Biomedical subjects

John R Perfect

Publications and source records attributed to John R Perfect.

83 records · Page 5Linked to original sources

PubMed2002

Cryptococcosis.

Cryptococcus neoformans has risen to a worldwide highly recognizable major opportunistic pathogen with deadly consequences. It has become a model fungus to study a variety of paradigms in the host-fungus relationships. Genomic studies are advancing knowledge on its evolution and dissecting its virulence composite. Studies designed to understand host immunology to this fungus are leading to development of active and passive prevention and therapeutic strategies. This article collates and analyzes both new and old knowledge about the pathogen to help frame the meaning of human cryptococcosis as it starts to evolve in the new millennium.

AIDS-Related Opportunistic Infections↗

PubMed2002

Recent advances in the epidemiology, prevention, diagnosis, and treatment of fungal pneumonia.

Although pneumonia caused by fungi is not a common occurrence in the general population, disease in an enlarging immunocompromised population is encountered with increasing frequency. Fungal pneumonias are most frequently caused by Aspergillus spp., dimorphic fungi and Cryptococcus neoformans. Recent studies have identified risk factors of thrombocytopenia, environmental events (such as construction or renovation) and immunosuppressive drug therapies as being specific risk factors for invasive fungal disease in select patient populations. Diagnostic strategies to detect circulating antigens and polymerase chain reaction based detection systems have been explored to improve identification prior to the progressive advanced disease. Advances in prophylactic strategies include increased use of aerosolized formulations of amphotericin B, usually in conjunction with new and old systemic antifungal agents. Despite recent published guidelines for treatment of fungal pneumonia based on etiology, mortality remains high in some infections with advanced disease. Caspofungin, a new echinocandin antifungal, has recently been approved by the US Food and Drug Administration for the treatment of invasive Aspergillus infections in patients unresponsive to or unable to receive amphotericin B. A triazole antifungal, voriconazole, has shown promise in phase III clinical trials in patients with refractory fungal infections and is expected to be available in early 2002. Other echinocandin and triazole antifungals are under development in attempts to provide improved effective therapy for fungal pneumonia.

Antifungal Agents↗

PubMed2002

Voriconazole in the treatment of aspergillosis, scedosporiosis and other invasive fungal infections in children.

OBJECTIVE: To describe the safety and efficacy of voriconazole in children treated within the compassionate release program. METHODS: Children received voriconazole on a compassionate basis for treatment of an invasive fungal infection if they were refractory to or intolerant of conventional antifungal therapy. Voriconazole was administered as a loading dose of 6 mg/kg every 12 h i.v. on Day 1 followed by 4 mg/kg every 12 h i.v. thereafter. When feasible the route of administration of voriconazole was changed from i.v. to oral (100 or 200 mg twice a day for patients weighing < 40 or > or = 40 kg, respectively). Outcome was assessed by investigators at the end of therapy or at the last visit as success (complete or partial response), stable infection, or failure, based on protocol-defined criteria. RESULTS: Sixty-nine children (ages 9 months to 15 years; median, 7 years) received voriconazole; 58 had a proven or probable fungal infection. Among these 58 patients 27 had hematologic malignancies and 13 had chronic granulomatous disease as the most frequent underlying conditions. Forty-two patients had aspergillosis, 8 had scedosporiosis, 4 had invasive candidiasis and 4 had other invasive fungal infections. The median duration of voriconazole therapy was 93 days. At the end of therapy 26 patients (45%) had a complete or partial response. Four patients (7%) had a stable response, 25 (43%) failed therapy and 4 (7%) were discontinued from voriconazole because of intolerance. Success rates were highest in patients with chronic granulomatous disease (62%) and lowest in patients with hematologic malignancies (33%). Two patients experienced treatment-related serious adverse events (ulcerated lips with rash, elevated hepatic transaminases or bilirubin). A total of 23 patients had voriconazole-related adverse events, 3 (13%) of which caused discontinuation of voriconazole therapy. The most commonly reported adverse events included elevation in hepatic transaminases or bilirubin (n = 8), skin rash (n = 8), abnormal vision (n = 3) and a photosensitivity reaction (n = 3). CONCLUSION: These data support the use of voriconazole for treatment of invasive fungal infections in pediatric patients who are intolerant of or refractory to conventional antifungal therapy.

