Histidine transport is essential for the growth of Staphylococcus aureus at low pH.

Staphylococcus aureus is an opportunistic pathogen capable of causing many different human diseases. During colonization and infection, S. aureus will encounter a range of hostile environments, including acidic conditions such as those found on the skin and within macrophages. However, little is known about the mechanisms that S. aureus uses to detect and respond to low pH. Here, we employed a transposon sequencing approach to determine on a genome-wide level the genes required or detrimental for growth at low pH. We identified 31 genes that were essential for the growth of S. aureus at pH 4.5 and confirmed the importance of many of them through follow up experiments using mutant strains inactivated for individual genes. Most of the genes identified code for proteins with functions in cell wall assembly and maintenance. These data suggest that the cell wall has a more important role than previously appreciated in promoting bacterial survival when under acid stress. We also identified several novel processes previously not linked to the acid stress response in S. aureus. These include aerobic respiration and histidine transport, the latter by showing that one of the most important genes, SAUSA300_0846, codes for a previously uncharacterized histidine transporter. We further show that under acid stress, the expression of the histidine transporter gene is increased in WT S. aureus. In a S. aureus SAUSA300_0846 mutant strain expression of the histidine biosynthesis genes is induced under acid stress conditions allowing the bacteria to maintain cytosolic histidine levels. This strain is, however, unable to maintain its cytosolic pH to the same extent as a WT strain, revealing an important function specifically for histidine transport in the acid stress response of S. aureus.

The genes mgtE and spoVG are involved in zinc tolerance of Staphylococcus aureus.

Metals are essential for all living organisms, but the type of metal and its concentration determines its action. Even low concentrations of metals may have toxic effects on organisms and therefore exhibit antimicrobial activities. In this study, we investigate the evolutionary adaptation processes of Staphylococcus aureus to metals and common genes for metal tolerance. Laboratory and clinical isolates were treated with manganese, cobalt, zinc, or nickel metal salts to generate growth-adapted mutants. After growth in medium supplemented with zinc, whole-genome sequencing identified, among others, two genes, mgtE (SAUSA300_0910), a putative magnesium transporter and spoVG (SAUSA300_0475), a global transcriptional regulator, as hot spots for stress-induced single-nucleotide polymorphisms (SNPs). SNPs in mgtE were also detected in mutants treated with high levels of cobalt or nickel salts. To investigate the effect of these genes on metal tolerance, deletion mutants and complementation strains in an S. aureus USA300 LAC* laboratory strain were generated. Both, the mgtE and spoVG deletion strains were more tolerant to cobalt, manganese, and zinc. The mgtE mutant was also more tolerant to nickel exposure. Inductively coupled plasma mass spectrometry analysis demonstrated that the mgtE deletion mutant accumulated less intracellular zinc than the wild type, explaining increased tolerance. From these results, we conclude that mgtE gene inactivation increases zinc tolerance presumably due to reduced uptake of zinc. For the SpoVG mutant, no direct effect on the intracellular zinc concentration was detected, indicating toward different pathways to increase tolerance. Importantly, inactivation of these genes offers a growth advantage in environments containing certain metals, pointing toward a common tolerance mechanism. IMPORTANCE: Staphylococcus aureus is an opportunistic pathogen causing tremendous public health burden and high mortality in invasive infections. Treatment is becoming increasingly difficult due to antimicrobial resistances. The use of metals in animal husbandry and aquaculture to reduce bacterial growth and subsequent acquisition of metal resistances has been shown to co-select for antimicrobial resistance. Therefore, understanding adaptive mechanisms that help S. aureus to survive metal exposure is essential. Using a screening approach, we were able to identify two genes encoding the transporter MgtE and the transcriptional regulator SpoVG, which conferred increased tolerance to specific metals such as zinc when inactivated. Further testing showed that the deletion of mgtE leads to reduced intracellular zinc levels, suggesting a role in zinc uptake. The accumulation of mutations in these genes when exposed to other metals suggests that inactivation of these genes could be a common mechanism for intrinsic tolerance to certain metals.

Identifying Predictors of PASI100 Responses up to Month 12 in Patients with Moderate-to-severe Psoriasis Receiving Biologics in the Psoriasis Study of Health Outcomes (PSoHO).

