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25-Hydroxycholesterol Inhibits Kaposi's Sarcoma Herpesvirus and Epstein-Barr Virus Infections and Activates Inflammatory Cytokine Responses.

ABSTRACT: Oncogenic gammaherpesviruses express viral products during latent and lytic infection that block the innate immune response. Previously, we found that Kaposi's sarcoma herpesvirus (KSHV/human herpesvirus-8) viral microRNAs (miRNAs) downregulate cholesterol biogenesis, and we hypothesized that this prevents the production of 25-hydroxycholesterol (25HC), a cholesterol derivative. 25HC blocks KSHV de novo infection of primary endothelial cells at a postentry step and decreases viral gene expression of LANA (latency-associated nuclear antigen) and RTA. Herein we expanded on this observation by determining transcriptomic changes associated with 25HC treatment of primary endothelial cells using RNA sequencing (RNA-Seq). We found that 25HC treatment inhibited KSHV gene expression and induced interferon-stimulated genes (ISGs) and several inflammatory cytokines (interleukin 8 [IL-8], IL-1α). Some 25HC-induced genes were partially responsible for the broadly antiviral effect of 25HC against several viruses. Additionally, we found that 25HC inhibited infection of primary B cells by a related oncogenic virus, Epstein-Barr virus (EBV/human herpesvirus-4) by suppressing key viral genes such as LMP-1 and inducing apoptosis. RNA-Seq analysis revealed that IL-1 and IL-8 pathways were induced by 25HC in both primary endothelial cells and B cells. We also found that the gene encoding cholesterol 25-hydroxylase (CH25H), which converts cholesterol to 25HC, can be induced by type I interferon (IFN) in human B cell-enriched peripheral blood mononuclear cells (PBMCs). We propose a model wherein viral miRNAs target the cholesterol pathway to prevent 25HC production and subsequent induction of antiviral ISGs. Together, these results answer some important questions about a widely acting antiviral (25HC), with implications for multiple viral and bacterial infections. IMPORTANCE A cholesterol derivative, 25-hydroxycholesterol (25HC), has been demonstrated to inhibit infections from widely different bacteria and viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, its mechanism of activity is still not fully understood. In this work, we look at gene expression changes in the host and virus after 25HC treatment to find clues about its antiviral activity. We likewise demonstrate that 25HC is also antiviral against EBV, a common cancer-causing virus. We compared our results with previous data from antiviral screening assays and found the same pathways resulting in antiviral activity. Together, these results bring us closer to understanding how a modified form of cholesterol works against several viruses.

SUBMITTER: Serquina AKP

PROVIDER: S-EPMC8593836 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The human herpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) are associated with Hodgkin's lymphoma (HL) and Primary effusion lymphomas (PEL), respectively, which are B cell malignancies that originate from germinal center B cells. PEL cells but also a quarter of EBV-positive HL tumor cells do not express the genuine B cell receptor (BCR), a situation incompatible with survival of normal B cells. EBV encodes LMP2A, one of EBV's viral latent membrane proteins, which likely replaces the BCR's survival signaling in HL. Whether KSHV encodes a viral BCR mimic that contributes to oncogenesis is not known because an experimental model of KSHV-mediated B cell transformation is lacking. We addressed this uncertainty with mutant EBVs encoding the KSHV genes K1 or K15 in lieu of LMP2A and infected primary BCR-negative (BCR(-)) human B cells with them. We confirmed that the survival of BCR(-) B cells and their proliferation depended on an active LMP2A signal. Like LMP2A, the expression of K1 and K15 led to the survival of BCR(-) B cells prone to apoptosis, supported their proliferation, and regulated a similar set of cellular target genes. K1 and K15 encoded proteins appear to have noncomplementing, redundant functions in this model, but our findings suggest that both KSHV proteins can replace LMP2A's key activities contributing to the survival, activation and proliferation of BCR(-) PEL cells in vivo.Several herpesviruses encode oncogenes that are receptor-like proteins. Often, they are constitutively active providing important functions to the latently infected cells. LMP2A of Epstein-Barr virus (EBV) is such a receptor that mimics an activated B cell receptor, BCR. K1 and K15, related receptors of Kaposi's sarcoma-associated herpesvirus (KSHV) expressed in virus-associated tumors, have less obvious functions. We found in infection experiments that both viral receptors of KSHV can replace LMP2A and deliver functions similar to the endogenous BCR. K1, K15, and LMP2A also control the expression of a related set of cellular genes in primary human B cells, the target cells of EBV and KSHV. The observed phenotypes, as well as the known characteristics of these genes, argue for their contributions to cellular survival, B cell activation, and proliferation. Our findings provide one possible explanation for the tumorigenicity of KSHV, which poses a severe problem in immunocompromised patients.

Project description:We previously demonstrated that 25HC (25-hydroxycholesterol, a derivative of cholesterol) blocks KSHV (Kaposi Sarcoma-associated Herpesvirus/ Human Herpesvirus-8) de novo infection of primary endothelial cells at a post-entry step and decreases viral gene expression. Herein we sought to determine transcriptomic changes associated with 25HC treatment of primary endothelial cells and primary B cells using RNA sequencing. To understand how 25HC inhibits KSHV infection, we examined global gene expression changes induced by 25HC in HUVECs, with or without KSHV infection. We pre-treated HUVEC with 25HC or vehicle control, then infected with KSHV (four conditions: -/+ 25HC, -/+ infection). At 2 days post-infection (dpi), we harvested RNA and performed RNA-seq to determine differentially expressed genes. We found that 25HC treatment inhibited KSHV gene expression globally and induced several inflammatory cytokines (CXCL8, IL1?), AP-1 components, and innate immunity receptors (RIG-I, TLR2) . Likewise, we also observed 25HC to block EBV de novo infection by inducing apoptosis and blocking transformation into lymphoblastoid cell lines. To determine transcriptomic changes that contributes to this, we purified B cells from healthy donors and infected them with EBV after 25HC pre-treatment with 4 similar conditions mentioned above. Samples were sent for RNA-Seq at 10-12 dpi. In contrast to KSHV infection, we found that only a subset of EBV viral transcripts are downregulated in the 25HC-treated samples. LMP1, which is the primary oncogenic factor, was suppressed and several downstream host targets that would prevent apoptosis during infection were likewise dysregulated. Additionally, several viral noncoding RNAs were also highly downregulated. Further analyses revealed that some 25HC-induced genes in our KSHV data set overlap with antiviral genes that were previously identified in various published screens involving other viruses, demonstrating the broad activity of 25HC. Together, these results answer some important questions about a widely acting antiviral (25HC), with implications for multiple viral and bacterial infections.

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25-Hydroxycholesterol Inhibits Kaposi's Sarcoma Herpesvirus and Epstein-Barr Virus Infections and Activates Inflammatory Cytokine Responses.

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