A New Duplication in 668 to 672 Sites of UL54 Gene in Cytomegalovirus Ganciclovir Resistant Liver Transplanted Patients

Background: In liver transplant recipients, human Cytomegalovirus (CMV) infection is a significant concern. Ganciclovir is the preferred medication for treating widespread CMV infections. In some cases, patients might require high doses of treatment for CMV infections that are resistant to ganciclovir, although liver transplant patients who have received extended ganciclovir and valganciclovir prophylaxis have reported infrequent cases of ganciclovir-resistant CMV infections. Mutations in the UL54 gene, responsible for encoding deoxyribonucleic acid (DNA) polymerase, can result in resistance. Objectives: In this study, the focus was on UL54 mutations and their association with ganciclovir resistance. Methods: In this study, 23 liver transplant recipients who were admitted to the transplant departments of Namazi and Abu Ali Sina hospitals within 2015 and 2017 were examined. Cytomegalovirus infection was then confirmed in them using the quantitative real-time polymerase chain reaction (PCR) method. The UL54 mutations were found after electrophoresis using the nested PCR method, and the PCR products were subsequently sequenced using the Sanger method. Sequence analysis and locating of UL54 mutations were performed using Finch software (version 1.4.0). Results: After sequencing 52 samples from 23 patients, 25 mutations in the UL54 gene were identified in 9 patients who were CMV-infected, occurring at a median of 32 days after transplant. These mutations, including S655L (10/9, 40%), N685S (8/9, 32%), F669L (4/9, 16%), A688V (2/9, 8%), and the novel AK124703.1: p.V668-G672dup (1/9, 4%), were detected in 9 liver transplant recipients over a median period of 2 years in the UL54 gene. Furthermore, a phylogenetic analysis was conducted to investigate the origins of these mutations in CMV isolated from the Iranian population. Conclusions: Considering that treatment with the drug ganciclovir has led to resistance mutations, particularly the new AK124703.1:p.V668-G672dup mutation, and inefficiency in treatment, it is necessary to determine drug-resistant CMV strains and closely monitor these patients. This includes determining viral load, assessing response to treatment, and identifying non-response at regular intervals until the viral load is completely eradicated in order to ensure the effectiveness of the treatment.