Effects of granulocyte and granulocyte-macrophage colony-stimulating factors in a neutropenic murine model of trichosporonosis

The Host Immune Response to Scedosporium/Lomentospora

Infections caused by the opportunistic pathogens Scedosporium/Lomentospora are on the rise. This causes problems in the clinic due to the difficulty in diagnosing and treating them. This review collates information published on immune response against these fungi, since an understanding of the mechanisms involved is of great interest in developing more effective strategies against them. Scedosporium/Lomentospora cell wall components, including peptidorhamnomannans (PRMs), α-glucans and glucosylceramides, are important immune response activators following their recognition by TLR2, TLR4 and Dectin-1 and through receptors that are yet unknown. After recognition, cytokine synthesis and antifungal activity of different phagocytes and epithelial cells is species-specific, highlighting the poor response by microglial cells against L. prolificans. Moreover, a great number of Scedosporium/Lomentospora antigens have been identified, most notably catalase, PRM and Hsp70 for their potential medical applicability. Against host immune response, these fungi contain evasion mechanisms, inducing host non-protective response, masking fungal molecular patterns, destructing host defense proteins and decreasing oxidative killing. In conclusion, although many advances have been made, many aspects remain to be elucidated and more research is necessary to shed light on the immune response to Scedosporium/Lomentospora.

The Cell Biology of the Trichosporon-Host Interaction

Fungi of the genus Trichosporon are increasingly recognized as causative agents of superficial and invasive fungal disease in humans. Although most species are considered commensals of the human skin and gastrointestinal tract, these basidiomycetes are an increasing cause of fungal disease among immunocompromised hosts, such as hematological patients and solid organ transplant recipients. The initiation of commensal or pathogenic programs by Trichosporon spp. involves the adaptation to the host microenvironment and its immune system. However, the exact virulence factors activated upon the transition to a pathogenic lifestyle, including the intricate biology of the cell wall, and how these interact with and subvert the host immune responses remain largely unknown. Here, we revisit our current understanding of the virulence attributes of Trichosporon spp., particularly T. asahii, and their interaction with the host immune system, and accommodate this knowledge within novel perspectives on fungal diagnostics and therapeutics.

Immunomodulatory therapy in yeast infections

Invasive yeast infections are a significant cause of morbidity and mortality in patients with defective immune response, such as those with cancer-related immunosuppression, organ transplantation or other immunodeficiencies, and neonates. Hospitalization in the intensive care unit may increase the risk for such infections. Despite the advent of new antifungal agents, the problem is escalating as the number of susceptible hosts increase and virulent, more resistant fungal strains emerge. Over the past few years, advances in immunology and molecular biology have greatly contributed to a better understanding of the pathogenesis of yeast infections. There is evidence that reconstitution of the host immune function is a major contributor to the resolution of yeast infections. Strategies aiming to increase the phagocyte number (e.g., granulocyte transfusions), to stimulate immune response (e.g., administration of hematopoietic growth factors and other proinflammatory cytokines) and to stimulate antigen-specific immunity (e.g., antibody therapy or vaccination) benefit patients at risk of, or suffering from, yeast infections. Further preclinical and clinical studies, as well as improving our understanding of immune system functions and dysfunctions, remain a future challenge.

In vivo evidence of free radical generation in the mouse lung after exposure to Pseudomonas aeruginosa bacterium: an ESR spin-trapping investigation

In the Pseudomonas aeruginosa-induced rodent pneumonia model, it is thought that free radicals are significantly associated with the disease pathogenesis. However, until now there has been no direct evidence of free radical generation in vivo. Here we used electron spin resonance (ESR) and in vivo spin trapping with α-(4-pyridyl-1-oxide)-N-tert-butylnitrone to investigate free radical production in a murine model. We detected and identified generation of lipid-derived free radicals in vivo (a(N) =14.86 ± 0.03 G and a(H)(β) =2.48 ± 0.09 G). To further investigate the mechanism of lipid radical production, we used modulating agents and knockout mice. We found that with GdCl(3) (phagocytic toxicant), NADPH-oxidase knockout mice (Nox2(-)/(-)), allopurinol (xanthine-oxidase inhibitor) and Desferal (metal chelator), generation of lipid radicals was decreased; histopathological and biological markers of acute lung injury were noticeably improved. Our study demonstrates that lipid-derived free radical formation is mediated by NADPH-oxidase and xanthine-oxidase activation and that metal-catalysed hydroxyl radical-like species play important roles in lung injury caused by Pseudomonas aeruginosa.

