The soluble IL2-receptor (sIL2R) serum level, which indicates T-cell activation, analogously increased after each trAb application. Comparing the sIL2R level on day 1 after trAb application, the maximum sIL2R level was found after the third trAb application, indicating an ongoing and increasing cellular immune activation during trAb therapy. Figure 1 Serum levels (mean, +/-
SEM) of TNF-α (A), soluble IL-2R (B), and IL-6 (C) immediately before the first, second and third trAb application, and corresponding I-BET-762 cell line serum levels on day one and two dafter trAb therapy. Serum levels were measured by ELISA (Biosource, Fleurs, Belgium). * p < 0.05. HAMA was measured after trAb therapy in 7 of 9 patients. In all these patients, HAMA was significantly increased (above the threshold of 40 ng/ml), representing an immunological reaction (Table 4). Table 4 Restimulation and response Patient Increase of IFN-γ secreting T-lymphocytes HAMA
(ng/ml) Chemotherapy after trAb therapy Survival after trAb therapy (months) A + 801 – 1 B + 230 + 21 C – 30512 + 31 D – n.d. – 4 E + 7870 + 7 F – 50730 + 12 G + 2540 + 15 H AMN-107 concentration – 400 + 8 I + n.d. – 7 Increase of IFN-γ secreting T-lymphocytes compared to baseline values before therapy. HAMA = human anti-mouse antibody reaction (values measured 4 weeks after trAb therapy). Immunological anti-tumor reactivity All patients were restimulated 4 weeks after i.p.-application of trAb. Patients revealed a base value of 0.4% (mean) CD4+/CD8+ IFN-γ secreting T-lymphocytes in
PBMC before trAb-treatment. Five of nine patients showed an increase of IFN-γ secreting T-lymphocytes, reflecting 4-Aminobutyrate aminotransferase autologous anti-tumor reactivity (Figure 2). In these 5 patients, the number of tumor reactive T-lymphocytes increased from baseline value of 0.4% to 2.9% (mean) after trAb therapy and restimulation. All control experiments with unstimulated PBMC or PBMC incubated with allogeneic tumor cells showed no increase compared to the corresponding baseline values. In patient B, the IFN-γ secretion assay was performed twice after intradermal restimulation (Figure 3). Here, IFN-γ secreting T-lymphocytes increased from 0.4% before therapy to 2.8% after restimulation, followed by a value of 2.8% on day 110 after stimulation, indicating long-term immunity. This patient also had a substantial decrease of tumor markers (CA 125 decreased from 57.8 U/ml to 29.7 U/ml). Figure 2 Individual percentage values presenting the relative proportion of IFN-γ secreting T-lymphocytes in 10 × 10 6 PBMC after stimulation with 5 × 10 5 autologous tumor cells before and 3–4 weeks after trAb therapy using the Miltenyi IFN-γ secretion assay. Figure 3 Analysis of tumor reactive IFN-γ secreting CD4+/CD8+ T lymphocytes before trAb therapy and on day 39 and 110 after boost stimulation in patient B using the Miltenyi IFN-γ secretion assay.