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Results for “Virus Replication”

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PubMed2026

Nonclinical investigation of the potential of MHAA4549A, an anti-influenza A therapeutic antibody, to mediate antibody-dependent enhancement.

Antibody-dependent enhancement (ADE) of infection and disease is a theoretical safety risk for antiviral antibodies against seasonal viruses with antigenic drift, such as influenza. ADE of infection may occur if virus-specific antibodies at subtherapeutic, nonneutralizing concentrations facilitate virus uptake, thus potentially enhancing virus replication. In contrast, ADE of disease reflects exacerbation of viral disease severity through viral replication-dependent or -independent mechanisms. Because of the theoretical concern of ADE, nonclinical safety assessment of therapeutic anti-influenza antibodies includes a thorough evaluation of ADE potential. The current set of studies was conducted to investigate the potential of MHAA4549A-a broadly specific, neutralizing, therapeutic anti-influenza A antibody-to elicit ADE of infection and disease of influenza H3N2 A/Aichi/2/68 (X31) across a broad dose range. Assessment of ADE was based on totality of results from both in vitro and mouse influenza studies with integration across study endpoints. In vitro studies demonstrated that MHAA4549A can mediate increased X31 entry into human and murine monocytic cells, but increased uptake did not result in enhanced viral replication or release under physiologic conditions. In a mouse model of X31 infection, intravenous administration of MHAA4549A resulted in delayed body weight recovery, but no exacerbation in orthogonal endpoints including mortality, lung viral titers or genomes, lung weights, or severity of influenza pneumonia. Overall, the totality of nonclinical data did not demonstrate any clear indication of ADE of infection at nonneutralizing concentrations, suggesting a low risk for MHAA4549A to cause enhanced influenza A-mediated disease at subtherapeutic doses.

Animals↗

PubMed2025

Droplet-Based Single-Cell 3' mRNA Sequencing of Marburg Virus-Infected Samples.

Single-cell technologies are continually evolving with emerging methods that are gradually uncovering the central DNA-RNA-protein dogma. Single-cell RNA sequencing is one arm of a multi-omic approach that achieves an astounding level of granularity to reveal the complexity of virus-host interactions at the transcriptomic level. Cell tropism, virus replication, pathogenesis, and gene expression changes mediated by the virus and the host's immune response to infection are just some areas of study that are gaining better clarity due to the high-resolution analysis afforded by the technology.We describe a single-cell sequencing protocol for Marburg virus infection in vivo using nonhuman primate blood and the 10× Chromium Next GEM single-cell genomics methodology. Working with pathogens of high consequence is logistically complicated, requiring containment in biosafety level (BSL)-4 laboratories and harsh inactivation procedures before samples can safely be removed to lower biosafety conditions. We provide procedural insight into sample isolation and processing conducted in BSL-4 and describe the requirements for safe sample removal without jeopardizing quality for down-stream sequencing and analysis in BSL-2 conditions. Characterization of complicated biological processes mediated by high-containment pathogens, typically restricted to analogous model systems, e.g., minigenome, can be achieved using live virus.

Animals↗

PubMed2026

Host-interferon-stimulated gene response to virus-host recombinant variants of hepatitis E virus and enhanced viral replication.

