Quantification of a low cellular immune response to aid in identification of pediatric liver transplant recipients at high-risk for EBV infection.

OBJECTIVE

Uncontrolled EBV infection leading to lymphoproliferative disease is a significant cause of morbidity in pediatric orthotopic liver transplant (OLT) recipients. Herein, we describe the use of a novel immune assay, which quantifies the lymphocyte immune response and correlates the value to risk for EBV infection.

METHODS

All patient data were prospectively collected between 2003 and 2005. The study included 18 pediatric liver transplant recipients, seven males and 11 females with a mean follow-up of 47 months post-OLT. Patient EBV load was monitored using real-time quantitative PCR (qPCR). The ATP release (ng/mL) of CD3+ lymphocytes after mitogenic stimulation with phytohemagluttinin (PHA; Cylex Corporation) was used to quantitate patient immune response. Patients were stratified by EBV load: low (<1000 copies/microg DNA), medium (1000-4000 copies/microg DNA), and high (>4000 copies/microg DNA).

RESULTS

Patients with low EBV loads had a significantly (p < 0.04) stronger immune response to PHA than patients with EBV load >1000 copies/microg DNA. Further analysis demonstrated that patients with ATP level <125 ng/mL had 100% probability of an EBV titer >4000 copies/microg DNA, when compared with 22% if the ATP level was between 125 and 400 ng/mL or only 15% if >400 ng/mL (p < 0.05). When immunosuppression was reduced, we observed an increase of the ATP release that correlated with a decrease of the EBV viral load.

CONCLUSION

In conclusion, this study investigates the use of a lymphocyte activation assay to closely measure the immunosuppression status of pediatric liver transplant recipients. Because measurement of EBV DNA load as a single parameter has a poor positive predictive value for development of PTLD, the association of these assays may be of help in the identification of patients at risk for PTLD.