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Group 2 innate lymphoid cells (ILC2s) have an important role in acute allergic lung inflammation. Given their distribution and function, lung ILC2s are hypothesized to coordinate epithelial responses to the external environment; however, how barrier survei

Group 2 innate lymphoid cells (ILC2s) and regulatory T (Treg) cells are systemically induced by helminth infection but also sustain metabolic homeostasis in adipose tissue and contribute to tissue repair during injury. Here we show that interleukin-33 (IL-33) mediates activation of ILC2s and Treg cells in resting adipose tissue, but also after helminth infection or treatment with IL-2. Unexpectedly, ILC2-intrinsic IL-33 activation was required for Treg cell accumulation invivo and was independent of ILC2 type 2 cytokines but partially dependent on direct co-stimulatory interactions via ICOSL-ICOS. IFN-γ inhibited ILC2 activation and Treg cell accumulation by IL-33 in infected tissue, as well as adipose tissue, where repression increased with aging and high-fat diet-induced obesity. IL-33 and ILC2s are central mediators of type 2 immune responses that promote tissue and metabolic homeostasis, and IFN-γ suppresses this pathway, likely to promote inflammatory responses and divert metabolic resources necessary to protect the host.

Eosinophils in visceral adipose tissue (VAT) have been implicated in metabolic homeostasis and the maintenance of alternatively activated macrophages (AAMs). The absence of eosinophils can lead to adiposity and systemic insulin resistance in experimental a

Gefapixant (MK-7264, RO4926219, AF-219) is a first-in-class P2X3 antagonists being developed to treat refractory or unexplained chronic cough. The initial single- and multiple-dose safety, tolerability, and pharmacokinetics of gefapixant at doses ranging from 7.5 to 1800 mg were assessed in four clinical trials. Following single-dose administration of 10-450 mg, the pharmacokinetic (PK) profile of gefapixant in plasma and urine demonstrated low inter-subject variability and a dose-proportional exposure. Following administration of multiple doses twice daily, the plasma exposures were dose-proportional at doses ranging from 7.5 to 50 mg and less than dose-proportional at doses ranging from 100 to 1800 mg. The time to mean peak drug concentration ranged from 2 to 3 h post-dose, and steady state was achieved by 7 days after dosing, with an accumulation ratio of approximately 2, comparing data from day 1 to steady state. The mean apparent terminal half-life ranged from 8.2 to 9.6 h. Gefapixant was primarily excreted unmodified in urine. Gefapixant was well tolerated following single-dose administration up to 1800 mg and multiple doses up to 1800 mg twice daily; there were no serious adverse events (AEs) reported. The most common AE reported was dysgeusia. The PK profile supports a twice-daily dosing regimen., (© 2024 Merck Sharp & Dohme LLC and The Authors. The Journal of Clinical Pharmacology published by Wiley Periodicals LLC on behalf of American College of Clinical Pharmacology.)

The eye, which is under constant exposure to environmental pathogens, has evolved various anatomic and immunological barriers critical to the protection of tissues lacking regenerative capacity, and the maintenance of a clear optic pathway essential to vision. By bypassing the ocular barriers, intravitreal (IVT) injection has become the mainstay for the delivery of drugs to treat conditions that affect the back of the eye. Both small molecules and biotherapeutics have been successfully administered intravitreally, and several drugs have been approved for the treatment of (wet) age-related macular degeneration and diabetic macular edema. However, IVT injection is an invasive procedure, which requires sufficient technical expertise from the healthcare professional administering the drug. Potential side effects include bleeding, retinal tear, cataracts, infection, uveitis, loss of vision, and increased ocular pressure. Pharmaceutical companies often differ in their drug development plan, including drug administration techniques, collection of ocular tissues and fluids, ophthalmology monitoring, and overall conduct of nonclinical and clinical studies. The present effort, under the aegis of the Innovation & Quality Ophthalmic Working Group, aims at understanding these differences, identifying pros and cons of the various approaches, determining the gaps in knowledge, and suggesting feasible good practices for nonclinical and early clinical IVT drug development., (© 2023 The Authors. Clinical and Translational Science published by Wiley Periodicals LLC on behalf of American Society for Clinical Pharmacology and Therapeutics.)

