Preparation of a purified, inactivated Japanese encephalitis (JE) virus vaccine in Vero cells

An attenuated Japanese encephalitis (JE) virus SA14-14-2 (PDK) was adapted to Vero cells, a continuous cell line that has been licensed for human vacc ine production, by serial passages. The resulting virus was purified by tan gential flow ultrafiltration followed by sucrose density gradient ultracent rifugation, giving 2.3 mg purified virus per liter of culture supernatant. Treatment with 0.05% formalin for 4 days at 22 degreesC completely inactiva ted viral infectivity while preserving its antigenicity. The purified, inac tivated JE virus was formulated with alum hydroxide and administered to mic e by intraperitoneal route. In terms of its ability to induce anti-JE neutr alizing antibody and to protect the immunized animal against neurovirulent virus challenge, the purified, inactivated JE virus formulated with alum wa s equivalent to the exiting commercial mouse brain-derived vaccine (JE-VAX, Aventis Pasteur Inc.).