Preference Characteristics on Consumers’ Online Consumption of Fresh Agricultural Products under the Outbreak of COVID-19: An Analysis of Online Review Data Based on LDA Model

Since the outbreak of the COVID-19 pandemic in 2020, China has adopted a zero-clearing policy under closed control. It is rather common for residents who are quarantined at home to buy fresh agricultural products online, when COVID-19 spread in big cities. Many e-commerce platforms are trying to develop online shopping channels for fresh agricultural products. However, negative comments and news about those platforms have been increasing because of several reasons, such as the difference in the quality of fresh products, inadequate categories of commodity and inefficient delivery caused by the shortage of personnel and so on. The smooth daily supply of online fresh agricultural products is conducive to soothing the pessimistic emotions and to encouraging their active obedience to epidemic prevention and control policy. Therefore, it is of great importance to explore the preference characteristics of consumers’ online purchase of fresh agricultural products under this critical situation. In this paper, firstly, Pycharm software is used to collect online comment texts of fresh agricultural products on the online platforms with a total of 34,546 pieces of evaluation data. Secondly, the collected data is preformed into the text preprocessing. To be specific, the obtained online comments are processed by Python, including the process of text duplication between sentences, text duplication within sentences and short sentence filtering. After that, processed texts are subjected to Jieba Text Segmentation to form the final word frequency ranking, involving two procedures, part-of-speech tagging and stop-words removal. Lastly, the results of the LDA model indicate the factors that influence consumers’ preferences when they purchase fresh agricultural products online. This study could not only identify the typical features of residents’ online shopping preference in the context of the spread of COVID-19, but also provide pragmatic suggestions for the local government to appease the residents’ negative emotions for the prevention of widespread complaints at the social level.

Structural Study of SARS-CoV-2 Antibodies Identifies a Broad-Spectrum Antibody That Neutralizes the Omicron Variant by Disassembling the Spike Trimer.

The continuous emergence of novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants poses new challenges in the fight against the coronavirus disease 2019 (COVID-19) pandemic. The newly emerging Omicron strain caused serious immune escape and raised unprecedented concern all over the world. The development of an antibody targeting a conserved and universal epitope is urgently needed. A subset of neutralizing antibodies (NAbs) against COVID-19 from convalescent patients were isolated in our previous study. In this study, we investigated the accommodation of these NAbs to SARS-CoV-2 variants of concern (VOCs), revealing that IgG 553-49 neutralizes pseudovirus of the SARS-CoV-2 Omicron variant. In addition, we determined the cryo-electron microscopy (cryo-EM) structure of the SARS-CoV-2 spike (S) protein complexed with three monoclonal antibodies targeting different epitopes, including 553-49, 553-15, and 553-60. Notably, 553-49 targets a novel conserved epitope and neutralizes the virus by disassembling S trimers. IgG 553-15, an antibody that neutralizes all of the VOCs except Omicron, cross-links two S trimers to form a trimer dimer, demonstrating that 553-15 neutralizes the virus by steric hindrance and virion aggregation. These findings suggest the potential to develop 553-49 and other antibodies targeting this highly conserved epitope as promising therapeutic reagents for COVID-19. IMPORTANCE The emergence of the Omicron strain of SARS-CoV-2 caused higher immune escape, raising unprecedented concerns about the effectiveness of antibody therapies and vaccines. In this study, we identified a SARS-CoV-2 neutralizing antibody, 553-49, which neutralizes all variants by targeting a completely conserved novel epitope. In addition, we revealed that IgG 553-15 neutralizes SARS-CoV-2 by cross-linking virions and that 553-60 functions by blocking receptor binding. Comparison of different receptor binding domain (RBD) epitopes revealed that the 553-49 epitope is hidden in the S trimer and keeps a high degree of conservation during SARS-CoV-2 evolution, making 553-49 a promising therapeutic reagent against the emerging Omicron and future variants of SARS-CoV-2.

The prominent role of a CDR1 somatic hypermutation for convergent IGHV3-53/3-66 antibodies in binding to SARS-CoV-2.

In the fight against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), monoclonal antibodies (mAbs) serve as key strategies for the rapid prevention and treatment of COVID-19. However, analysis to fully characterize functional SARS-CoV-2 mAbs is still needed. In this study, by interrogating 1,695 published or patented mAbs of human origin and validated SARS-CoV-2-binding potency, we found a highly preferential usage of IGHV3-53/3-66 germline genes that was then revealed as a distinct selectivity of SARS-CoV-2-induced humoral immunity across other coronaviruses. Moreover, among the rare somatic hypermutations, we identified a novel mutation signature of F27 to I, L, or V with high frequency, which was located in the CDR1 region of the heavy chain among IGHV3-53/3-66-encoded antibodies. This convergent mutation contributed to improving SARS-CoV-2 binding affinity and may advance our knowledge of the humoral immunity to SARS-CoV-2.

A non-ACE2 competing human single-domain antibody confers broad neutralization against SARS-CoV-2 and circulating variants.

