Unit: Antiviral Cell Immunology

Director: François Lemonnier

The work of the laboratory aims, by producing genetically modified strains of mice (H-2 class I or class II knock-out mice, HLA class I or class II transgenic mice) at a) the analysis of the mechanisms involved in the education, the peripheral mobilization and the maintenance of cytolytic CD8+, helper CD4+ T lymphocytes and Natural Killer (NK) cells, b) the identification of viral or tumoral peptides presented to cytolytic and helper T lymphocytes, and c) the evaluation and optimization of their vaccine potential. More recently, the laboratory has get involved in an exploration of the interface between T lymphocytes and iron metabolism through the Hfe molecule.

HLA transgenic, H-2 KO mice (A. Pajot, Y.-C. Lone, P. Langlade-Demoyen, E. Boulanger, N. Gaidot, T. Laïka).

Additional HLA-transgenic, H-2 KO mouse strains have been created which express either HLA-A0201 and DR1, HLA-A0201 and DR3 or HLA-A0201 and DQ8 in a H-2 class I/class II null context. HLA-A0201 and DR1 immunized by Hepatitis B viral envelop mount immune responses (cytolytic, T CD4+ helper and antibody) superimposable to those of HLA-A0201+ and HLA-DR1+ humans and are specifically protected against a viral challenge with a recombinant vaccinia virus expressing the Hepatitis B viral envelop.

These mice have further been used for the identification of new HLA-DR-restricted, T CD4 epitopes derived from either the Hepatitis B viral envelop or the HIV 1 gag protein. The immunological potential of these epitopes that have been validated in humans has been compared to that of previously identified HLA-DR1-restricted epitopes using a recombinant mouse invariant chain vector in order to select those of the most promissing vaccinal potential. The HLA-A0201 and DQ8 mouse strain is used on a collaborative basis (INSERM Unit U 561) for a physiopathologic study of type 1 diabetis.

Two additional mouse strains expressing either HLA-A24.2 or HLA-A3.1 in a H-2 class I KO context have been derived and are used for the characterisation of T CD8 epitopes from HIV 1 proteins, with, as a final goal, the construction of polyepitopic motifs of vaccinal interest. Two other mouse strains (HLA-A0201 and HLA-B0702) H-2 class I KO have been used for the identification in the telomerase catalytic subunit of T CD8 epitopes that could be used for immunotherapy of a variety of human tumors.

Recognition by CD8+ cytolytic T lymphocytes of histocompatibililty molecules deprived of antigen presention function (P. Rohrlich).

Cytolytic CD8+ T lymphocytes recognize short antigenic peptides bound to histocompatibility molecules in their peptide binding pocket. Immunizing mice deficient in Hfe molecules (a molecule which regulates iron metabolism, has an overall structure similar to that of " classical " histocompatibility molecules but has no ligand in its peptide binding pocket) cytolytic CD8+ T lymphocytes were stimulated that recognize directly Hfe. Thus, the presence of a ligand in the peptide binding pocket of histocompatibility molecules is not an absolute requirement for their recognition by the T cell receptor (TcR) for antigen. Direct recognition of Hfe results from the preferential mobilization of a subset of CD8+ T lymphocytes with predominant usage of a defined variable segment of the TcR α chain. This subset of CD8+ T lymphocytes might therefore participate in the regulation of iron metabolism. These results, together with various published observations, support the possibility that the TCR α chain might be mainly responsible for the recognition of MHC α helices whereas the α and α chains hypervariable CDR3 regions intereact principally with the presented peptides. Applying such a functional dichotomy to alloreactive T lymphocyte populations leads to hypothesize that selective (in terms of α chain variable segments usage) alloreactive subsets of T lymphocytes could be mobilized with regard of the HLA mismatch between donor and graft recipient.

Genes controlling NK cell differentiation (C. Roth and S. Riou).

C. Roth and S. Riou have documented the implication of 3 tyrosine kinase receptors (Tyro 3, Mer and Axl) implicated in the final maturation step of NK cells in bone marrow. Mice deficient for these 3 receptors have NK T cells with reduced functional capacities (low cytolytic activity, reduced production of γ interferon) and expressing on cell surface lower levels of Ly-49 molecules. It thus appears that the 2 known ligands, Gas 6 and proteine S) of these 3 receptors which are produced by bone marrow stromal cells control NK cell final differenciation as they also do for cells of the central nervous system and cells of the germinal line.

Keywords: HLA Transgenic, H-2 KO mice, HIV 1, Hfe, NK

Activity Reports 2005 - Institut Pasteur

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