Experimental pathogenicity of a clinical isolate of Trichosporon dermatis in a murine model

The pathogenicity of Trichosporon dermatis isolated from skin lesions of a patient has been examined in mice. Balb/c mice were treated with two intraperitoneal injections of 100 mg/kg cyclophosphamide on days 4 and 1 and one subcutaneous injection of 10 mg/kg dexamethasone on day 1 pre-inoculation, and then challenged with 0.2 ml T. dermatis inoculum (1 × 10(8) CFU/ml) by topical application on an abrasive wound in the dermabrasive group and by hypodermic injection in the subcutaneous group. In the intravenous group, 0.2 ml of high (1 × 10(8) CFU/ml) or low (1 × 10(7 )CFU/ml) inoculum was injected into the tail vein. Histopathology and inverse fungal culture were performed on the skin lesion and viscera, and renal fungal burden was also determined. Inoculated sites developed localized infections after dermabrasive and subcutaneous challenge in all mice, but the maximum area of skin lesions, and number of positive cultures from the lesions, were higher for immunocompromised mice. In the intravenous group, all immunocompetent animals survived during the four-week period, whereas 100 and 70% of immunocompromised animals died by 3 and 5 days in the high and low-inoculum groups, respectively. The incidence of disseminated infection and the renal fungal burden of immunocompromised mice were higher than those of immunocompetent mice. Our results demonstrate that subcutaneous and intravenous injection of T. dermatis can successfully establish cutaneous and systemic infection models in immunocompromised mice, with the kidney and lung being most susceptible.

Host immune response against Scedosporium species

Scedosporium apiospermum and Scedosporium prolificans cause therapy-refractory infections in immunocompromised and immunocompetent hosts. While innate immune response is believed to be critical for the host defense against these fungi, its role has only recently been elucidated. Undefined pathogen-associated molecular patterns on the surface of conidia and hyphae are recognized by pattern-recognition receptors (PRRs) on the membrane of phagocytes, and the signal is transmitted intracellularly. PRRs that are important in the recognition of both fungal species are human Toll-like receptors (or Toll receptors in Drosophila melanogaster) and dectin-1. These induce signals responsible for the activation of genes leading to an effective host defense, especially those encoding pro-inflammatory cytokines. Both species are efficiently phagocytosed and elicit an oxidative burst by neutrophils and monocytes. While cytokines, such as interleukin-15, granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor and interferon-gamma, have been found in vitro to variably modulate antifungal activity of human phagocytes, cytokines in vivo activities are less well documented. Certain antifungal agents exert immunopharmacological effects on phagocytes against S. apiospermum and S. prolificans. Translation of these in vitro findings to appropriate in vivo systems and into clinical trials may lead to improved strategies for augmenting innate host defenses in patients infected with these emerging pathogens.

Infección nosocomial por Trichosporon asahii: revisión clínica de 22 casos

Twenty two cases of nosocomial infection caused by Trichosporon asahii, detected during a period of six years (1999-2005) is described. The patients were predominantly males with an average age of 47.3 years-old. The predominant diseases in the study group were respiratory insufficiency, cancer, diabetes, chronic renal insufficiency, cirrhosis and AIDS. The main predisposing conditions were antibiotic therapy, mechanical ventilation, urethral catheterization, catheter, corticoids, transplant, immunosuppressive therapy, chemotherapy, granulocytopenia, surgical procedures and continuous ambulatory peritoneal dialysis. The most used antifungal drugs were fluconazole and amphotericin B. In some cases several antifungals were administered. Five patients did not receive antifungal treatment, and one patient received granulocyte colony stimulating factor (G-CSF). Nine patients showed clinical improvement, nine died and the progress of four patients is unknown. T. asahii is an emergent pathogen in patients with immunodeficiency and its presence in these type hosts can not be considered colonization, as there is an important risk of invasive infection. So, in susceptible patients to develop trichosporonosis it is advisable to take into consideration this disease especially in intensive clinical care units.

