Joseph Bliss | Brown University (original) (raw)

Papers by Joseph Bliss

Current Fungal Infection Reports, 2015

Candida species are the leading cause of invasive fungal infections in premature infants. Associa... more Candida species are the leading cause of invasive fungal infections in premature infants. Associated with substantial morbidity and mortality, these infections represent serious and sometimes catastrophic complications in the course of hospitalization of a preterm infant in the neonatal intensive care unit. Although virulence factors of Candida and the host defense mechanisms that are important in protection from candidiasis have been the subject of intensive study, considerably less is known about the features of this disease that are specific to premature neonates. As animal models for neonatal candidiasis have been developed, efforts to understand the similarities and differences of candidiasis in the neonatal host relative to other immunocompromised patients have begun to provide insights to these questions.

Evidence-Based Handbook of Neonatology, 2011

Med Mycol, Feb 8, 2010

Candida species are associated with invasive fungal infections, and C. parapsilosis has become in... more Candida species are associated with invasive fungal infections, and C. parapsilosis has become increasingly prevalent. As key antifungal effector cells, the function of human neutrophils confronting C. parapsilosis was investigated. We hypothesized that interaction between neutrophils and Candida species may not be uniform. Opsonins were omitted from these studies to understand the antifungal mechanisms at their most basic level. Human neutrophils underwent phagocytosis of C. parapsilosis with much higher efficiency than C. albicans. Immunofluorescence assays with βglucan specific antibody detected more surface exposed β-glucan on C. parapsilosis than C. albicans. However, blockade of the β-glucan receptor, Dectin-1, reduced phagocytosis of C. albicans but not C. parapsilosis. Inclusion of excess β-glucan, mannan, or chitin also had no effect on phagocytosis of C. parapsilosis. Consistent with the difference in phagocytosis, neutrophils mediated damage to C. parapsilosis but not C. albicans in assays of residual metabolic activity. C. parapsilosis was more sensitive to oxidative stress, and inclusion of antioxidant in toxicity assays decreased neutrophil mediated damage, suggesting that generation of reactive oxygen species contributes to the mechanism of toxicity. These data suggest that the interaction between neutrophils and Candida species is not uniform and may partially account for differences observed in the epidemiology and natural history of infections caused by these species.

Textbook of Clinical Pediatrics, 2012

Journal of Infectious Diseases, 2015

Release of neutrophil extracellular traps (NETs) is a significant antimicrobial host defense mech... more Release of neutrophil extracellular traps (NETs) is a significant antimicrobial host defense mechanism in adults. In neonates, fungal sepsis is a frequent cause of morbidity and mortality and may be a consequence of inadequate neutrophil defense functions. Like neutrophils from adult donors, we found that neutrophils from neonates formed robust cellular aggregates and released NETs in response to fungal β-glucan and Candida albicans hyphae when presented with extracellular matrix. Therefore, in response to fungal stimulation, neonatal neutrophils are capable of NETosis. Neonate susceptibility to fungal infections may not be due to an inability of their neutrophils to produce NETs.

Molecular microbiology, 1996

Capsules are well-studied components of the bacterial surface that modulate interactions between ... more Capsules are well-studied components of the bacterial surface that modulate interactions between the cell and its environment. Generally composed of polysaccharide, they are key virulence determinants in invasive infections in humans and other animals. Genetic determinants involved in capsule expression have been isolated from a number of organisms, but perhaps the best characterized is the kps cluster of Escherichia coli K1. In this review, the current understanding of the functions of the kps gene products is summarized. Further, a proposed mechanistic model for capsule expression is presented and discussed. The model is based on the premise that the numerous components of the kps cluster form a hetero-oligomeric complex responsible for synthesis and concurrent translocation of the capsular polysialic acid through sites of inner and outer membrane fusion. We view the ATP-binding cassette (ABC) transporter, KpsMT, to be central to the functioning of the complex, interacting with th...

