Characterization of tick-borne encephalitis virus and immunogenicity of its surface components in mice

Tick-borne encephalitis (TBE) virus grown in chick embryo cells and purified by rate-zonal centrifugation was shown to have a density of 1.195 g/cm3 in sucrose density gradients. Under the conditions used, CsCl centrifugation caused disruption of the virus and less than 5% of input infectivity could be recovered from the virus peak at 1.23 g/cm3. As in other fiaviviruses, three polypeptides (V1, V2, V3) were detected by polyacrylamide gel electrophoresis in radioactively labelled purified TBE virus. After disruption of TBE virus with Nonidet P-40, Tween-80/Tri-(n-butyl)-phosphate or sodium deoxycholate, a 120--130 S nucleoprotein could be separated by rate zonal centrifugation from more slowly sedimenting haemagglutinins. Immunization of mice with these haemagglutinins showed that they induced haemagglutination inhibiting, neutralizing and complement fixing antibodies. A pronounced increase in immunogenicity could be observed by the use of Al(OH3) as an adjuvant.