Molecular characterization of JC virus in progressive multifocal leukoencephalopathy cases from India.

Progressive Multifocal Leukoencephalopathy (PML) is a rare, often fatal demyelinating disease of the central nervous system caused by reactivation of the John Cunningham virus (JCV) in immunocompromised individuals. Despite an estimated 2.4 million people living with HIV in India, the reported incidence of PML remains lower than in Western countries, likely due to underdiagnosis, underreporting, and distinct host genetic and viral factors. The rising number of individuals on immunosuppressive therapies, including organ transplant recipients and those with autoimmune disorders, further emphasizes the need to study JC virus diversity in the Indian context. This study aimed to characterize the genetic diversity of JCV in India by sequencing the VP1 and non-coding control region (NCCR) from cerebrospinal fluid (n=30) of confirmed PML cases using Sanger sequencing. VP1 sequencing (n=23) revealed a predominance of genotypes 2 (subtypes 2D, 2A, 2B) and 3A. NCCR analysis (n=17) showed extensive rearrangements relative to the archetype form, with most sequences classified as Type II-R. Structural variations, including deletions, duplications, and insertions were common, particularly in blocks D, C, and F. Transcription factor binding sites (TFBS) were identified for TATA box, Tst-1, SP-1, p53, CEBPB, AP-1, NF-1, EGR-1, GF-1, CRE-TAR and NFkB. Additional TFBS were created due to rearrangements, often spanning two blocks. These findings underscore the genomic diversity of JCV in India and highlight the need for continued molecular surveillance to better understand its implications for high-risk populations.