Medical Mycology, 2013

Recent in vitro studies have implicated galectin-3 as an important receptor in host recognition a... more Recent in vitro studies have implicated galectin-3 as an important receptor in host recognition and response to specific Candida species; however, its role in protection against disseminated candidiasis in vivo has not been evaluated. This study investigated the importance of galectin-3 in host defense against systemic infection with the highly virulent species Candida albicans, and the less virulent species, C. parapsilosis. Mice deficient in galectin-3 (gal3-/-) were more susceptible to infection than wild-type (WT) mice. When infected with C. albicans, gal3-/- mice died significantly faster and exhibited a trend towards increased fungal burden and increased abscess formation in infected brains compared to WT mice. When infected with C. parapsilosis, gal3-/- mice had significantly higher renal fungal burdens and abscess formation compared to WT mice. To evaluate whether galectin-3 may contribute to susceptibility to candidiasis in human infants, galectin-3 levels in sera of newborn infants, a patient population uniquely susceptible to infections with both C. albicans and C. parapsilosis, were compared to serum galectin-3 levels of adults. Galectin-3 levels were significantly lower in newborn infant sera compared to adult sera. These data indicate that galectin-3 plays an important role in a murine model of disseminated candidiasis and suggest a potential mechanism of neonatal susceptibility to these infections.

Medical Mycology, 2010

Candida species are associated with invasive fungal infections, and C. parapsilosis has become in... more Candida species are associated with invasive fungal infections, and C. parapsilosis has become increasingly prevalent. As key antifungal effector cells, the function of human neutrophils confronting C. parapsilosis was investigated. We hypothesized that interaction between neutrophils and Candida species may not be uniform. Opsonins were omitted from these studies to understand the antifungal mechanisms at their most basic level. Human neutrophils underwent phagocytosis of C. parapsilosis with much higher efficiency than C. albicans. Immunofluorescence assays with βglucan specific antibody detected more surface exposed β-glucan on C. parapsilosis than C. albicans. However, blockade of the β-glucan receptor, Dectin-1, reduced phagocytosis of C. albicans but not C. parapsilosis. Inclusion of excess β-glucan, mannan, or chitin also had no effect on phagocytosis of C. parapsilosis. Consistent with the difference in phagocytosis, neutrophils mediated damage to C. parapsilosis but not C. albicans in assays of residual metabolic activity. C. parapsilosis was more sensitive to oxidative stress, and inclusion of antioxidant in toxicity assays decreased neutrophil mediated damage, suggesting that generation of reactive oxygen species contributes to the mechanism of toxicity. These data suggest that the interaction between neutrophils and Candida species is not uniform and may partially account for differences observed in the epidemiology and natural history of infections caused by these species.

Journal of Chemical Education, 2013

ABSTRACT Efforts to provide active research context to introductory courses in basic sciences are... more ABSTRACT Efforts to provide active research context to introductory courses in basic sciences are likely to better engage learners and provide a framework for relevant concepts. A simple teaching and learning experiment was conducted to use concepts in organic chemistry to solve problems in the life sciences. Bryant University is a liberal arts university with new programs in biological and environmental sciences. This laboratory exercise was developed for introductory organic chemistry and designed to highlight its applicability to the biological sciences. Students participated in an ongoing project to identify antigens on the surface of Candida albicans hyphae by testing a variety of lipid extraction procedures and characterizing the fatty acid and carbohydrate composition of their extractions by thin-layer chromatography and gas chromatography–mass spectrometry. Student extracts were also tested in an immunoblot assay with a specific antibody fragment (scFv) that recognizes an unknown component of the cell surface of C. albicans hyphae. In order to build communication skills, students were required to prepare and present posters detailing the project and their findings.

Infection and Immunity, 2003

Specific antibody opsonization significantly enhances the level of phagocytosis of Candida in the... more Specific antibody opsonization significantly enhances the level of phagocytosis of Candida in the absence of complement. Furthermore, we have described a system using a recombinant human antibody single-chain variable fragment that allows a comparative study of phagocytosis of multiple Candida species opsonized via a common antigen.

Fungal Genetics and Biology, 2010

As a means to study surface proteins involved in the yeast to hypha transition, human monoclonal ... more As a means to study surface proteins involved in the yeast to hypha transition, human monoclonal antibody fragments (single-chain variable fragments, scFv) have been generated that bind to antigens expressed on the surface of Candida albicans yeast and/or hyphae. A cDNA expression library was constructed from hyphae, and screened for immunoreactivity with scFv5 as a means to identify its cognate antigen. A reactive clone contained the 3 0 end of the C. albicans gene, orf 19.7136, designated SPT6 based on homology to Saccharomyces cerevisiae, where its product functions as a transcription elongation factor. A mutant containing a homozygous deletion of SPT6 was isolated, demonstrating that unlike S. cerevisiae, deletion of this gene in C. albicans is not lethal. Growth of this strain was severely impaired, however, as was its capacity to undergo filamentous growth. Reactivity with scFv5 was not detected in the mutant strain, although its impaired growth complicates the interpretation of this finding. To assess C. albicans SPT6 function, expression of the C. albicans gene was induced in a defined S. cerevisiae spt6 mutant. Partial complementation was seen, confirming that the C. albicans and S. cerevisiae genes are functionally related in these species.

