*Purpose: Viral infections (VI) represent significant morbidity and mortality factors for KTx Pts. We previously showed more VI in BLT-treated Pts compared with CNI Pts and a higher VI risk at early conversion to BLT post-Tx. We also showed less CMV and EBV VI in HS than non-HS Pts due to IVIG and rituximab used for desensitization (DES). Here, we analyzed VI status in HS vs. non-HS KTx Pts who were converted to BLT within (<1yr) vs. (>1yr) post-Tx.

*Methods: 160 EBV sero+ KTx pts (48 HS, 112 non-HS) with conversion to BLT from CNI between 2012 & 2019 (89 Pts <1yr [median 3.6 M, 0.7-12.5 post-Tx), 71 Pts >1yr [median 43.1M, 12.6-117.3]) were included. 128 Pts received lymphocyte depletion and 32 anti-CD25 induction. All received standard viral prophylaxis for 6M post-Tx. CMV, EBV and BKV viremia were monitored by PCR, and viremia with >50 copies/PCR for CMV &EBV and >2500 copies/ml for BKV that required anti-viral therapy were analyzed.

*Results: Overall, EBV viremia was significantly less in HS vs. non-HS, likely due to rituximab depletion of B cell, reservoirs of EBV. There was no difference in CMV and BKV viremia in the two groups. Overall, CMV and BKV viremia was greater in patients converted to BLT <1yr post-Tx. This trend was greater in HS vs. non-HS. In contrast, EBV viremia was significantly greater in Pts converted to BLT >1yr than <1yr post-Tx and this trend was greater in non-HS Pts. There was no significant difference in CMV viremia rate by CMV sero status. 2 PTLD and 2BKAN occurred in 4 non-HS Pts with conversion <1yr.

*Conclusions: Differential viremia rates were observed in KTx Pts who received BLT, depending on the conversion timing and HS status. Recognizing these associations directs higher vigilance in monitoring the higher risk groups.

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