Adolescent↗

PubMed2002

Safety and efficacy of quinupristin/dalfopristin for treatment of invasive Gram-positive infections in pediatric patients.

BACKGROUND: Antibiotic-resistant Gram-positive pathogens are an increasingly common cause of serious pediatric infections. Although quinupristin/dalfopristin demonstrates favorable activity against resistant Gram-positive pathogens (including many vancomycin-resistant and methicillin-resistant staphylococci), published experience in the pediatric patient population is limited. METHODS: We retrospectively analyzed data from the global quinupristin/dalfopristin Emergency-Use Program, which enrolled patients with serious Gram-positive infections who had no further therapy options because of resistance to, failure on or intolerance to standard antibiotic treatments. Our subset included safety and efficacy data from pediatric patients (age <18 years). There were no restrictions on underlying diseases, severity of illness or prior/concomitant antimicrobial use. RESULTS: Between May 1995 and October 1999, 127 pediatric patients with 131 infections were enrolled. Microbiologic confirmation of etiology was available in 124 patients. All patients had 1 or more concomitant conditions, including malignancy and solid organ or bone marrow transplantation. The most frequent causative pathogens were vancomycin-resistant (80%), spp. (7%), methicillin-resistant (6%) and (4%). All but 21 patients received intravenous quinupristin/dalfopristin 7.5 mg/kg every 8 h. The favorable clinical response rate of quinupristin/dalfopristin was 86 of 124 (69%); the favorable microbiologic response rate was 97 of 124 (78%). Eleven patients (8%) had nonvenous adverse events classified as possibly or probably related to quinupristin/dalfopristin. CONCLUSIONS: Quinupristin/dalfopristin demonstrated favorable response rates and was reasonably well-tolerated in pediatric patients with serious Gram-positive infections unable to receive alternative therapy. In our opinion quinupristin/dalfopristin is a therapeutic option for the management of such infections.

Adolescent↗

PubMed2002

Antisense repression in Cryptococcus neoformans as a laboratory tool and potential antifungal strategy.

Antisense repression was used as a method to alter gene function in the human-pathogenic fungus Cryptococcus neoformans. The calcineurin A gene (CNA1) and the laccase gene (LAC1) were targeted since disruption of these loci results in phenotypes that are easy to screen (temperature sensitivity and lack of melanin, respectively). Serotype D yeasts were transformed with a plasmid containing the CNA1 cDNA in an antisense orientation under the control of the inducible GAL7 promoter, and serotype A yeasts were transformed with a plasmid containing the LAC1 cDNA in an antisense orientation under the control of the constitutive actin promoter. The calcineurin transformants demonstrated a temperature-sensitive phenotype only when grown on galactose, and the laccase transformants had decreased melanin production. Northern blot analysis of the calcineurin antisense transformants confirmed that the inducible phenotype was associated with a decrease in the native CNA1 transcript levels. Furthermore, it was possible to modestly impair growth of C. neoformans at 37 degrees C by using a 30 bp antisense oligonucleotide targeting CNA1. Antisense repression is now available as a tool for molecular studies in this organism, and may be applicable to other human-pathogenic fungi that have less amenable genetic systems.

Antifungal Agents↗

PubMed2002

Adenylyl cyclase functions downstream of the Galpha protein Gpa1 and controls mating and pathogenicity of Cryptococcus neoformans.

