Immunotherapy for fungal infections

Promising immunotherapeutic targets for treating candidiasis

In the last twenty years, there has been a significant increase in invasive fungal infections, which has corresponded with the expanding population of individuals with compromised immune systems. As a result, the mortality rate linked to these infections remains unacceptably high. The currently available antifungal drugs, such as azoles, polyenes, and echinocandins, face limitations in terms of their diversity, the escalating resistance of fungi and the occurrence of significant adverse effects. Consequently, there is an urgent need to develop new antifungal medications. Vaccines and antibodies present a promising avenue for addressing fungal infections due to their targeted antifungal properties and ability to modulate the immune response. This review investigates the structure and function of cell wall proteins, secreted proteins, and functional proteins within C. albicans. Furthermore, it seeks to analyze the current advancements and challenges in macromolecular drugs to identify new targets for the effective management of candidiasis.

Direct antimicrobial effects of chemokines on Cryptococcus spp, with special emphasis on a 'CXC' chemokine

Cryptococcus species are ingenious human pathogens that are widespread globally. They continue to cause over 200,000 deaths per year. Presently due to the rise in resistance and therapy failure, it is necessary to shift the focus to an alternate therapeutic strategy against this pathogen. One promising approach is to emphasize the host defense system in order to develop more precise and customized treatment strategies. In this regard, research has revealed that interferon-γ-inducible CXCL10 chemokine, amongst other chemokines spanning both CXC and CC categories, has a direct killing effect in vitro against Cryptococcus neoformans and Cryptococcus gattii, with a significantly greater microbicidal effect against the former. Moreover, when CXCL10 is used in combination with CCL5, there is a significant reduction in the survival of C. gattii at normal-serum level concentration, indicating a previously unreported synergistic effect of these two chemokines. Confocal and STED microscopic studies have demonstrated that CXCL10 has both cell wall/membrane and intracellular targets against this fungus. These findings present new possibilities for developing chemokine-derived small molecule antifungals and may represent a step forward in creating precision medicine tailored to each patient.

Immunotherapies against human bacterial and fungal infectious diseases: A review

Nations' ongoing struggles with a number of novel and reemerging infectious diseases, including the ongoing global health issue, the SARS-Co-V2 (severe acute respiratory syndrome coronavirus 2) outbreak, serve as proof that infectious diseases constitute a serious threat to the global public health. Moreover, the fatality rate in humans is rising as a result of the development of severe infectious diseases brought about by multiple drug-tolerant pathogenic microorganisms. The widespread use of traditional antimicrobial drugs, immunosuppressive medications, and other related factors led to the establishment of such drug resistant pathogenic microbial species. To overcome the difficulties commonly encountered by current infectious disease management and control processes, like inadequate effectiveness, toxicities, and the evolution of drug tolerance, new treatment solutions are required. Fortunately, immunotherapies already hold great potential for reducing these restrictions while simultaneously expanding the boundaries of healthcare and medicine, as shown by the latest discoveries and the success of drugs including monoclonal antibodies (MAbs), vaccinations, etc. Immunotherapies comprise methods for treating diseases that specifically target or affect the body's immune system and such immunological procedures/therapies strengthen the host's defenses to fight those infections. The immunotherapy-based treatments control the host's innate and adaptive immune responses, which are effective in treating different pathogenic microbial infections. As a result, diverse immunotherapeutic strategies are being researched more and more as alternative treatments for infectious diseases, leading to substantial improvements in our comprehension of the associations between pathogens and host immune system. In this review we will explore different immunotherapies and their usage for the assistance of a broad spectrum of infectious ailments caused by various human bacterial and fungal pathogenic microbes. We will discuss about the recent developments in the therapeutics against the growing human pathogenic microbial diseases and focus on the present and future of using immunotherapies to overcome these diseases. Graphical AbstractThe graphical abstract shows the therapeutic potential of different types of immunotherapies like vaccines, monoclonal antibodies-based therapies, etc., against different kinds of human Bacterial and Fungal microbial infections.

Mechanisms to reduce the cytotoxicity of pharmacological nicotinamide concentrations in the pathogenic fungus Candida albicans

Candida albicans is a pathogenic fungus that causes systemic infections and mortality in immunosuppressed individuals. We previously showed that deacetylation of histone H3 lysine 56 by Hst3 is essential for C. albicans viability. Hst3 is a fungal-specific NAD+ -dependent protein deacetylase of the sirtuin family. In vivo, supraphysiological concentrations of nicotinamide (NAM) are required for Hst3 inhibition and cytotoxicity. This underscores the importance of identifying mechanisms by which C. albicans can modulate intracellular NAM concentrations. For the first time in a pathogenic fungus, we combine genetics, heavy isotope labeling, and targeted quantitative metabolomics to identify genes, pathways, and mechanisms by which C. albicans can reduce the cytotoxicity of high NAM concentrations. We discovered three distinct fates for supraphysiological NAM concentrations. First, upon transient exposure to NAM, high intracellular NAM concentrations rapidly return near the physiological levels observed in cells that are not exposed to NAM. Second, during the first step of a fungal-specific NAM salvage pathway, NAM is converted into nicotinic acid, a metabolite that cannot inhibit the sirtuin Hst3. Third, we provide evidence that NAM enters the NAD+ metabolome through a NAM exchange reaction that contributes to NAM-mediated inhibition of sirtuins. However, in contrast to the other fates of NAM, the NAM exchange reaction cannot cause a net decrease in the intracellular concentration of NAM. Therefore, this reaction cannot enhance resistance to NAM. In summary, we demonstrate that C. albicans possesses at least two mechanisms to attenuate the cytotoxicity of pharmacological NAM concentrations. It seems likely that those two mechanisms of resistance to cytotoxic NAM concentrations are conserved in many other pathogenic fungi.

