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A case study of a 56-year-old woman was admitted to this hospital in the spring of 2020, during the initial surge of the coronavirus disease 2019 (Covid-19) pandemic in Boston. Topics include the patient began isolating at home with her teenage son, working from home, and having groceries delivered; and frontal headache developed, along with a dry cough that was associated with a self-limited episode of chest pain.

• Fungal recognition by C-type lectin receptors are critical for proper immune response. • Innate effector pathways contribute to fungal killing and recruit immune cells. • CLR regulation and signaling can be leveraged for novel treatment strategies. The innate immune system is critical to proper host defense against fungal pathogens, which is highlighted by increased susceptibility to invasive disease in immunocompromised patients. Innate cells (e.g. macrophages, neutrophils, dendritic cells, eosinophils) are equipped with intricate cell machinery to detect invading fungi and facilitate fungal killing, recruit additional immune cells, and direct the adaptive immune system responses. Understanding the mechanisms that govern a protective response will enable the development of novel treatment strategies. This review focuses on recent insights of signaling and regulation of C-type lectin receptors and their effector mechanisms enabling an effective host antifungal immunity. [ABSTRACT FROM AUTHOR]

Abstract Phagocytosis is an essential step in the innate immune response to invasive fungal infections. This process is carried out by a proverbial "village" of professional phagocytic cells, which have evolved efficient machinery to recognize and ingest pathogens, namely macrophages, neutrophils and dendritic cells. These innate immune cells drive early cytokine production, fungicidal activity, antigen presentation and activation of the adaptive immune system. Despite the development of antifungal agents with potent activity, the biological activity of professional phagocytic innate immune cells has proven indispensable in protecting a host from invasive fungal infections. Additionally, an emerging body of evidence suggests non-professional phagocytes, such as airway epithelial cells, carry out phagocytosis and may play a critical role in the elimination of fungal pathogens. Here, we review recent advances of phagocytosis by both professional and non-professional phagocytes in response to fungal pathogens, with a focus on invasive aspergillosis as a model disease. [ABSTRACT FROM AUTHOR]

The article explains the need to focus on diagnostic reasoning in internal medicine training. Physicians are advised to enhance their competency in internal medicine training in order to help them the challenges in the health care environment. Some recommendations for rebuilding the focus on diagnostic reasoning in internal medicine training are enumerated, including changing the teaching conferences and structure of teaching rounds.

The article describes the case of a 76-year-old man who presented with fever, worsening renal function and confusion upon admission to the Massachusetts General Hospital. The patient has a history of chronic renal disease, renal obstruction and recurrent urinary tract infections. It discusses the viral infections that cause meningoencephalitis. The final diagnosis for the patient was West Nile virus meningoencephalitis.

The application of advanced imaging techniques to fundamental questions in immunology has provided insight into dendritic cell function and has challenged dogma created using static imaging of lymphoid tissue. The history of dendritic cell biology has a storied past and is tightly linked to imaging. The development of imaging techniques that emphasize live cell imaging in situ has provided not only breath-taking movies, but also novel insights into the importance of spatiotemporal relationships between antigen presenting cells and T cells. This review serves to provide a primer on two-photon microscopy, TirF microscopy, spinning disk confocal microscopy and optical trapping and provides selective examples of insights gained from these tools on dendritic cell biology. [ABSTRACT FROM AUTHOR]

We report two cases of fatal hepatic failure in patients who received matched unrelated bone marrow transplantation. Both patients presented with high fevers, abnormal liver functions tests, and hypodense lesions in the liver by CT scan. Histologic examination of postmortem liver samples demonstrated extensive necrosis, and immunohistochemistry was positive for adenovirus. [ABSTRACT FROM AUTHOR]

The principal components of both MHC class I and class II antigen processing and presentation pathways are well known. In dendritic cells, these pathways are tightly regulated by Toll-like-receptor signalling and include features, such as cross-presentation, that are not seen in other cell types. However, the exact mechanisms involved in the subcellular trafficking of antigens remain poorly understood and in some cases are controversial. Recent data suggest that diverse cellular machineries, including autophagy, participate in antigen processing and presentation, although their relative contributions remain to be fully elucidated. Here, we highlight some emerging themes of antigen processing and presentation that we think merit further attention. [ABSTRACT FROM AUTHOR]

We describe 2 patients who presented to a health care facility with abdominal abscesses years after undergoing laparoscopic cholecystectomy that was complicated by gallstone spillage. In both patients, sample cultures yielded Actinomyces species and enteric organisms. In 1 patient, crystallographic analysis of abscess debris confirmed the presence of gallstones. Actinomyces species is a rare cause of abdominal abscesses that should be considered in this patient population. [ABSTRACT FROM AUTHOR]