The signaling molecule cyclic AMP (cAMP) is a ubiquitous second messenger that enables cells to detect and respond to extracellular signals. cAMP is generated by the enzyme adenylyl cyclase, which is activated or inhibited by the Galpha subunits of heterotrimeric G proteins in response to ligand-activated G-protein-coupled receptors. Here we identified the unique gene (CAC1) encoding adenylyl cyclase in the opportunistic fungal pathogen Cryptococcus neoformans. The CAC1 gene was disrupted by transformation and homologous recombination. In stark contrast to the situation for Saccharomyces cerevisiae, in which adenylyl cyclase is essential, C. neoformans cac1 mutant strains were viable and had no vegetative growth defect. Furthermore, cac1 mutants maintained the yeast-like morphology of wild-type cells, in contrast to the constitutively filamentous phenotype found upon the loss of adenylyl cyclase in another basidiomycete pathogen, Ustilago maydis. Like C. neoformans mutants lacking the Galpha protein Gpal, cac1 mutants were mating defective and failed to produce two inducible virulence factors: capsule and melanin. As a consequence, cac1 mutant strains were avirulent in animal models of cryptococcal meningitis. Reintroduction of the wild-type CAC1 gene or the addition of exogenous cAMP suppressed cac1 mutant phenotypes. Moreover, the overexpression of adenylyl cyclase restored mating and virulence factor production in gpal mutant strains. Physiological studies revealed that the Galpha protein Gpa1 and adenylyl cyclase controlled cAMP production in response to glucose, and no cAMP was detectable in extracts from cac1 or gpa1 mutant strains. These findings provide direct evidence that Gpal and adenylyl cyclase function in a conserved signal transduction pathway controlling cAMP production, hyphal differentiation, and virulence of this human fungal pathogen.

Adenylyl Cyclases↗

PubMed2002

Mating-type-specific and nonspecific PAK kinases play shared and divergent roles in Cryptococcus neoformans.

Cryptococcus neoformans is an opportunistic fungal pathogen with a defined sexual cycle involving fusion of haploid MATalpha and MATa cells. Virulence has been linked to the mating type, and MATalpha cells are more virulent than congenic MATa cells. To study the link between the mating type and virulence, we functionally analyzed three genes encoding homologs of the p21-activated protein kinase family: STE20alpha, STE20a, and PAK1. In contrast to the STE20 genes that were previously shown to be in the mating-type locus, the PAK1 gene is unlinked to the mating type. The STE20alpha, STE20a, and PAK1 genes were disrupted in serotype A and D strains of C. neoformans, revealing central but distinct roles in mating, differentiation, cytokinesis, and virulence. ste20alpha pak1 and ste20a pak1 double mutants were synthetically lethal, indicating that these related kinases share an essential function. In summary, our studies identify an association between the STE20alpha gene, the MATalpha locus, and virulence in a serotype A clinical isolate and provide evidence that PAK kinases function in a MAP kinase signaling cascade controlling the mating, differentiation, and virulence of this fungal pathogen.

Alleles↗

PubMed2002

Relationship of the glyoxylate pathway to the pathogenesis of Cryptococcus neoformans.

Functional genomics has become a major focus in the study of microbial pathogenesis. This study used a functional genomic tool, differential display reverse transcription-PCR, to identify a transcriptional profile of Cryptococcus neoformans cells as they produced meningitis in an immunosuppressed host. This serial global gene expression during infection allowed for the identification of up- and down-regulated genes during infection. During this profiling, a single gene for the enzyme isocitrate lyase (ICL1) was found to be up regulated at 1 week of infection in a rabbit meningitis model and during a time of maximum host cellular response. The finding suggested that this enzyme and the glyoxylate shunt pathway are important to this yeast's energy production during infection. However, site-directed icl1 mutants had no apparent virulence defect in two animal models and no growth defect within macrophages. These observations suggest that although the yeast responded to a certain environmental cue(s) by an increase in ICL1 expression during infection, this gene was not necessary for progression of a C. neoformans infection. Compounds that specifically target only ICL1 are unlikely to cripple C. neoformans growth in vivo.

Amino Acid Sequence↗

PubMed2002

Outcome of lung transplantation in patients with mycetomas.