The hepatitis E virus (HEV) is a leading cause of acute hepatitis worldwide. HEV infection can become chronic in immunocompromised individuals, in whom virus-host recombinant variants (VHRVs) can be detected. These variants often harbor host-derived insertions in the polyproline-rich region (PPR), and most display enhanced replication in vitro. However, the mechanisms underlying this replicative advantage remain unclear. It is likely that genes of the infected cells are differentially expressed according to the replicative capacity of the strain. The host factors involved in the improvement of the replicative capacity of these VHRVs are yet to be identified.In this study, we analyzed the host transcriptional response to seven VHRVs in HepG2/C3A cells using bulk RNA sequencing at 48 h and 168 h post-infection. Five VHRVs (RNF19A, ZNF787, KIF1B, RPS17, EEF1A1) previously associated with a high replication rate induced more significant, distinct transcriptomic changes than low-replicative variants (RNA18, RPL6), particularly at 168 h. A shared set of 25 genes, especially interferon-stimulated genes (ISGs), was upregulated in cells infected with high-replicating variants. Interestingly, ISG induction was limited at 48 h despite high viral RNA concentrations, suggesting a delayed antiviral response. At 168 h, high ISG expression coincided with high viral loads, indicating that VHRVs may evade or exploit immune defenses. Our findings reveal candidate ISGs such as IFIT1 and ISG15 that may influence HEV persistence and immune escape. These results offer new insights into the interplay between VHRV replication and host immunity.IMPORTANCEHepatitis E virus (HEV) is a major cause of acute hepatitis and can cause chronic infections in immunocompromised individuals. Virus-host recombinant variants (VHRVs) having integrated host-derived insertions often replicate more effectively, yet the host determinants of this phenotype remain unclear. With RNA sequencing of HepG2/C3A-infected cells, we observed that high-replicating VHRVs induce a delayed but strong expression of interferon-stimulated genes (ISGs), including IFIT1 and ISG15, despite high viral loads. These results suggest that VHRVs may transiently modulate or evade aspects of host antiviral defenses. Our study revealed host transcriptional patterns associated with enhanced viral replication, providing insight into potential mechanisms that enhance HEV replication and highlighting candidate pathways that could influence the interplay between viral replication and immune responses, all requiring further investigation.

Humans↗

PubMed2026

A novel dimerization site in non-structural protein 5A of hepatitis C virus regulates viral replication fitness.

We previously found that high genome replication fitness of the hepatitis C virus (HCV) was associated with severe disease in immunocompromised patients. Elevated replication fitness was mediated by accumulation of mutations in the replication enhancing domain (ReED) within domain (D) 2 of non-structural protein (NS) 5A. NS5A is a partially unstructured phosphoprotein lacking enzymatic activity but fulfilling a key role in HCV replication due to interacting with various cellular and viral proteins. It can exist in a variety of dimeric and oligomeric conformations mediated by NS5A D1 with clinically approved NS5A inhibitors proposed to exert their antiviral function by fixing these dimers in distinct conformations. In this study, we aimed at elucidating the ReED's mode of action. AlphaFold modelling indicated a so far unrecognized NS5A dimerization site in the ReED. Indeed, split nano luciferase assays revealed a significantly stronger NS5A dimerization of high replicator ReED variants, suggesting that high replication fitness is mediated by enforcement of NS5A self-interaction. This hypothesis was supported by the effect of low dose (1 pM) NS5A inhibitor treatment, increasing replication fitness and phenocopying the effects of ReED mutations. Furthermore, we found that HCV isolate JFH1, replicating with very high efficiency, is completely resistant to the regulatory function of the ReED. Chimeric replicons composed of ReED resistant JFH1 and the ReED sensitive isolate J6 identified NS3 helicase and NS5B polymerase as critical genetic elements mediating ReED sensitivity/resistance. Our data overall suggest that the ReED in NS5A is a negative regulator of HCV replication fitness with dimerization releasing the inhibitory interaction with helicase and/or polymerase, thereby likely facilitating initiation of RNA synthesis.

Viral Nonstructural Proteins↗

PubMed2026

SARS-CoV-2 3CLpro inhibits the replication of influenza viruses through the cleavage of NP and PA.

The co-circulation of multiple viruses can lead to distinct pathological outcomes, yet how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection influences other viral infections remains poorly understood, despite its documented high frequency during the pandemic. In this study, we investigated how the proteolytic activity of SARS-CoV-2 3C-like protease (3CLpro) influences the replication of influenza A virus. In silico analysis identified candidate 3CLpro cleavage sites across numerous viral proteins, and biochemical assays confirmed that 3CLpro catalyzes the degradation of influenza virus nucleoprotein (NP) and polymerase acidic protein (PA) in a manner requiring its protease activity. This degradation of NP and PA, which are essential for viral genome packaging and transcription, disrupted the influenza replicative cycle and suppressed viral replication, both upon ectopic 3CLpro expression and during SARS-CoV-2 infection. Our data uncover a direct, enzyme-based mechanism by which SARS-CoV-2 can suppress influenza virus replication during coinfection. We provide a molecular explanation for the sharp, global decline in influenza activity observed during the COVID-19 pandemic and illustrate how enzymatic weapons of one virus can be repurposed to restrain a competing pathogen.

Virus Replication↗

PubMed2026

Naturally occurring mutations in replication proteins of a small RNA virus that alter the number, sizes, and relative abundances of subgenomic RNAs.

Many positive-strand (+) RNA viruses produce subgenomic RNAs (sgRNAs) in infected cells. sgRNAs are synthesized by virus-encoded replication proteins (RPs), but whether RPs regulate the number and sizes of sgRNAs remains largely unknown. We report multiple naturally occurring mutations within the RPs of turnip crinkle virus (TCV) that alter the number, sizes, and relative abundances of TCV sgRNAs. TCV is a (+) RNA virus that normally produces two sgRNAs: the 1,724-nucleotide (nt) sgRNA1 expressing movement proteins, and the 1,449-nt sgRNA2 expressing capsid protein. A single amino acid change, A113V, within a region shared by TCV RPs p28 and p88, diminished sgRNA1 levels and delayed viral systemic spread. Interestingly, three second-site RP mutations emerged in infected plants that, alone or in combination with A113V, resulted in over-production of sgRNA1 or accumulation of two alternative sgRNAs of 1,876 and 1,601 nt, and rescued A113V defects. The alternative sgRNAs originated from nearly identical recombination events, their size difference reflecting varying 5' extensions. They may have accumulated to high levels through selective stabilization of their (-)-strand intermediates that were in turn derived from transcriptional pausing and recombination. Our findings reveal previously unrecognized constraints on viral RPs that ensure production of sgRNAs with precise sizes and abundances.

Subgenomic RNA↗

PubMed2025

A New Type of Nonsuppressible Viremia Produced by HIV-Infected Macrophage.

BACKGROUND: HIV-1 RNA typically declines rapidly after initiation of antiretroviral therapy (ART); often reaching undetectable levels within a few weeks and remaining undetectable by standard assays. However, some patients on ART have persistent nonsuppressible viremia (NSV) that does not respond to treatment optimization or intensification. NSV can emerge at the time of ART initiation (primary NSV) or after being ART-suppressed (secondary NSV). Here, we examine mechanisms producing primary NSV in four people on ART. METHODS: Blood samples were collected from four participants who, despite being adherent to ART, required approximately a year or more to become virologically suppressed. Viral RNA and proviral DNA genomes were sequenced to examine HIV-1 drug resistance, genome intactness and genetic diversity. The ability of HIV-1 Envs to facilitate efficient entry into cells expressing low levels of CD4 (a proxy for macrophage tropism) was assessed. RESULTS: Before ART, the blood contained HIV-1 RNA genomes that were adapted to replication in CD4+ T cells and rapidly decayed after ART initiation. During ART, the blood contained HIV-1 genomes that were drug sensitive, genetically diverse, macrophage-tropic, not evolving and often had defects in vpr. CONCLUSIONS: Our results suggest that in individuals with primary NSV, ART stopped virus replication, but large pools of long-lived, HIV-infected macrophage continued to produce virus. This is mechanistically distinct from secondary NSV produced by CD4+ T cell clones. In addition, defects in vpr independently accumulation in macrophage-tropic lineages found in three participants, suggesting that vpr may impact survival of, or virus production from, HIV-infected macrophage.

Journal Article↗

PubMed2026

Small molecule inhibition of the mitochondrial lipid transfer protein STARD7 attenuates influenza viral replication.

The increasing appearance of drug-resistant and zoonotic influenza strains highlights an urgent need for host-directed antivirals that offer broad-spectrum activity and a higher barrier to resistance. Here, we describe the characterization of M4, a small-molecule identified from a high-throughput screen that potently inhibits influenza A and B viruses. Mechanistic studies reveal that M4 suppresses influenza virus replication by preventing formation of export-competent viral ribonucleoprotein (vRNP) complexes in the nucleus. Chemoproteomic profiling identified the lipid transfer protein STARD7 as the primary cellular target, and genetic depletion of STARD7 phenocopies the antiviral effects of M4. Additional studies localized the M4 binding site to cysteine 302 within the lipid-binding domain of STARD7, supporting a model in which STARD7-dependent lipid transfer activity promotes efficient vRNP assembly and nuclear export. Combining M4 with baloxavir enhances antiviral efficacy in a murine infection model, providing in vivo support for a host-directed therapeutic strategy. Together, these results identify STARD7 as a metabolic checkpoint licensing vRNP nuclear export and they establish a proof of concept for therapeutic intervention with small molecule inhibitors.

Journal Article↗

PubMed2025

Natural self-attenuation of pathogenic viruses by deleting the silencing suppressor coding sequence for long-term plant-virus coexistence.

Potyviridae is the largest family of plant-infecting RNA viruses. All members of the family (potyvirids) have single-stranded positive-sense RNA genomes, with polyprotein processing as the expression strategy. The 5'-proximal regions of all potyvirids, except bymoviruses, encode two types of leader proteases: the serine protease P1 and the cysteine protease HCPro. However, their arrangement and sequence composition vary greatly among genera or even species. The leader proteases play multiple important roles in different potyvirid-host combinations, including RNA silencing suppression and virus transmission. Here, we report that viruses in the genus Arepavirus, which encode two HCPro leader proteases in tandem (HCPro1-HCPro2), can naturally lose the coding sequences for these two proteins during infection. Notably, this loss is associated with a shift in foliage symptoms from severe necrosis to mild chlorosis or even asymptomatic infections. Further analysis revealed that the deleted region is flanked by two short repeated sequences in the parental isolates, suggesting that recombination during virus replication likely drives this genomic deletion. Reverse genetic approaches confirmed that the loss of leader proteases weakens RNA silencing suppression and other critical functions. A field survey of areca palm trees displaying varied symptom severity identified a transitional stage in which full-length viruses and deletion mutants coexist in the same tree. Based on these findings, we propose a scenario in which full-length isolates drive robust infections and facilitate plant-to-plant transmission, eventually giving rise to leader protease-less variants that mitigate excessive damage to host trees, allowing long-term coexistence with the perennial host. To our knowledge, this is the first report of potyvirid self-attenuation via coding sequence loss.

Plant Diseases↗

PubMed2018

Replication of Zika Virus in Human Prostate Cells: A Potential Source of Sexually Transmitted Virus.

BACKGROUND: While Zika virus (ZIKV) is mainly transmitted by mosquitoes, numerous cases of sexual transmission have been reported during recent outbreaks. Little is known about which host cell types or entry factors aid in mediating this sexual transmission. METHODS: In this study, we investigated ZIKV cell tropism by infecting 2 types of human prostate cells with 3 contemporary ZIKV isolates from persons infected in the Americas. We used real-time quantitative polymerase chain reaction and immunofluorescence analyses to measure infection and flow cytometry to detect entry factor expression. RESULTS: Here we show that ZIKV infects, replicates, and produces infectious virus in prostate stromal mesenchymal stem cells, epithelial cells, and organoids made with a combination of these cells. We also show that prostate cells express several well-characterized flavivirus attachment factors. In contrast, dengue virus does not infect or does not replicate in these prostate cells, although it is known to use similar receptors. CONCLUSIONS: Our results indicate that ZIKV favors infection of stromal cells more so than epithelial cells in organoids, possibly indicating a preference for stem cells in general. Overall, these results suggest that ZIKV replication occurs in the human prostate and can account for ZIKV secretion in semen, thus leading to sexual transmission.

Americas↗

PubMed2024

The immediate-early protein 1 of human herpesvirus 6B interacts with NBS1 and inhibits ATM signaling.

Viral infection often trigger an ATM serine/threonine kinase (ATM)-dependent DNA damage response in host cells that suppresses viral replication. Viruses evolved different strategies to counteract this antiviral surveillance system. Here, we report that human herpesvirus 6B (HHV-6B) infection causes genomic instability by suppressing ATM signaling in host cells. Expression of immediate-early protein 1 (IE1) phenocopies this phenotype and blocks homology-directed double-strand break repair. Mechanistically, IE1 interacts with NBS1, and inhibits ATM signaling through two distinct domains. HHV-6B seems to efficiently inhibit ATM signaling as further depletion of either NBS1 or ATM do not significantly boost viral replication in infected cells. Interestingly, viral integration of HHV-6B into the host's telomeres is not strictly dependent on NBS1, challenging current models where integration occurs through homology-directed repair. Given that spontaneous IE1 expression has been detected in cells of subjects with inherited chromosomally-integrated form of HHV-6B (iciHHV-6B), a condition associated with several health conditions, our results raise the possibility of a link between genomic instability and the development of iciHHV-6-associated diseases.

