Gla-domain mediated targeting of externalized phosphatidylserine for intracellular delivery.

Phosphatidylserine (PS) is a negatively charged phospholipid normally localized to the inner leaflet of the plasma membrane of cells but is externalized onto the cell surface during apoptosis as well as in malignant and infected cells. Consequently, PS may comprise an important molecular target in diagnostics, imaging, and targeted delivery of therapeutic agents. While an array of PS-binding molecules exist, their utility has been limited by their inability to internalize diagnostic or therapeutic payloads. We describe the generation, isolation, characterization, and utility of a PS-binding motif comprised of a carboxylated glutamic acid (GLA) residue domain that both recognizes and binds cell surface-exposed PS, and then unlike other PS-binding molecules is internalized into these cells. Internalization is independent of the traditional endosomal-lysosomal pathway, directly entering the cytosol of the target cell rapidly. We demonstrate that this PS recognition extends to stem cells and that GLA-domain-conjugated probes can be detected upon intravenous administration in animal models of infectious disease and cancer. GLA domain binding and internalization offer new opportunities for specifically targeting cells with surface-exposed PS for imaging and delivery of therapeutics.

Infection of the murine placenta by Listeria monocytogenes induces sex-specific responses in the fetal brain.

BACKGROUND: Epidemiological data indicate that prenatal infection is associated with an increased risk of several neurodevelopmental disorders in the progeny. These disorders display sex differences in presentation. The role of the placenta in the sex-specificity of infection-induced neurodevelopmental abnormalities is not well-defined. We used an imaging-based animal model of the bacterial pathogen Listeria monocytogenes to identify sex-specific effects of placental infection on neurodevelopment of the fetus. METHODS: Pregnant CD1 mice were infected with a bioluminescent strain of Listeria on embryonic day 14.5 (E14.5). Excised fetuses were imaged on E18.5 to identify the infected placentas. The associated fetal brains were analyzed for gene expression and altered brain structure due to infection. The behavior of adult offspring affected by prenatal Listeria infection was analyzed. RESULTS: Placental infection induced sex-specific alteration of gene expression patterns in the fetal brain and resulted in abnormal cortical development correlated with placental infection levels. Furthermore, male offspring exhibited abnormal social interaction, whereas females exhibited elevated anxiety. CONCLUSION: Placental infection by Listeria induced sex-specific abnormalities in neurodevelopment of the fetus. Prenatal infection also affected the behavior of the offspring in a sex-specific manner. IMPACT: Placental infection with Listeria monocytogenes induces sexually dichotomous gene expression patterns in the fetal brains of mice. Abnormal cortical lamination is correlated with placental infection levels. Placental infection results in autism-related behavior in male offspring and heightened anxiety levels in female offspring.

Listeria monocytogenes Infection Alters the Content and Function of Extracellular Vesicles Produced by Trophoblast Stem Cells.

Placental immunity is critical for fetal health during pregnancy, as invading pathogens spread from the parental blood to the fetus through this organ. However, inflammatory responses in the placenta can adversely affect both the fetus and the pregnant person, and the balance between protective placental immune response and detrimental inflammation is poorly understood. Extracellular vesicles (EVs) are membrane-enclosed vesicles that play a critical role in placental immunity. EVs produced by placental trophoblasts mediate immune tolerance to the fetus and to the placenta itself, but these EVs can also activate detrimental inflammatory responses. The regulation of these effects is not well characterized, and the role of trophoblast EVs (tEVs) in the response to infection has yet to be defined. The Gram-positive bacterial pathogen Listeria monocytogenes infects the placenta, serving as a model to study tEV function in this context. We investigated the effect of L. monocytogenes infection on the production and function of tEVs, using a trophoblast stem cell (TSC) model. We found that tEVs from infected TSCs can induce the production of the proinflammatory cytokine tumor necrosis factor alpha (TNF-α) in recipient cells. Surprisingly, this tEV treatment could confer increased susceptibility to subsequent L. monocytogenes infection, which has not been reported previously as an effect of EVs. Proteomic analysis and RNA sequencing revealed that tEVs from infected TSCs had altered cargo compared with those from uninfected TSCs. However, no L. monocytogenes proteins were detected in tEVs from infected TSCs. Together, these results suggest an immunomodulatory role for tEVs during prenatal infection.

