Defective presentation of MHC class I-restricted cytotoxic T-cell epitopes in Burkitt's lymphoma cells

Abstract

Defects of antigen processing/presentation have been suggested to play a role in the escape of Burkitt's lymphoma (BL) from cytotoxic T lymphocyte (CTL)-mediated rejection. Impaired presentation of an immunodominant HLA A11-restricted epitope from the resident or recombinant vaccinia virus-expressed Epstein-Barr virus nuclear antigen (EBNA)4 was demonstrated in the EBV-positive E95B-BL28 and its EBV-negative parental BL28 cell lines. We have investigated whether this was due to (i) impaired production of the antigenic peptide, (ii) poor peptide translocation into the ER lumen or (iii) inefficient maturation and transport of the MHC-peptide complexes at the cell surface. The defect was not overcome by cytosolic expression of a pre-formed epitope, suggesting that presentation of EBNA4 is not limited by inefficient production of the antigenic peptide. BL28 expressed 5- to 10-fold lower levels of the transporter associated with antigen presentation (TAP) 1 and TAP2 proteins and behaved poorly in a streptolysin-O-mediated peptide translocation assay, whereas E95B-BL28 showed higher TAP expression and virtually normal transporter function. Up-regulation of HLA A11 and reconstitution of TAP activity by treatment with IFN-gamma did not restore presentation of the resident EBNA4 in E95SB-BL28 and did not enhance presentation of the vaccinia virus-expressed intact protein or preformed epitope. Efficient maturation of class I molecules to Endo H-resistant species was demonstrated in pulse-chase experiments. Taken together, our findings identify a previously uncharacterized defect of antigen presentation which appears to affect events occurring after proteasomal degradation but before TAP-dependent peptide transport and MHC class I assembly and maturation.

Epstein–Barr virus oncogenesis and the ubiquitin–proteasome system

“…Similar lymphoid infiltrates are found in all LMP-1-expressing malignancies of epithelial cell origin, which explains their histological definition as lymphoepitheliomas (Iezzoni et al, 1995). Several components of the antigen presentation pathway are also upregulated in LMP-1-expressing cells including the transporters associated with antigen processing (TAPs) Frisan et al, 1996) and the interferon-g-regulated subunits of the proteasome core and regulatory particles, which results in enhanced enzymatic activity and changed cleavage specificity (Frisan et al, 1998). A more direct mode of regulation is suggested by the finding that LMP-1 contains two peptides with strong homology to an immunosuppressive peptide found in the retrovirus-encoded transmembrane protein p15E (Dukers et al, 2000).…”

“…Characteristic for the tumor cells are also the low levels of MHC class I and selective loss of certain class I alleles, HLA A11 in particular (Andersson et al, 1991), which may contribute to the poor allostimulatory capacity of these cells in mixed lymphocyte cultures (Avila-Carino et al, 1987). In addition, BL cells are deficient in their ability to present endogenous antigens via the MHC class I pathway (Frisan et al, 1996), which correlates with downregulation of the interferon-ginducible subunits of the proteasome and the peptide transporters TAP1 and TAP2 Frisan et al, 1998).…”

“…Studies of in vitro EBV-transformed cell lines that recapitulate the BL cell phenotype through regulated expression of EBNA2/LMP-1 and c-Myc have shown that overexpression of c-Myc in the absence of LMP-1 is directly responsible for the altered immunogenicity of BL cells (Frisan et al, 1996(Frisan et al, , 1998Staege et al, 2002), which also correlates with alterations of ubiquitindependent proteolysis (Gavioli et al, 2001). BL cells were shown to be resistant to treatment with doses of proteasome inhibitors that are readily toxic for normal lymphoblasts.…”

Gene expression predicts overall survival in paraffin-embedded tissues of diffuse large B-cell lymphoma treated with R-CHOP

“…1,31,32 Down-regulation of immune response has been identified as a key feature of Burkitt lymphoma and poor-outcome DLBCL previously. 24,28,29,31,[33][34][35][36] Highly proliferative DLBCL has also been identified as a key feature of poor-outcome DLBCL. 1,4,37 This tentative 2-gene model therefore is biologically plausible based on previous literature.…”

Down‐regulation of locus‐specific human lymphocyte antigen class I expression in Epstein–Barr virus‐associated gastric cancer

“…5 Many reports have indicated that there are defects in the HLA class I-associated antigen processing and presentation pathway in EBV-associated BL and nasal natural killer (NK) cell/T-cell carcinoma. 6,7 Furthermore, there is evidence of the interference of certain viral antigens in the locus-specific and functional expression of HLA class I antigens in various malignancies. 8,9 Surprisingly, to our knowledge little is known regarding HLA class I antigen expression in EBVaGC, although it has been proposed that the down-regulation or complete loss of HLA class Ia antigen expression is a mechanism to escape host immunosurveillance and, thus, tumor progression.…”