Defining the single base importance of human mRNAs and lncRNAs (preprint)

As the fundamental unit of a gene and its transcripts, nucleotides have enormous impacts on molecular function and evolution, and thus on phenotypes and diseases. Given that different nucleotides on one gene often exhibit diverse levels of effects, it is quite crucial to comprehensively and quantitatively measure the importance of each base on a gene transcript, however, tools are still not available. Here we proposed Base Importance Calculator (BIC), an algorithm to calculate the importance score of single bases based on sequence information of human mRNAs and long noncoding RNAs (lncRNAs). We then confirmed its power by applying BIC to three different tasks. Firstly, we revealed that BIC can effectively evaluate the pathogenicity of both genes and single bases by analyzing the BIC scores and the pathogenicity of single nucleotide variations (SNVs). Moreover, the BIC score in the Cancer Genome Atlas (TCGA) somatic mutations is able to predict the prognosis of some cancers. Finally, we show that BIC can also precisely predict the transmissibility of SARS-CoV-2. The above results indicate that BIC is a useful tool for evaluating the single base important of human mRNAs and lncRNAs.

Cryoelectron microscopy structures of a human neutralizing antibody bound to MERS-CoV spike glycoprotein

Neutralizing monoclonal antibodies (mAbs) against highly pathogenic coronaviruses represent promising candidates for clinical intervention. Here, we isolated a potent neutralizing monoclonal antibody, MERS-S41, from a yeast displayed scFv library using the S protein as a bait. To uncover the neutralization mechanism, we determined structures of MERS-S41 Fab in complex with the trimeric spike glycoprotein by cryoelectron microscopy (cryo-EM). We observed four distinct classes of the complex structure, which showed that the MERS-S41 Fab bound to the “up” receptor binding domain (RBD) with full saturation and also bound to an accessible partially lifted “down” RBD, providing a structural basis for understanding how mAbs bind to trimeric spike glycoproteins. Structure analysis of the epitope and cell surface staining assays demonstrated that virus entry is blocked predominantly by direct competition with the host receptor, dipeptidyl peptidase-4 (DPP4).

Modeling COVID-19 vaccine-induced immunological memory development and its links to antibody level and infectiousness (preprint)

COVID-19 vaccines have proven to be effective against SARS-CoV-2 infection. However, the dynamics of vaccine-induced immunological memory development and neutralizing antibodies generation are not fully understood, limiting vaccine development and vaccination regimen determination. Herein, we constructed a mathematical model to characterize the vaccine-induced immune response based on fitting the viral infection and vaccination datasets. With the example of CoronaVac, we revealed the association between vaccine-induced immunological memory development and neutralizing antibody levels. The establishment of the intact immunological memory requires more than 6 months after the first and second doses, after that a booster shot can induce high levels neutralizing antibodies. By introducing the maximum viral load and recovery time after viral infection, we quantitatively studied the protective effect of vaccines against viral infection. Accordingly, we optimized the vaccination regimen, including dose and vaccination timing, and predicted the effect of the fourth dose. Last, by combining the viral transmission model, we showed the suppression of virus transmission by vaccination, which may be instructive for the development of public health policies.

Label‐Free Cell Viability Assay and Enrichment of Cryopreserved Cells Using Microfluidic Cytometry and On‐Demand Sorting

Cryopreservation is essential for the long‐term storage of primary cell samples and enables accessing primary cells anytime via a simple thawing process. However, low viability and cell fragmentation are the major issues for cryopreserved cell samples due to the toxicity of cryoprotective agents and crystallization of intracellular contents during cooling at low temperature. Human peripheral blood mononuclear cells (PBMCs) in high viability are critical for pathophysiological and therapeutic research of infectious diseases, especially for the current worldwide pandemic of coronavirus disease 2019. Conventional viability enrichment techniques for primary PBMC samples provoke either cryoinjury caused by cell sorting mechanism or substantial cell loss due to multiple sample preparation steps. Here, a label‐free viability assessment and on‐demand enrichment system for cryopreserved primary human PBMCs with validation by fluorescent label‐based flow cytometry, is demonstrated. It can provide consistent viability assays by discriminating viable PBMCs from apoptotic, DMSO toxicity‐induced dead cells and cell debris, and deliver over 90% viability of sorted samples in one step after thawing. This integrated cell viability assay and on‐demand enrichment of viable cells has broad applications in diverse cellular biology research and cell‐related biomedical diagnostics. [ABSTRACT FROM AUTHOR] Copyright of Advanced Materials Technologies is the property of John Wiley & Sons, Inc. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dynamics of SARS-CoV-2 and host immunity in infection and vaccine protection (preprint)