Charge-altering releasable transporters (CARTs) for the delivery and release of mRNA in living animals.

Functional delivery of mRNA to tissues in the body is key to implementing fundamentally new and potentially transformative strategies for vaccination, protein replacement therapy, and genome editing, collectively affecting approaches for the prevention, detection, and treatment of disease. Broadly applicable tools for the efficient delivery of mRNA into cultured cells would advance many areas of research, and effective and safe in vivo mRNA delivery could fundamentally transform clinical practice. Here we report the step-economical synthesis and evaluation of a tunable and effective class of synthetic biodegradable materials: charge-altering releasable transporters (CARTs) for mRNA delivery into cells. CARTs are structurally unique and operate through an unprecedented mechanism, serving initially as oligo(α-amino ester) cations that complex, protect, and deliver mRNA and then change physical properties through a degradative, charge-neutralizing intramolecular rearrangement, leading to intracellular release of functional mRNA and highly efficient protein translation. With demonstrated utility in both cultured cells and animals, this mRNA delivery technology should be broadly applicable to numerous research and therapeutic applications.

Rheumatology Care Using Telemedicine.

Introduction: People living in many parts of the world have limited access to diagnostic studies and therapies for rheumatologic, musculoskeletal, and connective tissue diseases. The challenge has been particularly poignant for rural areas of low- and middle-income countries. Objectives: We report on the implementation of a telemedicine program in Iran for the evaluation and treatment of patients with rheumatologic and musculoskeletal diseases. More than 4,800 patients were seen remotely over a span of 5 years by a rheumatologist in the United States. The remote rheumatologist was aided by a general physician and a nurse at a local charity hospital in northeastern Iran that has a catchment area that includes rural regions extending to the border of Afghanistan. Seventy to 90 patients were evaluated online by the remote rheumatologist 3 days a week. A subset of patients was evaluated by the rheumatologist in person every 4 months. Materials and Methods: The population of rheumatology patients was evaluated using descriptive statistics. Information collected included demographic information consisting of age, gender, and primary rheumatologic diagnosis. Results: The average age of patients who were seen was 52 years and 89% of patients were women. Approximately 50% of patients were Afghan refugees. The most common disorders included osteoarthritis (1,149, 23.6%), rheumatoid arthritis (653, 13.4%), axial spondyloarthropathies (647, 13.3%), lumbar spinal stenosis (427, 8.8%), meniscal tear of the knee (326, 6.7%), and psoriatic arthritis (217, 4.5%). Certain conditions were lower than expected such as lupus (19, 0.4%) and fibromyalgia (169, 3.5%). Diagnostic tests included serologic tests (1,328, 27.3%), plain radiographs (946, 19.5%), magnetic resonance imaging (899, 18.5%), bone densitometry (147, 3.0%), and electromyography and nerve conduction study (132, 2.7%). The most common medications prescribed were non-steroidal anti-inflammatory drugs (791, 16.3%), methotrexate (764, 15.7%), pregabalin (234, 4.8%), duloxetine (230, 4.7%), sulfasalazine (177, 3.6%), etanercept (97, 2.0%), tofacitinib (64, 1.3%), adalimumab (18, 0.4%), and infliximab (9, 0.2%). Conclusions: Telemedicine is becoming more prevalent. We report the successful use of this service in evaluation and management of rheumatic diseases in a region with limited access to rheumatologic care. We have shown that patients can be seen, evaluated, and successfully treated with a variety of medications, including biologic agents.

Differential fates of biomolecules delivered to target cells via extracellular vesicles.