A patient with acquired immune deficiency syndrome presented with babesiosis 6 months after presumed tick exposure. Despite initial treatment with azithromycin and atovaquone, followed by quinine and clindamycin, he experienced an increasing parasite load. Finally, red blood cell exchange transfusion, anti-Babesia therapy, and the addition of atovaquone-proguanil to the treatment regimen led to symptomatic improvement and elimination of parasitemia. Low-level parasitemia recurred 20 weeks later and was eradicated by administration of atovaquone-proguanil monotherapy. Atovaquone-proguanil appears to have activity against babesiosis and should be studied as a potential therapy for patients with refractory babesiosis. [ABSTRACT FROM AUTHOR]

Residency training is a profound experience that greatly influences the career trajectory of every trainee. Currently, residency programs focus heavily (or almost exclusively) on the acquisition of medical knowledge and fail to foster intellectual curiosity and introduce residents to careers in investigation. We share 3 programs embedded in residency training where this focus is shifted with an emphasis on prompting intellectual curiosity and exciting residents about careers in investigation to revitalize the physician-scientist workforce. [ABSTRACT FROM AUTHOR]

The article discusses the role of antigen-presenting dendritic cells (DC) in recognizing pathogens and activating and communicating with other cells of the immune system. The author cites the interaction of DC with antigen-specific T cells within the lymph node, which can be viewed using 2-photon microscopy. Laboratory manipulations provide a way to differentiate DC ex vivo using synthetic cytokines.

The association between treatment of acute COVID-19 with nirmatrelvir−ritonavir (N-R) and virologic rebound (VR) is uncertain. This observational cohort study in a multicenter health care system compared the frequency of VR in patients who received 5 days of N-R treatment versus those who received no COVID-19 therapy. Visual Abstract. SARS-CoV-2 Virologic Rebound With Nirmatrelvir–Ritonavir Therapy: The association between treatment of acute COVID-19 with nirmatrelvir−ritonavir (N-R) and virologic rebound (VR) is uncertain. This observational cohort study in a multicenter health care system compared the frequency of VR in patients who received 5 days of N-R treatment versus those who received no COVID-19 therapy. Background: Data are conflicting regarding an association between treatment of acute COVID-19 with nirmatrelvir−ritonavir (N-R) and virologic rebound (VR). Objective: To compare the frequency of VR in patients with and without N-R treatment for acute COVID-19. Design: Observational cohort study. Setting: Multicenter health care system in Boston, Massachusetts. Participants: Ambulatory adults with acute COVID-19 with and without use of N-R. Intervention: Receipt of 5 days of N-R treatment versus no COVID-19 therapy. Measurements: The primary outcome was VR, defined as either a positive SARS-CoV-2 viral culture result after a prior negative result or 2 consecutive viral loads above 4.0 log 10 copies/mL that were also at least 1.0 log 10 copies/mL higher than a prior viral load below 4.0 log 10 copies/mL. Results: Compared with untreated persons (n = 55), those taking N-R (n = 72) were older, received more COVID-19 vaccinations, and more commonly had immunosuppression. Fifteen participants (20.8%) taking N-R had VR versus 1 (1.8%) who was untreated (absolute difference, 19.0 percentage points [95% CI, 9.0 to 29.0 percentage points]; P = 0.001). All persons with VR had a positive viral culture result after a prior negative result. In multivariable models, only N-R use was associated with VR (adjusted odds ratio, 10.02 [CI, 1.13 to 88.74]; P = 0.038). Virologic rebound was more common among those who started therapy within 2 days of symptom onset (26.3%) than among those who started 2 or more days after symptom onset (0%) (P = 0.030). Among participants receiving N-R, those who had VR had prolonged shedding of replication-competent virus compared with those who did not have VR (median, 14 vs. 3 days). Eight of 16 participants (50% [CI, 25% to 75%]) with VR also reported symptom rebound; 2 were completely asymptomatic. No post-VR resistance mutations were detected. Limitations: Observational study design with differences between the treated and untreated groups; positive viral culture result was used as a surrogate marker for risk for ongoing viral transmission. Conclusion: Virologic rebound occurred in approximately 1 in 5 people taking N-R, often without symptom rebound, and was associated with shedding of replication-competent virus. Primary Funding Source: National Institutes of Health. [ABSTRACT FROM AUTHOR]

The growing complexities of clinical medicine and biomedical research have clouded the career path for physician-scientists. In this perspective piece, we address one of the most opaque career stage transitions along the physician-scientist career path, the transition from medical school to research-focused internal medicine residency programs, or physician-scientist training programs (PSTPs). We present the perspectives of medical scientist training program (MSTP) and PSTP directors on critical features of PSTPs that can help trainees proactively align their clinical and scientific training for successful career development. We aim to provide both trainees and MSTP directors with a conceptual framework to better understand and navigate PSTPs. We also offer interview-specific questions to help trainees gather data and make informed decisions in choosing a residency program that best supports their career. [ABSTRACT FROM AUTHOR]

