Epstein-Barr virus (EBV) reactivation post allogeneic hematopoietic stem cell transplantation (HSCT) can lead to the outgrowth of EBV-infected B cells and the development of post-transplant lymphoproliferative disease (EBV-PTLD). In a series of Phase I and II clinical trials we have assessed the safety and clinical benefit associated with these transferred cells in allogeneic HSCT recipients.
Of 162 patients infused prophylactically only 1 (0.6%) developed EBV-PTLD, which occurred following the administration of steroids 3 weeks-post VST infusion. However, this patient responded to a second VST infusion after the steroids. 31 of 36 (86%) patients with elevated viral load (n=21) or biopsy-proven/probable LPD (n=15) achieved durable complete remissions and the infused cells persisted long term as demonstrated in 26 patients who received gene-marked VSTs that were detectable for up to 9 years post-infusion.
To extend the approach to additional viruses we initially developed methodology for using genetically modified antigen presenting cells approach to generate VSTs from donor peripheral blood that target CMV, EBV and adenovirus and showed that adoptively transferred donor-derived VSTs can reconstitute antiviral immunity to all three viruses and effectively treat established infections. More recently we have evaluated whether T-cell lines manufactured using overlapping peptide pools and extended the specificity to include HHV6 and BK. When administered to 11 recipients of allogeneic transplants, 8 of whom had up to four active infections with the targeted viruses, these VSTs proved safe in all subjects and produced an overall 94% virological and clinical response rate that was sustained long-term.
Another means of avoiding growing CTLs for individual patients is to bank lines that are then available as an off the shelf product of most closely HLA-matched allogeneic cytotoxic T lymphocyte lines. We evaluated this strategy in a multicenter study through the NHLBI Specialized Centers for Cell-Based Therapy (SCCT) program in HSCT recipients who had viral reactivation or infection refractory to standard therapy. The overall cumulative incidence of first CR/PR in 50 patients based on viral load by day 42 was 74.0% (73.9% for CMV, 66.7% for EBV and 77.8% for adenovirus).
In a follow up study using the peptide induced VSTs that recognize 5 viruses, based on viral load measurements by quantitative PCR a single VST infusion successfully controlled active infections in 19/21 evaluable patients. These results demonstrate the feasibility and safety of 3rd party multivirus-directed VSTs, generated by direct stimulation of PBMCs with synthetic peptides and administered as an off the shelf product.
Heslop HE, Tzannou I, Omer B, Brenner MK, Leen AM, Rooney CM. Immunotherapy with virus-specific T cells. 2016.