Despite the abundance of data concerning biologic treatments for patients with psoriasis, clinicians are often challenged with discerning the optimal treatment for each patient. To inform this selection, this study explored whether a patient's baseline characteristics or disease profile could predict the likelihood of achieving complete skin clearance with biologic treatment. Machine-learning and other statistical methods were applied to the substantial data collected from patients with moderate-to-severe psoriasis in the ongoing, international, prospective, observational Psoriasis Study of Health Outcomes (PSoHO). The 3 measures of complete skin clearance were a psoriasis area and severity index (PASI)100 response at (a) week 12, (b) month 12, and (c) week 12 and maintain ed at month 6 and month 12 (PASI100 durability). From these real-world data, the absence of nail psoriasis emerged  as the most consistent feature that may be used by clinicians to predict high-level treatment responses with biologic treatment. Other significant predictors of skin clearance with biologic treatments were the absence of hypertension and a lower body surface area affected by psoriasis. Overall, this study evidences the substantial challenge of identifying reliable clinical markers of treatment response for patients with psoriasis and highlights the importance of regular screening for psoriatic nail involvement.

Diastereoselective Reductive Etherification Via High-Throughput Experimentation: Access to Pharmaceutically Relevant Alkyl Ethers.

This manuscript describes the development of the first diastereoselective intermolecular synthesis of alkyl ethers via reductive etherification of diverse ketones or aldehydes with alcohols. Key to this development was the use of low-temperature high-throughput experimentation (HTE) technologies that enabled rapid reaction optimizations and parallel synthesis. A broad scope of pharmaceutically relevant substrates was surveyed, which formed alkyl ethers effectively. In addition, we demonstrated that the diastereoselectivity of this transformation can be readily modulated by prudent selection of the reductant.

Human fetal dendritic cells promote prenatal T-cell immune suppression through arginase-2.

During gestation the developing human fetus is exposed to a diverse range of potentially immune-stimulatory molecules including semi-allogeneic antigens from maternal cells, substances from ingested amniotic fluid, food antigens, and microbes. Yet the capacity of the fetal immune system, including antigen-presenting cells, to detect and respond to such stimuli remains unclear. In particular, dendritic cells, which are crucial for effective immunity and tolerance, remain poorly characterized in the developing fetus. Here we show that subsets of antigen-presenting cells can be identified in fetal tissues and are related to adult populations of antigen-presenting cells. Similar to adult dendritic cells, fetal dendritic cells migrate to lymph nodes and respond to toll-like receptor ligation; however, they differ markedly in their response to allogeneic antigens, strongly promoting regulatory T-cell induction and inhibiting T-cell tumour-necrosis factor-α production through arginase-2 activity. Our results reveal a previously unappreciated role of dendritic cells within the developing fetus and indicate that they mediate homeostatic immune-suppressive responses during gestation.

Ultra-deep long-read sequencing detects IS-mediated gene duplications as a potential trigger to generate arrays of resistance genes and a mechanism to induce novel gene variants such as blaCTX-M-243.

BACKGROUND: Extended-spectrum ß-lactamases (ESBLs) are enzymes that can render their hosts resistant to various ß-lactam antibiotics. CTX-M-type enzymes are the most prevalent ESBLs and the main cause of resistance to third-generation cephalosporins in Enterobacteriaceae. The number of described CTX-M types is continuously rising, currently comprising over 240 variants. During routine screening we identified a novel blaCTX-M gene. OBJECTIVES: To characterize a novel blaCTX-M variant harboured by a multidrug-resistant Escherichia coli isolate of sequence type ST354. METHODS: Antibiotic susceptibilities were determined using broth microdilution. Genome and plasmid sequences were reconstructed using short- and long-read sequencing. The novel blaCTX-M locus was analysed using long-read and Sanger sequencing. Plasmid polymorphisms were determined in silico on a single plasmid molecule level. RESULTS: The novel blaCTX-M-243 allele was discovered alongside a nearly identical blaCTX-M-104-containing gene array on a 219 kbp IncHI2A plasmid. CTX-M-243 differed from CTX-M-104 by only one amino acid substitution (N109S). Ultra-deep (2300-fold coverage) long-read sequencing revealed dynamic scaling of the blaCTX-M genetic contexts from one to five copies. Further antibiotic resistance genes such as blaTEM-1 also exhibited sequence heterogeneity but were stable in copy number. CONCLUSIONS: We identified the novel ESBL gene blaCTX-M-243 and illustrate a dynamic system of varying blaCTX-M copy numbers. Our results highlight the constant emergence of new CTX-M family enzymes and demonstrate a potential evolutionary platform to generate novel ESBL variants and possibly other antibiotic resistance genes.

