Insights into absence of lymphoma despite fulminant Epstein-Barr virus infection in patients with XIAP deficiency
Yizhe Sun, Janet Chou, Kevin D. Dong, Steven P. Gygi, Benjamin E. Gewurz
Yizhe Sun, Janet Chou, Kevin D. Dong, Steven P. Gygi, Benjamin E. Gewurz
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Research Article Infectious disease Virology

Insights into absence of lymphoma despite fulminant Epstein-Barr virus infection in patients with XIAP deficiency

Abstract

X-linked Lymphoproliferative Syndromes (XLP), arising from mutations in SH2D1A or XIAP genes, are characterized by fulminant Epstein-Barr virus (EBV) infection. Lymphomas occur frequently in XLP-1 and in other congenital conditions with heightened EBV susceptibility, but not in XLP-2. Why XLP-2 patients are apparently protected from EBV-driven lymphomagenesis remains a key open question. To gain insights, newly EBV-infected versus receptor-stimulated primary B cells from XLP-2 patients or with XIAP CRISPR editing were compared with healthy controls. XIAP perturbation impeded outgrowth of newly EBV-infected B cells, but not of CD40 ligand and interleukin-21–stimulated B cells. XLP-2–deficient B cells showed significantly lower EBV transformation efficiency than cells from healthy controls. Interestingly, EBV-immortalized lymphoblastoid cell proliferation was not impaired by XIAP knockout, implicating a XIAP role in early EBV B cell transformation. Mechanistically, nascent EBV infection activated p53-mediated apoptosis signaling, which was counteracted by XIAP in control cells. With XIAP deficiency, EBV markedly elevated apoptosis rates over the first 2 weeks of infection. IFN-γ, whose levels are increased with severe XLP2 EBV infection, markedly increased newly EBV-infected B cell apoptosis. These findings underscored XIAP’s crucial role in support of the earliest stages of EBV-mediated B cell immortalization and provide insights into the curious absence of EBV+ lymphoma in patients with XLP-2.

Authors

Yizhe Sun, Janet Chou, Kevin D. Dong, Steven P. Gygi, Benjamin E. Gewurz

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Figure 2

B cells from patients with XLP-2 demonstrate impaired EBV, but not CD40L/IL-21–driven outgrowth at early timepoints.

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B cells from patients with XLP-2 demonstrate impaired EBV, but not CD40L...
(A) Schematic diagram highlighting the XIAP mutation shared by XLP-2 Patient numbers 1 and 2. (B) Growth curve analysis of primary B cells from patients with XLP-2 or people in the control group that were infected with EBV on Day 0. Statistical significance of comparisons between the XLP-2 samples and Control no. 1 are indicated. (C) Growth curve analysis of primary B cells from patients with XLP-2 or controls treated with CD40L and IL-21, which was replenished every 3 days. Statistical significance of comparisons between the XLP-2 samples and Control no. 1 are indicated. (D) Growth curves of lymphoblastoid cells established from B cells from Patients 1 or 2 with XLP-2, or from 3 healthy controls. Statistical significance of comparisons between the XLP-2 samples and Control no. 1 are indicated. (E) EBV B cell transformation assay workflow. CD19+ B cells purified from PBMCs were plated and infected with serial dilutions of the Akata EBV strain, using a range of 0–100 EBV transforming units/well. Wells with B cell outgrowth were scored 4 weeks later. (F) EBV transformation assays of primary human B cells from XLP-2 Patient no. 1 or from 2 healthy controls, as in E. Shown are the mean ± SD percentages of wells with B cell outgrowth from n = 3 replicates. Mean ± SD fold change live cell numbers from n = 3 replicates, relative to Day 0 values, are shown (B–D). Statistical significance was assessed by 1-way ANOVA followed by Tukey’s multiple comparisons test (B–D, and F). *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.