The current COVID-19 pandemic has heavily burdened the global public health system and may keep simmering for years. The frequent emergence of immune escape variants have spurred the search for prophylactic vaccines and therapeutic antibodies that confer broad protection against SARS-CoV-2 variants. Here we show that the bivalency of an affinity maturated fully human single-domain antibody (n3113.1-Fc) exhibits exquisite neutralizing potency against SARS-CoV-2 pseudovirus, and confers effective prophylactic and therapeutic protection against authentic SARS-CoV-2 in the host cell receptor angiotensin-converting enzyme 2 (ACE2) humanized mice. The crystal structure of n3113 in complex with the receptor-binding domain (RBD) of SARS-CoV-2, combined with the cryo-EM structures of n3113 and spike ecto-domain, reveals that n3113 binds to the side surface of up-state RBD with no competition with ACE2. The binding of n3113 to this novel epitope stabilizes spike in up-state conformations but inhibits SARS-CoV-2 S mediated membrane fusion, expanding our recognition of neutralization by antibodies against SARS-CoV-2. Binding assay and pseudovirus neutralization assay show no evasion of recently prevalent SARS-CoV-2 lineages, including Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), and Delta (B.1.617.2) for n3113.1-Fc with Y58L mutation, demonstrating the potential of n3113.1-Fc (Y58L) as a promising candidate for clinical development to treat COVID-19.

Insights into biological therapeutic strategies for COVID-19

The worldwide pandemic of novel coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that emerged in late December 2019 requires the urgent development of therapeutic options. So far, numerous studies have investigated and uncovered the underlying epidemiology and clinical characteristics of COVID-19 infections in order to develop effective drugs. Compared with antiviral small-molecule inhibitors, biotherapeutics have unique advantages such as few side effects by virtue of their high specificity, and thus can be rapidly developed for promising treatments of COVID-19. Here, we summarize potential biotherapeutics and their mechanisms of action, including convalescent plasma, therapeutic antibodies, peptides, engineered ACE2, interferons, cytokine inhibitors, and RNAi-based therapeutics, and discuss in depth the advancements and precautions for each type of biotherapeutics in the treatment of COVID-19.

Deep Mining of Human Antibody Repertoires: Concepts, Methodologies, and Applications

The ability of the human adaptive immune system to respond to antigens relies upon the tremendous diversity of T cell receptors (TCR) and B cell receptors (BCR). The entirety of an individual's BCRs, often referred to as an antibody repertoire, shapes the humoral immune system. Therefore, technologies to identify and characterize antibody repertoires are critical for understanding fundamental aspects of the development and maintenance of the humoral immune system. Recently, innovative methodologies and technologies devoted to high-throughput sequencing of antibody repertoires (Ig-Seq) have broadened the understanding of humoral immunity. This review provides an overview of the Ig-Seq pipeline from sample collection, library preparation, and sequencing, to data cleaning, sequence alignment, and high-level processing. Conventional and current strategies used in Ig-Seq are introduced in detail, including bulk BCR sequencing, heavy and light chain paired sequencing combined with proteomic or single B cell sequencing approaches, antigen-specific single B cell sequencing, and single-molecule sequencing. Applications of Ig-Seq are also discussed, including antibody diversity measurement, signatures associated with different populations, novel findings involved in the antibody repertoire development, and strategies of functional antibody discovery from antibody repertoires. Finally, the pitfalls and opportunities in the deep mining of antibody repertoires are discussed.

Potent binding of 2019 novel coronavirus spike protein by a SARS coronavirus-specific human monoclonal antibody.

The newly identified 2019 novel coronavirus (2019-nCoV) has caused more than 11,900 laboratory-confirmed human infections, including 259 deaths, posing a serious threat to human health. Currently, however, there is no specific antiviral treatment or vaccine. Considering the relatively high identity of receptor-binding domain (RBD) in 2019-nCoV and SARS-CoV, it is urgent to assess the cross-reactivity of anti-SARS CoV antibodies with 2019-nCoV spike protein, which could have important implications for rapid development of vaccines and therapeutic antibodies against 2019-nCoV. Here, we report for the first time that a SARS-CoV-specific human monoclonal antibody, CR3022, could bind potently with 2019-nCoV RBD (KD of 6.3 nM). The epitope of CR3022 does not overlap with the ACE2 binding site within 2019-nCoV RBD. These results suggest that CR3022 may have the potential to be developed as candidate therapeutics, alone or in combination with other neutralizing antibodies, for the prevention and treatment of 2019-nCoV infections. Interestingly, some of the most potent SARS-CoV-specific neutralizing antibodies (e.g. m396, CR3014) that target the ACE2 binding site of SARS-CoV failed to bind 2019-nCoV spike protein, implying that the difference in the RBD of SARS-CoV and 2019-nCoV has a critical impact for the cross-reactivity of neutralizing antibodies, and that it is still necessary to develop novel monoclonal antibodies that could bind specifically to 2019-nCoV RBD.