Lytic Replication and Reactivation from B Cells Is Not Required for Establishing or Maintaining Gammaherpesvirus Latency In Vivo

• Published in: Journal of virology 2022-06, Vol.96 (12), p.e0069022-e0069022
• Main Authors: Gupta, Arundhati, Owens, Shana M, Oldenburg, Darby G, White, Douglas W, Forrest, J Craig
• Format: Article
• Language: English
• Subjects: Animals; B-Lymphocytes - virology; Gammaherpesvirinae - genetics; Gammaherpesvirinae - physiology; Herpesviridae Infections - virology; Immediate-Early Proteins - genetics; Mice; Mice, Inbred C57BL; Pathogenesis and Host Response; Pathogenesis and Immunity; Virus Activation; Virus Latency; Virus Replication
• ISSN: 0022-538X; 1098-5514
• DOI: 10.1128/jvi.00690-22

Gammaherpesviruses (GHVs) are lymphotropic tumor viruses with a biphasic infectious cycle. Lytic replication at the primary site of infection is necessary for GHVs to spread throughout the host and establish latency in distal sites. Dissemination is mediated by infected B cells that traffic hematogenously from draining lymph nodes to peripheral lymphoid organs, such as the spleen. B cells serve as the major reservoir for viral latency, and it is hypothesized that periodic reactivation from latently infected B cells contributes to maintaining long-term chronic infection. While fundamentally important to an understanding of GHV biology, aspects of B cell infection in latency establishment and maintenance are incompletely defined, especially roles for lytic replication and reactivation in this cell type. To address this knowledge gap and overcome limitations of replication-defective viruses, we generated a recombinant murine gammaherpesvirus 68 (MHV68) in which , the gene that encodes the essential immediate-early replication and transcription activator protein (RTA), was flanked by sites to enable conditional ablation of lytic replication by deletion in cells that express Cre recombinase. Following infection of mice that encode Cre in B cells with this virus, splenomegaly and viral reactivation from splenocytes were significantly reduced; however, the number of latently infected splenocytes was equivalent to WT MHV68. Despite deletion, MHV68 latency was maintained over time in spleens of mice at levels approximating WT, reactivation-competent MHV68. Treatment of infected mice with lipopolysaccharide (LPS), which promotes B cell activation and MHV68 reactivation , yielded equivalent increases in the number of latently infected cells for both -deleted and WT MHV68, even when mice were simultaneously treated with the antiviral drug cidofovir to prevent reactivation. Together, these data demonstrate that productive viral replication in B cells is not required for MHV68 latency establishment and support the hypothesis that B cell proliferation facilitates latency maintenance in the absence of reactivation. Gammaherpesviruses establish lifelong chronic infections in cells of the immune system and place infected hosts at risk for developing lymphomas and other diseases. It is hypothesized that gammaherpesviruses must initiate acute infection in these cells to establish and maintain long-term infection, but this has not been directly tested. We report here the use o