Dependence on Mincle and Dectin-2 Varies With Multiple Candida Species During Systemic Infection

More than 95% of invasive Candida infections are caused by four Candida spp. (C. albicans, C. glabrata, C. tropicalis, C. parapsilosis). C-type lectin-like receptors (CLRs), such as Dectin-1, Dectin-2, and Mincle mediate immune responses to C. albicans. Dectin-1 promotes clearance of C. albicans, C. glabrata, C. tropicalis, and C. parapsilosis, however, dependence on Dectin-1 for specific immune responses varies with the different Candida spp. Dectin-2 is important for host immunity to C. albicans and C. glabrata, and Mincle is important for the immune response to C. albicans. However, whether Dectin-2 drives host immunity to C. tropicalis or C. parapsilosis, and whether Mincle mediates host immunity to C. glabrata, C. tropicalis or C. parapsilosis is unknown. Therefore, we compared the roles of Dectin-2 and Mincle in response to these four Candida spp. We demonstrate that these four Candida spp. cell walls have differential mannan contents. Mincle and Dectin-2 play a key role in regulating cytokine production in response to these four Candida spp. and Dectin-2 is also important for clearance of all four Candida spp. during systemic infection. However, Mincle was only important for clearance of C. tropicalis during systemic infection. Our data indicate that multiple Candida spp. have different mannan contents, and dependence on the mannan-detecting CLRs, Mincle, and Dectin-2 varies between different Candida spp. during systemic infection.

IL-27 Negatively Controls Antifungal Activity in a Model of Invasive Pulmonary Aspergillosis

Invasive pulmonary aspergillosis is a life-threatening disease, particularly in immunocompromised patients, despite currently available therapy. IL-27 is an important regulatory cytokine in infection and immunity. However, its role in the pathogenesis of invasive pulmonary aspergillosis remains unknown. Here we found that Aspergillus fumigatus pulmonary infection induced an elevated production of IL-27 in the lung. As compared with wild-type (WT) mice, IL-27R (IL-27 receptor)-deficient mice developed less severe infection when challenged with A. fumigatus conidia, as evidenced by the decreased fungal colonization and pathology of lungs and the increased survival. IL-27R deficiency led to significantly higher production of IFN-γ in the lung after A. fumigatus infection, and the increased resistance to invasive pulmonary A. fumigatus infection in IL-27R-deficient mice was ablated by neutralizing IFN-γ. Importantly, neutralization of IL-27 could protect WT mice against invasive pulmonary A. fumigatus infection. Our data therefore suggest an important role of IL-27 in impairing anti-A. fumigatus host immunity, which may have translational implications in treating clinical cases of invasive pulmonary aspergillosis.

Immunomodulation for the Treatment of Fungal Infections: Opportunities and Challenges

Opportunistic fungal infections are major causes of morbidity and mortality in patients with single or multiple defects in their immunity. Antifungal agents targeting the pathogen remain the treatment of choice for fungal infections. However, antifungal agents are toxic to the host mainly due to the close evolutionary similarity of fungi and humans. Moreover, antifungal therapy is ineffective in patients with immunosuppression. For this reason, there is an increased demand to develop novel strategies to enhance immune function and augment the existing antifungal drugs. In recent times, targeting the immune system to improve impaired host immune responses becomes a reasonable approach to improve the effectiveness of antifungal drugs. In this regard, immunomodulating therapeutic agents that turn up the immune response in the fight against fungal infections hold promise for enhancing the efficacy and safety of conventional antifungal therapy. In general, immunomodulating therapies are safe with decreased risk of resistance and broad spectrum of activity. In this review, therefore, clinical evidences supporting the opportunities and challenges of immunomodulation therapies in the treatment of invasive fungal infections are included.

A Paradigm Shift in the Development of Anti-Candida Drugs

BACKGROUND

The considerable increase in the incidence of Candida infection in recent times has prompted the use of numerous antifungal agents, which has resulted in the development of resistance towards various antifungal agents. With rising Candida infections, the need for design and development of novel antifungal agents is in great demand. However, new therapeutic approaches are very essential in preventing the mortality rate and improving the patient outcome in those suffering from Candida infections.

OBJECTIVE

The present review objective is to describe the burden, types of Candidiasis, mechanism of action of antifungal agents and its resistance and the current novel approaches used to combat candidiasis.

METHODS

We have collected and analyzed 135 different peer-reviewed literature studies pertinent to candidiasis. In this review, we have compiled the major findings from these studies.

RESULTS AND CONCLUSION

The review describes the concerns related to candidiasis, its current treatment strategy, resistance mechanisms and imminent ways to tackle the problem. The review explored that natural plant extracts and essential oils could act as sources of newer therapeutic agents, however, the focus was on novel strategies, such as combinational therapy, new antibodies, utilization of photodynamic therapy and adaptive transfer primed immune cells with emphasis on the development of effective vaccination.

Impact of automatic infectious diseases consultation on the management of fungemia at a large academic medical center

PURPOSE

The impact of automatic infectious diseases (ID) consultation for inpatients with fungemia at a large academic medical center was studied.

