Trends in immunotherapy of fungal infections

Cryptococcosis and Cryptococcal Meningitis: A Narrative Review and the Up-to-Date Management Approach

Cryptococcosis is a fungal infectious disease that enormously impacts human health worldwide. Cryptococcal meningitis is the most severe disease caused by the fungus Cryptococcus, and can lead to death, if left untreated. Many patients develop resistance and progress to death even after treatment. It requires a prolonged treatment course in people with AIDS. This narrative review provides an evidence-based summary of the current treatment modalities and future trial options, including newer ones, namely, 18B7, T-2307, VT-1598, AR12, manogepix, and miltefosine. This review also evaluated the management and empiric treatment of cryptococcus meningitis. The disease can easily evade diagnosis with subacute presentation. Despite the severity of the disease, treatment options for cryptococcosis remain limited, and more research is needed.

Animal models of invasive mycoses

Animal models of invasive fungal infections have been developed and are applied in a huge number of different animal species for a number of research purposes, for example, the study of pathogenesis, defense mechanisms, and therapeutic strategies. From the different models, which in most cases are based on the same fungal species and often the same strain, as in spontaneous human infections, fundamental results and knowledge of the diagnosis, progression, prophylaxis, and therapy have been achieved. However, in all models, one should be critical with respect to mimicking the disease entity of humans, which is often the focus of the research. In many of the models for instance, the time course is different to the one of humans, and in others, the propensity for localization and containment in specific organs does not parallel the situation in humans. Nevertheless, many animal models of invasive mycoses have proven valuable in a number of research areas. With regard to new generations of anti-mycotic drugs, the models play an essential role in demonstrating antifungal activity, as well as in demonstrating the absence of toxic side effects, a critical step which cannot be accomplished by in vitro studies.

Sepsis in the era of data-driven medicine: personalizing risks, diagnoses, treatments and prognoses

Sepsis is a series of clinical syndromes caused by the immunological response to infection. The clinical evidence for sepsis could typically attribute to bacterial infection or bacterial endotoxins, but infections due to viruses, fungi or parasites could also lead to sepsis. Regardless of the etiology, rapid clinical deterioration, prolonged stay in intensive care units and high risk for mortality correlate with the incidence of sepsis. Despite its prevalence and morbidity, improvement in sepsis outcomes has remained limited. In this comprehensive review, we summarize the current landscape of risk estimation, diagnosis, treatment and prognosis strategies in the setting of sepsis and discuss future challenges. We argue that the advent of modern technologies such as in-depth molecular profiling, biomedical big data and machine intelligence methods will augment the treatment and prevention of sepsis. The volume, variety, veracity and velocity of heterogeneous data generated as part of healthcare delivery and recent advances in biotechnology-driven therapeutics and companion diagnostics may provide a new wave of approaches to identify the most at-risk sepsis patients and reduce the symptom burden in patients within shorter turnaround times. Developing novel therapies by leveraging modern drug discovery strategies including computational drug repositioning, cell and gene-therapy, clustered regularly interspaced short palindromic repeats -based genetic editing systems, immunotherapy, microbiome restoration, nanomaterial-based therapy and phage therapy may help to develop treatments to target sepsis. We also provide empirical evidence for potential new sepsis targets including FER and STARD3NL. Implementing data-driven methods that use real-time collection and analysis of clinical variables to trace, track and treat sepsis-related adverse outcomes will be key. Understanding the root and route of sepsis and its comorbid conditions that complicate treatment outcomes and lead to organ dysfunction may help to facilitate identification of most at-risk patients and prevent further deterioration. To conclude, leveraging the advances in precision medicine, biomedical data science and translational bioinformatics approaches may help to develop better strategies to diagnose and treat sepsis in the next decade.

Immune cell response to Candida cell wall mannan derived branched α-oligomannoside conjugates in mice

BACKGROUND

Constructs composed of cell wall mannan-derived moieties conjugated to immunogenic proteins could be promising agents for induction of protective anti-Candida immune responses.

METHODS

This report is focused on the cellular immune response differences induced by BSA-based conjugates bearing synthetic α-1,6-branched oligomannosides. For monitoring of the immune responses following active immunization we evaluated changes in the frequencies of T and B lymphocytes and their activation status in the blood and spleen. We compared the immunization-induced changes of co-stimulatory molecules CD80 and CD86 expression on blood neutrophils and Th1/Th2 polarization of the immune response based on IFN-γ, TNF-α (pro-Th1), IL-4, and IL-10 (pro-Th2) cytokines levels and induction of IL-17.

