Entry, infection, replication, and egress of human polyomaviruses: an update.

Polyomaviruses (PyVs), belonging to the family Polyomaviridae, are a group of small, nonenveloped, double-stranded, circular DNA viruses widely distributed in the vertebrates. PyVs cause no apparent disease in adult laboratory mice but cause a wide variety of tumors when artificially inoculated into neonates or semipermissive animals. A few human PyVs, such as BK, JC, and Merkel cell PyVs, have been unequivocally linked to pathogenesis under conditions of immunosuppression. Infection is thought to occur early in life and persists for the lifespan of the host. Over evolutionary time scales, it appears that PyVs have slowly co-evolved with specific host animal lineages. Host cell surface glycoproteins and glycolipids seem to play a decisive role in the entry stage of viral infection and in channeling the virions to specific intracellular membrane-bound compartments and ultimately to the nucleus, where the genomes are replicated and packaged for release. Therefore the transport of the infecting virion or viral genome to this site of multiplication is an essential process in productive viral infection as well as in latent infection and transformation. This review summarizes the major findings related to the characterization of the nature of the interactions between PyV and host protein and their impact in host cell invasion.

Molecular analysis of JC polyomavirus genotypes circulating among tribal populations of North-Eastern West Bengal, India.

There is a resurgence of interest in the study of occurrence, genotype and pathogenic associations of human Polyomaviruses in recent years. In the present study, we have ascertained the presence of human Polyomavirus JC (JCV) in the urine and peripheral blood leukocytes of tribal populations, for the first time in the North-Eastern part of West Bengal State of India. We have also characterized the prevalent genotypes of the non-coding controlregions (NCCRs) of these natural isolates. The result suggests a high incidence of JCV reactivation in the populations assayed. Approximately 25% of the non-immunocompromized tribal men and women, tested positive based on polymerase chain reaction (PCR) analysis, and these results were further confirmed by sequencing of PCR products. Pairwise sequence comparison and alignment of the NCCR sequence of these Indian strains appeared to be comparable and related to the archetypal JCV (CY) and the Tibetan LH3 strains, with some alterations in few key positions. The sequence analyses were done with regard to transcription factor binding to DNA sequence elements of endemic JCV NCCRs.