{Reference Type}: Journal Article {Title}: Detailed analysis of low temperature inactivation of respiratory syncytial virus. {Author}: Kitai Y;Watanabe O;Ohmiya S;Kisu T;Ota R;Kawakami K;Katoh H;Fukuzawa K;Takeda M;Nishimura H; {Journal}: Sci Rep {Volume}: 14 {Issue}: 1 {Year}: 2024 05 23 {Factor}: 4.996 {DOI}: 10.1038/s41598-024-62658-z {Abstract}: Our previous findings indicated that many respiratory syncytial virus (RSV) isolates are unstable at 4 °C compared to 20 °C. Some of the strains completely lose infectivity after 24 h at 4 °C. This study analyzed the inactivation process at 4 °C using a representative strain, RSV/Sendai/851/13. After 24 h of storage at 4 °C, the virus was completely inactivated but retained its ability to attach to and to be taken into host cells. It suggested a reduced fusion ability between the viral and cellular membranes. During storage at 4 °C, the RSV fusion (F) protein underwent a conformational change and was no longer recognized by pre-fusion form-specific antibodies. When the RSV/Sendai/851/13 strain was passaged at 4 °C, a variant with an amino acid substitution, I148T, in the F protein fusion peptide was selected. Also, an amino acid change in G protein demonstrating stability at low temperatures was obtained. These results show that the inactivation of RSV at 4 °C is due to the loss of membrane fusion activity in the F protein, which cannot maintain its pre-fusion state at 4 °C.