FEMS Immunology & Medical Microbiology, 2006

This study evaluates the conditions in which peripheral blood mononuclear cells mediate toxicity ... more This study evaluates the conditions in which peripheral blood mononuclear cells mediate toxicity to Candida albicans opsonized with heat-inactivated human serum. Serum concentrations as low as 1% resulted in 50% inhibition of C. albicans metabolic activity after incubation with peripheral blood mononuclear cells at an effector to target ratio of 8. Measurable inhibition was also achieved at lower effector to target ratios and lower serum concentrations, and at least a portion of the metabolic inhibition reflected fungal cell death. Depletion of C. albicans-specific antibody decreased the toxic effect while opsonization with purified human IgG restored toxicity, and cell-cell contact between peripheral blood mononuclear cells and fungus was required. Depletion of or enrichment for monocytes from the peripheral blood mononuclear cells preparation diminished the toxic effect and the monocytic cell line, THP-1, was likewise incapable of toxicity. These studies provide evidence that antibody augments antifungal host defense and underscore the complex interrelationship between humoral and cellular immunity in these infections.

Expert Review of Anti-infective Therapy, 2012

Invasive candidiasis is a common problem in premature infants that leads to high morbidity and mo... more Invasive candidiasis is a common problem in premature infants that leads to high morbidity and mortality. Although Candida albicans has historically been the most prominent species involved in these infections and has therefore been the subject of the most study, Candida parapsilosis is increasing in frequency, and neonates are disproportionately affected. This article reviews unique aspects of the epidemiology of this organism as well as strategies for prophylaxis against invasive candidiasis in general. Additionally, important differences between C. parapsilosis and C. albicans are coming to light related to virulence determinants and interactions with components of host immunity. These developments are reviewed while highlighting the significant gaps in our understanding that remain to be elucidated.

Cellular Microbiology, 2013

Candida albicans causes the majority of invasive candidiasis in immunocompromised adults while Ca... more Candida albicans causes the majority of invasive candidiasis in immunocompromised adults while Candida parapsilosis is a leading cause of neonatal candidiasis. While much work has focused on how the immune system recognizes and responds to C. albicans, less is known about host interaction with C. parapsilosis. This study investigates the human neutrophil phagocytic response to these species. Neutrophils underwent phagocytosis of C. parapsilosis yeast and C. albicans hyphae much more efficiently than C. albicans yeast. Treatment of neutrophils with a galectin-3 (gal3) blocking antibody inhibited phagocytosis of C. parapsilosis yeast and C. albicans hyphae, but not C. albicans yeast. The majority of neutrophil gal3 was expressed intracellularly and was secreted from neutrophils after treatment with C. parapsilosis mannan. When neutrophils were treated with exogenous gal3, phagocytosis of both C. albicans and C. parapsilosis yeast increased. Exposure of neutrophils to C. parapsilosis yeast increased phagocytosis of C. albicans yeast and was inhibited by gal3 blocking antibody. Taken together, these data indicate that gal3 secreted from neutrophils may act as a pro-inflammatory autocrine/paracrine signal in neutrophil phagocytosis and suggest that gal3 has a unique role in neutrophil response to C. parapsilosis yeast and C. albicans hyphae distinct from C. albicans yeast.

