Type 2 Cytokines Predominate in the Human CD4 + T-Lymphocyte Response to Epstein-Barr Virus Nuclear Antigen 1

Section: Characterization Of Cytotoxic Cd4mentioning

confidence: 87%

Cytolytic CD4⁺-T-Cell Clones Reactive to EBNA1 Inhibit Epstein-Barr Virus-Induced B-Cell Proliferation

Nikiforow

Bottomly²,

Miller

et al. 2003

“…Most in vitro studies to date have focused on CD4 ϩ T-cell responses to just one of the available latent proteins, EBNA1 (9,13,17,27,32) and, even when studying responses to the same epitope (9,17), have reported discordant results with respect to LCL recognition. To address this issue in a more systematic way, the present work set out to identify CD4 epitopes in a broader range of latent-cycle antigens, EBNA1, -2, -3A, and -3C, and then to generate CD4 ϩ T-cell clones to a representative panel of epitopes drawn from these four proteins.…”

Section: Discussionmentioning

confidence: 99%

“…Of these, only the EBNA2-specific clone appeared to be capable of recognizing LCLs directly in cytotoxicity assays (10). Since that time, CD4 ϩ recall responses to more latent-cycle epitopes have been generated by a variety of protocols, many involving in vitro stimulation with dendritic cells either overexpressing antigen from vaccinia virus vectors or preloaded with exogenous antigen or with epitope peptides (13,17,21,27,32). Although these clones display specificity for antigen in protein loading assays, there are differing reports of their ability to recognize LCLs naturally expressing cognate antigen from the resident EBV genome.…”

mentioning

confidence: 99%

CD4⁺T-Cell Responses to Epstein-Barr Virus (EBV) Latent-Cycle Antigens and the Recognition of EBV-Transformed Lymphoblastoid Cell Lines

Long

Haigh

Gudgeon

et al. 2005

111

163

There is considerable interest in the potential of Epstein-Barr virus (EBV) latent antigen-specific CD4؉ T cells to act as direct effectors controlling EBV-induced B lymphoproliferations. Such activity would require direct CD4؉ T-cell recognition of latently infected cells through epitopes derived from endogenously expressed viral proteins and presented on the target cell surface in association with HLA class II molecules. It is therefore important to know how often these conditions are met. Here we provide CD4؉ epitope maps for four EBV nuclear antigens, EBNA1, -2, -3A, and -3C, and establish CD4 ؉ T-cell clones against 12 representative epitopes. For each epitope we identify the relevant HLA class II restricting allele and determine the efficiency with which epitope-specific effectors recognize the autologous EBV-transformed B-lymphoblastoid cell line (LCL). The level of recognition measured by gamma interferon release was consistent among clones to the same epitope but varied between epitopes, with values ranging from 0 to 35% of the maximum seen against the epitope peptide-loaded LCL. These epitope-specific differences, also apparent in short-term cytotoxicity and longer-term outgrowth assays on LCL targets, did not relate to the identity of the source antigen and could not be explained by the different functional avidities of the CD4 ؉ clones; rather, they appeared to reflect different levels of epitope display at the LCL surface. Thus, while CD4 ؉ T-cell responses are detectable against many epitopes in EBV latent proteins, only a minority of these responses are likely to have therapeutic potential as effectors directly recognizing latently infected target cells.

“…Very little information had come from LCL-stimulated populations in that regard, the available evidence being limited to rare CD4 ϩ T-cell clones specific for one EBNA1-derived and one EBNA2-derived epitope (16,17). Alternative approaches, however, based on stimulating CD8-depleted PBMCs either with peptide panels, purified antigen, or antigen expressed in autologous dendritic cells, have generated polyclonal or clonal populations of CD4 ϩ T cells specific for the relevant antigen/epitope (22,30,35,36,42,49). Most attention has been given to EBNA1-specific responses (30,36,49), but it is now clear that CD4…”

Section: T-cell Memory To Epstein-barr Virus (Ebv) Was First Demonstrmentioning

confidence: 99%

Regression of Epstein-Barr Virus-Induced B-Cell Transformation In Vitro Involves Virus-Specific CD8⁺T Cells as the Principal Effectors and a Novel CD4⁺T-Cell Reactivity

Gudgeon

Taylor

Long

et al. 2005

T-cell memory to Epstein-Barr virus (EBV) was first demonstrated through regression of EBV-induced B-cell transformation to lymphoblastoid cell lines (LCLs) in virus-infected peripheral blood mononuclear cell (PBMC)cultures. Here, using donors with virus-specific T-cell memory to well-defined CD4 and CD8 epitopes, we reexamine recent reports that the effector cells mediating regression are EBV latent antigen-specific CD4 ؉ and not, as previously assumed, CD8؉ T cells. In regressing cultures, we find that the reversal of CD23 ؉ B-cell proliferation was always coincident with an expansion of latent epitope-specific CD8؉ , but not CD4 ؉ , T cells; furthermore CD8؉ T-cell clones derived from regressing cultures were epitope specific and reproduced regression when cocultivated with EBV-infected autologous B cells. In cultures of CD4-depleted PBMCs, there was less efficient expansion of these epitope-specific CD8 ؉ T cells and correspondingly weaker regression. The data are consistent with an effector role for epitope-specific CD8 ؉ T cells in regression and an auxiliary role for CD4؉ T cells in expanding the CD8 response. However, we also occasionally observed late regression in CD8-depleted PBMC cultures, though again without any detectable expansion of preexisting epitope-specific CD4 ؉ T-cell memory. CD4 ؉ T-cell clones derived from such cultures were LCL specific in gamma interferon release assays but did not recognize any known EBV latent cycle protein or derived peptide. A subset of these clones was also cytolytic and could block LCL outgrowth. These novel effectors, whose antigen specificity remains to be determined, may also play a role in limiting virus-induced B-cell proliferation in vitro and in vivo.Epstein-Barr virus (EBV) is a human B lymphotropic herpesvirus that has cell growth transforming ability in vitro yet is carried by the great majority of immunocompetent individuals as a lifelong asymptomatic infection. The importance of T-cellmediated immune responses in maintaining asymptomatic persistence is emphasized by clinical observation. Thus, patients who are severely T-cell immunosuppressed either iatrogenically or through progressive human immunodeficiency virus (HIV) infection are at risk of developing fatal EBV-associated lymphoproliferative lesions (11,32,37). These lesions are largely composed of EBV-transformed B cells expressing the same panel of latent cycle proteins (the nuclear antigens EBNAs 1, 2, 3A, 3B, 3C, and LP and the latent membrane proteins [LMPs] 1 and 2), as do the lymphoblastoid cell lines (LCLs) that arise by EBV-induced transformation of normal resting B cells in vitro (8,12,54).The ready availability of such latently infected LCLs provided stimulator cells which, when cocultured at particular ratios with autologous peripheral blood mononuclear cells (PBMCs), were able to reactivate T-cell memory and generate EBV latent antigen-specific, interleukin 2 (IL-2)-dependent, T-cell lines (39, 51). These lines, which kill the autologous LCL in short-term cytotoxicity assays, tend to...