A Review and Perspective of Environmental Disinfection Technology Based on Microwave Irradiation

Purpose of Review In the context of COVID-19 sweeping the world, the development of microbial disinfection methods in gas, liquid, and solid media has received widespread attention from researchers. As a disinfection technology that can adapt to different environmental media, microwave-assisted disinfection has the advantages of strong permeability, no secondary pollution, etc. The purpose of this review is to put forward new development requirements for future microwave disinfection strategies by summarizing current microwave disinfection methods and effects. From the perspective of the interaction mechanism of microwave and microorganisms, this review provides a development direction for more accurate and microscopic disinfection mechanism research. Recent Findings Compared to other traditional environmental disinfection techniques, microwave-assisted disinfection means have the advantages of being more destructive, free of secondary contamination, and thorough. Currently, researchers generally agree that the efficiency of microwave disinfection is the result of a combination of thermal and non-thermal effects. However, the performance of microwave disinfection shows the differences in the face of different environmental media as well as different types of microorganisms. Summary This review highlights the inactivation mechanism of microwave-assisted disinfection techniques used in different scenarios. Suggestions for promoting the efficiency and overcoming the limitations of low energy utilization, complex reactor design, and inaccurate monitoring methods are proposed.

Purification of SARS-CoV-2 RBD in Affinity Chromatography Using a Novel Nanobody Ligand (preprint)

In the spike protein of SARS-CoV-2, the receptor-binding domain (RBD) contains multiple dominant neutralizing epitopes and can be used as an antigen for developing COVID-19 vaccines and neutral antibodies. Affinity chromatography is one of the most extensively used methods for rapid one-step protein purification. However, there is a lack of commercially available affinity ligands for RBD purification. Here, we report the rapid isolation of a nanobody suitable for purifying RBD as an affinity ligand from immune phage display libraries. After bio-panning, the enriched clones were sequenced on next-generation sequencing (NGS) platforms and classified into four groups based on the CDRH3 amino acid sequence. The representative sequences with high nanomolar affinities to RBD were further categorized into two groups via epitope binning analysis. Finally, from the two epitope bins, we found that SS3 showed easy elution under a mild eluting condition and could be used as a functional affinity ligand to purify RBD. These results also indicate that categorizing the bio-panned sequences via high-throughput sequencing (HTS) techniques followed by epitope binning represents a fast workflow to select specific binders with desired properties.

Status of COVID-19 research: an analysis based on articles in the Web of Science database

Against the background of the outbreak of coronavirus disease 2019 (COVID-19) . in order to further understand and clarify the current global status and hotspots of the COVID-19, this paper is based on the Web of Science database to search for this topic. As of April 30, 2020, the SCI literature in the field of SARS-CoV-2 will be subjected to a metrological analysis to discuss the research focus and research status of SARS-CoV-2. This research analyzed the research situation of this research field through the information acquisition, processing and analysis of SARS - CoV - 2 related literature, and the application of bibliometrics methods. Statistical analysis data and visual data analysis results showed that a total of 1, 523 documents had been searched with "COVID - 19" as the subject term;at the current stage of research, China ranked first in the number of articles published in this field;University of London, Harvard University and Huazhong University of Science and Technology were among the top three institutions in the world in terms of publication volume;sorting out high-frequency key words to identify the research hotspots as COVID-19, SARS and public health. It is found that Chinese scholars have achieved rapid development in the field of "COV ID-19", and they are at the forefront of the world in terms of the influence of articles and the amount of articles published.

Multi-omics integrated analysis reveals a specific phenotype of CD8+ T cell may contribute to immunothromosis via Th17 response in severe and critical COVID-19 (preprint)

T lymphocyte reduction and immunosenescence frequently occur in severe and critical coronavirus disease 2019 (COVID-19) patients, which may cause immunothrombosis and numerous sequelae. This study integrated analyzed multi-omics data from healthy donors, pneumonia, COVID-19 patients (mild & moderate, severe, and critical), and convalescences, including clinical, laboratory test, PBMC bulk RNA-seq, PBMC scRNA-seq and TCR-seq, BAL scRNA-seq, and lung proteome. We revealed that there are certain associations among T lymphocyte reduction, CD8+ T cell senescence, Th17 immune activation, and immunothrombosis. A specific phenotype (S. P.) CD8+ T cells were identified in severe and critical COVID-19 patients in both PBMC and BAL scRNA-seq, which showed highly TCR homology with terminal effector CD8+ T cells and senescent CD8+ T cells. Pseudotime analysis showed that the S. P. CD8+ T cells were located in the transition trajectory from mild to severe disease. Which may be activated by terminal effector CD8+ T cells or senescent CD8+ T cells, thereby promoting Th17 cell differentiation. This phenomenon was absent in healthy donors, mild and moderate COVID-19 patients, or convalescences. Our findings are an important reference for avoiding the conversion of patients with mild to severe diseases and provide insight into the future prevention and control of COVID-19 and its variants.