The Faseb Journal, Apr 1, 2014

The Pediatric Infectious Disease Journal, Mar 1, 2008

Very low birth weight infants (VLBW, &amp... more Very low birth weight infants (VLBW, < or = 1500 g) are at increased risk for invasive disease caused by fungi, and colonization is an important risk factor. This study was designed to examine the effect of maternal flora on Candida colonization of VLBW infants. Body site samples were collected within 24 hours of delivery from mothers who gave birth to VLBW infants, from their infants at birth, and then weekly for 12 weeks or until death or discharge. Yeast isolates were identified as Candida albicans by standard methods and typed by DNA fingerprinting using a C. albicans strain-specific DNA probe (CARE-2). Sixty-six percent (50/76) of mothers were colonized with yeast and 51% (39/76) of their infants had a Candida species isolated at least once. Of 46 infants born to C. albicans-colonized mothers, 18 (39%) became colonized with C. albicans. Twenty-two percent (17/76) of the infants in the study were colonized with C. albicans by 1 week of age; 76% of these infants (13/17) were born to C. albicans-colonized mothers suggesting vertical transmission. DNA fingerprinting was performed on these 13 mother-infant pairs and 11 pairs demonstrated identical band patterns, confirming vertical transmission. However, of all infants colonized with C. albicans by the first week of age, just 65% (11/17) had a maternal source, and among all infants colonized at any time point, only 41% (11/27) became colonized by vertical transmission. Both vertical and horizontal transmission contribute to Candida colonization of VLBW infants in the neonatal intensive care unit.

The Journal of infectious diseases, Jan 2, 2015

Release of neutrophil extracellular traps (NETs) is a significant antimicrobial host defense mech... more Release of neutrophil extracellular traps (NETs) is a significant antimicrobial host defense mechanism in adults. In neonates, fungal sepsis is a frequent cause of morbidity and mortality and may be a consequence of inadequate neutrophil defense functions. Like neutrophils from adult donors, we found that neutrophils from neonates formed robust cellular aggregates and released NETs in response to fungal β-glucan and Candida albicans hyphae when presented with extracellular matrix. Therefore, in response to fungal stimulation, neonatal neutrophils are capable of NETosis. Neonate susceptibility to fungal infections may not be due to an inability of their neutrophils to produce NETs.

Journal of human lactation : official journal of International Lactation Consultant Association, Jan 26, 2015

Colonization increases risk for invasive candidiasis in neonates. Breast milk host defense protei... more Colonization increases risk for invasive candidiasis in neonates. Breast milk host defense proteins may affect yeast colonization of infants. This study aimed to evaluate breast milk host defense proteins relative to yeast colonization in infants. Infants admitted for longer than 72 hours to the neonatal intensive care unit at Women & Infants Hospital in Providence, Rhode Island, were eligible. After consent, expressed breast milk and swabs from oral, rectal, and inguinal sites from infants were cultured weekly for 12 weeks, or until discharge, transfer, or death. Breast milk was tested for levels of human lactoferrin, lysozyme, apolipoprotein J, mucin-1, dermcidin, and soluble CD14 using commercial ELISA. Concentrations of these components were compared in breast milk received by infants who were colonized or not colonized with yeast. From an original cohort of 130, 61 infants had samples available for this subanalysis. A convenience sample of stored breast milk was analyzed. Media...

Virulence, 2015

Candida parapsilosis is a fungal pathogen that is associated with hematogenously disseminated dis... more Candida parapsilosis is a fungal pathogen that is associated with hematogenously disseminated disease in premature neonates, acutely ill or immunocompromised patients. In cell culture, C. parapsilosis cells are actively and avidly endocytosed by endothelial cells via actin polymerization mediated by N-WASP. Here we present evidence that C. parapsilosis that were internalized by endothelial cells remained alive, and avoided being acidified or otherwise damaged via the host cell. Internalized fungal cells reproduced intracellularly and eventually burst out of the host endothelial cell. When neutrophils were added to endothelium and C. parapsilosis, they patrolled the endothelial surface and efficiently killed most adherent fungal cells prior to endocytosis. But after endocytosis by endothelial cells, internalized fungal cells evaded neutrophil killing. Silencing endothelial N-WASP blocked endocytosis of C. parapsilosis and left fungal cells stranded on the cell surface, where they were susceptible to neutrophil killing. These observations suggest that for C. parapsilosis to escape from the bloodstream, fungi may adhere to and be internalized by endothelial cells before being confronted and phagocytosed by a patrolling leukocyte. Once internalized by endothelial cells, C. parapsilosis may safely replicate to cause further rounds of infection. Immunosurveillance of the intravascular lumen by leukocytes crawling on the endothelial surface and rapid killing of adherent yeast may play a major role in controlling C. parapsilosis dissemination and infected endothelial cells may be a significant reservoir for fungal persistence.

