Receptor recognition is a major determinant of viral host range, as well as infectivity and pathogenesis. Emergences have been associated with serendipitous events of adaptation upon encounters with a novel host, and the high mutation rate of RNA viruses has been proposed to explain their frequent host shifts 1. SARS-CoV-2 extensive circulation in humans has been associated with the emergence of variants, including variants of concern (VOCs) with diverse mutations in the spike and increased transmissibility or immune escape 2. Here we show that unlike the initial virus, VOCs are able to infect common laboratory mice, replicating to high titers in the lungs. This host range expansion is explained in part by the acquisition of changes at key positions of the receptor binding domain that enable binding to the mouse angiotensin-converting enzyme 2 (ACE2) cellular receptor, although differences between viral lineages suggest that other factors are involved in the capacity of SARS-CoV-2 VOCs to infect mice. This abrogation of the species barrier raises the possibility of wild rodent secondary reservoirs and provides new experimental models to study disease pathophysiology and countermeasures.

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The B1.351 and P.1 variants extend SARS-CoV-2 host range to mice

SARS-CoV-2 proteases Mpro and PLpro are promising targets for antiviral drug development. In this study, we present an antiviral screening strategy involving a novel in-cell protease assay, antiviral and biochemical activity assessments, as well as structural determinations for rapid identification of protease inhibitors with low cytotoxicity. We identified eight compounds with anti-SARS-CoV-2 activity from a library of 64 repurposed drugs and modeled at protease active sites by in silico docking. We demonstrate that Sitagliptin and Daclatasvir inhibit PLpro, and MG-101, Lycorine HCl, and Nelfinavir mesylate inhibit Mpro of SARS-CoV-2. The X-ray crystal structure of Mpro in complex with MG-101 shows a covalent bond formation between the inhibitor and the active site Cys145 residue indicating its mechanism of inhibition is by blocking the substrate binding at the active site. Thus, we provide methods for rapid and effective screening and development of inhibitors for blocking virus polyprotein processing as SARS-CoV-2 antivirals. Additionally, we show that the combined inhibition of Mpro and PLpro is more effective in inhibiting SARS-CoV-2 and the delta variant. 

/pdf/identification-of-sars-cov-2-inhibitors-targeting-mpro-and-5m106ly1.pdf

Identification of SARS-CoV-2 inhibitors targeting Mpro and PLpro using in-cell-protease assay

The coronavirus disease 2019 (COVID-19) has been a global pandemic for more than 2 years and it still impacts our daily lifestyle and quality in unprecedented ways. A better understanding of immunity and its regulation in response to SARS-CoV-2 infection is urgently needed. Based on the current literature, we review here the various virus mutations and the evolving disease manifestations along with the alterations of immune responses with specific focuses on the innate immune response, neutrophil extracellular traps, humoral immunity, and cellular immunity. Different types of vaccines were compared and analyzed based on their unique properties to elicit specific immunity. Various therapeutic strategies such as antibody, anti-viral medications and inflammation control were discussed. We predict that with the available and continuously emerging new technologies, more powerful vaccines and administration schedules, more effective medications and better public health measures, the COVID-19 pandemic will be under control in the near future. 

https://www.nature.com/articles/s41418-022-01015-x.pdf

Immune response in COVID-19: what is next?

Abstract Background During the ongoing Covid-19 pandemic caused by the emerging virus SARS-CoV-2, research in the field of coronaviruses has expanded tremendously. The genome of SARS-CoV-2 has rapidly acquired numerous mutations, giving rise to several Variants of Concern (VOCs) with altered epidemiological, immunological, and pathogenic properties. Methods As cell culture models are important tools to study viruses, we investigated replication kinetics and infectivity of SARS-CoV-2 in the African Green Monkey-derived Vero E6 kidney cell line and the two human cell lines Caco-2, a colon epithelial carcinoma cell line, and the airway epithelial carcinoma cell line Calu-3. We assessed viral RNA copy numbers and infectivity of viral particles in cell culture supernatants at different time points ranging from 2 to 96 h post-infection. Results We here describe a systematic comparison of growth kinetics of the five SARS-CoV-2 VOCs Alpha/B.1.1.7, Beta/B.1.351, Gamma/P.1, Delta/B.1.617.2, and Omicron/B.1.1.529 and a non-VOC/B.1.1 strain on three different cell lines to provide profound information on the differential behaviour of VOCs in different cell lines for researchers worldwide. We show distinct differences in viral replication kinetics of the SARS-CoV-2 non-VOC and five VOCs on the three cell culture models Vero E6, Caco-2, and Calu-3. Conclusion This is the first systematic comparison of all SARS-CoV-2 VOCs on three different cell culture models. This data provides support for researchers worldwide in their experimental design for work on SARS-CoV-2. It is recommended to perform virus isolation and propagation on Vero E6 while infection studies or drug screening and antibody-based assays should rather be conducted on the human cell lines Caco-2 and Calu-3. 

