Proliferation and Activation Patterns of Naïve, Memory and Regulatory T Cells in Patients with Multiple Myeloma During Thalidomide, Interferon-α and Bortezomib Maintenance Therapy.
Authors: Hundemer Michael , Herth Isabelle , Meissner Tobias , Hose Dirk , Ho Anthony D , Neben Kai , Goldschmidt Hartmut , Witzens-Harig Mathias 
Published: October 2019

Abstract
Abstract 3880
Poster Board III-816
Hundemer and Herth (Contributed equally)

Introduction
In patients with Multiple myeloma, maintenance therapy after high-dose chemotherapy and autologous stem cell transplantation is performed with the aim to prolong remission duration and survival. Beside IFN-α, thalidomide and bortezomib are increasingly applied in maintenance protocols. In this prospective study we have analysed the implication of the various types of maintenance therapy on the patients T cell pattern and activation status.

Patients and Methods
T cells from 63 patients in clinical remission were analyzed. The median duration of remission was 38,6 months. Eighteen patients were treated with IFN-α, 22 with thalidomide, 7 with bortezomib and 16 patients received no maintenance therapy (control group). Peripheral blood mononuclear cells were isolated and stimulated with CD3/CD28 beads. Activated and nonactivated T cells were analyzed by flow cytometry (CD45RA, CD45RO, CCR7, CD28, CD200R, CD95, CD279, CD69, CD134 and TCRγ/δ) and ELISA (IFN-γ, perforine and granzym B). Furthermore the rate of IFN-γ-producing and regulatory T cells were analyzed by intracytoplasmatic staining and flow cytometry.

Results
All groups including the control group showed an up-regulation of CD69 and CD134 on CD4+ and CD8+ T cells after activation (p<0,001), on CD8+ T cells in the bortezomib-group only CD69 was upregulated (p=0,008). Patients treated with IFN-α showed a high rate of naïve T cells (CD45RA- and CCR7-positive), while in the thalidomide-group a high rate of effector memory T-cells (CD45RA- and CCR7-negative) were observed (CD45RA on CD8+ and CD4+ T cells: p<0,001, CCR7 on CD8+ T cells: p=0,03, CCR7 on CD4+ T cells: p=0,003). Regarding the surface marker CD28 on CD8+ T cells the IFN-α-group demonstrated a significant higher expression than the control-group (p=0,04) and the bortezomib-group a significant lower expression than the IFN-α- and the thalidomide-group (p=0,006 and p=0,02). Furthermore the rate of IFN-γ-producing CD4+ T cells was significant higher in the thalidomide-group than in the IFN-α-group after activation (p=0,02). On the basis of the cytoplasmatic staining of Foxp3 there was a trend to a higher amount of regulatory T cells in the thalidomide-group compared to the IFN-α-group (p=0,07). Analysis of IFN-y secretion by ELISA, an increases IFN-γ secretion could be demonstrated in all groups after activation (control group: p=0,002, IFN-α-group: p<0,001, thalidomide-group: p<0,001, bortezomib group: p=0,01), furthermore in all groups despite the bortezomib-group an increase of the granzyme B-production can be observed (control group: p=0,003, IFN-α-group: p=0,03, thalidomide-group: p<0,001). Regarding the activated state of the T cells the production of IFN-γ, perforine and granzyme B was significant higher in the thalidomide-group than in the IFN-α-group (IFN-γ: p=0,05, perforine: p=0,02, granzyme B: p=0,04). Furthermore the nonactivated and the activated T cells of the patients treated with thalidomide showed a significant higher production of granzyme B than the T cells of the control group (p=0,0003 and p=0,006).

Conclusion
During maintenance therapy, thalidomide promotes maturation and proliferation of effector memory T cells and regulatory T cells, while IFN-α treatment increases the number of naïve T cells and subsequently, the T cell activation in the thalidomide group was significantly higher than in the IFN-α group. These results have profound impact on the development of novel immunomodulating therapy strategies in the treatment of multiple myeloma.

Disclosures:
No relevant conflicts of interest to declare.