Does Social Capital Help to Reduce Farmland Abandonment? Evidence from Big Survey Data in Rural China

At a time when COVID-19 is sweeping the world, farmland abandonment is obviously not conducive to solving food security problems. Since the formal institutions of local government in China have not been effective in the reduction of farmland abandonment, this study aims to explore whether informal institutions can help mitigate this problem. Based on big survey data from 8031 farmer households in 27 provinces in mainland China, this study uses an econometric model to investigate the quantitative impact of social capital on farmland abandonment, and to analyze the channels through which that impact manifests itself. The empirical results point to the following conclusions: (i) Social capital, as a key informal institution, can help reduce farmland abandonment. More specifically, after controlling for other variables, for every unit increase in social capital, the proportion of farmland abandonment can be predicted to drop by 7.17 percentage points. (ii) Both off-farm employment and farmland rent are channels for the impact of social capital on farmland abandonment. However, social capital’s effect on increasing farmland abandonment via the promotion of off-farm employment is small when compared with its effect on reducing farmland abandonment via the promotion of farmland rent. This study’s conclusions may help generate new ideas for reducing farmland abandonment. At the same time, the study may provide a sound, empirical basis for policies aimed at reducing the negative impact of COVID-19 on food security while also revitalizing rural areas.

Rapid development of SARS-CoV-2 receptor binding domain-conjugated nanoparticle vaccine candidate (preprint)

The ongoing of coronavirus disease 2019 (COVID-19) pandemic caused by novel SARS-CoV-2 coronavirus, resulting in economic losses and seriously threating the human health in worldwide, highlighting the urgent need of a stabilized, easily produced and effective preventive vaccine. The SARS-COV-2 spike protein receptor binding region (RBD) plays an important role in the process of viral binding receptor angiotensin-converting enzyme 2 (ACE2) and membrane fusion, making it an ideal target for vaccine development. In this study, we designed three different RBD-conjugated nanoparticles vaccine candidates, RBD-Ferritin (24-mer), RBD-mi3 (60-mer) and RBD-I53-50 (120-mer), with the application of covalent bond linking by SpyTag-SpyCatcher system. It was demonstrated that the neutralizing capability of sera from mice immunized with three RBD-conjugated nanoparticles adjuvanted with AddaVax or Sigma Systerm Adjuvant (SAS) after each immunization was ~8- to 120-fold greater than monomeric RBD group in SARS-CoV-2 pseudovirus and authentic virus neutralization assay. Most importantly, sera from RBD-conjugated NPs groups more efficiently blocked the binding of RBD to ACE2 or neutralizing antibody in vitro, a further proof of promising immunization effect. Besides, high physical stability and flexibility in assembly consolidated the benefit for rapid scale-up production of vaccine. These results supported that our designed SARS-CoV-2 RBD-conjugated nanoparticle was competitive vaccine candidate and the carrier nanoparticles could be adopted as universal platform for future vaccine development.

COVID-19 risk haplogroups differ between populations, deviate from Neanderthal haplotypes and compromise risk assessment in non-Europeans (preprint)

Recent genome wide association studies (GWAS) have identified genetic risk factors for developing severe COVID-19 symptoms. The studies reported a 1bp insertion rs11385942 on chromosome 3 and furthermore two single nucleotide variants (SNVs) rs35044562 and rs67959919, all three correlated with each other. Zeberg and Paabo subsequently traced them back to Neanderthal origin. They found that a 49.4 kb genomic region including the risk allele of rs35044562 is inherited from Neanderthals of Vindija in Croatia. Here we add a differently focused evaluation of this major genetic risk factor to these recent analyses. We show that (i) COVID-19-related genetic factors of Neanderthals deviate from those of modern humans and that (ii) they differ among world-wide human populations, which compromises risk prediction in non-Europeans. Currently, caution is thus advised in the genetic risk assessment of non-Europeans during this world-wide COVID-19 pandemic.

Computational prediction of SARS-CoV-2 encoded miRNAs and their putative host targets (preprint)

Background: Over the past two decades, there has been a continued research on the role of small non-coding RNAs including microRNAs (miRNAs) in various diseases. Studies have shown that viruses modulate the host cellular machinery and hijack its metabolic and immune signaling pathways by miRNA mediated gene silencing. Given the immensity of coronavirus disease 19 (COVID-19) pandemic and the strong association of viral encoded miRNAs with their pathogenesis, it is important to study Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) miRNAs. Results: To address this unexplored area, we identified 8 putative novel miRNAs from SARS-CoV-2 genome and explored their possible human gene targets. A significant proportion of these targets populated key immune and metabolic pathways such as MAPK signaling pathway, maturity-onset diabetes of the young, Insulin signaling pathway, endocytosis, RNA transport, TGF-{beta} signaling pathway, to name a few. The data from this work is backed up by recently reported high-throughput transcriptomics datasets obtains from SARS-CoV-2 infected samples. Analysis of these datasets reveal that a significant proportion of the target human genes were down-regulated upon SARS-CoV-2 infection. Conclusions: The current study brings to light probable host metabolic and immune pathways susceptible to viral miRNA mediated silencing in a SARS-CoV-2 infection, and discusses its effects on the host pathophysiology.

