Persistent TCRB repertoire in blood found at vaccination site and tumor infiltrating lymphocytes in a cutaneous melanoma patient immunized with the CSF-470 vaccine plus BCG and rhGM-CSF

ARIS, MARIANA; BRAVO, ALICIA INÉS; GARCIA ALVAREZ, HELI MAGALÍ; CARRI, IBEL; PODAZA, ENRIQUE; BLANCO, PAULA ALEJANDRA; ROTONDARO, CECILIA; BENTIVEGNA, SOFIA; NIELSEN, MORTEN; BARRIO, MARÍA MARCELA; MORDOH, JOSÉ

París

Conferencia; FIFTH CRI-CIMT-EATI-AACR INTERNATIONAL CANCER IMMUNOTHERAPY CONFERENCE: TRANSLATING SCIENCE INTO SURVIVAL; 2019

Cancer Research Institute (CRI) and the European Network for Cancer Immunotherapy (ENCI)

The CASVAC-0401 study analyzed the combination of the CSF- 470 cell-based vaccine plus BCG and rhGM-CSF for immunotherapy adjuvancy in stage II-III cutaneous melanoma patients after surgery, in comParison to medium dose IFN-a2b. Patient-045 developed a mature vaccination site (VAC-SITE) and a regional cutaneous metastasis (C-MTS) which were excised during the protocol. CDR3-TCRβ repertoire sequencing in PBMC and tissue samples, along with skin-DTH score and IFN-G ELISPOT assay in PBMC obtained before, during and at the end of vaccination were performed to analyze the T-cell immune response dynamics throughout the immunization protocol. Histopathological analysis of the VAC-SITE revealed a highly-inflamed granulomatous structure, with a necrotic center encircled by CD11c+ nested-clus- ters, surrounded by CD8+ lymphocytes, mostly PD1-negative and scarce FOXP3+ lymphocytes. Large numbers of Langhans multi-nucleated-giant-cells and macrophages were as well detected. The C-MTS contained a large tumor-regression area fulfilled with brisk lymphocyte infiltration, mainly composed of CD8+PD1+ T-cells, CD20+ B-cells, and scarce FOXP3+ cells. Despite the emergence of a loco-regional lymph-node and a small cutaneous metasta- sis, patient-045 remains disease-free 36 months after initiating CSF-470 vaccination. The immune response induced through- out treatment was evidenced by increasing DTH score and IFN-γ ELISPOT assay against the vaccine lysate. TCRβ repertoire analysis revealed for the first time the presence of common clonotypes between the VAC-SITE and the C-MTS ; most of them persisted in blood by the end of the immunization protocol. We found that expansion of such persistent clonotypes might derive from two different although complementary mechanisms : proliferation of specific clones as well as expansion of redundant clones, which increased the number of nucleotide rearrangements per clono- type, suggesting a functional antigenic selection. In this patient, immunization with the CSF-470 vaccine plus BCG and rhGM-CSF induced a T-cell repertoire at the VAC-SITE that was able to infiltrate an emerging C-MTS, contributing to the generation of a local immune response, resulting in the expansion of a T-cell repertoire which persisted in blood by the end of the 2-year treatment.