RESULTS

The results pointed out a comparable effect of the conjugates on the modulation of T and B lymphocytes frequencies in blood and spleen. Both conjugates induced upregulation of CD25 surface antigen on CD4(+) T lymphocytes, independently on the structural differences of oligosaccharides. The differences in structure of oligomannoside antigens or conjugate constructs were reflected in the increase of co-stimulatory molecules CD80 and CD86 expression on neutrophils, and in induced cytokine response. M5-BSA conjugate induced only a slight increase in CD80 expression but a significant increase in IFN-γ, TNF-α, and IL-10. M6-BSA conjugate induced a significant increase of CD80 expression and increase of TNF-α, IL-4, and IL-10.

CONCLUSION

Obtained data demonstrate the importance of cellular immune response analysis for investigation of immunomodulatory properties of oligomannoside-protein conjugates.

Immunomodulator tuftsin increases the susceptibility ofCryptococcus neoformansto liposomal amphotericin B in immunocompetent BALB/c mice

The co-administration of immunomodulators and antibiotics has been proved very successful for treatment of opportunistic infectious diseases. In the present study, we evaluated the combination of liposomal amphotericin B (lip-Amp B) and immunomodulator tuftsin to cure Cryptococcus neoformans infection in BALB/c mice. Mice infected with C. neoformans were treated with Amp B deoxycholate and tuftsin free or tuftsin-loaded Amp B liposomes. The results of the present study demonstrated higher efficacy of tuftsin-loaded Amp B liposomes against experimental murine cryptococcosis, in terms of enhanced survival rate and reduced fungal burden in organs (lungs and brain) of the treated mice. Interestingly, pre-treatment of mice with liposomal tuftsin before challenging them with the C. neoformans infection resulted in 100% survival of the treated animals followed by treatment with lip-Amp B. Immunomodulator-based therapy seems likely to be more beneficial for treatment of fungal infectious diseases.

Animal models: an important tool in mycology

Animal models of fungal infections are, and will remain, a key tool in the advancement of the medical mycology. Many different types of animal models of fungal infection have been developed, with murine models the most frequently used, for studies of pathogenesis, virulence, immunology, diagnosis, and therapy. The ability to control numerous variables in performing the model allows us to mimic human disease states and quantitatively monitor the course of the disease. However, no single model can answer all questions and different animal species or different routes of infection can show somewhat different results. Thus, the choice of which animal model to use must be made carefully, addressing issues of the type of human disease to mimic, the parameters to follow and collection of the appropriate data to answer those questions being asked. This review addresses a variety of uses for animal models in medical mycology. It focuses on the most clinically important diseases affecting humans and cites various examples of the different types of studies that have been performed. Overall, animal models of fungal infection will continue to be valuable tools in addressing questions concerning fungal infections and contribute to our deeper understanding of how these infections occur, progress and can be controlled and eliminated.

CpG oligodeoxynucleotides protect mice from lethal challenge with Candida albicans via a pathway involving tumor necrosis factor-alpha-dependent interleukin-12 induction

In this study, we have attempted to determine whether the systemic administration of CpG oligodeoxynucleotide (CpG-ODN) 1826 would protect mice against systemic lethal Candida albicans infection. CpG-ODNs were found completely to protect mice from death and also reduced the growth of C. albicans in the kidneys. The administration of CpG-ODNs resulted in early interleukin (IL)-12 mRNA expression in the kidneys and an increase in serum IL-12 levels. The protective activity of CpG-ODN was abolished in IL-12-deficient (IL-12-/-) mice, thereby indicating the IL-12-dependency inherent to the effects of CpG-ODN. The protective effect of CpG-ODN was not associated with the activity of NF-kappaB. Interestingly, in tumor necrosis factor (TNF)-alpha-deficient (TNF-/-) mice CpG-ODN neither exerted protective effects nor induced IL-12 expression. These data indicate that CpG-ODN protects animals against lethal C. albicans challenge via a pathway that involves the TNF-alpha-dependent induction of IL-12.

Itraconazole IV nanosuspension enhances efficacy through altered pharmacokinetics in the rat

The goal of this research was to evaluate an intravenous itraconazole nanosuspension dosage form, relative to a solution formulation, in the rat. Itraconazole was formulated as a nanosuspension by a tandem process of microcrystallization followed by homogenization. Acute toxicity, pharmacokinetics, and distribution were studied in the rat, and compared with a solution formulation of itraconazole. Efficacy was studied in an immunocompromised rat model, challenged with a lethal dose of either itraconazole-sensitive or itraconazole-resistant C. albicans. Itraconazole nanosuspension was tolerated at significantly higher doses compared with a solution formulation. Pharmacokinetics of the nanosuspension were altered relative to the solution formulation. C(max) was reduced and t(1/2) was much prolonged. This occurred due to distribution of the nanosuspension to organs of the monocyte phagocytic system (MPS), followed by sustained release from this IV depot. The higher dosing of the drug, enabled in the case of the nanosuspension, led to higher kidney drug levels and reduced colony counts. Survival was also shown to be superior relative to the solution formulation. Thus, formulation of itraconazole as a nanosuspension enhances efficacy of this antifungal agent relative to a solution formulation, because of altered pharmacokinetics, leading to increased tolerability, permitting higher dosing and resultant tissue drug levels.

