Cytomegalovirus (CMV) Cell-Mediated Immunity and CMV Infection After Allogeneic Hematopoietic Cell Transplantation: The REACT Study

Abstract

Background: Cytomegalovirus (CMV) infection remains an important cause of morbidity and mortality in allogeneic hematopoietic cell transplant (allo-HCT) recipients. CMV cell-mediated immunity (CMV-CMI) as determined by a peptide-based enzyme-linked immunospot (ELISPOT) CMV assay may identify patients at risk for clinically significant CMV infection (CS-CMVi).

Methods: The CS-CMVi was defined as CMV viremia and/or disease necessitating antiviral therapy. CMV-CMI was characterized as high when the intermediate-early 1 (IE-1) antigen spot counts (SPCs) were >100 (cutoff 1) or when the IE-1 and phosphoprotein 65 antigen SPCs were both >100 SPCs per 250 000 cells (cutoff 2), and a low CMV-CMI when SPCs were below these thresholds. In this prospective multicenter study, we evaluated CMV-CMI every 2 weeks from the pretransplant period until 6 months posttransplantation in 241 allo-HCT recipients with positive CMV serostatus. The primary endpoint was CS-CMVi occurring within 2 weeks of the last measurement of CMV-CMI.

Results: CS-CMVi occurred in 70 allo-HCT recipients (29%). CMV-CMI was low in patients who experienced CS-CMVi (94%), whereas those who had a high CMV-CMI were less likely to have CS-CMVi (P < .0001). Patients with CS-CMVi had higher all-cause mortality (P = .007), especially those with low CMV-CMI (P = .035). On multivariable analysis, CMV-CMI, sex, race, antithymocyte globulin, and steroid use were independent predictors of CS-CMVi, and the time from transplant to engraftment was the only predictor of mortality.

Conclusions: Measurement of CMV-CMI using a novel ELISPOT assay would be useful clinically to monitor allo-HCT recipients and distinguish between those at risk of developing CS-CMVi and requiring antiviral prophylaxis or therapy and those who are protected.

Keywords: CMV ELISPOT assay; cell-mediated immunity; cytomegalovirus; hematopoietic cell transplant; multicenter.

Figure 1.

Flowchart showing the number of patients enrolled in the study. Abbreviations: CMV, cytomegalovirus; CS-CMVi, clinically significant CMV infection; ELISPOT, enzyme-linked immunospot assay; HCT, hematopoietic cell transplant.

Figure 2.

Box plot of the number of spots produced in the enzyme-linked immunospot (ELISPOT) cytomegalovirus (CMV) assay for patients with and without clinically significant CMV infection (CS-CMVi) for the intermediate-early 1 (IE-1; A) and phosphoprotein 65 (pp65; B) antigens. The length of box represents the interquartile range (the distance between the 25th and 75th percentiles). The diamond in the box represents the group mean. The horizontal line in the box represents the group median. The vertical lines originating from the box extend to the group minimum and maximum values. For IE-1 level in patients with CS-CMVi, its median was equal to its 25th percentile and its minimum value.

Figure 3.

Correlation curve with intermediate-early 1 (IE-1) spot counts on the y-axis and phosphoprotein 65 (pp65) spot counts on the x-axis. Shown are values before the occurrence of clinically significant cytomegalovirus (CMV) infection (CS-CMVi) for 70 patients and maximum values for 171 patients who did not experience CS-CMVi.

Figure 4.

Cumulative incidence curves of clinically significant cytomegalovirus (CMV) infection (CS-CMVi) in patients with different CMV cell-mediated immunity (CMV-CMI) cutoffs. The curves show the likelihood of developing CS-CMVi in a particular patient at each time point. A, Cutoff 1 (intermediate-early 1 spot counts >100 as high CMV-CMI; P < .049). B, Cutoff 2 (IE-1 SPCs >100 and phosphoprotein 65 SPCs >100 as high CMV-CMI; P < .039). CMV-CMI (low/high) was a time-dependent variable in the cumulative incidence curves as it changed over time during the study period.

Figure 5.

Cumulative survival curves of patients with or without clinically significant cytomegalovirus infection (CS-CMVi).

Figure 6.

Cumulative survival curves of all patients using intermediate-early 1 (IE-1) >100 as high cytomegalovirus cell-mediated immunity (CMV-CMI) (cutoff 1). CMV-CMI level (high/low) and clinically significant cytomegalovirus infection (CS-CMVi) were time-dependent variables in the cumulative survival curves. There was only 1 significant difference among the 4 groups of patients: low CMV-CMI with CS-CMVi vs low CMV-CMI without CS-CMVi (P = .003).

Figure 7.

Probability curves for predicted protection against clinically significant cytomegalovirus infection of 4 typical cases of patients who received steroids during the study period: white male (A), white female (B), nonwhite male (C), and nonwhite female (D). Abbreviations: CS-CMVi, clinically significant cytomegalovirus infection; IE-1, intermediate-early 1 antigen; SPC, spot count.