GENOTYPIC CHARACTERISTICS, GENOMIC MUTATIONS OF BK POLYOMAVIRUS IN PATIENTS AFTER KIDNEY TRANSPLANTATION: A CROSS-SECTIONAL STUDY IN VIETNAM

Abstract

Purpose: BK polyomavirus (BKPyV) frequently reactivates in kidney transplant recipients during immunosuppressive therapy and triggers BKPyV-associated nephropathy (BKVN) and graft rejection. The virulence and the ability of viral replication to be related to the mutation status of BKPyV. The study aims to determine genotypic characteristics and genomic mutations of BKPyV in patients after kidney transplantation. Materials and Methods: A total of 201 patients underwent kidney transplantation were enrolled in the study. Serum, urine, and kidney biopsy samples were collected to detect BKPyV infection and BKVN. Genotypic and genomic mutations identified based on the VP1 (Virus Protein 1) gene region by sequencing and phylogenetic analysis. The presence of any single-nucleotide polymorphisms (SNPs) and changes in amino acid gene sequences VP1 (1630-1956) was recorded. Results: BKPyV infection was determined in 84 patients (41.8%). Among them, 8 patients (3.9%) were diagnosed with BKPyV-associated nephropathy. Genotypic analysis was performed in 40 patients with an average age was 39.7 years old, 82.1% male, the average duration of post-transplantation 1.56 ± 2.82 years, average serum creatinine 115.82 ± 29.85 µmol/L. Genotypic characteristics showed that BKPyV-I accounted for 25/40 (62.5%), BKPyV-IV observed in 15/40 (37.5%). Of note, BKPyV-I/b-1 was (100%) with BKV genotype I, whereas BKPyV-IV/a-1 (26.67%), BKPyV-IV/a-2 (6.67%), BKPyV-IV/c-1 (66.66%). Sequence analysis of VP1 region of BKPyV-I genotypes identified 5 mutant positions, of BKPyV-IV genotype presented 17 mutant positions, in which at position 1745 of BKPyV-IV appeared to change from A to G with the frequency of 13/15 samples (86.67%) resulted in amino acid change from N to S. There was no difference between the BKPyV genotypes with age, sex, viral load, and BKPyV-associated nephropathy. Conclusion: This study indicated that the BKPyV-I genotype was more common than BKPyV-IV, however genomic mutations that occur in the VP1 region of BKPyV-IV strains were more common than those of BKPyV-I.