Search

Very little is known about the conformational properties of the MHC molecules that are able to signal positive selection of a given TCR. To try to understand these parameters and to determine whether these requirements are shared with interactions during negative selection and antigen recognition, we have studied selection and antigen recognition of a transgenic TCR (specific for lymphocytic choriomeningitls virus glycoprotein and H-2Db) in the context of two Db mutants, H-2bm13 and H-2bm14. The data showed that the transgenic TCR was not positively selected by the H-2bm14 haplotype but, interestingly, enhanced positive selection was seen in H-2bm13 mice. The transgenic TCR could not be negatively selected In H-2bm13animals persistently infected with the virus (neonatal virus carrier mice), nor could the transgenic TCR be activated by H-2bm13 infected cells in vivo or in vitro. These experiments show that although a TCR may be selected by a mutant MHC molecule, the corresponding viral antigen cannot be recognized in the context of the mutant MHC molecule, as Judged by both negative selection and T cell reactivity in vivo and in vitro. The ‘enhanced' positive selection occurring in the context of Dbm13 suggests that a different conformation of the MHC molecule is able to select the same TCR and also that various TCR-ligand avidities may permit positive selection

Udgivelsesdato: 2009-Jul-27, Antigen-specific immunotherapy is an attractive strategy for cancer control. In the context of antiviral vaccines, adenoviral vectors have emerged as a favorable means for immunization. Therefore, we chose a strategy combining use of these vectors with another successful approach, namely linkage of the vaccine antigen to invariant chain (Ii). To evaluate this strategy we used a mouse model, in which an immunodominant epitope (GP33) of the LCMV glycoprotein (GP) represents the tumor-associated neoantigen. Prophylactic vaccination of C57BL/6 mice with a replication-deficient human adenovirus 5 vector encoding GP linked to Ii (Ad-Ii-GP) resulted in complete protection against GP33-expressing B16.F10 tumors. Therapeutic vaccination with Ad-Ii-GP delayed tumor growth by more than 2 wk compared with sham vaccination. Notably, therapeutic vaccination with the linked vaccine was significantly better than vaccination with adenovirus expressing GP alone (Ad-GP), or GP and Ii unlinked (Ad-GP+Ii). Ad-Ii-GP- induced tumor control depended on an improved generation of the tumor-associated neoantigen-specific CD8(+) T-cell response and was independent of CD4(+) T cells. IFN-gamma was shown to be a key player during the tumor degradation. Finally, Ad-Ii-GP but not Ad-GP vaccination can break the immunological non-reactivity in GP transgenic mice indicating that our vaccine strategy will prove efficient also against endogenous tumor antigens.

Udgivelsesdato: 2009-Jul-27, Antigen-specific immunotherapy is an attractive strategy for cancer control. In the context of antiviral vaccines, adenoviral vectors have emerged as a favorable means for immunization. Therefore, we chose a strategy combining use of these vectors with another successful approach, namely linkage of the vaccine antigen to invariant chain (Ii). To evaluate this strategy we used a mouse model, in which an immunodominant epitope (GP33) of the LCMV glycoprotein (GP) represents the tumor-associated neoantigen. Prophylactic vaccination of C57BL/6 mice with a replication-deficient human adenovirus 5 vector encoding GP linked to Ii (Ad-Ii-GP) resulted in complete protection against GP33-expressing B16.F10 tumors. Therapeutic vaccination with Ad-Ii-GP delayed tumor growth by more than 2 wk compared with sham vaccination. Notably, therapeutic vaccination with the linked vaccine was significantly better than vaccination with adenovirus expressing GP alone (Ad-GP), or GP and Ii unlinked (Ad-GP+Ii). Ad-Ii-GP- induced tumor control depended on an improved generation of the tumor-associated neoantigen-specific CD8(+) T-cell response and was independent of CD4(+) T cells. IFN-gamma was shown to be a key player during the tumor degradation. Finally, Ad-Ii-GP but not Ad-GP vaccination can break the immunological non-reactivity in GP transgenic mice indicating that our vaccine strategy will prove efficient also against endogenous tumor antigens.

CCR7(+ )central memory (T(CM)) CD4(+) T cells play a central role in long-term immunological memory. Recent reports indicate that a proportion of CD4(+) T(CM) is able to produce effector cytokines. The phenotype and the role of this subset remain unknown. We characterized cytokine-producing human CD4(+) T(CM) specific for cleared protein and persistent viral Ag. Our results demonstrate that the type of Ag stimulation is a major determinant of CD4(+) T(CM) differentiation. CMV-specific T(CM) were significantly more differentiated than protein Ag-specific T(CM) and included higher proportions of IFN-gamma-producing cells. The expression of killer cell lectin-like receptor G1 (KLRG1) by protein Ag- and CMV-specific T(CM) was associated with increased production of effector cytokines. KLRG1(+) T(CM) expressed high levels of CD127, suggesting that they can survive long term under the influence of IL-7. The induction of KLRG1(+) T(CM) may therefore represent an important target of vaccination against pathogens controlled by cellular immune responses., Journal Article, Research Support, Non-U.S. Gov't, FLWIN, info:eu-repo/semantics/published

