Biology subjects

Vragel, G.

Publications and source records attributed to Vragel, G..

4 recordsLinked to original sources

bioRxiv2026

HIGH DOSE GAMMAHERPESVIRUS INFECTION IN MACROPHAGES RESULTS IN INFLAMMATORY MULTIMODAL CELL DEATH

Human gammaherpesviruses (gHVs) including Epstein-Barr Virus and Kaposis sarcoma associated herpesvirus are linked to cancer and inflammatory disease development. The outcome of gHV infection is highly regulated by cell type, with macrophages identified as an important early infection target that can also serve as a latency reservoir. Here, we used the mouse gHV model, murine gammaherpesvirus (MHV68), to identify a dose-dependent outcome of MHV68 infection of macrophages, with high dose infection resulting in extensive morphological changes, viral gene expression, and a pronounced inflammatory cell death not observed under conditions of lytic replication occurring at lower infectious dose. Virion envelope and tegument components were not sufficient for this dose-dependent cell death, which required intact viral DNA and virus transcription, yet occurred independently of viral DNA replication and late gene transcription. Necrostatin-1 (Nec-1) treatment, an anti-inflammatory therapeutic, limited cell death and reduced cell morphology alterations, with no impact on virus replication, uncoupling cell death from lytic replication. Activation of autophagy profoundly limited high dose infection outcomes, with increased cell survival and reduced viral gene expression. Despite the improved cell survival observed in cells treated with Nec-1, biochemical analysis of infected cultures identified robust apoptosis induction with subsequent activation of gasdermin E, suggesting a multi-modal cell death mechanism culminating in pyroptosis. Our findings suggest that high dose macrophage infection byMHV68 is a major driver of inflammatory cell death to potentially shape downstream inflammation and immune responses.

microbiology↗

bioRxiv2026

Cytokine signaling regulates multiple stages of gammaherpesvirus infection in myeloid cells

The gammaherpesviruses, including Epstein-Barr Virus and Kaposis Sarcoma-associated Herpesvirus, establish lifelong infections by maintaining a balance between lytic and latent infection states. How this balance is regulated in myeloid cells, an important but understudied cell type that can achieve both infection states, remains unclear. Using the murine gammaherpesvirus 68 (MHV68) model, we show that IFNg; and IL-4 reciprocally regulate lytic infection in macrophages in a time- and JAK/STAT signaling dependent-manner, with basal JAK/STAT signaling further restricting lytic infection. Using a combination of MHV68 reporter viruses, cellular and molecular techniques, we demonstrate that IFNg blocks lytic replication through at least two distinct mechanisms, restricting delivery to or stability of the viral genome in the nucleus and potently restricting lytic cycle progression downstream of the immediate-early viral transactivator, RTA. These findings define specific points during lytic infection where IFNg; to enforce restricted, latent-like infection in myeloid cells.

immunology↗

bioRxiv2024

Control of pili synthesis and putrescine homeostasis in Escherichia coli

Polyamines are biologically ubiquitous cations that bind to nucleic acids, ribosomes, and phospholipids and, thereby, modulate numerous processes, including surface motility in Escherichia coli. We characterized the metabolic pathways that contribute to polyamine-dependent control of surface motility in the commonly used strain W3110 and the transcriptome of a mutant lacking a putrescine synthetic pathway that was required for surface motility. Genetic analysis showed that surface motility required type 1 pili, the simultaneous presence of two independent putrescine anabolic pathways, and modulation by putrescine transport and catabolism. An immunological assay for FimA--the major pili subunit, reverse transcription quantitative PCR of fimA, and transmission electron microscopy confirmed that pili synthesis required putrescine. Comparative RNAseq analysis of a wild type and {Delta}speB mutant which exhibits impaired pili synthesis showed that the latter had fewer transcripts for pili structural genes and for fimB which codes for the phase variation recombinase that orients the fim operon promoter in the ON phase, although loss of speB did not affect the promoter orientation. Results from the RNAseq analysis also suggested (a) changes in transcripts for several transcription factor genes that affect fim operon expression, (b) compensatory mechanisms for low putrescine which implies a putrescine homeostatic network, and (c) decreased transcripts of genes for oxidative energy metabolism and iron transport which a previous genetic analysis suggests may be sufficient to account for the pili defect in putrescine synthesis mutants. We conclude that pili synthesis requires putrescine and putrescine concentration is controlled by a complex homeostatic network that includes the genes of oxidative energy metabolism.

microbiology↗

bioRxiv2023

Murine Gammaherpesvirus 68 Efficiently Infects Myeloid Cells Resulting In An Atypical, Restricted Form Of Infection

The gammaherpesviruses establish a lifelong infection, with the cellular outcome of infection intimately regulated by cell type. Though myeloid cells are an early infection target, infection results in widely divergent outcomes without a clear explanation. Here we use murine gammaherpesvirus 68 to demonstrate that macrophages are readily infectable, resulting in three divergent infection outcomes dictated by viral and host factors. Infection in vivo and in a cell culture model results in a high frequency of viable cells characterized by restricted viral transcription and unexpected transcription of the ORF75 locus, with rare cells initiating but failing to complete lytic replication. Restricted infection can be fully converted to productive lytic replication by pre-treatment with the host cytokine IL-4. Finally, infection with a high viral dose also results in productive infection, but triggers increased cell death. These studies demonstrate stepwise regulation of virus infection and identify virus and host factors that dictate divergent outcomes in a single cell type.

microbiology↗