Extracellular vesicles (EVs), specifically exosomes and microvesicles (MVs), are presumed to play key roles in cell-cell communication via transfer of biomolecules between cells. The biogenesis of these two types of EVs differs as they originate from either the endosomal (exosomes) or plasma (MVs) membranes. To elucidate the primary means through which EVs mediate intercellular communication, we characterized their ability to encapsulate and deliver different types of macromolecules from transiently transfected cells. Both EV types encapsulated reporter proteins and mRNA but only MVs transferred the reporter function to recipient cells. De novo reporter protein expression in recipient cells resulted only from plasmid DNA (pDNA) after delivery via MVs. Reporter mRNA was delivered to recipient cells by both EV types, but was rapidly degraded without being translated. MVs also mediated delivery of functional pDNA encoding Cre recombinase in vivo to tissues in transgenic Cre-lox reporter mice. Within the parameters of this study, MVs delivered functional pDNA, but not RNA, whereas exosomes from the same source did not deliver functional nucleic acids. These results have significant implications for understanding the role of EVs in cellular communication and for development of EVs as delivery tools. Moreover, studies using EVs from transiently transfected cells may be confounded by a predominance of pDNA transfer.

Preparation of Tc99m-Labeled Pseudomonas Bacteriophage without Adversely Impacting Infectivity or Biodistribution.

Bacteriophages (phages) are ubiquitous viruses which have adapted to infect and replicate within target bacteria, their only known hosts, in a strain specific fashion with minimal cross infectivity. The recent steep rise in antibiotic resistance throughout the world has renewed interest in adapting phages for the imaging and treatment of bacterial infection in humans. In this article, we describe the current limitations surrounding the radiolabeling of phage for the imaging and treatment of bacterial infection and methods to overcome these difficulties. Specifically, we examined the effects of hydrazinonicotinamide conjugation and removal of bacterial DNA on the infectivity, biodistribution, and radionuclide imaging of a phage lytic for a clinically relevant strain of Pseudomonas aeruginosa, a common Gram-negative bacterial pathogen often resistant to multiple antibiotics. We found that all but the briefest reaction of concentrated phage with hydrazinonicotinamide (≤3 min) resulted in nearly complete loss of infectivity. Furthermore, we determined that digestion and removal of bacterial DNA was needed to avoid high nonspecific uptake of hydrazinonicotinamide-labeled phage within the liver and spleen as well as prolonged circulation in the blood. We also demonstrate the surprisingly wide soft tissue and organ biodistribution and rapid pharmacokinetics of 99mTc-hydrazinonicotinamide-labeled phage in normal mice as well as its imaging characteristics and efficacy in wounded mice infected with bioluminescent Pseudomonas aeruginosa. In conclusion, the preservation of phage infectivity and removal of all bacterial containments including DNA are critical methodologic considerations in the labeling of phages for imaging and therapy.

Food-specific serum IgE and IgG reactivity in dogs with and without skin disease: lack of correlation between laboratories.

BACKGROUND: Despite conflicting data on their utility and no reports on interlaboratory reproducibility, serum food-specific antibodies are commonly assayed in first-opinion canine practice. HYPOTHESIS/OBJECTIVES: To determine both the variability of test results between two laboratories and the frequencies and magnitudes of food reactivity in dogs of different disease status. ANIMALS: Sera were obtained from eight dogs with cutaneous adverse food reaction (Group A), 22 with nonfood-induced atopic dermatitis (Group B), 30 with an allergic/inflammatory phenotype (Group C), 12 with miscellaneous skin diseases (Group D) and nine healthy dogs (Group E). METHODS: Paired sera were submitted to two laboratories (A and B) for assays of food-specific IgE and IgG antibodies. RESULTS: Numbers of positive IgE and IgG tests determined by each laboratory in Groups A, B, D and E were comparable (Group C not included). Significant differences in the magnitude of IgE reactivity between groups for each allergen were seen only for lamb (Laboratory A, P = 0.003); lamb reactivity in Group D exceeded Group E (P = 0.004) but was comparable between all other groups. Agreement (kappa statistic) between the two laboratories' tests was 'moderate' for one antigen (potato IgE), 'fair' for four (corn IgE, rice IgE and IgG and soya bean IgG), 'slight' for eight (six IgE and two IgG) and 'less than chance' for the remaining six antigens (three IgE and three IgG). CONCLUSIONS AND CLINICAL IMPORTANCE: These laboratories' tests appear to have dubious predictive clinical utility because they neither correlate nor distinguish between dogs of different disease status.