Protection from direct cerebral cryptococcus infection by interferon-gamma-dependent activation of microglial cells

The brain represents a significant barrier for protective immune responses in both infectious disease and cancer. We have recently demonstrated that immunotherapy with anti-CD40 and IL-2 can protect mice against disseminated Cryptococcus infection. We now applied this immunotherapy using a direct cerebral cryptococcosis model to study direct effects in the brain. Administration of anti-CD40 and IL-2 significantly prolonged the survival time of mice infected intracerebrally with Cryptococcus neoformans. The protection was correlated with activation of microglial cells indicated by the up-regulation of MHC II expression on brain CD45(low)CD11b(+) cells. CD4(+) T cells were not required for either the microglial cell activation or anticryptococcal efficacy induced by this immunotherapy. Experiments with IFN-gamma knockout mice and IFN-gammaR knockout mice demonstrated that IFN-gamma was critical for both microglial cell activation and the anticryptococcal efficacy induced by anti-CD40/IL-2. Interestingly, while peripheral IFN-gamma production and microglial cell activation were observed early after treatment, negligible IFN-gamma was detected locally in the brain. These studies indicate that immunotherapy using anti-CD40 and IL-2 can augment host immunity directly in the brain against C. neoformans infection and that IFN-gamma is essential for this effect.

Immune response and immunotherapy to Cryptococcus infections

Cryptococcus neoformans is a ubiquitous fungus that can cause lifethreatening infections during immunosuppressive states such as acquired immunodeficiency syndrome (AIDS) and after bone marrow transplantation (BMT). Infected individuals normally succumb to meningitis and meningoencephalitis caused by dissemination of C. neoformans to the brain. In this review, we analyze the current understanding of the interaction between host immune response and C. neoformans as well as the current state of immunotherapeutic strategies for treating cryptococcosis.

Animal models testing monotherapy versus combination antifungal therapy: lessons learned and future directions

PURPOSE OF REVIEW

The continued rise in serious fungal infections and rises in therapy failure dictate that more efficacious therapies be developed. Combination therapy using available drugs is an attractive choice, yet primarily only anecdotal clinical data are available. We review here data from animal models as an indicator of future potential.

RECENT FINDINGS

The primary data are from murine studies and we will briefly review chemotherapeutic combination studies, some showing benefit over monotherapy and some showing no benefit over monotherapy. In addition, we will address the potential of immunotherapy in combination with conventional therapy.

SUMMARY

The data derived from animal model studies of antifungal drug efficacy have proven to be predictive of clinical utility. Studies on combination therapy will prove useful to the clinician in evaluating courses of treatment, especially where clinical-trial data are not available or probable in the future.

Incorporation of amphotericin B in tuftsin-bearing liposomes showed enhanced efficacy against systemic cryptococcosis in leucopenic mice

OBJECTIVES

The role of the immunomodulator tuftsin in enhancing the antifungal activity of liposomal amphotericin B against Cryptococcus neoformans in leucopenic mice was assessed.

METHODS

In the present study, we investigated the antifungal activity of amphotericin B liposomes with tuftsin grafted on the surface. Mice were treated with free amphotericin B as well as liposomal formulations after C. neoformans infection. For prophylactic studies, mice were pre-treated with liposomal tuftsin (50 microg/mL) for three consecutive days prior to C. neoformans infection (7 x 10(5) cfu/mouse). Chemotherapy, with tuftsin-free and tuftsin-bearing amphotericin B liposomes, was started 24 h post C. neoformans infection. The role of tuftsin in immunoaugmentative therapy was assessed by survival and cfu of treated mice.

RESULTS

Amphotericin B entrapped in tuftsin-bearing liposomes showed increased anticryptococcal activity in the murine model. Moreover, tuftsin pre-treatment further augmented the antifungal activity of liposomal amphotericin B in leucopenic mice. Incorporation of tuftsin in liposomes resulted in increased anticryptococcal activity of liposomal amphotericin B compared with amphotericin B deoxycholate and conventional liposomal amphotericin B formulations.

CONCLUSIONS

The enhanced anticryptococcal activity of amphotericin B in tuftsin-liposomes can be attributed to the immune-stimulating property of tuftsin. Tuftsin activates the key immune cells, due to the presence of its receptors on macrophages and neutrophils, for a better fight against pathogens. Simultaneous liposome-mediated delivery of amphotericin B to the site of infection kills the pathogens more effectively.

