Introduction
The scientific article summarized was written by Lin, Yang, Ou, Wang, Lo, Tsai, and Wu, titled “The impacts of antivirals on the coronavirus genome structure and subsequent pathogenicity, virus fitness, and antiviral design.” It was published in September 2020 by the Biomedicines Journal. The primary focus of the study was to test the changes in resistance, pathogenicity, and genome structure of the bovine coronavirus variant (BCoV) under treatment. The researchers conducted experiments to determine how and whether treated viruses changed their characteristics, which are medically significant outcomes (Lin et al., 2020). This summary focuses on the type of cells used, experiments conducted, applied treatments, the experiments’ findings, and the authors’ conclusions.
Data Collection
The experiment began with collecting the required cells from David A. Brian, which included Mouse L (ML) and human rectum tumor (HRT)-18 cells. These cells were preserved at 37 °C in a Dulbecco’s modified Eagle’s medium (DMEM) containing 10% fetal bovine serum and 5% CO2. BCoV strain, plaque-purified in HRT-18 cells, was also collected from David A. Brian (Lin et al., 2020). The treatment started with an infection of the cells with a wild-type (wt) BCoV (Lin et al., 2020). In addition, virus samples were collected at the end of every step in the experiment and given different labels.
The multiplicity of infection (MOI) during treatment was maintained at one every hour, and antiviral remdesivir (GS-5734) was used for treatment. MERS-CoV and SARS-CoV-1 replication inhibition is achieved at a concentration of 10 µM (Lin et al., 2020). After every infection, the virus was collected and passaged through fresh HRT-18 cells in the presence of antivirals up to ten times.
The virus was then collected at the tenth passage with and without GS-5734 for testing and labeled WtGS10 and Wt10, respectively. Constant pressure testing involved transfecting or mock-transfecting HRT-18 cells with polyinosinic (poly IC) in a maximum concentration of 1 µg/mL (Lin et al., 2020). The head-to-tail ligation method determined BCoV’s genome structure and the mutations experienced after treatments.
Findings
The researchers found that GS-5734 treatments and poly IC pressure effect changed BCoV’s genome structure, but pathogenicity did not increase in any cases. BCoV developed resistance after repeated GS-5734 treatments, but did not develop resistance with poly IC treatment. Another important finding is that the cells collected after GS-5734 treatment and ten HRT-18 cell passages, namely WtGS10, showed higher efficiency at adapting to ML cells than those collected without the GS-5734 antiviral, Wt10. The genome alteration caused by GS-5734 and poly IC mainly occurred in the S protein and other proteins linked to replication, like N protein and nsps 1, 3, 6, 8, 9, and 14 (Lin et al., 2020). Therefore, the researchers found that treatment with an antivirus and transfection pressure created significant mutations in disease control and transmission.
Northern blotting technique showed that GS-5734 contained viral synthesis inhibitory ability, and poly IC induced an innate immunity, preventing an increase in pathogenicity. HRT-18 cells were treated and infected with viruses after the tenth passage with poly IC and GS-5734 to test resistance. A plaque assay test of the virus collected after 24 hours in GS-5734 had a three-fold increase in titer and around a 20% increase in viral synthesis, indicating resistance (Lin et al., 2020).
However, the poly IC virus had no statistically significant differences, indicating a lack of resistance. ML cells were infected with the virus collected after the tenth passage with and without GS-5734 to determine the effect of the aa substitutions observed in the S protein on the virus’s adaptability to different host cells (Lin et al., 2020). The virus collected in the presence of GS-5734 adapted to the ML cells more efficiently than that collected without it, which would affect disease control and interspecies transmission.
Conclusion
The article presented essential findings in the development of solutions for coronaviruses. The researchers established that coronaviruses did not increase pathogenicity when treated with an antiviral or due to constant pressure. However, they found a mutations that have a statistically significant impact on antiviral treatments and control. The genome alterations observed in the S, N, and nsps proteins have replication effects and contribute to resistance. In addition, the WtGS10 virus could adapt to different cell hosts, impacting interspecies control and transmission of the coronaviruses.
Reference
Lin CH, Yang CY, Ou SC, Wang M, Lo CY, Tsai TL, Wu HY. 2020. The impacts of antivirals on the coronavirus genome structure and subsequent pathogenicity, virus fitness, and antiviral design. Biomedicines, 8(10):376.