Quantification of human polyomavirus JC virus load in urine and blood samples of healthy tribal populations of North-Eastern part of West Bengal, India

Human BK and JC polyomaviruses: Molecular insights and prevalence in Asia

Polyomaviridae family consists of small circular dsDNA viruses. Out of the 14 human polyomaviruses described so far, BKPyV and JCPyV have been studied extensively since their discovery in 1971. Reportedly, both BKPyV and JCPyV are widely distributed across the globe with the frequency of 80-90 % in different populations. The primary infection of these viruses is usually asymptomatic and latent which is activated as a consequence of immunosuppression. Activated BKPyV and JCPyV viruses lead to the development of BK Virus Associated Nephropathy and Progressive Multifocal Leukoencephalopathy, respectively. Immense progress has been made during the last few decades regarding the molecular understanding of polyomaviruses. Epidemiology of polyomaviruses has also been studied extensively. However, most of the epidemiological studies have focused on European and American populations. Therefore, limited data is available regarding the geographical distribution of these potentially oncogenic viruses in Asian countries. In this article, we have presented a compendium of latest advances in the molecular understanding of polyomaviruses and their pathobiology. We also present a comprehensive review of published literature regarding the epidemiology and prevalence of BKPyV and JCPyV in Asian regions. For this purpose, a thorough search of available online resources was performed. As a result, we retrieved 24 studies for BKPyV and 22 studies for JCPyV, that describe their prevalence in Asia. These studies unanimously report high occurrence of both BKPyV and JCPyV in Asian populations. The available data from these studies was categorized into two groups: on the basis of prevalence (low, medium and high) and disease development (healthy and diseased). Altogether, Korean population hasbeen evidenced to possess highest frequency of BKPyV (66.7 %), while JCPyV was found to be most prevalent in Taiwan (88 %). Due to high and ubiquitous distribution of these viruses, frequent studies are required to develop a better understanding regarding the epidemiology and pathobiology of these viruses in Asia.

Viral tumor antigen expression is no longer required in radiation-resistant subpopulation of JCV induced mouse medulloblastoma cells

The human neurotropic polyomavirus JC, JC virus (JCV), infects the majority of human population during early childhood and establishes a latent/persistent infection for the rest of the life. JCV is the etiologic agent of the fatal demyelinating disease of the central nervous system, progressive multifocal leukoencephalopathy (PML) that is seen primarily in immunocompromised individuals. In addition to the PML, JCV has also been shown to transform cells in culture systems and cause a variety of tumors in experimental animals. Moreover, JCV genomic DNA and tumor antigen expression have been shown in a variety of human tumors with CNS origin. Similar to all polyomaviruses, JCV encodes for several tumor antigens from a single transcript of early coding region via alternative splicing. There is little known regarding the characteristics of JCV induced tumors and impact of DNA damage induced by radiation on viral tumor antigen expression and growth of these cells. Here we analyzed the possible impact of ionizing radiation on transformed phenotype and tumor antigen expression by utilizing a mouse medulloblastoma cell line (BSB8) obtained from a mouse transgenic for JCV tumor antigens. Our results suggest that a small subset of BSB8 cells survives and shows radiation resistance. Further analysis of the transformed phenotype of radiation resistant BSB8 cells (BSB8-RR) have revealed that they are capable of forming significantly higher numbers and sizes of colonies under anchorage dependent and independent conditions with reduced viral tumor antigen expression. Moreover, BSB8-RR cells show an increased rate of double-strand DNA break repair by homologous recombination (HR). More interestingly, knockout studies of JCV tumor antigens by utilizing CRISPR/Cas9 gene editing reveal that unlike parental BSB8 cells, BSB8-RR cells are no longer required the expression of viral tumor antigens in order to maintain transformed phenotype.

Specific and quantitative detection of Human polyomaviruses BKPyV and JCPyV in the healthy Pakistani population

BACKGROUND

The BK Polyomavirus (BKPyV) and JC polyomavirus (JCPyV) infections are widespread in human population and have been associated with severe kidney and brain disorders, respectively. The viruses remain latent primarily in reno-urinary tract, reactivating only in case of a compromised immune system. The seroepidemiology and molecular prevalence of BKPyV and JCPyV have been widely studied both in healthy and immunocompromised patients worldwide. However, data regarding the prevalence of these viruses in the immunocompetent or apparently healthy Pakistani population is lacking. Herein, we present the first ever report on quantitative prevalence of BKPyV and JCPyV in the peripheral blood of a randomly selected cohort of healthy Pakistani population.

METHODS

A total of 266 whole blood samples were examined. The subjects were divided into three age groups: ≤ 25 years (young), 26-50 years (middle) and ≥ 51 years (elder). Absolute real time PCR assay was designed to quantify the BKPyV and JCPyV viral copy numbers in the range of 106 to 100 copies/mL.

RESULTS

Overall, BKPyV was detected in 27.1% (72/266) individuals while JCPyV in 11.6% (31/266) indicating significant difference (p < 0.005) in the distribution of these two viruses. The prevalence of BKPyV significantly decreased from 51% (49/96) in young age group to 8.2% (7/85) in eldest age group. Whereas, JCPyV positivity rate slightly increased from 8.3% (8/96) in young age group to 11.8% (10/85) in elder age group. The median viral load was calculated as 6.2 log and 3.38 log copies/mL of blood for BKPyV and JCPyV, respectively. Notably, no significant difference in viral load of either of the subtypes was found between different age groups.

CONCLUSION

The current study provides an important baseline data on the prevalence and viral load of circulating BKPyV and JCPyV in Pakistani population. The prevalence and viral load of BKPyV was comparatively higher than JCPyV. The prevalence of BKPyV significantly decreased with increase in age while JCPyV positivity rate slightly increased with increasing age. Viral load of both BKPyV and JCPyV was not correlated with the individual ages.