CELL-SPECIFIC TARGETING OF A THYMIDINE KINASE GANCICLOVIR GENE-THERAPY SYSTEM USING A RECOMBINANT SINDBIS VIRUS VECTOR/

Transfer of the herpes simplex virus type I thymidine kinase (HSV-TK) gene into tumor cells using virus-based vectors in conjunction with ga nciclovir (GCV) exposure provides a potential gene therapy strategy fo r the treatment of cancer. The possibility of using a novel targetable Sindbis virus expression vector containing the HSV-TK gene was examin ed, Baby hamster kidney (BHK) cells and several human tumor cells infe cted with a Sindbis virus containing the HSV-TK gene showed strong exp ression of HSV-TK protein. Cells transduced with the HSV-TK gene exhib ited increased TK activity, ranging from 3- to 20-fold over an average baseline level. The human HeLa-CD4(+) cells infected with recombinant Sindbis virus containing the HSV-TK gene were sensitive to low concen trations of GCV (0.1-1 mu g/ml) and the 50% growth inhibitory concentr ation (IC50) was 0.6 mu g/ml, We also demonstrated applications of cel l type-specific Sindbis virus-mediated antigen-antibody targeting of t he HSV-TK/GCV system in vitro. Sindbis virus containing the HSV-TK gen e packaged in a helper virus displaying the IgG-binding domain of prot ein A on its envelope could infect various tumor cell lines in the pre sence of specific antibodies that recognize antigens on their surfaces . HSV-TK-transduced tumor cell lines exhibited sensitivity to GCV, Our data suggest the potential for targeted gene therapy of the HSV-TK/GC V system using a cell type-specific recombinant Sindbis virus vector-a ntibody system. (C) 1999 Wiley-Liss, Inc.