Project description:Kaposi’s sarcoma-associated herpesvirus (KSHV) is an oncogenic double-stranded DNA virus and the etiologic agent of Kaposi’s sarcoma and hyperinflammatory lymphoproliferative disorders. Understanding the mechanism by which KSHV increases infected cell populations is crucial for curing KSHV-associated diseases. Here, we demonstrate that KSHV preferentially infects CD14+ monocytes and sustains viral replication through the viral interleukin-6 (vIL-6)-mediated activation of STAT1 and 3. Using vIL6-sufficient and vIL6-deficient recombinant KSHV, we demonstrated that vIL6 plays a critical role in promoting the proliferation and differentiation of KSHV-infected monocytes into macrophages. The macrophages derived from vIL6-sufficient (wild type) KSHV infection showed a distinct transcriptional profile of elevated IFN-pathway activation with immune suppression and were compromised in T-cell stimulation function compared to those from vIL6-deficient KSHV infection or uninfected control. These results highlight a clever strategy, in which KSHV utilizes vIL6 to secure its initial viral pool by expanding infected dysfunctional macrophages. This mechanism also facilitates KSHV to escape from host immune surveillance and to establish a lifelong infection.
Project description:Kaposi’s sarcoma-associated herpesvirus (KSHV) is an oncogenic double-stranded DNA virus and the etiologic agent of Kaposi’s sarcoma and hyperinflammatory lymphoproliferative disorders. Understanding the mechanism by which KSHV increases infected cell populations is crucial for curing KSHV-associated diseases. Here, we demonstrate that KSHV preferentially infects CD14+ monocytes and sustains viral replication through the viral interleukin-6 (vIL-6)-mediated activation of STAT1 and 3. Using vIL6-sufficient and vIL6-deficient recombinant KSHV, we demonstrated that vIL6 plays a critical role in promoting the proliferation and differentiation of KSHV-infected monocytes into macrophages. The macrophages derived from vIL6-sufficient (wild type) KSHV infection showed a distinct transcriptional profile of elevated IFN-pathway activation with immune suppression and were compromised in T-cell stimulation function compared to those from vIL6-deficient KSHV infection or uninfected control. These results highlight a clever strategy, in which KSHV utilizes vIL6 to secure its initial viral pool by expanding infected dysfunctional macrophages. This mechanism also facilitates KSHV to escape from host immune surveillance and to establish a lifelong infection.
Project description:Primary effusion lymphoma (PEL) is caused by Kaposi's sarcoma-associated herpesvirus (KSHV) and frequently also harbors Epstein-Barr virus (EBV). The expression of KSHV- and EBV-encoded microRNAs (miRNAs) in PELs suggests a role for these miRNAs in latency and lymphomagenesis. Using PAR-CLIP, a technology which allows the direct and transcriptome-wide identification of miRNA targets, we delineate the target sites for all viral and cellular miRNAs expressed in PEL cell lines. The resulting data set revealed that KSHV miRNAs directly target more than 2000 cellular mRNAs, including many involved in pathways relevant to KSHV pathogenesis. Moreover, 58% of these mRNAs are also targeted by EBV miRNAs, via distinct binding sites. In addition to a known viral analog of cellular miR-155, we show that KSHV encodes a viral miRNA that mimics cellular miR-142-3p function. In summary, this study identifies an extensive list of KSHV miRNA targets, which are likely to influence viral replication and pathogenesis.
Project description:Phosphorylation of sphingosine by sphingosine kinases (SphK1 and SphK2) generates sphingosine-1-phosphate (S1P), a bioactive sphingolipid which promotes cancer cell survival and tumor progression in vivo. We have recently reported that targeting SphK2 induces apoptosis for human primary effusion lymphoma (PEL) cell lines infected by the Kaposi's sarcoma-associated herpesvirus (KSHV), and this occurs in part through inhibition of canonical NF-?B activation. In contrast, pharmacologic inhibition of SphK2 has minimal impact for uninfected B-cell lines or circulating human B cells from healthy donors. Therefore, we designed additional studies employing primary human endothelial cells to explore mechanisms responsible for the selective death observed for KSHV-infected cells during SphK2 targeting. Using RNA interference and a clinically relevant pharmacologic approach, we have found that targeting SphK2 induces apoptosis selectively for KSHV-infected endothelial cells through induction of viral lytic gene expression. Moreover, this effect occurs through repression of KSHV-microRNAs regulating viral latency and signal transduction, including miR-K12-1 which targets I?B? to facilitate activation of NF-?B, and ectopic expression of miR-K12-1 restores NF-?B activation and viability for KSHV-infected endothelial cells during SphK2 inhibition. These data illuminate a novel survival mechanism and potential therapeutic target for KSHV-infected endothelial cells: SphK2-associated maintenance of viral latency.
