Epstein-Barr virus (EBV)–encoded small RNA is released from EBV-infected cells and activates signaling from toll-like receptor 3

Abstract

Epstein-Barr virus–encoded small RNA (EBER) is nonpolyadenylated, noncoding RNA that forms stem-loop structure by intermolecular base-pairing, giving rise to double-stranded RNA (dsRNA)–like molecules, and exists abundantly in EBV-infected cells. Here, we report that EBER induces signaling from the Toll-like receptor 3 (TLR3), which is a sensor of viral double-stranded RNA (dsRNA) and induces type I IFN and proinflammatory cytokines. A substantial amount of EBER, which was sufficient to induce signaling from TLR3, was released from EBV-infected cells, and the majority of the released EBER existed as a complex with a cellular EBER-binding protein La, suggesting that EBER was released from the cells by active secretion of La. Sera from patients with infectious mononucleosis (IM), chronic active EBV infection (CAEBV), and EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH), whose general symptoms are caused by proinflammatory cytokines contained EBER, and addition of RNA purified from the sera into culture medium induced signaling from TLR3 in EBV-transformed lymphocytes and peripheral mononuclear cells. Furthermore, DCs treated with EBER showed mature phenotype and antigen presentation capacity. These findings suggest that EBER, which is released from EBV-infected cells, is responsible for immune activation by EBV, inducing type I IFN and proinflammatory cytokines. EBER-induced activation of innate immunity would account for immunopathologic diseases caused by active EBV infection.

Silencing the shutoff protein of Epstein–Barr virus in productively infected B cells points to (innate) targets for immune evasion

“…TLR2, 3 and 9 sense EBV particles (Gaudreault et al, 2007;Iwakiri et al, 2009;van Gent et al, 2011), yet no evidence for TLR4-mediated recognition of EBV has been reported (Gaudreault et al, 2007). Here, we monitored the influence of BGLF5 on TLR2 and TLR4.…”

Lactoferrin suppresses the Epstein–Barr virus-induced inflammatory response by interfering with pattern recognition of TLR2 and TLR9

“…Several TLRs, including TLR2, TLR3, and TLR9, participate in recognition of EBV by monocytes/macrophages and dendritic cells. 5,7,11,12 Gaudreault et al 7 revealed that stimulation of monocytes with EBV virions leads to the release of MCP-1 and IL-8 through the activation of TLR2. 7 TLR2 recognizes glycoproteins of the viral envelope, resulting in the activation of NF-kB signaling and production of these inflammatory cytokines.…”

“…10 Several reports have demonstrated that human TLRs can recognize EBV. 5,7,11,12 Stimulation of human monocytes with either inactivated or infectious EBV virions leads to the release of MCP-1 and to an increase of several cytokine mRNA levels, including IL-8, through the engagement of the cell surface TLR2. 7 More recently, TLR9 was found to contribute to the recognition of EBV DNA in primary monocytes, leading to an increased release of IL-8.…”

Epstein-Barr Virus-Associated Classical Hodgkin Lymphoma and Its Therapeutic Strategies

“…It was demonstrated that EBERs induce expression of type-I IFNs by binding to the retinoic acid-inducible gene I (RIG-I) product that is a cytosolic protein that recognizes viral dsRNA inside the cell (Samanta et al, 2006). Another evidence of a role of EBERs in innate immunity is their binding to Toll-like receptor 3 after secreted from EBV-infected cells (Iwakiri et al, 2009;Iwakiri and Takada, 2010), triggering innate immunity that might explain immunopathologic diseases caused by active EBV infection. However, EBERs also induce an anti-infl ammatory cytokine, IL-10, through RIG-1-mediated interferon regulatory factor (IRF) 3 (Samanta et al, 2008), suggesting that modulation of innate immune signaling by EBERs may contribute to EBVmediated oncogenesis.…”

“…Nt (Ho et al, 1999;Komano et al, 1999;Kitagawa et al, 2000;Yamamoto et al., 2000;Iwakiri et al, 2003;Iwakiri et al, 2005;Samanta et al, 2006;Samanta et al, 2008;Iwakiri et al, 2009;Iwakiri and Takada, 2010 Immunization with LMP1 gene or polyepitope expression vectors Taylor et al, 2004;Smith et al, 2006;Pan et al, 2009;Lutzky et al, 2010;Chia et al, Immunization with LMP2A gene or polyepitope expression vectors (Taylor et al, 2004;Smith et al, 2006;Pan et al, 2009;Lutzky et al, 2010;Chia et al, 2011) LMP2B Modulation of innate immune response nt TLR: Toll-like receptor, RIG: retinoic acid-inducible gene, PKR: RNA-dependent protein kinase, Nt: not tested, CTL: cytotoxic T lymphocyte, DC: dendritic cells.…”