JC polyomavirus in the aetiology and pathophysiology of glial tumours.

Glial brain tumours with their poor prognosis, limited treatment modalities and unclear detailed pathophysiology represent a significant health concern. The purpose of the current study was to investigate and describe the possible role of the human polyomavirus JC as an underlying cancerogenic or co-cancerogenic factor in the complex processes of glial tumour induction and development. Samples from 101 patients with glial tumours were obtained during neurosurgical tumour resection. Small tissue pieces were taken from several areas of the histologically verified solid tumour core. Biopsies were used for DNA extraction and subsequent amplification reactions of sequences from the JC viral genome. Real-time polymerase chain reaction was used for detection and quantification of its non-coding control region (NCCR) and gene encoding the regulatory protein Large T antigen (LT). An average of 37.6% of all patients was found to be LT positive, whereas only 6.9% tested positive for NCCR. The analysis of the results demonstrated significant variance between the determined LT prevalence and the rate for NCCR, with a low starting copy number in all positive samples and threshold cycles in the range of 36 to 42 representing viral load in the range from 10 to 1000 copies/µl. The results most probably indicate incomplete JC viral replication. Under such conditions, mutations in the host cell genome may be accumulated due to interference of the virus with the host cell machinery, and eventually malignant transformation may occur.

Prevalence of JC polyomavirus genomic sequences from the large T-antigen and non-coding control regions among Bulgarian patients with primary brain tumors.

A total of 111 fresh brain biopsies from patients with primary brain tumors were examined for JC polyomavirus sequences from the Large T antigen encoding region (LT) and the viral non-coding control region (NCCR). SYBR Green and TaqMan real-time polymerase chain reaction assays were used. In the glioblastoma group of 39 patients 48.7% were positive for LT sequences. Among the astrocytoma group (19 patients) and the oligodendroglioma group (12 patients) 31.6% and 33.3% were also positive. The prevalence of LT genomic sequences among the other groups was as follows: in 2 out of 3 oligoastrocytomas; in 3 out 5 gangliogliomas; in 2 out of 5 meduloblastomas; in 1 out 3 pineocytomas; and in none of the tested 5 ependimomas. All positive samples had a late threshold cycle that varied from 36 to 49, indicative of very low starting viral number. Only 21 of all the 111 samples were positive for NCCR. Low copy number in range of 10-1,000 was present. Notably, only 8 of all NCCR positive specimens were also LT positive. It might be suggested that the disproportion between the results for LT and NCCR is either due to clonally integrated LT fragments, with loss of genetic material, or changes in the NCCR. The latter would alter the productive course of the infection and may establish a premise for continuous interaction of viral regulatory proteins with cell molecules that are responsible for the control of the cell cycle. This may lead subsequently to malignant transformation.

Do human polyoma viruses and human immunodeficiency virus share common co-receptors?

Host and/or viral factors involved in human polyomavirus (HPoV) infection in persons living with HIV remain unknown. A hypothesis is outlined suggesting the importance of the co-receptors CCR5, CCR2, and CXCR4 not only for HIV, but also for HPoV. Functionally capable receptors coded by wild-type (wt) genotypes could facilitate internalization of HPoV in the cell resulting in brain and/or kidney infection/s in HIV infected individuals. Forty-nine Bulgarians with HIV, all treated by HAART, without neurological and/or kidney disorders, were tested for JCV and BKV and genotyped for CCR5 (CCR5del32), CCR2 (CCR2-64I), and CXCR4 (SDF1-3'A). In 27/49 (55.1%) individuals a co-infection with HPoV was identified-BKV in 12/49 (24.5%), JCV-in another 12/49 (24.5%), and both viruses-in 3/49 (6.1%). A high frequency of wt CCR5 was found in patients with HPoV (91.7% for BKV and JCV and in 100% with both viruses). V/V of CCR2 was presented in 75% for BKV and JCV and in 66.7% for BKV plus JCV. SDF1-3'G/G predominated in JCV infected patients (75%), while G/A and A/A genotypes were more frequent in patients with BKV (41.7%). Also, 21/22 (95.4%) persons without HPoV infection were heterozygous for SDF1 and CCR2. The number of individuals bearing wt of all co-receptors in the group of persons not infected with HPoV was lower (P = 0.03) than that with polymorphism/s in one or two genes (SDF1 and CCR2) in the same group. The results suggest a probable role of co-receptors used by HIV to facilitate infection with HPoV.

Sequence variations of the VP1 gene of Polyomavirus hominis 1 among Bulgarians.

Polyomavirus hominis 1 (BK virus, BKV) is an important pathogen in the field of transplantation medicine. BKV reactivation among renal-transplant recipients could cause BK associated nephropathy, which has unfavorable prognosis and is a cause for graft rejection. It is not clear why only few transplanted patients develop BK associated nephropathy while most exhibit asymptomatic viruria. One of the possible reasons lies in the mutations of the VP1 gene, encoding the main structural protein, bearing important determinants for the recognition of specific cellular receptors. The change of amino acid sequence could result in altered pathogenicity of BKV. The amplified sequences of BK in this research were from urines of patients with various clinical conditions along with healthy individuals. Nevertheless the sequence analysis which was undertaken did not show correlation between the viral genotype and the clinical condition. It was demonstrated that the most common BKV genotype in Bulgaria is genotype I and that the strains common in Bulgaria (genotypes I and IV) have typical European origin. Most of the sequenced BKV DNA samples (8/10) were correlated with the highest degree of similarity (81%) to the subcluster Ib. A specific place among the samples is taken by Pr-9, amplified from the urine of a pregnant woman that has a different evolutionary origins and might establish the beginning of a new distinct BKV strain.