Durable immunity to EBV after rituximab and third-party LMP-specific T cells: a Children's Oncology Group study

Abstract

Posttransplant lymphoproliferative disease (PTLD) in pediatric solid organ transplant (SOT) recipients is characterized by uncontrolled proliferation of Epstein-Barr virus-infected (EBV+) B cells due to decreased immune function. This study evaluated the feasibility, safety, clinical and immunobiological outcomes in pediatric SOT recipients with PTLD treated with rituximab and third-party latent membrane protein-specific T cells (LMP-TCs). Newly diagnosed (ND) patients without complete response to rituximab and all patients with relapsed/refractory (R/R) disease received LMP-TCs. Suitable LMP-TC products were available for all eligible subjects. Thirteen of 15 patients who received LMP-TCs were treated within the prescribed 14-day time frame. LMP-TC therapy was generally well tolerated. Notable adverse events included 3 episodes of rejection in cardiac transplant recipients during LMP-TC therapy attributed to subtherapeutic immunosuppression and 1 episode of grade 3 cytokine release syndrome. Clinical outcomes were associated with disease severity. Overall response rate (ORR) after LMP-TC cycle 1 was 70% (7/10) for the ND cohort and 20% (1/5) for the R/R cohort. For all cohorts combined, the best ORR for LMP-TC cycles 1 and 2 was 53% and the 2-year overall survival was 70.7%. vβT-cell receptor sequencing showed persistence of adoptively transferred third-party LMP-TCs for up to 8 months in the ND cohort. This study establishes the feasibility of administering novel T-cell therapies in a cooperative group clinical trial and demonstrates the potential for positive outcomes without chemotherapy for ND patients with PTLD. This trial was registered at www.clinicaltrials.gov as #NCT02900976 and at the Children's Oncology Group as ANHL1522.

Graphical abstract

Figure 1.

Patient treatment assignments and outcomes. RTX indicate rituximab 375 mg/m² weekly × 3 doses and cycle length, 21 days; LMP, 2 × 10⁷ cells per m² weekly × 2 and cycle length, 42 days. Alive, alive with further therapy and/or relapse; CCR, continous complete remission; DOAC, dead of other causes; DOD, dead of disease.

Figure 2.

Production of LMP-TCs. In brief, donor peripheral blood mononuclear cells (PBMCs) are sorted into B cells, T cells, and monocytes. B cells are transfected with laboratory strain EBV and grown into the lymphoblastoid cell line (LCL). LCL and monocytes are transduced with a replication-incompetent adenoviral vector expressing LMP 1 and 2. T cells are cocultured with LMP1 and 2 expressing LCLs and monocytes in the presence of interleukin-2 (IL-2) to produce a LMP-specific T-cell product containing both CD4⁺ and CD8⁺ cells.

Figure 3.

Outcomes and responses to rituximab and/or LMP-TCs. Swimmer plots for ND patients (A) and patients with refractory disease (B), EFS (C), and OS (D) for ND patients and patients with R/R disease. The P value for the log-rank test between the ND patients and the patients with R/R disease is .024 for EFS and .049 for OS.

Figure 4.

Rejection episodes did not correlate with increasing EBV-specific immunity. All patients had stable or decreasing EBV immune response, as evaluated by ELISpot assay (and reported in IFN-γ spot forming cells (SFC) per100 000 cells). Mononuclear cells isolated from peripheral blood samples were cocultured with LCLs; after 10 days, cells were evaluated by ELISpot to assess IFN-γ release when plated with LCLs. Patient A1 had no evidence of EBV-specific immune response at time of rejection (A). EBV-specific immune response were decreasing at time of rejection in patients C3 and A12 (B-C). ∗ indicates that data were not available at these time points. IFN-γ, interferon gamma; SFC, spot forming cells.

Figure 5.

Persistence of EBV-specific immune response. (A) Persistence of EBV-specific immune responses of responders (blue) as compared with those of nonresponders (red) in new diagnosis stratum is evident on day 90 (A). Patients with CR on day 41 demonstrated EBV-specific immune response while maintaining negative EBV viral load through 3 months after infusion (B). Patients with PR maintained EBV-specific immune response (C). Patients with PD had declining EBV-specific immune response; both patients received further therapy after day 41 evaluation with PD (D).

Figure 6.

TCR sequences unique to LMP-TC product expanded after infusion and were maintained in responders. Patient A3, with CR and with TCR sequences unique to product persistent at 11 months (A); patient A4, CR with TCR sequences until 8 months (B); patient A7, PR with sequences present until 17 months (C); patient C2, with PD, had declining unique TCR sequences at second follow-up time point, and patient received further therapy with CAR-T. After CAR-T, evidence of expansion of novel TCR sequences were again evident (D). Diversity of TCR clones present in LMP-TC products (E). CAR-T, chimeric antigen receptor T-cell therapy.