The endemic fungal infection, coccidioidomycosis, occurs after inhalation of one or very few Coccidioides spp. spores. Infections produce diverse clinical manifestations, ranging from insignificant to extremely destructive, even fatal. Approaches to understanding this range of consequences have traditionally categorized patients into a small number of groups (asymptomatic, uncomplicated self-limited, fibro-cavitary, and extra-thoracic disseminated) and then looked for immunologic differences among them. Recently, variants within genes of innate pathways have been found to account, in part, for infections that result in disseminated disease. This discovery raises the very attractive theory that, in patients without severe immunosuppression, much of the disease spectrum can be accounted for by various combinations of such deleterious variants in innate pathways. In this review, we summarize what is known about genetic determinants that are responsible for the severity of coccidioidal infections and how complex innate genetic differences among different people might account for the spectrum of disease observed clinically. [ABSTRACT FROM AUTHOR]

We enrolled 7 individuals with recurrent symptoms or antigen test conversion following nirmatrelvir-ritonavir treatment. High viral loads (median 6.1 log10 copies/mL) were detected after rebound for a median of 17 days after initial diagnosis. Three had culturable virus for up to 16 days after initial diagnosis. No known resistance-associated mutations were identified. [ABSTRACT FROM AUTHOR]

The lung epithelial lining serves as the primary barrier to inhaled environmental toxins, allergens, and invading pathogens. Pulmonary fungal infections are devastating and carry high mortality rates, particularly in those with compromised immune systems. While opportunistic fungi infect primarily immunocompromised individuals, endemic fungi cause disease in immune competent and compromised individuals. Unfortunately, in the case of inhaled fungal pathogens, the airway epithelial host response is vastly understudied. Furthering our lack of understanding, very few studies utilize primary human models displaying pseudostratified layers of various epithelial cell types at air-liquid interface. In this review, we focus on the diversity of the human airway epithelium and discuss the advantages and disadvantages of oncological cell lines, immortalized epithelial cells, and primary epithelial cell models. Additionally, the responses by human respiratory epithelial cells to invading fungal pathogens will be explored. Future investigations leveraging current human in vitro model systems will enable identification of the critical pathways that will inform the development of novel vaccines and therapeutics for pulmonary fungal infections. [ABSTRACT FROM AUTHOR]

The development of invasive aspergillosis is a feared complication for immunocompromised patients. Despite the use of antifungal agents with excellent bioactivity, the morbidity and mortality rates for invasive aspergillosis remain unacceptably high. Defects within the innate immune response portend the highest risk for patients, but detailed knowledge of molecular pathways in neutrophils and macrophages in response to this fungal pathogen is lacking. Phagocytosis of fungal spores is a key step that places the pathogen into a phagosome, a membrane-delimited compartment that undergoes maturation and ultimately delivers antigenic material to the class II MHC pathway. We review the role of Toll-like receptor 9 (TLR9) in phagosome maturation of Aspergillus fumigates-containing phagosomes. Advanced imaging modalities and the development of fungal-like particles are promising tools that will aid in the dissection of the molecular mechanism to fungal immunity. [ABSTRACT FROM AUTHOR]

The impact of coronavirus disease 2019 vaccination on viral characteristics of breakthrough infections is unknown. In this prospective cohort study, incidence of severe acute respiratory syndrome coronavirus 2 infection decreased following vaccination. Although asymptomatic positive tests were observed following vaccination, the higher cycle thresholds, repeat negative tests, and inability to culture virus raise questions about their clinical significance. [ABSTRACT FROM AUTHOR]

The field of infectious diseases currently takes a reactive approach and treats infections as they present in patients. Although certain populations are known to be at greater risk of developing infection (eg, immunocompromised), we lack a systems approach to define the true risk of future infection for a patient. Guided by impressive gains in "omics" technologies, future strategies to infectious diseases should take a precision approach to infection through identification of patients at intermediate and high-risk of infection and deploy targeted preventative measures (ie, prophylaxis). The advances of high-throughput immune profiling by multiomics approaches (ie, transcriptomics, epigenomics, metabolomics, proteomics) hold the promise to identify patients at increased risk of infection and enable risk-stratifying approaches to be applied in the clinic. Integration of patient-specific data using machine learning improves the effectiveness of prediction, providing the necessary technologies needed to propel the field of infectious diseases medicine into the era of personalized medicine. [ABSTRACT FROM AUTHOR]

Coccidioidomycosis, otherwise known as Valley Fever, is caused by the dimorphic fungi Coccidioides immitis and C. posadasii. While most clinical cases present with self-limiting pulmonary infection, dissemination of Coccidioides spp. results in prolonged treatment and portends higher mortality rates. While the structure, genome, and niches for Coccidioides have provided some insight into the pathogenesis of disease, the underlying immunological mechanisms of clearance or inability to contain the infection in the lung are poorly understood. This review focuses on the known innate and adaptive immune responses to Coccidioides and highlights three important areas of uncertainty and potential approaches to address them. Closing these gaps in knowledge may enable new preventative and therapeutic strategies to be pursued. [ABSTRACT FROM AUTHOR]

The article discusses strategies for integrating physician-scientist research and development into clinical training programs which were implemented in three academic medical centers in the U.S. Topics discussed include physician-scientist training programs (PSTPs) for trainees, funding opportunities for sustaining successful physician-scientist pipelines, and metrics of success of physician-scientist development programs.

