T Cell Epitope Clustering in the Highly Immunogenic BZLF1 Antigen of Epstein-Barr Virus

Abstract

Polymorphism in the human leukocyte antigen (HLA) loci ensures that the CD8؉ T cell response to viruses is directed against a diverse range of antigenic epitopes, thereby minimizing the impact of virus escape mutation across the population. The BZLF1 antigen of Epstein-Barr virus is an immunodominant target for CD8 ؉ T cells, but the response has been characterized only in the context of a limited number of HLA molecules due to incomplete epitope mapping. We have now greatly expanded the number of defined CD8 ؉ T cell epitopes from BZLF1, allowing the response to be evaluated in a much larger proportion of the population. Some regions of the antigen fail to be recognized by CD8 ؉ T cells, while others include clusters of overlapping epitopes presented by different HLA molecules. These highly immunogenic regions of BZLF1 include polymorphic sequences, such that up to four overlapping epitopes are impacted by a single amino acid variation common in different regions of the world. This focusing of the immune response to limited regions of the viral protein could be due to sequence similarity to human proteins creating "immune blind spots" through self-tolerance. This study significantly enhances the understanding of the immune response to BZLF1, and the precisely mapped T cell epitopes may be directly exploited in vaccine development and adoptive immunotherapy. IMPORTANCE Epstein-Barr virus (EBV) is an important human pathogen, associated with several malignancies, including nasopharyngeal carcinoma and Hodgkin lymphoma. T lymphocytes are critical for virus control, and clinical trials aimed at manipulating this armof the immune system have demonstrated efficacy in treating these EBV-associated diseases. These trials have utilized information on the precise location of viral epitopes for T cell recognition, for either measuring or enhancing responses. In this study, we have characterized the T cell response to the highly immunogenic BZLF1 antigen of EBV by greatly expanding the number of defined T cell epitopes. An unusual clustering of epitopes was identified, highlighting a small region of BZLF1 that is targeted by the immune response of a high proportion of the world's population. This focusing of the immune response could be utilized in developing vaccines/therapies with wide coverage, or it could potentially be exploited by the virus to escape the immune response.

Hepatitis D Virus-Specific CD8+ T Cells Have a Memory-Like Phenotype Associated With Viral Immune Escape in Patients With Chronic Hepatitis D Virus Infection

“…For example, the HBV core 18-27 FLPSDFFPSV epitope overlaps with the HLA-B*35:01 and HLA-B*51:01-restricted epitope LPSDFFPSV, 22 and EBV-specific CD8 + T-cell epitopes cluster in the BZLF1 region of the virus. 23 However, promiscuous binding of CD8 + T-cell epitopes to multiple HLA class I molecules is unusual. It is more commonly associated with CD4 T-cell epitopes, 24 as the HLA class II binding groove accommodates longer peptides.…”

Endo-lysosomal assembly variations among Human Leukocyte Antigen class I (HLA-I) allotypes

“…Two EBV proteins contain known epitopes for both B*08:01 (RAKFKQLL (RAK) and FLRGRAYGL (FLR)) and B*35:01 (EPLPQGQLTAY (EPL) and YPLHEQHGM (YPL)). The FLR and YPL epitopes are derived from the EBNA3A protein, and the RAK and EPL epitopes are derived from the BZLF1 protein (Thomson et al, 1995, Rist et al, 2015). We sorted and expanded antigen-specific CTLs with B*08:01-RAK, B*08:01-FLR, B*35:01-EPL, and B*35:01-YPL tetramers from donors expressing the relevant HLA-B allotypes (Group 3, Table S1 ).…”

“…Two EBV proteins contain known epitopes for both B*08:01 (RAKFKQLL (RAK) and FLRGRAYGL (FLR)) and B*35:01 (EPLPQGQLTAY (EPL) and YPLHEQHGM (YPL)). The FLR and YPL epitopes are derived from the EBNA3A protein, and the RAK and EPL epitopes are derived from the BZLF1 protein (Thomson et al, 1995, Rist et al, 2015. We To control for donor-to-donor antigen uptake and processing differences during cross-presentation assays, monocytes and moDCs were used from donors expressing both B*08:01 and B*35:01 so that antigen presentation via both allotypes occurs within the same cells (Group 4, Table S1).…”

The Role of the Epstein-Barr Virus Lytic Cycle in Tumor Progression: Consequences in Diagnosis and Therapy

“…From an immunologic standpoint, ZEBRA expression is thus likely to represent a prime target of adaptive immune responses (T-cell and humoral responses) ( Table 2). ZEBRA, highly immunogenic, elicits robust T-cell responses [10,[67][68][69][70][71][72] that dominate the early immune responses in patients [70]. B-cell epitopes were additionally described; to illustrate, the DNA-binding domain of ZEBRA (basic region, including the so-called RAK epitope) is a major target antigen for IgM antibody response in EBV primary infection (45), whereas the N-terminus part (activation domain) is mainly recognized by IgG in patients with EBV reactivation [35,[73][74][75].…”