Antiviral activity of plant juices and green tea against SARS-CoV-2 and influenza virus in vitro (preprint)

Respiratory viruses initially infect the naso- and oropharyngeal regions, where they amplify, cause symptoms and may also be transmitted to new hosts. Preventing initial infection or reducing viral loads upon infection might soothe symptoms, prevent dissemination into the lower airways, or transmission to the next individual. We here analyzed the potential of plant derived products to inactivate SARS-CoV-2 and influenza virus. We found that black chokeberry (Aronia melanocarpa) juice, pomegranate (Punica granatum) juice, and green tea (Camellia sinensis) have virucidal activity against both viruses, suggesting that oral rinsing may reduce viral loads in the oral cavity thereby lowering virus transmission.

Potential Opportunity Of Antisense Therapy Of COVID-19 on an in vitro model (preprint)

Data on potential effectiveness and prospects of treatment of new coronavirus infection of COVID-19 caused by virus SARS-CoV-2 with the help of antisense oligonucleotides acting against RNA of virus on an in vitro model are given. The ability of antisense oligonucleotides to suppress viral replication in diseases caused by coronaviruses using the example of SARS and MERS is shown. The identity of the initial regulatory section of RNA of various coronaviruses was found within 50 - 100 nucleotides from the 5'-end, which allows using antisense suppression of this RNA fragment. A new RNA fragment of the virus present in all samples of coronovirus SARS-CoV-2 has been identified, the suppression of which with the help of an antisense oligonucleotide can be effective in the treatment of COVID-19. The study of the synthesized antisense oligonucleotide 5`-AGCCGAGTGACAGCC ACACAG, complementary to the selected virus RNA sequence, was carried out. The low toxicity of the preparations of this group in the cell culture study and the ability to reduce viral load at high doses according to real time-PCR data are shown. The cytopathogenic dose exceeds 2 mg/ml. At a dosage of 1 mg/ml, viral replication is reduced by 5 - 13 times. Conclusions are made about the prospects of this direction and the feasibility of using the inhalation way of drug administration into the body.

Modelling the active SARS-CoV-2 helicase complex as a basis for structure-based inhibitor design (preprint)

Having claimed over 1 million lives worldwide to date, the ongoing COVID-19 pandemic has created one of the biggest challenges to develop an effective drug to treat infected patients. Among all the proteins expressed by the virus, RNA helicase is a fundamental protein for viral replication, and it is highly conserved among the coronaviridae family. To date, there is no high-resolution structure of helicase bound with ATP and RNA. We present here structural insights and molecular dynamics (MD) simulation results of the SARS-CoV-2 RNA helicase both in its apo form and in complex with its natural substrates. Our structural information of the catalytically competent helicase complex provides valuable insights for the mechanism and function of this enzyme at the atomic level, a key to develop specific inhibitors for this potential COVID-19 drug target.

Blocking antibodies against SARS-CoV-2 RBD isolated from a phage display antibody library using a competitive biopanning strategy (preprint)

The infection of the novel coronavirus SARS-CoV-2 have caused more than 150,000 deaths, but no vaccine or specific therapeutic antibody is currently available. SARS-CoV-2 relies on its spike protein, in particular the receptor binding domain (RBD), to bind human cell receptor angiotensin-converting enzyme 2 (ACE2) for viral entry, and thus targeting RBD holds the promise for preventing SARS-CoV-2 infection. In this work, a competitive biopanning strategy of a phage display antibody library was applied to screen blocking antibodies against RBD. High-affinity antibodies were enriched after the first round using a standard panning process in which RBD-His recombinant protein was immobilized as a bait. At the next two rounds, immobilized ACE2-Fc and free RBD-His proteins were mixed with the enriched phage antibodies. Antibodies binding to RBD at epitopes different from ACE2-binding site were captured by the immobilized ACE2-Fc, forming a "sandwich" complex. Only antibodies competed with ACE2 for recognizing RBD at the same or similar epitopes can bind to the free RBD-His in the supernatant and be subsequently separated by the Ni-NTA magnetic beads. Top 1 lead from the competitive biopanning of a synthetic antibody library, Lib AB1, was produced as the full-length IgG1 format. It was proved to competitively block the binding of RBD to ACE2 protein, and potently inhibit SARS-CoV-2 pseudovirus infection of ACE2-overexpressing Hela cells with IC50 values of 12nM. Nevertheless, top 1 lead from the standard biopanning of Lib AB1, can only bind to RBD in vitro but not have the blocking or neutralization activity. Our strategy can efficiently isolate the blocking antibodies of RBD, and it would speed up the discovery of neutralizing antibodies against SARS-CoV-2.