Unraveling the mechanisms of inhibition of silver-doped bioactive glass-ceramic particles.

Infections are a major concern in orthopedics. Antibacterial agents such as silver ions are of great interest as broad-spectrum biocides and have been incorporated into bioactive glass-ceramic particles to control the release of ions within a therapeutic concentration and provide tissue regenerative properties. In this work, the antibacterial capabilities of silver-doped bioactive glass (Ag-BG) microparticles were explored to reveal the unedited mechanisms of inhibition against methicillin-resistant Staphylococcus aureus (MRSA). The antibacterial properties were not limited to the delivery of silver ions but rather a combination of antibacterial degradation by-products. For example, nano-sized debris punctured holes in bacteria membranes, osmotic effects, and reactive oxygen species causing oxidative stress and almost 40% of the inhibition. Upon successive Ag-BG treatments, MRSA underwent phenotypic and genomic mutations which were not only insufficient to develop resistance but instead, the clones became more sensitive as the treatment was re-delivered. Additionally, the unprecedented restorative functionality of Ag-BG allowed the effective use of antibiotics that MRSA resists. The synergy mechanism was mainly identified for combinations targeting cell-wall activity and their action was proven in biofilm-like and virulent conditions. Unraveling these mechanisms may offer new insights into how to tailor healthcare materials to prevent or debilitate infections and join the fight against antibiotic resistance in clinical cases.

Bacterial Meningitis With Cerebral Edema in a Young Adult: A Simulation Case for Medical Students.

Introduction: Simulation in the preclinical medical education setting is a beneficial tool for students to develop clinical skills, supplement preexisting knowledge, and prepare for clinical rotations and beyond. We detail the complete simulation scenario, including a participant postresponse questionnaire, of a 28-year-old male who developed bacterial meningitis after experiencing an upper respiratory infection in the days prior. Methods: Simulation fellows and faculty at the Alabama College of Osteopathic Medicine created a simulation scenario pertaining to bacterial meningitis. The scenario utilized a high-fidelity patient simulator, one standardized participant for patient voiceover, one standardized participant as a patient family member, and one standardized participant as a physician consultant on an as-needed basis. Sixteen preclinical medical students from various specialty interest groups were recruited to participate in the scenario and complete the postscenario questionnaire. Results: The simulation scenario was well received by the participants, and 15 of 16 completed the postscenario questionnaire. Ninety-three percent strongly agreed the simulation was a valuable clinical experience. Additionally, 73% of participants strongly agreed that the simulation experience was realistic, 80% strongly agreed that it tested their clinical reasoning ability, and 53% strongly agreed it was appropriate for their level of clinical knowledge. Discussion: Medical simulation is a valuable educational tool tailored to maximize student learning and supplement the traditional didactic curriculum. The successful development and implementation of our meningitis simulation case further supports the continued use of medical simulation in the preclinical setting.

Silver-releasing bioactive glass nanoparticles for infected tissue regeneration.

