The microbiome can promote or disrupt human health by influencing both adaptive and innate immune functions. We tested whether bacteria that normally reside on human skin participate in host defense by killing Staphylococcus aureus, a pathogen commonly found in patients with atopic dermatitis (AD) and an important factor that exacerbates this disease. High-throughput screening for antimicrobial activity against S.aureus was performed on isolates of coagulase-negative Staphylococcus (CoNS) collected from the skin of healthy and AD subjects. CoNS strains with antimicrobial activity were common on the normal population but rare on AD subjects. A low frequency of strains with antimicrobial activity correlated with colonization by S.aureus. The antimicrobial activity was identified as previously unknown antimicrobial peptides (AMPs) produced by CoNS species including Staphylococcus epidermidis and Staphylococcus hominis. These AMPs were strain-specific, highly potent, selectively killed S.aureus, and synergized with the human AMP LL-37. Application of these CoNS strains to mice confirmed their defense function in vivo relative to application of nonactive strains. Strikingly, reintroduction of antimicrobial CoNS strains to human subjects with AD decreased colonization by S.aureus. These findings show how commensal skin bacteria protect against pathogens and demonstrate how dysbiosis of the skin microbiome can lead to disease.

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Highlights d Neonatal skin is enriched with immature fat and adipogenic dermal fibroblasts d Dermal immature fat and adipogenic-antimicrobial dFBs are lost with age d TGF-b pathway promotes the age-related adipogenic-tofibrotic switch of dFBs d Inhibition of TGFBR restores antimicrobial function of dFBs in adult mice

Tyrosine 411 of human albumin is an established site for covalent attachment of 10-fluoroethoxyphosphinyl-N-biotinamidopentyldecanamide (FP-biotin), diisopropylfluorophosphate, chlorpyrifos oxon, soman, sarin, and dichlorvos. This work investigated the hypothesis that other residues in albumin could be modified by organophosphorus agents (OP). Human plasma was aggressively treated with FP-biotin; plasma proteins were separated into high and low abundant portions using a proteome partitioning antibody kit, and the proteins were digested with trypsin. The FP-biotinylated tryptic peptides were isolated by binding to monomeric avidin beads. The major sites of covalent attachment identified by mass spectrometry were Y138, Y148, Y401, Y411, Y452, S232, and S287 of human albumin. Prolonged treatment of pure human albumin with chlorpyrifos oxon labeled Y138, Y150, Y161, Y401, Y411, and Y452. To identify the most reactive residue, albumin was treated for 2 h with DFP, FP-biotin, chlorpyrifos oxon, or soman, digested with trypsin or pepsin, and analyzed by mass spectrometry. The most reactive residue was always Tyr 411. Diethoxyphosphate-labeled Tyr 411 was stable for months at pH 7.4. These results will be useful in the development of specific antibodies to detect OP exposure and to engineer albumin for use as an OP scavenger.

Inflammatory acne vulgaris afflicts hundreds of millions of people globally. Propionibacterium acnes, an opportunistic skin bacterium, has been linked to the pathogenesis of acne vulgaris. Our results show that a secretory Christie-Atkins-Munch-Petersen (CAMP) factor of P. acnes is up-regulated in anaerobic cultures. Mutation of CAMP factor significantly diminishes P. acnes colonization and inflammation in mice, demonstrating the essential role of CAMP factor in the cytotoxicity of P. acnes. Vaccination of mice with CAMP factor considerably reduced the growth of P. acnes and production of MIP-2, a murine counterpart of human IL-8. Acne lesions were collected from patients to establish an ex vivo acne model for validation of the efficacy of CAMP factor antibodies in the neutralization of the acne inflammatory response. The P. acnes CAMP factor and two proinflammatory cytokines (IL-8 and IL-1β) were expressed at higher levels in acne lesions than those in nonlesional skin. Incubation of ex vivo acne explants with monoclonal antibodies to CAMP factor markedly attenuated the amounts of IL-8 and IL-1β. Our work using an ex vivo acne model shows that P. acnes CAMP factor is an essential source of inflammation in acne vulgaris.