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Endogenous presentation of CD8+ T cell epitopes from Epstein-Barr virus-encoded nuclear antigen 1.

Tellam J, Connolly G, Green KJ, Miles JJ, Moss DJ, Burrows SR, Khanna R - J. Exp. Med. (2004)

Bottom Line: However, these different degradation rates do not correspond to the level of major histocompatibility complex class I-restricted presentation of EBNA1 epitopes.Functional assays revealed that processing of these EBNA1 epitopes is proteasome and transporter associated with antigen processing dependent.Based on these observations, we propose that defective ribosomal products, not the full-length antigen, are the primary source of endogenously processed CD8+ T cell epitopes from EBNA1.

View Article: PubMed Central - PubMed

Affiliation: EBV Unit, Tumour Immunology Laboratory, Division of Infectious Diseases and Immunology, Queensland Institute of Medical Research, 300 Herston Road, Brisbane (Qld) 4006, Australia.

ABSTRACT
Epstein-Barr virus (EBV)-encoded nuclear antigen (EBNA)1 is thought to escape cytotoxic T lymphocyte (CTL) recognition through either self-inhibition of synthesis or by blockade of proteasomal degradation by the glycine-alanine repeat (GAr) domain. Here we show that EBNA1 has a remarkably varied cell type-dependent stability. However, these different degradation rates do not correspond to the level of major histocompatibility complex class I-restricted presentation of EBNA1 epitopes. In spite of the highly stable expression of EBNA1 in B cells, CTL epitopes derived from this protein are efficiently processed and presented to CD8+ T cells. Furthermore, we show that EBV-infected B cells can readily activate EBNA1-specific memory T cell responses from healthy virus carriers. Functional assays revealed that processing of these EBNA1 epitopes is proteasome and transporter associated with antigen processing dependent. We also show that the endogenous presentation of these epitopes is dependent on the newly synthesized protein rather than the long-lived stable EBNA1. Based on these observations, we propose that defective ribosomal products, not the full-length antigen, are the primary source of endogenously processed CD8+ T cell epitopes from EBNA1.

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Related in: MedlinePlus

Ex vivo intracellular IFN-γ production by EBNA1-specific T cells after stimulation with LCLs. PBMCs from an HLA B35+ donor were incubated alone (A) or with autologous LCL (B), 0.221.B35 LCL (C), HLA B35− LCL (D), or 0.221 LCL (E). Samples shown were gated on the CD8+ population, and then the percentage of CD8+ and HPV tetramer+ cells that were producing IFN-γ was assessed. The percentage of HPV-specific T cells producing IFN-γ after LCL stimulation is shown on the top right hand corner of each of the panels. These data are a representation of two separate experiments.
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fig4: Ex vivo intracellular IFN-γ production by EBNA1-specific T cells after stimulation with LCLs. PBMCs from an HLA B35+ donor were incubated alone (A) or with autologous LCL (B), 0.221.B35 LCL (C), HLA B35− LCL (D), or 0.221 LCL (E). Samples shown were gated on the CD8+ population, and then the percentage of CD8+ and HPV tetramer+ cells that were producing IFN-γ was assessed. The percentage of HPV-specific T cells producing IFN-γ after LCL stimulation is shown on the top right hand corner of each of the panels. These data are a representation of two separate experiments.

Mentions: To further confirm these observations, we established an ex vivo stimulation assay, in which PBMCs from three unrelated HLA B35–seropositive individuals were stimulated with autologous LCLs, 721.221 LCL, 721.221 LCL transfected with HLA B*3501 (referred to as 0.221.B*3501 LCL), or HLA B35− LCLs. After overnight incubation, these cells were assessed for binding to an HPV-HLA B*3501 tetramer and intracellular IFN-γ expression. Data presented in Fig. 4 clearly demonstrate that a large proportion of HPV-HLA B*3501 tetramer+ T cells showed strong intracellular IFN-γ expression after stimulation with autologous LCL or the 0.221.B*3501 LCL. On the other hand, no ex vivo IFN-γ response was observed within the HPV tetramer+ cells when the PBMCs were stimulated with the HLA B35− LCLs or left unstimulated. A similar pattern of IFN-γ response was also observed in other donors when stimulated with HLA B35+ LCLs (not depicted) These observations further confirm our conclusions drawn from Fig. 3, which indicated that EBV-infected B cells can endogenously process and present CTL epitopes directly to the virus-specific T cells.


