Early-Onset Invasive Candidiasis in Extremely Low Birth Weight Infants: Perinatal Acquisition Predicts Poor Outcome

Background

Neonatal invasive candidiasis (IC) presenting in the first week of life is less common and less well described than later-onset IC. Risk factors, clinical features, and disease outcomes have not been studied in early-onset disease (EOD, ≤7 days) or compared to late-onset disease (LOD, >7 days).

Methods

All extremely low birth weight (ELBW, <1000 g) cases with IC and controls from a multicenter study of neonatal candidiasis enrolled from 2001 to 2003 were included in this study. Factors associated with occurrence and outcome of EOD in ELBW infants were determined.

Results

Forty-five ELBW infants and their 84 matched controls were included. Fourteen (31%) ELBW infants had EOD. Birth weight <750 g, gestation <25 weeks, chorioamnionitis, and vaginal delivery were all strongly associated with EOD. Infection with Candida albicans, disseminated disease, pneumonia, and cardiovascular disease were significantly more common in EOD than in LOD. The EOD case fatality rate (71%) was higher than in LOD (32%) or controls (15%) (P = .0001). The rate of neurodevelopmental impairment and mortality combined was similar in EOD (86%) and LOD (72%), but higher than in controls (32%; P = .007).

Conclusions

ELBW infants with EOD have a very poor prognosis compared to those with LOD. The role of perinatal transmission in EOD is supported by its association with chorioamnionitis, vaginal delivery, and pneumonia. Dissemination and cardiovascular involvement are common, and affected infants often die. Empiric treatment should be considered for ELBW infants delivered vaginally who have pneumonia and whose mothers have chorioamnionitis or an intrauterine foreign body.

Oropharyngeal Candidiasis in HIV Infection: Analysis of Impaired Mucosal Immune Response to Candida albicans in Mice Expressing the HIV-1 Transgene

IL-17-producing Th17 cells are of critical importance in host defense against oropharyngeal candidiasis (OPC). Speculation about defective Th17 responses to oral C. albicans infection in the context of HIV infection prompted an investigation of innate and adaptive immune responses to Candida albicans in transgenic mice expressing the genome of HIV-1 in immune cells and displaying an AIDS-like disease. Defective IL-17 and IL-22-dependent mucosal responses to C. albicans were found to determine susceptibility to OPC in these transgenic mice. Innate phagocytes were quantitatively and functionally intact, and individually dispensable for control of OPC and to prevent systemic dissemination of Candida to deep organs. CD8+ T-cells recruited to the oral mucosa of the transgenic mice limited the proliferation of C. albicans in these conditions of CD4+ T-cell deficiency. Therefore, the immunopathogenesis of OPC in the context of HIV infection involves defective T-cell-mediated immunity, failure of crosstalk with innate mucosal immune effector mechanisms, and compensatory cell responses, which limit Candida infection to the oral mucosa and prevent systemic dissemination.

Defective IL-17- and IL-22-dependent mucosal host response to Candida albicans determines susceptibility to oral candidiasis in mice expressing the HIV-1 transgene

BACKGROUND

The tissue-signaling cytokines IL-17 and IL-22 are critical to host defense against oral Candida albicans infection, by their induction of oral antimicrobial peptide expression and recruitment of neutrophils. Mucosal Th17 cells which produce these cytokines are preferentially depleted in HIV-infected patients. Here, we tested the hypothesis that defective IL-17- and IL-22-dependent host responses to C. albicans determine the phenotype of susceptibility to oropharyngeal candidiasis (OPC) in transgenic (Tg) mice expressing HIV-1.

RESULTS

Naïve CD4+ T-cells and the differentiated Th1, Th2, Th17, Th1Th17 and Treg lineages were all profoundly depleted in cervical lymph nodes (CLNs) of these Tg mice. However, naive CD4+ cells from Tg mice maintained the capacity to differentiate into these lineages in response to polarizing cytokines in vitro. Expression of Il17, Il22, S100a8 and Ccl20 was enhanced in oral mucosal tissue of non-Tg, but not of Tg mice, after oral infection with C. albicans. Treatment of infected Tg mice with the combination of IL-17 and IL-22, but not IL-17 or Il-22 alone, significantly reduced oral burdens of C. albicans and abundance of Candida hyphae in the epithelium of tongues of infected Tg mice, and restored the ability of the Tg mice to up-regulate expression of S100a8 and Ccl20 in response to C. albicans infection.

CONCLUSIONS

These findings demonstrate that defective IL-17- and IL-22-dependent induction of innate mucosal immunity to C. albicans is central to the phenotype of susceptibility to OPC in these HIV transgenic mice.

Invasive candidiasis in low birth weight preterm infants: risk factors, clinical course and outcome in a prospective multicenter study of cases and their matched controls

Background

This multicenter prospective study of invasive candidiasis (IC) was carried out to determine the risk factors for, incidence of, clinical and laboratory features, treatment and outcome of IC in infants of birth weight <1250 g.

Methods

Neonates <1250 g with IC and their matched controls (2:1) were followed longitudinally and descriptive analysis was performed. Survivors underwent neurodevelopmental assessment at 18 to 24 months corrected age. Neurodevelopmental impairment (NDI) was defined as blindness, deafness, moderate to severe cerebral palsy, or a score <70 on the Bayley Scales of Infant Development 2nd edition. Multivariable analyses were performed to determine risk factors for IC and predictors of mortality and NDI.

Results

Cumulative incidence rates of IC were 4.2%, 2.2% and 1.5% for birth-weight categories <750 g, <1000 g, <1500 g, respectively. Forty nine infants with IC and 90 controls were enrolled. Necrotizing enterocolitis (NEC) was the only independent risk factor for IC (p = 0.03). CNS candidiasis occurred in 50% of evaluated infants, while congenital candidiasis occurred in 31%. Infants with CNS candidiasis had a higher mortality rate (57%) and incidence of deafness (50%) than the overall cohort of infants with IC. NDI (56% vs. 33%; p = 0.017) and death (45% vs. 7%; p = 0.0001) were more likely in cases than in controls, respectively. IC survivors were more likely to be deaf (28% vs. 7%; p = 0.01). IC independently predicted mortality (p = 0.0004) and NDI (p = 0.018).

Conclusion

IC occurred in 1.5% of VLBW infants. Preceding NEC increased the risk of developing IC. CNS candidiasis is under-investigated and difficult to diagnose, but portends a very poor outcome. Mortality, deafness and NDI were independently significantly increased in infants with IC compared to matched controls.

Characteristics and outcome of infants with candiduria in neonatal intensive care - a Paediatric Investigators Collaborative Network on Infections in Canada (PICNIC) study

BACKGROUND

There is limited information in the literature on the presentation and prognosis of candidal urinary tract infection (UTI) in infants in the neonatal intensive care unit (NICU).

METHODS

This was a prospective cohort study performed in 13 Canadian NICUs. Infants with candidal UTI without extra-renal candidal infection at presentation were enrolled.

RESULTS

Thirty infants fit the study criteria. Median birth weight and gestational age were 2595 grams (range 575-4255) and 35 weeks (range 24-41) with 10 infants being < 30 weeks gestation. The most common primary underlying diagnosis was congenital heart disease (n = 10). The median age at initial diagnosis was 16 days (range 6-84 days). Renal ultrasonography findings were compatible with possible fungal disease in 15 of the 26 infants (58%) in whom it was performed. Treatment was variable, but fluconazole and either amphotericin B deoxycholate or lipid-based amphotericin B in combination or sequentially were used most frequently. Extra-renal candidiasis subsequently developed in 4 infants. In 2 of these 4 infants, dissemination happened during prolonged courses of anti-fungal therapy. Three of 9 deaths were considered to be related to candidal infection. No recurrences of candiduria or episodes of invasive candidiasis following treatment were documented.

