Initiation and Pathogenesis of Severe Asthma with Fungal Sensitization

A comprehensive review on the role of T cell subsets and CAR-T cell therapy in Aspergillus fumigatus infection

Understanding the immune response to Aspergillus fumigatus, a common cause of invasive fungal infections (IFIs) in immunocompromised individuals, is critical for developing effective treatments. Tcells play a critical role in the immune response to A. fumigatus, with different subsets having distinct functions. Th1 cells are important for controlling fungal growth, while Th2 cells can exacerbate infection. Th17 cells promote the clearance of fungi indirectly by stimulating the production of various antimicrobial peptides from epithelial cells and directly by recruiting and activating neutrophils. Regulatory T cells have varied functions in A.fumigatus infection. They expand after exposure to A. fumigatus conidia and prevent organ injury and fungal sepsis by downregulating inflammation and inhibiting neutrophils or suppressing Th17 cells. Regulatory T cells also block Th2 cells to stop aspergillosis allergies. Immunotherapy with CAR T cells is a promising treatment for fungal infections, including A. fumigatus infections, especially in immunocompromised individuals. However, further research is needed to fully understand the mechanisms underlying the immune response to A. fumigatus and to develop effective immunotherapies with CAR-T cells for this infection. This literature review explores the role of Tcell subsets in A.fumigatus infection, and the effects of CAR-T cell therapy on this fungal infection.

Relationship between Aspergillus and asthma

Fungal sensitization is highly prevalent in severe asthma. The relationship between fungus and asthma, especially Aspergillus fumigatus, has been the subject of extensive research. The ubiquitous presence of A. fumigatus, its thermotolerant nature, the respirable size of its conidia, and its ability to produce potent allergens are pivotal in worsening asthma control. Due to the diverse clinical manifestations of fungal asthma and the lack of specific biomarkers, its diagnosis remains intricate. Diagnosing fungal asthma requires carefully assessing the patient's clinical history, immunological tests, and imaging. Depending on the severity, patients with fungal asthma require personalized treatment plans, including inhaled corticosteroids and bronchodilators, and antifungal therapy. This review provides a comprehensive overview of the association between Aspergillus and asthma by reviewing the relevant literature and highlighting key findings. We discuss the diagnosis of various entities included in fungal asthma. We also debate whether newer definitions, including allergic fungal airway disease, offer any additional advantages over the existing ones. Finally, we provide the current treatment options for the individual entities, including A. fumigatus-associated asthma, severe asthma with fungal sensitization, and allergic bronchopulmonary mycoses.

Clinical Manifestations of Human Exposure to Fungi

Biological particles, along with inorganic gaseous and particulate pollutants, constitute an ever-present component of the atmosphere and surfaces. Among these particles are fungal species colonizing almost all ecosystems, including the human body. Although inoffensive to most people, fungi can be responsible for several health problems, such as allergic fungal diseases and fungal infections. Worldwide fungal disease incidence is increasing, with new emerging fungal diseases appearing yearly. Reasons for this increase are the expansion of life expectancy, the number of immunocompromised patients (immunosuppressive treatments for transplantation, autoimmune diseases, and immunodeficiency diseases), the number of uncontrolled underlying conditions (e.g., diabetes mellitus), and the misusage of medication (e.g., corticosteroids and broad-spectrum antibiotics). Managing fungal diseases is challenging; only four classes of antifungal drugs are available, resistance to these drugs is increasing, and no vaccines have been approved. The present work reviews the implications of fungal particles in human health from allergic diseases (i.e., allergic bronchopulmonary aspergillosis, severe asthma with fungal sensitization, thunderstorm asthma, allergic fungal rhinosinusitis, and occupational lung diseases) to infections (i.e., superficial, subcutaneous, and systemic infections). Topics such as the etiological agent, risk factors, clinical manifestations, diagnosis, and treatment will be revised to improve the knowledge of this growing health concern.