Gefapixant, a P2X3 receptor antagonist, has demonstrated efficacy in patients with refractory or unexplained chronic cough. We investigated the effect of renal impairment (RI) on the pharmacokinetics (PK) of gefapixant 50 mg in an open-label, single-dose study enrolling participants with moderate (n = 6) or severe (n = 6) RI, end-stage renal disease (ESRD; n = 6) under hemodialysis (HD) and non-HD conditions, and healthy matched controls (n = 6). Serial plasma and urine samples for gefapixant concentrations were collected at selected time points over 72 and 48 hours after dosing, respectively. Linear regression analysis predicted a 1.87-, 2.79-, and 3.76-fold higher exposure (area under the plasma concentration-time curve) for participants with mild, moderate, and severe RI, respectively, than that for healthy matched control participants. Categorical analysis exhibited a 2.98-, 4.43-, and 4.74-fold higher exposure for participants with moderate RI, severe RI, and ESRD, respectively, than that for healthy matched control participants. Apparent oral clearance and renal clearance was lower in participants with various degrees of RI, by 66% to 90%, compared with healthy matched control participants, explaining the increased gefapixant exposure with increasing degrees of renal impairment. Gefapixant area under the plasma concentration-time curve and maximum plasma concentration decreased by ≈25% under HD conditions compared to non-HD conditions. Single-dose administration of gefapixant was generally well tolerated in this study. The data from this trial informed the enrollment of phase 3 clinical trials that evaluated the efficacy and safety of gefapixant in >2000 participants with refractory or unexplained chronic cough. Those efficacy and safety data, combined with analysis of population pharmacokinetics from across the entire development program, will be used to evaluate the magnitude of the renal impairment effect in the refractory or unexplained chronic cough population and to determine any dose adjustment recommendations., (© 2022, The American College of Clinical Pharmacology.)

Gefapixant is a P2X3-receptor antagonist being developed for treatment of refractory or unexplained chronic cough. Four phase 1 studies were conducted in healthy participants that bridged the early-phase gefapixant formulation (F01) to the phase 3 (F04A) and intended commercial (F04B) formulations. In addition, food and proton pump inhibitor (PPI) coadministration effects on gefapixant exposure were assessed. The gefapixant free base formulation (F01) was used in the initial early-phase clinical studies. Adding citric acid to the F01 formulation (to generate F02) enhanced drug solubilization, resulting in similar bioavailability and mitigating food and gastric pH effects. The subsequently developed gefapixant citrate salt formulation (F04) achieved exposures that were comparable to F02 in the fed state (90%CIs of geometric mean ratios for area under the plasma concentration-time curve from time 0 extrapolated to infinity and maximum observed concentration were within 0.80 and 1.25) and were not meaningfully affected by food or PPIs (90%CIs of geometric mean ratios for area under the plasma concentration-time curve from time 0 extrapolated to infinity and maximum observed concentration were within 0.80 and 1.25). Minor compositional changes were made to generate the F04A and F04B formulations. In vitro dissolution studies were used to bridge F04 to F04A, and clinical bioequivalence was then established between F04A and F04B. These data support use of the proposed commercial gefapixant formulation without significant food and PPI effects., (© 2022 Merck Sharp and Dohme Corp. Clinical Pharmacology in Drug Development published by Wiley Periodicals LLC on behalf of American College of Clinical Pharmacology.)