Bacterial infections represent a formidable challenge, often leaving behind significant bone defects post-debridement and necessitating prolonged antibiotic treatments. The rise of antibiotic-resistant bacterial strains further complicates infection management. Bioactive glass nanoparticles have been presented as a promising substitute for bone defects and as carriers for therapeutic agents against microorganisms. Achieving consistent incorporation of ions into BGNs has proven challenging and restricted to a maximum ion concentration, especially when reducing the particle size. This study presents a notable achievement in the synthesis of 10 nm-sized Ag-doped bioactive glass nanoparticles (Ag-BGNs) using a modified yet straightforward Stöber method. The successful incorporation of essential elements, including P, Ca, Al, and Ag, into the glass structure at the intended concentrations (i.e., CaO wt% above 20 %) was confirmed by EDS, signifying a significant advancement in nanoscale biomaterial engineering. While exhibiting a spherical morphology and moderate dispersity, these nanoparticles tend to form submicron-sized aggregates outside of a solution state. The antibacterial effectiveness against MRSA was established across various experimental conditions, with Ag-BGNs effectively sterilizing planktonic bacteria without the need for antibiotics. Remarkably, when combined with oxacillin or fosfomycin, Ag-BGNs demonstrated a potent synergistic effect, restoring antibacterial capabilities against MRSA strains resistant to these antibiotics when used alone. Ag-BGNs exhibited potential in promoting human mesenchymal stromal cell proliferation, inducing the upregulation of osteoblast gene markers, and significantly contributing to bone regeneration in mice. This innovative synthesis protocol holds substantial promise for the development of biomaterials dedicated to the regeneration of infected tissue.

Infection of pregnant mice with Listeria monocytogenes induces fetal bradycardia.

INTRODUCTION: Listeriosis is one of the most lethal bacterial diseases for fetuses and infants. However, pregnant women who get infected with Listeria may experience only mild symptoms, making the diagnosis difficult, even when the fetus is fatally infected. METHODS: To reveal features of this infection, we conducted a multimodality imaging study of Listeria-induced miscarriage, using a pregnant mouse model. In this model, fetal morbidity and mortality can be observed in utero, noninvasively, and the timing and extent of infection can be carefully controlled. By employing in vivo bioluminescence imaging (BLI), perinatal infections were localized over time such that a correlation of infection to outcome could be determined without the need to kill the animal subject. The morbidity and viability of fetuses were assessed with ultrasound, and fetal morphology was imaged using magnetic resonance imaging (MRI). RESULTS: The ultrasound revealed sustained fetal bradycardia, the slowing of the fetal heartbeat, in infected fetuses, with an association between slowed fetal heart rate and strong bioluminescent signal. DISCUSSION: Uninfected fetuses showing no bioluminescent signal in the same uterine horn exhibited normal heartbeats. Thus, fetal bradycardia during infection was localized to the infected fetus and was not systemic or disseminated.

Factors affecting knowledge of recovery-oriented practice amongst mental health nursing and medical staff working on acute mental health inpatient units.

Over recent decades, the shift to recovery-oriented practice has been central to mental health policy. Despite this emphasis, mental health services can struggle to meet this expectation. This study explores the knowledge and attitudes in relation to the recovery-oriented practice of clinical staff working at an Australian acute inpatient mental health unit. The Recovery Knowledge Inventory (RKI) is a widely used self-report tool that assesses mental health professionals' knowledge and attitudes towards recovery; higher scores indicate higher levels of recovery knowledge and attitudes. Seventy-four staff members (44 nursing staff and 30 medical staff) completed the RKI via an online survey. The study has been reported according to the STROBE checklist for cross-sectional studies. The relationships between the RKI scores and a range of variables were considered using inferential statistics, including multivariate regression. Medical staff had higher mean RKI scores than nursing staff, although this did not meet the predefined threshold for a clinically significant difference. More years of mental health experience were associated with increased mean RKI scores for medical staff. This Australian inpatient staff cohort demonstrated higher mean RKI scores than have been observed in recent international studies of mental health professions. However, the recovery knowledge and attitude levels were disappointingly similar to those shown in earlier Australian research completed over a decade ago. Efforts are needed to further enhance the recovery knowledge of clinicians working in mental health inpatient units.

Novel internalin P homologs in Listeria.