More than Just Protein Degradation: The Regulatory Roles and Moonlighting Functions of Extracellular Proteases Produced by Fungi Pathogenic for Humans

Extracellular proteases belong to the main virulence factors of pathogenic fungi. Their proteolytic activities plays a crucial role in the acquisition of nutrients from the external environment, destroying host barriers and defenses, and disrupting homeostasis in the human body, e.g., by affecting the functions of plasma proteolytic cascades, and playing sophisticated regulatory roles in various processes. Interestingly, some proteases belong to the group of moonlighting proteins, i.e., they have additional functions that contribute to successful host colonization and infection development, but they are not directly related to proteolysis. In this review, we describe examples of such multitasking of extracellular proteases that have been reported for medically important pathogenic fungi of the Candida, Aspergillus, Penicillium, Cryptococcus, Rhizopus, and Pneumocystis genera, as well as dermatophytes and selected endemic species. Additional functions of proteinases include supporting binding to host proteins, and adhesion to host cells. They also mediate self-aggregation and biofilm formation. In addition, fungal proteases affect the host immune cells and allergenicity, understood as the ability to stimulate a non-standard immune response. Finally, they play a role in the proper maintenance of cellular homeostasis. Knowledge about the multifunctionality of proteases, in addition to their canonical roles, greatly contributes to an understanding of the mechanisms of fungal pathogenicity.

Human matters in asthma: Considering the microbiome in pulmonary health

Microbial communities form an important symbiotic ecosystem within humans and have direct effects on health and well-being. Numerous exogenous factors including airborne triggers, diet, and drugs impact these established, but fragile communities across the human lifespan. Crosstalk between the mucosal microbiota and the immune system as well as the gut-lung axis have direct correlations to immune bias that may promote chronic diseases like asthma. Asthma initiation and pathogenesis are multifaceted and complex with input from genetic, epigenetic, and environmental components. In this review, we summarize and discuss the role of the airway microbiome in asthma, and how the environment, diet and therapeutics impact this low biomass community of microorganisms. We also focus this review on the pediatric and Black populations as high-risk groups requiring special attention, emphasizing that the whole patient must be considered during treatment. Although new culture-independent techniques have been developed and are more accessible to researchers, the exact contribution the airway microbiome makes in asthma pathogenesis is not well understood. Understanding how the airway microbiome, as a living entity in the respiratory tract, participates in lung immunity during the development and progression of asthma may lead to critical new treatments for asthma, including population-targeted interventions, or even more effective administration of currently available therapeutics.

A Case of Allergic Bronchopulmonary Aspergillosis With Bronchial Asthma

Allergic bronchopulmonary aspergillosis (ABPA) is a fungal hypersensitivity reaction in chronic lung diseases like bronchial asthma and cystic fibrosis. It is caused by an allergic reaction to aspergillus antigen in the lung mucus resulting in airway inflammation and damage. This condition usually presents in a patient with asthma as a poorly controlled disease with recurrent infection symptoms that do not respond to standard antibiotic therapy. Diagnosis is made by chest X-ray, computed tomography, eosinophilia, and raised serum IgE on serology and immunological tests for aspergillus antigen. Lack of diagnosis and treatment of the condition can lead to respiratory failure from bronchiectasis and pulmonary fibrosis.

Registry analysis of patients with severe allergic asthma and clinically relevant sensitization to fungal allergens treated with genetically engineered biologics

