Isolation of Koala Retroviruses from Koalas in Japan
Takayuki MIYAZAWA1,2)*,†, Takayuki SHOJIMA1,2)†, Rokusuke YOSHIKAWA1,2,3) and Takuji OHATA1,2,3)
1)Laboratory of Signal Transduction, Department of Cell Biology,
2)Laboratory of Viral Pathogenesis, Center for Emerging Virus Research, Institute for Virus Research, Kyoto University, 53 Shogoin-Kawaracho, Sakyo-ku, Kyoto 606–8507,
3)Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsucho, Sakyo-ku, Kyoto 606–8501
4)Kobe Municipal Oji Zoo, 3–1 Oji-cho, Nada-ku, Kobe, Hyogo 657–0838, Japan
* CORRESPONDENCE TO: MIYAZAWA, T., Laboratory of Signal Transduction, Department of Cell Biology, Institute for Virus Research, Kyoto University, 53 Shogoin-Kawaracho, Sakyo-ku, Kyoto 606–8507, Japan. e-mail:
† These authors contributed equally to this work.
Koala retrovirus (KoRV) is considered to be associated with leukemia, lymphoma and immunodeficiency-like diseases in koalas. We therefore conducted a pilot study of KoRV infection in five Queensland koalas in Kobe Municipal Oji Zoo. By polymerase chain reaction to detect partial env and pol genes of KoRV in genomic DNA isolated from whole blood and feces, all five koalas were found to be positive for KoRV proviruses. We succeeded in culturing koala lymphocytes from less than 1 ml blood for over 14 days in the presence of recombinant human interleukin-2. By coculturing the lymphocytes with human embryonic kidney (HEK) 293T cells, we isolated KoRVs from all five koalas. We designated these isolates as strains OJ-1 to OJ-5. By electron microscopy, we observed C-type retroviral particles in HEK 293T cells chronically infected with KoRV strain OJ-4. This is the first report on the isolation of KoRV from koalas in a Japanese zoo.