The pandemic of COVID-19 caused by SARS-CoV-2 has posed serious threats to global health and economy, thus calling for the development of safe and effective vaccines. The receptor-binding domain (RBD) in the spike protein of SARS-CoV-2 is responsible for its binding to ACE2 receptor. It contains multiple dominant neutralizing epitopes and serves as an important antigen for the development of COVID-19 vaccines. Here, we showed that immunization of mice with a candidate subunit vaccine consisting of SARS-CoV-2 RBD and Fc fragment of human IgG, as an immunopotentiator, elicited high titer of RBD-speci c antibodies with robust neutralizing activity against both pseudotyped and live SARS-CoV-2 infections. The mouse antisera could also effectively neutralize infection by pseudotyped SARS-CoV-2 with several natural mutations in RBD and the IgG extracted from the mouse antisera could also show neutralization against pseudotyped SARS-CoV and SARS-related coronavirus (SARSr-CoV). Vaccination of human ACE2 transgenic mice with RBD-Fc could effectively protect mice from the SARS-CoV-2 challenge. These results suggest that SARS-CoV-2 RBD-Fc has good potential to be further developed as an effective and broad-spectrum vaccine to prevent infection of the current SARS-CoV-2 and its mutants, as well as future emerging SARSr-CoVs and re-emerging SARS-CoV. Background The outbreaks of severe acute respiratory syndrome (SARS) caused by SARS coronavirus (SARS-CoV) in 2002/2003 and those of middle east respiratory syndrome (MERS) caused by MERS coronavirus (MERS-CoV) in 2012 have highlighted the high zoonotic potential of emerging coronaviruses 1, 2. The pandemic of coronavirus disease 2019 (COVID-19) caused by the novel coronavirus 2019 (2019-nCoV) 3 , which was also denoted as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) 4 , or human coronavirus 2019 (HCoV-19) 5 , has resulted in more than 17 million con rmed cases and 0.66 million deaths in 216 countries, areas or territories (https://www.who.int/), endangering the global public health and economy and thus calling for the development of effective vaccines to protect at-risk populations. Currently, more than 150 COVID-19 vaccines are under development at different stages 6-9. Especially, a number of COVID-19 vaccines' phase 1/2 clinical trials have been completed, including the adenovirusvectored vaccines (Ad5-nCoV and ChAdOx1 nCoV-19) from CanSino 10 and Oxford University/AstraZeneca 11 , respectively; the mRNA vaccines (mRNA-1273 and BNT162b1) from Moderna 12 and P zer/BioNTech 13 , respectively; and the inactivated vaccines (PiCoVacc and BBIBP-CorV) from Sinovac 14 and Beijing Institute of Biological Products 15 , respectively (https://biorender.com/covid-vaccine-tracker/). Generally speaking, all these vaccines could induce antibodies speci c for spike (S) protein and receptor-binding domain (RBD), which neutralized pseudotyped and live SARS-CoV-2 infection. Some reports have shown that the neutralizing antibody titers are strongly correlated with RBD-binding IgG ...

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused huge social and economic distress. Given its rapid spread and the lack of specific treatment options, SARS-CoV-2 needs to be inactivated according to strict biosafety measures during laboratory diagnostics and vaccine development. The inactivation method for SARS-CoV-2 affects research related to the natural virus and its immune activity as an antigen in vaccines. In this study, we used size exclusion chromatography, western blotting, ELISA, an electron microscope, dynamic light scattering, circular dichroism, and surface plasmon resonance to evaluate the effects of four different chemical inactivation methods on the physical and biochemical characterization of SARS-CoV-2. Formaldehyde and β-propiolactone (BPL) treatment can completely inactivate the virus and have no significant effects on the morphology of the virus. None of the four tested inactivation methods affected the secondary structure of the virus, including the α-helix, antiparallel β-sheet, parallel β-sheet, β-turn, and random coil. However, formaldehyde and long-term BPL treatment (48 h) resulted in decreased viral S protein content and increased viral particle aggregation, respectively. The BPL treatment for 24 h can completely inactivate SARS-CoV-2 with the maximum retention of the morphology, physical properties, and the biochemical properties of the potential antigens of the virus. In summary, we have established a characterization system for the comprehensive evaluation of virus inactivation technology, which has important guiding significance for the development of vaccines against SARS-CoV-2 variants and research on natural SARS-CoV-2.

