Pei-Yong Shi, PhD, John Sealy Distinguished Chair in Innovations in Molecular Biology, Vice Chair for Innovation and Commercialization, Department of Biochemistry & Molecular Biology, University of Texas Medical Branch at Galveston, SARS-CoV-2 Biology and Countermeasure Development
Dr. Shi developed recombinant SARS-CoV-2 using reverse genetic technique and this recapitulates phenotype of Washington state isolate (USA-WA1/2020). They later insert a report gene (ORF7) and constructed Reporter SARS-CoV-2, mNeonGreen (mNG) SARS-Co-V-2 for the further use of high-throughput drug screening and neutralizing titer in serum. However, this is required in a BSL-3 environment. To overcome this limitation, they created ΔORF3-E mNG RNA by deleting 2 genes (ORF3 and envelope ORF) from the viral genome and this can be used in the BSL-2 level since the ΔORF3-E mNG virion can infect cell but no further assemble occurs because of the missing components. Animal studies (hamster and K-18-hACE2 mouse) showed no virulence signs with ΔORF3-E mNG virion compare to WT demonstrating the safety of this trans-complement system. The ΔORF3-E mNG virion was utilized for testing neutralization and antiviral testing with patient’s samples. New variant G614 was constructed using reverse genetic and compare the infectivity, fitness with the original D614 SARS-CoV-2. The results of animal and in vitro studies showed that G614 is more thermostable, contagious and transmissible than D614.
UK variant (N501Y) also showed enhanced attachment to receptor binding site and resulted in greater viral replication and infectivity to host cells. They performed neutralization assay with SARS-CoV-2 variants using Pfizer vaccinated serum and neutralization activity was lower with South Africa variant (3 times lower) compare to Washington isolate and this remains a major concern currently.