Cytokines and fungal infections

The very poor outcome of invasive fungal infections (IFI) in patients with haematological malignancies or recipients of haematopoietic stem cell transplantation is largely attributed to their compromised host defence mechanisms. The restoration or augmentation of immune responses in these patients is now considered as one of the cornerstones of effective antifungal therapy. Major advances in the field of experimental immunology have provided insight on the important regulatory role of cytokines in both innate and adaptive immunity to fungal pathogens. Preclinical studies have convincingly demonstrated that immunomodulation with cytokines can enhance the antifungal activity of neutrophils and monocytes/macrophages as well as upregulate protective T-helper type 1 adaptive immune responses. Evidence on the clinical use of cytokines in immunocompromised hosts with IFI is, however, still scant and inconclusive. The present review summarizes experimental and clinical data on the role of cytokines in the immune response to fungal pathogens and on their potential use for prevention or treatment of fungal infections. Implications for future research are also briefly discussed.

Trichosporon pullulans infection in 2 patients with chronic granulomatous disease: an emerging pathogen and review of the literature

BACKGROUND

Chronic granulomatous disease is a genetically determined primary immunodeficiency disease in which phagocytic cells are unable to kill certain bacteria and fungi after ingestion. Manifestations include recurrent pyogenic infections caused by catalase-positive microbes. Trichosporon species are emerging as opportunistic agents that cause systemic disease in immunocompromised patients. Typically disease has been described in association with T beigelii in patients with secondary immunodeficiency, such as underlying malignancy.

OBJECTIVE

The objective was to report the first 2 cases of T pullulans infection in 2 male children with chronic granulomatous disease.

METHODS

The records of the 2 patients were reviewed. In addition, all cases of T pullulans infection reported in the English language literature are presented.

RESULTS

This report brings to 7 the total number of cases of T pullulans reported and the first in patients with chronic granulomatous disease, one with invasive pneumonia and the other with an infected paronychium and localized cellulitis. In the 5 additional cases malignancy was the principal risk factor.

CONCLUSION

T pullulans has rarely been reported as a fungal pathogen. The most prominent risk factor for the development of trichosporonosis is immunocompromise, most notably with neutropenia. Abnormally functioning neutrophils, such as with chronic granulomatous disease, may also predispose individuals to this opportunistic pathogen.

Immunomodulation of invasive fungal infections

Genetic and acquired (disease- or therapy- related) host immune factors increase the risk for IFIs. In addition to antifungal drug therapy, modulation of host defenses by the use of HGFs and IFN-gamma has been supported by extensive in vitro and in vivo preclinical data. Clinical studies on the prevention or the adjunctive therapy of IFIs in combination with antifungal agents are limited, however, and do not allow specific recommendations for their cost-effective use in most of the immunodeficient settings. There is an urgent need to push forward with well-structured, randomized clinical trials to determine optimal dose, duration, and timing for different combinations of immunotherapy and antifungal agents in high-risk patients.

In vivo lipid-derived free radical formation by NADPH oxidase in acute lung injury induced by lipopolysaccharide: a model for ARDS

Intratracheal instillation of lipopolysaccharide (LPS) activates alveolar macrophages and infiltration of neutrophils, causing lung injury/acute respiratory distress syndrome. Free radicals are a special focus as the final causative molecules in the pathogenesis of lung injury caused by LPS. Although in vitro investigation has demonstrated radical generation after exposure of cells to LPS, in vivo evidence is lacking. Using electron spin resonance (ESR) and the spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN), we investigated in vivo free radical production by rats treated with intratracheal instillation of LPS. ESR spectroscopy of lipid extract from lungs exposed to LPS for 6 h gave a spectrum consistent with that of a POBN/carbon-centered radical adduct (aN=14.94+/-0.07 G and abetaH=2.42+/-0.06 G) tentatively assigned as a product of lipid peroxidation. To further investigate the mechanism of LPS-initiated free radical generation, rats were pretreated with the phagocytic toxicant GdCl3, which significantly decreased the production of radical adducts with a corresponding decrease in neutrophil infiltration. NADPH oxidase knockout mice completely blocked phagocyte-mediated, ESR-detectable radical production in this model of acute lung injury. Rats treated intratracheally with LPS generate lipid-derived free radicals via activation of NADPH oxidase.

