Isolation and characterization of an equine foamy virus

Foamy viruses (FVs) are complex retroviruses which have been isolated from different animal species including nonhuman primates, cattle, and cats. Her e, we report the isolation and characterization of a new FV isolated from b lood samples of horses. Similar to other FVs, the equine foamy virus (EFV) exhibits a highly characteristic ultrastructure and induces syncytium forma tion and subsequent cell lysis on a large number of cell lines, Molecular c loning of EFV reveals that the general organization is that of other known FVs, whereas sequence similarity with its bovine FV counterpart is only 40% . Interestingly, EFV buds exclusively from the plasma membrane and not from the endoplasmic reticulum (ER), as previously shown for other FVs. The abs ence of the ER retrieval dilysine motif in EFV Env is likely responsible fo r this unexpected sorting pathway.