Reducing cytotoxicity induced by sindbis viral vectors

Sindbis virus has been recognized as a potentially useful virus vector for gene therapy. In an effort to improve its utility and provide cell-targetin g capability to gene therapy vectors, we recently developed Sindbis virus v ectors possessing chimeric envelopes with cell-specific targeting ability [ K. Ohno et al. Nature Biotechnol 15:763-767, 1997; K. Sawai et al. Biochem Biophys Res Commun 248:315-323, 1998]. However, a residual problem associat ed with Sindbis virus vectors is the apoptotic effect of this virus on infe cted cells. To address this issue, we have studied the possible role of bcl -2 expression. Bcl-2 expression has been postulated to facilitate the estab lishment of persistent Sindbis viral infection by blocking virus-induced ap optosis. In this study we produced a Sindbis virus vector capable of expres sing human bcl-2 and the reporter gene, lacZ. This chimeric virus (SinRep/l acZ/bcl-2/DH-BB) showed a marked reduction in induced apoptosis in infected cells. For example, after infection with this vector, cell proliferation o f BHK cells was 55% of that of uninfected cells 2 days after infection and 40% 3 days after infection. While this reflected a significant degree of ap optosis, the effect was much less pronounced than that seen with wild-type Sindbis virus. Cell proliferation was reduced to 26% 2 days after wild-type virus infection of BHK cells and to only 7% 3 days after infection. Althou gh additional work will be required to eliminate apoptosis induced by Sindb is virus vectors, the studies reported here suggest that such a goal may be achievable after additional modification of the vectors. (C) 1999 Academic Press.