A new study by researchers from Texas A&M University-USA has found that environmental conditions with high ionic concentration, presence of hydrophobic fatty acids, and low temperature enhances the binding behavior of both the spike protein and receptor binding domain of SARS-Cov-2 virus.
Such environmental conditions are typical in most meat processing plants.
Though extensive research has been performed on SARS-CoV-2, the binding behavior of spike (S) protein and receptor binding domain (RBD) of SARS-CoV-2 at different environmental conditions have yet to be studied.
The study findings were published in the peer reviewed journal: Scientific Reports (Nature). https://www.nature.com/articles/s41598-021-04673-y
In this study, three conditions are identified to enhance the attachment of the purified S protein and its RBD to hydrophobic surfaces: high ionic concentration, presence of hydrophobic fatty acids, and low temperature. The S protein exposed to a wide temperature change from 0 °C to 25 °C within one hour results in S protein detachment, suggesting that freezing can cause structural changes in the S protein that affect its binding kinetics after it is recovered at higher temperature.
This rapid change of temperature within an hour was applied to simulate the sudden temperature drop which is common in meat processing plants when the workers move between warmer and colder locations in the facility, for example, from the 25 °C breakroom to the chiller or fabrication rooms where temperature is kept low, usually < 12 °C, and even lower due to the presence of dry ice containers to keep the products safe during processing.
At all the conditions, RBD exhibits lower dissociation capabilities than the full-length S trimer protein, indicating that the separated RBD formed stronger attachment to hydrophobic surfaces compared to when it was included in the S protein.
The interaction between RBD of S protein and APS ligand was verified via molecular docking. MD simulation further revealed that the presence of fatty acid molecules has the potential to increase the hydrophobic surface area of RBD, changing its binding ability.
The findings of this study implied that certain environmental conditions – low temperature, high humidity, and presence of fatty acids— – hat are typical in critical infrastructures such as meat processing plants enhance the binding by the S protein and RBD of the SARS-CoV-2 to hydrophobic surfaces. Under such conditions, SARS-CoV-2 is harder to be removed through typical sanitation procedures such as ventilation and hosing due to the enhanced attachment.
The findings also suggested that the environmental conditions affect the transmission of SARS-CoV-2. With the presence of fat particles in the air, the binding can form between SARS-CoV-2 Spike and fat aerosols, which are entrained in the ventilated airflow and can travel for a longer distance, increasing the chances of airborne transmission of the virus.
The enhanced attachment of the virus to equipment surfaces and workers’ clothes makes sanitation challenging and can lead to longer residence time of the virus and impose higher risks to contact transmission. This study helps recommend necessary modifications to sanitation and cleaning procedures in meat processing plants.
For example, hosing the floors and workbenches with warm water, heating the surface temporarily before cleaning, and modifying the mode of ventilation to reach a lower humidity can potentially increase the efficiency of removing SARS-CoV-2 from the facilities and providing a safer and cleaner environment to protect workers.
The MD simulation can be performed in the future on S protein and RBD at 0 °C to assess any structural changes in low temperature environments.
A past study conducted in Iowa described that a single SARS-CoV-2-infected individual working at a meatpacking plant led to unrestrained spread within the meat facility and consequently in 13 surrounding cities. https://www.medrxiv.org/content/10.1101/2020.06.08.20125534v1
A few studies have investigated the clusters of SARS-CoV-2 infections among the workers in the unique environment of meat processing facilities from different aspects, producing evidence that these facilities are far more conducive to SARS-CoV-2 replication and transmission due to their environmental conditions. https://pubmed.ncbi.nlm.nih.gov/34111143/