Gefapixant (MK-7264) is a first-in-class, selective antagonist of the P2X3 purinergic receptor currently being investigated as a therapeutic agent for the treatment of refractory or unexplained chronic cough. In non-clinical studies, gefapixant was eliminated primarily by renal excretion of the parent drug. The objective of this study was to assess the disposition of gefapixant in humans. The absorption, metabolism, and excretion profiles of gefapixant were assessed after oral administration of a single dose of [ 14 C]gefapixant to six healthy adult males. Following a single-oral [ 14 C]gefapixant dose to healthy adult males, the mass balance was achieved, with 98.9% of the administered radioactivity recovered in urine and feces. Elimination of gefapixant occurred primarily via renal excretion of the intact drug (64%); metabolism was a minor pathway of elimination of gefapixant (12% and 2% recovered in urine and feces, respectively). Single-dose administration of [ 14 C]gefapixant 50 mg was generally well tolerated in healthy adult males. The fraction of the anticipated therapeutic oral dose of gefapixant absorbed is estimated to be at least 78%. Gefapixant is expected to be the major circulating drug-related material in plasma, and the majority of the dosed drug will be excreted unchanged in urine., (© 2022 The Authors. Pharmacology Research & Perspectives published by John Wiley & Sons Ltd, British Pharmacological Society and American Society for Pharmacology and Experimental Therapeutics.)

Gefapixant (MK-7264, AF-219) is a first-in-class P2X3 antagonist in development for refractory or unexplained chronic cough. Gefapixant is primarily cleared by renal excretion. To assess the importance of the multidrug and toxin extrusion protein 1 (MATE1) and MATE2K transporters in the elimination of gefapixant, a drug-drug interaction study was conducted evaluating the effect of coadministration of a single dose of pyrimethamine, a competitive inhibitor of MATE1 and MATE2K, on the single-dose pharmacokinetics of gefapixant in healthy participants. Safety and tolerability were also assessed. In this open-label, 2-period, fixed-sequence study, a 45-mg dose of gefapixant was administered to 12 participants in period 1. After a 7-day washout, a 50-mg dose of pyrimethamine was administered 3 hours before a 45-mg dose of gefapixant in period 2. Compared with the administration of gefapixant alone, concomitant dosing of gefapixant with pyrimethamine increased the total gefapixant plasma exposure (area under the plasma concentration-time curve from time 0 to infinity) by 24%, reduced gefapixant renal clearance by 30%, and increased gefapixant mean terminal half-life from 7.7 to 10.3 hours. The most frequently reported adverse events were dysgeusia, hypogeusia, and dry mouth; all adverse events were considered of mild intensity and resolved by the end of the study. These results support that MATE1 and/or MATE2K contribute to the renal clearance of gefapixant, but the effect of inhibition of these transporters on gefapixant pharmacokinetics is not considered clinically meaningful., (© 2021, The American College of Clinical Pharmacology.)

The perinatal period is a critical window for distribution of innate tissue-resident immune cells within developing organs. Despite epidemiologic evidence implicating the early-life environment in the risk for allergy, temporally controlled lineage tracing of group 2 innate lymphoid cells (ILC2s) during this period remains unstudied. Using complementary fate-mapping approaches and reporters for ILC2 activation, we show that ILC2s appeared in multiple organs during late gestation like tissue macrophages, but, unlike the latter, a majority of peripheral ILC2 pools were generated de novo during the postnatal window. This period was accompanied by systemic ILC2 priming and acquisition of tissue-specific transcriptomes. Although perinatal ILC2s were variably replaced across tissues with age, the dramatic increases in tissue ILC2s following helminth infection were mediated through local expansion independent of de novo generation by bone marrow hematopoiesis. We provide comprehensive temporally controlled fate mapping of an innate lymphocyte subset with notable nuances as compared to tissue macrophage ontogeny., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Group 2 innate lymphoid cells (ILC2s) are distributed systemically and produce type 2 cytokines in response to a variety of stimuli, including the epithelial cytokines interleukin (IL)-25, IL-33, and thymic stromal lymphopoietin (TSLP). Transcriptional profiling of ILC2s from different tissues, however, grouped ILC2s according to their tissue of origin, even in the setting of combined IL-25-, IL-33-receptor-, and TSLP-receptor-deficiency. Single-cell profiling confirmed a tissue-organizing transcriptome and identified ILC2 subsets expressing distinct activating receptors, including the major subset of skin ILC2s, which were activated preferentially by IL-18. Tissue ILC2 subsets were unaltered in number and expression in germ-free mice, suggesting that endogenous, tissue-derived signals drive the maturation of ILC2 subsets by controlling expression of distinct patterns of activating receptors, thus anticipating tissue-specific perturbations occurring later in life.

