ABSTRACT
One of the structural uniqueness of arylnaphthalene lignans (ANLs) is their potential atropoisomerism, which may result in bioactivity discrepancy. However, the stable ANL atropisomers rarely exist in nature. In the course of our phytochemical study of Justicia procumbens, we isolated nine ANL glycosides (1-9) with four of them (1-4) being identified as new stable atropisomers. Their absolute configurations were determined based on the analysis of the circular dichroism (CD) and electronic circular dichroism (ECD) data. The ANL compounds were evaluated for their antiviral potential as entry inhibitors against the infections of H5N1 influenza virus, vesicular stomatitis virus (VSV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with 5 being the most potent one with IC50 values ranging from 0.0063-1.13 mu M. The atropisomers did not display significant antiviral activity, indicating that a free rotation of the biphenyl aryl-aryl bond could play a significant role in the antiviral activity of ANL compounds.
ABSTRACT
Research activities with infectious severe acute respiratory syndrome corona-virus 2 (SARS-CoV-2) are currently permitted only under biosafety level 3 (BSL3) containment. Here, we report the development of a single-cycle infectious SARS-CoV-2 virus replicon particle (VRP) system with a luciferase and green fluorescent protein (GFP) dual reporter that can be safely handled in BSL2 laboratories to study SARS-CoV-2 biology. The spike (S) gene of SARS-CoV-2 encodes the envelope glycoprotein, which is essential for mediating infection of new host cells. Through deletion and replacement of this essential S gene with a luciferase and GFP dual reporter, we have generated a conditional SARS-CoV-2 mutant (Delta S-VRP) that produces infectious particles only in cells expressing a viral envelope glycoprotein of choice. Interestingly, we observed more efficient production of infectious particles in cells expressing vesicular stomatitis virus (VSV) glycoprotein G [Delta S-VRP(G)] than in cells expressing other viral glycoproteins, including S. We confirmed that infection from Delta S-VRP(G) is limited to a single round and can be neutralized by anti-VSV serum. In our studies with Delta S-VRP(G), we observed robust expression of both luciferase and GFP reporters in various human and murine cell types, demonstrating that a broad variety of cells can support intracellular replication of SARS-CoV-2. In addition, treatment of Delta S-VRP(G)-infected cells with either of the anti-CoV drugs remdesivir (nucleoside analog) and GC376 (CoV 3CL protease inhibitor) resulted in a robust decrease in both luciferase and GFP expression in a drug dose-and cell-type-dependent manner. Taken together, our findings show that we have developed a single-cycle infectious SARS-CoV-2 VRP system that serves as a versatile platform to study SARS-CoV-2 intracellular biology and to perform high-throughput screening of antiviral drugs under BSL2 containment. IMPORTANCE Due to the highly contagious nature of SARS-CoV-2 and the lack of immunity in the human population, research on SARS-CoV-2 has been restricted to biosafety level 3 laboratories. This has greatly limited participation of the broader scientific community in SARS-CoV-2 research and thus has hindered the development of vaccines and anti-viral drugs. By deleting the essential spike gene in the viral genome, we have developed a conditional mutant of SARS-CoV-2 with luciferase and fluorescent reporters, which can be safely used under biosafety level 2 conditions. Our single-cycle infectious SARS-CoV-2 virus replicon system can serve as a versatile platform to study SARS-CoV-2 intracellular biology and to perform high-throughput screening of antiviral drugs under BSL2 containment.
ABSTRACT
The epidemic caused by coronavirus poses a serious threat to human health, but there is no specific drug or vaccine for the treatment of this kind of virus infection. Herein, this article selects typical case studies in recent years and reviews the medicinal chemistry strategies of anti-SARS-CoV, MERS-CoV and other coronavirus drugs from the perspective of medicinal chemistry, and tries to provide some clues to current drug research against-SARS-CoV-2.