Cytokines in immunodeficient patients with invasive fungal infections: an emerging therapy

Immune response is the major contributor to host defense against opportunistic fungal infections such as candidiasis, aspergillosis and other rare infections. A number of cytokines have been developed and studied in vitro for activity against fungal pathogens. The most studied among them in relation to fungal infections are granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF) and interferon-gamma (IFN-gamma). The fields where these cytokines have been predominantly studied or where they may need more study are primary immunodeficiencies of the phagocytic cells, neonatal age, human immunodeficiency virus infection and cancer-related conditions such as neutropenia and hemopoietic cell transplantation. In this review, the in vitro, experimental animal and clinical data of cytokines are summarized in relation to invasive candidiasis, aspergillosis and emerging fungal infections. Cytokine administration to patients together with antifungal agents, as well as transfusion of cytokine-upgraded phagocytes, are promising immunotherapeutic modalities for further research.

Granulocyte colony-stimulating factor and other cytokines in antifungal therapy

Invasive fungal infections (IFIs) have emerged as a serious threat in immunocompromised patients during the last two decades. Host defenses including appropriate cytokine responses and intact phagocytic function are necessary to combat IFIs. Several cytokines have been investigated and developed for preventive and therapeutic use. Among them, granulocyte colony-stimulating factor (G-CSF) has been mostly studied and used for various purposes, the most important being the faster recovery from neutropenia. Other cytokines with potential clinical significance in relation to IFI are granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-gamma (IFN-gamma) and macrophage colony-stimulating factor. Supported by a large number of preclinical studies but limited clinical results their potential utility against IFI has been suggested. In this review, certain questions related to this issue are discussed based on data already available and an attempt to consider future research is made.

Immunotherapy in patients with systemic mycoses: a promising adjunct

Evidence from several in vitro and animal model studies suggests a modulatory role of haemopoietic, T(H)1 and T(H)2 cytokines in host defence against fungi, and highlights their potential utility as adjunctive therapy for management of systemic mycoses (SM). However, there are limited clinical data to support the use of cytokines in prevention and treatment of SM. Thus, at present no adjunctive treatment is justified for routine use in all patients. Potential application of these immunomodulatory agents include the use of granulocyte-macrophage colony-stimulating factor or macrophage colony-stimulating factor in the management of mycoses in neutropenic patients with myelogenous leukaemia or bone marrow transplantation. Interferon-gamma may have a useful role against aspergillosis in patients with chronic granulomatous disease. Granulocyte colony-stimulating factor-elicited white blood cell transfusions may be life saving to patients with refractory SM. Better understanding of synergy between cytokines and specific antifungals may provide powerful tools for managing these serious infections.

Malignancy: Granulocyte Colony Stimulating Factor Increases the Efficacy of Conventional Amphotericin in the Treatment of Presumed Deep-Seated Fungal Infection in Neutropenic Patients following Intensive Chemotherapy or Bone Marrow Transplantation for Haematological Malignancies

A prospective, comparative study of empiric amphotericin B with, or without, granulocyte colony stimulating factor was carried out to assess whether the addition of granulocyte colony stimulating factor to empiric amphotericin B improves the clinical response in neutropenic patients with suspected or proven fungal infection. Fifty nine neutropenic adults with haematological malignancy and antibiotic-refractory fever or clinical evidence of deep-seated fungal infection were studied. Patients received intravenous colloidal amphotericin B (1 milligram per kilogram body weight) with or without subcutaneous granulocyte colony stimulating factor (three to five micrograms per kilogram body weight). Thirty patients received amphotericin alone and 29 amphotericin plus granulocyte colony stimulating factor. Nearly twice as many patients responded to amphotericin B with concomitant administration of granulocyte colony stimulating factor (62%) as responded to amphotericin alone (33%; difference in proportions 0.29, 95%CI 0.03-0.54). Clinical response in patients receiving granulocyte colony stimulating factor coincided with neutrophil recovery in most cases. Addition of granulocyte colony stimulating factor to empiric amphotericin B significantly reduced the number of patients requiring salvage therapy with lipid-associated or liposomal formulations of amphotericin B addition of granulocyte colony stimulating factor to empiric intravenous amphotericin B improves the response rate and thereby reduces the number of patients requiring salvage therapy with liposomal or lipid-associated preparations of amphotericin B.

