Chikungunya virus uses the tetraspanins CD63, CD9, and CD151 to replicate in human synovial fibroblasts.

The arthritogenic alphavirus chikungunya virus (CHIKV) causes debilitating long-lasting joint pain. Host factors used by CHIKV to infect joint cells are largely unknown. Here, we evaluated the role of the 19 tetraspanins expressed in primary human synovial fibroblasts in virus infection. The exosome-associated tetraspanins CD63, CD9, and CD151 supported CHIKV infection of joint fibroblasts. Silencing of CD63 and CD151 reduced subgenomic replicon activity. CD9 localized in close proximity to replication sites and its silencing reduced intracellular CHIKV genome accumulation. Silencing of all three tetraspanins reduced progeny virus production. While these tetraspanins were dispensable for CHIKV entry into joint fibroblasts, the receptor MXRA8 promoted cell entry. Our findings demonstrate that CHIKV exploits tetraspanins as host factors in synovial fibroblasts, shedding light on molecular mechanisms underlying CHIKV pathogenesis in joint tissues.