title: Cooperation between Epstein-Barr virus immune evasion proteins spreads protection from CD8+ T cell recognition across all three phases of the lytic cycle.
abstract: CD8+ T cell responses to Epstein-Barr virus (EBV) lytic cycle expressed antigens display a hierarchy of immunodominance, in which responses to epitopes of immediate-early (IE) and some early (E) antigens are more frequently observed than responses to epitopes of late (L) expressed antigens. It has been proposed that this hierarchy, which correlates with the phase-specific efficiency of antigen presentation, may be due to the influence of viral immune-evasion genes. At least three EBV-encoded genes, BNLF2a, BGLF5 and BILF1, have the potential to inhibit processing and presentation of CD8+ T cell epitopes. Here we examined the relative contribution of these genes to modulation of CD8+ T cell recognition of EBV lytic antigens expressed at different phases of the replication cycle in EBV-transformed B-cells (LCLs) which spontaneously reactivate lytic cycle. Selective shRNA-mediated knockdown of BNLF2a expression led to more efficient recognition of immediate-early (IE)- and early (E)-derived epitopes by CD8+ T cells, while knock down of BILF1 increased recognition of epitopes from E and late (L)-expressed antigens. Contrary to what might have been predicted from previous ectopic expression studies in EBV-negative model cell lines, the shRNA-mediated inhibition of BGLF5 expression in LCLs showed only modest, if any, increase in recognition of epitopes expressed in any phase of lytic cycle. These data indicate that whilst BNLF2a interferes with antigen presentation with diminishing efficiency as lytic cycle progresses (IE>E>>L), interference by BILF1 increases with progression through lytic cycle (IE<E<<L). Moreover, double-knockdown experiments showed that BILF1 and BNLF2a co-operate to further inhibit antigen presentation of L epitopes. Together, these data firstly indicate which potential immune-evasion functions are actually relevant in the context of lytic virus replication, and secondly identify lytic-cycle phase-specific effects that provide mechanistic insight into the immunodominance pattern seen for CD8+ T cell responses to EBV lytic antigens.
authors.affiliation: School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom.
authors.forename: Laura L
authors.initials: LL
authors.lastname: Quinn
authors.affiliation: School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom.
authors.forename: Jianmin
authors.initials: J
authors.lastname: Zuo
authors.affiliation: School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom.
authors.forename: Rachel J M
authors.initials: RJ
authors.lastname: Abbott
authors.affiliation: School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom.
authors.forename: Claire
authors.initials: C
authors.lastname: Shannon-Lowe
authors.affiliation: School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom.
authors.forename: Rosemary J
authors.initials: RJ
authors.lastname: Tierney
authors.affiliation: School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Hislop
authors.affiliation: School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom.
authors.forename: Martin
authors.initials: M
authors.lastname: Rowe
mesh_terms: D017951:Antigen Presentation / Q000276:immunology*; D015153:Blotting, Western; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D003851:Deoxyribonucleases / Q000276:immunology; D020031:Epstein-Barr Virus Infections / Q000276:immunology*; D055785:Gene Knockdown Techniques; D004854:Herpesvirus 4, Human / Q000276:immunology; D006801:Humans; D057131:Immune Evasion / Q000276:immunology*; D060888:Real-Time Polymerase Chain Reaction; D043562:Receptors, G-Protein-Coupled / Q000276:immunology; D014763:Viral Matrix Proteins / Q000276:immunology; D014764:Viral Proteins / Q000276:immunology
chemical_list: C495131:BILF1 protein, Epstein-Barr virus; C539239:BNLF21 protein, human herpesvirus 4; D043562:Receptors, G-Protein-Coupled; D014763:Viral Matrix Proteins; D014764:Viral Proteins; D003851:Deoxyribonucleases; C083203:deoxyribonuclease, Epstein-Barr virus