The SARS-CoV-2 pandemic revealed large gaps in the knowledge of aerosol-borne viruses, raising fundamental questions regarding their spread in enclosed rooms, the preventive measures of protective masks up to air filters and the efficiency of inactivation processes of air purifiers. The innovation field of Virus-based Technologies has established a comprehensive and adaptable workflow to address these questions.
To establish a test system, several viruses were considered as surrogates for SARS-CoV-2. The decision was made for bacteriophage Phi6, which is similar to SARS-CoV-2 with regard to its morphological characteristics like viral envelope and RNA genome content, but is neither harmful to animals nor to humans. Propagation of Phi6 is performed on specific host bacteria. To ensure a maximum yield from Phi6 propagation as required for testing, a scaled production process based on a liquid culture was established. In parallel, we use the human coronavirus 229E (HCoV-229E), a common and widespread cold virus, as additional surrogate virus for specific queries.
To record the presence and/or infectivity of surrogate viruses, detection methods for active, infectious viral particles and for total viral genome counts were established. Virus activity is detected via phage plaque assay, allowing detection of lytic spots on a bacterial lawn (so called plaques) that correspond to the number of active, infectious viral particles, which is used for quantification. In addition, a Phi6-specific RT-qPCR approach was established to record all viral particles, present in active or inactive state, on the genomic level. This serves as both, a reference for the degree of inactivation and for virus depletion.
An aerosolization chamber was developed to facilitate closed aerosolization and analysis of surrogate and infectious airborne viruses. For aerosolization procedures, viruses are formulated in an appropriate medium and filled in an aerosol generator hooked up to the chamber. A sampling procedure for aerosolized viruses was established using swabs, allowing the sampling of infectious viruses for further analysis.
These tools enable us to use a comprehensive and flexible workflow for all kinds of requests in terms of airborne viruses.
In addition to burning issues like virus inactivation using UV-C irradiation, we are preparing for future challenges and are already expanding our testing capabilities for aerosols containing fungal spores and bacteria.
We will be happy to advise you in order to develop solutions for your specific issues.
Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB