The Chinese hamster ovary (CHO) cells used to produce biopharmaceutical proteins are known to contain type-C endogenous retrovirus (ERV) sequences in their genome and to release retroviral-like particles. Although evidence for their infectivity is missing, this has raised safety concerns. As the genomic origin of these particles remained unclear, we characterized type-C ERV elements at the genome, transcriptome, and viral particle RNA levels. We identified 173 type-C ERV sequences clustering into three functionally conserved groups. Transcripts from one type-C ERV group were full-length, with intact open reading frames, and cognate viral genome RNA was loaded into retroviral-like particles, suggesting that this ERV group may produce functional viruses. CRISPR-Cas9 genome editing was used to disrupt the gag gene of the expressed type-C ERV group. Comparison of CRISPR-derived mutations at the DNA and RNA level led to the identification of a single ERV as the main source of the release of RNA-loaded viral particles. Clones bearing a Gag loss-of-function mutation in this ERV showed a reduction of RNA-containing viral particle release down to detection limits, without compromising cell growth or therapeutic protein production. Overall, our study provides a strategy to mitigate potential viral particle contaminations resulting from ERVs during biopharmaceutical manufacturing.
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http://dx.doi.org/10.1002/bit.27200 | DOI Listing |
Elife
January 2025
Institute of Parasitology, Faculty of Agricultural and Environmental Sciences, McGill University, Montreal, Canada.
Paramyxovirus membrane fusion requires an attachment protein for receptor binding and a fusion protein for membrane fusion triggering. Nipah virus (NiV) attachment protein (G) binds to ephrinB2 or -B3 receptors, and fusion protein (F) mediates membrane fusion. NiV-F is a class I fusion protein and is activated by endosomal cleavage.
View Article and Find Full Text PDFInvest Ophthalmol Vis Sci
January 2025
Department of Ophthalmology, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Purpose: This study aimed to identify a novel recombinant adeno-associated virus (rAAV) capsid variant that can widely transfect the deep retina through intravitreal injection and to assess their effectiveness and safety in gene delivery.
Methods: By adopting the sequences of various cell-penetrating peptides and inserting them into the capsid modification region of AAV2, we generated several novel variants. The green fluorescent protein (GFP)-carrying variants were screened following intravitreal injection.
J Virol
December 2024
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA.
Unlabelled: Flavivirus envelope (E) and precursor M (prM) proteins, when ectopically expressed, assemble into empty, virus-like particles (VLPs). Cleavage of prM to M and loss of the pr fragment converts the VLPs from immature to mature particles, mimicking a similar maturation of authentic virions. Most of the VLPs obtained by prM-E expression are smaller than virions; early, low-resolution cryo-EM studies suggested a simple, 60-subunit, icosahedral organization.
View Article and Find Full Text PDFACS Infect Dis
January 2025
Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States.
RNA viruses possess small genomes encoding a limited repertoire of essential and often multifunctional proteins. Although genetically tagging viral proteins provides a powerful tool for dissecting mechanisms of viral replication and infection, it remains a challenge. Here, we leverage genetic code expansion to develop a recoded strain of respiratory syncytial virus (RSV) in which the multifunctional nucleoprotein is site-specifically modified with a noncanonical amino acid.
View Article and Find Full Text PDFSci Adv
January 2025
Graduate Program in Immunology, University of Iowa, Iowa City, IA 52242, USA.
Ebola virus (EBOV) causes severe human disease. During late infection, EBOV virions are on the skin's surface; however, the permissive skin cell types and the route of virus translocation to the epidermal surface are unknown. We describe a human skin explant model and demonstrate that EBOV infection of human skin via basal media increases in a time-dependent and dose-dependent manner.
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