The EXXXLV motif is essential to counteract tetherin-mediated restriction of cell-free HIV-1 particle release from CD4+ T cells treated with type-1 interferon.

Jurkat cells were infected with the indicated HIV-1 mutant at an MOI of 1. 16 h later the cells were treated or not with 5000 U/ml universal type-I interferon. Cell lysates and viral supernatants were harvested a further 24 h later and analyzed for infectivity on HeLa-TZM (A) or physical particle yield and cellular viral and tetherin expression by quantitative Western blotting (B). (C) A representative example of primary human CD4+ T cells treated as in (B) and the MFI of surface tetherin levels on these cells with or without 24 h type-I interferon treatment as analyzed by flow cytometry (D). (E) Human CD4+ T cells were infected with the indicated virus. 48 h later cells were stained for surface tetherin and intracellular p24CA and analyzed by flow cytometry.