TITRATION AND EXTENSIVE SERIAL PASSAGES OF YABA VIRUS IN VITRO

A sensitive assay system of Yaba virus (YV) was established in a cynomolgus monkey kidney cell line, JINET, in which the virus caused multilayered cellular foci countable even with the unaided eye. The specificity of the foci induced by YV in these cells was demonstrated by (1) the focus‐forming ability was destroyed by heating at 60 C for 12 min; (2) the focus formation was inhibited by specific antiserum; (3) specific fluorescence was detected only in cells composing the foci when tested by fluorescent antibody technique; (4) a linear relationship was observed between the virus concentration and the number of foci formed; (5) YV preparation passed 20 times in JINET cells still possessed “tumorigenicity” in cynomolgus monkeys. The sensitivity of JINET cells to YV was comparable to that of cynomolgus monkeys, and YV was successively propagated in JINET cells with 2 log increase in infectivity titer during over 40 serial passages. Application of this assay system to growth kinetic studies of YV and quantitation of neutralizing antibody to YV is also discussed. © jointly owned by Japanese society for Bacteriology and Society of Japanese Virologists