METHODS

In this single-center, retrospective study, the time to appropriate antifungal therapy before and after implementing a policy requiring automatic ID consultation for the management of fungemia for all patients with an inpatient positive blood culture for fungus was examined. The rates of ID consultation; the likelihood of receiving appropriate antifungal therapy; central venous catheter (CVC) removal rates; performance of ophthalmologic examinations; infection-related length of stay (LOS); rates of all-cause inhospital mortality, death, or transfer to an intensive care unit within 7 days of first culture; and inpatient cost of antifungals were also evaluated.

RESULTS

A total of 173 unique episodes (94 and 79 in the control and intervention groups, respectively) were included. Candida species were the most frequently cultured organisms, isolated from over 90% of patients in both groups. No differences were observed between the control and intervention groups in time to appropriate therapy, infection-related LOS, or time to CVC removal. However, patients in the intervention group were more likely than those in the control group to receive appropriate antifungal therapy (p = 0.0392), undergo ophthalmologic examination (p = 0.003), have their CVC removed (p = 0.0038), and receive ID consultation (p = 0.0123). Inpatient antifungal costs were significantly higher in the intervention group (p = 0.0177).

CONCLUSION

While automatic ID consultation for inpatients with fungemia did not affect the time to administration of appropriate therapy, improvement was observed for several process indicators, including rates of appropriate antifungal therapy selection, time to removal of CVCs, and performance of ophthalmologic examinations.

Candida spp. and phagocytosis: multiple evasion mechanisms

Invasive fungal infections are a global health problem, mainly in hospitals, where year by year hundreds of patients die because of these infections. Commensal yeasts may become pathogenic to human beings, affecting mainly immunocompromised patients. During infectious processes, the immune system uses phagocytes to eliminate invader microorganisms. In order to prevent or neutralize phagocyte attacks, pathogenic yeasts can use virulence factors to survive, as well as to colonize and infect the host. In this review, we describe how Candida spp., mainly Candida albicans, interact with phagocytes and use several factors that contribute to immune evasion. Polymorphism, biofilm formation, gene expression and enzyme production mediate distinct functions such as adhesion, invasion, oxidative stress response, proteolysis and escape from phagocytes. Fungal and human cells have similar structures and mechanisms that decrease the number of potential targets for antifungal drugs. Therefore, research on host-pathogen interaction may aid in the discovery of new targets and in the development of new drugs or treatments for these diseases and thus to save lives.

Microrna Expression Profiling of Macrophage Line Raw264.7 Infected by Candida Albicans

INTRODUCTION

The aim of this study was to clarify the microRNA (miRNA) expression profiles of RAW264.7 macrophages infected by Candida albicans to elucidate the roles of differentially expressed miRNAs and to further explore the mechanisms underlying the immune response to C. albicans infection.

METHODS

High-throughput miRNA microarray analysis was performed to detect differentially expressed miRNAs in control and C. albicans-infected RAW264.7 cells. Quantitative real-time PCR analysis was used to verify the microarray results. Target genes of differentially expressed miRNAs were predicted with bioinformatics software. The cell biological processes and signaling pathways of these miRNA-targeted genes involved in C. albicans infection were predicted by gene ontology (GO) enrichment and pathway analyses.

RESULTS

Significant upregulation of eight miRNAs (mmu-miR-140-5p, mmu-miR-96-5p, mmu-miR-8109, mmu-miR-466i-3p, mmu-miR-222-5p, mmu-miR-301b-3p, mmu-miR-466g, and mmu-miR-7235-5p) and downregulation of eight miRNAs (mmu-miR-3154, mmu-miR-223-3p, mmu-miR-494-3p, mmu-miR-6908-5p, mmu-miR-188-5p, mmu-miR-6769b-5p, mmu-miR-7002-5p, and mmu-miR-1224-5p) were observed, as compared with the control (fold change ≥2.0 and P < 0.05). GO analysis revealed that both mmu-miR-140-5p and mmu-miR-223-3p participated in immune responses, inflammatory reactions, and cell apoptosis in C. albicans infection. Also, the MAPK signaling pathway was found to play an important role in the immune response against C. albicans infection.

CONCLUSIONS

This study revealed comprehensive expression and functional profiles of differentially expressed miRNAs in macrophage RAW264.7 cells infected by C. albicans. These findings should help to further elucidate the mechanisms underlying the immune response to C. albicans infection.

Fungal melanin stimulates surfactant protein D-mediated opsonization of and host immune response to Aspergillus fumigatus spores

Surfactant protein D (SP-D), a C-type lectin and pattern-recognition soluble factor, plays an important role in immune surveillance to detect and eliminate human pulmonary pathogens. SP-D has been shown to protect against infections with the most ubiquitous airborne fungal pathogen, Aspergillus fumigatus, but the fungal surface component(s) interacting with SP-D is unknown. Here, we show that SP-D binds to melanin pigment on the surface of A. fumigatus dormant spores (conidia). SP-D also exhibited an affinity to two cell-wall polysaccharides of A. fumigatus, galactomannan (GM) and galactosaminogalactan (GAG). The immunolabeling pattern of SP-D was punctate on the conidial surface and was uniform on germinating conidia, in accordance with the localization of melanin, GM, and GAG. We also found that the collagen-like domain of SP-D is involved in its interaction with melanin, whereas its carbohydrate-recognition domain recognized GM and GAG. Unlike un-opsonized conidia, SP-D-opsonized conidia were phagocytosed more efficiently and stimulated the secretion of proinflammatory cytokines by human monocyte-derived macrophages. Furthermore, SP-D^-/- mice challenged intranasally with wildtype conidia or melanin ghosts (i.e. hollow melanin spheres) displayed significantly reduced proinflammatory cytokines in the lung compared with wildtype mice. In summary, SP-D binds to melanin present on the dormant A. fumigatus conidial surface, facilitates conidial phagocytosis, and stimulates the host immune response.

