TIM-family Proteins Promote Infection of Multiple Enveloped Viruses through Virion-associated Phosphatidylserine

Jemielity, Stephanie; Wang, Jinyize J.; Chan, Ying Kai; Ahmed, Asim A.; Li, Wenhui; Monahan, Sheena; Bu, Xia; Farzan, Michael; Freeman, Gordon J.; Umetsu, Dale T.; DeKruyff, Rosemarie H.; Choe, Hyeryun

However, flavivirus virions often incorporate immature glycoproteins [57] , which could lead to gaps in the glycoprotein coat through which PS becomes accessible. Our findings are consistent 293T cells were transduced with empty vector (mock) or hACE2, the receptor for SARS-CoV, followed by a second transduction with empty vector or hTIM1. These cells expressing hACE2 and/or hTIM1 were then infected with pseudoviruses carrying the GFP-reporter gene and the entry glycoprotein of the indicated SARS-CoV isolates that use hACE2 with varying efficiency [37] . Comparable titers of these pseudoviruses were confirmed by infecting cells expressing civet cat ACE2, which is efficiently used by all SARS-CoV isolates [37] . Infection levels were assessed the following day by measuring GFP expression. Shown are representative results of one of three experiments performed in duplicates. (B) 293T cells transduced with hTIM1 or hACE2 (mock) were preincubated for 20 min at room temperature with increasing concentrations of anti-hTfR1 antibody ch128.1. MACV or LASV pseudoviruses were then added for a 1 h infection at 37uC, after which cells were washed and supplemented with fresh antibody-containing medium. Infection levels were assessed the following day as in A. Figure shows mean 6 SD from two independent, duplicated experiments. doi:10.1371/journal.ppat.1003232.g006 with another recent report for a role of TIM proteins in flavivirus entry [58] . Second, as described below, the importance of PS receptors in viral entry is underscored by the fact that several viruses are known to initiate infections in PS receptor-rich cells. Finally, because the exposure of PS on virions is likely a common feature of enveloped viruses [33] , it is perhaps most surprising that the entry of a number of viruses remains unaffected by TIM1 expression.