Human T-cell leukemia viruses are highly unstable over a wide range of temperatures

• Published in: Journal of general virology 2012-03, Vol.93 (Pt 3), p.608-617
• Main Authors: SHINAGAWA, Masahiko, JINNO-OUE, Atsushi, SHIMIZU, Nobuaki, ROY, Bibhuti Bhusan, SHIMIZU, Akira, ARIFUL HOQUE, Sk, HOSHINO, Hiroo
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Carcinogenesis, carcinogens and anticarcinogens; Disulfides - chemistry; Fundamental and applied biological sciences. Psychology; Human T-lymphotropic virus 1 - pathogenicity; Human T-lymphotropic virus 1 - radiation effects; Human T-lymphotropic virus 2 - pathogenicity; Human T-lymphotropic virus 2 - radiation effects; Humans; Leukemia Virus, Bovine - pathogenicity; Leukemia Virus, Bovine - radiation effects; Medical sciences; Microbial Viability - radiation effects; Microbiology; Miscellaneous; Protein Stability; Protein Subunits - chemistry; Temperature; Time Factors; Tumors; Viral Envelope Proteins - chemistry; Virology; Viruses
• ISSN: 0022-1317; 1465-2099
• DOI: 10.1099/vir.0.037622-0

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.