Cytomegalovirus (CMV) is an important opportunistic infection in kidney transplant recipients (KTR). Whilst pre-emptive or prophylactic anti-viral regime reduce CMV complications, drug toxicity and resistance suggest that biomarker led stratification of risk may have value in guiding therapy.

Purpose: of the study was to determine peripheral blood frequency of CMV specific T lymphocytes 3 months post kidney transplantation (KTx) and to correlate this with CMV disease.

Methods: This single centre, prospective, observational study recruited 116 KTR, immunosuppressed with tacrolimus based triple immunosuppression. KTR with CMV serology (Donor (D)+/Recipient (R)-) received 3 months valganciclovir prophylaxis. Investigation and treatment of CMV disease was for clinical indication. CMV specific T cell responses (T-SPOT.CMV ELISPOT, Oxford Diagnostics Laboratories, Abingdon, UK) and viral load on stored samples (Roche LightCycler^®) were serially assessed from 3 months post KTx. This analysis categorized a T-SPOT.CMV test result as low if the maximum spot count in either antigen well was <50 spots per 250,000 cells; medium if 50-100; and high if >100.

Results: An interim analysis is reported for 79 KTR with test results available at 3 and 6 months. T-SPOT.CMV response at 3 months varied by sero-status and was medium-high in 49% of patients [D-/R- 16% (4/25); D-/R+ 93% (13/14); D+/R+ 86% (18/21) and D+/R- 21% (4/19)]. In the D+/R- group: none of 4 KTR with a medium-high response at 3 months developed CMV disease whereas 4 of 15 KTR with a low response developed CMV disease and 1 of 15 asymptomatic viremia. Between 3 and 6 months T-SPOT.CMV response increased from low to medium-high in 5 patients (1 D-/R+, 1 D+/R+, 3 D+/R-). All but one of these (D-/R+) sustained a significant episode of viremia although only one (D+/R-) then had CMV disease.

Conclusion: Most R+ recipients (86%) had a medium-high T-SPOT.CMV response at 3 months. The 4 D+/R- KTR with a medium-high response at 3 months post KTx remained free of CMV disease at 6 months post KTx (and remain so to >11 months). Although this study is not powered to comment further, this may be biologically significant and will be addressed in an ongoing larger study. This interim analysis indicates how such tests might guide personalized decisions regarding CMV management such as length of prophylaxis, particularly in the high risk D+/R- group.

CITATION INFORMATION: Ball S, Small A, Waite C. CMV Immune Monitoring with a CMV ELISPOT Test in Kidney Transplant Patients. Am J Transplant. 2016;16 (suppl 3).

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