Listeria monocytogenes (Lm) is a bacterial pathogen that causes listeriosis in immunocompromised individuals, particularly pregnant women. Several virulence factors support the intracellular lifecycle of Lm and facilitate cell-to-cell spread, allowing it to occupy multiple niches within the host and cross-protective barriers, including the placenta. One family of virulence factors, internalins, contributes to Lm pathogenicity by inducing specific uptake and conferring tissue tropism. Over 25 internalins have been identified thus far, but only a few have been extensively studied. Internalins contain leucine-rich repeat (LRR) domains that enable protein-protein interactions, allowing Lm to bind host proteins. Notably, other Listeria species express internalins but cannot colonize human hosts, prompting questions regarding the evolution of internalins within the genus Listeria. Internalin P (InlP) promotes placental colonization through interaction with the host protein afadin. Although prior studies of InlP have begun to elucidate its role in Lm pathogenesis, there remains a lack of information regarding homologs in other Listeria species. Here, we have used a computational evolutionary approach to identify InlP homologs in additional Listeria species. We found that Listeria ivanovii londoniensis (Liv) and Listeria seeligeri (Ls) encode InlP homologs. We also found InlP-like homologs in Listeria innocua and the recently identified species Listeria costaricensis. All newly identified homologs lack the full-length LRR6 and LRR7 domains found in Lm's InlP. These findings are informative regarding the evolution of one key Lm virulence factor, InlP, and serve as a springboard for future evolutionary studies of Lm pathogenesis as well as mechanistic studies of Listeria internalins.

Infection with Listeria monocytogenes alters the placental transcriptome and eicosanome.

INTRODUCTION: Placental infection and inflammation are risk factors for adverse pregnancy outcomes, including preterm labor. However, the mechanisms underlying these outcomes are poorly understood. METHODS: To study this response, we have employed a pregnant mouse model of placental infection caused by the bacterial pathogen Listeria monocyogenes, which infects the human placenta. Through in vivo bioluminescence imaging, we confirm the presence of placental infection and quantify relative infection levels. Infected and control placentas were collected on embryonic day 18 for RNA sequencing to evaluate gene expression signatures associated with infection by Listeria. RESULTS: We identified an enrichment of genes associated with eicosanoid biosynthesis, suggesting an increase in eicosanoid production in infected tissues. Because of the known importance of eicosanoids in inflammation and timing of labor, we quantified eicosanoid levels in infected and uninfected placentas using semi-targeted mass spectrometry. We found a significant increase in the concentrations of several key eicosanoids: leukotriene B4, lipoxin A4, prostaglandin A2, prostaglandin D2, and eicosatrienoic acid. DISCUSSION: Our study provides a likely explanation for dysregulation of the timing of labor following placental infection. Further, our results suggest potential biomarkers of placental pathology and targets for clinical intervention.

Engineered endosymbionts that alter mammalian cell surface marker, cytokine and chemokine expression.

Developing modular tools that direct mammalian cell function and activity through controlled delivery of essential regulators would improve methods of guiding tissue regeneration, enhancing cellular-based therapeutics and modulating immune responses. To address this challenge, Bacillus subtilis was developed as a chassis organism for engineered endosymbionts (EES) that escape phagosome destruction, reside in the cytoplasm of mammalian cells, and secrete proteins that are transported to the nucleus to impact host cell response and function. Two synthetic operons encoding either the mammalian transcription factors Stat-1 and Klf6 or Klf4 and Gata-3 were recombined into the genome of B. subtilis expressing listeriolysin O (LLO) from Listeria monocytogenes and expressed from regulated promoters. Controlled expression of the mammalian proteins from B. subtilis LLO in the cytoplasm of J774A.1 macrophage/monocyte cells altered surface marker, cytokine and chemokine expression. Modulation of host cell fates displayed some expected patterns towards anti- or pro-inflammatory phenotypes by each of the distinct transcription factor pairs with further demonstration of complex regulation caused by a combination of the EES interaction and transcription factors. Expressing mammalian transcription factors from engineered intracellular B. subtilis as engineered endosymbionts comprises a new tool for directing host cell gene expression for therapeutic and research purposes.

