CD4 and CD8 T Cells Directly Recognize Murine Gammaherpesvirus 68-Immortalized Cells and Prevent Tumor Outgrowth

Abstract

There has been extensive research regarding T cell recognition of Epstein-Barr virus-transformed cells; however, less is known regarding the recognition of B cells immortalized by gamma-2 herpesviruses. Here we show that B cells immortalized by murine gammaherpesvirus 68 (MHV-68, ␥HV-68) can be controlled by either CD4 or CD8 T cells in vivo. We present evidence for the direct recognition of infected B cells by CD4 and CD8 T cells. These data will help in the development of immunotherapeutic approaches combating gamma-2 herpesvirus-related disease.T cell immunity is critical to control virus replication and latently infected cells in most herpesvirus infections. Using the murine gammaherpesvirus 68 (MHV-68, ␥HV-68) mouse model of gamma-2 herpesvirus infection, we now have a good understanding of the immunological factors necessary to control virus replication (1-9). However, we have a much poorer understanding of T cell recognition of latently infected B cells. This has been due largely to our inability to immortalize B cells by MHV-68 infection in vitro. However, our recently published work describes a methodology by which immature B cells can be immortalized by MHV-68 (10). These cells grow as tumors in immunodeficient mice but not immunocompetent mice, indicating immunological control of the outgrowth of MHV-68-infected B cells (10). To determine the key cell types responsible for this protection, we used an adoptive transfer system. We transferred purified T lymphocytes, B lymphocytes, or both T and B lymphocytes from naïve mice into RAG2 Ϫ/Ϫ mice. MHV-68-immortalized SL1 cells were then injected into the mice, and tumor growth was monitored. In mice receiving no T cells or only B cells, the tumor grew to a size necessitating euthanasia by approximately 30 to 40 days postinjection (Fig. 1A). However, mice receiving either T cells alone or T and B cells survived for Ͼ150 days postinjection with no tumor growth (Fig. 1B). These data indicated that T cells were the predominant cells responsible for mediating protection against the outgrowth of MHV-68-immortalized tumor cells. Importantly, we did not observe virus reactivation from SL1 cells after injection in vivo, as no viral spread to the host was detectable, measured by PCR for the viral genome in the spleens of wild-type or RAG2 Ϫ/Ϫ mutant mice injected with SL1 cells (data not shown).Next, we adoptively transferred purified CD8 or CD4 T cells into RAG2Ϫ/Ϫ mutant mice, injected them with SL1 cells, and 001). (C) RAG2Ϫ/Ϫ mutant mice received SL1 cells and T cells (Pan T), CD4 T cells, CD8 T cells, or a PBS control. Cells were isolated by negative selection by magnetic cell separation. The control group received PBS buffer only (n ϭ 10; log-rank test; ***, P Ͻ 0.001).

LXR Alpha Restricts Gammaherpesvirus Reactivation from Latently Infected Peritoneal Cells

“…In addition to CD8 ϩ T cells, CD4 ϩ T cells are important for the control of chronic MHV68 infection (37)(38)(39) and are capable of producing IFN-␥ in response to the MHC class II peptide gp150 67-83 as long as 8 months after infection (40). Stimulation with gp150 67-83 produced a measurable IFN-␥ response from splenic CD4 ϩ T cells (see Fig.…”

“…MHV68-specific CD8 ϩ and CD4 ϩ T cells are critical for the control of chronic MHV68 infection and reactivation (29,30,37,(51)(52)(53), and T cell deficiency is a well-defined risk factor for gammaherpesvirus-driven malignancies (8,38,54). To probe trans-acting LXR␣ mechanisms, we examined the generation of MHV68-specific CD8 ϩ and CD4 ϩ effector T cells and their recruitment to the peritoneal cavity and found no LXR␣dependent effects.…”

CD4 T Cells Specific for a Latency-Associated γ-Herpesvirus Epitope Are Polyfunctional and Cytotoxic

“…Cytotoxic CD4 T cells specific for latent epitopes may be important because the majority of tumor cells sustain a latent infection whereas non-cytotoxic, cytokine-secreting lytic epitope-specific CD4 T cells may be crucial for targeting cells harboring reactivating virus to prevent full recrudescence. As CD4 T cells are capable of mediating protection in two models of γHV68-associated tumors (36, 37), it will be of particular interest to investigate the protective efficacy of latency-specific cytotoxic CD4 T cells in these systems.…”

Type I Interferon Signaling Enhances CD8+T Cell Effector Function and Differentiation during Murine Gammaherpesvirus 68 Infection

“…ϩ T cells prevent in vivo tumor outgrowth of B cell cancer lines immortalized by murine gammaherpesvirus 68 (MHV68), a wellcharacterized virus model for EBV (6). Thus, CD8…”