Kaszuba, T. | bioRxiv Science

bioRxiv2026

CD164 is an endolysosomal host factor for entry of Clade A New World Arenaviruses

Arenaviruses are divided into Old World (OW) and New World (NW) groups. OW arenaviruses enter cells through a pH-dependent receptor switch from a plasma-membrane factor to an endolysosomal receptor for subsequent membrane fusion, whereas clade B NW arenaviruses use transferrin receptor 1 without a secondary receptor. Using a vesicular stomatitis virus (VSV) chimera expressing the glycoprotein complex (GPC) of the clade A NW arenavirus Pichinde virus, we performed a genome-wide CRISPR loss-of-function screen and identified the endolysosomal sialomucin CD164 as an essential host factor. CD164 knockout cells were resistant to VSV chimeras bearing the GPCs of Pichinde, Parana, and Flexal viruses, and to authentic Pichinde and Parana virus, with susceptibility restored by complementation. The requirement mapped to the cysteine-rich domain of CD164, which bound GP1 in a pH-dependent manner through main-chain interactions. These findings define CD164 as an endolysosomal receptor for clade A NW arenaviruses expanding the receptor switching paradigm.

microbiology↗

bioRxiv2025

Determinants of human versus mosquito cell entry by the Chikungunya virus envelope proteins

Chikungunya virus (CHIKV) infects both humans and mosquitoes during its transmission cycle. How the viruss envelope proteins mediate entry in cells from such different species is unclear. MXRA8 is a receptor for CHIKV in mammalian cells, but the receptor(s) in mosquito cells remains unknown. Here we use pseudovirus deep mutational scanning to measure how nearly all amino-acid mutations to the CHIKV envelope proteins affect entry in MXRA8-expressing human and mosquito cells. Most mutations similarly affect entry in both types of cells, and our comprehensive measurements of these effects define functional constraints related to protein folding and fusion activity. However, some mutations differentially affect entry in MXRA8-expressing human cells versus mosquito cells. Sites where mutations specifically impair entry in MXRA8-expressing human cells are often involved in MXRA8 binding, and we hypothesize sites where mutations specifically impair entry in mosquito cells are involved in binding the unknown mosquito receptor(s). We use the deep mutational scanning data to design loss-of-tropism mutant viruses that are impaired in their ability to infect either mosquito cells or MXRA8-expressing human cells. Our findings provide insights into the species-specific determinants of CHIKV cell entry that can help guide receptor identification and vaccine development.

microbiology↗