BK Polyomavirus Prevalence in Renal Diseases: Associations with Immunosuppressants and Lymphocyte Subsets.

Background: BK polyomavirus (BKV), a latent pathogen in immunocompromised individuals, poses significant risks in renal-associated diseases (RD).

Methods: This study recruited 88 healthy control (HC) individuals and 271 patients with RD, including 96 connective tissue diseases with renal involvement (CTD-RI), 90 chronic kidney disease (CKD), 66 urological tumors (UT), 19 kidney transplantation (KT), at Peking Union Medical College Hospital from January 2020 to September 2021. The BKV-DNA qPCR detection kit was evaluated in terms of lowest detection limit, linear range, accuracy, precision, analytical specificity. Urine, serum, and plasma specimens from 17 UT patients were detected simultaneously to evaluate the detection sensitivity of various sample types. The positive rates and loads of BKV-DNA were compared among the various groups. The difference in immunosuppressants use between BKV-DNA positive and negative groups was compared in patients with CTD-RI. Furthermore, the correlations between BKV-DNA loads and the counts of lymphocyte subsets were explored in the CTD-RI group.

Results: The BKV-DNA qPCR detection kit has satisfactory sensitivity, linear range, reproducibility, accuracy, and specificity to detect the presence and loads of BKV-DNA. Urine specimens are more sensitive for BKV-DNA detection than serum and plasma. The CTD-RI and UT groups had higher BKV-DNA positive rates (49.0% and 31.8%, respectively) and loads (median: 5.69 log10 copies/mL and 6.03 log10 copies/mL, respectively) compared to the HC group (positive rate 12.5%, load median 3.96 log10 copies/mL). Multivariate logistic regression analysis indicated that the use of mycophenolate mofetil (MMF) was associated with a reduced risk of BKV (odds ratio and 95% confidence interval: 0.27 (0.09-0.78), P=0.015). The trends toward negative correlations between the BKV-DNA loads and the counts of CD19+ B cells, CD4+CD28+ T cells, CD45RA+CD4+ T cells, and naive CD4+ T cells were observed.

Conclusion: These findings support monitoring BKV-DNA in high-risk RD patients to guide immunosuppressant use and mitigate renal injury. Future long-term follow-up and multicenter large-scale cohort studies are necessary to further clarify the role of BKV in RD.