Reduction in CMV and Adenovirus Viremia after Haploidentical Donor Transplantation Utilizing CD45RA Depletion and NK Cell Infusion

Background. T-cell depletion is often used to reduce graft-vs-host disease in haploidentical donor hematopoietic cell transplantation (HCT). However, the absence of adoptively transferred T-cells may increase graft failure, relapse, and infection. Novel methods have been developed to more selectively deplete naïve T cells and preserve memory T cells. Depletion of CD45RA+ cells can provide robust early recovery of diverse memory T-cell populations in haploidentical donor transplantation, and may provide increased immunity against viral infections. Likewise, the provision of additional donor NK cells may reduce viral complications.

Patients and Methods. Sixty-seven patients received initial allogeneic HCT on 3 consecutive IRB approved haploidentical donor HCT trials at St. Jude Children's Research Hospital from 2005 to 2015. CD3-depletion was used in 41 recipients, and CD45RA-depletion was used in 26. All patients received similar preparative doses of fludarabine, thiotepa, and melphalan. Patients with CD3-depleted grafts received OKT3 (n=20) or Campath (n=21), and all 41 received rituximab on Day 0 as EBV prophylaxis. Patients with CD45RA-depleted grafts (n=26) did not receive antibody therapy, but instead received total lymphoid irradiation and a dose of cyclophosphamide added to the preparative backbone. Donor NK cells were given Day +6.

Peripheral blood was tested for CMV, EBV, and adenovirus using quantitative PCR at least weekly until day +100, and then as indicated. The first 180 days post-HCT were evaluated. Fisher's exact test was used to compare two proportions.

Results. Patients with CD3-depletion received a median 0.04 (range: 0.01 - 0.15) x 10⁶ CD3+ cells/kg, and patients with CD45RA-depletion received a median 80.07 (range: 16.08 - 528.52) x 10⁶ CD3+ cells/kg.

CMV reactivation occurred in 23 of 41 patients (56.1%) with CD3-depletion and 5 of 26 patients (19.2%) with CD45RA-depletion (p=0.005). Differences occurred predominantly in those CMV seropositive recipients who received grafts from CMV seropositive donors, as CMV was detected in 22 of 24 (91.7%) +/+ patients with CD3-depletion and 4 of 11 (36.4%) +/+ patients with CD45RA-depletion (p=0.001). Of the 23 patients with CMV after CD3-depletion, the peak viral load was a median 4.49 log₁₀ copies/mL blood (range: <2.7 - 6.87). Of the 5 patients with CMV after CD45RA-depletion, the peak viral load was a median 3.81 log₁₀ copies/mL blood (range: <2.7 - 4.38). Of the 23 patients that experienced CMV following CD3-depleted HCT, 18 (78.3%) received antiviral therapy, 8 (34.8%) received donor lymphocyte infusions (DLI) for treatment. Of the 5 patients that reactivated CMV following CD45RA-depleted HCT, 4 (80%) received antiviral therapy, none received DLI for treatment.

EBV was detected in 7 of 41 (17.1%) patients with CD3-depletion and 5 of 26 patients (19.2%) with CD45RA-depletion (p=1). Of the 7 patients with EBV in the CD3-depletion group, 3 received rituximab, and 1 received rituximab, chemotherapy, and DLI. Overall 4 of 41 patients (9.8%) with CD3-depletion received EBV-directed therapy, compared to 0 of 26 patients with CD45RA-depletion (p=0.15).

Adenovirus viremia was detected in 11 of 41 patients (26.8%) with CD3-depletion and 1 of 26 patients (3.8%) with CD45RA-depletion (p=0.02). Of the 11 patients with CD3-depletion, the median peak viral load was 3.14 log₁₀ copies/mL DNA (range: 2.03 - 4.11). The patient with adenovirus following CD45RA-depleted transplant had a peak viral load that was below the threshold of quantification (2 log₁₀ copies/mL DNA). Of the 11 patients with adenovirus after CD3-depletion, 9 (81.8%) were given cidofovir, 4 (36.4%) were given DLI for treatment. The patient with adenovirus after CD45RA-depletion received cidofovir.

Conclusion. CD45RA-depletion has been shown to effectively deplete naïve T cells while providing substantial memory T-cell populations in the early post-HCT period. The significant reduction in CMV and adenovirus detection in the blood of patients with CD45RA-depletion suggests that adoptive transfer of memory T cells provides protection against these viruses in the early post-HCT period. The incidence of EBV was not significantly different - indicating that in vivo B-cell depletion by rituximab in CD3-depletion recipients and use of CD45RA-depletion may have similar efficacy in minimizing EBV reactivation.