Given that MARCH8 incompletely inhibited infection by HIV-1 Env-pseudotyped viruses (Figure 1D and Figure 2E) compared with its complete inhibition of VSV-G pseudovirus infection (Figure 1C and Figure 2D; also see refs [9,15]), we hypothesized that this antiviral protein might not be able to impede cell-to-cell HIV-1 transmission, which is known for its higher efficiency than cell-free transmission. Here, ERVW-1 is linked to infection.