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Introduction: Immune reconstitution is often impaired for months to years in patients after allogeneic hematopoietic stem cell transplantation (HSCT) which predisposes them to a wide collection of clinical infections.
Primary herpes simplex virus (HSV) types 1 and 2 infections in immune-competent hosts results in long-term latent infections that can be associated with recurrent reactivations. After HSCT symptomatic HSV-1 reactivation predominantly manifests with involvement of the oropharyngeal, esophageal or tracheobronchial tracts.
Without prophylaxis HSV disease after HSCT occurs in approximately 70–80% of seropositive recipients. Although rarely life-threatening, HSV reactivation may cause severe oral and genital ulceration and in some cases even disseminated diseases such as encephalitis. Our center follows the current guidelines that recommend antiviral prophylaxis for HSV-seropositive allogeneic HSCT recipients against HSV infection which has reduced the incidence of HSV disease in the early phase after HSCT.
Methods: We retrospectively analyzed possible risk factors both by univariate and multivariate analysis for HSV reactivation in 382 HSV seropositive patients transplanted between 2005 and 2013 at our center. In addition we analyzed the impact of HSV reactivation on clinical outcome in this patient cohort with regards to; overall survival (OS), relapse free survival (RFS) and Transplant related mortality (TRM).
Results: The cumulative incidence was 18 % of early HSV reactivation (<90 days) in the patient material. A majority (67%) of the HSV infections occurred within 30 days after HSCT. HSV infection occurred a median of 20 days (5-90) after HSCT. The only risk factor observed for HSV reactivation both by univariate and multivariate analysis was age of recipient (P<0.01). The cumulative incidence of HSV reactivation in the different age subsets were: 0-20 years: 12.5%, 21-40 years 14.9%, 41-50 years 16.9%, 51-60 years 22.9% and >60 years 24.6%. There was no significant difference in OS, RFS or TRM in the patient material with regards to HSV reactivation. However, patients with malignant disease patients with HSV reactivation had significantly decreased OS compared to patients with no HSV reactivation (p=0.02). In patients with lymphoma this difference was even more prominent (p=0.002). There was also a significant decrease in RFS in this patient category (p<0.01).
Discussion: Despite antiviral prophylaxis there is still a substantial proportion of HSV reactivation in patients after HSCT. In our material we did not observe any risk factors except older patient age. While the OS and RFS was significantly decreased in lymphoma patients with HSV reactivation additional measures as intensified prophylaxis and additional therapy might be considered. Future studies regarding the mechanism of HSV reactivation and lymphoid malignancies are warranted.