Current Fungal Infection Reports, 2015

Candida species are the leading cause of invasive fungal infections in premature infants. Associa... more Candida species are the leading cause of invasive fungal infections in premature infants. Associated with substantial morbidity and mortality, these infections represent serious and sometimes catastrophic complications in the course of hospitalization of a preterm infant in the neonatal intensive care unit. Although virulence factors of Candida and the host defense mechanisms that are important in protection from candidiasis have been the subject of intensive study, considerably less is known about the features of this disease that are specific to premature neonates. As animal models for neonatal candidiasis have been developed, efforts to understand the similarities and differences of candidiasis in the neonatal host relative to other immunocompromised patients have begun to provide insights to these questions.

Evidence-Based Handbook of Neonatology, 2011

Med Mycol, Feb 8, 2010

Candida species are associated with invasive fungal infections, and C. parapsilosis has become in... more Candida species are associated with invasive fungal infections, and C. parapsilosis has become increasingly prevalent. As key antifungal effector cells, the function of human neutrophils confronting C. parapsilosis was investigated. We hypothesized that interaction between neutrophils and Candida species may not be uniform. Opsonins were omitted from these studies to understand the antifungal mechanisms at their most basic level. Human neutrophils underwent phagocytosis of C. parapsilosis with much higher efficiency than C. albicans. Immunofluorescence assays with βglucan specific antibody detected more surface exposed β-glucan on C. parapsilosis than C. albicans. However, blockade of the β-glucan receptor, Dectin-1, reduced phagocytosis of C. albicans but not C. parapsilosis. Inclusion of excess β-glucan, mannan, or chitin also had no effect on phagocytosis of C. parapsilosis. Consistent with the difference in phagocytosis, neutrophils mediated damage to C. parapsilosis but not C. albicans in assays of residual metabolic activity. C. parapsilosis was more sensitive to oxidative stress, and inclusion of antioxidant in toxicity assays decreased neutrophil mediated damage, suggesting that generation of reactive oxygen species contributes to the mechanism of toxicity. These data suggest that the interaction between neutrophils and Candida species is not uniform and may partially account for differences observed in the epidemiology and natural history of infections caused by these species.

Textbook of Clinical Pediatrics, 2012

Journal of Infectious Diseases, 2015

Release of neutrophil extracellular traps (NETs) is a significant antimicrobial host defense mech... more Release of neutrophil extracellular traps (NETs) is a significant antimicrobial host defense mechanism in adults. In neonates, fungal sepsis is a frequent cause of morbidity and mortality and may be a consequence of inadequate neutrophil defense functions. Like neutrophils from adult donors, we found that neutrophils from neonates formed robust cellular aggregates and released NETs in response to fungal β-glucan and Candida albicans hyphae when presented with extracellular matrix. Therefore, in response to fungal stimulation, neonatal neutrophils are capable of NETosis. Neonate susceptibility to fungal infections may not be due to an inability of their neutrophils to produce NETs.

Molecular microbiology, 1996

Capsules are well-studied components of the bacterial surface that modulate interactions between ... more Capsules are well-studied components of the bacterial surface that modulate interactions between the cell and its environment. Generally composed of polysaccharide, they are key virulence determinants in invasive infections in humans and other animals. Genetic determinants involved in capsule expression have been isolated from a number of organisms, but perhaps the best characterized is the kps cluster of Escherichia coli K1. In this review, the current understanding of the functions of the kps gene products is summarized. Further, a proposed mechanistic model for capsule expression is presented and discussed. The model is based on the premise that the numerous components of the kps cluster form a hetero-oligomeric complex responsible for synthesis and concurrent translocation of the capsular polysialic acid through sites of inner and outer membrane fusion. We view the ATP-binding cassette (ABC) transporter, KpsMT, to be central to the functioning of the complex, interacting with th...

