SARS-CoV-2 NSP12 Protein Is Not an Interferon-ß Antagonist.

The coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is bringing an unprecedented health crisis to the world. To date, our understanding of the interaction between SARS-CoV-2 and host innate immunity is still limited. Previous studies reported that SARS-CoV-2 nonstructural protein 12 (NSP12) was able to suppress interferon-ß (IFN-ß) activation in IFN-ß promoter luciferase reporter assays, which provided insights into the pathogenesis of COVID-19. In this study, we demonstrated that IFN-ß promoter-mediated luciferase activity was reduced during coexpression of NSP12. However, we could show NSP12 did not affect IRF3 or NF-κB activation. Moreover, IFN-ß production induced by Sendai virus (SeV) infection or other stimulus was not affected by NSP12 at mRNA or protein level. Additionally, the type I IFN signaling pathway was not affected by NSP12, as demonstrated by the expression of interferon-stimulated genes (ISGs). Further experiments revealed that different experiment systems, including protein tags and plasmid backbones, could affect the readouts of IFN-ß promoter luciferase assays. In conclusion, unlike as previously reported, our study showed SARS-CoV-2 NSP12 protein is not an IFN-ß antagonist. It also rings the alarm on the general usage of luciferase reporter assays in studying SARS-CoV-2. IMPORTANCE Previous studies investigated the interaction between SARS-CoV-2 viral proteins and interferon signaling and proposed that several SARS-CoV-2 viral proteins, including NSP12, could suppress IFN-ß activation. However, most of these results were generated from IFN-ß promoter luciferase reporter assay and have not been validated functionally. In our study, we found that, although NSP12 could suppress IFN-ß promoter luciferase activity, it showed no inhibitory effect on IFN-ß production or its downstream signaling. Further study revealed that contradictory results could be generated from different experiment systems. On one hand, we demonstrated that SARS-CoV-2 NSP12 could not suppress IFN-ß signaling. On the other hand, our study suggests that caution needs to be taken with the interpretation of SARS-CoV-2-related luciferase assays.

SARS-CoV-2 Antibody Seroprevalence in Wuhan, China, from 23 April to 24 May 2020.

The outbreak of coronavirus disease 2019 (COVID-19) was first reported in Wuhan, China, in December 2019. To investigate the prevalence of COVID-19 in Wuhan, we conducted serologic tests on 35,326 individuals from four different communities to estimate cumulative incidence of infection. Our results showed that 1,332 individuals (3.77%) showed positive COVID-19 antibody (either IgM or IgG). Males had a lower positivity rate than females (3.02% versus 4.52%). The antibody positivity rates showed a clear trend of increase according to patients' ages and varied among different communities. The results indicate that public health interventions may play important roles in the control of COVID-19.IMPORTANCE Coronavirus disease 2019 (COVID-19) was first detected in December 2019 in Wuhan, China. Afterwards, a number of public health interventions were implemented, including lock-down, face mask ordinances, and social distancing. Studies that rely on viral RNA testing of symptomatic patients have shown that these multifaceted interventions contributed to the control of the COVID-19 outbreak in Wuhan and delayed the epidemic's progression. However, these estimates of confirmed cases may miss large numbers of asymptomatic patients and recovered symptomatic patients who were not tested. To investigate the prevalence of COVID-19 in Wuhan, we conducted serologic tests on 35,326 individuals to estimate the cumulative incidence of infection. The results suggest that public health interventions may play important roles in the control of COVID-19.

[Ionization suppression effect of phosphopeptides in nano-electrospray ionization quadrupole time-of-flight mass spectrometry].

Protein phosphorylation is an important post-translational modification (PTM), and involves in many cell activities and disease processes. Nowadays, mass spectrometry (MS) is a powerful tool in peptide-based proteomics. But phosphopeptides, especially multiply phosphorylated peptides, are difficult to be detected by MS. One opinion is that the presence of unphosphorylated peptides lead to the ionization suppression of phosphopeptides. But contrary opinion exists. Moreover, the suppression effect caused by different types of phosphopeptides hasn't been studied yet. In this study, a set of synthetic standard phosphopeptides (singly, doubly and triply phosphorylated peptides) with the same amino acid sequence, and the unphosphorylated peptides were injected into mass spectrometer with or without mixing. Through the ratios of signal intensities of the phosphopeptides before and after mixing, we confirmed that the signals of phosphopeptides were suppressed by those of the unphosphorylated peptides. In addition, the signals of the doubly phosphorylated peptides were slightly suppressed by those of the singly phosphorylated peptides with the same amino acid sequence. The signals of the triply phosphorylated peptides were notably suppressed by the singly and doubly phosphorylated peptides with the same amino acid sequence. Therefore, the singly and multiply phosphorylated peptides should be fractionated and enriched before mass spectrometry analysis.

Photo-switched wettability on an electrostatic self-assembly azobenzene monolayer.

A simple electrostatic self-assembly technique was used to fabricate a photo-switched azobenzene monolayer, on which superhydrophobicity and a large reversible CA change could be realized.