RT Journal Article SR Electronic(1) A1 Shimizu, Akira A1 Shimizu, Nobuaki A1 Tanaka, Atsushi A1 Jinno-Oue, Atsushi A1 Roy, Bibhuti Bhusan A1 Shinagawa, Masahiko A1 Ishikawa, Osamu A1 Hoshino, HirooYR 2004 T1 Human T-cell leukaemia virus type I is highly sensitive to UV-C light JF Journal of General Virology, VO 85 IS 8 SP 2397 OP 2406 DO https://doi.org/10.1099/vir.0.19578-0 PB Microbiology Society, SN 1465-2099, AB The biological characteristics of human T-cell leukaemia virus type I (HTLV-I) are not yet well understood. UV light C (UV-C) sensitivity of HTLV-I was studied using a newly established infectivity assay: infection with cell-free HTLV-I dose-dependently induced syncytial plaques in cat cells transduced with the tax1 gene of HTLV-I. HTLV-I was inactivated by a much lower UV dose than bovine leukaemia virus (BLV). The D10 (10 % survival dose) of HTLV-I was about 20 J m−2, while that of BLV was about 180 J m−2, which was similar to the reported D10 of BLV. The UV sensitivity of HTLV-I and BLV was also examined by detecting viral DNA synthesis 24 h after infection. The D10 values determined by PCR using the gag primers for HTLV-I and BLV were close to those determined by the infectivity assays. Further PCR analyses were then performed to determine D10 values using several different primers located between the 5′-long terminal repeat (5′-LTR) and the tax1 gene. The difference in UV sensitivity between HTLV-I and BLV was detected very early during replication, even during reverse transcription of the 5′-LTR of irradiated viruses, and became more prominent as reverse transcription proceeded towards the tax1 gene. Chimeric mouse retroviruses that contain the LTR-tax1 fragments of HTLV-I and BLV were made and hardly any difference in UV sensitivity was detected between them, suggesting that the difference was not determined by the linear RNA sequences of HTLV-I and BLV. HTLV-I was found to be much more sensitive than other retroviruses to UV., UL https://www.microbiologyresearch.org/content/journal/jgv/10.1099/vir.0.19578-0