Bacteria-free reverse genetics techniques are crucial for the efficient generation of recombinant viruses, bypassing the need for labor-intensive bacterial cloning. These methods are particularly relevant for studying the pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19. This study compared the efficiency of three bacteria-free approaches—circular polymerase extension reaction (CPER) with and without nick sealing and infectious sub-genomic amplicons (ISA)—to bacterial artificial chromosome (BAC)-based technology for rescuing SARS-CoV-2. Significant differences in viral titers following transfection were observed between methods. CPER with nick sealing generated virus titers comparable to those of the BAC-based method and 10 times higher than those of the standard CPER. In contrast, ISA demonstrated extremely low efficiency, as cytopathic effects were detected only after two passages. All rescued viruses exhibited replication kinetics consistent with those of the original strain, with no significant deviation in replication capacity. Furthermore, the utility of CPER and ISA in genetically modifying SARS-CoV-2 was demonstrated by successfully inserting the gene encoding green fluorescent protein into the genome. Overall, this study underscores the potential of bacteria-free methods, such as CPER and ISA, in advancing SARS-CoV-2 research while highlighting their significant differences in efficiency.
Dengue virus (DENV), from the Flaviviridae family, is the causative agent of dengue fever and poses a significant global health challenge. The virus primarily affects the vascular system and liver; however, a growing body of evidence suggests its involvement in the gastrointestinal (GI) tract, contributing to clinical symptoms such as abdominal pain, vomiting, and diarrhea. However, the mechanisms underlying DENV infection in the digestive system remain largely unexplored. Prior research has detected viral RNA in the GI tissue of infected animals; however, whether the dengue virus can directly infect human enterocytes remains unclear. In this study, we examine the infectivity of human intestinal cell lines to the dengue virus and their subsequent response. We report that the Caco-2 cell line, a model of human enterocytes, is susceptible to infection and capable of producing viruses. Notably, differentiated Caco-2 cells exhibited a lower infection rate yet a higher level of virus production than their undifferentiated counterparts. These findings suggest that human intestinal cells are a viable target for the dengue virus, potentially elucidating the GI symptoms observed in dengue fever and offering a new perspective on the pathogenetic mechanisms of the virus.
Extracellular vesicles (EVs) play a crucial role in cell-to-cell
communication. EVs and viruses share several properties
related to their structure and the biogenesis machinery in
cells. EVs from virus-infected cells play a key role in virus
spread and suppression using various loading molecules,
such as viral proteins, host proteins, and microRNAs. However,
it remains unclear how and why viruses regulate EV
production inside host cells. The purpose of this study is to
investigate the molecular mechanisms underlying EV production
and their roles in Kaposi’s sarcoma-associated herpesvirus
(KSHV)-infected cells. Here, we found that KSHV
induced EV production in human endothelial cells via Rab-
27b upregulation. The suppression of Rab27b expression in
KSHV-infected cells enhanced cell death by increasing autophagic
flux and autolysosome formation. Our results indicate
that Rab27b regulates EV biogenesis to promote cell survival
and persistent viral infection during KSHV infection,
thereby providing novel insights into the crucial role of Rab-
27b in the KSHV life cycle.
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