Function but not phenotype of melanoma peptide-specific CD8(+) T cells correlate with survival in a multiepitope peptide vaccine trial (ECOG 1696)

Abstract

ECOG 1696 was a Phase II multi-center trial testing vaccination with melanoma peptides, gp100, MART-1 and tyrosinase delivered alone, with GM-CSF, IFN-α2b or both cytokines to HLA-A2(+) patients with metastatic melanoma. Here, the frequency of circulating CD8(+) tetramer(+) (tet(+) ) T cells and maturation stages of responding T cells were serially monitored and compared with baseline values in a subset of patients (n = 37) from this trial. Multiparameter flow cytometry was used to measure the frequency of CD8(+) T cells specific for gp100, MART-1, tyrosinase and influenza (FLU) peptides. Expression of CD45RA/CCR7 on CD8(+) tet(+) T cells and CD25, CD27, CD28 on all circulating T cells was determined. Vaccine-induced changes in the CD8(+) tet(+) T cell frequency and phenotype were compared with results of IFN-γ ELISPOT assays and with clinical responses. The frequency of CD8(+) tet(+) T cells in the circulation was increased for the melanoma peptides (p < 0.03-0.0001) but not for FLU (p < 0.9). Only gp100- and MART-1-specific T cells differentiated to CD45RA(+) CCR7(-) effector/memory T cells. In contrast to the IFN-γ ELISPOT frequency, previously correlated with overall survival (Kirkwood et al., Clin Cancer Res 2009;15:1443-51), neither the frequency nor differentiation stage of CD8(+) tet(+) T cells correlated with clinical responses. Delivery of GM-CSF and/or IFN-α2b had no effects on the frequency or differentiation of CD8(+) tet(+) , CD8+ or CD4+ T cells. Phenotypic analyses of CD8(+) tet(+) T cells did not correlate with clinical responses to the vaccine, indicating that functional assessments of peptide-specific T cells are preferable for monitoring of anti-tumor vaccines.

Copyright © 2011 UICC.

Figures

Figure 1

Vaccine-induced changes in the frequency of CD8+tet+ T cells. (a) Box plots show the frequency of CD8+tet+ T cells in the circulation of patients at baseline (Day 0) and the two post-vaccination time points (Days 43 and 85). The bars are median values, the box shows the interquartile range (25–75%), and the whiskers indicate the maximum and minimum values. The maximal change from baseline defines the percent increase (or decrease) from baseline on Days 43 or 85, whichever gives the highest value. (b) Examples of dot plots for patient 16,069 are shown for two of the vaccine peptides (MART-1 and gp100) and the Flu control. The calculated CD8+tet+ frequencies are shown in each upper-right quadrant.

Figure 2

Vaccine-induced changes in the differentiation phenotypes. (a) The dot plots for the expression of CCR7 and CD45RA on CD8+tet+ T cells in patient 16,069 (see Fig. 2). The gate is set on CD8+tet+ T cells for FLU, MART-1 and gp100 tetramers. The tetramer frequency calculated for each quadrant is shown in the upper-right of each dot plot. For this analysis, 4 × 105 cells/ sample were acquired. Note that almost all gp100+ cells are in the EM and TD compartments. The gp100+ T cells represent 15% of CD8+ T cells in this patient on Day 85 (see Fig. 2b). (b) The dot plots for expression of CCR7 and CD45RA on CD8+tet+ versus CD8+tetneg (“global”) T cells in patient 16,053. Note that vaccine-induced changes in the differentiation phenotype are evident only for CD8+MART-1 and CD8+gp100+ tetramers but not for “global” CD8+ T cells. The patient’s CD8+tyr+ T cells were at 0.2%, and no changes were seen in the differentiation phenotype after vaccination (data not shown). (c) Differentiation profiles of CD8+gp100tet+ T cells, and CD8+tetneg T cells at baseline (n= 37) and on Day 43 after vaccination (n= 35) for all tested patients. The Day 83 profile was analogous to that on Day 43 and is not shown. Phenotype of tet+ tumour-specific T cells is significantly different than that of the tetneg CD8+ T cell population p < 0.0001. EM gp100+ T cells increased significantly after vaccination (p= 0.003). The bars indicate mean% ± SD.