High reactivation of BK virus variants in Asian Indians with renal disorders and during pregnancy.

There is resurgence of interest in the study of occurrence, genotype and pathogenic associations of human Polyomavirus BK and JC in recent years. In the present study, we have ascertained the presence of BK virus shed in the urine samples of pregnant women and immunocompromised patients, for the first time in Asian Indian population, and have also characterised the prevalent genotypes of the non-coding control regions (NCCRs) of these natural isolates. The results strongly suggest a very high incidence, as well as degree, of BK virus reactivation in this population groups assayed. Approximately 65% of the patients and pregnant women together, tested positive based on polymerase chain reaction (PCR) analysis, and these results were further confirmed by Southern hybridisation and dot blot against BKV specific probes. The NCCRs of the several Indian endemic strains were analysed by sequencing PCR products, amplified directly from urine samples, with oligonucleotide primers designed from the constant region of T-Antigen and VP2 coding sequences. The typical features of the NCCRs of these Indian strains appeared to be comparable and related to the archetypal strain BKV (WW) with some alterations in few key positions. Apart from these subtle alterations, neither any major DNA rearrangement within the NCCR region nor any drastic modification marked BKV strains found in nephropathy and in the healthy subjects (pregnancy). However, in some of the immunocompromised patients studied, the degree of reactivations reflected by viruria, appeared to be much higher compared to other reports.