Medical Mycology, 2013

Recent in vitro studies have implicated galectin-3 as an important receptor in host recognition a... more Recent in vitro studies have implicated galectin-3 as an important receptor in host recognition and response to specific Candida species; however, its role in protection against disseminated candidiasis in vivo has not been evaluated. This study investigated the importance of galectin-3 in host defense against systemic infection with the highly virulent species Candida albicans, and the less virulent species, C. parapsilosis. Mice deficient in galectin-3 (gal3-/-) were more susceptible to infection than wild-type (WT) mice. When infected with C. albicans, gal3-/- mice died significantly faster and exhibited a trend towards increased fungal burden and increased abscess formation in infected brains compared to WT mice. When infected with C. parapsilosis, gal3-/- mice had significantly higher renal fungal burdens and abscess formation compared to WT mice. To evaluate whether galectin-3 may contribute to susceptibility to candidiasis in human infants, galectin-3 levels in sera of newborn infants, a patient population uniquely susceptible to infections with both C. albicans and C. parapsilosis, were compared to serum galectin-3 levels of adults. Galectin-3 levels were significantly lower in newborn infant sera compared to adult sera. These data indicate that galectin-3 plays an important role in a murine model of disseminated candidiasis and suggest a potential mechanism of neonatal susceptibility to these infections.

Medical Mycology, 2010

Candida species are associated with invasive fungal infections, and C. parapsilosis has become in... more Candida species are associated with invasive fungal infections, and C. parapsilosis has become increasingly prevalent. As key antifungal effector cells, the function of human neutrophils confronting C. parapsilosis was investigated. We hypothesized that interaction between neutrophils and Candida species may not be uniform. Opsonins were omitted from these studies to understand the antifungal mechanisms at their most basic level. Human neutrophils underwent phagocytosis of C. parapsilosis with much higher efficiency than C. albicans. Immunofluorescence assays with βglucan specific antibody detected more surface exposed β-glucan on C. parapsilosis than C. albicans. However, blockade of the β-glucan receptor, Dectin-1, reduced phagocytosis of C. albicans but not C. parapsilosis. Inclusion of excess β-glucan, mannan, or chitin also had no effect on phagocytosis of C. parapsilosis. Consistent with the difference in phagocytosis, neutrophils mediated damage to C. parapsilosis but not C. albicans in assays of residual metabolic activity. C. parapsilosis was more sensitive to oxidative stress, and inclusion of antioxidant in toxicity assays decreased neutrophil mediated damage, suggesting that generation of reactive oxygen species contributes to the mechanism of toxicity. These data suggest that the interaction between neutrophils and Candida species is not uniform and may partially account for differences observed in the epidemiology and natural history of infections caused by these species.

Journal of Chemical Education, 2013

ABSTRACT Efforts to provide active research context to introductory courses in basic sciences are... more ABSTRACT Efforts to provide active research context to introductory courses in basic sciences are likely to better engage learners and provide a framework for relevant concepts. A simple teaching and learning experiment was conducted to use concepts in organic chemistry to solve problems in the life sciences. Bryant University is a liberal arts university with new programs in biological and environmental sciences. This laboratory exercise was developed for introductory organic chemistry and designed to highlight its applicability to the biological sciences. Students participated in an ongoing project to identify antigens on the surface of Candida albicans hyphae by testing a variety of lipid extraction procedures and characterizing the fatty acid and carbohydrate composition of their extractions by thin-layer chromatography and gas chromatography–mass spectrometry. Student extracts were also tested in an immunoblot assay with a specific antibody fragment (scFv) that recognizes an unknown component of the cell surface of C. albicans hyphae. In order to build communication skills, students were required to prepare and present posters detailing the project and their findings.

Infection and Immunity, 2003

Specific antibody opsonization significantly enhances the level of phagocytosis of Candida in the... more Specific antibody opsonization significantly enhances the level of phagocytosis of Candida in the absence of complement. Furthermore, we have described a system using a recombinant human antibody single-chain variable fragment that allows a comparative study of phagocytosis of multiple Candida species opsonized via a common antigen.

Fungal Genetics and Biology, 2010

As a means to study surface proteins involved in the yeast to hypha transition, human monoclonal ... more As a means to study surface proteins involved in the yeast to hypha transition, human monoclonal antibody fragments (single-chain variable fragments, scFv) have been generated that bind to antigens expressed on the surface of Candida albicans yeast and/or hyphae. A cDNA expression library was constructed from hyphae, and screened for immunoreactivity with scFv5 as a means to identify its cognate antigen. A reactive clone contained the 3 0 end of the C. albicans gene, orf 19.7136, designated SPT6 based on homology to Saccharomyces cerevisiae, where its product functions as a transcription elongation factor. A mutant containing a homozygous deletion of SPT6 was isolated, demonstrating that unlike S. cerevisiae, deletion of this gene in C. albicans is not lethal. Growth of this strain was severely impaired, however, as was its capacity to undergo filamentous growth. Reactivity with scFv5 was not detected in the mutant strain, although its impaired growth complicates the interpretation of this finding. To assess C. albicans SPT6 function, expression of the C. albicans gene was induced in a defined S. cerevisiae spt6 mutant. Partial complementation was seen, confirming that the C. albicans and S. cerevisiae genes are functionally related in these species.