The recent discovery of innate lymphoid cells (ILCs), a major source of canonical T cell cytokines, has prompted significant interest into understanding the role of these novel cells in immune responses. Unlike T cells, ILCs lack antigen receptors, instead receiving activation from locally derived tissue signals. Group 2 ILCs (ILC2s), which express the genes encoding GATA-3, interleukin (IL)-4, IL-5, IL-9, and IL-13, are distributed throughout nonlymphoid tissues. Although ILC2s lack antigen receptors, there are considerable similarities that they share with their Th2 cell counterparts, including receptors, secreted signals, and key transcription factors. Here we describe a method of isolating ILC2s for analysis from peripheral tissues of the mouse. The approach consists of digesting and mechanically dissociating harvested organs followed by staining with fluorescently labeled antibodies for flow cytometry or cell sorting. We suggest panels of antibodies for each tissue that can be used as positive and negative markers to selectively separate ILC2s from other cells, and we demonstrate marker specificity with example cells from a "cytokine reporter" mouse strain.

Group 2 innate lymphoid cells (ILC2s) and CD4 + type 2 helper T cells (T H 2 cells) are defined by their similar effector cytokines, which together mediate the features of allergic immunity. We found that tissue ILC2s and T H 2 cells differentiated independently but shared overlapping effector function programs that were mediated by exposure to the tissue-derived cytokines interleukin 25 (IL-25), IL-33 and thymic stromal lymphopoietin (TSLP). Loss of these three tissue signals did not affect lymph node priming, but abrogated the terminal differentiation of effector T H 2 cells and adaptive lung inflammation in a T cell-intrinsic manner. Our findings suggest a mechanism by which diverse perturbations can activate type 2 immunity and reveal a shared local-tissue-elicited checkpoint that can be exploited to control both innate and adaptive allergic inflammation.

Group 2 innate lymphoid cells (ILC2s) have an important role in acute allergic lung inflammation. Given their distribution and function, lung ILC2s are hypothesized to coordinate epithelial responses to the external environment; however, how barrier surveillance is linked to ILC2 activation remains unclear. Here, we demonstrate that alveolar type II cells are the main source of interleukin (IL)-33 and thymic stromal lymphopoietin (TSLP) generated in response to chitin or migratory helminths. IL-33 and TSLP synergistically induce an interferon regulatory factor 4 (IRF4)-IL-9 program in ILC2s, and autocrine IL-9 promotes rapid IL-5 and IL-13 production required for optimal epithelial responses in the conducting airways. Thus, ILC2s link alveolar function to regulation of airway flow, revealing a key interaction between resident lymphoid and structural cells that might underlie similar organizational hierarchies in other organs.

Foreign body-induced granuloma is an uncommon yet clinically significant cause of hypercalcemia. The molecular mechanisms are uncertain, although extrarenal calcitriol production has been proposed. We describe severe hypercalcemia associated with increased levels of plasma calcitriol in a patient with HIV and local granulomatous reaction 5 years after injection of polymethylmethacrylate (PMMA) as dermal filler for cosmetic body sculpting. Extensive evaluation revealed no identifiable cause of increased calcitriol levels. Nuclear imaging was remarkable for diffuse uptake in the subcutaneous tissues of the buttocks. Subsequent muscle biopsy and immunohistochemical staining showed strong local expression of CYP27B1 within histiocytes surrounding globules of PMMA. This case highlights an unfortunate complication of dermal fillers and shows that inflammatory cells can express high levels of CYP27B1 even without frank granulomas. The growing trend of body contour enhancement using injectable fillers should raise suspicion for this cause of hypercalcemia in clinical practice. Patients with HIV who receive this treatment for lipodystrophy or other cosmetic purposes may have increased susceptibility to hypercalcemia in the setting of underlying chronic inflammation. This may be a concern when changing anti-retroviral therapy, since alterations in levels of HIV viremia may initiate or contribute to worsening hypercalcemia.

