COVID-19, volatility dynamics, and sentiment trading.

In this paper, we study how different categories of crucial COVID-19 information influence price dynamics in stock and option markets during the period from 01/21/20 to 01/31/21. We present a theoretical model in which the behavioral traders make perceptual errors based on the intensity of sentiment arising from different types of news. In addition to the magnitude and direction of the news and its payoff relevance to security prices, other factors such as fear, emotion, and social media can influence the sentiment level. Using Google search data, we construct novel proxies for the sentiment levels induced by five categories of news, COVID, Market, Lockdown, Banking, and Government relief efforts. If the relative presence of behavioral traders in the stock market exceeds that in the option market, different predictions obtain for the effect of sentiment indices on jump volatility of the VIX index, the S&P 500 index, and the S&P 500 Banks index. We find that the jump component in the VIX index is increasing significantly with COVID index, Market index, Lockdown index, and Banking index. However, only COVID index and Market index increase the jump component of realized volatility of the stock indices (S&P 500 index and S&P 500 Banks index). The Government relief efforts index decreases this jump component. Banking and Lockdown index reduce jump volatility in the S&P 500 index and S&P 500 Banks index, but only with a delay of 5 days. These results are consistent with the predictions of our model.

A novel cell culture system modeling the SARS-CoV-2 life cycle.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes the global pandemic of COVID-19. SARS-CoV-2 is classified as a biosafety level-3 (BSL-3) agent, impeding the basic research into its biology and the development of effective antivirals. Here, we developed a biosafety level-2 (BSL-2) cell culture system for production of transcription and replication-competent SARS-CoV-2 virus-like-particles (trVLP). This trVLP expresses a reporter gene (GFP) replacing viral nucleocapsid gene (N), which is required for viral genome packaging and virion assembly (SARS-CoV-2 GFP/ΔN trVLP). The complete viral life cycle can be achieved and exclusively confined in the cells ectopically expressing SARS-CoV or SARS-CoV-2 N proteins, but not MERS-CoV N. Genetic recombination of N supplied in trans into viral genome was not detected, as evidenced by sequence analysis after one-month serial passages in the N-expressing cells. Moreover, intein-mediated protein trans-splicing approach was utilized to split the viral N gene into two independent vectors, and the ligated viral N protein could function in trans to recapitulate entire viral life cycle, further securing the biosafety of this cell culture model. Based on this BSL-2 SARS-CoV-2 cell culture model, we developed a 96-well format high throughput screening for antivirals discovery. We identified salinomycin, tubeimoside I, monensin sodium, lycorine chloride and nigericin sodium as potent antivirals against SARS-CoV-2 infection. Collectively, we developed a convenient and efficient SARS-CoV-2 reverse genetics tool to dissect the virus life cycle under a BSL-2 condition. This powerful tool should accelerate our understanding of SARS-CoV-2 biology and its antiviral development.