Dynamic Immune Cell Recruitment After Murine Pulmonary Aspergillus fumigatus Infection under Different Immunosuppressive Regimens

Humans are continuously exposed to airborne spores of the saprophytic fungus Aspergillus fumigatus. However, in healthy individuals pulmonary host defense mechanisms efficiently eliminate the fungus. In contrast, A. fumigatus causes devastating infections in immunocompromised patients. Host immune responses against A. fumigatus lung infections in immunocompromised conditions have remained largely elusive. Given the dynamic changes in immune cell subsets within tissues upon immunosuppressive therapy, we dissected the spatiotemporal pulmonary immune response after A. fumigatus infection to reveal basic immunological events that fail to effectively control invasive fungal disease. In different immunocompromised murine models, myeloid, notably neutrophils, and macrophages, but not lymphoid cells were strongly recruited to the lungs upon infection. Other myeloid cells, particularly dendritic cells and monocytes, were only recruited to lungs of corticosteroid treated mice, which developed a strong pulmonary inflammation after infection. Lymphoid cells, particularly CD4⁺ or CD8⁺ T-cells and NK cells were highly reduced upon immunosuppression and not recruited after A. fumigatus infection. Moreover, adoptive CD11b⁺ myeloid cell transfer rescued cyclophosphamide immunosuppressed mice from lethal A. fumigatus infection but not cortisone and cyclophosphamide immunosuppressed mice. Our findings illustrate that CD11b⁺ myeloid cells are critical for anti-A. fumigatus defense under cyclophosphamide immunosuppressed conditions.

Evaluation of APR1 Gene Expression in Candida albicans Strains Isolated From Patients With Multiple Sclerosis

BACKGROUND

Intracellular aspartic proteinase A enzyme is expressed by the APR1 gene and is one of the important factors in the development of systemic candidiasis caused by Candida albicans.

OBJECTIVES

The aim of this study was to evaluate the expression of the APR1 gene in C. albicans isolates obtained from patients with multiple sclerosis (MS) and from controls.

PATIENTS AND METHODS

The samples were obtained from 135 MS patients with candidiasis and 100 matched controls of healthy individuals during 2010 - 2011. The clinical and control isolates of C. albicans obtained from individuals were cultured onto sabouraud dextrose agar (SDA). The evaluation of APR1 gene expression was performed using the reverse transcriptase-polymerase chain reaction (RT-PCR) method.

RESULTS

There was a statistically significant difference in APR1 gene expression of C. albicans strains between MS patients (mean ± SD: 0.5208 ± 0.11518) and the control group (mean ± SD: 0.7603 ± 0.11405) (P = 0.000). Significant correlations were found between the APR1 gene expression of C. albicans strains from MS patients with regard to age and the expanded disability status scale (EDSS) (P = 0.000). The mean values of EDSS were 1.6074 ± 0.1081 after antifungal treatment and 2.2519 ± 0.1323 before antifungal treatment (P = 0.000). No significant correlation was observed between the APR1 gene expression with regard to sex and MS subtypes.

CONCLUSIONS

The results suggested that APR1 gene expression in C. albicans strains isolated from MS patients may be an important factor for invasive C. albicans strains in the progression of MS disease.

[Immunopathogenesis of invasive mould infections]

Invasive fungal infections caused by filamentous fungi are devastating diseases that occur in patients with a variety of immunosuppressive conditions. This review focuses on the pathogenesis of the most important invasive mycosis in the human being caused by the filamentous fungi Aspergillus, Fusarium, Scedosporium and mucorales. The first contact between the mould and the patient, the host defense to different fungi, including the role of mucosa in the innate immune system, the whole innate immune recognition receptors, and the pathways connecting innate and adaptive immunity, as well as the virulence factors of fungi, are discussed in this paper.

Myeloid derived hypoxia inducible factor 1-alpha is required for protection against pulmonary Aspergillus fumigatus infection

Hypoxia inducible factor 1α (HIF1α) is the mammalian transcriptional factor that controls metabolism, survival, and innate immunity in response to inflammation and low oxygen. Previous work established that generation of hypoxic microenvironments occurs within the lung during infection with the human fungal pathogen Aspergillus fumigatus. Here we demonstrate that A. fumigatus stabilizes HIF1α protein early after pulmonary challenge that is inhibited by treatment of mice with the steroid triamcinolone. Utilizing myeloid deficient HIF1α mice, we observed that HIF1α is required for survival and fungal clearance early following pulmonary challenge with A. fumigatus. Unlike previously reported research with bacterial pathogens, HIF1α deficient neutrophils and macrophages were surprisingly not defective in fungal conidial killing. The increase in susceptibility of the myeloid deficient HIF1α mice to A. fumigatus was in part due to decreased early production of the chemokine CXCL1 (KC) and increased neutrophil apoptosis at the site of infection, resulting in decreased neutrophil numbers in the lung. Addition of recombinant CXCL1 restored neutrophil survival and numbers, murine survival, and fungal clearance. These results suggest that there are unique HIF1α mediated mechanisms employed by the host for protection and defense against fungal pathogen growth and invasion in the lung. Additionally, this work supports the strategy of exploring HIF1α as a therapeutic target in specific immunosuppressed populations with fungal infections.