Efficacy of Cathelicidin-Mimetic Antimicrobial Peptoids against Staphylococcus aureus.

Staphylococcus aureus is one of the most common pathogens associated with infection in wounds. The current standard of care uses a combination of disinfection and drainage followed by conventional antibiotics such as methicillin. Methicillin and vancomycin resistance has rendered these treatments ineffective, often causing the reemergence of infection. This study examines the use of antimicrobial peptoids (sequence-specific poly-N-substituted glycines) designed to mimic naturally occurring cationic, amphipathic host defense peptides, as an alternative to conventional antibiotics. These peptoids also show efficient and fast (<30 min) killing of methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) at low micromolar concentrations without having apparent cytotoxic side effects in vivo. Additionally, these novel peptoids show excellent efficacy against biofilm formation and detachment for both MSSA and MRSA. In comparison, conventional antibiotics were unable to detach or prevent formation of biofilms. One cationic 12mer, Peptoid 1, shows great promise, as it could prevent formation of and detach biofilms at concentrations as low as 1.6 µM. The use of a bioluminescent S. aureus murine incision wound model demonstrated clearance of infection in peptoid-treated mice within 8 days, conveying another advantage these peptoids have over conventional antibiotics. These results provide clear evidence of the potential for antimicrobial peptoids for the treatment of S. aureus wound infections. IMPORTANCE Staphylococcus aureus resistance is a consistent problem with a large impact on the health care system. Infections with resistant S. aureus can cause serious adverse effects and can result in death. These antimicrobial peptoids show efficient killing of bacteria both as a biofilm and as free bacteria, often doing so in less than 30 min. As such, these antimicrobials have the potential to alleviate the burden that Staphylococcus infections have on the health care system and cause better outcomes for infected patients.

Efficacy of antimicrobial peptoids against Mycobacterium tuberculosis.

Tuberculosis is a leading cause of death worldwide. Resistance of Mycobacterium to antibiotics can make treatments less effective in some cases. We tested selected oligopeptoids--previously reported as mimics of natural host defense peptides--for activity against Mycobacterium tuberculosis and assessed their cytotoxicity. A tetrameric, alkylated, cationic peptoid (1-C13(4mer)) was most potent against M. tuberculosis and least cytotoxic, whereas an unalkylated analogue, peptoid 1(4mer), was inactive. Peptoid 1-C13(4mer) thus merits further study as a potential antituberculosis drug.

Mast cell-derived TNF can exacerbate mortality during severe bacterial infections in C57BL/6-KitW-sh/W-sh mice.

We used mast cell-engrafted genetically mast cell-deficient C57BL/6-Kit(W-sh/W-sh) mice to investigate the roles of mast cells and mast cell-derived tumor necrosis factor in two models of severe bacterial infection. In these mice, we confirmed findings derived from studies of mast cell-deficient WBB6F(1)-Kit(W/W-v) mice indicating that mast cells can promote survival in cecal ligation and puncture (CLP) of moderate severity. However, we found that the beneficial role of mast cells in this setting can occur independently of mast cell-derived tumor necrosis factor. By contrast, using mast cell-engrafted C57BL/6-Kit(W-sh/W-sh) mice, we found that mast cell-derived tumor necrosis factor can increase mortality during severe CLP and can also enhance bacterial growth and hasten death after intraperitoneal inoculation of Salmonella typhimurium. In WBB6F(1)-Kit(W-sh/W-sh) mice, mast cells enhanced survival during moderately severe CLP but did not significantly change the survival observed in severe CLP. Our findings in three types of genetically mast cell-deficient mice thus support the hypothesis that, depending on the circumstances (including mouse strain background, the nature of the mutation resulting in a mast cell deficiency, and type and severity of infection), mast cells can have either no detectable effect or opposite effects on survival during bacterial infections, eg, promoting survival during moderately severe CLP associated with low mortality but, in C57BL/6-Kit(W-sh/W-sh) mice, increasing mortality during severe CLP or infection with S. typhimurium.