Cell detachment techniques using animal-derived enzymes are necessary for the production of biopharmaceuticals that are made with the help of adherent cell cultures, although the majority of protein therapeutics (>USD 100 billion of income per year) are made under suspension cultures that do not require animal-derived proteins for manufacture. In this study, we establish the optimal Vero cell detachment process, and analyze physiological changes during cell detachment at the cellular and molecular levels. Using flow cytometry, we find that animal-based enzymes are more likely to induce apoptosis than animal-origin-free enzymes. We analyze the levels of RNAs, proteins, and metabolites in cells treated with two detachment strategies, and identify 1237 differentially expressed genes, 2883 differential proteins, and 210 differential metabolites. Transcriptomic analysis shows that animal-origin-free enzymes have a less significant effect on gene expression levels. Combined with proteomic analysis, animal-based enzymes affect the oxidative phosphorylation process and reduce the mRNA and protein levels of Cytochrome C Oxidase Assembly Protein 17 (COX17), which is a Cytochrome C Oxidase Copper Chaperone involved in the mitochondrial respiratory chain. Metabolomics analysis indicates that the levels of spermine and spermidine, which are involved in the glutathione metabolism pathway and apoptosis inhibition, are significantly reduced. Therefore, COX17, spermine, and spermidine may be biomarkers for evaluating the cell subculture process. In conclusion, we have deeply characterized the cell subculture process through multi-omics, which may provide important guidance for research and process evaluation to optimize cell detachment processes.

Bioreactors are one of the most important, basic pieces of equipment in the biopharmaceutical industry. Understanding the effects of mechanical damage and other factors on the physiological state of cells during cell matrix culture is the basis for continuously achieving greater efficiency and higher product quality. In this study, Vero cells were used as a model and apoptosis, senescence, transcriptomics, proteomics, and metabolomics were carried out for analysis at the cellular and molecular levels. The results showed that compared with cells cultured in the simulated natural state, the cells cultured in the basket bioreactor displayed no obvious senescence. Additionally, the proportion of early apoptotic cells increased, but the proportions of damaged, late apoptotic and dead cells did not change significantly. The transcription levels of aminoacyl-tRNA synthetase and cyclin D1 and the expression levels of DNA replication licensing factor, methenyltetrahydrofolate cyclohydrolase, arachidonic acid and other metabolites of cells cultured in the basket bioreactor were significantly increased. These results suggest that DNA replication, protein translation and the metabolic activities in cells cultured in basket bioreactors are more active, which is more conducive to cell amplification and target product production. In this study, the growth and physiological state of cells in a basket bioreactor were characterized at the molecular level for the first time. Additionally, a tool to evaluate the physiological state of cells in a bioreactor was established, which can be used to guide the development and optimization of cell matrix culture conditions in industrial production and improve the production efficiency of the target products.

Since the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in late 2019, the virus has been mutating continuously, resulting in the continuous emergence of variants and creating challenges for epidemic prevention and control. Here, we immunized mice with different vaccine candidates, revealing the immune, protein, and metabolomic changes that take place in vaccines composed of different variants. We found that the prototype strain and Delta- and Omicron-variant inactivated vaccine candidates could all induce a high level of neutralizing antibodies and cellular immunity responses in mice. Next, we found that the metabolic and protein profiles were changed, showing a positive association with immune responses, and the level of the change was distinct in different inactivated vaccines, indicating that amino acid variations could affect metabolomics and proteomics. Our findings reveal differences between vaccines at the metabolomic and proteomic levels. These insights provide a novel direction for the immune evaluation of vaccines and could be used to guide novel strategies for vaccine design.