Retroviral membrane display of apoptotic effector molecules

Retroviruses have been widely used in gene transmission studies. In this paper, we show that nonviral apoptotic proteins can be displayed on viral membrane surfaces and that the displayed proteins can execute their normal effector functions. We introduced the genes encoding the apoptosis effector proteins, human CD95 ligand (hFasL) or human tumor necrosis factor-related apoptosis-inducing ligand (hTRAIL), into a cell line that packages Moloney murine leukemia virus vectors. Retrovirus preparations from these lines killed target cells efficiently, and target killing was prevented by Fas-Ig fusion protein or soluble TRAIL receptor (sDR5), respectively. We show that the virus preparation exhibiting Fas-specific cytotoxicity has the same density as a retrovirus, contains full-length FasL protein, and can be depleted of infectivity by immunoadsorption with anti-FasL antibody. This novel property of retroviruses-the display of functional effector proteins-may allow the custom design of reagents whose normal function requires their being embedded in a membrane.