Type 2 innate lymphoid cells (ILC2s), an innate source of the type 2 cytokines interleukin (IL)-5 and -13, participate in the maintenance of tissue homeostasis. Although type 2 immunity is critically important for mediating metabolic adaptations to environmental cold, the functions of ILC2s in beige or brown fat development are poorly defined. We report here that activation of ILC2s by IL-33 is sufficient to promote the growth of functional beige fat in thermoneutral mice. Mechanistically, ILC2 activation results in the proliferation of bipotential adipocyte precursors (APs) and their subsequent commitment to the beige fat lineage. Loss- and gain-of-function studies reveal that ILC2- and eosinophil-derived type 2 cytokines stimulate signaling via the IL-4Rα in PDGFRα(+) APs to promote beige fat biogenesis. Together, our results highlight a critical role for ILC2s and type 2 cytokines in the regulation of adipocyte precursor numbers and fate, and as a consequence, adipose tissue homeostasis. PAPERCLIP:, (Copyright © 2015 Elsevier Inc. All rights reserved.)

Chitin, a polysaccharide constituent of many allergens and parasites, initiates innate type 2 lung inflammation through incompletely defined pathways. We show that inhaled chitin induced expression of three epithelial cytokines, interleukin-25 (IL-25), IL-33, and thymic stromal lymphopoietin (TSLP), which nonredundantly activated resident innate lymphoid type 2 cells (ILC2s) to express IL-5 and IL-13 necessary for accumulation of eosinophils and alternatively activated macrophages (AAMs). In the absence of all three epithelial cytokines, ILC2s normally populated the lung but failed to increase IL-5 and IL-13. Although eosinophils and AAMs were attenuated, neutrophil influx remained normal without these epithelial cytokines. Genetic ablation of ILC2s, however, enhanced IL-1β, TNFα, and IL-23 expression, increased activation of IL-17A-producing γδ T cells, and prolonged neutrophil influx. Thus, chitin elicited patterns of innate cytokines that targeted distinct populations of resident lymphoid cells, revealing divergent but interacting pathways underlying the tissue accumulation of specific types of inflammatory myeloid cells., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background:  Cryptococcal meningitis (CM) is a leading cause of death in individuals infected with human immunodeficiency virus (HIV). Identifying factors associated with mortality informs strategies to improve outcomes., Methods:  Five hundred one patients with HIV-associated CM were followed prospectively for 10 weeks during trials in Thailand, Uganda, Malawi, and South Africa. South African patients (n = 266) were followed for 1 year. Similar inclusion/exclusion criteria were applied at all sites. Logistic regression identified baseline variables independently associated with mortality., Results:  Mortality was 17% at 2 weeks and 34% at 10 weeks. Altered mental status (odds ratio [OR], 3.1; 95% confidence interval [CI], 1.7-5.9), high cerebrospinal fluid (CSF) fungal burden (OR, 1.4 per log10 colony-forming units/mL increase; 95% CI, 1.0-1.8), older age (>50 years; OR, 3.9; 95% CI, 1.4-11.1), high peripheral white blood cell count (>10 × 10(9) cells/L; OR, 8.7; 95% CI, 2.5-30.2), fluconazole-based induction treatment, and slow clearance of CSF infection were independently associated with 2-week mortality. Low body weight, anemia (hemoglobin <7.5 g/dL), and low CSF opening pressure were independently associated with mortality at 10 weeks in addition to altered mental status, high fungal burden, high peripheral white cell count, and older age. In those followed for 1 year, overall mortality was 41%. Immune reconstitution inflammatory syndrome occurred in 13% of patients and was associated with 2-week CSF fungal burden (P = .007), but not with time to initiation of antiretroviral therapy (ART)., Conclusions:  CSF fungal burden, altered mental status, and rate of clearance of infection predict acute mortality in HIV-associated CM. The results suggest that earlier diagnosis, more rapidly fungicidal amphotericin-based regimens, and prompt immune reconstitution with ART are priorities for improving outcomes.