Prophylaxis with meropenem of septic complications in acute pancreatitis: a randomized, controlled trial versus imipenem

OBJECTIVES

Prophylactic antibiotics are helpful in decreasing the incidence of septic complications in acute pancreatitis. The aim of this study was to compare the efficacy of meropenem, a new carbapenem antibiotic, with that of imipenem, which is the standard prophylactic treatment in patients with severe acute pancreatitis.

METHODS

One hundred seventy-six patients with necrotizing pancreatitis were prospectively randomized to prophylactic treatment with 0.5 g meropenem t.i.d. intravenously or 0.5 g imipenem q.i.d. intravenously. The occurrence of infection of pancreatic necrosis, rate of extrapancreatic infections, systemic and local complications, need for surgery, mortality rate, and length of hospitalization were recorded for each group. When a septic complication of pancreatic necrosis was suspected, fine needle aspiration with cultures of the sample was performed. Surgery was performed in cases of verified infected necrosis.

CONCLUSION

No difference was observed between patients treated with meropenem and those treated with imipenem in terms of incidence of pancreatic infection (11.4% versus 13.6%) and extrapancreatic infections (21.6% versus 23.9%) and clinical outcome. Meropenem is as effective as imipenem in preventing septic complications of patients with severe acute pancreatitis.

Protective Effects of a Protein-Bound Polysaccharide, PSK, Against Candida albicans Infection in Syngeneic Tumor-Bearing Mice via Th1 Cell Functions

We investigated the effects of a protein-bound polysaccharide, PSK, on the resistance of tumor-bearing mice against Candida albicans infection. In BALB/c mice that had received subcutaneous (sc) transplantation of fibrosarcoma Meth A, viable fungal counts were increased in the kidney and the mean survival period was shortened after challenge with C. albicans, compared with healthy mice. Oral administration of PSK to such mice resulted in a significant decrease of viable fungal counts and a prolongation of the mean survival period. The ratio of CD4-positive T cells in the spleen was decreased in noninfected tumor-bearing mice and the decrease was prevented by PSK, although in vitro anticandida activities of phagocytes were not significantly affected by tumor burden or PSK. Further, intracellular interferon (IFN)-gamma productivity was enhanced and the number of IFN-gamma-producing CD4-positive T cells was enhanced by PSK. PSK enhanced the gene expression of interleukin (IL)-12 and IFN-gamma in the spleen of tumor-bearing mice inoculated with C. albicans. Treatments with anti-IL-12 or anti-IFN-gamma antibody reduced the anti-infectious effects of PSK. These findings suggest that the protective effect of PSK on sublethal inoculation with C. albicans in tumor-bearing mice is possibly mediated by Th1 cell functions.

Relative contributions of myeloperoxidase and NADPH-oxidase to the early host defense against pulmonary infections with Candida albicans and Aspergillus fumigatus

Generation of oxidative products by phagocytic cells is known to be an important host defense mechanism directed toward killing of invading microorganisms. The importance of two major oxidant-producing enzymes, myeloperoxidase (MPO) and NADPH-oxidase, in in vivo fungicidal action was directly compared in genetically engineered mice. Both MPO-deficient (MPO-/-) and NADPH-oxidase-deficient (X-linked chronic granulomatous disease [X-CGD]) mice showed increased susceptibility to pulmonary infections with Candida albicans and Aspergillus fumigatus compared with normal mice, and the X-CGD mice exhibited shorter survivals than MPO-/- mice. This increased mortality of X-CGD mice was associated with a 10- to 100-fold increased outgrowth of the fungi in their organs during the first 6 days. These results suggest that superoxide (O2-) produced by NADPH-oxidase is more important than hypochlorous acid (HOCl) produced by MPO, although both oxidative products obviously contribute to the host defense against pulmonary infection with those fungi. We also observed that MPO-/-/X-CGD double knockout mice showed comparable levels of susceptibility to the X-CGD mice against C. albicans and A. funigatus, indicating that MPO is unable to play a role in host defense in the absence of NADPH-oxidase. This strongly suggests that hydrogen peroxide, the precursor of HOCl, is solely derived from O2- produced by NADPH-oxidase.

[Antifungal activity of Caryocar brasiliensis (Caryocaraceae) against Cryptococcus neoformans]

The widespread occurrence of cryptococcosis mainly in immunocompromised patients and the side effects of available drugs which are effective against this mycosis have led investigators to search for new antimycotic agents. Caryocar brasiliensis derived compounds were investigated against Cryptococcus neoformans using the agar dilution method. Based on MIC values, the best results were obtained with a concentration of < 250 g/mL of cuticular waxes of the Caryocar brasiliensis leaf collected during the dry period (170.8mm of precipitation) which inhibited the growth of 91.3% (21/23) Cryptococcus neoformans isolates.

