Clinical-grade varicella zoster virus-specific T cells produced for adoptive immunotherapy in hemopoietic stem cell transplant recipients.

Background Aims: Varicella zoster virus (VZV) causes life-long latent infection in healthy individuals, which reactivates in 10-68% of stem cell transplant patients. Reconstituting immunity through adoptive transfer of T cells specific for VZV may aid in the prophylaxis and treatment of VZV infections. The potential for generating T cells specific for VZV using a clinically approved VZV vaccine strain was investigated.
Methods: The Varivax® vaccine was used to stimulate peripheral blood mononuclear cells from healthy donors. Only reagents approved for clinical manufacture were used. Monocyte-derived dendritic cells pulsed with Varivax (R) were used to stimulate autologous mononuclear cells at a responder to stimulator ratio of 10:1. On day 7, a second stimulation was performed; 20 U/mL interleukin (IL)-2 were added from day 7 and 50 U/mL IL-2 from day 14 onwards. Cell phenotype and functionality were assessed after 21 days of culture.
Results: A mean increase of 11-fold in cell number was observed (n= 18). Cultures were mainly T cells (mean CD3 (+) 89.7%, CD4 (+) 54.2%, CD8 (+) 28.7%) with effector and central memory phenotypes. Cells produced one or more T helper (Th)1 cytokine (interferon-γ, tumor necrosis factor-α and IL-2), and CD4 (+) (but not CD8 (+) ) cells expressed the cytoxicity marker CD107 when restimulated with VZV antigens.
Conclusions: We have demonstrated a clinically applicable method that yields high numbers of highly reactive T cells specific for VZV. We propose that reconstructing host immunity through adoptive transfer of VZV-specific T cells will reduce the frequency of clinical VZV infection in the period of severe immune suppression that follows allogeneic stem cell transplantation.