Expanded clinical-grade NK cells exhibit stronger effects than primary NK cells against HCMV infection

Cytomegalovirus (CMV) reactivation remains a common complication and leads to high mortality in patients who undergo allogeneic hematopoietic stem cell transplantation (allo-HSCT). Early natural killer (NK) cell reconstitution may protect against the development of human CMV (HCMV) infection post-HSCT. Our previous data showed that ex vivo mbIL21/4-1BBL-expanded NK cells exhibited high cytotoxicity against leukemia cells. Nevertheless, whether expanded NK cells have stronger anti-HCMV function is unknown. Herein, we compared the anti-HCMV functions of ex vivo expanded NK cells and primary NK cells. Expanded NK cells showed higher expression of activating receptors, chemokine receptors and adhesion molecules;stronger cytotoxicity against HCMV-infected fibroblasts;and better inhibition of HCMV propagation in vitro than primary NK cells. In HCMV-infected humanized mice, expanded NK cell infusion resulted in higher NK cell persistence and more effective tissue HCMV elimination than primary NK cell infusion. A clinical cohort of 20 post-HSCT patients who underwent adoptive NK cell infusion had a significantly lower cumulative incidence of HCMV infection (HR = 0.54, 95% CI = 0.32–0.93, p = 0.042) and refractory HCMV infection (HR = 0.34, 95% CI = 0.18–0.65, p = 0.009) than controls and better NK cell reconstitution on day 30 post NK cell infusion. In conclusion, expanded NK cells exhibit stronger effects than primary NK cells against HCMV infection both in vivo and in vitro.

Comparable anti-CMV responses of transplant donor and third-party CMV-specific T cells for treatment of CMV infection after allogeneic stem cell transplantation

Adoptive transfer of cytomegalovirus(CMV)-specific cytotoxic T lymphocytes(CMV-CTLs)from original transplant donors or third-party donors was effective for the treatment of CMV infection after allogenic stem cell transplantation(allo-SCT),but the antiviral activity of CMV-CTL types has not been compared.To determine whether third-party CMV-CTLs provide comparable long-term antiviral efficacy to transplant donor CMV-CTLs,we first compared the antiviral abilities of transplant donors and third-party CMV-CTLs for treatment of CMV infection in two mouse models,compared the in vivo recovery of CMV-specific immunity,and analyzed the underlying mechanisms driving sustained antiviral immunity.The results showed that both donor and third-party CMV-CTLs effectively combated systemic CMV infection by reducing CMV pathology and tumor burden 28 days postinfusion.The in vivo recovery of CMV-specific immunity after CMV-CTL infusion was comparable in both groups.A detailed analysis of the source of recovered CMV-CTLs showed the proliferation and expansion of graft-derived endogenous CMV-CTLs in both groups.Our clinical study,which enrolled 31 patients who received third-party CMV-CTLs and 62 matched pairs of individuals who received transplant donor CMV-CTLs for refractory CMV infection,further showed that adoptive therapy with donor or third-party CMV-CTLs had comparable clinical responses without significant therapy-related toxicity.We observed strong expansion of CD8+tetramer+T cells and proliferation of recipient endogenous CMV-CTLs after CMV-CTL infusion,which were associated with a reduced or cleared viral load.Our data confirmed that adoptive therapy with third-party or transplant donor CMV-CTLs triggered comparable antiviral responses to CMV infection that might be mediated by restoration of endogenous CMV-specific immunity.