Different Epstein-Barr Virus DNA Load and Immune Reconstitution Following Hematopoietic Stem Cell Transplantation Depending on Antithymocyte Globulin Preparation.

Epstein-Barr virus (EBV)-associated lymphoproliferative disease (LPD) is a serious complication following hematopoietic stem cell transplantation (HSCT). In 86 patients undergoing HSCT in a single center we prospectively performed a quantitative EBV-specific polymerase chain reaction in peripheral blood mononuclear cells (PBMC) weekly after HSCT. Cellular immune reconstitution was monitored by flow cytometric analysis on days 30 and 60 after transplantation. We observed an EBV reactivation (>10³ EBV-genome copies/10⁵ PBMC) only in patients who received antithymocyte globulin (ATG) for immunosuppression. 15 of 46 patients (33%) who received ATG experienced EBV reactivation. Interestingly, we found a similar incidence of EBV reactivation in 7 of 21 patients (33%) who received ATG (Fresenius) at a median total dose of 40 mg/kg and in 8 of 26 patients (31%) who received ATG (Sangstat) at a median total dose of 20 mg/kg. However, in patients with ATG (Fresenius) EBV reactivation was observed only in the range between 10³ and 10⁴ EBV-genome copies/10⁵ PBMC and no EBV-associated LPD occurred. In contrast, in patients with ATG (Sangstat) EBV reactivation was always greater than 10⁴ EBV-genome copies/10⁵ PBMC. Median values for CD3+ cells were 157.7/μl versus 1.5/μl on day 30 and 327.0/μl versus 15.5/μl on day 60 in the group receiving ATG (Fresenius) or ATG (Sangstat), respectively. For CD3+CD4+ cells the corresponding numbers were 57.8/μl versus 0.5/μl on day 30 and 90.8/μl versus 10.0/μl on day 60. Median values for CD3+CD8+ cells were 89.4/μl versus 0.3/μl on day 30 and 237.3/μl versus 9.4/μl on day 60 in the group receiving ATG (Fresenius) or ATG (Sangstat), respectively. Patients with ATG (Sangstat) had significantly lower numbers of CD3+, CD3+CD4+, and CD3+CD8+ cells than patients with ATG (Fresenius) on day 30 (P <.001) and day 60 (P <.03). Four patients who received ATG (Sangstat) developed EBV-associated LPD at a median of 80 days after HSCT. The increase of EBV-genome copies occurred 1–5 weeks before the onset of LPD. After treatment of LPD 3 of 4 patients demonstrated a dramatic decrease of EBV-genome copies and survived, while the fourth patient died of lymphoma. All 4 patients with EBV-associated LPD presented with a high copy number (>10⁴ EBV-genome copies/10⁵ PBMC). In contrast, 79 patients who had a copy number lower than 10⁴ EBV-genome copies/10⁵ PBMC did not develop EBV-associated LPD (P <.001). This finding prompted us to start pre-emptive therapy in patients with a high copy number for prevention of EBV-associated LPD. Three patients developed a high viral load (>10⁴ EBV-genome copies/10⁵ PBMC). Pre-emptive therapy was performed with a single dose of rituximab (375 mg/m²) at a median of 52 days after HSCT. Following administration of rituximab a dramatic decrease of EBV-genome copies and B cells was observed. In all 3 patients no EBV-associated LPD occurred until 6 months after rituximab infusion. We conclude that in comparison to ATG (Fresenius) the use of ATG (Sangstat) as part of the conditioning regimen leads to a significant delay in T-cell reconstitution and to a significantly higher increase of EBV DNA load which predicts for EBV-associated LPD. Pre-emptive therapy with rituximab results in a dramatic decrease of EBV-genome copies and B cells and appears to be effective for preventing EBV-associated LPD.