Immediate Early and Early Lytic Cycle Proteins Are Frequent Targets of the Epstein-Barr Virus–induced Cytotoxic T Cell Response

Abstract

Epstein-Barr virus (EBV), a human γ-herpesvirus, can establish both nonproductive (latent) and productive (lytic) infections. Although the CD8+ cytotoxic T lymphocyte (CTL) response to latently infected cells is well characterized, very little is known about T cell controls over lytic infection; this imbalance in our understanding belies the importance of virus-replicative lesions in several aspects of EBV disease pathogenesis. The present work shows that the primary CD8+ CTL response to EBV in infectious mononucleosis patients contains multiple lytic antigen-specific reactivities at levels at least as high as those seen against latent antigens; similar reactivities are also detectable in CTL memory. Clonal analysis revealed individual responses to the two immediate early proteins BZLF1 and BRLF1, and to three (BMLF1, BMRF1, and BALF2) of the six early proteins tested. In several cases, the peptide epitope and HLA-restricting determinant recognized by these CTLs has been defined, one unusual feature being the number of responses restricted through HLA-C alleles. The work strongly suggests that EBVreplicative lesions are subject to direct CTL control in vivo and that immediate early and early proteins are frequently the immunodominant targets. This contrasts with findings in α- and β-herpesvirus systems (herpes simplex, cytomegalovirus) where viral interference with the antigen-processing pathway during lytic infection renders immediate early and early proteins much less immunogenic. The unique capacity of γ-herpesvirus to amplify the viral load in vivo through a latent growth-transforming infection may have rendered these agents less dependent upon viral replication as a means of successfully colonizing their hosts.

Monocyte-Derived Dendritic Cells Generated After a Short-Term Culture with IFN-α and Granulocyte-Macrophage Colony-Stimulating Factor Stimulate a Potent Epstein-Barr Virus-Specific CD8+ T Cell Response

“…In fact, whereas similar high frequencies of T cells reactive to the BMLF-1 (GLC) epitope were obtained using IFN-DCs or IL-4-DCs as stimulators, the expansion of T cells specific for the gp350 epitope was promoted exclusively by IFNDCs. Several studies have demonstrated that responses to lytic cycle Ags, including BMLF-1, are detectable in CTL memory (21,30,31) and can dominate those to latent cycle Ags (32), as in the case of donor LL, whose basal frequency of T cells reactive against the BMLF-1 (GLC) epitope largely exceeded that of each latent cycle Ag reactivity tested. Moreover, BMLF-1 (GLC) epitope-specific T cells can be easily detected in sensitive ELISPOT assays by adding the corresponding peptide to total PBMCs as responders (30,32), indicating that relatively inefficient APCs, such as the IL-4-DCs used in this study, can stimulate T cells reactive to this immunodominant epitope.…”

“…ANOVA test paired with Tukey-Kramer comparison was used for calculating the significance of the differences in the survival times of mice. Table I reports the HLA typing of the three healthy EBV-seropositive donors and the sequence of the EBV peptides, known to be CTL epitopes (15)(16)(17)(18)(19)(20)(21)(22)(23), used in this study. In all the experiments described in this work, the DC preparations were generated from immunomagnetically purified CD14 ϩ monocytes by 3-day culture in GM-CSF and IFN (IFN-DCs) or IL-4 (IL-4-DCs).…”

A Shift in the Phenotype of Melan-A-Specific CTL Identifies Melanoma Patients with an Active Tumor-Specific Immune Response

“…Peptides synthesized by FMOC chemistry were: melan-A, ELAGIGILTV, a variant of the 26 -35 epitope, which binds better to HLA-A2 than the natural peptide due to an altered anchor residue, but which is recognized by the same CTL as the natural peptide (26); influenza, GILGFVFTL, the influenza matrix protein 58 -66 epitope (27); EBV, GLCTLVAML, the 280 -288 epitope from the lytic protein BMLF1 of EBV (28,29).…”

“…Expression libraries of tumor cDNAs showed that the target of these CTL was melan-A, a lineage-specific molecule also expressed on normal melanocytes (2,3). The dominant HLA-A2-restricted epitope of melan-A originally appeared to be melan-A [27][28][29][30][31][32][33][34][35] (AAGIGILTV) (4), but subsequent experiments showed melan-A 26 -35 (EAAGIGILTV) is also recognized by CTL, and binds better to HLA-A2 (5). Many laboratories have since found it relatively easy to generate CTL specific for this epitope from HLA-A2 ϩ melanoma patients (6,7), and it therefore seemed that melan-A 26/7-35 might be the most commonly recognized epitope among all the known targets of melanoma Ag-specific CTL (6).…”

Large TCR Diversity of Virus-Specific CD8 T Cells Provides the Mechanistic Basis for Massive TCR Renewal after Antigen Exposure

“…Although the mechanisms have not been clearly established (reviewed in Refs. 4,5), the limited pattern of epitopes recognized among the large number of potent immunogenic epitopes encoded by viruses (immunodominant epitopes) is an important factor for the limitation of the TCR repertoire diversity (6)(7)(8)(9). Furthermore, in several situations, certain virus epitopes recruited a low number of clonotypes (reviewed in Ref.…”