, Department for Health Sciences and Biomedicine, Danube University Krems, Krems, Austria
| | - Ludwig Knabl
- Division of Hygiene and Medical Microbiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Dorothea Orth-Höller
- Division of Hygiene and Medical Microbiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Sandrine Dubrac
- Department of Dermatology, Venereology and Allergology, Medical University of Innsbruck, Innsbruck, Austria.
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58
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Petrova E, Hovnanian A. Advances in understanding of Netherton syndrome and therapeutic implications. Expert Opin Orphan Drugs 2020. [DOI: 10.1080/21678707.2020.1857724] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Evgeniya Petrova
- Laboratory of genetic skin diseases, Université de Paris, Imagine Institute, INSERM UMR1163, Paris, France
| | - Alain Hovnanian
- Laboratory of genetic skin diseases, Université de Paris, Imagine Institute, INSERM UMR1163, Paris, France
- Departement of Genetics, AP-HP, Hôpital Necker-Enfants Malades, Paris, France
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59
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DeVore SB, Gonzalez T, Sherenian MG, Herr AB, Khurana Hershey GK. On the surface: Skin microbial exposure contributes to allergic disease. Ann Allergy Asthma Immunol 2020; 125:628-638. [PMID: 32853786 DOI: 10.1016/j.anai.2020.08.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 07/15/2020] [Accepted: 08/14/2020] [Indexed: 12/26/2022]
Abstract
OBJECTIVE To discuss the skin microbiome modulates immunity by interactions between skin immunology with keratinocytes to combat pathogens. Allergic disorders are classified by immunoglobulin E sensitivity and aberrant TH2 cell responses, and an increasing number of studies have described the associations with skin microbiome fluctuations. In this review, we discuss commensal-epidermal homeostasis and its influence on allergic disease. DATA SOURCES All included references were obtained from the PubMed database. STUDY SELECTIONS Studies addressing relevant aspects of commensal-epidermal homeostasis, skin microbiome dysbiosis, microbiome-targeted therapeutics, and prevention in allergy were included. RESULTS Homeostasis between the commensal microbiome and the epidermis is important in protecting against allergic disease. Commensals promote antiallergic TH1 and TH17 immunophenotypes within the skin and induce keratinocytes to secrete antimicrobial peptides and alarmins that enhance barrier function and antagonize proallergic organisms. Perturbations in this homeostasis, however, is associated with allergic disease development. Atopic dermatitis is associated with decreases in skin commensals and increases in the pathogen, Staphylococcus aureus. Fluctuations in the skin microbiome contributes to decreased barrier dysfunction, allergic sensitization, and TH2 cytokine secretion. Little is known about how the skin microbiome affects food allergy, allergic rhinitis, and asthma, and it is poorly understood how cutaneous inflammation influences systemic allergic responses. Therapies are targeted toward maintenance of the skin barrier, replacement of healthy commensals, and anti-TH2 biologic therapy. CONCLUSION Although the effects of commensal-epidermal homeostasis on allergy within the skin are becoming increasingly clear, future studies are necessary to assess its effects on extracutaneous allergic disorders and explore potential therapeutics targeting the skin microbiome.
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Affiliation(s)
- Stanley B DeVore
- Department of Pediatrics, Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio; Division of Asthma Research, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Tammy Gonzalez
- Department of Pediatrics, Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio; Division of Immunobiology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Michael G Sherenian
- Department of Pediatrics, Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio; Division of Asthma Research, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Division of Allergy and Immunology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Andrew B Herr
- Department of Pediatrics, Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio; Division of Immunobiology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Gurjit K Khurana Hershey
- Department of Pediatrics, Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio; Division of Asthma Research, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Division of Allergy and Immunology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
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60
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Pham-Ledard A. Quoi de neuf en recherche en 2020 ? Ann Dermatol Venereol 2020; 147:12S15-12S19. [DOI: 10.1016/s0151-9638(20)31103-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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61
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Abstract
Our skin is our first line of defense against environmental and pathogenic challenges. It is densely populated by a flora of bacteria, fungi, and viruses that normally interact with each other and with our immune system to promote skin health and homeostasis. Staphylococcus epidermidis is one of the most abundant bacterial colonizers of healthy human skin. While the field has historically assumed that all S. epidermidis isolates behave similarly, emerging evidence suggests that colonization by specific strains of S. epidermidis can either help or hurt the skin barrier depending on the context. In this short review, we discuss what is currently understood about S. epidermidis strain-level diversity and evaluate costs and benefits of S. epidermidis skin colonization. We challenge the current dogma that “all S. epidermidis strains behave equally” and posit that behavior is in fact highly context and strain dependent. Finally, in light of current proposals to use skin commensals as nonantibiotic treatments for acute or chronic skin diseases, we conclude that more work is urgently needed to fully understand the pathogenic and protective roles of commensals before we use them therapeutically.
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Affiliation(s)
- Morgan M. Brown
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Alexander R. Horswill
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, United States of America
- Department of Veterans Affairs, Eastern Colorado Healthcare System, Aurora, Colorado, United States of America
- * E-mail:
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