Detection of ganciclovir resistance after valacyclovir-prophylaxis in renal transplant recipients with active cytomegalovirus infection

Whether valaciclovir (VCV) prophylaxis could be responsible for ganciclovir (GCV)-resistance of Human cytomegalovirus (HCMV) in transplantation has never been documented. A multicentric retrospective pilot study was undertaken to detect GCV-resistance through mutations within the UL97 gene in renal transplant recipients who experienced active HCMV infection and received valacyclovir prophylaxis. Twenty-three patients who experienced HCMV antigenaemia or DNAemia during or at the end of prophylaxis were included. UL97 genotyping was carried out on peripheral blood samples, using a nested in-house PCR, which amplified the full-length UL97 gene. One patient has a resistance-related mutation (M460I); the major risk factor for emergence of resistance in this patient was the presence of early and persistent antigenaemia. GCV-resistance during VCV-prophylaxis was rare after renal transplantation. However, special attention must be paid to patients developing early active HCMV infection under prophylaxis.