Targeting HIV-1 Gag into the defective ribosomal product pathway enhances MHC class I antigen presentation and CD8+ T cell activation

J Immunol. 2008 Jan 1;180(1):372-82. doi: 10.4049/jimmunol.180.1.372.


The main source for endogenous peptides presented by the MHC class I (MHC-I) pathway are de novo-synthesized proteins which are degraded via the ubiquitin proteasome pathway. Different MHC-I Ag pools can be distinguished: first, short-lived defective ribosomal products, which are degraded in concert with or shortly after their synthesis, and, second, functional proteins that enter the standard protein life cycle. To compare the contribution of these two Ag sources to the generation of MHC-I-presented peptides, we established murine cell lines which express as a model Ag the HIV-1 Gag polyprotein fused to ubiquitin (Ub) carrying the epitope SIINFEKL (SL). Gag was expressed either in its wild-type form (UbMGagSL) or as a variant UbRGagSL harboring an N-end rule degron signal. Although UbRGagSL displayed wild-type protein stability, its inherent defective ribosomal products rate observed after proteasome shutdown was increased concomitant with enhanced presentation of the SL epitope. In addition, UbRGagSL induces enhanced T cell stimulation of SL-specific B3Z hybridoma cells as measured in vitro and of adoptively transferred TCR-transgenic OT-1 T cells in vivo. Furthermore, an elevated frequency of SL-specific T cells was detected by IFN-gamma ELISPOT after immunization of naive C57BL/6 mice with UbRGagSL/EL4 cells. These results further underline the role of the defective ribosomal product pathway in adaptive immunity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antigen Presentation*
  • Antigens, Viral / genetics
  • Antigens, Viral / immunology
  • Antigens, Viral / metabolism*
  • CD8-Positive T-Lymphocytes / immunology
  • Cell Line
  • Cytotoxicity, Immunologic
  • Epitopes / chemistry
  • Epitopes / immunology
  • HIV-1*
  • Histocompatibility Antigens Class I / chemistry
  • Histocompatibility Antigens Class I / immunology
  • Histocompatibility Antigens Class I / metabolism*
  • Humans
  • Hybridomas
  • Interferon-gamma / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Peptides / chemistry
  • Peptides / immunology
  • Peptides / metabolism
  • Ribosomes / metabolism
  • T-Lymphocytes, Cytotoxic / immunology*
  • Ubiquitin / metabolism
  • gag Gene Products, Human Immunodeficiency Virus / genetics
  • gag Gene Products, Human Immunodeficiency Virus / immunology
  • gag Gene Products, Human Immunodeficiency Virus / metabolism*


  • Antigens, Viral
  • Epitopes
  • Histocompatibility Antigens Class I
  • Peptides
  • Ubiquitin
  • gag Gene Products, Human Immunodeficiency Virus
  • Interferon-gamma