Humans↗

PubMed2024

Replication of single viruses across the kingdoms, Fungi, Plantae, and Animalia.

It is extremely rare that a single virus crosses host barriers across multiple kingdoms. Based on phylogenetic and paleovirological analyses, it has previously been hypothesized that single members of the family Partitiviridae could cross multiple kingdoms. Partitiviridae accommodates members characterized by their simple bisegmented double-stranded RNA genome; asymptomatic infections of host organisms; the absence of an extracellular route for entry in nature; and collectively broad host range. Herein, we show the replicability of single fungal partitiviruses in three kingdoms of host organisms: Fungi, Plantae, and Animalia. Betapartitiviruses of the phytopathogenic fungusRosellinia necatrix could replicate in protoplasts of the carrot (Daucus carota), Nicotiana benthamiana and Nicotiana tabacum, in some cases reaching a level detectable by agarose gel electrophoresis. Moreover, betapartitiviruses showed more robust replication than the tested alphapartitiviruses. One of the fungal betapartitiviruses, RnPV18, could persistently and stably infect carrot plants regenerated from virion-transfected protoplasts. Both alpha- and betapartitiviruses, although with different host preference, could replicate in two insect cell lines derived from the fall armyworm Spodoptera frugiperda and the fruit fly Drosophila melanogaster. Our results indicate the replicability of single partitiviruses in members of three kingdoms and provide insights into virus adaptation, host jumping, and evolution.

Animals↗

PubMed2026

Development and preclinical evaluation of a decoy DLL4-encoding oncolytic HSV-1 for high-grade glioma.

Preclinical and clinical investigation of oncolytic HSV-1 (oHSV) treatment for cancer has indicated increased Notch signaling in tumors after treatment. Since Notch activation often heralds cancer cell stemness, angiogenesis, and invasion, the induction of this pathway after oHSV virotherapy can support tumor growth and limit response to virotherapy. Here, we evaluated the impact of blocking DLL4, a Notch ligand, on virotherapy. Matched tumor biopsies pre- and post-oHSV (CAN-3110, NCT03152318) treatment revealed an induction of DLL4 post-therapy. We observed that expression of a recombinant soluble decoy DLL4 (sDLL4) could block Notch activation in tumor cells. Thus, we engineered an oHSV vector designed to encode soluble DLL4 (OVsDLL4) to block ligand-mediated Notch signaling. RNA sequencing and gene set enrichment analysis revealed that, relative to control oHSV, OVsDLL4 blocked Notch and sprouting angiogenesis pathways after treatment. Despite slower virus replication in vitro, OVsDLL4 cytotoxicity remained effective against tumor cells. Transcriptome profiling also indicated a significant dysregulation of metabolic pathways related to oxidative phosphorylation and glutathione metabolism, in accordance with increased oxygen consumption observed by Seahorse analysis in cells expressing sDLL4. OVsDLL4-treated cells further showed increased reactive oxygen species relative to control oHSV-treated cells. Co-culture of infected tumor cells with immune cells revealed that OVsDLL4 treatment polarized them toward an inflammatory phenotype. In vivo, the therapeutic efficacy of OVsDLL4 was underscored, as treatment of glioma-bearing mice resulted in reduced tumor burden and prolonged survival.

Journal Article↗

PubMed2025

A pan-beta-coronavirus vaccine bearing conserved and asymptomatic B- and T-cell epitopes protects against highly pathogenic Delta and highly transmissible Omicron SARS-CoV-2 variants.