Arg1 is produced by AAMs and is proposed to have a regulatory role during asthma and allergic inflammation. Here, we use an Arg1 reporter mouse to identify additional cellular sources of the enzyme in the lung. We demonstrate that ILC2s express Arg1 at rest and during infection with the migratory helminth Nippostrongylus brasiliensis. In contrast to AAMs, which express Arg1 following IL-4/IL-13-mediated STAT6 activation, ILC2s constitutively express the enzyme in a STAT6-independent manner. Although ILC2s deficient in the IL-33R subunit T1/ST2 maintain Arg1 expression, IL-33 can regulate total lung Arg1 by expanding the ILC2 population and by activating macrophages indirectly via STAT6. Finally, we find that ILC2 Arg1 does not mediate ILC2 accumulation, ILC2 production of IL-5 and IL-13, or collagen production during N. brasiliensis infection. Thus, ILC2s are a novel source of Arg1 in resting tissue and during allergic inflammation.

Eosinophils are specialized myeloid cells associated with allergy and helminth infections. Blood eosinophils demonstrate circadian cycling, as described over 80 years ago, and are abundant in the healthy gastrointestinal tract. Although a cytokine, interleukin (IL)-5, and chemokines such as eotaxins mediate eosinophil development and survival, and tissue recruitment, respectively, the processes underlying the basal regulation of these signals remain unknown. Here we show that serum IL-5 levels are maintained by long-lived type 2 innate lymphoid cells (ILC2) resident in peripheral tissues. ILC2 cells secrete IL-5 constitutively and are induced to co-express IL-13 during type 2 inflammation, resulting in localized eotaxin production and eosinophil accumulation. In the small intestine where eosinophils and eotaxin are constitutive, ILC2 cells co-express IL-5 and IL-13; this co-expression is enhanced after caloric intake. The circadian synchronizer vasoactive intestinal peptide also stimulates ILC2 cells through the VPAC2 receptor to release IL-5, linking eosinophil levels with metabolic cycling. Tissue ILC2 cells regulate basal eosinophilopoiesis and tissue eosinophil accumulation through constitutive and stimulated cytokine expression, and this dissociated regulation can be tuned by nutrient intake and central circadian rhythms.

Eosinophils in visceral adipose tissue (VAT) have been implicated in metabolic homeostasis and the maintenance of alternatively activated macrophages (AAMs). The absence of eosinophils can lead to adiposity and systemic insulin resistance in experimental animals, but what maintains eosinophils in adipose tissue is unknown. We show that interleukin-5 (IL-5) deficiency profoundly impairs VAT eosinophil accumulation and results in increased adiposity and insulin resistance when animals are placed on a high-fat diet. Innate lymphoid type 2 cells (ILC2s) are resident in VAT and are the major source of IL-5 and IL-13, which promote the accumulation of eosinophils and AAM. Deletion of ILC2s causes significant reductions in VAT eosinophils and AAMs, and also impairs the expansion of VAT eosinophils after infection with Nippostrongylus brasiliensis, an intestinal parasite associated with increased adipose ILC2 cytokine production and enhanced insulin sensitivity. Further, IL-33, a cytokine previously shown to promote cytokine production by ILC2s, leads to rapid ILC2-dependent increases in VAT eosinophils and AAMs. Thus, ILC2s are resident in VAT and promote eosinophils and AAM implicated in metabolic homeostasis, and this axis is enhanced during Th2-associated immune stimulation.

Background: Cryptococcal meningitis in Africa is associated with up to 70% mortality at 3 months and 500 000 deaths annually. We examined strategies to improve on fluconazole (FLU) monotherapy: addition of flucytosine (5-FC) and/or addition of short-course amphotericin B (AmB)., Methods: In step 1, previously reported, patients were randomized to receive FLU 1200 mg per day with or without 5-FC 100 mg/kg per day for 14 days. In step 2, 43 patients were similarly randomized, with addition of AmB 1 mg/kg per day for 7 days to both arms. After 2 weeks, patients received FLU monotherapy and were followed to 10 weeks. The primary endpoint was rate of clearance of infection (early fungicidal activity, EFA). Secondary endpoints related to safety and mortality., Results: Forty patients (25% with Glasgow Coma Scale <15) were analyzed. EFA for the triple combination arm was greater than that for AmB-FLU: -0.50 ± 0.15 log CFU/day vs. -0.38 ± 0.19 log colony forming units per day (P=0.03); and greater than that for step 1 with FLU-5-FC (-0.28 ± 0.17) or FLU alone (-0.11 ± 0.09). Combined analysis across steps revealed that addition of 5-FC and AmB had significant, independent additive effects on EFA, with trends toward fewer early deaths with addition of 5-FC (4/41 vs. 11/39, P = 0.05) and fewer deaths overall with addition of AmB (13/39 vs. 20/40, P = 0.1)., Conclusion: Addition of 5-FC and short-course AmB to high-dose FLU significantly enhanced EFA and may be associated with favorable trends in survival. Both these strategies should be tested in a larger phase III study.

