Department of Neurovirology, National Institute of Mental Health and Neurosciences, Bangalore, India.
Abstracts of the papers presented at the International Conference of Indian Virological Society on “Emerging and Re-emerging viral Diseases of the Tropics and Subtropics” at Indian Agricultural Research Institute, New Delhi, India, December 11–14, 2007.
Japanese encephalitis (JE) is a leading cause of viral encephalitis in Asia with sporadic and epidemic cases reported annually. Despite their emergence no specific therapy is available. Hence, identification of compounds that inhibit flavivirus replication is critical. Earlier investigations have shown that infection due to Japanese encephalitis virus (JEV) generates rapid inflammatory response and the mortality rate increases with increasing concentrations of TNF-a in serum and CSF. Studies have shown that pentoxiphyllin is a known TNF-a inhibitor, immunomodulator and possess antiviral property. A compound that can interfere with viral replication and concomitantly overcome the infection by modulating the immune system is one of the strategies that can be used to treat viral infections. Therefore, the present study investigated the effects of pentoxiphyllin in infections caused by JEV. The antiviral effect of pentoxiphyllin against JEV was determined by in vitro assays carried out on cell culture models using Porcine Stable kidney (PS) cells. Initially, cytotoxicity was ascertained using trypan blue exclusion assay and proliferation tests to arrive at CC50. The antiviral activity of pentoxiphyllin was then evaluated by an in vitro CPE inhibition screening assay using three experimental conditions namely, pre-incubation assay, co-incubation assay and post- infection assay. This was essentially to classify the compound as entry inhibitor, virucidal agent or inhibitor of viral replication respectively. The extent of antiviral activity was confirmed by plaque reduction assay. Further, the mechanism of antiviral action of pentoxiphyllin was evaluated using a series of in vitro experiments. Therapeutic potential of pentoxiphyllin was then studied in vivo using mouse model. In vitro antiviral evaluation suggested that pentoxiphyllin inhibited JEV replication post-entry into host cell. Studies on the mechanism of action of pentoxiphyllin suggested that it inhibited the replication of JEV by interfering with the late stages of virus replication. Further, it was observed that, 200 mg/Kg body weight pentoxiphyllin completely protected mice from infection by JEV.
