Forty-Five Years of Marburg Virus Research

Brauburger, Kristina; Hume, Adam J.; Mühlberger, Elke; Olejnik, Judith

Besides its function in entry and budding, GP may also play a role in immune evasion. The IFN-inducible antiviral protein tetherin was shown to block the release of VP40-induced virus-like MARV and EBOV particles, suggesting that tetherin might act as a restriction factor for filovirus release [102, 103] . However, co-expression of GP was sufficient to counteract the antiviral activity of tetherin by a yet unknown mechanism [104, 105] . It is possible that GP not only subverts innate immune responses but also suppresses the adaptive immune response. Filoviral GP 2 subunits, including MARV GP 2 , contain a domain resembling an immunosuppressive motif found in retroviral envelope proteins [106] . A 17-mer peptide corresponding to the putative immunosuppressive domain of MARV GP was shown to induce lymphocyte death and suppression of cytokine responses [107] . It is not yet known if this motif plays a role in the induction of lymphocyte apoptosis observed in MARV infection. Finally, it has been suggested that shedding of the ectodomain of membrane-bound EBOV GP by tumor necrosis factor α-converting enzyme (TACE) may play a role in blocking the activity of neutralizing antibodies during infection [108] . It has been reported for MARV that considerable amounts of GP shed from infected cells, although it is not clear if MARV GP is a target for TACE cleavage [108, 109] .