BACKGROUND: Lung transplantation has become an acceptable treatment option for many end-stage lung diseases. Pulmonary mycetomas are found in patients with end-stage lung diseases, especially sarcoidosis. The clinical course and long-term outcome of these patients after transplantation remains unknown. METHODS: We reviewed retrospectively the pathology reports of the explanted lungs from all lung and heart-lung transplantations performed at our institution between January 20, 1992, and June 26, 2000. Patients were included in our study if mycetomas were present on the specimens. Information on transplant date and type, diagnosis, information on antifungal therapy and fungal infections pretransplant and posttransplant, and clinical course after transplantation was recorded. RESULTS: Mycetomas were present in 3.0% of transplant recipients (9 of 303 patients). The underlying pulmonary diagnoses were sarcoidosis (six patients), and emphysema, idiopathic pulmonary fibrosis, and pneumoconiosis (one patient each). Seven patients received bilateral lung transplants, one patient received a heart/lung transplant, and one patient received a single lung transplant. Aspergillus was isolated from culture in five patients pretransplant and from five patients posttransplant. Six patients received treatment with itraconazole, or IV or inhaled amphotericin B prior to transplantation. All patients who survived transplantation received posttransplant antifungal therapy. Four patients died in the first month after transplantation. Two patients died at 17 months and 24 months posttransplant, respectively; one patient received a second transplant 30 months later; and two patients are alive and free from fungal infections 17 months and 18 months, respectively, after transplantation. All of the medium-term survivors received lengthy therapy with inhaled and systemic amphotericin B and itraconazole before and after transplantation. CONCLUSIONS: Lung transplant recipients with mycetomas have significantly reduced posttransplant survival. Careful selection of patients and aggressive antifungal therapies before and after transplantation have led to improved outcomes in patients with mycetomas. Additional research is needed to define the best therapeutic strategy for these patients during transplantation.

Adult↗

PubMedDate not supplied

Evaluation of host immune responses to pulmonary cryptococcosis using a temperature-sensitive C. neoformans calcineurin A mutant strain.

Cryptococcus neoformans is an opportunistic fungal pathogen that threatens individuals with impaired cell-mediated immunity (CMI). Presently, there are no standardized vaccines available to prevent cryptococcal infections and conventional anti-fungal drug therapy does not induce host immune reactivity and thus cannot efficiently resolve C. neoformans infections in immunocompromised individuals. The present study was designed to characterize pulmonary immune responses following infection with an avirulent temperature-sensitive (ts) mutant, calcineurin A1 (cna1) compared to the pathogenic C. neoformans strain H99 and its potential to induce protective anti-cryptococcal immunity. Host CMI responses in cna1-inoculated mice were observed to be dose-dependent, and comprise increases in pulmonary macrophages and CD4(+) T lymphocytes. However, cytokine analysis demonstrated a mixed pulmonary cytokine response (increases in IL-4, and MCP-1) with no induction of IFN-gamma. Also, pre-immunization with the ts cna1 mutant did not result in protection from a subsequent secondary pulmonary infection with the pathogenic C. neoformans strain H99. Taken together, these results suggest that host pulmonary CMI responses to the ts cna1 mutant that is eventually eliminated from the host without the induction of IFN-gamma appear to be dose-dependent, diverse, and require further stimulation to induce C. neoformans-specific Th1-type cytokine responses to resolve subsequent experimental pulmonary cryptococcal infections.

Animals↗

PubMedDate not supplied

Evaluation and management of fungal infections in immunocompromised patients.

As the population of chronically immunosuppressed individuals continues to grow, the prevalence of fungal infections is increasing. Fungal infections in this patient population represent challenges in diagnosis and management. This article will review the common superficial and invasive mycoses that occur in the solid organ transplant and HIV-infected populations. Disease presentations are reviewed, but emphasis is placed on cutaneous manifestations. Recent advances in antifungal therapy and their direct application to specific diseases provide important new approaches to this complex and often seriously ill patient population.

Antifungal Agents↗