Introduction: The primary treatment for polyomavirus BK viral infection (BKV) is a reduction in immunosuppression exposure. However this can lead to rejection and development of DSA which are independently associated with poor long-term allograft survival. Here we explore the prevalence of de novo DSA after treatment of BKV with an approach that includes lowered immunosuppression in combination with IVIG.

Methods: We identified all patients that received IVIG as part of their management for BKV. All patients were inititally treated for BKV infection by discontinuing mycophenolate and adding leflunomide. IVIG (2g/kg, max 140g) was administered to those who did not initially respond to this intervention. DSA screens were reviewed both prior to and after the development of BKV. The incidence of de novo DSA after IVIG administration and graft outcomes were observed.

Results: A total of 35 patients were identified, 12 of whom were pre-sensitized (PRA >30%). Median time to BK infection was 104 days from transplant. Average follow-up after BKV diagnosis was 616 days with a median of three DSA screens per patient during this time period. Thirteen (37%) had biopsy proven BKV nephropathy and 30 (86%) had a peak viral load of >10,000 copies/ml. The median peak viral load was 140,000 copies/ml.

No patients (0%) developed de novo DSA during the follow-up period. The median time to the first dose of IVIG from the time of BKV diagnosis was 57 days. Twenty-four patients (69%) received more than one dose of IVIG with a median of two doses given (IQ range 1-3). The median time between the first and second dose of IVIG was 44.5 days.

Patient survival was 91%. Death censored graft survival was 80%. BKV resolved in 12 patients (60%). The median time to resolution was 263 days. Four graft losses (11%) were due to BKV nephropathy and one from rejection. Median creatinine at last follow-up was 1.2 (range 1.1-2.1). Seven patients (23%) had rejection after BKV, 6 cell-mediated (CMR) and one antibody-mediated (AMR). The patient with AMR received the first dose of IVIG following the rejection episode.

Conclusion: There was no development of DSA in patients treated with IVIG despite a prolonged time period of lowered immunosuppression (mean 540 days). Rejection was kept to a minimum and was limited to CMR. There was good allograft function and survival in this cohort with severe BK infection.

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