Over the last five years of the COVID-19 pandemic, the repetitive mutations and deletions in the SARS-CoV-2 genome, primarily targeting the Spike gene, resulted in the emergence of multiple viral variants and sub-variants. The non-updated mismatched Spike-based sub-unit vaccines are less effective due to the ability of these SARS-CoV-2 variants and sub-variants to evade vaccine-induced humoral immunity. To reduce reliance on neutralizing antibodies and prevent potential mismatches between circulating variants, sub-variants, and the vaccines, we have identified highly conserved Spike and non-Spike viral epitopes associated with protective asymptomatic B- and T-cell immune responses, respectively. We demonstrated that unvaccinated asymptomatic patients with COVID-19 recognized these conserved B- and T-cell epitopes. Using the mRNA-LNP-based antigen delivery system, we developed a multi-epitope vaccine that incorporates the conserved B-cell epitopes, CD4+ T-cell epitopes, and CD8+ T-cell epitopes. To assess the efficacy of this "asymptomatic" multi-epitope vaccine, we used the HLA-A*02:01/HLA-DRB1* 01:01-hACE-2 triple transgenic mouse model. We demonstrated that this "asymptomatic" multi-epitope vaccine conferred robust protection against infection and disease caused by the SARS-CoV-2 Delta (B.1.617.2) and Omicron (XBB.1.5) variants as assessed by: (i) prevention of weight loss, (ii) reduction of virus replication, and (iii) lung pathology. This protection was associated with: (i) strong antibody responses; and (ii) high frequency of anti-viral IFN-γ-producing CD4+ and CD8+ T-cells. These findings illustrate the possibility of developing a pan-beta-coronavirus vaccine to induce broad-spectrum protective immunity against SARS-CoV-2 variants and sub-variants by targeting highly conserved "asymptomatic" B- and T-cell epitopes identified from both structural and non-structural viral proteins.

Epitopes, T-Lymphocyte↗

PubMed2025

Inference of differential kinase interaction networks with KINference.

MOTIVATION: Differential kinase interaction networks (DKINs) are networks containing kinase-substrate links that are differentially active between two conditions. Existing methods are either able to predict condition-agnostic kinase-substrate links or condition-specific differential kinase activity, but do not provide differential kinase-substrate links. Moreover, existing methods for predicting kinase-substrate links usually rely on curated biochemical knowledge. Thus, there is a lack of data-driven DKIN inference methods that are also applicable when prior knowledge is scarce. RESULTS: To address this need, we present KINference. KINference combines computation of a baseline KIN representing the space of all possible kinase-substrate links with filters applied to nodes and edges to identify differentially active subnetworks that are relevant in the context of a specific phosphoproteomics dataset. For the node filters, we rely on functional relevance and differential phosphorylation scores; for the edge filters, we make use of prize-collecting Steiner trees and correlations between phosphorylation sites of kinases and their target proteins. Tests on two phosphoproteomics datasets (kinase inhibition in breast cancer cells, SARS-CoV-2 infection in Calu-3 cells) show that the proposed filters produce significant results in terms of overlap with known interactions between kinases and phosphorylation sites. Furthermore, a case study on the SARS-CoV-2 infection data, suggests a potential host pathway linked to virus replication, showcasing the process of hypothesis generation utilizing DKINs computed by KINference. AVAILABILITY AND IMPLEMENTATION: KINference is available as an R package at https://github.com/bionetslab/KINference and https://doi.org/10.5281/zenodo.15411150. Scripts to reproduce the results are available at https://github.com/bionetslab/KINference-Evaluation-Scripts and https://doi.org/10.5281/zenodo.15424599.

Humans↗

PubMed2023

Intra-Host Evolution Provides for the Continuous Emergence of SARS-CoV-2 Variants.

