Clinical assessment of anti-viral CD8+ T cell immune monitoring using QuantiFERON-CMV® assay to identify high risk allogeneic hematopoietic stem cell transplant patients with CMV infection complications

Abstract

The reconstitution of anti-viral cellular immunity following hematopoietic stem cell transplantation (HSCT) is crucial in preventing cytomegalovirus (CMV)-associated complications. Thus immunological monitoring has emerged as an important tool to better target pre-emptive anti-viral therapies. However, traditional laboratory-based assays are too cumbersome and complicated to implement in a clinical setting. Here we conducted a prospective study of a new whole blood assay (referred to as QuantiFERON-CMV®) to determine the clinical utility of measuring CMV-specific CD8+ T-cell responses as a prognostic tool. Forty-one evaluable allogeneic HSCT recipients underwent weekly immunological monitoring from day 21 post-transplant and of these 21 (51.2%) showed CMV reactivation and 29 (70.7%) developed acute graft-versus-host disease (GvHD). Patients with acute GvHD (grade ≥ 2) within 6 weeks of transplant showed delayed reconstitution of CMV-specific T-cell immunity (p = 0.013) and a higher risk of CMV viremia (p = 0.026). The median time to stable CMV-specific immune reconstitution was 59 days and the incidence of CMV reactivation was lower in patients who developed this than those who did not (27% versus 65%; p = 0.031). Furthermore, a failure to reconstitute CMV-specific immunity soon after the onset of CMV viraemia was associated with higher peak viral loads (5685 copies/ml versus 875 copies/ml; p = 0.002). Hence, QuantiFERON-CMV® testing in the week following CMV viremia can be useful in identifying HSCT recipients at risk of complicated reactivation.

Figure 1. Cumulative incidence of CMV-specific CD8+ T cell immune reconstitution and CMV reactivation in HSCT recipients.

Panel A: Reconstitution of CMV-specific T cell immunity according to donor and recipient CMV-serostatus. Panel B: CMV reactivation according to the development of GVHD grade ≥II within 6 weeks post transplant (p = 0.026, log-rank test). Panel C: Reconstitution of CMV-specific T cell immunity according to the development of GVHD grade ≥II within 6 weeks post transplant (p = 0.013, log-rank test).

Figure 2. Relationship between stable CMV-specific CD8+ T cell immune reconstitution and CMV reactivation.

Data presented in this graph shows the cumulative incidence of CMV reactivation according to the development of stable CMV-specific CD8+ T cell immune reconstitution by day 59.

Figure 3. Individual patient plots showing the relationship between CMV-specific CD8+ T cell immune reconstitution and virus reactivation.

QuantiFERON-CMV® readings are shown in black continuous lines; the threshold for positive QuantiFERON-CMV® reading (0.2 IU/ml) is indicated by a light continuous line. CMV viral loads are shown in dotted lines; the threshold for pre-emptive antiviral treatment (600 copies/ml) is indicated by a light dotted line. Anti-viral treatments are indicated by grey bars.

Figure 4. Effect of QuantiFERON-CMV® results on the maximum viral load.

Patients were grouped according to QuantiFERON-CMV® results (a) just prior to or on the day of first virus reactivation and (b) results immediately after evidence of virus reactivation (4.0±2.4 days, mean ± SD; range 1 to 8 days). Box and whisker plots show the upper and lower quartiles (box) with median value indicated as line in the box, while whiskers show maximum and minimum values.