Background:  Although HAART may maintain or restore cellular immunity, progressive multifocal leukoencephalopathy (PML) remains a serious cause of neurologic morbidity among AIDS patients, with 50% fatality rate. PML may arise amidst the setting of immune reconstitution inflammatory syndrome (IRIS). In these patients T cell infiltrates are found in the PML lesions in the brain. It remains unknown if these cells can modulate JCV replication. We therefore hypothesized that the soluble factors released by activated T cells (ATC) can modulate John Cunningham virus (JCV) replication in primary human fetal glial (PHFG) cells and can also alter the cytokine profile of these cells.

Methods:  PHFG cells were infected with 20 hemagglutination units (20 x 10⁶ copies) of JCV and cultivated in the continuous presence of supernatant from healthy T cells either activated with anti-CD3/CD28 (ATCS) or un-activated (UATCS) or control T cell medium (CTCM). Cytotoxicity assay was conducted on ATCS, UATCS, and CTCM to determine the optimal non-toxic dose, and based on this data 8-fold dilution of ATCS, UATCS, and CTCM were employed for all experiments. Supernatant and cells were harvested at various time points to assess for inhibition of JCV by measuring JCV T antigen and viral protein-1 DNA and mRNA transcripts, by quantitative real-time polymerase chain reaction (qRT-PCR) and  RT-PCR, and for measuring secretion of key cytokines in the supernatant by using a microsphere-bead assay. 

Results:  JCV replication was significantly inhibited starting day 1 and continued until the end of the experiment, day 15, in the presence of ATCS. Moreover, in the presence of ATCS, a swarm of cytokines and chemokines were secreted of which, interleukin (IL) -6, IL-8, and tumor necrosis factor-alpha (TNF-a) levels were significantly high. Interestingly, IL-6 was not detected in the CTCM but was 10- to 100-fold increased over a 15-day period in JCV-infected PHFG cells cultivated with ACTS compared to JCV-infected PHFG cells cultivated with UATCS or CTCM. Furthermore, IL-6 up-regulation was correlated with significant inhibition of JCV replication.

Conclusions:  Our data demonstrate direct antiviral effect of 1 or more component present in the ACTS on JCV replication, and that the soluble factors released by ATC also trigger JCV-infected PHFG cells to produce IL-6. The role of IL-6 in JCV replication needs to be determined. However, these data suggest that ATC in the PML lesion may have a protective effect against JCV replication.