Immunodeficiency Genes Are Associated with EBV Positive Malignancies and Hemophagocytic Lymphohistiocytosis That Can be Cured By Allogeneic Hematopoietic Stem Cell Transplantation

Background: Epstein-Barr virus (EBV) positive hematological malignancies and EBV-associated hemophagocytic lymphohistiocytosis (HLH) are serious illness that is related with chronic active EBV infection (CAEBV). Recently, more and more immune-related gene mutations have been identified to associate with the EBV positive hematological diseases. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative therapy for above diseases.

Aim: In present clinical study, the germline gene mutations associated with EBV positive hematological malignancies and EBV positive HLH were analyzed and the outcomes of allo-HSCT in those diseases were investigated.

Methods: Between January 2018 and June 2021, 7 patients with EBV positive hematological diseases (lymphoma 3, aggressive NK-cell leukemia (ANKL) 1, secondary HLH 3) who received allo-HSCT in our hospital were included. Blood samples from patients, parents and potential related donors were collected before transplantation and whole exome sequencing of the blood DNA samples was performed to detect and analyze their relevance with the clinical features before and after allo-HSCT. The median age was 23 (5-31) years old. The median disease course before transplant was 6 (3-38) months. Before allo-HSCT, 3 patients (HLH 1, lymphoma 1, ANKL 1) were in non-remission (NR), 2 patients with lymphoma were in partial remission (PR) and the other two patients with HLH were in complete remission (CR). Five patients received allo-HSCT from haploidentical donors and 2 patients from unrelated donors (HLA 10/10, 9/10 matched). Myeloablative conditioning regimen with busulfan (0.8mg/kg iv q6h, 3 days)/etoposide (200mg/m ², 3 days)/fludarabine (30mg/m ², 5 days) /rabbit anti-T-cell globulin was used. Cyclosporine, mycophenolate mofetil and short-term methotrexate were employed for graft-versus-host disease (GVHD) prophylaxis.

Results: All patients achieved durable engraftment. Plasma EBV-DNA was positive in three patients (1200, 880, 84000 copies/ml, respectively) before transplant and has been negative in all patients after transplant. One patient had gastrointestinal bleeding caused by EBV enteritis. Two patients had CMV viremia. Three patients developed grade III acute GVHD and two had extensive chronic GVHD. All GVHD was resolved with immune-suppressants. With the median follow-up time of 21 (7-36) months, all patients are alive and free of their diseases. Seven disease-related gene mutations were detected including FANCA p.S1088F, TGFBR2 p.T315M, IRF7 p.K446R, PRF1 p.R4C, MPEG1 p.P316S, STX11 p.R49Q, and UNC13D p.G863D. The first 5 gene mutations were detected in the patients with lymphoma and ANKL, and the last 2 gene mutations were detected in the patients with HLH. FANCA is associated with bone marrow failure and the other genes are associated with primary immunodeficiency, all of these gene mutations have been reported and affect in part the function of the genes. In particular, STX11 p.R49Q and UNC13D p.G863D have also been reported in HLH patients and the NK cell activity of these patients is lower than normal levels. Apart from the defined gene mutations in primary HLH, recently, many new immunodeficiency gene mutations have been reported to associate with EBV positive malignancies and HLH which suggests immunodeficiency might play a role in the etiology of the diseases. The gene mutations we reported here might be the main gene mutations associated with disease susceptibility and infection risk.

Conclusion: Our preliminary results have shown the gene mutation profile related to EBV positive hematological malignancies and HLH. With our transplant protocol, durable reconstitution of hematopoiesis and immune from healthy donors has been achieved successfully which has resulted in 100% disease-free survival and no transplant-related death. Allo-HSCT is a safe and effective curative modality for EBV positive hematological malignancies and HLH.