Despite advances in medicine, infectious diseases remain major causes of death and disability worldwide. Acute or chronic infectious agents mediate host tissue damage and cause a spectrum of disease as diverse as overwhelming sepsis and shock within hours to persistent tissue inflammation causing organ failure or even cancer over years. Although pathogen exposure can cause disease via host-derived inflammation, pathogens share recognized elements with harmless human commensals. Mouse models and organisms with simpler flora are revealing the dialogue between multicellular hosts and commensal flora. In some instances the persistent inflammation associated with pathogens can be interpreted within a framework of frustrated commensalism in which the host and pathogen cannot complete the requisite dialogue that establishes homeostasis. In contrast, coevolved commensals interact cooperatively with the host immune system, resulting in immunotolerance. Attempts to more thoroughly understand the molecular nature of the dialogue may uncover novel approaches to the control of inflammation and tissue damage.

Background: Cryptococcal meningitis is a major cause of human immunodeficiency virus (HIV)-associated morbidity and mortality in Africa. Improved oral treatment regimens are needed because amphotericin B is neither available nor feasible in many centers. Fluconazole at a dosage of 1200 mg per day is more fungicidal than at a dosage of 800 mg per day, but mortality rates remain unacceptably high. Therefore, we examined the effect of adding oral flucytosine to fluconazole., Methods: From 13 February through 2 December 2008, HIV-seropositive, antiretroviral-naive patients experiencing their first episode of cryptococcal meningitis were randomized to receive (1) 14 days of fluconazole (1200 mg per day) alone or (2) in combination with flucytosine (100 mg/kg per day) followed by fluconazole (800 mg per day), with both groups undergoing 10 weeks of follow-up. The primary end point was early fungicidal activity, derived from quantitative cerebrospinal fluid cultures on days 1, 3, 7, and 14. Secondary end points were safety and 2- and 10-week mortality., Results: Forty-one patients were analyzed. Baseline mental status, cryptococcal burden, opening pressure, CD4(+) cell count, and HIV load were similar between groups. Combination therapy was more fungicidal than fluconazole alone (mean early fungicidal activity +/- standard deviation -0.28 +/- 0.17 log colony-forming units [CFU]/mL per day vs -0.11 +/- 0.09 log CFU/mL per day; P < .001). The combination arm had fewer deaths by 2 weeks (10% vs 37%) and 10 weeks (43% vs 58%). More patients had grade III or IV neutropenia with combination therapy (5 vs 1, within the first 2 weeks; P = .20), but there was no increase in infection-related adverse events., Conclusions: The results suggest that optimal oral treatment for cryptococcal meningitis is high-dose fluconazole with flucytosine. Efforts are needed to increase availability of flucytosine in Africa. Clinical trials registration. isrctn.org Identifier: ISRCTN02725351.