Persistent Cryptococcal Brain Infection despite Prolonged Immunorecovery in an HIV-Positive Patient

Background. HIV-positive people starting combined antiretroviral therapy may develop immune reconstitution to latent or treated opportunistic infections. Immune reconstitution to cerebral Cryptococcus is poorly understood and can be fatal. Case Presentation. A 33-year-old Zimbabwean female presented with cryptococcal meningitis and newly diagnosed HIV with a CD4 count of 51 cells/μL (4%). She was treated with amphotericin and flucytosine. Combined antiretroviral therapy was started four weeks later and she showed early improvement. However, over the ensuing 18 months, her clinical course was marked by periodic worsening with symptoms resembling cryptococcal meningitis despite having achieved CD4 counts ≥400 cells/μL. Although initially treated for relapsing cryptococcal immune reconstitution syndrome, a brain biopsy taken 17 months after initial presentation showed budding Cryptococci. Conclusion. This unusually protracted case highlights the difficulties in differentiating relapsing cryptococcal meningitis from immune reconstitution and raises questions concerning the optimum timing of initiation of combined antiretroviral therapy in such patients.

Immunomodulatory therapy in yeast infections

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

Epidemiology and echinocandin susceptibility of Candida parapsilosis sensu lato species isolated from bloodstream infections at a Spanish university hospital

OBJECTIVES

The aims of this work were to study the epidemiological profiles, differences in echinocandin susceptibilities and clinical relevance of the Candida parapsilosis sensu lato species isolated from proven fungaemia cases at La Fe University Hospital of Valencia (Spain) from 1995 to 2007.

RESULTS

The prevalence of these species was: C. parapsilosis sensu stricto, 74.4%; Candida orthopsilosis, 23.54%; and Candida metapsilosis, 2.05%. The incidence of the species complex as agents of fungaemia remained stationary until 2005 and doubled in 2006. The incidence of C. orthopsilosis showed an increasing trend during the study period, while C. parapsilosis sensu stricto incidence diminished. Also, an important epidemiological change was observed starting in 2004, when 86.5% of the C. parapsilosis sensu lato strains were found in adult patients, while before that year only 13.5% of the isolates were found in this population.

CONCLUSIONS

Echinocandin drug susceptibility testing using the CLSI M27-A3 document showed a wide range of MIC values (0.015-4 mg/L), with micafungin being the most potent in vitro inhibitor followed by anidulafungin and caspofungin (MIC geometric mean of 0.68, 0.74 and 0.87 mg/L, respectively). C. metapsilosis was the most susceptible species of the complex to anidulafungin and micafungin in vitro (MIC(50) for anidulafungin and micafungin: 0.06 mg/L), while there were no differences between C. parapsilosis sensu lato species when caspofungin MIC(50)s were compared (MIC(50) 1.00 mg/L). Differences in caspofungin in vitro susceptibility were observed between the different clinical service departments of La Fe Hospital.

Phagocytic receptors on macrophages distinguish between different Sporothrix schenckii morphotypes

Sporothrix schenckii is a human pathogen that causes sporotrichosis, a cutaneous subacute or chronic mycosis. Little is known about the innate immune response and the receptors involved in host recognition and phagocytosis of S. schenckii. Here, we demonstrate that optimal phagocytosis of conidia and yeast is dependent on preimmune human serum opsonisation. THP-1 macrophages efficiently ingested opsonised conidia. Competition with D-mannose, methyl α-D-mannopyranoside, D-fucose, and N-acetyl glucosamine blocked this process, suggesting the involvement of the mannose receptor in binding and phagocytosis of opsonised conidia. Release of TNF-α was not stimulated by opsonised or non-opsonised conidia, although reactive oxygen species (ROS) were produced, resulting in the killing of conidia by THP-1 macrophages. Heat inactivation of the serum did not affect conidia internalization, which was markedly decreased for yeast cells, suggesting the role of complement components in yeast uptake. Conversely, release of TNF-α and production of ROS were induced by opsonised and non-opsonised yeast. These data demonstrate that THP-1 macrophages respond to opsonised conidia and yeast through different phagocytic receptors, inducing a differential cellular response. Conidia induces a poor pro-inflammatory response and lower rate of ROS-induced cell death, thereby enhancing the pathogen's survival.

Doxorubicin selects for fluconazole-resistant petite mutants in Candida glabrata isolates

Candida infections are a permanent threat to immunocompromised individuals such as cancer patients, and Candida glabrata has emerged as a major problem in recent years. Resistance may develop during lengthy antifungal therapies and is often mediated by upregulation of fungal drug efflux pumps. During chemotherapy the yeast cell is also exposed to cytotoxic agents that may affect its drug susceptibility. Four C. glabrata isolates, three susceptible and one resistant to fluconazole (FLU), were incubated with 20 μg/ml of doxorubicin (DOX) for 90 min. In a second experiment, the isolates were cultured with DOX for ten days. Samples were taken on subsequent days to determine the minimal inhibitory concentration (MIC) of FLU and to analyze expression of CgCDR1, CgCDR2, CgSNQ2 and CgPDR1. Samples were also used to assess the petite phenotype. Short-term DOX exposure did not induce efflux pump gene expression, but genes were consistently overexpressed in FLU-susceptible isolates during long-term exposure. An increase in MIC values on day 6 in two of the isolates coincided with the first occurrence of petite mutants in all susceptible isolates. The respiratory deficiency of selected petite mutants was confirmed by culturing mutants on agar containing glycerol as the sole carbon source. FLU MIC values for respiratory-deficient clones were ≥64 μg/ml, and efflux pump gene expression was greatly increased. The resistant isolate did not develop mitochondrial dysfunction. In summary, the cytotoxic agent DOX selects for FLU-resistant respiratory-deficient C. glabrata mutants, which may affect antifungal therapy.