CONCLUSION

Candidal UTI in the NICU population occurs both in term infants with congenital abnormalities and in preterm infants, and is associated with renal parenchymal disease and extra-renal dissemination. A wide variation in clinical approach was documented in this multicenter study. The overall mortality rate in these infants was significant (30%). In one third of the deaths, Candida infection was deemed to be a contributing factor, suggesting the need for antifungal therapy with repeat evaluation for dissemination in infants who are slow to respond to therapy.

Oral mucosal cell response to Candida albicans in transgenic mice expressing HIV-1

Controlled studies on the immunopathogenesis of mucosal candidiasis in HIV infection have been hampered by the lack of a relevant animal model. We have previously reported that oral Candida infection in CD4C/HIV transgenic mice expressing gene products of HIV-1 in immune cells and developing an AIDS-like disease closely mimics oropharyngeal candidiasis in human HIV infection. The role of defective dendritic cells and CD4+ T cells in impaired induction of protective immunity and in the phenotype of chronic oral carriage of C. albicans can now be investigated under controlled conditions in these transgenic mice.

The nuclear GTPase Gsp1p can affect proper telomeric function through the Sir4 protein inSaccharomyces cerevisiae

The small Ras-like GTPase Ran/Gsp1p is a highly conserved nuclear protein required for the nucleocytoplasmic trafficking of macromolecules. Recent findings suggest that the Ran/Gsp1p pathway may have additional roles in several aspects of nuclear structure and function, including spindle assembly, nuclear envelope formation, nuclear pore complex assembly and RNA processing. Here, we provide evidence that Gsp1p can regulate telomeric function in Saccharomyces cerevisiae. We show that overexpression of PRP20, encoding the Gsp1p GDP/GTP nuclear exchange factor, specifically weakens telomeric silencing without detectably affecting nucleocytoplasmic transport. In addition to this silencing defect, we show that Rap1p and Sir3p delocalize from their normal telomeric foci. Interestingly, Gsp1p was found to interact genetically and physically with the telomeric component Sir4p. Taken together, these results suggest that the GSP1 pathway could regulate proper telomeric function in yeast through Sir4p.

Altered CD4+T Cell Phenotype and Function Determine the Susceptibility to Mucosal Candidiasis in Transgenic Mice Expressing HIV-1

The impairments of protective mucosal immunity which cause susceptibility to oropharyngeal candidiasis (OPC) in HIV infection remain undefined. This study used a model of OPC in CD4C/HIV MutA transgenic (Tg) mice expressing Rev, Env, and Nef of HIV-1 to investigate the role of transgene expressing dendritic cells (DCs) and CD4+ T cells in maintenance of chronic oral carriage of Candida albicans. DCs were depleted in the Tg mice and had an immature phenotype, with low expression of MHC class II and IL-12. CD4+ T cells were quantitatively reduced in the oral mucosa, cervical lymph nodes (CLNs) and peripheral blood of the Tg mice, and displayed a polarization toward a nonprotective Th2 response. Proliferation of CLN CD4+ T cells from infected Tg mice in response to C. albicans Ag in vitro was abrogated and the cells failed to acquire an effector phenotype. Coculture of C. albicans-pulsed DCs with CD4+ T cells in vitro showed that Tg expression in either or both of these cell populations sharply reduced the proliferation of CD4+ T cells and their production of IL-2. Finally, transfer of naive non-Tg CD4+ T cells into these Tg mice restored proliferation to C. albicans Ag and sharply reduced oral burdens of C. albicans. Overall, these results indicate that defective CD4+ T cells primarily determine the susceptibility to chronic carriage of C. albicans in these Tg mice.

