Sequencing of the red sea bream iridovirus (RSIV) genome and the identification of genes which may encode prospective protective antigens

J. Kurita and K. Nakajima (Fish Pathology Div)

   The entire genome of the red sea bream iridovirus (RSIV) was sequenced. The RSIV causes the red sea bream iridoviral disease (RSIVD), as important disease affecting cultured marine fish species. In addition, we searched for genes that possibly encode protective antigens, which would be essential for the production of a subunit vaccine.

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［Objective］

  RSIV is the causative agent of RSIVD, which leads to mass mortalities and huge economical losses, not only in cultured red sea bream but also in other cultured marine fish species. A vaccination against RSIVD using a formaline-killed vaccine has been used for the control of the disease. However, production of the inactivated type of viral vaccine entails high production costs since expensive materials for cell culture to replicate the virus are required. Subunit vaccine development using recombinant DNA technology is a promising alternative to produce a cheap vaccine against RSIVD. To develop such a vaccine, identification of the protective antigens and isolation of genes, which encode them, are essential. These have not been achieved in the case of RSIV. Hence, we aimed to sequence the entire genomic DNA of RSIV to identify all the genes which many encode possible protective antigens of RSIV.

［Results］

  We succeeded in sequencing the 112, 414bp genomic DNA of RSIV by gene analysis and to search for genes which encode potential protective antigens (Figs 1 and 2). There were only 2 reports regarding the full genome sequences of large genome sized DNA viruses which cause fish disease. This study is the first to be undertaken in Japan. From result of the gene analysis, we have evidence to suggest that RSIV belongs to a new genus in the family Iridoviridae. Moreover, we succeeded to identify the genes which encode prospective cell attachment proteins, which could be evaluated as prospective cell attachment proteins, which could be evaluated as protective antigens among the genes of possible membrane proteins. Development of a cheap subunit vaccine or effective DNA vaccine using identified viral genes should be undertaken.

　

［Publications］

1) Kurita, J., Nakajima, K., Hirono, I., and Aoki, T. (2000) Decision of complete genome DNA sequence of red sea bream iridovirus genome. Abstract of 2000 spring meeting of Japanese Society of Fish Pathology, p.7 (In Japanese).
2) Kurita, J. (2000) Gene analysis of red sea bream iridovirus. Yoshoku, 37(6), p.118-121 (In Japanese).

［Patent Applications］

1) Kurita, J. and Nakajima, K. : Red sea bream iridoviral DNAs that encode proteins in relation to viral neutralization or protectivity (Application code: 2000-294991, Japan).

　

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