Cytokine and chemokine production by human oral and vaginal epithelial cells in response to Candida albicans

Oropharyngeal and vaginal candidiases are the most common forms of mucosal fungal infections and are primarily caused by Candida albicans, a dimorphic fungal commensal organism of the gastrointestinal and lower female reproductive tracts. Clinical and experimental observations suggest that local immunity is important in host defense against candidiasis. Accordingly, cytokines and chemokines are present at the oral and vaginal mucosa during C. albicans infections. Since mucosal epithelial cells produce a variety of cytokines and chemokines in response to microorganisms and since C. albicans is closely associated with mucosal epithelial cells as a commensal, we sought to identify cytokines and/or chemokines produced by primary oral and vaginal epithelial cells and cell lines in response to C. albicans. The results showed that proinflammatory cytokines were produced by oral and/or vaginal epithelial cells at various levels constitutively with considerable interleukin-1alpha (IL-1alpha) and tumor necrosis factor alpha, but not IL-6, produced in response to C. albicans. In contrast, Th1-type (IL-12 and gamma interferon) and Th2-type-immunoregulatory (IL-10 and transforming growth factor beta) cytokines and the chemokines monocyte chemoattractant protein 1 and IL-8 were produced in low to undetectable concentrations with little additional production in response to C. albicans. Taken together, these results indicate that cytokines and chemokines are variably produced by oral and vaginal epithelial cells constitutively, as well as in response to C. albicans, and are predominated by proinflammatory cytokines.

Adjunctive immune therapy for fungal infections

Fungal infections in immunocompromised patients can pose difficult problems in clinical management, because the available antifungal chemotherapy is often unable to eradicate the infection in these people. Hence, the use of immune modulating therapy to augment impaired host immune responses--and thus enhance the efficacy of antifungal drugs--is a reasonable approach to improve the prognosis of fungal infections. Advances in biotechnology have produced a variety of biological response modifiers with the potential to serve as adjunctive immune therapy for the treatment of fungal infections, including cytokines, monoclonal antibodies, and cell growth factors. In recent years, immune-modulating therapies have been studied in an effort to define their potential use for the treatment of fungal infections. Much of the available information on the use of this approach is encouraging and invites further investigation--with the caveats that the information is mostly anecdotal and that immune-modulating therapy occasionally has produced adverse effects.

Protective effects of a protein-bound polysaccharide, PSK, on Candida albicans infection in mice via tumor necrosis factor-alpha induction

We investigated the protective mechanism of a protein-bound polysaccharide, PSK, against lethal infection with Candida albicans (C. albicans) in mice. (1) In BALB/c mice inoculated intravenously with C. albicans, the intraperitoneal (ip) administration of PSK increased survival rates and prolonged the survival period depending on the time of administration, the dosage, and the size of fungal inoculum; the maximal effect was obtained when PSK 250 mg/kg was ip administered to mice 24 h before inoculation of 1 x 10(6) C. albicans (30 days survivors showed 60% and the mean survival period of mice with fatal infection increased 209%). (2) The protective effect of PSK was significantly decreased in mice treated with cyclophosphamide or carrageenan, or in mice treated previously with anti-tumor necrosis factor-alpha (TNF-alpha) antibody. (3) The administration of PSK significantly enhanced the expression of TNF-alpha gene in spleen and increased leukocyte functions from 6 h to 1 day after inoculation. (4) When the PSK fraction subjected to hydrolysis with beta1-3 glucanase or hydrazine was used instead of PSK, the anti-fungal activities were significantly decreased. These findings suggested that the protective effect of PSK on lethal C. albicans infection in mice was mainly produced via TNF-alpha functions, and that beta 1-3 glucan and protein moiety in PSK molecule were involved in the expression of the activities.

A clinical perspective for the management of invasive fungal infections: focus on IDSA guidelines. Infectious Diseases Society of America

Invasive fungal infections, especially candidiasis and aspergillosis, are a major cause of morbidity and mortality. Many controversies surround the management of these infections. A critical overview of the recent Infectious Diseases Society of America practice guidelines is provided, as are comments on both the conundrums and future perspectives in medical mycology.

Antifungal activity of volatile constituents of Eugenia dysenterica leaf oil

The essential oil from the hydrodistillation of Eugenia dysenterica leaves consisted mainly of beta-caryophyllene and alpha-humulene as the major sesquiterpene, while limonene and alpha-thujene were the major monoterpene hydrocarbons. The main oxygenated mono and sesquiterpene constituents were alpha-terpineol and beta-caryophyllene oxide, respectively. The oil was investigated against eight strains of Candida albicans, 35 strains of Cryptococcus neoformans var. neoformans, and two C. neoformans var. gattii isolated from HIV-infected individuals with candidosis or cryptococcal meningitis using the agar dilution method. Based on the minimal inhibitory concentration (MIC) values, the most significant results were obtained against Cryptococcus strains. It was observed that 22 strains were inhibited at a concentration of 250 microg/ml, whereas four exhibited potent inhibition with MIC values below 125 microg/ml against 10(6) UFC/ml organisms. We found MICs > or = 3.12 microg/ml for 91.6, 50 and 30% of all Cryptococcus strains in relation of amphotericin B, fluconazole and itraconazole, respectively.