CD8+ T cells but not polymorphonuclear leukocytes are required to limit chronic oral carriage of Candida albicans in transgenic mice expressing human immunodeficiency virus type 1

Candida albicans causes oropharyngeal candidiasis (OPC) but rarely disseminates to deep organs in human immunodeficiency virus (HIV) infection. Here, we used a model of OPC in CD4C/HIV(Mut) transgenic (Tg) mice to investigate the role of polymorphonuclear leukocytes (PMNs) and CD8+ T cells in limiting candidiasis to the mucosa. Numbers of circulating PMNs and their oxidative burst were both augmented in CD4C/HIV(MutA) Tg mice expressing rev, env, and nef of HIV type 1 (HIV-1), while phagocytosis and killing of C. albicans were largely unimpaired compared to those in non-Tg mice. Depletion of PMNs in these Tg mice did not alter oral or gastrointestinal burdens of C. albicans or cause systemic dissemination. However, oral burdens of C. albicans were increased in CD4C/HIV(MutG) Tg mice expressing only the nef gene of HIV-1 and bred on a CD8 gene-deficient background (CD8-/-), compared to control or heterozygous CD8+/- CD4C/HIV(MutG) Tg mice. Thus, CD8+ T cells contribute to the host defense against oral candidiasis in vivo, specifically in the context of nef expression in a subset of immune cells.

Animal models in the analysis of Candida host-pathogen interactions

An increasingly diverse array of clinically relevant animal models of candidiasis have been established that mimic both the immune perturbations of the host and tissue-specific features of candidiasis in humans. Cause-and-effect analysis of Candida host-pathogen interactions using these animal models has made a quantum leap forward in the genomic era, with the concurrent construction of C. albicans mutants with targeted mutations of putative virulence factors, the application of microarrays and other emerging technologies to comprehensively assess C. albicans gene expression in vivo, and construction of transgenic and knockout mice to simulate specific host immunodeficiencies. The opportunity to combine these powerful tools will yield an unprecedented wealth of new information on the molecular and cellular pathogenesis of candidiasis.

Immunopathogenesis of oropharyngeal candidiasis in human immunodeficiency virus infection

Oropharyngeal and esophageal candidiases remain significant causes of morbidity in human immunodeficiency virus (HIV)-infected patients, despite the dramatic ability of antiretroviral therapy to reconstitute immunity. Notable advances have been achieved in understanding, at the molecular level, the relationships between the progression of HIV infection, the acquisition, maintenance, and clonality of oral candidal populations, and the emergence of antifungal resistance. However, the critical immunological defects which are responsible for the onset and maintenance of mucosal candidiasis in patients with HIV infection have not been elucidated. The devastating impact of HIV infection on mucosal Langerhans' cell and CD4(+) cell populations is most probably central to the pathogenesis of mucosal candidiasis in HIV-infected patients. However, these defects may be partly compensated by preserved host defense mechanisms (calprotectin, keratinocytes, CD8(+) T cells, and phagocytes) which, individually or together, may limit Candida albicans proliferation to the superficial mucosa. The availability of CD4C/HIV transgenic mice expressing HIV-1 in immune cells has provided the opportunity to devise a novel model of mucosal candidiasis that closely mimics the clinical and pathological features of candidal infection in human HIV infection. These transgenic mice allow, for the first time, a precise cause-and-effect analysis of the immunopathogenesis of mucosal candidiasis in HIV infection under controlled conditions in a small laboratory animal.

Effect of the echinocandin caspofungin on expression of Candida albicans secretory aspartyl proteinases and phospholipase in vitro

Although the echinocandin caspofungin primarily inhibits the synthesis of cell wall 1,3-beta-D-glucan, its fungicidal activity could also potentially perturb the expression of virulence factors involved in the ability of Candida albicans to cause infection. Expression of the C. albicans secretory aspartyl proteinase (SAP) and phospholipase B (PLB) virulence genes was determined by reverse transcription-PCR after the addition of caspofungin to cells grown for 15 h in Sabouraud dextrose broth. In cells that remained viable, expression of SAP1 to SAP3, SAP7 to SAP9, and PLB1 was unaltered after exposure to fungicidal concentrations (4 to 16 micro g/ml) of caspofungin over a period of 7 h. However, expression of SAP5 increased steadily beginning 1 h after exposure to caspofungin. These results indicate that caspofungin is rapidly fungicidal against C. albicans, before any suppression of SAP or PLB1 gene expression can occur.