Background. Fungal sensitization (FS) often escapes the attention of clinicians when assessing the spectrum of sensitization in patients with atopic diseases. According to cohort studies is found in 310% of the general population and in 720% of asthmatics; the proportion of patients with severe bronchial asthma (SBA) with HS ranges from 35 to 75%. Fungal conidia have a 1000-fold higher exposure and are among the most important clinically relevant allergens in asthma. Exposure to fungal allergens is capable of generating a sustained T2 response with production of proinflammatory cytokines such as IL-5 and 13, which is indirectly related to the severity of airway eosinophilia. The identification of specific serum IgE is considered the benchmark diagnostic sign of FS, and the encapsulated hydrophobic carrier polymer system is considered preferable to skin prick tests. The process of reclassifying diseases with fungal lung lesions is confusing treatment strategies, leaving the FS problem underestimated. A series of publications have shown that omalizumab and other biologics targeting IL-5 or IL-5 receptor (IL5R) alpha are effective in treating SBA with FS. However, there remains an unmet need in real clinical practice for standardized approaches to genetically engineered biological therapies (BT) for different phenotypes of SBA, especially those associated with impaired microbiological homeostasis and this type of sensitization. Aim. Using retrospective analysis of clinical-dynamic observational data from patients on BT treatment in a real clinical setting to determine phenotypic features of severe allergic bronchial asthma with FS and to perform additional detailed analysis of a cohort of patients on anti-IgE therapy. Materials and methods. A retrospective observational single-center registry study was conducted between June 2017 and August 2021 at the City Reference Center for Allergology and Immunology. The baseline cohort consisted of 198 patients with severe allergic AD who were in the initial phase of BT. Inclusion criteria: age of patients over 18 years; presence of severe allergic bronchial asthma. Complex initial examination of patients included determination of FS by two methods: ImmunoCap ISAC to fungal allergic components alt a1, alt 6 (fungi of genus Alternaria) and asp f1, asp f3, asp f6 (fungi of genus Aspergillus). Specific IgE determinations on fungal panels. Sensitization to fungi was detected in 47 people during allergy examination. The following criteria were considered in evaluation of response to omalizumab: AST score less than 19 and/or difference between initial AST score and this score in dynamics less than 3 points; FEV 1 score less than 80; combination of 2 listed criteria. The minimum period of BT was 16 weeks. Nonparametric methods of descriptive statistics were used: median, interquartile range. Differences were considered significant at p0.05. Data were statistically processed using nonparametric methods in IBM SPSS Statistics V-22 program. MannWhitney U-test and KruskalWallis one-way analysis of variance were used to compare quantitative characteristics. Fisher's 2 test was used to compare qualitative characteristics. Results. Characteristics of the eosinophilic phenotype of SBA combined with FS: middle-aged patients, more often women, with relatively early onset of AD and high baseline eosinophil levels before prescription of biological drug therapy. Concomitant atopic dermatitis and food allergies are additional frequent features of this phenotype. Analysis of the effect of FS on achieving response to omalizumab and further consideration of switching to alternative therapy in SBA and FS patients showed the need to avoid premature revision and perform no earlier than the 10th month of therapy due to delayed response formation. Given the aggressive impact of FS on the barrier functions of the bronchial tree epithelium, it is advisable to test patients for FS at the initial diagnosis of AD. In the presence of atopic dermatitis and/or food allergy as T2 comorbidities in patients with SBA, early testing for FS and increased control of local and systemic inflammation are appropriate, which may improve long-term outcomes and reduce risks of further damage to natural barriers. Conclusion. Further research on various aspects of FS and its role in allergic diseases is extremely relevant in the current context.

Impact of Therapeutics on Unified Immunity During Allergic Asthma and Respiratory Infections

Asthma is a common chronic respiratory disease that affects millions of people worldwide. Patients with allergic asthma, the most prevalent asthma endotype, are widely considered to possess a defective immune response against some respiratory infectious agents, including viruses, bacteria and fungi. Furthermore, respiratory pathogens are associated with asthma development and exacerbations. However, growing data suggest that the immune milieu in allergic asthma may be beneficial during certain respiratory infections. Immunomodulatory asthma treatments, although beneficial, should then be carefully prescribed to avoid misuse and overuse as they can also alter the host microbiome. In this review, we summarize and discuss recent evidence of the correlations between allergic asthma and the most significant respiratory infectious agents that have a role in asthma pathogenesis. We also discuss the implications of current asthma therapeutics beyond symptom prevention.

Purified Native and Recombinant Major Alternaria alternata Allergen (Alt a 1) Induces Allergic Asthma in the Murine Model

Aeroallergens such us the spores of Alternaria alternata are described as the most important agents associated with respiratory allergies and severe asthma. Various experimental models of asthma have been developed using A. alternata extracts to study the pathogenesis of asthma, establishing the main parameters that trigger the asthmatic response. In this study, we describe a mouse model of asthma induced only by Alt a 1. To induce the allergic response, mice were challenged intranasally with the major allergen of A. alternata, Alt a 1. The presence of eosinophils in the lungs, elevated concentrations of Th2 family cytokines, lymphocyte proliferation and elevated IgE total serum levels indicated that the sensitisation and challenge with Alt a 1 induced the development of airway inflammation. Histological studies showed an eosinophilic cellular infiltrate in the lung tissue of mice instilled with Alt a 1. We demonstrate that Alt a 1 alone is capable of inducing a lung inflammatory response with an increase in IgE serum levels mimicking the allergic asthma immunoresponse when it is administered into BALB/c mice. This model will allow the evaluation of the immunoregulatory or immunotolerant capacity of several molecules that can be used in targeted immunotherapy for fungal allergic asthma.