Langerhans dendritic cell vaccine bearing mRNA-encoded tumor antigens induces antimyeloma immunity after autotransplant

Abstract

Posttransplant vaccination targeting residual disease is an immunotherapeutic strategy to improve antigen-specific immune responses and prolong disease-free survival after autologous stem cell transplantation (ASCT) for multiple myeloma (MM). We conducted a phase 1 vaccine trial to determine the safety, toxicity, and immunogenicity of autologous Langerhans-type dendritic cells (LCs) electroporated with CT7, MAGE-A3, and Wilms tumor 1 (WT1) messenger RNA (mRNA), after ASCT for MM. Ten patients received a priming immunization plus 2 boosters at 12, 30, and 90 days, respectively, after ASCT. Vaccines contained 9 × 106 mRNA-electroporated LCs. Ten additional patients did not receive LC vaccines but otherwise underwent identical ASCT and supportive care. At 3 months after ASCT, all patients started lenalidomide maintenance therapy. Vaccinated patients developed mild local delayed-type hypersensitivity reactions after booster vaccines, but no toxicities exceeded grade 1. At 1 and 3 months after vaccines, antigen-specific CD4 and CD8 T cells increased secretion of proinflammatory cytokines (interferon-γ, interleukin-2, and tumor necrosis factor-α) above prevaccine levels, and also upregulated the cytotoxicity marker CD107a. CD4 and CD8 T-cell repertoire analysis showed a trend for increased clonal expansion in the vaccine cohort, which was more pronounced in the CD4 compartment. Although not powered to assess clinical efficacy, treatment responses favored the vaccine arm. Triple antigen-bearing mRNA-electroporated autologous LC vaccination initiated at engraftment after ASCT, in conjunction with standard lenalidomide maintenance therapy for MM, is safe and induces antigen-specific immune reactivity. This trial was registered at www.clinicaltrials.gov as #NCT01995708.

© 2022 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.

Figures

Graphical abstract

Figure 1.

Clinical responses after ASCT and mRNA-electroporated LC vaccines. (A) Depth of response pre-ASCT and at days +90 (d90) and +365 (d365) after ASCT. Relapse is also indicated. PFS and OS for patients in the control arm (B) and the vaccine arm (C). D, deceased; R, relapse.

Figure 2.

Bone marrow immunophenotyping after ASCT and mRNA-electroporated LC vaccines. BMMCs were analyzed by flow cytometry to profile the lymphocyte composition postvaccination in comparison with baseline (prevaccine) and an unvaccinated control cohort. (A) t-Distributed stochastic neighbor embedding plots at 3 months after vaccination showing CD4 and CD8 T cells (far left plot), CD4 and CD8 effector memory cells (TEM; CCR7negCD45RAneg) (middle left plot), CD4 and CD8 naive cells (TN; CCR7+CD45ROneg) (middle right plot), and PD-1–expressing CD4 and CD8 cells (far right plot). CD4 (B) and CD8 (C) effector memory, naive, and PD-1–expressing cells at 1 and 3 months after vaccines. Pooled data (mean ± standard deviation) are shown for patients in the control (red circles) and vaccine (blue squares) arms. ns, not significant; Pre, prevaccine.

Figure 3.

LC vaccines after ASCT stimulate antigen-specific CD4 and CD8 T-cell cytokine secretion and activation epitope expression. Postvaccination recall responses to CT7, MAGE-A3, and WT1 mRNA-electroporated LCs were measured as the fold change increase above prevaccine baseline using PBMCs at 1 and 3 months after vaccines (A-B) and BMMCs at 3 months after vaccines (C-D). Fold change in CD4 (A,C) and CD8 (B,D) T-cell proinflammatory cytokine (IFN-γ, IL-2, and TNF-α) secretion and activation epitope (CD107a and Mip-1β) expression. Pooled data (mean ± standard deviation) are shown for patients from the control (red circles) and vaccine (blue squares) arms. ns, not significant.

Figure 4.

T-cell clonality after ASCT and vaccination with mRNA-electroporated LCs. Next-generation deep sequencing of the TCR-V-β CDR3 was performed on CD4 and CD8 T cells isolated from PBMCs obtained at days 30, 90, and 120 after ASCT and compared with prevaccine levels (day 12). (A) Stacked bar plots of CD4 and CD8 T-cell repertoire composition from 6 representative patients (3 from vaccine arm, 3 from control arm). Each color represents a unique clone, with the higher-percentage clones at the top and lower-percentage clones underneath (low-frequency clones blend together in black). (B) Heat maps of interpatient overlap of CD4 and CD8 T-cell clones calculated using the Morisita similarity index (dark yellow = similar; dark green = dissimilar). V1-V9 along the x- and y-axes represent vaccinated patients. C1-C9 along the x- and y-axes represent control patients. (C) Violin plots representing the mean log fold change in CD4 and CD8 T-cell expansion. Each color represents an individual patient. The red dashed line represents the mean log fold change value in each group. D12, day 12; D30, day 30; D90, day +90; D120, day 120.