Filling the knowledge gap: Scoping review regarding sampling methods, assays, and further requirements to assess airborne viruses.

Assessment of occupational exposure to viruses is crucial to identify virus reservoirs and sources of dissemination at an early stage and to help prevent spread between employees and to the general population. Measuring workers' exposure can facilitate assessment of the effectiveness of protective and mitigation measures in place. The aim of this scoping review is to give an overview of available methods and those already implemented for airborne virus' exposure assessment in different occupational and indoor environments. The results retrieved from the different studies may contribute to the setting of future standards and guidelines to ensure a reliable risk characterization in the occupational environments crucial for the implementation of effective control measures. The search aimed at selecting studies between January 1st 2010 and June 30th 2023 in the selected databases. Fifty papers on virus exposure assessment fitted the eligibility criteria and were selected for data extraction. Overall, this study identified gaps in knowledge regarding virus assessment and pinpointed the needs for further research. Several discrepancies were found (transport temperatures, elution steps, …), as well as a lack of publication of important data related to the exposure conditions (contextual information). With the available information, it is impossible to compare results between studies employing different methods, and even if the same methods are used, different conclusions/recommendations based on the expert judgment have been reported due to the lack of consensus in the contextual information retrieved and/or data interpretation. Future research on the field targeting sampling methods and in the laboratory regarding the assays to employ should be developed bearing in mind the different goals of the assessment.

Nutritional Provision of Iron Complexes by the Major Allergen Alt a 1 to Human Immune Cells Decreases Its Presentation.

Alternaria alternata is a common fungus strongly related with severe allergic asthma, with 80% of affected individuals being sensitized solely to its major allergen Alt a 1. Here, we assessed the function of Alt a 1 as an innate defense protein binding to micronutrients, such as iron-quercetin complexes (FeQ2), and its impact on antigen presentation in vitro. Binding of Alt a 1 to FeQ2 was determined in docking calculations. Recombinant Alt a 1 was generated, and binding ability, as well as secondary and quaternary structure, assessed by UV-VIS, CD, and DLS spectroscopy. Proteolytic functions were determined by casein and gelatine zymography. Uptake of empty apo- or ligand-filled holoAlt a 1 were assessed in human monocytic THP1 cells under the presence of dynamin and clathrin-inhibitors, activation of the Arylhydrocarbon receptor (AhR) using the human reporter cellline AZ-AHR. Human PBMCs were stimulated and assessed for phenotypic changes in monocytes by flow cytometry. Alt a 1 bound strongly to FeQ2 as a tetramer with calculated Kd values reaching pico-molar levels and surpassing affinities to quercetin alone by a factor of 5000 for the tetramer. apoAlt a 1 but not holoAlta 1 showed low enzymatic activity against casein as a hexamer and gelatin as a trimer. Uptake of apo- and holo-Alt a 1 occurred partly clathrin-dependent, with apoAlt a 1 decreasing labile iron in THP1 cells and holoAlt a 1 facilitating quercetin-dependent AhR activation. In human PBMCs uptake of holoAlt a 1 but not apoAlt a 1 significantly decreased the surface expression of the costimulatory CD86, but also of HLADR, thereby reducing effective antigen presentation. We show here for the first time that the presence of nutritional iron complexes, such as FeQ2, significantly alters the function of Alt a 1 and dampens the human immune response, thereby supporting the notion that Alt a 1 only becomes immunogenic under nutritional deprivation.

Validation of a quantitative PCR based detection system for indoor mold exposure assessment in bioaerosols.

Determination and assessment of airborne fungal particles is complex and results of different sampling and analytical strategies are hard to compare due to limitations of each of the techniques. Here, an indoor mold detection system based on quantitative polymerase chain reaction (qPCR) is described and validated for its reliability and stability to identify airborne fungal particles collected. Data obtained from testing the system with fungal DNA, spore suspensions and bioaerosols indicated a need for spiking and normalization of measurements due to material loss and assay specific bias. Considering the loss of material during sample processing, detection limits defined for suspensions of Tritirachium oryzae spores were roughly 18 spores per sample. Detection of fungal spore mixtures nebulized under controlled conditions in a bioaerosol chamber showed generally 2-3 times higher normalized values measured with the molecular system compared to cultivation. Data obtained from a mold infested indoor sampling site and its corresponding outdoor reference measurement showed good correlations between qPCR and high-throughput sequencing (rho = 0.83, p < 0.01), if Cladosporium species were excluded. Taking necessary data normalization into account, the described qPCR detection system shows great potential to complement commonly used culture based approaches with the aim to improve the precision of indoor mold assessments. In contrast to already available qPCR assays that detect certain molds on a species level, this system covers a broad range of relevant fungal communities, serving as a promising alternative to high-throughput sequencing to identify indoor molds.