KSHV uses viral IL6 to expand infected immunosuppressive macrophages (scRNA-seq)
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. Overall design: The goal of this study was to define the specific peripheral blood mononuclear cell (PBMC) cell types or lineages that are susceptible to infection by KSHV. To this end, recombinant KSHV (rKSHV.291) virions were purified from the culture supernatant of the iSLK.291 producer cell line. PBMCs were infected with rKSHV.291 at a multiplicity of infection (MOI)=1, fixed at various time points (day 0, 1, 2, and 4) after infection, and subjected to scRNA-seq analysis. KSHV infection and lytic replication in individual single cells were then monitored by the expression of the KSHV K2 gene that encodes vIL6.