CCR7(+ )central memory (T(CM)) CD4(+) T cells play a central role in long-term immunological memory. Recent reports indicate that a proportion of CD4(+) T(CM) is able to produce effector cytokines. The phenotype and the role of this subset remain unknown. We characterized cytokine-producing human CD4(+) T(CM) specific for cleared protein and persistent viral Ag. Our results demonstrate that the type of Ag stimulation is a major determinant of CD4(+) T(CM) differentiation. CMV-specific T(CM) were significantly more differentiated than protein Ag-specific T(CM) and included higher proportions of IFN-gamma-producing cells. The expression of killer cell lectin-like receptor G1 (KLRG1) by protein Ag- and CMV-specific T(CM) was associated with increased production of effector cytokines. KLRG1(+) T(CM) expressed high levels of CD127, suggesting that they can survive long term under the influence of IL-7. The induction of KLRG1(+) T(CM) may therefore represent an important target of vaccination against pathogens controlled by cellular immune responses., Journal Article, Research Support, Non-U.S. Gov't, FLWIN, info:eu-repo/semantics/published

Very little is known about the conformational properties of the MHC molecules that are able to signal positive selection of a given TCR. To try to understand these parameters and to determine whether these requirements are shared with interactions during negative selection and antigen recognition, we have studied selection and antigen recognition of a transgenic TCR (specific for lymphocytic choriomeningitls virus glycoprotein and H-2Db) in the context of two Db mutants, H-2bm13 and H-2bm14. The data showed that the transgenic TCR was not positively selected by the H-2bm14 haplotype but, interestingly, enhanced positive selection was seen in H-2bm13 mice. The transgenic TCR could not be negatively selected In H-2bm13animals persistently infected with the virus (neonatal virus carrier mice), nor could the transgenic TCR be activated by H-2bm13 infected cells in vivo or in vitro. These experiments show that although a TCR may be selected by a mutant MHC molecule, the corresponding viral antigen cannot be recognized in the context of the mutant MHC molecule, as Judged by both negative selection and T cell reactivity in vivo and in vitro. The ‘enhanced' positive selection occurring in the context of Dbm13 suggests that a different conformation of the MHC molecule is able to select the same TCR and also that various TCR-ligand avidities may permit positive selection

Two populations of CD4 single positive (SP) thymocytes were found In transgenic mice bearing class l-restricted Mls-1a reactive (Vβ8.1) TCR genes in the absence of the restriction element. CD3high CD4 sp cells were deleted In the presence of Mls-15 and were cortisone resistant, whereas CD3low CD4 SP cells were not deleted In the presence of Mls-1* and were cortisone sensitive. Intravenous transfer of CD3low CD4 SP cells into nude mice resulted in significant peripheral expansion of these cells with apparent upregulation of CD3. These data Indicate that CD3low CD4 SP thymocytes represent an Intermediate stage In the transition from CDSlow double positive (DP) to CD3high SP thymocytes and raise the possibility that these cells may have undergone positive but not negative selection events (at least to Mls-1a). Furthermore the fact that CD3high DP thymocytes were also deleted by Mls-1a in these mice suggests strongly that sensitivity to Mls-1a deletion is dependent upon stage of thymic maturation (as revealed by TCR density) rather than CD4/CD8 phenotype

Clonal deletion of thymocytes bearing TCR for self antigens is one major mechanism of T cell tolerance induction. Peptide antigen-induced deletion of thymocytes from αβ TCR transgenic mice has been studied using single cell suspension cultures. The results show that antigen-presenting immature CD4+CD8+ thymocytes can tolerize antigen-reactive immature thymocytes in vitro by programmed cell death (apoptosis) 6-8 h after antigen exposure. Antigen-induced apoptosis of immature thymocytes was inhibited by antibodies specific for the αβ TCR, CD3, CD8, and LFA-1 molecules. This implies that clonal elimination of self-reactive CD4+CD8+ thymocytes does not depend on specialized deleting cell types in the thymus and occurs whenever the TCR of immature thymocytes bind antigen fragments presented by MHC molecules

Very little is known about the conformational properties of the MHC molecules that are able to signal positive selection of a given TCR. To try to understand these parameters and to determine whether these requirements are shared with interactions during negative selection and antigen recognition, we have studied selection and antigen recognition of a transgenic TCR (specific for lymphocytic choriomeningitls virus glycoprotein and H-2Db) in the context of two Db mutants, H-2bm13 and H-2bm14. The data showed that the transgenic TCR was not positively selected by the H-2bm14 haplotype but, interestingly, enhanced positive selection was seen in H-2bm13 mice. The transgenic TCR could not be negatively selected In H-2bm13animals persistently infected with the virus (neonatal virus carrier mice), nor could the transgenic TCR be activated by H-2bm13 infected cells in vivo or in vitro. These experiments show that although a TCR may be selected by a mutant MHC molecule, the corresponding viral antigen cannot be recognized in the context of the mutant MHC molecule, as Judged by both negative selection and T cell reactivity in vivo and in vitro. The ‘enhanced' positive selection occurring in the context of Dbm13 suggests that a different conformation of the MHC molecule is able to select the same TCR and also that various TCR-ligand avidities may permit positive selection