Insertional mutagenesis was applied to Cryptococcus neoformans to identify genes associated with virulence attributes. Using biolistic transformation, we generated 4,300 nourseothricin (NAT)-resistant strains, of which 590 exhibited stable resistance. We focused on mutants with defects in established virulence factors and identified two with reduced growth at 37 degrees C, four with reduced production of the antioxidant pigment melanin, and two with an increased sensitivity to nitric oxide (NO). The NAT insertion and mutant phenotypes were genetically linked in five of eight mutants, and the DNA flanking the insertions was characterized. For the strains with altered growth at 37 degrees C and altered melanin production, mutations were in previously uncharacterized genes, while the two NO-sensitive strains bore insertions in the flavohemoglobin gene FHB1, whose product counters NO stress. Because of the frequent instability of nourseothricin resistance associated with biolistic transformation, Agrobacterium-mediated transformation was tested. This transkingdom DNA delivery approach produced 100% stable nourseothricin-resistant transformants, and three melanin-defective strains were identified from 576 transformants, of which 2 were linked to NAT in segregation analysis. One of these mutants contained a T-DNA insertion in the promoter of the LAC1 (laccase) gene, which encodes a key enzyme required for melanin production, while the second contained an insertion in the promoter of the CLC1 gene, encoding a voltage-gated chloride channel. Clc1 and its homologs are required for ion homeostasis, and in their absence Cu+ transport into the secretory pathway is compromised, depriving laccase and other Cu(+)-dependent proteins of their essential cofactor. The NAT resistance cassette was optimized for cryptococcal codon usage and GC content and was then used to disrupt a mitogen-activated protein kinase gene, a predicted gene, and two putative chloride channel genes to analyze their contributions to fungal physiology. Our findings demonstrate that both insertional mutagenesis methods can be applied to gene identification, but Agrobacterium-mediated transformation is more efficient and generates exclusively stable insertion mutations.

Enzymes that protect cells from reactive oxygen species (superoxide dismutase, catalase, peroxidase) have well-established roles in mammalian biology and microbial pathogenesis. Two recently identified enzymes detoxify nitric oxide (NO)-related molecules; flavohemoglobin denitrosylase consumes NO, and S-nitrosoglutathione (GSNO) reductase metabolizes GSNO. Although both enzymes protect microorganisms from nitrosative challenge in vitro, their relevance has not been established in physiological contexts. Here we studied their biological functions in Cryptococcus neoformans, an established human fungal pathogen that replicates in macrophages and whose growth in vitro and in infected animals is controlled by NO bioactivity. We show that both flavohemoglobin denitrosylase and GSNO reductase contribute to C. neoformans pathogenesis. FHB1 and GNO1 mutations abolished NO- and GSNO-consuming activity, respectively. Growth of fhb1 mutant cells was inhibited by nitrosative challenge, whereas that of gno1 mutants was not. fhb1 mutants showed attenuated virulence in a murine model, and virulence was restored in iNOS(-/-) animals. Survival of the fhb1 mutant was also reduced in activated macrophages and restored to wild-type by inhibition of NOS activity. Combining mutations in flavohemoglobin and GSNO reductase, or flavohemoglobin and superoxide dismutase, further attenuated virulence. These studies illustrate that fungal pathogens elaborate enzymatic defenses against nitrosative stress mounted by the host.

The establishment and mapping of gene-specific DNA sequences greatly complement the ongoing efforts to map and sequence all human chromosomes. To facilitate our studies of human chromosome 7, we have generated and analyzed 2006 expressed-sequence tags (ESTs) derived from a collection of direct selection cDNA libraries that are highly enriched for human chromosome 7 gene sequences. Similarity searches indicate that approximately two-thirds of the ESTs are not represented by sequences in the public databases, including those in dbEST. In addition, a large fraction (68%) of the ESTs do not have redundant or overlapping sequences within our collection. Human DNA-specific sequence-tagged sites (STSs) have been developed from 190 of the ESTs. Remarkably, 180 (96%) of these STSs map to chromosome 7, demonstrating the robustness of chromosome enrichment in constructing the direct selection cDNA libraries. Thus far, 140 of these EST-specific STSs have been assigned unequivocally to YAC contigs that are distributed across the chromosome. Together, these studies provide > 2000 ESTs highly enriched for chromosome 7 gene sequences, 180 new chromosome 7 STSs corresponding to ESTs, and a definitive demonstration of the ability to enrich for chromosome-specific cDNAs by direct selection. Furthermore, the libraries, sequence data, and mapping information will contribute to the construction of a chromosome 7 transcript map.