“Emergency” granulopoiesis in G-CSF–deficient mice in response to Candida albicans infection

Granulocyte colony-stimulating factor (G-CSF) is a glycoprotein believed to play an important role in regulating granulopoiesis both at steady state and during an “emergency” situation. Generation of G-CSF and G-CSF receptor–deficient mice by gene targeting has demonstrated unequivocally the importance of G-CSF in the regulation of baseline granulopoiesis. This study attempted to define the physiologic role of G-CSF during an emergency situation by challenging a cohort of wild-type and G-CSF–deficient mice with Candida albicans. Interestingly, after infection, G-CSF–deficient mice developed an absolute neutrophilia that was observed both in blood and bone marrow. In addition, 3 days after Candida infection increased numbers of granulocyte-macrophage (GM) and macrophage (M) progenitors were observed in the bone marrow of G-CSF–deficient mice. Of the cytokines surveyed, interleukin (IL)-6 levels in serum were elevated; interestingly, levels of IL-6 were higher and more sustained in G-CSF–deficient mice infected with C albicans than similarly infected wild-type mice. Despite the higher levels of serum IL-6, this cytokine is dispensable for the observed neutrophilia because candida-infected IL-6–deficient mice, or mice simultaneously deficient in G-CSF and IL-6, developed neutrophilia. Similarly, mice lacking both G-CSF and GM-CSF developed absolute neutrophilia and had elevated numbers of GM and M progenitors in the bone marrow; thus, G-CSF and GM-CSF are dispensable for promoting the emergency response to candidal infection.

“Emergency” granulopoiesis in G-CSF–deficient mice in response to Candida albicans infection

Granulocyte colony-stimulating factor (G-CSF) is a glycoprotein believed to play an important role in regulating granulopoiesis both at steady state and during an “emergency” situation. Generation of G-CSF and G-CSF receptor–deficient mice by gene targeting has demonstrated unequivocally the importance of G-CSF in the regulation of baseline granulopoiesis. This study attempted to define the physiologic role of G-CSF during an emergency situation by challenging a cohort of wild-type and G-CSF–deficient mice with Candida albicans. Interestingly, after infection, G-CSF–deficient mice developed an absolute neutrophilia that was observed both in blood and bone marrow. In addition, 3 days after Candida infection increased numbers of granulocyte-macrophage (GM) and macrophage (M) progenitors were observed in the bone marrow of G-CSF–deficient mice. Of the cytokines surveyed, interleukin (IL)-6 levels in serum were elevated; interestingly, levels of IL-6 were higher and more sustained in G-CSF–deficient mice infected with C albicans than similarly infected wild-type mice. Despite the higher levels of serum IL-6, this cytokine is dispensable for the observed neutrophilia because candida-infected IL-6–deficient mice, or mice simultaneously deficient in G-CSF and IL-6, developed neutrophilia. Similarly, mice lacking both G-CSF and GM-CSF developed absolute neutrophilia and had elevated numbers of GM and M progenitors in the bone marrow; thus, G-CSF and GM-CSF are dispensable for promoting the emergency response to candidal infection.

Interleukin 10 suppresses phagocytic and antihyphal activities of human neutrophils

We investigated the effects of human interleukin 10 (IL-10) on the antibacterial and antifungal activities of human neutrophils (PMNs) against Staphylococcus aureus and Candida albicans. Incubation of PMNs from healthy volunteers with 20-100 ng/ml of IL-10 at 37 degrees C for 1 h suppressed phagocytosis of serum-opsonized S. aureus (P=0.02) and blastoconidia of C. albicans (P<0.01). In contrast, 2-100 ng/ml of IL-10 had no effect on superoxide anion production upon stimulation with phorbol myristate acetate, N-formylmethionyl leucyl phenylalanine, C. albicans blastoconidia or pseudohyphae; neither did it significantly affect conidiocidal or bactericidal activities of PMNs. However, 20-100 ng/ml of IL-10 significantly decreased PMN-induced damage of C. albicans pseudohyphae (P=0.008). The suppression of phagocytic activity of PMNs against S. aureus and blastoconidia of C. albicans as well as the impairment of PMN-induced hyphal damage may have important implications for understanding the immunosuppressive profile of IL-10 in clinical usage.

