Ex vivo cytokine release and pattern recognition receptor expression of subjects exposed to dampness: pilot study to assess the outcome of mould exposure to the innate immune system

AWMF mold guideline "Medical clinical diagnostics for indoor mold exposure" - Update 2023 AWMF Register No. 161/001

None.

Is in vitro cytokine release a suitable marker to improve the diagnosis of suspected mold-related respiratory symptoms? A proof-of-concept study

Indoor mold infestation can lead to a variety of adverse health effects, including allergic and non-allergic respiratory complaints. Especially if no evidence of an allergic reaction can be found for the complaints, diagnostic tools that might explain mold-associated health problems are missing. As a proof-of-concept, in the present study whole blood assay (WBA) was used to determine cellular response by measuring cytokine release (IL-1β and IL-8) after in vitro stimulation. Blood was available from a total of 48 subjects. By questionnaire, complaints and possible mold exposure were documented. Specific in vitro blood stimulation was tested with Escherichia coli endotoxin and extracts of different molds (Aspergillus fumigatus, Penicillium chrysogenum, Aspergillus versicolor, and Cladosporium herbarum). To characterize the relevance of WBA in describing the mold-induced immune response, we compared the following groups: asthmatics vs. non-asthmatics, mx1-sensitized vs. non-mx1-sensitized, mold-exposed vs. non-mold-exposed. In response to endotoxin stimulation, a significantly higher IL-1β release was found in mx1-sensitized than in non-mx1-sensitized subjects. Furthermore, the blood of asthmatics showed significantly higher IL-8 and IL-1β release after stimulation with Penicillium chrysogenum and endotoxin, respectively, compared to non-asthmatics. However, no significant difference in the level of cytokine release was observed between the mold-exposed and non-exposed group, neither after endotoxin nor mold stimulation. In conclusion, the WBA used in this study is not a suitable tool for clinical routine diagnostic workup. Our data suggests that WBA reflects cellular differences that are disease-related but not directly attributable to mold exposure. However, in combination with further data, WBA will be a helpful und interesting tool in research, e.g., in description of the complex immune response to molds.

Characterization and pro-inflammatory potential of indoor mold particles

A number of epidemiological studies find an association between indoor air dampness and respiratory health effects. This is often suggested to be linked to enhanced mold growth. However, the role of mold is obviously difficult to disentangle from other dampness-related exposure including microbes as well as non-biological particles and chemical pollutants. The association may partly be due to visible mycelial growth and a characteristic musty smell of mold. Thus, the potential role of mold exposure should be further explored by evaluating information from experimental studies elucidating possible mechanistic links. Such studies show that exposure to spores and hyphal fragments may act as allergens and pro-inflammatory mediators and that they may damage airways by the production of toxins, enzymes, and volatile organic compounds. In the present review, we hypothesize that continuous exposure to mold particles may result in chronic low-grade pro-inflammatory responses contributing to respiratory diseases. We summarize some of the main methods for detection and characterization of fungal aerosols and highlight in vitro research elucidating how molds may induce toxicity and pro-inflammatory reactions in human cell models relevant for airway exposure. Data suggest that the fraction of fungal hyphal fragments in indoor air is much higher than that of airborne spores, and the hyphal fragments often have a higher pro-inflammatory potential. Thus, hyphal fragments of prevalent mold species with strong pro-inflammatory potential may be particularly relevant candidates for respiratory diseases associated with damp/mold-contaminated indoor air. Future studies linking of indoor air dampness with health effects should assess the toxicity and pro-inflammatory potential of indoor air particulate matter and combined this information with a better characterization of biological components including hyphal fragments from both pathogenic and non-pathogenic mold species. Such studies may increase our understanding of the potential role of mold exposure.

Early age exposure to moisture damage and systemic inflammation at the age of 6 years

Cross-sectional studies have shown that exposure to indoor moisture damage and mold may be associated with subclinical inflammation. Our aim was to determine whether early age exposure to moisture damage or mold is prospectively associated with subclinical systemic inflammation or with immune responsiveness in later childhood. Home inspections were performed in children's homes in the first year of life. At age 6 years, subclinical systemic inflammation was measured by serum C-reactive protein (CRP) and blood leukocytes and immune responsiveness by ex vivo production of interleukin 1-beta (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α) in whole blood cultures without stimulation or after 24 hours stimulation with phorbol 12-myristate 13-acetate and ionomycin (PI), lipopolysaccharide (LPS), or peptidoglycan (PPG) in 251-270 children. Moisture damage in child's main living areas in infancy was not significantly associated with elevated levels of CRP or leukocytes at 6 years. In contrast, there was some suggestion for an effect on immune responsiveness, as moisture damage with visible mold was positively associated with LPS-stimulated production of TNF-α and minor moisture damage was inversely associated with PI-stimulated IL-1β. While early life exposure to mold damage may have some influence on later immune responsiveness, it does not seem to increase subclinical systemic inflammation in later life.

Moisture damage in home associates with systemic inflammation in children

This study investigated the association between confirmed moisture damage in homes and systemic subclinical inflammation in children. Home inspections were performed in homes of 291 children at the age of 6 years. Subclinical inflammation at the age of 6 years was assessed by measuring the circulating levels of C-reactive protein (CRP) and leukocytes in peripheral blood and fractional exhaled nitric oxide (FeNO). Proinflammatory cytokines interleukin (IL)-1β and IL-6 and tumor necrosis factor (TNF)-α were measured in unstimulated, and in phorbol 12-myristate 13-acetate and ionomycin (PI), lipopolysaccharide (LPS), or peptidoglycan (PPG)-stimulated whole blood. Major moisture damage in the child's main living areas (living room, kitchen, or child's bedroom) and moisture damage with mold in the bathroom were associated with increased levels of CRP and stimulated production of several proinflammatory cytokines. There were no significant associations between moisture damage/visible mold and leukocyte or FeNO values. The results suggest that moisture damage or mold in home may be associated with increased systemic subclinical inflammation and proinflammatory cytokine responsiveness.

Determination of ATP-activity as a useful tool for monitoring microbial load in aqueous humidifier samples

Air humidifier water tanks are potential sources of microbial contaminants. Aerosolization of these contaminants is associated with the development of airway and lung diseases; therefore, implementation of preventive strategies including monitoring of the microbial contamination is recommended. So far, culture-based methods that include measuring colony forming units (CFU) are widely used to monitor microbial load. However, these methods are time consuming and have considerable drawbacks. As a result, alternative methods are needed which provide not only clear and accurate results concerning microbial load in water samples, but are also rapid and easy to use in the field. This paper reports on a rapid test for ATP quantification as an alternative method for microbial monitoring, including its implementation, validation and application in the field. For this purpose, 186 water samples were characterized with different methods, which included ATP analysis, culture-based methods, endotoxin activity (common and rapid test), pyrogenic activity and number of particles. Half of the samples was measured directly in the field and the other half one day later in the laboratory. The results of both tests are highly correlated. Furthermore, to check how representative the result from one sample of a water source is, a second sample of the same water tank were collected and measured. Bioluminescence results of the undiluted samples covered a range between 20 and 25,000 relative light units (RLU) and correlated with the results obtained using the other methods. The highest correlation was found between bioluminescence and endotoxin activity (rs=0.79) as well as pyrogenic activity (rs=0.75). Overall, the results of this study indicate that ATP measurement using bioluminescence is a suitable tool to obtain rapid, reproducible and sensitive information on the microbial load of water samples, and is suitable to use in the field. However, to use ATP measurement as an indicator of water quality, criteria of assessment has to be discussed.