Effects of recombinant granulocyte-colony stimulating factor administration during Mycobacterium avium infection in mice

Granulocyte colony-stimulating factor (G-CSF) administration in vivo has been shown to improve the defence mechanisms against infection by different microbes. Here we evaluated a possible protective role of this molecule in a mouse model of mycobacterial infection. The administration of recombinant G-CSF promoted an extensive blood neutrophilia but failed to improve the course of Mycobacterium avium infection in C57Bl/6 or beige mice. G-CSF administration also failed to improve the efficacy of a triple chemotherapeutic regimen (clarithromycin + ethambutol + rifabutin). G-CSF treatment did not protect interleukin-10 gene disrupted mice infected with M. avium. Spleen cells from infected mice treated with G-CSF had a decreased priming for antigen-specific production of interferon gamma compared to control infected mice. Our data do not substantiate previous reports on the protective activity of G-CSF in antimycobacterial immunity using mouse models.

Recombinant murine granulocyte-macrophage colony-stimulating factor modulates the course of pulmonary histoplasmosis in immunocompetent and immunodeficient mice

Several endogenous cytokines, including granulocyte-macrophage colony-stimulating factor (GM-CSF), are necessary for eliminating Histoplasma capsulatum from tissues. In this study, we explored the efficacy of recombinant murine GM-CSF in the treatment of pulmonary histoplasmosis. This cytokine significantly reduced fungal burden in a dose-dependent manner. Pretreatment did not consistently produce a better result than treatment started after infection. The biological effectiveness of GM-CSF was not associated with modulation of lung cytokine production or alteration in lung inflammation, but it directly activated a nonadherent lung cell population to exert anti-Histoplasma activity. GM-CSF improved survival of T-cell-depleted mice exposed to H. capsulatum. When combined with a suboptimal amount of amphotericin B, GM-CSF enhanced survival of normal or T-cell-depleted mice given a lethal challenge. These results suggest that this cytokine may be useful as an adjunctive treatment for histoplasmosis.

Experimental model of progressive disseminated trichosporonosis in mice with latent trichosporonemia

Trichosporon asahii and Trichosporon mucoides are the most common strains of fungi that cause disseminated trichosporonosis, a severe opportunistic infection in immunocompromised hosts. We have previously established a nested PCR assay using serum samples for detection of both strains. Here we describe a new experimental animal model for investigating the underlying mechanisms of disseminated trichosporonosis. T. asahii (OMU239, a clinical isolate from a patient with acute myelogenous leukemia) and 8-week-old ICR male mice were used in all experiments. A suspension of T. asahii (3 x 10(6) CFU/animal) was injected into the caudal vein of each mouse after immunosuppression with cyclophosphamide (200 mg/kg of body weight/day for 2 days) and prednisolone (30 mg/kg/day for 1 day). Mice were then divided into four subgroups (R0, R1, R2, and R3) based on the time of reimmunosuppression. The latter was performed using the same drugs 1 week (group R1), 2 weeks (group R2), and 3 weeks (group R3) after fungal infection. Reimmunosuppression was not performed in group R0. The 5-week-survival rates of mice after T. asahii infection were 0% for group R1, 50% for group R2, 80% for group R3, and 80% for group R0. There was a significant difference in the survival rates between group R1 and either group R0 or R3 (P < 0.05). Fungal clearance in peripheral blood and various organs of group R1 and R2 was delayed relative to that of group R0 but was similar to the control in group R3 in spite of reimmunosuppression. Our results suggest that the critical period for the development of disseminated trichosporonosis in our model is shorter than 3 weeks after T. asahii infection. We concluded that mice during this critical period were in a state of latent trichosporonemia. Comparison of the survival rates suggests that the nested PCR assay was more useful than blood culture and glucuronoxylomannan antigen assay in the detection of this latent trichosporonemia.

Trichosporon beigelii: a life-threatening pathogen in immunocompromised hosts

Patients undergoing bone marrow transplantation are profoundly immunosuppressed as a result of their intensive myeloablative chemotherapy and are at high risk for opportunistic fungal infections mainly caused by Candida spp and Aspergillus spp. Trichosporon beigelii (T beigelii) has emerged as a life-threatening opportunistic pathogen in granulocytopenic and immunocompromised hosts and there is a marked increase in cases reported in the literature. Response to antifungal agents is poor, mortality is high and immunological recovery is the most important factor for a favorable outcome in patients with trichosporonosis. We present three cases of T. beigelii infection in patients undergoing allogeneic bone marrow transplantation in our center and we review cases described in the literature.