Tetraspanins are a family of proteins possessing four transmembrane domains that help in lateral organization of plasma membrane proteins. These proteins interact with each other as well as other receptors and signaling proteins, resulting in functional complexes called "tetraspanin microdomains." Tetraspanins, including CD82, play an essential role in the pathogenesis of fungal infections. Dectin-1, a receptor for the fungal cell wall carbohydrate β-1,3-glucan, is vital to host defense against fungal infections. The current study identifies a novel association between tetraspanin CD82 and Dectin-1 on the plasma membrane of Candida albicans-containing phagosomes independent of phagocytic ability. Deletion of CD82 in mice resulted in diminished fungicidal activity, increased C. albicans viability within macrophages, and decreased cytokine production (TNF-α, IL-1β) at both mRNA and protein level in macrophages. Additionally, CD82 organized Dectin-1 clustering in the phagocytic cup. Deletion of CD82 modulates Dectin-1 signaling, resulting in a reduction of Src and Syk phosphorylation and reactive oxygen species production. CD82 knockout mice were more susceptible to C. albicans as compared with wild-type mice. Furthermore, patient C. albicans-induced cytokine production was influenced by two human CD82 single nucleotide polymorphisms, whereas an additional CD82 single nucleotide polymorphism increased the risk for candidemia independent of cytokine production. Together, these data demonstrate that CD82 organizes the proper assembly of Dectin-1 signaling machinery in response to C. albicans. [ABSTRACT FROM AUTHOR]

Background: Several specialty societies participate in the Choosing Wisely (CW) campaign in an attempt to reduce waste in health care spending. We surveyed internal medicine (IM) residents with an objective of classifying knowledge of and confidence in using the American Society of Hematology (ASH) CW principles in hemostasis, thrombosis, and non-malignant hematology. Methods: Multi-institutional study of IM residents at 5 academic training programs in the United States. A 10-question, case-based multiple choice test, with each question accompanied by a 5-point Likert-scale confidence assessment, was distributed electronically. Responses were summarized with frequencies and percentages or medians and ranges, as appropriate. Two sample t-tests or Wilcoxon rank-sum tests were used to compare confidence and knowledge scores. Results: Of 892 IM residents, 174 (19.5%) responded to all questions. Overall, residents answered a median of 7 of 10 questions correctly (range 2–10) and median resident confidence in their responses was 3.1 (on a 5-point scale). Correct responses were significantly associated with higher confidence for all but one question. Having a hematology rotation experience was significantly associated with more correct responses and with higher confidence (p = 0.001 and p<0.001, respectively). Conclusions: IM residents at several academic hospitals have variable knowledge of ASH-CW guidelines in thrombosis and hemostasis/non-malignant hematology. Residents who have done hematology rotations, particularly a hematology consult rotation, were more likely to answer questions correctly and to be more confident that their answers were correct. Adequate clinical exposure and training in cost-effective care is essential to train clinicians who are cost-conscious in any specialty. [ABSTRACT FROM AUTHOR]

Invasive candidiasis remains one of the most serious community and healthcare-acquired infections worldwide. ConventionalCandidadetection methods based on blood and plate culture are time-consuming and require at least 2–4 days to identify variousCandidaspecies. Despite considerable advances for candidiasis detection, the development of simple, compact and portable point-of-care diagnostics for rapid and precise testing that automatically performs cell lysis, nucleic acid extraction, purification and detection still remains a challenge. Here, we systematically review most prominent conventional and nonconventional techniques for the detection of variousCandidaspecies, includingCandidastaining, blood culture, serological testing and nucleic acid-based analysis. We also discuss the most advanced lab on a chip devices for candida detection. [ABSTRACT FROM PUBLISHER]

Lentiviral vectors (LVVs) are powerful genetic tools that are being used with greater frequency in biomedical laboratories and clinical trials. Adverse events reported from initial clinical studies provide a basis for risk assessment of occupational exposures, yet many questions remain about the potential harm that LVVs may cause. We review those risks and provide a framework for principal investigators, Institutional Biosafety Committees, and occupational health professionals to assess and communicate the risks of exposure to staff. We also provide recommendations to federal research and regulatory agencies for tracking LVV exposures to evaluate long-term outcomes. U.S. Food and Drug Administration approved antiviral drugs for HIV have theoretical benefits in LVV exposures, although evidence to support their use is currently limited. If treatment is appropriate, we recommend a 7-day treatment with an integrase inhibitor with or without a reverse transcriptase inhibitor within 72 hours of exposure. [ABSTRACT FROM AUTHOR]

