Abstract

Background: GvHD, intensity of ISP and infection are major causes of toxicity post-HSCT. Yet, no method reliably predicts these complications. A functional assay for immunity, which predicts risk of GvHD and infection and allows tailoring ISP and infection prophylaxis, is needed. The ImmuKnow is an assay of global T-cell function that measures increased ATP production after stimulating CD4+ T-helper cells and has been shown useful for managing ISP therapies in solid-organ transplantation. We hypothesized that ImmuKnow could assist in predicting risk of GvHD and infection and response to ISP post-HSCT.

Patients and Methods: Between January 2003 and May 2006, 34 adult allogeneic HSCT pts [mean age 47 years (range 22–71); 53% females; acute myelogenous leukemia, 8 pts; myeloma, 6 pts;] underwent blood sampling for determining ImmuKnow at various times post-HSCT (238 assays, mean of 7/pt). Results were correlated with clinical course (infection, stable, GvHD, response to ISP).

Results: During the testing period, GvHD was documented in 16 pts [(acute, n=7 pts; chronic, n=9 pts] and 53 infections occurred [CMV viremia (n=20); bacteremia (n=20); others (n=13)]. The median immune function (ng/mL ATP) of GvHD pts was significantly higher than that of clinically stable pts (342 +/−105 vs. 167 ng/mL +/−136 respectively), p<0.001. Pts with infections had a median 89 ng/mL ATP (+/−119), also statistically different (p=0.002) from stable pts. A pt with ATP value ≥ 300 ng/mL was more likely (RR=4) to develop GvHD than one with lower immune response. Similarly, there was a higher risk (RR=5) for infection in pts with an ATP ≤ 80 ng/mL. Relative risk curves for infection and GvHD intersected in the low immune response zone (140 ng/mL ATP). Following therapy for GvHD in 10 pts, ATP values rapidly decreased (193 ng/mL ATP +/−122) over 17 days (range 3–35) and were associated with improvement, while stable or increasing values (50 ng/mL ATP +/−99) were observed among 6 pts who failed to respond to GvHD therapy.

Conclusions: these data suggest that the FDA-approved ImmuKnow assay is an objective marker of risk for infection and GvHD, and of responsiveness to ISP therapy post-HSCT. Tailoring intensity and duration of ISP to risks of GvHD and infection in an individual pt may be possible and may improve outcomes. Validation of these preliminary data is ongoing.

Disclosure: No relevant conflicts of interest to declare.

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