Immunotherapies in infectious diseases

The development of an infection involves interplay between the host's immune system and the virulence of the infecting microorganism. The traditional treatment of an infection involves antimicrobial chemotherapy to kill the organism. The use of immunotherapies in infections includes treatment options that modulate the immune response and can lead to control of infections. These therapies are expected to become more important therapeutic options with the increase in infections due to multidrug-resistant organisms and the increasing number of immunocompromised patients.

Role of endogenous biological response modifiers in pathogenesis of infectious diseases

Biologic response modifiers (BRMs) interact with the host immune system and modify the immune response. BRMs can be therapeutically used to restore, augment, or dampen the host immune response. Although they have been used for decades, their clinical applications have been expanded in the past decade for diagnosis and treatment of many diseases including cancers, immunologic disorders, and infections. This article discusses endogenous biological response modifiers (ie, naturally occurring immunomodulators as a part of the host immune system), which play vital roles as regulators of both innate and adaptive immune responses.

The impact of the host on fungal infections

Outcomes of fungal infections in immunocompromised individuals depend on a complex interplay between host and pathogen factors, as well as treatment modalities. Problems occur when host responses to an infection are either too weak to effectively help eradicate the pathogen, or when they become too strong and are associated with host damage rather than protection. Immune reconstitution syndrome (IRS) can be generally defined as a restoration of host immunity in a previously immunosuppressed patient that becomes dysregulated and overly robust, resulting in host damage and sometimes death. IRS associated with opportunistic mycoses presents as new or worsening clinical symptoms or radiographic signs consistent with an inflammatory process that occur during receipt of an appropriate antifungal, and that cannot be explained by a newly acquired infection. Because there are currently no established tests or biomarkers for IRS, it can be difficult to distinguish from progression of the original infection, although culture and biomarkers for the fungal pathogen or infection are typically negative during diagnostic workup. IRS was originally characterized in human immunodeficiency virus-infected patients receiving antiretroviral therapy, but has subsequently been described in solid-organ transplant recipients, neutropenic patients, women in the postpartum period, and recipients of tumor necrosis factor-α inhibitor therapy. In each of these cases, recovery of the host's immunity during treatment of an initial infection results in a powerful proinflammatory environment that overshoots and leads to host damage. Optimal management of IRS has not been established at present, but often involves treatment with a corticosteroid or other anti-inflammatory compounds. This article uses a number of patient cases to explore the intricacies of diagnosing and managing a patient with IRS, as well as the other extreme, namely patients who are so immunocompromised without immune recovery that they essentially become breeding grounds for a wide range of opportunistic pathogens, often simultaneously.

Immunotherapy of aspergillosis

Management of invasive aspergillosis in high-risk patients remains challenging. There is an increasing demand for novel therapeutic strategies aimed at enhancing or restoring antifungal immunity in immunocompromised patients. In this regard, modulation of specific innate immune functions and vaccination are promising immunotherapeutic strategies. Recent findings have also provided a compelling rationale for assessment of the contribution of the individual genetic profile to the immunotherapy outcome. Altogether, integration of immunological and genetic data may contribute to the optimization of therapeutic strategies exerting control over immune pathways, ultimately improving the management of fungal infections in high-risk settings.

Serum amyloid a protein in clinical cancer diagnosis

The serum amyloid A (SAA) protein is an acute phase protein that is synthesized under the regulation of inflammatory cytokines during both acute and chronic inflammation. It is suggested that the SAA increases correlate with many types of carcinogenesis and neoplastic diseases. Th changes in SAA in serum could therefore indicate the progress and malignancy of the disease, as well as the host responses. The present paper reviewed the rationale of using SAA as potential cancer biomarker in clinical diagnosis, including the contribution and involvement of SAA in cancer growth and development. Then we discussed the current applications of SAA in diagnosis and tracing of different types of cancers. Finally the proteomics techniques, especially the SELDI-TOF MS to identify SAA in serum from patients were appreciated as an important manner in clinical diagnosis.

Human NK cells display important antifungal activity against Aspergillus fumigatus, which is directly mediated by IFN-γ release

Despite the strong interest in the NK cell-mediated immunity toward malignant cells and viruses, there is a relative lack of data on the interplay between NK cells and filamentous fungi, especially Aspergillus fumigatus, which is the major cause of invasive aspergillosis. By studying the in vitro interaction between human NK cells and A. fumigatus, we found only germinated morphologies to be highly immunogenic, able to induce a Th1-like response, and capable of upregulating cytokines such as IFN-γ and TNF-α. Moreover, priming NK cells with human rIL-2 and stimulating NK cells by direct NK cell-pathogen contact were essential to induce damage against A. fumigatus. However, the most interesting finding was that NK cells did not mediate anti-Aspergillus cytotoxicity through degranulation of their cytotoxic proteins (perforin, granzymes, granulysine), but via an alternative mechanism involving soluble factor(s). To our knowledge, our study is the first to demonstrate that IFN-γ, released by NK cells, directly damages A. fumigatus, attributing new properties to both human NK cells and IFN-γ and suggesting them as possible therapeutic tools against IA.

