Immune Function Assay (Immunknow) Drop Over First 6 Months After Renal Transplant: A Predictor of Opportunistic Viral Infections?

Background. The Immuknow assay (IKA; Cylex) is a T-cell immune function assay that evaluates immunoreactivity in immunocompromised patients. The aim of this study was to analyze IKA values in a cohort of kidney transplantation (KT) recipients to investigate correlations between single-time point low IKA values and their trend over time with cytomegalovirus (CMV) or BK virus (BKV) reactivation. Methods. A total of 118 adult patients receiving deceased-donor KT were enrolled (55.6 +/- 11.9 years old; 79 [66.9%] male). IKA CMV and BKV viremia determinations and were performed at months 1, 3, and 6 after surgery. Results. Overall, 272 IKA determinations were performed: IKA values significantly decreased from month 1 (422 +/- 184 ng/mL) to month 3 (330 +/- 159 ng/mL; P < .001) and from month 3 to month 6 (300 +/- 128 ng/mL; P = .030). IKA values did not correlate with renal function or viral reactivation at any time. However, patients with either CMV or BKV viremia had a trend to higher IKA values at month 1 and lower IKA values at month 6, even if the difference did not reach a statistical significance (P = .115). Conclusions. Our study suggests that presence of low immunologic reactivity (IKA <225 ng/mL) is not associated with an increased risk of CMV and BKV reactivation over the 1st 6 months after KT. However, a trend to a more pronounced drop in IKA values over time was observed in patients with viral reactivation. These preliminary results suggests that drop in IKA values within the 1st post-KT months, unlike single-time point immune function assay, may predict the risk of opportunistic viral infections.