FEMS Immunology & Medical Microbiology, 2006

This study evaluates the conditions in which peripheral blood mononuclear cells mediate toxicity ... more This study evaluates the conditions in which peripheral blood mononuclear cells mediate toxicity to Candida albicans opsonized with heat-inactivated human serum. Serum concentrations as low as 1% resulted in 50% inhibition of C. albicans metabolic activity after incubation with peripheral blood mononuclear cells at an effector to target ratio of 8. Measurable inhibition was also achieved at lower effector to target ratios and lower serum concentrations, and at least a portion of the metabolic inhibition reflected fungal cell death. Depletion of C. albicans-specific antibody decreased the toxic effect while opsonization with purified human IgG restored toxicity, and cell-cell contact between peripheral blood mononuclear cells and fungus was required. Depletion of or enrichment for monocytes from the peripheral blood mononuclear cells preparation diminished the toxic effect and the monocytic cell line, THP-1, was likewise incapable of toxicity. These studies provide evidence that antibody augments antifungal host defense and underscore the complex interrelationship between humoral and cellular immunity in these infections.

Expert Review of Anti-infective Therapy, 2012

Invasive candidiasis is a common problem in premature infants that leads to high morbidity and mo... more Invasive candidiasis is a common problem in premature infants that leads to high morbidity and mortality. Although Candida albicans has historically been the most prominent species involved in these infections and has therefore been the subject of the most study, Candida parapsilosis is increasing in frequency, and neonates are disproportionately affected. This article reviews unique aspects of the epidemiology of this organism as well as strategies for prophylaxis against invasive candidiasis in general. Additionally, important differences between C. parapsilosis and C. albicans are coming to light related to virulence determinants and interactions with components of host immunity. These developments are reviewed while highlighting the significant gaps in our understanding that remain to be elucidated.

Cellular Microbiology, 2013

Candida albicans causes the majority of invasive candidiasis in immunocompromised adults while Ca... more Candida albicans causes the majority of invasive candidiasis in immunocompromised adults while Candida parapsilosis is a leading cause of neonatal candidiasis. While much work has focused on how the immune system recognizes and responds to C. albicans, less is known about host interaction with C. parapsilosis. This study investigates the human neutrophil phagocytic response to these species. Neutrophils underwent phagocytosis of C. parapsilosis yeast and C. albicans hyphae much more efficiently than C. albicans yeast. Treatment of neutrophils with a galectin-3 (gal3) blocking antibody inhibited phagocytosis of C. parapsilosis yeast and C. albicans hyphae, but not C. albicans yeast. The majority of neutrophil gal3 was expressed intracellularly and was secreted from neutrophils after treatment with C. parapsilosis mannan. When neutrophils were treated with exogenous gal3, phagocytosis of both C. albicans and C. parapsilosis yeast increased. Exposure of neutrophils to C. parapsilosis yeast increased phagocytosis of C. albicans yeast and was inhibited by gal3 blocking antibody. Taken together, these data indicate that gal3 secreted from neutrophils may act as a pro-inflammatory autocrine/paracrine signal in neutrophil phagocytosis and suggest that gal3 has a unique role in neutrophil response to C. parapsilosis yeast and C. albicans hyphae distinct from C. albicans yeast.