Recurrent bacteremia with a hypermucoviscous Escherichia coli isolated from a patient with perihilar cholangiocarcinoma: insights from a comprehensive genome-based analysis.

BACKGROUND: Escherichia coli (E. coli) is a common human pathogen, responsible for a broad spectrum of infections. Sites of infection can vary, but the hepato-biliary system is of particular concern due to the infection-associated formation of gallstones and the spread of pathogens from the bile ducts into the bloodstream. CASE PRESENTATION: The presented case is striking, as the detected isolate showed a positive string test. This hypermucoviscous phenotype is atypical for E. coli and a particular feature of hypervirulent Klebsiella pneumoniae (K. pneumoniae) variants. OBJECTIVES: To provide new insights into the genomic background of an E. coli strain with an unusual hypermucoviscous phenotype using hybrid short- and long-read sequencing approaches. RESULTS: Complete hybrid assemblies of the E. coli genome and plasmids were done and used for genome based typing. Isolate 537-20 was assigned to the multilocus sequence type ST88 and serotype O8:H4. The strain showed a close relationship to avian pathogenic strains. Analysis of the chromosome and plasmids revealed the presence of several virulence factors, such as the Conserved Virulence Plasmidic (CVP) region on plasmid 537-20_1, including several iron acquisition genes (sitABCD, iroABCDEN, iucABCD, hbd) and the iutA gene encoding the receptor of the siderophore aerobactin. The hypermucoviscous phenotype could be caused by encapsulation of putative K. pneumoniae origin. CONCLUSIONS: Hybrid sequencing enabled detailed genomic characterization of the hypermucoviscous E. coli strain, revealing virulence factors that have their putative origin in K. pneumoniae.

Sustained Resolution of Nail Psoriasis Through 5 Years with Ixekizumab: A Post-Hoc analysis from UNCOVER-3.

Nail psoriasis is a chronic, difficult-to-treat condition affecting almost half of patients with psoriasis. It is associated with considerable social stigma and impairment of patients' quality of life. The aim of this study was to assess improvements in objective measures of nail psoriasis among patients from the long-term extension of the UNCOVER-3 study who received the interleukin-17A inhibitor ixekizumab and had either any degree of nail psoriasis (Nail Psoriasis Severity Index (NAPSI) >=1) or significant nail psoriasis (fingernail NAPSI ≥ 16 and ≥ 4 fingernails involved) at baseline. Efficacy outcomes reported through week 264 included the mean percentage improvements from baseline in NAPSI score and the proportion of patients achieving nail psoriasis resolution (NAPSI=0). In UNCOVER-3, 56.9% (219/385) of patients had nail psoriasis at baseline; of those, 61.2% (134/219) had significant nail psoriasis. At week 60, a total of 66.9% and 59.1% of patients with baseline nail psoriasis and significant baseline nail psoriasis, respectively, reported complete clearance of nail psoriasis, an effect which was sustained through week 264. This analysis demonstrates that continuous treatment with ixekizumab in adult patients with moderate-to-severe-psoriasis through 264 weeks was associated with improvements and clearance of fingernail psoriasis, irrespective of the severity of nail psoriasis at baseline.

Real-World Treatment Patterns and Treatment Benefits among Adult Patients with Atopic Dermatitis: Results from the Atopic Dermatitis Patient Satisfaction and Unmet Need Survey.