Increased susceptibility to systemic candidiasis in interleukin-6 deficient mice

Interleukin-6 (IL-6) is a multifunctional cytokine that regulates multiple aspects of the innate immune response. It has been recently shown that endogenous IL-6 is crucial for an efficient defence against severe infections with Gram-negative and Gram-positive bacteria. The aim of the present study was to investigate the role of endogenous IL-6 in the defence against infection with the yeast Candida albicans. During experimental candidemia, IL-6 deficient mice (IL-6-/-) had a decreased survival and an increased fungal load in their organs when compared with IL-6+/+ controls, despite increased plasma concentrations of tumour necrosis factor-alpha (TNF), interleukin-1 alpha (IL-1 alpha) and IL-1 beta, IL-6-/- mice were not able to mount an efficient neutrophil response during the infection. When mice were rendered neutropenic by cyclophosphamide, neutropenic IL-6-/- mice were equally susceptible to C. albicans when compared to neutropenic IL-6+/+ mice, implying that neutrophils mediate the beneficial effect of endogenous IL-6. In conclusion, IL-6-/- mice are more susceptible to disseminated candidiasis, and the effect of IL-6 is most likely mediated by neutrophils.

Increased Susceptibility of TNF-α Lymphotoxin-α Double Knockout Mice to Systemic Candidiasis Through Impaired Recruitment of Neutrophils and Phagocytosis of Candida albicans

TNF-α and lymphotoxin-α (LT) are members of the TNF family, and these cytokines play crucial roles in the defense against infection with Candida albicans. The aim of the present study was to investigate the role of endogenous TNF and LT during disseminated candidiasis in TNF−/−LT−/− knockout mice. The TNF- and LT-deficient animals had a significantly increased mortality following C. albicans infection compared with control mice, and this was due to a 10- to 1000-fold increased outgrowth of the yeast in their organs. No differences between TNF−/−LT−/− mice and TNF+/+LT+/+ were observed when mice were rendered neutropenic, suggesting that activation of neutrophils mediates the beneficial effects of endogenous TNF and LT. Histopathology of the organs, combined with neutrophil recruitment experiments, showed a dramatic delay in the neutrophil recruitment at the sites of Candida infection in the TNF−/−LT−/− mice. Moreover, the neutrophils of deficient animals were less potent to phagocytize Candida blastospores than control neutrophils. In contrast, the killing of Candida and the oxygen radical production did not differ between neutrophils of TNF−/−LT−/− and TNF+/+LT+/+ mice. Peak circulating IL-6 was significantly higher in TNF−/−LT−/− mice during infection. Peritoneal macrophages of TNF−/−LT−/− mice did not produce TNF, and synthesized significantly lower amounts of IL-1α, IL-1β, IL-6, and macrophage-inflammatory protein-1α than macrophages of TNF+/+LT+/+ animals did. In conclusion, endogenous TNF and/or LT contribute to host resistance to disseminated candidiasis, and their absence in TNF−/−LT−/− mice renders the animals susceptible through impaired recruitment of neutrophils and impaired phagocytosis of C. albicans.

Aspergillus fumigatus and aspergillosis

Aspergillus fumigatus is one of the most ubiquitous of the airborne saprophytic fungi. Humans and animals constantly inhale numerous conidia of this fungus. The conidia are normally eliminated in the immunocompetent host by innate immune mechanisms, and aspergilloma and allergic bronchopulmonary aspergillosis, uncommon clinical syndromes, are the only infections observed in such hosts. Thus, A. fumigatus was considered for years to be a weak pathogen. With increases in the number of immunosuppressed patients, however, there has been a dramatic increase in severe and usually fatal invasive aspergillosis, now the most common mold infection worldwide. In this review, the focus is on the biology of A. fumigatus and the diseases it causes. Included are discussions of (i) genomic and molecular characterization of the organism, (ii) clinical and laboratory methods available for the diagnosis of aspergillosis in immunocompetent and immunocompromised hosts, (iii) identification of host and fungal factors that play a role in the establishment of the fungus in vivo, and (iv) problems associated with antifungal therapy.