https://virologyj.biomedcentral.com/track/pdf/10.1186/s12985-022-01802-5

Replication kinetics and infectivity of SARS-CoV-2 variants of concern in common cell culture models

https://www.nature.com/articles/s41467-022-32665-7.pdf

Omicron SARS-CoV-2 mutations stabilize spike up-RBD conformation and lead to a non-RBM-binding monoclonal antibody escape

The 501Y.V2 variants contain multiple mutations in the spike region. We found that they had no significant increased effect on infectivity to human cell lines and cells overexpressing human ACE2, but increased infectivity in cells overexpressing mouse ACE2 based on the pseudotyped viruses. The susceptibility of 501Y.V2 variants to many neutralizing monoclonal antibodies decreased significantly. These variants also had a significant reduced effect on the neutralization ability of convalescent and RBD protein immunized sera. The immune resistances were mainly caused by E484K and N501Y mutations located in receptor binding region. These data suggest that the enhancement of infectivity in mouse may lead to the spillover of 501Y.V2 to mouse. The immune resistance of 501Y.V2 may compromise the efficacy of monoclonal antibodies, convalescent sera and vaccines.

Funding: This work was supported by General Program ofNational Natural Science Foundation of China [grant number 82073621], BILL & MELINDA GATES FOUNDATION [Investment ID INV-006379], National Science and Technology Major Projects of Drug Discovery [grant number 2018ZX09101001] and National Science and Technology Major Projects of Infectious Disease [grant number 2017ZX10304402].

Conflict of Interest: All the authors declare no competing interests.

Ethical Approval: The protocol of the animal study was approved by Ethical review Committee for Animal Welfare of The National Institutes for Food and Drug Control.

No Higher Infectivity But Immune Escape of SARS-CoV-2 501Y.V2 Variants

The spike protein of SARS-Cov-2 has been undergoing mutations and is highly glycosylated. It is critically important to investigate the biological significance of these mutations. Here we investigated 80 natural mutants and 26 glycosylation mutants for the infectivity  and reactivity to a panel of neutralizing antibodies and sera from convalescent patients. D614G, along with several double mutations with D614G and another mutation in the same strains, were significantly more infectious, so was N149H, a glycosylation mutant. Most natural mutants within receptor binding domain were less infectious but some became more resistant to neutralizing antibodies. Moreover, the majority of glycosylation mutations were less infectious, revealing the importance of glycosylation for viral infectivity. Interestingly, N234Q was markedly resistant to neutralizing antibodies, whereas N165Q became more sensitive. These findings could be of value in informing our strategy for the development of vaccine and therapeutic antibodies.

Funding: This work was supported by National Science and Technology Major Projects of Drug Discovery [grant number 2018ZX09101001] and National Science and Technology Major Projects of Infectious Disease [grant number 2017ZX10304402].

Conflict of Interest: All authors declare no competing interest.

The Impact of Natural and Glycosylation Mutations in the SARS-CoV-2 Spike Protein on Viral Infectivity and Antigenicity

The invention discloses a fluorescence immunochromatography device for detecting a novel coronavirus COVID-19 and a using method of the fluorescence immunochromatography device. The fluorescence immunochromatography device disclosed by the invention is high in sensitivity and strong in specificity, the accuracy is high, the detection sensitivity can reach 10pg/ml, the detection speed is high, theoperation is simple, the device is portable, the requirement for personnel is low, the operation of professionals is not needed, the detection cost is low, the device can be applied to preliminary screening of various places such as hospitals, airports, customs and disease control centers, the detection time (10-15 min) is short, a simpler, more convenient and faster field detection means is provided for suspected patient investigation and asymptomatic infected person screening, and therefore epidemic spreading is prevented as soon as possible.

Fluorescence immunochromatography device for detecting COVID-19 and using method thereof

The invention discloses a colloidal gold immunochromatography device for detecting a novel coronavirus COVID-19 and a using method thereof. The colloidal gold immunochromatography device disclosed bythe invention is high in sensitivity and strong in specificity, high in accuracy, and the detection sensitivity can reach 100pg/ml; the detection speed is high and the operation is simple; special equipment is not needed, the device is portable,, low in requirement for personnel, free of operation of professionals and low in detection cost, can be applied to preliminary screening of various placessuch as hospitals, airports, customs, communities and families, can judge results within several minutes, and provides a simpler, more convenient and quicker field detection means for suspected patient investigation and asymptomatic infected person screening, so that epidemic diffusion is prevented as soon as possible.

Nie Jianhui

Papers

No Higher Infectivity But Immune Escape of SARS-CoV-2 501Y.V2 Variants

The Impact of Natural and Glycosylation Mutations in the SARS-CoV-2 Spike Protein on Viral Infectivity and Antigenicity

Fluorescence immunochromatography device for detecting COVID-19 and using method thereof

Colloidal gold immunochromatography device for detecting COVID-19 and using method thereof