Epidemiology and treatment approaches in management of invasive fungal infections

Over the past 20 years, the number of invasive fungal infections has continued to persist, due primarily to the increased numbers of patients subjected to severe immunosuppression. Despite the development of more active, less toxic antifungal agents and the standard use of antifungal prophylaxis, invasive fungal infections (especially invasive mold infections) continue to be a significant factor in hematopoietic cell and solid organ transplantation outcomes, resulting in high mortality rates. Since the use of fluconazole as standard prophylaxis in the hematopoietic cell transplantation setting, invasive candidiasis has come under control, but no mold-active antifungal agent (except for posaconazole in the setting of acute myelogenous leukemia and myelodysplastic syndrome) has been shown to improve the survival rate over fluconazole. With the advent of new azole and echinocandin agents, we have seen the emergence of more azole-resistant and echinocandin-resistant fungi. The recent increase in zygomycosis seen in the hematopoietic cell transplantation setting may be due to the increased use of voriconazole. This has implications for the empiric approach to pulmonary invasive mold infections when zygomycosis cannot be ruled out. It is imperative that an amphotericin B product, an antifungal that has never developed resistance in over 50 years, be initiated. The clinical presentations of invasive mold infections and invasive candidiasis can be nonspecific and the diagnostic tests insensitive, so a high index of suspicion and immediate initiation of empiric therapy is required. Unfortunately, our currently available serologic tests do not predict infection ahead of disease, and, therefore cannot be used to initiate “preemptive” therapy. Also, the Aspergillus galactomannan test gives a false negative result in patients receiving antimold prophylaxis, ie, virtually all of our patients with hematologic malignancy and hematopoietic cell transplant recipients. We may eventually be able to select patients at highest risk for invasive fungal infections for prophylaxis by genetic testing. However, with our current armamentarium of antifungal agents and widespread use of prophylaxis in high-risk groups (hematologic malignancy, hematopoietic cell transplantation), we continue to see high incidence and mortality rates, and our future hope lies in reversing the immunosuppression or augmenting the immune system of these severely immunocompromised hosts by developing and utilizing immunotherapy, immunoprophylaxis, and vaccines.

Antifungal prophylaxis and therapy in patients with hematological malignancies and hematopoietic stem cell transplant recipients

Patients with acute leukemia and hematopoietic stem cell transplant recipients are at risk of a spectrum of invasive fungal diseases corresponding to the type and intensity of immunosuppression. The development of newer antifungal agents has broadened therapeutic options. In the 1990s, lipid formulations of amphotericin B became widely used as safer alternatives to amphotericin B deoxycholate. In addition, fluconazole was shown to be beneficial as a yeast-active prophylaxis in hematopoietic stem cell transplant recipients. In the past decade, the antifungal armamentarium was further enhanced with the availability of extended-spectrum azoles and echinocandins. The development of effective broad-spectrum antifungal agents has led to their use as prophylaxis rather than delaying treatment until clinical signs of infection manifest. Antigen-based and PCR-based diagnostic adjuncts facilitate earlier detection of invasive fungal diseases compared with conventional culture, and have been incorporated into strategies in which initiation or modification of an antifungal regimen is targeted to patients with the highest likelihood of having fungal disease. Here, we review the pharmacological data and major clinical trials that guide the use of antifungals, as well as areas of uncertainty and future perspectives.

Nosocomial fungal infections: epidemiology, infection control, and prevention

Fungal infections are an increasing cause of morbidity and mortality in hospitalized patients. This article reviews the current epidemiology of nosocomial fungal infections in adult patients, with an emphasis on invasive candidiasis and aspergillosis. Recently published recommendations and guidelines for the control and prevention of these nosocomial fungal infections are summarized.

[Spanish Paediatric Infectious Diseases Society consensus document on the treatment of fungal infections based on the immune response]

Despite the emergence of new diagnostic and therapeutic methods, invasive fungal infections are still a major cause of morbidity and mortality in immunocompromised and critical patients. Therefore, adjuvant treatments to the standard antifungal therapy are being investigated, with immunity-based therapy being one of the most important. Both immunomodulatory (dendritic and T cells transfusions, colony stimulating factors, interferón-gamma, interleukin 12, fungal vaccines, transfer factors and certain drugs such as chloroquine) and immunotherapeutic modalities (granulocyte transfusions, monoclonal antibodies and intravenous immunoglobulin) have been described. This document aims to summarise currently available data on immunity-based therapy of fungal infections and to provide basic knowledge on the immune response to fungal infections. This helps to understand how, in selected cases, immunity-based therapy may improve the response to standard antifungal treatment. The potential indications of immunity-based therapy in the paediatric patient are reviewed, although there is still a lack of scientific evidence for its use in children.

Aspergillosis in hematopoietic stem cell transplant recipients: risk factors, prophylaxis, and treatment

This article discusses newer antifungal agents, recent randomized controlled trials, and the 2008 guidelines for treatment of aspergillosis in reference to hematopoietic stem cell transplantation (HSCT). Strategies such as reduced-intensity conditioning and agents such as infliximab shed new light on aspergillosis risk. The association between Toll-like receptor polymorphisms and aspergillosis is an exciting development. Posaconazole was evaluated in two randomized prophylaxis trials, and a large, randomized trial established voriconazole's therapeutic superiority to amphotericin. However, many questions remain regarding which patients benefit most from prophylaxis; resistance to newer antifungals; and combination, salvage, and immunomodulatory therapies. Current therapies and strategies have improved the outlook of HSCT recipients with invasive aspergillosis. Future directions include increasingly sophisticated risk stratification, clinical testing of combination therapies, and adjunctive immunomodulatory therapies.