Atopic dermatitis is a chronic inflammatory skin disorder associated with a heterogeneous presentation and considerable disease burden. Exploring atopic dermatitis treatment patterns and patient benefits could improve disease management and patients' quality of life. This study aimed to describe current and previous atopic dermatitis treatment patterns and patient benefits from those treatments to inform disease management. Data were collected in 10 countries. Adults (n = 1,988) with confirmed moderate-to-severe atopic dermatitis completed a web-based cross-sectional survey. Most patients (86.6%) had body surface area involvement <10%, and therapies used were topical (69.7%), systemic (28.1%), and biologics (2.3%). Most flares were managed by topical monotherapies (73.4%), even in patients with body surface area involvement ≥10%. Treatment expectations were met only partially, or not at all, in 75% of patients. Those with body surface area involvement ≥10% reported lower treatment satisfaction. Overall, this study highlights the unmet medical needs in atopic dermatitis management.

Time to Loss of Response following Withdrawal of Ixekizumab in Patients with Moderate-to-Severe Psoriasis.

In clinical practice, interruption of treatment may not result in immediate cessation of disease control, and some patients even experience sustained treatment response following treatment interruption. This post hoc analysis of UNCOVER-1 and -2 Phase 3 clinical trials characterized the time to loss of treatment response in patients with psoriasis who responded to ixekizumab through a 12-week treatment period, and who were then re-randomized to placebo for the following 48 weeks. For those with static Physician Global Assessment [sPGA]0/1 and Psoriasis Area and Severity Index [PASI]90 at Week 12, the median time to loss of PASI90 was 16.1 weeks (95% confidence interval 12.7-16.4). For those with PASI100 at Week 12, the median time to loss of PASI100 was 12.1 weeks (95% confidence interval 9.0-13.0). A small subset of patients maintained high levels of disease control through Week 60. This study adds to the growing body of evidence on sustained treatment response following treatment interruption.

Comparative effectiveness of biologics in clinical practice: week 12 primary outcomes from an international observational psoriasis study of health outcomes (PSoHO).

BACKGROUND: Clinical trials study treatment outcomes under stringent conditions, capturing incompletely the heterogeneity of patient populations and treatment complexities encountered in real-world practice. OBJECTIVES: To compare the effectiveness of anti-interleukin (IL)-17A biologics relative to other approved biologics in patients with moderate-to-severe psoriasis. METHODS: The Psoriasis Study of Health Outcomes (PSoHO) is an ongoing 3-year observational cohort study in adults with chronic moderate-to-severe plaque psoriasis initiating or switching to a new biologic. Primary study endpoint is the proportion of patients achieving 90% improvement in Psoriasis Area and Severity Index (PASI 90) and/or static Physician Global Assessment (sPGA) 0/1 at Week 12 (W12) in the anti-IL-17A cohort (ixekizumab [IXE], secukinumab) vs. all other approved biologics. Secondary outcomes include the proportion of patients who achieve PASI 75/90/100, absolute PASI scores ≤5, ≤2 and ≤1, Dermatology Life Quality Index (DLQI) score of 0/1 at W12 between the two cohorts and among the individual biologics. Comparative effectiveness analyses were conducted using Frequentist Model Averaging (FMA), a novel causal inference machine learning approach. Missing data for binary outcomes were imputed as non-response. RESULTS: Patient profiles in the anti-IL-17A cohort and other biologics cohort were similar, with more frequent comorbid psoriatic arthritis and less frequent exposure to conventional treatments in the patients receiving anti-IL-17A biologics. At W12, 71.4% of patients who received an anti-IL-17A biologic achieved PASI 90 and/or sPGA 0/1 compared to 58.6% of patients who received other biologics (odds ratios [OR], 1.9; 95% confidence intervals [CI], [1.6, 2.4]). Similar findings were observed for secondary outcomes. CONCLUSIONS: These results reflect the high efficacy and early onset of skin clearance of IL-17A inhibitors observed in randomized clinical trials and confirm the effectiveness of anti-IL-17A biologics in the real-world setting.

High-throughput transposon sequencing highlights the cell wall as an important barrier for osmotic stress in methicillin resistant Staphylococcus aureus and underlines a tailored response to different osmotic stressors.

