Multiplication of bovine viruses in hamster lung HmLu-1 cells cultured in protein-free medium.

Technology for virus multiplication has been greatly advanced since the establishments of the chick embryo culture method^ and tissue culture method.2) These methods have contributed to progress in virology and vaccine preparation. Many vaccines for virus diseases of human and domestic animals have been developed after Salk's success in preparing poliovaccine using primary culture of monkey kidney cells.3) Host cells need, however, serum components for their growth. The requisite of the serumused in host cell culture is that it is free from antibodies against the virus. In general, serum used in cell culture is derived from cattle. Therefore, in the case of multiplication of viruses that cause bovine diseases, it is necessary to avoid the use of serum derived from cattle infected with the viruses or injected with vaccines to the viruses. In addition, whenvaccination to different types of animals is repeated, serum components induce needless antigen-antibody reactions in a harmful way. The vaccines madefrom protein-free mediumdo not have any of these disadvantages. Wereported that hamster lung (HmLu-1) cells could not only grow but also support multiplication ofAkabane virus in a protein-free DF (PF-DF) medium,40 as well as in DF medium supplemented with 10% new born calf serum.5) When HmLu-1 cells are used as a host cell line, the problems that are attributable in serum as above may not be encountered. This paper deals with the multiplication of viruses that cause bovine diseases using HmLu-1 cells cultured in the PF-DF medium. Four virus strains, Akabane virus OBE-1,6) bovine ephemeral fever virus (BEFV) YHL, Ibaraki virus No. 2,7) and Chuzan virus K-478) and a host cell line, HmLu-1 cells, were obtained from the National Institute of Animal Health, Ministry of Agriculture, Forestry, and Fisheries of Japan. HmLu-1 cells were cultured in the PF-DF