Endogenous presentation of CD8+ T cell epitopes from Epstein-Barr virus-encoded nuclear antigen 1.

Tellam J, Connolly G, Green KJ, Miles JJ, Moss DJ, Burrows SR, Khanna R - J. Exp. Med. (2004)

Ex vivo intracellular IFN-γ production by EBNA1-specific T cells after stimulation with LCLs. PBMCs from an HLA B35+ donor were incubated alone (A) or with autologous LCL (B), 0.221.B35 LCL (C), HLA B35− LCL (D), or 0.221 LCL (E). Samples shown were gated on the CD8+ population, and then the percentage of CD8+ and HPV tetramer+ cells that were producing IFN-γ was assessed. The percentage of HPV-specific T cells producing IFN-γ after LCL stimulation is shown on the top right hand corner of each of the panels. These data are a representation of two separate experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2211806&req=5

fig4: Ex vivo intracellular IFN-γ production by EBNA1-specific T cells after stimulation with LCLs. PBMCs from an HLA B35+ donor were incubated alone (A) or with autologous LCL (B), 0.221.B35 LCL (C), HLA B35− LCL (D), or 0.221 LCL (E). Samples shown were gated on the CD8+ population, and then the percentage of CD8+ and HPV tetramer+ cells that were producing IFN-γ was assessed. The percentage of HPV-specific T cells producing IFN-γ after LCL stimulation is shown on the top right hand corner of each of the panels. These data are a representation of two separate experiments.
Mentions: To further confirm these observations, we established an ex vivo stimulation assay, in which PBMCs from three unrelated HLA B35–seropositive individuals were stimulated with autologous LCLs, 721.221 LCL, 721.221 LCL transfected with HLA B*3501 (referred to as 0.221.B*3501 LCL), or HLA B35− LCLs. After overnight incubation, these cells were assessed for binding to an HPV-HLA B*3501 tetramer and intracellular IFN-γ expression. Data presented in Fig. 4 clearly demonstrate that a large proportion of HPV-HLA B*3501 tetramer+ T cells showed strong intracellular IFN-γ expression after stimulation with autologous LCL or the 0.221.B*3501 LCL. On the other hand, no ex vivo IFN-γ response was observed within the HPV tetramer+ cells when the PBMCs were stimulated with the HLA B35− LCLs or left unstimulated. A similar pattern of IFN-γ response was also observed in other donors when stimulated with HLA B35+ LCLs (not depicted) These observations further confirm our conclusions drawn from Fig. 3, which indicated that EBV-infected B cells can endogenously process and present CTL epitopes directly to the virus-specific T cells.

Bottom Line: However, these different degradation rates do not correspond to the level of major histocompatibility complex class I-restricted presentation of EBNA1 epitopes.Functional assays revealed that processing of these EBNA1 epitopes is proteasome and transporter associated with antigen processing dependent.Based on these observations, we propose that defective ribosomal products, not the full-length antigen, are the primary source of endogenously processed CD8+ T cell epitopes from EBNA1.

View Article: PubMed Central - PubMed

Affiliation: EBV Unit, Tumour Immunology Laboratory, Division of Infectious Diseases and Immunology, Queensland Institute of Medical Research, 300 Herston Road, Brisbane (Qld) 4006, Australia.

ABSTRACT
Epstein-Barr virus (EBV)-encoded nuclear antigen (EBNA)1 is thought to escape cytotoxic T lymphocyte (CTL) recognition through either self-inhibition of synthesis or by blockade of proteasomal degradation by the glycine-alanine repeat (GAr) domain. Here we show that EBNA1 has a remarkably varied cell type-dependent stability. However, these different degradation rates do not correspond to the level of major histocompatibility complex class I-restricted presentation of EBNA1 epitopes. In spite of the highly stable expression of EBNA1 in B cells, CTL epitopes derived from this protein are efficiently processed and presented to CD8+ T cells. Furthermore, we show that EBV-infected B cells can readily activate EBNA1-specific memory T cell responses from healthy virus carriers. Functional assays revealed that processing of these EBNA1 epitopes is proteasome and transporter associated with antigen processing dependent. We also show that the endogenous presentation of these epitopes is dependent on the newly synthesized protein rather than the long-lived stable EBNA1. Based on these observations, we propose that defective ribosomal products, not the full-length antigen, are the primary source of endogenously processed CD8+ T cell epitopes from EBNA1.

Show MeSH
Related in: MedlinePlus