ABSTRACT
The coronavirus disease-2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has seriously affected public health around the world. In-depth studies on the pathogenic mechanisms of SARS-CoV-2 is urgently necessary for pandemic prevention. However, most laboratory studies on SARS-CoV-2 have to be carried out in bio-safety level 3 (BSL-3) laboratories, greatly restricting the progress of relevant experiments. In this study, we used a bacterial artificial chromosome (BAC) method to assemble a SARS-CoV-2 replication and transcription system in Vero E6 cells without virion envelope formation, thus avoiding the risk of coronavirus exposure. Furthermore, an improved real-time quantitative reverse transcription PCR (RT-qPCR) approach was used to distinguish the replication of full-length replicon RNAs and transcription of subgenomic RNAs (sgRNAs). Using the SARS-CoV-2 replicon, we demonstrated that the nucleocapsid (N) protein of SARS-CoV-2 facilitates the transcription of sgRNAs in the discontinuous synthesis process. Moreover, two high-frequency mutants of N protein, R203K and S194L, can obviously enhance the transcription level of the replicon, hinting that these mutations likely allow SARS-CoV-2 to spread and reproduce more quickly. In addition, remdesivir and chloroquine, two well-known drugs demonstrated to be effective against coronavirus in previous studies, also inhibited the transcription of our replicon, indicating the potential applications of this system in antiviral drug discovery. Overall, we developed a bio-safe and valuable replicon system of SARS-CoV-2 that is useful to study the mechanisms of viral RNA synthesis and has potential in novel antiviral drug screening.
ABSTRACT
Coronavirus disease 2019 (COVID-19) is a remarkably contagious and pathogenic viral infection arising from the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which first appeared in Wuhan, China. For the time being, COVID-19 is not treated with a specific therapy. The Food and Drug Administration (FDA) has approved Remdesivir as the first drug to treat COVID-19. However, many other therapeutic approaches are being investigated as possible treatments for COVID-19. As part of this review, we discussed the development of various drugs, their mechanism of action, and how they might be applied to different cases of COVID-19 patients. Furthermore, this review highlights an update in the emergence of new prophylactic or therapeutic vaccines against COVID-19. In addition to FDA or The World Health Organization (WHO) approved vaccines, we intended to incorporate the latest published data from phase III trials about different COVID-19 vaccines and provide clinical data released on the networks or peer-review journals.
ABSTRACT
A severe form of pneumonia, named coronavirus disease 2019 (COVID-19) by the World Health Organization, broke out in China and rapidly developed into a global pandemic, with millions of cases and hundreds of thousands of deaths reported globally. The novel coronavirus, which was designated as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified as the etiological agent of COVID-19. On the basis of experience accumulated following previous SARS-CoV and MERS-CoV outbreaks and research, a series of studies have been conducted rapidly, and major progress has been achieved with regard to the understanding of the phylogeny and genomic organization of SARS-CoV-2 in addition its molecular mechanisms of infection and replication. In the present review, we summarized crucial developments in the elucidation of the structure and function of key SARS-CoV-2 proteins, especially the main protease, RNA-dependent RNA polymerase, spike glycoprotein, and nucleocapsid protein. Results of studies on their associated inhibitors and drugs have also been highlighted.