Long-Time Remission of Epstein-Barr Virus Associated Hemophagocytic Lymphohistiocytosis by Interferon-α Treatment

Introduction to Hemophagocytic Lymphohistiocytosis and Epstein-Barr Virus
Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome characterized by excessive immune activation, cytokine dysregulation, and multi-organ dysfunction. Epstein-Barr virus (EBV), a ubiquitous herpesvirus, is a well-recognized trigger for secondary HLH, particularly in cases of chronic active EBV (CAEBV) infection. CAEBV is defined by persistent or recurrent infectious mononucleosis-like symptoms lasting over three months, accompanied by high EBV DNA loads in peripheral blood and infiltration of tissues by EBV-infected lymphocytes. While pediatric HLH has been extensively studied, adult-onset EBV-associated HLH remains poorly understood and carries a dismal prognosis, with long-term survival rates as low as 13% despite aggressive therapies.

Case Presentation: Clinical History and Diagnostic Findings
A 59-year-old Chinese woman presented with a one-month history of fatigue, fever, and pancytopenia. Three years prior, she had been diagnosed with CAEBV based on recurrent fevers, elevated EBV serology, and detectable EBV DNA in peripheral blood. Physical examination upon admission revealed no hepatosplenomegaly, lymphadenopathy, or signs of pulmonary infection. Initial laboratory tests demonstrated severe cytopenias: white blood cell count 0.92×10⁹/L (normal: 4–10×10⁹/L), hemoglobin 66 g/L (normal: 115–150 g/L), and platelets 15×10⁹/L (normal: 100–300×10⁹/L). Liver function abnormalities included aspartate transaminase 142 U/L (normal: 13–35 U/L) and alanine aminotransferase 44 U/L (normal: 7–40 U/L). Coagulopathy was evident with fibrinogen 0.81 g/L (normal: 2–4 g/L) and D-dimer 18.35 mg/L (normal: <0.5 mg/L). Hyperferritinemia (8,500 ng/mL; normal: 20–200 ng/mL) and elevated soluble interleukin-2 receptor (sIL-2R; 13,200 U/mL; normal: 45–1,100 U/mL) further supported HLH diagnosis. Bone marrow examination showed mild hemophagocytosis without lymphoma or clonal lymphoproliferation. Serum EBV-DNA load was 1.99×10³ copies/mL.

Therapeutic Intervention: HLH-2004 Protocol with Interferon-α
The patient met diagnostic criteria for EBV-associated HLH based on fever, cytopenias, hypertriglyceridemia (3.02 mmol/L), hypofibrinogenemia, elevated ferritin, and sIL-2R. Immediate treatment with the HLH-2004 protocol was initiated, comprising dexamethasone, etoposide, and cyclosporin A. Additionally, subcutaneous recombinant human interferon (IFN)-α2b at 300 million units was administered every other day. Within two weeks, her fever resolved, and hematological parameters improved. By four weeks, complete blood counts and coagulation profiles normalized: white blood cells 4.5×10⁹/L, hemoglobin 120 g/L, platelets 150×10⁹/L, fibrinogen 2.8 g/L, and D-dimer 0.3 mg/L. Liver enzymes returned to normal ranges. EBV-DNA decreased to 1.02×10² copies/mL but remained detectable.

Maintenance Therapy and Long-Term Outcomes
Chemotherapy agents (etoposide, dexamethasone, cyclosporin A) were tapered and discontinued after six weeks. IFN-α2b was continued as monotherapy, gradually reduced to weekly injections over six months. During three years of follow-up, the patient maintained complete clinical remission despite persistent low-level EBV viremia (10–100 copies/mL). Serial imaging showed no hepatosplenomegaly or lymphadenopathy, and bone marrow evaluations confirmed absence of hemophagocytosis or malignant transformation.

Mechanistic Insights: Dual Roles of Interferon-α
This case highlights IFN-α’s dual antiviral and immunomodulatory effects in EBV-HLH. IFN-α directly inhibits EBV replication by suppressing viral DNA polymerase activity and impairing promoter activation of latent viral genes. Simultaneously, it modulates cytokine networks by downregulating proinflammatory mediators like interleukin-18 and interferon-γ (IFN-γ), which drive macrophage activation and tissue damage in HLH. The sustained remission despite low-level EBV persistence suggests IFN-α’s efficacy in controlling viral reactivation and preventing recurrent immune hyperactivation.

Contrasting Pediatric and Adult HLH Paradigms
Pediatric HLH management has advanced with standardized protocols like HLH-94 and HLH-2004, achieving survival rates of 55–70%. In contrast, adult EBV-HLH exhibits distinct pathophysiology, often complicated by CAEBV and T/NK-cell lymphoproliferative disorders. Traditional therapies yield poor outcomes, with mortality exceeding 80% in some cohorts. The HLH-2004 regimen alone often fails to sustain remission in adults, necessitating maintenance strategies. Recent FDA approval of emapalumab, an anti-IFN-γ monoclonal antibody, underscores cytokine-targeted approaches. However, this case demonstrates IFN-α’s potential as a low-cost alternative for long-term disease control.

Clinical Implications and Future Directions
The durable remission in this patient challenges conventional paradigms favoring indefinite chemotherapy or hematopoietic stem cell transplantation for EBV-HLH. Key observations include:

Rapid Response: Normalization of hematological and biochemical parameters within four weeks, faster than typical HLH-2004 outcomes.
EBV Suppression: Despite persistent low-level viremia, clinical remission was maintained, suggesting a threshold effect for viral load-triggered inflammation.
Safety Profile: No IFN-α-related adverse effects (e.g., cytopenias, neuropsychiatric symptoms) were reported, supporting its tolerability in prolonged use.

Further studies should explore IFN-α dosing schedules, combination therapies with antivirals (e.g., valganciclovir), and biomarkers predicting treatment response. Comparative trials against emerging biologics like emapalumab are warranted to establish IFN-α’s role in adult HLH management.

Conclusion
This case provides compelling evidence for IFN-α as an effective maintenance therapy in adult EBV-associated HLH, achieving long-term remission without intensive chemotherapy. By targeting both viral replication and cytokine dysregulation, IFN-α addresses core disease mechanisms, offering a viable strategy for this high-mortality condition. The findings advocate for expanded clinical evaluation of IFN-α in HLH treatment protocols, particularly in resource-limited settings.

doi.org/10.1097/CM9.0000000000000947

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