Staphylococcus aureus is an opportunistic pathogen that can cause soft tissue infections but is also a frequent cause of foodborne illnesses. One contributing factor for this food association is its high salt tolerance allowing this organism to survive commonly used food preservation methods. How this resistance is mediated is poorly understood, particularly during long-term exposure. In this study, we used transposon sequencing (TN-seq) to understand how the responses to osmotic stressors differ. Our results revealed distinctly different long-term responses to NaCl, KCl and sucrose stresses. In addition, we identified the DUF2538 domain containing gene SAUSA300_0957 (gene 957) as essential under salt stress. Interestingly, a 957 mutant was less susceptible to oxacillin and showed increased peptidoglycan crosslinking. The salt sensitivity phenotype could be suppressed by amino acid substitutions in the transglycosylase domain of the penicillin-binding protein Pbp2, and these changes restored the peptidoglycan crosslinking to WT levels. These results indicate that increased crosslinking of the peptidoglycan polymer can be detrimental and highlight a critical role of the bacterial cell wall for osmotic stress resistance. This study will serve as a starting point for future research on osmotic stress response and help develop better strategies to tackle foodborne staphylococcal infections.

Identification of the main glutamine and glutamate transporters in Staphylococcus aureus and their impact on c-di-AMP production.

A Staphylococcus aureus strain deleted for the c-di-AMP cyclase gene dacA is unable to survive in rich medium unless it acquires compensatory mutations. Previously identified mutations were in opuD, encoding the main glycine-betaine transporter, and alsT, encoding a predicted amino acid transporter. Here, we show that inactivation of OpuD restores the cell size of a dacA mutant to near wild-type (WT) size, while inactivation of AlsT does not. AlsT was identified as an efficient glutamine transporter, indicating that preventing glutamine uptake in rich medium rescues the growth of the S. aureus dacA mutant. In addition, GltS was identified as a glutamate transporter. By performing growth curves with WT, alsT and gltS mutant strains in defined medium supplemented with ammonium, glutamine or glutamate, we revealed that ammonium and glutamine, but not glutamate promote the growth of S. aureus. This suggests that besides ammonium also glutamine can serve as a nitrogen source under these conditions. Ammonium and uptake of glutamine via AlsT and hence likely a higher intracellular glutamine concentration inhibited c-di-AMP production, while glutamate uptake had no effect. These findings provide, besides the previously reported link between potassium and osmolyte uptake, a connection between nitrogen metabolism and c-di-AMP signalling in S. aureus.

Asymmetric synthesis from terminal alkenes by cascades of diboration and cross-coupling.

Terminal, monosubstituted alkenes are ideal prospective starting materials for organic synthesis because they are manufactured on very large scales and can be functionalized via a broad range of chemical transformations. Alkenes also have the attractive feature of being stable in the presence of many acids, bases, oxidants and reductants. In spite of these attributes, relatively few catalytic enantioselective transformations have been developed that transform aliphatic α-olefins into chiral products with an enantiomeric excess greater then 90 per cent. With the exception of site-controlled isotactic polymerization of α-olefins, none of these catalytic enantioselective processes results in chain-extending carbon-carbon bond formation to the terminal carbon. Here we describe a strategy that directly addresses this gap in synthetic methodology, and present a single-flask, catalytic enantioselective conversion of terminal alkenes into a number of chiral products. These reactions are facilitated by a neighbouring functional group that accelerates palladium-catalysed cross-coupling of 1,2-bis(boronates) relative to non-functionalized alkyl boronate analogues. In tandem with enantioselective diboration, this reactivity feature transforms alkene starting materials into a diverse array of chiral products. We note that the tandem diboration/cross-coupling reaction generally provides products in high yield and high selectivity (>95:5 enantiomer ratio), uses low loadings (1-2 mol per cent) of commercially available catalysts and reagents, offers an expansive substrate scope, and can address a broad range of alcohol and amine synthesis targets, many of which cannot be easily addressed with current technology.

Inactivation of the Monofunctional Peptidoglycan Glycosyltransferase SgtB Allows Staphylococcus aureus To Survive in the Absence of Lipoteichoic Acid.

