Long-term follow up of invasive aspergillosis in allogeneic stem cell transplantation recipients and leukemia patients: Differences in risk factors and outcomes

Routine Surveillance of Healthcare-Associated Infections Misses a Significant Proportion of Invasive Aspergillosis in Patients with Severe COVID-19

Rates of invasive aspergillosis (IA) among COVID-19 ICU patients seem to reach over 30% in certain settings. At Vienna General Hospital (VGH), all rooms in COVID-19 ICUs were put under negative pressure as a protective measure, thus increasing the risk of exposure to environmental pathogens for patients. Even though all ICU patients are surveilled for healthcare-associated infections (HAI), there were concerns that the routine protocol might not be sufficient for IA detection. We reviewed the electronic patient charts of all patients with COVID-19 admitted to ICUs between 1 March 2020 and 31 July 2021 for fungal co- or superinfections, comparing four diagnostic algorithms based on different recommendations for the diagnosis of IA (according to EORTC/MSG, BM-AspICU, IAPA and CAPA) to our routine surveillance protocol. We found that out of 252 patients who were admitted to the ICU during the study period, 25 (9.9%) fulfilled the criteria of probable or possible IA of at least one algorithm. The IAPA definitions detected 25 and the CAPA definition 23 probable and 2 possible cases, out of which only 16 were classified as hospital-acquired IA by routine surveillance. In conclusion, adjustment of the routine protocol using a classification system especially designed for respiratory viral illness seems useful for the surveillance of IA in a highly vulnerable patient cohort.

The Pathogenesis of Aspergillus fumigatus, Host Defense Mechanisms, and the Development of AFMP4 Antigen as a Vaccine

Aspergillus fumigatus is one of the ubiquitous fungi with airborne conidia, which accounts for most aspergillosis cases. In immunocompetent hosts, the inhaled conidia are rapidly eliminated. However, immunocompromised or immunodeficient hosts are particularly vulnerable to most Aspergillus infections and invasive aspergillosis (IA), with mortality from 50% to 95%. Despite the improvement of antifungal drugs over the last few decades, the therapeutic effect for IA patients is still limited and does not provide significant survival benefits. The drawbacks of antifungal drugs such as side effects, antifungal drug resistance, and the high cost of antifungal drugs highlight the importance of finding novel therapeutic and preventive approaches to fight against IA. In this article, we systemically addressed the pathogenic mechanisms, defense mechanisms against A. fumigatus, the immune response, molecular aspects of host evasion, and vaccines' current development against aspergillosis, particularly those based on AFMP4 protein, which might be a promising antigen for the development of anti-A. fumigatus vaccines.

Data of common and species-specific transcriptional host responses to pathogenic fungi

Using a comparative RNA-Sequencing based transcriptional profiling approach, responses of primary human peripheral blood mononuclear cells (PBMCs) to common human pathogenic fungi have been characterized (Bruno et al. Computational and Structural Biology Journal). Primary human PBMCs were stimulated in vitro with the fungi A. fumigatus, C. albicans, and R. oryzae after which RNA was isolated and sequenced. From raw sequencing reads differential expressed genes in response to the different fungi where calculated by comparison with unstimulated cells. By overlapping differentially expressed genes in response to the pathogenic fungi A. fumigatus, C. albicans, and R. oryzae a dataset was generated that encompasses a common response to these three distinct fungi as well as species-specific responses. Here we present datasets on these common and species-specific responses that complement the original study (Bruno et al. Computational and Structural Biology Journal). These data serve to facilitate further fundamental research on the immune response to opportunistic pathogenic fungi such as A. fumigatus, C. albicans, and R. oryzae.

Comparative host transcriptome in response to pathogenic fungi identifies common and species-specific transcriptional antifungal host response pathways

Candidiasis, aspergillosis, and mucormycosis cause the majority of nosocomial fungal infections in immunocompromised patients. Using an unbiased transcriptional profiling in PBMCs exposed to the fungal species causing these infections, we found a core host response in healthy individuals that may govern effective fungal clearance: it consists of 156 transcripts, involving canonical and non-canonical immune pathways. Systematic investigation of key steps in antifungal host defense revealed fungal-specific signatures. As previously demonstrated, Candida albicans induced type I and Type II interferon-related pathways. In contrast, central pattern recognition receptor, reactive oxygen species production, and host glycolytic pathways were down-regulated in response to Rhizopus oryzae, which was associated with an ER-stress response. TLR5 was identified to be uniquely regulated by Aspergillus fumigatus and to control cytokine release in response to this fungus. In conclusion, our data reveals the transcriptional profiles induced by C. albicans, A. fumigatus, and R. oryzae, and describes both the common and specific antifungal host responses that could be exploited for novel therapeutic strategies.

