Distinct memory CD4+ T-cell subsets mediate immune recognition of Epstein Barr virus nuclear antigen 1 in healthy virus carriers

Abstract

IntroductionThe human ␥-herpesvirus Epstein Barr virus (EBV) infects more than 90% of the adult population. Latent infection by EBV is associated with human cancers of epithelial and B-cell origin, including 95% of nasopharyngeal carcinoma 1 and 90% of endemic Burkitt lymphoma, and it is associated with 40% to 60% of Hodgkin lymphoma cases. 2 Although all latently infected B cells have the potential for malignant transformation, most carriers remain free of tumors due to an effective immune control of the virus. This becomes apparent in conditions of immune suppression. Increased frequencies of EBV-associated malignancies can be observed during immunosuppressive therapy 3 in patients with hereditary immunodeficiencies 4,5 or with immunocompromising coinfections like HIV-induced AIDS. 6 T cells are an essential part of EBV-specific immune control. This is evident from the successful treatment of posttransplantation lymphoproliferative disease (PTLD) with the adoptive transfer of EBV-specific T cells. 7,8 This study focuses on the CD4 ϩ T-cell response of healthy virus carriers to the latent EBV antigen Epstein-Barr nuclear antigen 1 (EBNA1), which is expressed in all EBV-associated malignancies. Maintenance of EBNA1 expression is due to its crucial function in viral persistence within proliferating cells. EBV DNA only rarely integrates into the host-cell genome 9 and is carried as circular DNA episome by most latently EBVinfected cells. 10,11 The EBNA1 protein initiates replication of viral episomes prior to mitosis and anchors viral DNA to mitotic chromosomes during cell division. 12 By this mechanism, EBV replicates in proliferating cells without viral particle formation during latent EBV infection.EBNA1 should be a critical target of protective immunity because it is expressed in all EBV-positive proliferating cells and is crucial for viral persistence. However, earlier studies have emphasized escape of EBNA1 from CD8 ϩ T-cell detection due to an amino terminal gly-ala repeat domain. [13][14][15] Since it is consistently recognized by CD4 ϩ T cells in healthy EBV carriers, 16,17 it was appreciated that EBNA1 is a promising T-cell antigen to target EBV-transformed B cells. 18 EBNA1-specific effector CD4 ϩ T cells are primarily T-helper 1 (TH1) polarized, 19 can target EBVtransformed B cells, 16,[19][20][21] and prevent EBV-mediated B-cell transformation in vitro. 22 EBNA1-specific CD4 ϩ T cells can also mediate rejection of EBNA1-positive Burkitt lymphoma transplanted into mice. 23 Recently, EBNA1-specific CD8 ϩ T cells, in association with a few HLA class I haplotypes, have also been reported to recognize EBV-transformed B cells [24][25][26] and to prevent their outgrowth in vitro. 25 Therefore, both EBNA1-specific CD4 ϩ and CD8 ϩ T cells are able to recognize EBV-transformed cells and deserve to be studied in more detail.In this study, we characterized EBNA1-specific CD4 ϩ T cells in healthy EBV carriers by flow cytometry-based intracellular cytokine staining and proliferation assays, using an overlapping pep...

Human peripheral blood and bone marrow Epstein–Barr virus‐specific T‐cell repertoire in latent infection reveals distinct memory T‐cell subsets

“…Our findings suggest that the differentiation model of Seder et al can also be extended to CD8 1 T cells, in which similarly TNF single or TNF/IL-2 double memory T cells showed the highest CCR7 expression. In line with our findings two previous studies could show that EBV-specific CCR7 1 CD4 1 and CD8 1 T cells are detectable in PB and predominately express IL-2 (Amyes et al [52] and Mallard et al [54]) and a study by Heller et al [55] showed the presence of EBNA-specific CD62L 1 T cells in PB. By sorting EBV-specific T cells based on CCR7 expression we could confirm and extend previous studies [30,52,56] showing that the CCR7 1 central memory T cells serve as reservoir for EBV-specific effector T cells (Fig.…”

CCR2 Identifies a Stable Population of Human Effector Memory CD4+ T Cells Equipped for Rapid Recall Response

“…2 subset, which is consistent with published data for both CD8 + and CD4 + T cells, showing that anti-EBV cells are less differentiated than anti-CMV cells (9,45,66 (68) or during acute infection with EBV or HIV-1 (69-71). Our finding that, among the agents tested, CMV elicited the greatest responses in the CD127 2 cells, which are relatively abundant in the CCR5 + CCR2 2 subset, is consistent with previous data (58), and suggested that CMV was the virus most often (re)stimulating a systemic immune response.…”

Age-associated Epstein–Barr virus-specific T cell responses in seropositive healthy adults

“…Overall, based on these assays, the reported frequency of CD8 + T lymphocytes against EBV latent and lytic-stage antigens is < 2% [25,[34][35][36], and that of CD4 + T lymphocytes is typically ∼1% [2,31,32,37]. EBVspecific T cells are described as monofunctional populations secreting interferon (IFN)-γ [4,34,[38][39][40][41][42][43][44] and multifunctional cells producing tumour necrosis factor (TNF)-α, IFN-γ and interleukin (IL)-2 [12,30,31,33,37,38,45] in addition to perforin, CD107a and macrophage inflammatory protein (MIP)-1α (CCL3) [45,46]. In contrast, among individuals aged > 50 years, the results regarding anti-EBV T-cell responses in vitro are controversial.…”