The cell wall of Staphylococcus aureus is composed of peptidoglycan and the anionic polymers lipoteichoic acid (LTA) and wall teichoic acid. LTA is required for growth and normal cell morphology in S. aureus Strains lacking LTA are usually viable only when grown under osmotically stabilizing conditions or after the acquisition of compensatory mutations. LTA-negative suppressor strains with inactivating mutations in gdpP, which resulted in increased intracellular c-di-AMP levels, were described previously. Here, we sought to identify factors other than c-di-AMP that allow S. aureus to survive without LTA. LTA-negative strains able to grow in unsupplemented medium were obtained and found to contain mutations in sgtB, mazE, clpX, or vraT The growth improvement through mutations in mazE and sgtB was confirmed by complementation analysis. We also showed that an S. aureussgtB transposon mutant, with the monofunctional peptidoglycan glycosyltransferase SgtB inactivated, displayed a 4-fold increase in the MIC of oxacillin, suggesting that alterations in the peptidoglycan structure could help bacteria compensate for the lack of LTA. Muropeptide analysis of peptidoglycans isolated from a wild-type strain and sgtB mutant strain did not reveal any sizable alterations in the peptidoglycan structure. In contrast, the peptidoglycan isolated from an LTA-negative ltaS mutant strain showed a significant reduction in the fraction of highly cross-linked peptidoglycan, which was partially rescued in the sgtB ltaS double mutant suppressor strain. Taken together, these data point toward an important function of LTA in cell wall integrity through its necessity for proper peptidoglycan assembly.IMPORTANCE The bacterial cell wall acts as a primary defense against environmental insults such as changes in osmolarity. It is also a vulnerable structure, as defects in its synthesis can lead to growth arrest or cell death. The important human pathogen Staphylococcus aureus has a typical Gram-positive cell wall, which consists of peptidoglycan and the anionic polymers LTA and wall teichoic acid. Several clinically relevant antibiotics inhibit the synthesis of peptidoglycan; therefore, it and teichoic acids are considered attractive targets for the development of new antimicrobials. We show that LTA is required for efficient peptidoglycan cross-linking in S. aureus and inactivation of a peptidoglycan glycosyltransferase can partially rescue this defect, together revealing an intimate link between peptidoglycan and LTA synthesis.

Cyclic di-adenosine monophosphate (c-di-AMP) is required for osmotic regulation in Staphylococcus aureus but dispensable for viability in anaerobic conditions.

Cyclic di-adenosine monophosphate (c-di-AMP) is a recently discovered signaling molecule important for the survival of Firmicutes, a large bacterial group that includes notable pathogens such as Staphylococcus aureus However, the exact role of this molecule has not been identified. dacA, the S. aureus gene encoding the diadenylate cyclase enzyme required for c-di-AMP production, cannot be deleted when bacterial cells are grown in rich medium, indicating that c-di-AMP is required for growth in this condition. Here, we report that an S. aureus dacA mutant can be generated in chemically defined medium. Consistent with previous findings, this mutant had a severe growth defect when cultured in rich medium. Using this growth defect in rich medium, we selected for suppressor strains with improved growth to identify c-di-AMP-requiring pathways. Mutations bypassing the essentiality of dacA were identified in alsT and opuD, encoding a predicted amino acid and osmolyte transporter, the latter of which we show here to be the main glycine betaine-uptake system in S. aureus. Inactivation of these transporters likely prevents the excessive osmolyte and amino acid accumulation in the cell, providing further evidence for a key role of c-di-AMP in osmotic regulation. Suppressor mutations were also obtained in hepS, hemB, ctaA, and qoxB, coding proteins required for respiration. Furthermore, we show that dacA is dispensable for growth in anaerobic conditions. Together, these findings reveal an essential role for the c-di-AMP signaling network in aerobic, but not anaerobic, respiration in S. aureus.

Use of the counter selectable marker PheS* for genome engineering in Staphylococcus aureus.