Systemic mycoses during prophylactical use of liposomal amphotericin B (Ambisome) after liver transplantation

We investigated the prophylactical administration of liposomal amphotericin B (Ambisome) in the early phase after liver transplantation (LTx). Fifty-eight patients received Ambisome prophylactically after LTx. Ambisome (1 mg kg-1 day-1) was given intravenously for 7 days after LTx. Immunosuppressive prophylaxis was cyclosporin A (CsA) based in 11 patients. Forty-seven patients had a tacrolimus-based immunosuppressive regimen. CsA and tacrolimus dosages were adjusted to trough levels of 150-250 ng ml-1 (EMIT) and 5-15 ng ml-1 (MEIA II) respectively. Three patients died from sepsis due to Aspergillus fumigatus infection. Reasons for a fatal outcome were foudroyant Aspergillus pneumonia in a patient transplanted for fulminant hepatic failure on post-operative day (pod) 8; Aspergillus sepsis with severe endocardidtis in a patient with two retransplantations for graft non/dysfunction on pod 24; and disseminated aspergillosis due to Aspergillus fumigatus in a patient retransplanted for primary non-function (pod 19). All three patients underwent haemofiltration for renal failure. One patient with Candida albicans sepsis (pod 4) recovered under increased dosage of Ambisome (3 mg kg-1 per day). Ambisome (1 mg kg-1 per day) seems to be beneficial against systemic Candida infections. However, the onset of systemic Aspergillus infections could not be prevented. Obviously, higher Ambisome doses appear to be necessary against Aspergillus. We recommend the use of Ambisome (3 mg kg-1 per day) for patients with risk factors such as graft dys-/non-function, retransplantation, haemofiltration and complicated acute liver failure to prevent invasive aspergillosis.

Gastrointestinal infections in the immunocompromised host

Gastrointestinal infections are a frequent and important complication of immunodeficiency diseases and immunosuppressive therapy. Such infections may be severe, prolonged, or even fatal, whereas the same infections are typically mild and transient in immunocompetent persons. In this regard, the strong association between HIV-induced immunosuppression and the increased prevalence of severe enteric infections is strong evidence of the link between immune function and defense against enteric pathogens. Because gastrointestinal infections in immunocompromised persons are frequently severe and life-threatening, a vigorous approach to the diagnostic evaluation and therapeutic management is advocated by many clinical investigators. In this review, we summarize the important new developments, particularly during the past year, regarding gastrointestinal infections in immunocompromised persons.

Invasive sinus aspergillosis in apparently immunocompetent hosts

OBJECTIVES

to describe the clinical, microbiological and pathological features of invasive sinus aspergillosis affecting immunocompetent hosts, and to identify the risk factors for mortality.

METHODS

we report three apparently immunocompetent patients with invasive sinus aspergillosis, and review all cases reported in the English literature since 1987, the year in which the triazole antifungal agents were introduced.

RESULTS

twenty-nine patients (including three of our own) were identified. The presenting symptoms were non-specific and indistinguishable from viral, bacterial or allergic causes of sinusitis. The findings on computed tomography scan were also non-specific, and histopathology and culture of sinus tissue biopsy had low yield. These factors, along with the mistaken impression that Aspergillus can only affect immunocompromised hosts, frequently delayed the diagnosis. Fifty-nine percent of patients either failed therapy or died. The following factors were associated with a poor prognosis: delayed diagnosis, intracranial extension of infection, and histopathology demonstrating hyphal invasion of blood vessel or tissue. Complete surgical extirpation was the key element of successful therapy; antifungal agents played an adjunctive role.

CONCLUSIONS

invasive sinus aspergillosis carries high morbidity and mortality, even in immunocompetent hosts. To improve outcome, the diagnosis must be recognized early, before the organism can invade the central nervous system or vascular structures. Aggressive surgical resection of the infected areas is of utmost importance in the management of this infection.

Beta-N-acetylhexosaminidase: a target for the design of antifungal agents

This review provides biochemical, analytical, and biological background information relating to beta-N-acetylhexosaminidase (HexNAc'ase; EC 3.2.1.52) as an emerging target for the design of low-molecular-weight antifungals. The article includes the following: (1) a biochemical description of HexNAc'ase (reaction catalyzed, nomenclature, and mechanism of action) that sets it apart from other, similar enzymes; (2) an overview and a critical evaluation of methods to assay the enzyme, including in crude extracts (photo- and fluorometric procedures with model substrates; HPLC/pulsed amperometric detection of N-acetylglucosamine and chito-oligomers; end-point vs. rate measurements); (3) a summary of some general characteristics of HexNAc'ases from fungi and organisms of other types (Km values, substrate preference, and glycoconjugation); (4) an hypothesis of a specific target function of wall-associated HexNAc'ase (a component of the assembly of surface-located enzymes effecting a continuous turnover and remodelling of the wall fabric through its combined hydrolytic and transglycosylating activities, and a mediator enzyme acting in concert with chitinase and chitin synthase to provide for the controlled lysis and synthesis of chitin during growth); (5) a tabulation of the structural formulae of reaction-based HexNAc'ase inhibitors with Ki values < or = 100 microM (some of them representing transition state mimics that could serve as leads for the development of new antifungals); and (6) an outline of approaches towards the establishment of a three-dimensional model of HexNAc'ase suitable for a truly rational design of antimycotics as well as agricultural fungicides.