Dectin-1 and TLR9 play distinct roles in the recognition and induction of innate immune responses to Aspergillus fumigatus and Candida albicans. Dectin-1 is a receptor for the major fungal cell wall carbohydrate β-1,3 glucan that induces inflammatory cytokines and controls phagosomal maturation through spleen tyrosine kinase activation. TLR9 is an endosomal TLR that also modulates the inflammatory cytokine response to fungal pathogens. In this study, we demonstrate that β-1,3 glucan beads are sufficient to induce dynamic redistribution and accumulation of cleaved TLR9 to phagosomes. Trafficking of TLR9 to A. fumigatus and C. albicans phagosomes requires Dectin-1 recognition. Inhibition of phagosomal acidification blocks TLR9 accumulation on phagosomes containing β-1,3 glucan beads. Dectin-1-mediated spleen tyrosine kinase activation is required for TLR9 trafficking to β-1,3 glucan-, A. fumigatus-, and C. albicans-containing phagosomes. In addition, Dectin-1 regulates TLR9-dependent gene expression. Collectively, our study demonstrates that recognition of β-1,3 glucan by Dectin-1 triggers TLR9 trafficking to β-1,3 glucan-containing phagosomes, which may be critical in coordinating innate antifungal defense. [ABSTRACT FROM AUTHOR]

The article presents a case study of 43-year-old man who was admitted to the hospital due to altered mental status and has a history of alcohol-use disorder. Topics include the magnetic resonance imaging (MRI) performed which revealed lateral ventricles enlargement and periventricular hyperintensity reflecting the transependymal flow of the cerebrospinal fluid (CSF), the diagnosis of obstructive hydrocephalus, and the incidence of fungal infections.

The contribution of human neutrophils to the protection against fungal infections by Aspergillus fumigatus is essential but not fully understood. Whereas healthy people can inhale spores of A. fumigatus without developing disease, neutropenic patients and those receiving immunosuppressive drugs have a higher incidence of invasive fungal infections. To study the role of neutrophils in protection against A. fumigatus infections, we developed an in vitro assay in which the interactions between human neutrophils and A. fumigatus were observed in real time, at single-cell resolution, in precisely controlled conditions. We measured the outcomes of neutrophil-fungus interactions and found that human neutrophils have a limited ability to migrate toward A. fumigatus and block the growth of A. fumigatus conidia (proportion with growth blocked, 69%). The blocking ability of human neutrophils increased to 85.1% when they were stimulated by uniform concentrations of fMLP and was enhanced further, to 99.4%, in the presence of chemoattractant gradients. Neutrophils from patients receiving immunosuppressive treatment after transplantation were less effective against the fungus than those from healthy donors, and broader heterogeneity exists between patients, compared with healthy individuals. Further studies using this microfluidic platform will help understand the relevance of innate immune deficiencies responsible for the higher risk of fungal infections in patients with immunosuppressive disease. [ABSTRACT FROM AUTHOR]

Beyond its well-documented role in reproduction, embryogenesis and maintenance of body tissues, vitamin A has attracted considerable attention due to its immunomodulatory effects on both the innate and the adaptive immune responses. In infectious diseases, vitamin A has been shown to have a host-protective effect in infections of bacterial, viral or protozoan origin. Nevertheless, its impact in fungal infections remains unknown. Meanwhile, the frequency of invasive mycoses keeps on growing, with Candida albicans being the major opportunistic fungal pathogen and associated with high mortality. In the present work, we explored the impact of all-trans retinoic acid (atRA), the most active metabolite of vitamin A, on the innate immune response against C. albicans in human monocytes. Our results show a strong immunomodulatory role for atRA, leading to a significant down-regulation of the fungi-induced expression and secretion of the pro-inflammatory cytokines TNFα, IL6 and IL12. Moreover, atRA significantly suppressed the expression of Dectin-1, a major fungal pattern recognition receptor, as well as the Dectin-1-dependent cytokine production. Both RAR-dependent and RAR-independent mechanisms seem to play a role in the atRA-mediated immunomodulation. Our findings open a new direction to elucidate the role of vitamin A on the immune function during fungal infections. [ABSTRACT FROM AUTHOR]

Autophagy has been postulated to play role in mammalian host defense against fungal pathogens, although the molecular details remain unclear. Here, we show that primary macrophages deficient in the autophagic factor LC3 demonstrate diminished fungicidal activity but increased cytokine production in response to Candida albicans stimulation. LC3 recruitment to fungal phagosomes requires activation of the fungal pattern receptor dectin-1. LC3 recruitment to the phagosome also requires Syk signaling but is independent of all activity by Toll-like receptors and does not require the presence of the adaptor protein Card9. We further demonstrate that reactive oxygen species generation by NADPH oxidase is required for LC3 recruitment to the fungal phagosome. These observations directly link LC3 to the inflammatory pathway against C. albicans in macrophages. [ABSTRACT FROM AUTHOR]