The gold standard method for the creation of gene deletions in Staphylococcus aureus is homologous recombination using allelic exchange plasmids with a temperature-sensitive origin of replication. A knockout vector that contains regions of homology is first integrated into the chromosome of S. aureus by a single crossover event selected for at high temperatures (non-permissive for plasmid replication) and antibiotic selection. Next, the second crossover event is encouraged by growth without antibiotic selection at low temperature, leading at a certain frequency to the excision of the plasmid and the deletion of the gene of interest. To detect or encourage plasmid loss, either a beta-galactosidase screening method or, more typically, a counterselection step is used. We present here the adaptation of the counter-selectable marker pheS*, coding for a mutated subunit of the phenylalanine tRNA synthetase, for use in S. aureus. The PheS* protein variant allows for the incorporation of the toxic phenylalanine amino acid analogue para-chlorophenylalanine (PCPA) into proteins and the addition of 20-40 mM PCPA to rich media leads to drastic growth reduction for S. aureus and supplementing chemically defined medium with 2.5-5 mM PCPA leads to complete growth inhibition. Using the new allelic exchange plasmid pIMAY*, we delete the magnesium transporter gene mgtE in S. aureus USA300 LAC* (SAUSA300_0910/SAUSA300_RS04895) and RN4220 (SAOUHSC_00945) and demonstrate that cobalt toxicity in S. aureus is mainly mediated by the presence of MgtE. This new plasmid will aid the efficient and easy creation of gene knockouts in S. aureus.

Epicutaneous administration of the pattern recognition receptor agonist polyinosinic-polycytidylic acid activates the MDA5/MAVS pathway in Langerhans cells.

Together with keratinocytes (KCs) and the dense network of Langerhans cells (LCs), the epidermis is an ideal portal for vaccine delivery. Pattern recognition receptor agonists, in particular polyinosinic-polycytidylic acid [p(I:C)], are promising adjuvant candidates for therapeutic vaccination to generate protective T-cell immunity. Here we established an ex vivo skin explant model to study the expression and activation of double-stranded RNA (dsRNA)-sensing pattern recognition receptors in LCs and KCs in human skin. Whereas KCs expressed all known dsRNA sensing receptors at a constitutive and inducible level, LCs exclusively expressed melanoma differentiation-associated protein 5 (MDA5) in untreated skin and freshly isolated cells. Comparative assessments of downstream signaling pathways induced by p(I:C) revealed distinct mitochondrial antiviral-signaling protein, IFN-regulatory factor 3, and NF-κB activation in LCs and KCs. Consequently, p(I:C) treatment of LCs significantly induced IFN-α and IFN-ß mRNA expression, while in KCs an up-regulation of IFN-ß and TNF-α mRNA was detectable. Stimulation of LCs with specific ligands revealed that not the TLR3- but only the MDA5-specific ligand induced IFN-α2, IFN-ß, and TNF-α cytokines, but no IL-6 and -8. In KCs, both ligands induced production of high IL-6 and IL-8 levels, and low IFN-α2 and IFN-ß levels, indicating that different dsRNA-sensing receptors and/or downstream signaling pathways are activated in both cell types. Our data suggest that MDA5 may be an attractive adjuvant target for epicutaneous delivery of therapeutic vaccines with the goal to target LCs.-Tajpara, P., Schuster, C., Schön, E., Kienzl, P., Vierhapper, M., Mildner, M., Elbe-Bürger, A. Epicutaneous administration of the pattern recognition receptor agonist polyinosinic-polycytidylic acid activates the MDA5/MAVS pathway in Langerhans cells.

Prevalence of Skin-specific Autoantibodies in HIV-infected Patients and Uninfected Controls.

Various autoantibodies are detected more frequently in HIV-infected individuals than in HIV-negative controls; however, limited data exist regarding autoimmune blistering skin diseases. Using enzyme-linked immunoassay (ELISA) and indirect immunofluore-scence, no difference in the frequency and magnitude of autoantibodies against BP180, BP230, desmoglein 1 and 3 was found between 594 HIV-infected patients and 248 uninfected controls in this cross-sectional study (16.0% vs. 11.7%, respectively, for at least one positive ELISA, p = 0.11). Interestingly, reactive syphilis serology in both HIV-infected individuals and uninfected controls was associated with positive anti-BP180 ELISA results (adjusted odds ratio (OR) 2.14, 95% confidence interval (CI) 1.07-4.29, p = 0.03 and OR 4.70, CI 1.3-16.86; p = 0.0180). Our study shows a comparably low prevalence of cutaneous autoantibodies in both HIV-infected patients and uninfected controls lacking signs of autoimmune blistering skin disease. Positive BP180 ELISA in the absence of clinical signs of bullous pemphigoid should prompt further evaluation for syphilis antibodies.