Electron Microscopy in Virus Research and Infection Prevention

In the given situation, dealing with COVID-19 pandemic, highly functional and reliable protective masks and clothings are of prime importance to protect the health of system employees and save lives.

A crucial question in this context is how to measure the filtering characteristics of these materials.

The FFG COIN project Aeropore (856321), a cooperative project between the Graz Centre for Electron Microscopy (ZFE) and the OFI Technologie & Innovation GmbH in Vienna, concentrates on this topic by developing and installing a new filter test rig, which is capable of testing filter materials under very realistic conditions. Conventional filter test rigs are using standardized test dust to measure filters, which results in very inaccurate parameters especially in the context of pathogenic germs (bacteria and viruses) and allergenic substances (pollen grains etc.) [1].

In contrast, this unique test rig can work with paraffin oil aerosols to check filtration characteristics of protective mask materials. All these investigations at the OFI are accompanied by high-resolution scanning electron microscopy (HRSEM) investigations to assess the aerosol diameters (to be as close to reality as possible) and the specific areas and cross-sections of filter materials (new and aged). It is the aim of this work to improve the understanding of how to filtrate viruses in an effective way to design new and more effective protection masks and clothings.

The enormous importance of electron microscopy (EM) in life sciences was impressively verified by awarding cryo electron microscopy (cryoTEM) with the Nobel price in chemistry 2017. Especially in virus research, this technique provides unique possibilities. For example in 2016 the structure of the Zika virus (i.e. flavivirus) was analyzed by cryoEM which is a key step to understand how a special protein interacts with other compounds in the body. The high-resolution EM images (resolution 3.8 Å) enabled to compare its protein interactions with those of other well-known types of flaviviruses [2]. With such knowledge, researchers were able to identify probable drug-binding pockets, which helps scientists to design vaccines and anti-viral compounds. At the moment, as a result of the COVID-19 pandemic, researcher all over the world are investigating the new SARS-CoV-2 virus again via EM to save lives, stop the global pandemic and design vaccines which are absolutely essential [3]. Besides cryoTEM, high-resolution TEM images can be acquired using the negative staining technique (see rotavirus micrograph).

 

Transmission electron micrograph of rotaviruses (negative staining,
virus diameter 76 nm) – courtesy of Elisabeth Ingolic (FELMI – ZFE)

 

The new filter test rig

 

Backscattered electron micrograph of a filter surface  and cross section

 

[1] Journal of Hospital Infection, 2006 Vol. 64, pp. 100-114, DOI: 10.1016/j.jhin.2006.05.022

[2] Science, 2016 Apr 22; Vol. 352, Issue 6284, pp. 467-470, DOI: 10.1126/science.aaf5316.

[3] Science,  2020 Mar 13; Vol. 367, Issue 6483, pp. 1260-1263, DOI: 10.1126/science.abb2507