Autophagy has been postulated to play role in mammalian host defense against fungal pathogens, although the molecular details remain unclear. Here, we show that primary macrophages deficient in the autophagic factor LC3 demonstrate diminished fungicidal activity but increased cytokine production in response to Candida albicans stimulation. LC3 recruitment to fungal phagosomes requires activation of the fungal pattern receptor dectin-1. LC3 recruitment to the phagosome also requires Syk signaling but is independent of all activity by Toll-like receptors and does not require the presence of the adaptor protein Card9. We further demonstrate that reactive oxygen species generation by NADPH oxidase is required for LC3 recruitment to the fungal phagosome. These observations directly link LC3 to the inflammatory pathway against C. albicans in macrophages. [ABSTRACT FROM AUTHOR]

Candida glabrata currently ranks as the second most frequent cause of invasive candidiasis. Our previous work has shown that C. glabrata is adapted to intracellular survival in macrophages and replicates within non-acidified late endosomal-stage phagosomes. In contrast, heat killed yeasts are found in acidified matured phagosomes. In the present study, we aimed at elucidating the processes leading to inhibition of phagosome acidification and maturation. We show that phagosomes containing viable C. glabrata cells do not fuse with pre-labeled lysosomes and possess low phagosomal hydrolase activity. Inhibition of acidification occurs independent of macrophage type (human/murine), differentiation (M1-/M2-type) or activation status (vitamin D3 stimulation). We observed no differential activation of macrophage MAPK or NFκB signaling cascades downstream of pattern recognition receptors after internalization of viable compared to heat killed yeasts, but Syk activation decayed faster in macrophages containing viable yeasts. Thus, delivery of viable yeasts to non-matured phagosomes is likely not triggered by initial recognition events via MAPK or NFκB signaling, but Syk activation may be involved. Although V-ATPase is abundant in C. glabrata phagosomes, the influence of this proton pump on intracellular survival is low since blocking V-ATPase activity with bafilomycin A1 has no influence on fungal viability. Active pH modulation is one possible fungal strategy to change phagosome pH. In fact, C. glabrata is able to alkalinize its extracellular environment, when growing on amino acids as the sole carbon source in vitro. By screening a C. glabrata mutant library we identified genes important for environmental alkalinization that were further tested for their impact on phagosome pH. We found that the lack of fungal mannosyltransferases resulted in severely reduced alkalinization in vitro and in the delivery of C. glabrata to acidified phagosomes. Therefore, protein mannosylation may play a key role in alterations of phagosomal properties caused by C. glabrata. [ABSTRACT FROM AUTHOR]

Elimination of fungal pathogens by phagocytes requires phagosome maturation, a process that involves the recruitment and fusion of intracellular proteins. The role of Dectin-1, a β-1,3-glucan receptor, critical for fungal recognition and triggering of Th17 responses, to phagosomal maturation has not been defined. We show that GFP-Dectin-1 translocates to the fungal phagosome, but its signal decays after 2 h. Inhibition of acidification results in retention of GFP-Dectin-1 to phagosome membranes highlighting the requirement for an acidic pH. Following β-1,3-glucan recognition, GFP-Dectin-1 undergoes tyrosine phosphorylation by Src kinases with subsequent Syk activation. Our results demonstrate that Syk is activated independently of intraphagosomal pH. Inhibition of Src or Syk results in prolonged retention of GFP-Dectin-1 to the phagosome signifying a link between Syk and intraphagosomal pH. β-1,3-glucan phagosomes expressing a signaling incompetent Dectin-1 failed to mature as demonstrated by prolonged Dectin-1 retention, presence of Rab5B, failure to acquire LAMP-1 and inability to acidify. Phagosomes containing Candida albicans also require Dectin-1-dependent Syk activation for phagosomal maturation. Taken together, these results support a model where Dectin-1 not only controls internalization of β-1,3-glucan containing cargo and triggers proinflammatory cytokines, but also acts as a master regulator for subsequent phagolysosomal maturation through Syk activation. [ABSTRACT FROM AUTHOR]

Chronic granulomatous disease, an inherited disorder of the NADPH oxidase in which phagocytes are defective in the generation of superoxide anion and downstream reactive oxidant species, is characterized by severe bacterial and fungal infections and excessive inflammation. Although NADPH oxidase isoforms exist in several lineages, reactive oxidant generation is greatest in neutrophils, where NADPH oxidase has been deemed vital for pathogen killing. In contrast, the function and importance of NADPH oxidase in macrophages are less clear. Therefore, we evaluated susceptibility to pulmonary aspergillosis in globally NADPH oxidase-deficient mice versus transgenic mice with monocyte/macrophage-targeted NADPH oxidase activity. We found that the lethal inoculum was >100-fold greater in transgenic versus globally NADPH oxidase-deficient mice. Consistent with these in vivo results, NADPH oxidase in mouse alveolar macrophages limited germination of phagocytosed Aspergillus fumigatus spores. Finally, globally NADPH oxidase-deficient mice developed exuberant neutrophilic lung inflammation and proinflammatory cytokine responses to zymosan, a fungal cell wall-derived product composed principally of particulate β-glucans, whereas inflammation in transgenic and wild-type mice was mild and transient. Taken together, our studies identify a central role for monocyte/macrophage NADPH oxidase in controlling fungal infection and in limiting acute lung inflammation. [ABSTRACT FROM AUTHOR]

Abstract: Members of the fungal genus Fusarium are capable of manifesting in a multitude of clinical infections, most commonly in immunocompromised patients. In order to better understand the interaction between the fungus and host, we have developed the larvae of the greater wax moth, Galleria mellonella, as a heterologous host for fusaria. When conidia are injected into the haemocoel of this Lepidopteran system, both clinical and environmental isolates of the fungus are able to kill the larvae at 37 °C, although killing occurs more rapidly when incubated at 30 °C. This killing was dependent on several other factors besides temperature, including the Fusarium strain, the number of conidia injected, and the conidia morphology, where macroconidia are more virulent than their microconidia counterpart. There was a correlation in the killing rate of Fusarium spp. when evaluated in G. mellonella and a murine model. In vivo studies indicated G. mellonella haemocytes were capable of initially phagocytosing both conidial morphologies. The G. mellonella system was also used to evaluate antifungal agents, and amphotericin B was able to confer a significant increase in survival to Fusarium-infected larvae. The G. mellonella–Fusarium pathogenicity system revealed that virulence of Fusarium spp. is similar, regardless of the origin of the isolate, and that mammalian endothermy is a major deterrent for Fusarium infection and therefore provides a suitable alternative to mammalian models to investigate the interaction between the host and this increasingly important fungal pathogen. [Copyright &y& Elsevier]

Repulsive guidance molecule (RGM) family members RGMa, RGMb/Dragon, and RGMc/hemojuvelin were found recently to act as bone morphogenetic protein (BMP) coreceptors that enhance BMP signaling activity. Although our previous studies have shown that hemojuvelin regulates hepcidin expression and iron metabolism through the BMP pathway, the role of the BMP signaling mediated by Dragon remains largely unknown. We have shown previously that Dragon is expressed in neural cells, germ cells, and renal epithelial cells. In this study, we demonstrate that Dragon is highly expressed in macrophages. Studies with RAW264.7 and J774 macrophage cell lines reveal that Dragon negatively regulates IL-6 expression in a BMP ligand-dependent manner via the p38 MAPK and Erk1/2 pathways but not the Smad1/5/8 pathway. We also generated Dragon knockout mice and found that IL-6 is upregulated in macrophages and dendritic cells derived from whole lung tissue of these mice compared with that in respective cells derived from wild-type littermates. These results indicate that Dragon is an important negative regulator of IL-6 expression in immune cells and that Dragon-deficient mice may be a useful model for studying immune and inflammatory disorders. [ABSTRACT FROM AUTHOR]

The application of live cell imaging allows direct visualization of the dynamic interactions between cells of the immune system. Some preliminary observations challenge long-held beliefs about immune responses to microorganisms; however, the lack of spatial and temporal control between the phagocytic cell and microbe has rendered focused observations into the initial interactions of host response to pathogens difficult. This paper outlines a method that advances live cell imaging by integrating a spinning disk confocal microscope with an optical trap, also known as an optical tweezer, in order to provide exquisite spatial and temporal control of pathogenic organisms and place them in proximity to host cells, as determined by the operator. Polymeric beads and live, pathogenic organisms (Candida albicans and Aspergillus fumigatus) were optically trapped using non-destructive forces and moved adjacent to living cells, which subsequently phagocytosed the trapped particle. High resolution, transmitted light and fluorescence-based movies established the ability to observe early events of phagocytosis in living cells. To demonstrate the broad applicability of this method to immunological studies, anti-CD3 polymeric beads were also trapped and manipulated to form synapses with T cells in vivo, and time-lapse imaging of synapse formation was also obtained. By providing a method to exert fine control of live pathogens with respect to immune cells, cellular interactions can be captured by fluorescence microscopy with minimal perturbation to cells and can yield powerful insight into early responses of innate and adaptive immunity. [ABSTRACT FROM AUTHOR]

Introduction: Infection and malignancy often have common characteristics which render the differential diagnosis for a prolonged fever difficult. Imaging and tissue biopsy are crucial in making a correct diagnosis, though differentiating between chronic osteomyelitis and malignancy is not always straightforward as they possess many overlapping features.Case Presentation: A 52-year-old Caucasian man was treated with antibiotics for his diabetic foot infection after a superficial culture showed Staphylococcus aureus. He had persistent fevers for several weeks and later developed acute onset of back pain which was treated with several courses of antibiotics. Radiographic and pathological findings were atypical, and a diagnosis of Hodgkin's lymphoma was made 12 weeks later.Conclusion: Clinicians should maintain a suspicion for Hodgkin's lymphoma or other occult malignancy when features of presumed osteomyelitis are atypical. Chronic vertebral osteomyelitis in particular often lacks features common to acute infectious disease processes, and the chronic lymphocytic infiltrates seen on histopathology have very similar features to Hodgkin's lymphoma, highlighting a similar inflammatory microenvironment sustained by both processes. [ABSTRACT FROM AUTHOR]

