Cancer regression and autoimmunity induced by cytotoxic T lymphocyte-associated antigen 4 blockade in patients with metastatic melanoma.

Surgery Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a critical immunoregulatory molecule (expressed on activated T cells and a subset of regulatory T cells) capable of down-regulating T cell activation. Blockade of CTLA-4 has been shown in animal models to improve the effectiveness of cancer immunotherapy. We thus treated 14 patients with metastatic melanoma by using serial i.v. administration of a fully human anti-CTLA-4 antibody (MDX-010) in conjunction with s.c. vaccination with two modified HLA-A*0201-restricted peptides from the gp100 melanoma-associated antigen, gp100:209-217(210M) and gp100:280-288(288V). This blockade of CTLA-4 induced grade III/IV autoimmune manifestations in six patients (43%), including dermatitis, enterocolitis, hepatitis, and hypophysitis, and mediated objective cancer regression in three patients (21%; two complete and one partial responses). This study establishes CTLA-4 as an important molecule regulating tolerance to "self" antigens in humans and suggests a role for CTLA-4 blockade in breaking tolerance to human cancer antigens for cancer immunotherapy.

PMID: 12826605 [PubMed - indexed for MEDLINE]

PMCID: PMC166236

CTLA-4. FasL induces alloantigen-specific hyporesponsiveness.

Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.

The APC:T cell interface can be effectively targeted with immunotherapeutic proteins. We previously described a unique trans signal converter protein, CTLA-4. Fas ligand (FasL), that has the inherent capacities to tether the T cell inhibitor FasL (CD95 ligand) to the surfaces of B7 (CD80 and CD86)-positive APC (via CTLA-4:B7 interaction), and in so doing, to simultaneously interfere with B7-to-CD28 T cell activation signals. Given the continuing need for agents capable of inducing allograft tolerance without generalized immunosuppression, we have explored in depth the functional activity of CTLA-4. FasL in human allogeneic MLR. CTLA-4. FasL inhibits 1 degrees MLR and induces specific hyporesponsiveness in 2 degrees MLR, with both effects only partially reversible with exogenous IL-2. Moreover, the presence of exogenous IL-2 during the 1 degrees MLR does not affect the induction of hyporesponsiveness upon restimulation. Furthermore, CTLA-4. FasL enables partial activation of allostimulated T cells, reduces the fraction of actively dividing cells, and increases the percentage of dead cells among dividing T cells. Taken together, these findings suggest that CTLA-4. FasL-mediated inhibition of secondary alloantigenic responses involves both anergy induction and clonal deletion. Thus, CTLA-4. FasL, a paradigmatic trans signal converter protein, manifests unique functional properties and emerges as a potentially useful immunotherapeutic for modulating alloresponsiveness.

PMID: 12794109 [PubMed - indexed for MEDLINE]

Inhibition of human T cell proliferation by CTLA-4 utilizes CD80 and requires CD25+ regulatory T cells.

MRC Centre for Immune Regulation, University of Birmingham Medical School, Vincent Drive, Birmingham B15 2TT, GB, UK.

CD28 and CTLA-4 are opposing regulators of T cell activation, triggered by the two ligands CD80 and CD86. How these ligands promote either T cell activation via CD28 or inhibition via CTLA-4 is not understood. Using CD80 and CD86 molecules expressed on transfected cells, we have identified a major difference between these ligands in that CD80 transfectants have the ability to inhibit activation of resting human peripheral blood T cells via interaction with CTLA-4, whereas CD86 transfectants do not. Rather, CTLA-4-CD86 interactions appear to contribute towards T cell proliferation. We also observed that CTLA-4 function is strongly influenced by TCR stimulation, effects being observed only at relatively low levels of TCR stimulation. The kinetics of CD80-CTLA-4 interactions revealed that CTLA-4 inhibition took place within the first 8 h of T cell stimulation, despite there being little measurable CTLA-4 expression on the majority T cells. However, significant amounts of CTLA-4 were observed in the CD25(+) CD4(+) subset of T cells which, when removed from the cultures, accounted for the CTLA-4 inhibition observed. Overall, these data provide evidence that CD80 and CD86 differ in their interactions with CTLA-4 and that CD80 appears to be the preferential inhibitory ligand for CTLA-4 working via a population of CD4(+) CD25(+) CTLA-4(+) regulatory T cells.

PMID: 12355442 [PubMed - indexed for MEDLINE]

Reduced CTLA-4 protein and messenger RNA expression in umbilical cord blood T lymphocytes.

Department of Pediatrics, University Hospitals Ireland Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH 44106, USA.

OBJECTIVE: A favorable incidence and severity of graft-vs-host disease is observed in patients transplanted with banked, unrelated, HLA-mismatched umbilical cord blood (UCB) grafts, while the incidence of malignant relapse remains low. CTLA-4 mediates negative T-cell signaling and may contribute to the development of allogeneic tolerance. In this study, we compared protein and mRNA expression of CTLA-4 in stimulated UCB and adult peripheral blood T cells. MATERIALS AND METHODS: T cells were isolated from UCB and adult peripheral blood and stimulated with anti-CD3 and anti-CD28 monoclonal antibodies. Cells were immunostained and analyzed by flow cytometry for both surface and intracellular expression of CTLA-4 in the presence and absence of cyclosporin A, and kinetics of CTLA-4 expression compared. CTLA-4 mRNA expression was measured using quantitative real-time polymerase chain reaction. NFAT1 protein levels were measured by Western blot analysis. RESULTS: These studies demonstrate reduced surface and intracellular expression of CTLA-4 in stimulated UCB T cells compared to adult controls. Furthermore, reduced CTLA-4 protein expression in UCB T cells was noted to be in part transcriptionally regulated, as CTLA-4 mRNA levels also were significantly lower. Reduced CLTA-4 expression by UCB T cells followed the kinetics of delayed and reduced expression of the transcription factor NFAT1 by UCB T lymphocytes during primary stimulation. Moreover, cyclosporin A, which is known to modulate NFAT activation, reduced CTLA-4 protein expression in adult and UCB T cells. CONCLUSION: Reduced expression of the key regulatory proteins CTLA-4 and NFAT-1 may contribute to favorable UCB T lymphocyte allogeneic responses.

PMID: 12135671 [PubMed - indexed for MEDLINE]

Role of the B7-CD28/CTLA-4 pathway in autoimmune disease.

Immunology Research Division, Department of Pathology, Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, Mass., USA.

PMID: 11826754 [PubMed - indexed for MEDLINE]