Effects of macrophage colony-stimulating factor (M-CSF) on anti-fungal activity of mononuclear phagocytes against Trichosporon asahii

Trichosporon asahii is an emerging opportunistic pathogen in immunocompromised patients. Little is known about the mechanisms of host defence against T. asahii. We investigated the fungicidal activity of human peripheral blood monocytes and murine peritoneal macrophages against T. asahii isolates, and the effects of M-CSF on the anti-fungal activity of mononuclear phagocytes. We also established a neutropenic mouse model of disseminated trichosporonosis with T. asahii. M-CSF enhanced the phagocytic fungicidal activity of mononuclear cells, and infected mice treated with human M-CSF at 10 x 106 U/kg showed a significant improvement in survival rate, with fewer fungal colony counts in the lung compared with control mice. Mice treated with human M-CSF showed higher concentrations of tumour necrosis factor-alpha (TNF-alpha) in the lung and plasma compared with control mice. The survival rate was significantly reduced in mice treated with anti-mouse TNF-alpha. Our results showed that M-CSF enhanced the fungicidal activity of mononuclear phagocytes partly by production of TNF-alpha, and suggest that the administration of M-CSF to patients with disseminated trichosporonosis may be a useful adjunct to conventional anti-microbial therapy and prophylaxis.

Granulocyte-Macrophage Colony-Stimulating Factor Upregulates Reduced 5-Lipoxygenase Metabolism in Peripheral Blood Monocytes and Neutrophils in Acquired Immunodeficiency Syndrome

Leukotrienes (LT) are mediators derived from the 5-lipoxygenase (5-LO) pathway, which play a role in host defense, and are synthesized by both monocytes (peripheral blood monocyte [PBM]) and neutrophils (PMN). Because 5-LO metabolism is reduced in alveolar macrophages and PMN from acquired immunodeficiency syndrome (AIDS) subjects, we investigated the synthesis of LT by PBM and PMN from these subjects. There was a reduction (74.2% ± 8.8% of control) in LT synthesis in PBM from human immunodeficiency virus (HIV)-infected compared with normal subjects. Expression of 5-LO (51.2% ± 8.8% of control), and 5-LO activating protein (FLAP) (48.5% ± 8.0% of control) was reduced in parallel. We hypothesized that this reduction in LT synthetic capacity in PBM and PMN was due to reduced cytokine production by CD4 T cells, such as granulocyte-macrophage colony-stimulating factor (GM-CSF). We treated 10 AIDS subjects with GM-CSF for 5 days. PBM 5-LO metabolism ex vivo was selectively increased after GM-CSF therapy and was associated with increased 5-LO and FLAP expression. PMN leukotriene B4(LTB4) synthesis was also augmented and associated with increased 5-LO, FLAP, and cytosolic phospholipase A2 expression. In conclusion, as previously demonstrated for PMN, PBM from AIDS subjects also demonstrate reduced 5-LO metabolism. GM-CSF therapy reversed this defect in both PBM and PMN. In view of the role of LT in antimicrobial function, cytokine administration in AIDS may play a role as adjunct therapy for infections.

Granulocyte-Macrophage Colony-Stimulating Factor Upregulates Reduced 5-Lipoxygenase Metabolism in Peripheral Blood Monocytes and Neutrophils in Acquired Immunodeficiency Syndrome

Leukotrienes (LT) are mediators derived from the 5-lipoxygenase (5-LO) pathway, which play a role in host defense, and are synthesized by both monocytes (peripheral blood monocyte [PBM]) and neutrophils (PMN). Because 5-LO metabolism is reduced in alveolar macrophages and PMN from acquired immunodeficiency syndrome (AIDS) subjects, we investigated the synthesis of LT by PBM and PMN from these subjects. There was a reduction (74.2% ± 8.8% of control) in LT synthesis in PBM from human immunodeficiency virus (HIV)-infected compared with normal subjects. Expression of 5-LO (51.2% ± 8.8% of control), and 5-LO activating protein (FLAP) (48.5% ± 8.0% of control) was reduced in parallel. We hypothesized that this reduction in LT synthetic capacity in PBM and PMN was due to reduced cytokine production by CD4 T cells, such as granulocyte-macrophage colony-stimulating factor (GM-CSF). We treated 10 AIDS subjects with GM-CSF for 5 days. PBM 5-LO metabolism ex vivo was selectively increased after GM-CSF therapy and was associated with increased 5-LO and FLAP expression. PMN leukotriene B4(LTB4) synthesis was also augmented and associated with increased 5-LO, FLAP, and cytosolic phospholipase A2 expression. In conclusion, as previously demonstrated for PMN, PBM from AIDS subjects also demonstrate reduced 5-LO metabolism. GM-CSF therapy reversed this defect in both PBM and PMN. In view of the role of LT in antimicrobial function, cytokine administration in AIDS may play a role as adjunct therapy for infections.