Baseline predictors influencing the prognosis of invasive aspergillosis in adults

Invasive aspergillosis (IA) is a serious hazard to haematological and critical care patients. Impactful risk factors for developing IA have been characterised; however, systematic analysis of baseline prognostic factors for treatment course of IA is missing. To understand prognostic variables, we analysed original articles identifying baseline factors that predict treatment outcome in patients with IA. PubMed database was searched for publications since database inception until May 2018. Inclusion criteria were published baseline prognostic factors present at the diagnosis of IA. In total, 58 studies from 267 centres reported 7320 patients with IA and 40 different predictors. Unfavourable predictors in medical history were kidney (7.4%, 10/136) and liver failure (3.7%, 5/136), ICU admission (3.7%, 5/136) and uncontrolled underlying disease (3.7%, 5/136). Regarding state of immunosuppression, negative outcome predictors were prolonged neutropenia (12.5%, 17/136), corticosteroid treatment (8.1%, 11/136) and graft-vs-host disease (3.7%, 5/136). On the pathogen side, relevant predictors were galactomannan positivity (8.1%, 11/136), Aspergillus terreus infection (2.2%, 3/136) and lack of amphotericin B susceptibility (1.5%, 2/136). IA-specific predictors were disseminated disease (5.1%, 7/136) and CNS involvement (2.9%, 4/136). Imaging results associated with negative outcome were multiple consolidations (2.9%, 4/136), bipulmonary lesions (2.2%, 3/136) and pleural effusion (2.2%, 3/136). At diagnosis of IA, most frequently identified predictors of outcome were neutropenia, corticosteroid use, elevated galactomannan, renal failure and disseminated disease. The predictors may be used to identify patients at high risk for treatment failure and to stratify neglected patient groups for clinical trials.

Translational proteomic study to address host protein changes during aspergillosis

Aspergillosis is a fungal disease due to Aspergillus molds that can affect both humans and animals. As routine diagnosis remains difficult, improvement of basic knowledge with respect to its pathophysiology is critical to search for new biomarkers of infection and new therapeutic targets. Large-scale proteomics allows assessment of protein changes during various disease processes. In the present study, mass spectrometry iTRAQ® (isobaric tags for relative and absolute quantitation) protocol was used for direct identification and relative quantitation of host proteins in diseased fluids and tissues collected from an experimental rat model challenged with Aspergillus, as well as in blood obtained from naturally-infected penguins. In all, mass spectrometry analysis revealed that proteome during aspergillosis was mostly represented by proteins that usually express role in metabolic processes and biological process regulation. Ten and 17 proteins were significantly ≥4.0-fold overrepresented in blood of Aspergillus-diseased rats and penguins, respectively, while five and 39 were negatively ≥4.0-fold depleted within the same samples. In rat lungs, 33 proteins were identified with positive or negative relative changes versus controls and were quite different from those identified in the blood. Except for some zinc finger proteins, kinases, and histone transferases, and while three pathways were common (Wnt, cadherin and FGF), great inter-species variabilities were observed regarding the identity of the differentially-represented proteins. Thus, this finding confirmed how difficult it is to define a unique biomarker of infection. iTRAQ® protocol appears as a convenient proteomic tool that is greatly suited to ex vivo exploratory studies and should be considered as preliminary step before validation of new diagnostic markers and new therapeutic targets in humans.

The Multifaceted Role of T-Helper Responses in Host Defense against Aspergillus fumigatus

The ubiquitous opportunistic fungal pathogen Aspergillus fumigatus rarely causes infections in immunocompetent individuals. A healthy functional innate immune system plays a crucial role in preventing Aspergillus-infection. This pivotal role for the innate immune system makes it a main research focus in studying the pathogenesis of aspergillosis. Although sometimes overshadowed by the innate immune response, the adaptive immune response, and in particular T-helper responses, also represents a key player in host defense against Aspergillus. Virtually all T-helper subsets have been described to play a role during aspergillosis, with the Th1 response being crucial for fungal clearance. However; morbidity and mortality of aspergillosis can also be partly attributed to detrimental immune responses resulting from adaptive immune activation. Th2 responses benefit fungal persistence; and are the foundation of allergic forms of aspergillosis. The Th17 response has two sides; although crucial for granulocyte recruitment, it can be involved in detrimental immunopathology. Regulatory T-cells, the endogenous regulators of inflammatory responses, play a key role in controlling detrimental inflammatory responses during aspergillosis. The current knowledge of the adaptive immune response against A. fumigatus is summarized in this review. A better understanding on how T-helper responses facilitate clearance of Aspergillus-infection and control inflammation can be the fundamental basis for understanding the pathogenesis of aspergillosis and for the development of novel host-directed therapies.