An important role of IgG antibodies in the defense against microbial infections is to promote the ingestion and killing of microbes by phagocytes. Here, we developed in vivo and in vitro approaches to ask whether opsonization of particles with IgG enhances intracellular targeting of lysosomes to phagosomes. To eliminate the effect of igG on the ingestion process, cells were exposed to latex beads at 15–20°C, which allows engulfment of both IgG-coated and uncoated beads but prevents the fusion of lysosomes with phagosomes. Upon shifting the temperature to 37°C, phagosomes containing IgG beads matured significantly faster into phagolysosomes as judged by colocalization with lysosomal markers. The IgG effect was independent of other particle-associated antigens or serum factors. Lysosome/phagosome attachment was also quantified biochemically with a cytosol-dependent scintillation proximity assay. Interactions were enhanced significantly in reactions containing cytosol from mouse macrophages that had been exposed to IgG-coated beads, indicating that IgG signaling modulates the cytosolic-targeting machinery. Similar results were obtained with cytosol from primary human monocytes, human U-937 histiocytic lymphoma cells and from Chinese hamster ovary (CHO) cells transfected with a human IgG (Fcγ) receptor. IgG-induced activation is shown to affect the actin-dependent tethering/docking stage of the targeting process and to proceed through a pathway involving protein kinase C. These results provide a rare example of an extracellular signal controlling membrane targeting on the level of tethering and docking. We propose that this pathway contributes to the role of antibodies in the protection against microbial infections. [ABSTRACT FROM AUTHOR]

The subcellular localization of the cluster of differentiation 63 (CD63) tetraspanin and its interaction with the class II MHC antigen presentation pathway were examined in the context of phagocytosis by live cell imaging, by using monomeric red fluorescent protein-tagged mouse CD63 expressed in primary bone marrow-derived cell cultures. Upon phagocytosis of Cryptococcus neoformans and polystyrene beads, CD63 was recruited selectively to C. neoformans-containing phagosomes in a MyD88-independent acidification-dependent manner. Bead-containing phagosomes, within a C. neoformans-containing cell, acidified to a lesser extent and failed to recruit CD63 to a level detectable by microscopy. CD63 recruitment to yeast phagosomes occurred independently of class II MHC and LAMP-1. These observations indicate that the composition of distinct phagosomal compartments within the same cell is determined by phagosomal cargo and may affect the outcome of antigen processing and presentation. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) and macrophages are critical to innate and adaptive immunity to the intestinal bacterial microbiota. Here, we identify a myeloidderived mucosal DC in mice, which populates the entire lamina propria of the small intestine. Lamina propria DCs were found to depend on the chemokine receptor CX[sub 3]CR1 to form transepithelial dendrites, which enable the cells to directly sample luminal antigens. CX[sub 3]CR1 was also found to control the clearance of entero-invasive pathogens by DCs. Thus, CX[sub 3]CR1-dependent processes, which control host interactions of specialized DCs with commensal and pathogenic bacteria, may regulate immunological tolerance and inflammation. [ABSTRACT FROM AUTHOR]

Background: Primary spontaneous pneumothorax is a common disorder occurring in young adults without underlying lung disease. Although tobacco smoking is a well-documented risk factor for spontaneous pneumothorax, an association between electronic cigarette use (that is, vaping) and spontaneous pneumothorax has not been noted. We report a case of spontaneous pneumothoraces correlated with vaping.Case Presentation: An 18-year-old Caucasian man presented twice with recurrent right-sided spontaneous pneumothoraces within 2 weeks. He reported a history of vaping just prior to both episodes. Diagnostic testing was notable for a right-sided spontaneous pneumothorax on chest X-ray and computed tomography scan. His symptoms improved following insertion of a chest tube and drainage of air on each occasion. In the 2-week follow-up visit for the recurrent episode, he was asymptomatic and reported that he was no longer using electronic cigarettes.Conclusions: Providers and patients should be aware of the potential risk of spontaneous pneumothorax associated with electronic cigarettes. [ABSTRACT FROM AUTHOR]

The Infectious Diseases Society of America, HIV Medicine Association, and Pediatric Infectious Diseases Society are concerned by the continued decline in the number of infectious diseases trainees pursuing careers as physician-scientists and the attrition of junior and midcareer physician-scientists. The inability to replace the aging physician-scientist workforce will have a negative, long-lasting impact our biomedical research enterprise and its ability to drive the discovery of new treatments for important infectious diseases. We discuss policy recommendations for securing and optimizing the infectious diseases physician-scientist workforce in the areas of education, training, compensation, and mentorship, as well as ways to improve federal research funding, cross-sector collaboration, and workforce diversity. [ABSTRACT FROM AUTHOR]

A correction to the article "Modulatory role of vitamin A on the Candida albicans-induced immune response in human monocytes" that was published in the October 9, 2014 issue is presented.