HIV Envelope Protein Inhibits MHC Class I Presentation of a Cytomegalovirus Protective Epitope

Abstract

CTL recognize peptides that derive from viral protein Ags by proteolytic processing and are presented by MHC class I molecules. In this study we tested whether coexpression of viral Ags in the same cell leads to competition between them. To this end, two Ld-restricted epitopes derived from HIV-1 envelope gp160 (ENV) and from CMV pp89 phosphoprotein were coexpressed. HIV ENV strain IIIB, but not MN variant, impaired recognition by specific CTL of CMV pp89 epitope 9pp89. Susceptibility to inhibition after ENV coexpression was inversely related to the amount of antigenic 9pp89 peptide processed from different antigenic constructs. In line with it, competition decreased the yield of naturally processed antigenic 9pp89 peptide bound to MHC class I molecules in coinfected cells. Also, point mutants of the presenting MHC class I molecule differed in their competition pattern. Collectively, the data imply that competition operates at the step of MHC-peptide complex assembly or stabilization. We conclude that, although not the rule, in certain combinations there is interference between different Ags expressed in the same cell and presented by the same MHC class I allele. These studies have implications for vaccine development and for understanding immunodominance.

An Endogenous HIV Envelope-derived Peptide without the Terminal NH3+ Group Anchor Is Physiologically Presented by Major Histocompatibility Complex Class I Molecules

“…of 3, and 14 h later they were washed and incubated for 2 h at 37°C in phosphate-buffered saline containing 0,1% bovine serum albumin and 500 M of the different peptides, as described (32). After washing (time point 0), the cells were further incubated at 37°C.…”

“…After washing (time point 0), the cells were further incubated at 37°C. Aliquots removed at different time points were stained with mAb 34-5-8S, which recognizes D d bound to peptides (34), followed by flow cytometry (32). Cells incubated without peptide had peak fluorescence intensities close to background staining with second Ab alone.…”

“…of 3.5 PFU per cell, and 16 h later naturally processed peptides were extracted from whole cells with trifluoroacetic acid (29,32) and purified by RP-HPLC (33). Control extractions were performed identically, except that pellets of 10 9 P13.1 cells received 10 nmol of R10I and Q11I peptides immediately after addition of trifluoroacetic acid.…”

Role of Metalloproteases in Vaccinia Virus Epitope Processing for Transporter Associated with Antigen Processing (TAP)-independent Human Leukocyte Antigen (HLA)-B7 Class I Antigen Presentation

“…Spleen cells were obtained from HLA-B*0702 transgenic mice at 7 days (acute response) or up to 30 days (memory response) post-intraperitoneal (intraperitoneal) infection with 1 ϫ 10 7 pfu of VACV-WR as described previously (18). After harvest, cells were stimulated for 2 h with RMA HLA-B*0702 cells infected with VACV-WR and incubated for 3 h in the presence of 5 g/ml BFA.…”

“…This allogeneic system prevents cross-presentation of TAP-dependent HLA-B*0702-restricted peptides in the cell culture. The CD8 ϩ T cell line was re-stimulated with VACVinfected RMA-S HLA-B*0702 cells and was cultured in ␣-minimal essential medium supplemented with 10% FBS and 1% ␤-mercaptoethanol and was used after five re-stimulations as effector cells in standard 4-h cytolytic assays (18) or ICS staining similarly to ex vivo ICS.…”