A reversible functional defect of CD8+ T lymphocytes involving loss of tetramer labeling

We eventually isolated two different clonotypic CD8 T cell subsets recognizing an HIV Pol-derived epitope peptide (IPLTEEAEL) in association with HLA-B35 from a chronic HIV-infected patient. By kinetic analysis experiments, the subsets showed a >3-fold difference in half-lives for the HLA tetramer in complex with the Pol peptide. In functional assays in vitro and ex vivo, both subsets showed substantial functional avidity toward peptide-loaded cells. However, the high affinity subset did not show cytolytic activity, cytokine production, or proliferation activity toward HIV-infected cells, whereas the moderate affinity one showed potent activities. Furthermore, using ectopic expression of each of the TCR genes into primary human CD8 T cells, the CD8 T cells transduced with the high affinity TCR showed greater binding activity toward the tetramer and impaired cytotoxic activity toward HIV-infected cells, corroborating the results obtained with parental CD8 T cells. Taken together, these data indicate that impaired responsiveness of T cells toward HIV-infected cells can occur at the level of TCR-ligand interactions, providing us further insight into the immune evasion mechanisms by HIV.

Section: Discussionmentioning

confidence: 99%

Functionally Impaired HIV-Specific CD8 T Cells Show High Affinity TCR-Ligand Interactions

Ueno

Tomiyama

Fujiwara

et al. 2004

“…Although it was possible that assaying for other cytokines, such as TNF-␣ could have identified a higher percentage of Ag-specific cells, this would probably only have represented a minor contribution, as the percentage of Ag-specific cells identified by tetramer staining and IFN-␥ staining correlated well. One possible explanation for why roughly only half of OT1 control-vector cells stained positive may relate to their activation state, because it has been reported that even though Ag-specific T cells may retain both TCR and CD8 expression, they may not always stain tetramer positive or exhibit Ag-specific functional qualities (74,75). If the activation state is a relevant factor, this may also explain why roughly 25% of BL6 ovASBN-vector cells stained positive for high levels of exogenous dual ␣␤ TCR expression while only 10 -15% of BL6 ovASBN-vector cells were positive by IFN-␥ staining or tetramer analysis.…”

Section: Discussionmentioning

confidence: 99%

Transfer of TCR Genes into Mature T Cells Is Accompanied by the Maintenance of Parental T Cell Avidity

Rubinstein

Kadima

Salem

et al. 2003

The adoptive transfer of tumor-specific T cells expanded in vitro can be of significant therapeutic value in select cancer patients. This strategy is limited though, as it is often difficult, if not impossible, to obtain T cells of clinical value. The transfer of TCR genes to mature T cells to generate tumor-reactive T cells provides a potential mechanism to overcome these limitations. To evaluate the feasibility of such an approach and the quality of the resulting T cells, we generated replication-deficient retroviral vectors using the well-characterized OT-1 TCR genes. After transducing murine T cells, we were able to expand large numbers of Ag-specific T cells that were functionally active against tumor cells expressing the relevant Ag. Furthermore, we found that T cells expressing retrovirally encoded TCR had avidity that was similar to that of the parental clone. This maintenance of avidity was despite variable expression of the retrovirally encoded TCR and the presence of potentially competing endogenous TCRs. These results suggest that the inherent qualities of the TCR, as dictated by the coding sequence, are the most critical parameters in the generation of high-avidity T cells.

“…Discrepancies between cytokine release or cytolytic activity and tetramer binding have also been found in melanoma patients (38) and have been reported for cultured T cells (39). Furthermore, triggering T cell clones under certain in vitro stimulation conditions has been demonstrated to lead to a loss of tetramer labeling (40). Moreover, tetramer binding has been shown to be an active cellular process requiring cytoskeletal rearrangements (41), and efficient binding also depends on the integrity of lipid rafts on the surface of T cells (42).…”

Section: Discussionmentioning

confidence: 99%

Lack of Effector Cell Function and Altered Tetramer Binding of Tumor-Infiltrating Lymphocytes

Blohm

Roth

Brommer

et al. 2002

Tumor-specific CD8 T cell responses to MCA102 fibrosarcoma cells expressing the cytotoxic T cell epitope gp33 from lymphocytic choriomeningitis virus were studied. MCA102gp33 tumors grew progressively in C57BL/6 mice, despite induction of peripheral gp33-tetramer+ T cells that were capable of mediating antiviral protection, specific cell rejection, and concomitant tumor immunity. MCA102gp33 tumors were infiltrated with a high number (∼20%) of CD11b+CD11c− macrophage-phenotype cells that were able to cross-present the gp33 epitope to T cells. Tumor-infiltrating CD8 T cells exhibited a highly activated phenotype but lacked effector cell function. Strikingly, a significant portion of tumor-infiltrating lymphocytes expressed TCRs specific for gp33 but bound MHC tetramers only after cell purification and a 24-h resting period in vitro. The phenomenon of “tetramer-negative T cells” was not restricted to tumor-infiltrating lymphocytes from MCA102gp33 tumors, but was also observed when Ag-specific T cells derived from an environment with high Ag load were analyzed ex vivo. Thus, using a novel tumor model, allowing us to trace tumor-specific T cells at the single cell level in vivo, we demonstrate that the tumor microenvironment is able to alter the functional activity of T cells infiltrating the tumor mass.