@article{mbs:/content/journal/jgv/10.1099/vir.0.037622-0, author = "Shinagawa, Masahiko and Jinno-Oue, Atsushi and Shimizu, Nobuaki and Roy, Bibhuti Bhusan and Shimizu, Akira and Hoque, Sk. Ariful and Hoshino, Hiroo", title = "Human T-cell leukemia viruses are highly unstable over a wide range of temperatures", journal= "Journal of General Virology", year = "2012", volume = "93", number = "3", pages = "608-617", doi = "https://doi.org/10.1099/vir.0.037622-0", url = "https://www.microbiologyresearch.org/content/journal/jgv/10.1099/vir.0.037622-0", publisher = "Microbiology Society", issn = "1465-2099", type = "Journal Article", abstract = "The biological properties of human T-cell leukemia virus type I (HTLV-I) and HTLV type II (HTLV-II) are not well elucidated as cell-free viruses. We established new assay systems to detect the infectivity of cell-free HTLVs and examined the stability of cell-free HTLVs at different temperatures. HTLVs lost infectivity more rapidly than did bovine leukemia virus (BLV), which is genetically related to HTLVs. The half-lives of three HTLV-I strains (two cosmopolitan strains and one Melanesian strain) at 37 °C were approximately 0.6 h, whereas the half-life of a BLV strain was 8.5 h. HTLV-I rapidly lost infectivity unexpectedly at 0 and 4 °C. We examined the stability of vesicular stomatitis virus pseudotypes with HTLV-I, HTLV-II or BLV Env proteins, and the Env proteins of HTLVs were found to be more unstable at 4 and 25 °C than the Env proteins of the BLV. Over the course of the viral life cycle, heat treatment inhibited HTLV-I infection at the phase of attachment to the host cells, and inhibition was more marked upon entry into the cells. The HTLV-I Env surface (SU) protein (gp46) was easily released from virions during incubation at 37 °C. However, this release was inhibited by pre-treatment of the virions with N-ethylmaleimide, suggesting that the inter-subunit bond between gp46 SU and gp21 transmembrane (TM) proteins is rearranged by disulfide bond isomerization. HTLVs are highly unstable over a wide range of temperatures because the disulfide bonds between the SU and TM proteins are labile.", }