Biology subjects

Chao, T.-L.

Publications and source records attributed to Chao, T.-L..

6 recordsLinked to original sources

bioRxiv2024

A robust platform for BaEVRless-lentiviral synthesis and primary natural killer cell transduction

Lentiviral vectors are invaluable tools for genetic modification in human cells for research, biotechnological and clinical applications. However, certain cell types, such as primary human natural killer (NK) cells, present challenges in lentiviral transduction. Overcoming this limitation requires specific pseudotype modifications. BaEVRless-pseudotyped lentivirus (BaEVRless-LV) has shown promise in efficiently transducing human NK cells, B cells, and hematopoietic stem cells (HSCs). BaEVRless, a modified envelope protein derived from Baboon endogenous retrovirus, targets ASCT receptors in human cells. While effective for several immune cell types, BaEVRless-LV production in standard HEK293T cells is challenging. During lentiviral synthesis, BaEVRless protein induces hyper cell fusion, leading to rapid HEK293T cell death and reduced BaEVRless-LV titers. To solve this problem, we used CRISPR genome editing to knockout (KO) the ASCT2 gene in HEK293T cells, thereby abolishing BaEVRless-induced cell fusion. Using the ASCT2-KO cells and an optimized viral production protocol, we efficiently packaged high titers of BaEVRless-LV encoding various transgenes, including turbogfp, chimeric antigen receptor (CAR), and a pooled CRISPR sgRNA library. Our robust BaEVRless-LV synthesis platform is readily adaptable for manufacturing cell therapeutics and enables advanced research techniques such as CRISPR genetic screens in primary NK cells.

immunology↗

bioRxiv2023

Antagonistic pleiotropy plays an important role in governing the evolution and genetic diversity of SARS-CoV-2

Analyses of the genomic diversity of SARS-CoV-2 found that some sites across the genome appear to have mutated independently multiple times with frequency significantly higher than four-fold sites, which can be either due to mutational bias, i.e., elevated mutation rate in some sites of the genome, or selection of the variants due to antagonistic pleiotropy, a condition where mutations increase some components of fitness at a cost to others. To examine how different forces shaped evolution of SARS-CoV-2 in 2020-2021, we analyzed a large set of genome sequences (~ 2 million). Here we show that while evolution of SARS-CoV-2 during the pandemic was largely mutation-driven, a group of nonsynonymous changes is probably maintained by antagonistic pleiotropy. To test this hypothesis, we studied the function of one such mutation, spike M1237I. Spike I1237 increases viral assembly and secretion, but decreases efficiency of transmission in vitro. Therefore, while the frequency of spike M1237I may increase within hosts, viruses carrying this mutation would be outcompeted at the population level. We also discuss how the antagonistic pleiotropy might facilitate positive epistasis to promote virus adaptation and reconcile discordant estimates of SARS-CoV-2 transmission bottleneck sizes in previous studies.

evolutionary biology↗

bioRxiv2022

Equilibrative Nucleoside Transporter 3 is an IFN-stimulated Gene that Facilitates Viral Genome Release

An increasing body of evidence emphasizes the role of metabolic reprogramming in immune cells to fight off infections. However, little is known about the regulation of metabolite transporters that facilitate and support metabolic demands. In this study, we found that equilibrative nucleoside transporter 3 (ENT3) expression is part of the innate immune response, and is rapidly upregulated upon bacterial and viral infection. The transcription of ENT3 is directly under the regulation of IFN-induced signaling, positioning this metabolite transporter as an Interferon-stimulated gene (ISG). Moreover, we unveil that several viruses, including SARS-CoV2, require ENT3 to facilitate their entry into the cytoplasm. The removal or suppression of ENT3 expression is sufficient to significantly decrease viral replication in vitro and in vivo.

immunology↗

bioRxiv2021

Impact of Glycosylation on SARS-CoV-2 Infection and Broadly Protective Vaccine Design

A major challenge to end the pandemic caused by SARS-CoV-2 is to develop a broadly protective vaccine. As the key immunogen, the spike protein is frequently mutated with conserved epitopes shielded by glycans. Here, we reveal that spike glycosylation has site-differential effects on viral infectivity and lung epithelial cells generate spike with more infective glycoforms. Compared to the fully glycosylated spike, immunization of spike protein with N-glycans trimmed to the monoglycosylated state (Smg) elicits stronger immune responses and better protection for hACE2 transgenic mice against variants of concern. In addition, a broadly neutralizing monoclonal antibody was identified from the Smg immunized mice, demonstrating that removal of glycan shields to better expose the conserved sequences is an effective and simple approach to broad-spectrum vaccine development. One-Sentence SummaryRemoving glycan shields to expose conserved epitopes is an effective approach to develop a broad-spectrum SARS-CoV-2 vaccine.

microbiology↗

bioRxiv2021

D614G Substitution of SARS-CoV-2 Spike Protein Increases Syncytium Formation and Viral Transmission via Enhanced Furin-mediated Spike Cleavage

Since the D614G substitution in the spike (S) of SARS-CoV-2 emerged, the variant strain underwent rapid expansion to become the most abundant strain worldwide. Therefore, this substitution may provide an advantage of viral spreading. To explore the mechanism, we analyzed 18 viral isolates containing S proteins with either G614 or D614. Both the virus titer and syncytial phenotype were significantly increased in S-G614 than in S-D614 isolates. We further showed increased cleavage of S at the furin substrate site, a key event that promotes syncytium, in S-G614 isolates. These functions of the D614G substitution were validated in cells expressing S protein. The effect on syncytium was abolished by furin inhibitor treatment and mutation of the furin-cleavage site, suggesting its dependence on cleavage by furin. Our study provides a mechanistic explanation for the increased transmissibility of S-G614 containing SARS-CoV-2 through enhanced furin-mediated S cleavage, which increases membrane fusion and virus infectivity.

microbiology↗

bioRxiv2020

Distinct Inductions of and Responses to Type I and Type III Interferons PromoteInfections in Two SARS-CoV-2 Isolates

The recent emerging coronavirus, SARS-CoV-2, has been rapidly and widely spread and causing an ongoing viral pneumonia outbreak worldwide. It has been observed that SARS-CoV-2 patients show a rather long and asymptomatic incubation time. We characterized the abilities to induce and to response to IFN{beta}/IFN{lambda}1 of two or our clinical isolates, SARS-CoV-2/NTU01/TWN/human/2020 and SARS-CoV-2/NTU02/TWN/human/2020, which exhibit only two amino acid differences over the [~]30kb viral genome. We found that both isolates may infect Huh7, A549 and Calu-3 cells, yet the RIG-I-like receptor-dependent antiviral signaling was poorly induced in these cells in the early infections. Unexpectedly, we found that the intracellular vRNA levels of these isolates were sustained upon to type I/III IFN treatments, and this phenotype was more pronounced in the Taiwan/NTU01/2020 isolate. The type I/III IFN responses are antiviral but partially proviral in the case of SARS-CoV-2 infections. Poor induction and response to innate immunity may contribute to destitute neutralization index of the antibody produced, and indeed we found that the patient serum could not efficiently neutralize SARS-CoV-2 virions. With better understandings of the interplay between SARS-CoV-2 and the host antiviral innate immunity, our report may provide new insights for the regimen of therapies for SARS-CoV-2 infected patients.

microbiology↗