TIM-1 promotes infection with mosquito cell-derived alphaviruses through virion-associated phospholipids.

Human T-cell immunoglobulin and mucin domain 1 (TIM-1) facilitates infection of re-emerging viruses, including alphaviruses, through its phosphatidylserine (PS) binding domain. Although alphaviruses are transmitted to humans via mosquito bite, it is unclear whether mosquito-derived viruses also use TIM-1 to infect human cells. Since viruses acquire their PS-containing envelope from the host cell and insect cell membranes differ in lipid composition from mammalian membranes, we here investigate the role of TIM-1 at the mosquito-mammalian interface. We show that TIM-1 promotes infection with mosquito cell-derived, replication-competent alphaviruses, including Chikungunya virus, O'nyong'nyong virus (ONNV), and Sindbis virus. The TIM-1 PS-binding domain is essential for enhancing mosquito cell-derived ONNV infection as shown by TIM-1 mutagenesis. According to untargeted lipidomics, mosquito cell-derived ONNV virions contain higher levels of phosphatidylethanolamine (PE) and PS compared to mammalian cell-derived ONNV. Notably, TIM-1 engages PE as well as PS, as demonstrated by liposome competition. PS decarboxylase experiments suggest that PS is an important mediator of mosquito-cell derived ONNV entry into mammalian cells. Taken together, our data show that TIM-1 promotes mosquito cell-derived alphavirus infection of mammalian cells. This work provides implications for the understanding of the TIM-1 ligand repertoire and advances our understanding of arbovirus transmission at the mosquito-mammalian interface.