Selective Expansion of Alveolar Macrophages In Vivo by Adenovirus-Mediated Transfer of the Murine Granulocyte-Macrophage Colony-Stimulating Factor cDNA

Based on the hypothesis that genetic modification of freshly isolated alveolar macrophages (AM) with the granulocyte-macrophage colony-stimulating factor (GM-CSF) cDNA would induce AM to proliferate, this study focuses on the ability of adenoviral (Ad) vectors to transfer and efficiently express the murine (m) GM-CSF cDNA in murine AM with consequent expansion in the number of AM in vitro and in vivo. To demonstrate that an Ad vector can effectively transfer and express genes in AM, murine AM recovered by bronchoalveolar lavage from the lung of Balb/c mice were infected with an Ad vector coding for green fluorescent protein (GFP) in vitro and expressed GFP in a dose-dependent fashion. Infection of AM with an Ad vector containing an expression cassette coding for mGM-CSF led to GM-CSF expression and to AM proliferation in vitro. When AM infected with AdGFP were returned to the respiratory tract of syngeneic recipient mice, GFP-expressing cells could still be recovered by bronchoalveolar lavage 2 weeks later. In vitro infection of AM with AdmGM-CSF and subsequent transplantation of the genetically modified AM to the lungs of syngeneic recipients led to GM-CSF expression in vivo. Strikingly, the AM recovered by lavage 5 weeks after transplantation demonstrated an increased rate of proliferation, and the total number of alveolar macrophages was 1.9-fold greater than controls. Importantly, the increase in the numbers of AM was selective (ie, other inflammatory cell numbers were unchanged), and there was no modification to the lung architecture. Thus, it is feasible to genetically modify AM with Ad vectors and to use this strategy to modify the behavior of AM in vivo. Based on the importance of AM in the primary defense of the respiratory epithelial surface, this strategy may be useful in enhancing pulmonary defenses in immunodeficiency states.

Selective Expansion of Alveolar Macrophages In Vivo by Adenovirus-Mediated Transfer of the Murine Granulocyte-Macrophage Colony-Stimulating Factor cDNA

Based on the hypothesis that genetic modification of freshly isolated alveolar macrophages (AM) with the granulocyte-macrophage colony-stimulating factor (GM-CSF) cDNA would induce AM to proliferate, this study focuses on the ability of adenoviral (Ad) vectors to transfer and efficiently express the murine (m) GM-CSF cDNA in murine AM with consequent expansion in the number of AM in vitro and in vivo. To demonstrate that an Ad vector can effectively transfer and express genes in AM, murine AM recovered by bronchoalveolar lavage from the lung of Balb/c mice were infected with an Ad vector coding for green fluorescent protein (GFP) in vitro and expressed GFP in a dose-dependent fashion. Infection of AM with an Ad vector containing an expression cassette coding for mGM-CSF led to GM-CSF expression and to AM proliferation in vitro. When AM infected with AdGFP were returned to the respiratory tract of syngeneic recipient mice, GFP-expressing cells could still be recovered by bronchoalveolar lavage 2 weeks later. In vitro infection of AM with AdmGM-CSF and subsequent transplantation of the genetically modified AM to the lungs of syngeneic recipients led to GM-CSF expression in vivo. Strikingly, the AM recovered by lavage 5 weeks after transplantation demonstrated an increased rate of proliferation, and the total number of alveolar macrophages was 1.9-fold greater than controls. Importantly, the increase in the numbers of AM was selective (ie, other inflammatory cell numbers were unchanged), and there was no modification to the lung architecture. Thus, it is feasible to genetically modify AM with Ad vectors and to use this strategy to modify the behavior of AM in vivo. Based on the importance of AM in the primary defense of the respiratory epithelial surface, this strategy may be useful in enhancing pulmonary defenses in immunodeficiency states.