Variants of concern (VOC) in SARS-CoV-2 refer to viruses whose viral genomes differ from the ancestor virus by ≥3 single-nucleotide variants (SNVs) and that show the potential for higher transmissibility and/or worse clinical progression. VOC have the potential to disrupt ongoing public health measures and vaccine efforts. Still, too little is known regarding how frequently new viral variants emerge and under what circumstances. We report a study to determine the degree of SARS-CoV-2 sequence evolution in 94 patients and to estimate the frequency at which highly diverse variants emerge. Two cases accumulated ≥9 SNVs over a 2-week period and one case accumulated 23 SNVs over 3 weeks, including three nonsynonymous mutations in the spike protein (D138H, E554D, D614G). The remainder of the infected patients did not show signs of intra-host evolution. We estimate that in as much as 2% of hospitalized COVID-19 cases, variants with multiple mutations in the spike glycoprotein emerge in as little as 1 month of persistent intra-host virus replication. This suggests the continued local emergence of variants with multiple nonsynonymous SNVs, even in patients without overt immune deficiency. Surveillance by sequencing for (i) viremic COVID-19 patients, (ii) patients suspected of reinfection, and (iii) patients with diminished immune function may offer broad public health benefits. IMPORTANCE New SARS-CoV-2 variants can potentially disrupt ongoing public health measures and vaccine efforts. Still, little is known regarding how frequently new viral variants emerge and under what circumstances. Based on this study, we estimate that in hospitalized COVID-19 cases, variants with multiple mutations may emerge locally in as little as 1 month, even in patients without overt immune deficiency. Surveillance by sequencing for continuously shedding patients, patients suspected of reinfection, and patients with diminished immune function may offer broad public health benefits.

Humans↗

PubMed2025

Construction and In Vitro and In Vivo Analysis of Coxsackievirus B4 Reporter Viruses: Attenuated Virulence but Highly Efficient for Antiviral Drug Screening and Evaluation.

Coxsackievirus B4 (CVB4) is an enterovirus with one of the highest mortality rates following infection, yet research on it remains limited. To enhance the efficiency of CVB4 research, we developed the rCVB4-EGFP and rCVB4-NanoLuc reporter viruses. The replication kinetics of these reporter viruses in SH-SY5Y and HeLa cells were essentially consistent with those of the wild-type CVB4. A strong correlation was observed between the fluorescence and bioluminescence signals of rCVB4-EGFP and rCVB4-NanoLuc and viral titers at specific times postinfection. When evaluating the anti-CVB4 drug fluoxetine using these reporter viruses, the half-maximal effective concentrations derived from fluorescence signals, bioluminescence signal intensities, and viral genome copies were consistent. In In Vivo drug evaluations, because CVB4 can infect various tissues and organs, the bioluminescence signal of rCVB4-NanoLuc effectively demonstrated the antiviral effects of drugs, offering significant advantages over traditional tissue viral titer analysis. The reporter viruses exhibited reduced virulence compared with wild-type CVB4 both In Vitro, in SH-SY5Y and HeLa cells, and In Vivo, in ICR suckling mice. Although this reduced virulence may limit their application for studying pathogenic mechanisms, these reporter viruses can serve as highly efficient tools for high-throughput screening and evaluation of anti-CVB4 drugs, vaccines, and neutralizing antibodies.

Humans↗

PubMed2025

Performance of Subgenomic RT-PCR for Predicting SARS-CoV-2 Infectivity Compared to Genomic RT-PCR and Culture Isolation.

SARS-CoV-2 clinical samples can be detected as positive for a long period of time using real-time RT-PCR, even when patients are no longer infectious. Viral culture is the gold standard for assessing a patient's infectivity, but it is a time-consuming technique and lacks sensitivity. SARS-CoV-2 subgenomic RNA (sgRNA) detection has been used as a proxy for assessing the infectivity but only a limited number of studies have described its use in vitro and in clinical samples. This study aimed to evaluate the correlation between results from viral culture, genomic RT-PCR (gRT-PCR), and subgenomic RT-PCR (sgRT-PCR) during in vitro infection and in clinical samples. In vitro viral replication kinetics showed that both genomic RNA (gRNA) and subgenomic RNA (sgRNA) levels remained stable up to 21 days in the absence of replication-competent virus. Using clinical samples, sgRNA was detected in 87.5% of culture-positive samples, demonstrating better performances than gRT-PCR (Positive predictive value (PPV) 93.3% and Negative predictive value (NPV) of 87.5%) and an almost perfect agreement with culture results (Cohen κ = 0.81 [95% CI: 0.66-0.95]). These findings suggest that testing for sgRNA and/or using a gRNA Ct cut-off of 21.2 could be used as a proxy to determine the presence of SARS-CoV-2 replication-competent virus.

Humans↗