The effect of different environmental conditions on the S-protein and RBD binding behavior of SARS-CoV-2

In a recent study published in the journal Scientific reportsa team of researchers investigated the binding behavior of the spike protein (S) and receptor-binding domain (RBD) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) under different environmental conditions.

Study: Binding behavior of spike protein and receptor binding domain of SARS-CoV-2 virus under different environmental conditions. Image Credit: Andrii Vodolazhskyi/Shutterstock

Structural analysis and molecular dynamics simulations have previously revealed that hydrophobic residues on the surfaces of angiotensin-converting enzyme 2 (ACE2) contribute significantly to the strength of its binding to the SARS-CoV-protein. 2 sec.

Food processing facilities, such as meat processing plants, typically maintain high humidity and temperatures below 12°C. Combined with a high concentration of grease particles in the air, these air properties could enhance attachment of SARS-CoV-2 to surfaces in these facilities. A study in Iowa described that a single individual infected with SARS-CoV-2 working in a meatpacking plant led to rampant spread within the meat plant and consequently to 13 surrounding towns. .

Several studies have investigated clusters of SARS-CoV-2 infections among workers in the unique environment of meat processing facilities from different aspects, yielding evidence that these facilities are much more conducive to replication and to the transmission of SARS-CoV-2 due to their environmental conditions. Additionally, while low temperature is known to promote aerosol transmission of SARS-CoV-2, the effect of intermediate temperatures on attachment of SARS-CoV-2 to surfaces remains largely unknown.

About the study

In the present study, researchers investigated the effect of temperature, fatty acids, ions, and protein concentration on the binding behavior of S-protein and RBD of SARS-CoV-2. They presented the binding curves fitted to the local model using BLItz Pro 1.3 software (ForteBio).

In addition, they performed biolayer interferometry (BLI) for kinetic analysis of each of the prepared SARS-CoV-2 protein S and RBD samples mixed with different substances or exposed to different temperatures, using the system of BLItz personal test with aminopropylsilane (APS) biosensors.

The determined rates of association and dissociation of Protein S and RBD were validated using molecular dynamics simulation, and these calculations were displayed in ForteBio’s BLItz Pro 1.3 software.

The researchers analyzed each sample by the BLI at least twice to ensure the reproducibility of the results. Additionally, they used the APS biosensor and phosphate-buffered saline (PBS) in the same way before each experiment to act as a baseline correction for each trial.

Study results

The results showed that three environmental conditions were conducive to binding purified protein S and its receptor-binding domain to hydrophobic surfaces – high ionic concentration, presence of hydrophobic fatty acids, and low temperature. Exposure of protein S to a wide temperature range of 0°C to 25°C within one hour resulted in detachment of protein S, suggesting that freezing induced structural changes in protein S that have affected its binding kinetics, and S recovered only at higher temperature. temperature later.

Experimenting under such conditions helped the researchers simulate the sudden temperature drop commonly seen in meat processing plants as workers move from break rooms to cold or manufacturing rooms. In these facilities, break rooms have 25°C warmer temperatures, and cold or manufacturing rooms typically have temperatures below 12°C due to the presence of dry ice containers to ensure product safety during treatment. As SARS-CoV-2 spreads via aerosols, it may be carried with the airflow through the openings between these locations, exposing more workers to SARS-CoV-2 infection. .

Under all environmental conditions studied, RBD exhibited lower dissociation abilities than full-length trimeric protein S, indicating that it had stronger attachment to hydrophobic surfaces alone than when residing in protein S. Moreover, as revealed by the MD simulation, the presence of fatty acid molecules significantly increased the hydrophobic surface of the RBD, impairing its binding capacity.

Overall, environmental conditions, including low temperature, high humidity, and the presence of fatty acids, of meat processing plants enhanced the binding of SARS-CoV-2 to hydrophobic surfaces, making it impossible elimination of the virus by typical sanitation procedures such as ventilation and watering. Additionally, the increased attachment of the virus to equipment surfaces and worker clothing has imposed higher risks of contact transmission.

Another condition that further contributed to higher transmission of SARS-CoV-2 in meat processing plants was the presence of grease particles in the air. These fatty aerosols strongly adhering to SARS-CoV-2 protein S were entrained in the ventilated airflow and traveled a longer distance, increasing the chances of airborne transmission of SARS-CoV-2.

conclusion

Based on the results of the study, the authors recommended several modifications to alter the environmental conditions of food processing facilities and help protect public health and safety.

Researchers recommended modifying sanitation and cleaning procedures in meat processing plants, such as dousing floors and workbenches with hot water, temporarily heating all surfaces before cleaning and reducing humidity by improving ventilation. All of these measures could increase the chances of eliminating SARS-CoV-2 from these facilities and the effectiveness of disinfection procedures, thus providing a safer environment to protect workers.

Future research should examine SARS-CoV-2 S-protein binding kinetics under higher S-protein concentrations and intermediate temperatures between 0°C and 37°C.

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