Mucosal candidiasis in transgenic mice expressing human immunodeficiency virus type 1

The availability of CD4C/HIV(MutA) transgenic (Tg) mice expressing human immunodeficiency virus type 1 in immune cells and developing an AIDS-like disease has provided the opportunity to devise a model of mucosal candidiasis that closely mimics the clinical and pathologic features of candidal infection in human AIDS. After intraoral infection with Candida albicans, oral burdens were strikingly elevated in the Tg mice, compared with non-Tg littermates (P<.05), during primary infection, a 6-10-week carrier state, and a marked terminal outgrowth preceding death. The chronic carrier state was absent in the non-Tg mice because of clearing of C. albicans. Candida hyphae penetrated the epithelium of the oral cavity, esophagus, and cardial-atrium fold of the stomach, accompanied by a mononuclear cell infiltrate. Immunohistochemical analysis suggested that decreased frequencies of major histocompatibility complex class II-expressing cells, combined with reduced CD4+ cells, may underlie the susceptibility to mucosal candidiasis in these Tg mice.

Evidence for differential expression of candida albicans virulence genes during oral infection in intact and human immunodeficiency virus type 1-transgenic mice

To comprehensively assess the in vivo expression of Candida albicans hydrolytic enzyme genes during oropharyngeal candidiasis (OPC), a controlled sequential analysis of the temporal expression of individual members of the SAP (secretory aspartyl proteinase) gene family and PLB1 (phospholipase B) in a murine model of OPC was conducted. Acute infections in intact C3H and DBA/2 mice were terminated by clearance of C. albicans within 7 days after oral inoculation, but transgenic (Tg) mice expressing human immunodeficiency virus type 1 were persistently colonized until a final outgrowth before death. In contrast to the sustained expression of other SAP genes and PLB1, SAP7 and SAP8 were conspicuously distinguished by their transient expression in both intact and Tg mice. SAP5 and SAP9 were most strongly expressed throughout the course of infection in the Tg mice. These findings indicate that expression of individual members of the C. albicans SAP gene family is differentially regulated during experimental OPC.

Overexpression of Candida albicans secretory aspartyl proteinase 2 and its expression in Saccharomyces cerevisiae do not augment virulence in mice

To elucidate the implications of secreted aspartyl proteinase (Sap)2p in the pathogenesis of Candida infections, the SAP2 gene was expressed in Saccharomyces cerevisiae and overexpressed in Candida albicans. The coding region of SAP2, including its signal sequence and propeptide, was amplified by PCR and cloned downstream of the S. cerevisiae or C. albicans ADH1 promoter. Plasmid expression of SAP2 in S. cerevisiae showed that the signal peptide was functional. Integrative transformation of S. cerevisiae and C. albicans was accomplished by homologous recombination within the URA3 locus for S. cerevisiae and the SAP2 locus for C. albicans. Negative control transformants carried plasmids either without the SAP2 insert or with mutated sap2. S. cerevisiae and C. albicans transformants showed similar growth rates to their parental strains or negative controls, when grown in medium containing amino acids. However, in medium with BSA as sole nitrogen source, constitutive expression of SAP2 enabled S. cerevisiae to grow and increased the growth rate of C. albicans. In both media, only S. cerevisiae transformants harbouring SAP2 secreted the enzyme, as confirmed by proteinase activity assays and immunoblotting. When C. albicans was grown in amino acids medium, the enzyme was detected exclusively in transformants constitutively expressing SAP2. However, in BSA medium these strains secreted enzyme earlier and secreted higher amounts of enzyme and total proteinase activity. In pathogenicity studies in intact mice, expression of Sap2p as a sole putative virulence factor did not cause S. cerevisiae to become virulent and constitutive overexpression of SAP2 did not augment virulence of C. albicans in experimental oral or systemic infection.