Once challenged by the SARS-CoV-2 virus, the human host immune system triggers a dynamic process against infection. We constructed a simplistic mathematical model to describe host innate and adaptive immune response to viral challenge. Based on the dynamic properties of viral load and immune response, we classified the resulting dynamics into four modes, corresponding to the increasing severity of COVID-19 disease. We found immune efficacy against viral attack, clearance of infected cells, and IL-6 levels to be prognostic determinants, especially for severe and critical patients. We also investigated vaccine-induced protection against SARS-CoV-2 infection. Results strongly suggested that immune efficacy based on memory T cells, as well as neutralizing antibody titers, could be true indicators of vaccine protection rates. Finally, we analyzed infection dynamics of SARS-CoV-2 variants within the construct of our mathematical model. Overall, our results provide a systematic framework for understanding the dynamics of host response upon challenge by SARS-CoV-2 infection, and this framework can be used to predict vaccine protection and perform clinical diagnosis.

Model-based cellular kinetic analysis of SARS-CoV-2 infection: different immune response modes and treatment strategies (preprint)

Increasing number in global COVID-19 cases demands for mathematical model to analyze the interaction between the virus dynamics and the response of innate and adaptive immunity. Here, based on the assumption of a weak and delayed response of the innate and adaptive immunity in SARS-CoV-2 infection, we constructed a mathematical model to describe the dynamic processes of immune system. Integrating theoretical results with clinical COVID-19 patients data, we classified the COVID-19 development processes into three typical modes of immune responses, correlated with the clinical classification of mild & moderate, severe and critical patients. We found that the immune efficacy (the ability of host to clear virus and kill infected cells) and the lymphocyte supply (the abundance and pool of naive T and B cell) play important roles in the dynamic process and determine the clinical outcome, especially for the severe and critical patients. Furthermore, we put forward possible treatment strategies for the three typical modes of immune response. We hope our results can help to understand the dynamical mechanism of the immune response against SARS-CoV-2 infection, and to be useful for the treatment strategies and vaccine design.

Model-based cellular kinetic analysis of SARS-CoV-2 infection: different immune response modes and treatment strategies (preprint)

Increasing number in global COVID-19 cases demands for mathematical model to analyze the interaction between the virus dynamics and the response of innate and adaptive immunity. Here, based on the assumption of a weak and delayed response of the innate and adaptive immunity in SARS-CoV-2 infection, we constructed a mathematical model to describe the dynamic processes of immune system. Integrating theoretical results with clinical COVID-19 patients' data, we classified the COVID-19 development processes into three typical modes of immune responses, correlated with the clinical classification of mild & moderate, severe and critical patients. We found that the immune efficacy (the ability of host to clear virus and kill infected cells) and the lymphocyte supply (the abundance and pool of na\"ive T and B cell) play important roles in the dynamic process and determine the clinical outcome, especially for the severe and critical patients. Furthermore, we put forward possible treatment strategies for the three typical modes of immune response. We hope our results can help to understand the dynamical mechanism of the immune response against SARS-CoV-2 infection, and to be useful for the treatment strategies and vaccine design.

Clinical findings in critical ill patients infected with SARS-Cov-2 in Guangdong Province, China: a multi-center, retrospective, observational study (preprint)

Abstract Background In December 2019, human infection with a novel coronavirus, known as SARS-CoV-2, was identified in Wuhan, China. The mortality of critical illness was high in Wuhan. Information about critically ill patients with SARS-CoV-2 infection outside of Wuhan is scarce. We aimed to provide the clinical features, treatment, and prognosis of the critically ill patients with SARS-CoV-2 infection in Guangdong Province. Methods In this multi-centered, retrospective, observational study, we enrolled critically ill patients with SARS-CoV-2 pneumonia who were admitted to the intensive care unit (ICU) in Guangdong Province. Demographic data, symptoms, laboratory findings, comorbidities, treatments, and prognosis were collected. Data were compared between patients with and without intubation. Results Forty-five critically ill patients with SARS-CoV-2 pneumonia were identified in 7 ICUs in Guangdong Province. The mean age was 56.7 years, and 29 patients (64.4%) were men. The most common symptoms at the onset of illness were high fever and cough. Majority of patients presented with lymphopenia and elevated lactate dehydrogenase. Treatment with antiviral drugs was initiated in all the patients. Thirty-seven patients (82.2%) had developed acute respiratory distress syndrome, and 13 (28.9%) septic shock. A total of 20 (44.4%) patients required intubation and 9 (20%) required extracorporeal membrane oxygenation. As of February 28th 2020, only one patient (2.2%) had died and half of them had discharged of ICU. Conclusions Infection with SARS-CoV-2 in critical illness is characterized by fever, lymphopenia, acute respiratory failure and multiple organ dysfunction. Compared with critically ill patients infected with SARS-CoV-2 in Wuhan, the mortality of critically ill patients in Guangdong Province was relatively low. These data provide some general understandings and experience for the critical patients with SARS-CoV-2 outside of Wuhan.