Epidemiology, incidence and risk factors for invasive candidiasis in high-risk patients

Candida spp. are an increasing cause of bloodstream infections, and are associated with high morbidity and mortality in both neutropenic and non-neutropenic critically ill patients. Risk factors associated with candidaemia are diverse and include exposure to broad spectrum antimicrobial agents, mucosal colonization by Candida spp., indwelling vascular catheters, prior surgery and cancer chemotherapy. During the last 20 years, there has been an increasing incidence worldwide in invasive candidiasis, but differences in geographical epidemiology are emerging, in particular regarding a shift towards non-albicans species. This shift has been correlated with routine fluconazole prophylaxis adopted in some patients, and the intrinsic/acquired azole resistance of Candida spp., which represents a very real problem, in terms of both selecting the appropriate empirical therapeutic approach and making prophylactic choices.

Minireview: Invasive fungal infection complicating acute Plasmodium falciparum malaria

Malaria is the most important parasitic infection in people, affecting 5-10% of the world's population with more than two million deaths a year. Whereas invasive bacterial infections are not uncommon during severe Plasmodium falciparum malaria, only a few cases of opportunistic fungal infections have been reported. Here, we present a fatal case of disseminated hyalohyphomycosis associated with acute P. falciparum malaria in a non-immune traveller, review the cases reported in the literature and discuss the theoretical foundations for the increased susceptibility of non-immune individuals with severe P. falciparum malaria to opportunistic fungal infections. Apart from the availability of free iron as sequelae of massive haemolysis, tissue damage, acidosis and measures of advanced life support, patients with complicated P. falciparum malaria also are profoundly immunosuppressed by the organism's interaction with innate and adaptive host immune mechanisms.

Activation of foal neutrophils at different ages by CpG oligodeoxynucleotides and Rhodococcus equi

Toll-like receptor 9 (TLR9) activation stimulates protective immune responses against intracellular pathogens by phagocytes, including neutrophils. This study examined TLR9-mediated neutrophil activation in neonatal foals. Unmethylated CpGs, ligands for TLR9, were used to stimulate equine neutrophils, either purified or in contact with other peripheral blood leukocytes. Rhodococcus equi was used as another stimulus in parallel. TLR9 mRNA was constitutively expressed at a similar level in purified equine neutrophils across different ages from birth to adulthood, and expression was not affected by either CpG or R. equi. Purified foal neutrophils were directly sensitive to CpG stimulation, reflected by enhanced reactive oxygen species generation following fMLP stimulation, and by expressing significantly (P<0.05) greater mRNA of IFN-gamma, IL-8, IL-12p35, and significantly (P<0.05) decreased TNF-alpha mRNA. In comparison, purified foal neutrophils stimulated by R. equi showed significantly (P<0.05) increased mRNA production of IL-6, IL-8, IL-23p19, and TNF-alpha. Neutrophils co-cultured with other leukocytes expressed a distinct profile of cytokine mRNA than purified neutrophils in response to CpG stimulation, whereas the profile was very similar following R. equi stimulation irrespective of neutrophil purity. When co-cultured with other leukocytes, foal neutrophils were significantly (P<0.05) activated at birth by B-class CpGs and produced IL-6, IL-8, IL-12p40, and IL-23p19 at similar magnitudes to those at 2 months of age. In foal neutrophils at birth, R. equi significantly (P<0.05) induced all cytokines stimulated by CpGs (except IL-12p40), as well as TNF-alpha. Our results indicate that foal neutrophils were sensitive to CpG or R. equi activation as early as at birth, and that B-class CpGs enhanced foal neutrophil functions in vitro.

Exogenous pentraxin 3 restores antifungal resistance and restrains inflammation in murine chronic granulomatous disease

Chronic granulomatous disease (CGD) is a primary immunodeficiency characterized by life-threatening bacterial and fungal infections and hyperinflammation. The susceptibility to aspergillosis in experimental CGD (p47(phox-/-) mice) is associated with the failure to control the inherent inflammatory response to the fungus and to restrict the activation of inflammatory Th17 cells. We assessed whether pentraxin (PTX)3, a member of a family of multimeric pattern-recognition proteins with potent anti-Aspergillus activity, could limit pathogenic inflammation in p47(phox-/-) mice by curbing the IL-23/Th17 inflammatory axis in response to the fungus. We found that the production of PTX3 was delayed in CGD mice in infection but exogenous administration of PTX3 early in infection restored antifungal resistance and restrained the inflammatory response to the fungus. This occurred through down-regulation of IL-23 production by dendritic cells and epithelial cells which resulted in limited expansion of IL-23R+ gammadelta+ T cells producing IL-17A and the emergence of Th1/Treg responses with minimum pathology. Thus, PTX3 could be therapeutically used for the exploitation of NADPH-independent mechanism(s) of antifungal immune protection with limited immunopathology in CGD.

Recent advances in antifungal prevention and treatment

Invasive fungal infections are important causes of morbidity and mortality in patients with bone marrow failure syndromes and hematological malignancies, or who are undergoing allogeneic hematopoietic stem cell transplantation (HSCT). Current epidemiological trends indicate a shift toward infections by Aspergillus spp., non-albicans Candida spp., and previously uncommon fungal pathogens that have decreased susceptibility to the available antifungal agents. The last two decades have seen substantial improvements in the clinical, laboratory, and radiological diagnosis of these infections and the development of new antifungal compounds. Progress has been made in establishing disease definitions and paradigms for antifungal intervention and in the design and conduct of interventional clinical trials. Collectively, these advances have led to major but ongoing changes in the management of patients at risk of or being affected by invasive fungal infections. This article reviews current approaches to prevention and treatment of opportunistic fungal infections in immunocompromised patients with hematological disorders and discusses novel approaches to antifungal chemotherapy and adjunctive treatments.