Abstract
Kuchijirosho (snout ulcer disease) is an infectious disease of tiger puffer Takifugu rubripes in Japan and Korea. Little is known about detailed characteristics on the causative agent of kuchijirosho, except it is a filterable agent. In the present study, kuchijirosho associated proteins (KAPs) with molecular weight of 100-120 kDa were detected in brain tissues of tiger puffer by western blot analysis with sera of tiger puffer which survived kuchijirosho, but not in the kidney or spleen tissues. Interestingly, KAPs existed in brain tissues of tiger puffer with no history of kuchijirosho, however, the KAPs were not recognized by those healthy fish sera. KAPs were fractionated in supernatant of brain tissue homogenate containing the kuchijirosho agent by ultra-centrifugation, while pathogenicity of the kuchijirosho agent was observed in the precipitated fraction rather than the supernatant. These results suggest that KAPs are not structural proteins of the kuchijirosho agent, and could be brain tissue proteins antigenically altered by infection of the kuchijirosho agent. It is also considered that the causative agent could be low in antigenicity to host fish because structural proteins of the causative agent was never recognized by host fish sera.
