Tripartite motif-containing protein 5α (TRIM5α) functions as a cellular antiviral restriction factor with exquisite specificity towards the capsid lattices of retroviruses. The relative avidity of TRIM5α binding to retrovirus capsids directly impacts primate species susceptibility to infection, but the antiviral role of TRIM5α is thought limited to retroviruses. In contrast to this current understanding, here we show that both human and rhesus TRIM5α possess potent antiviral function against specific flaviviruses through interaction with the viral protease (NS2B/3) to inhibit virus replication. Importantly, TRIM5α was essential for the antiviral function of IFN-I against sensitive flaviviruses in human cells. However, TRIM5α was ineffective against mosquito-borne flaviviruses (yellow fever, dengue, and Zika viruses) that establish transmission cycles in humans following emergence from non-human primates. Thus, TRIM5α is revealed to possess remarkable plasticity in recognition of diverse virus families, with potential to influence human susceptibility to emerging flaviviruses of global concern.

TRIM5α restricts flavivirus replication by targeting the viral protease for proteasomal degradation.