The Faseb Journal, Apr 1, 2014

The Pediatric Infectious Disease Journal, Mar 1, 2008

Very low birth weight infants (VLBW, &amp... more Very low birth weight infants (VLBW, < or = 1500 g) are at increased risk for invasive disease caused by fungi, and colonization is an important risk factor. This study was designed to examine the effect of maternal flora on Candida colonization of VLBW infants. Body site samples were collected within 24 hours of delivery from mothers who gave birth to VLBW infants, from their infants at birth, and then weekly for 12 weeks or until death or discharge. Yeast isolates were identified as Candida albicans by standard methods and typed by DNA fingerprinting using a C. albicans strain-specific DNA probe (CARE-2). Sixty-six percent (50/76) of mothers were colonized with yeast and 51% (39/76) of their infants had a Candida species isolated at least once. Of 46 infants born to C. albicans-colonized mothers, 18 (39%) became colonized with C. albicans. Twenty-two percent (17/76) of the infants in the study were colonized with C. albicans by 1 week of age; 76% of these infants (13/17) were born to C. albicans-colonized mothers suggesting vertical transmission. DNA fingerprinting was performed on these 13 mother-infant pairs and 11 pairs demonstrated identical band patterns, confirming vertical transmission. However, of all infants colonized with C. albicans by the first week of age, just 65% (11/17) had a maternal source, and among all infants colonized at any time point, only 41% (11/27) became colonized by vertical transmission. Both vertical and horizontal transmission contribute to Candida colonization of VLBW infants in the neonatal intensive care unit.

The Journal of infectious diseases, Jan 2, 2015

Release of neutrophil extracellular traps (NETs) is a significant antimicrobial host defense mech... more Release of neutrophil extracellular traps (NETs) is a significant antimicrobial host defense mechanism in adults. In neonates, fungal sepsis is a frequent cause of morbidity and mortality and may be a consequence of inadequate neutrophil defense functions. Like neutrophils from adult donors, we found that neutrophils from neonates formed robust cellular aggregates and released NETs in response to fungal β-glucan and Candida albicans hyphae when presented with extracellular matrix. Therefore, in response to fungal stimulation, neonatal neutrophils are capable of NETosis. Neonate susceptibility to fungal infections may not be due to an inability of their neutrophils to produce NETs.

Journal of human lactation : official journal of International Lactation Consultant Association, Jan 26, 2015

Colonization increases risk for invasive candidiasis in neonates. Breast milk host defense protei... more Colonization increases risk for invasive candidiasis in neonates. Breast milk host defense proteins may affect yeast colonization of infants. This study aimed to evaluate breast milk host defense proteins relative to yeast colonization in infants. Infants admitted for longer than 72 hours to the neonatal intensive care unit at Women & Infants Hospital in Providence, Rhode Island, were eligible. After consent, expressed breast milk and swabs from oral, rectal, and inguinal sites from infants were cultured weekly for 12 weeks, or until discharge, transfer, or death. Breast milk was tested for levels of human lactoferrin, lysozyme, apolipoprotein J, mucin-1, dermcidin, and soluble CD14 using commercial ELISA. Concentrations of these components were compared in breast milk received by infants who were colonized or not colonized with yeast. From an original cohort of 130, 61 infants had samples available for this subanalysis. A convenience sample of stored breast milk was analyzed. Media...

Virulence, 2015

Candida parapsilosis is a fungal pathogen that is associated with hematogenously disseminated dis... more Candida parapsilosis is a fungal pathogen that is associated with hematogenously disseminated disease in premature neonates, acutely ill or immunocompromised patients. In cell culture, C. parapsilosis cells are actively and avidly endocytosed by endothelial cells via actin polymerization mediated by N-WASP. Here we present evidence that C. parapsilosis that were internalized by endothelial cells remained alive, and avoided being acidified or otherwise damaged via the host cell. Internalized fungal cells reproduced intracellularly and eventually burst out of the host endothelial cell. When neutrophils were added to endothelium and C. parapsilosis, they patrolled the endothelial surface and efficiently killed most adherent fungal cells prior to endocytosis. But after endocytosis by endothelial cells, internalized fungal cells evaded neutrophil killing. Silencing endothelial N-WASP blocked endocytosis of C. parapsilosis and left fungal cells stranded on the cell surface, where they were susceptible to neutrophil killing. These observations suggest that for C. parapsilosis to escape from the bloodstream, fungi may adhere to and be internalized by endothelial cells before being confronted and phagocytosed by a patrolling leukocyte. Once internalized by endothelial cells, C. parapsilosis may safely replicate to cause further rounds of infection. Immunosurveillance of the intravascular lumen by leukocytes crawling on the endothelial surface and rapid killing of adherent yeast may play a major role in controlling C. parapsilosis dissemination and infected endothelial cells may be a significant reservoir for fungal persistence.