Expression of the CD40 ligand(CD40L) on tumors can activate host immune systems and produce antitumor effects against the tumors. To deliver the CD40L gene efficiently,we evaluated the efficiency of transduction of different serotypes of adeno-associated virus(AAV) vectors in lung cancer A549 cells and compared the transduction efficiency of a conventional AAV vector with that of self-complementary AAV(scAAV) vectors as well. We determined that serotype AAV2/5 transduced A549 cells much more efficiently than serotypes AAV2/1,AAV2/2,AAV2/6,AAV2/7,AAV2/8,AAV2/9 and AAV2/10. And the transduction efficiency of scAAV2/5 was significantly higher than conventional AAV2/5. Furthermore,pretreatment with carboplatin,which is a chemotherapeutic agent used in lung cancer chemotherapy,substantially increased AAV-mediated transgene expression. The scAAV2/5 vectors encoding human CD40L were used to tranduce CD40L into A549 cells,which were then co-cultivated with immature human dendritic cells(DCs). Interleukin 12(IL-12) that was released was measured in the culture supernatant. Specificity of the immunostimulatory effect of CD40L was confirmed by blocking with a monoclonal antibody binding to human CD40L. The in vivo antitumor activity was evaluated in BALB/c nude mice hearing A549 lung cancer. scAAV2/5-CD40L showed significant inhibitory effects on the growth of transplanted tumor cells as compared with control group. These studies suggest that recombinant AAV2/5-CD40L may provide an effective form of therapy for lung cancer. (c)2007 Elsevier Inc. All rights reserved. Expression of the CD40 ligand (CD40L) on tumors can activate host immune systems and produce antitumor effects against the tumors. To deliver the CD40L gene efficiently, we evaluated the efficiency of transduction of different serotypes of adeno-associated virus (AAV) vectors in lung cancer A549 cells and compared the transduction efficiency of a conventional AAV vector with that of self-complementary AAV (scAAV) vectors as well. We determined that serotype AAV2 / 5 transduced A549 cells much more efficiently than serotypes AAV2 / 1, AAV2 / 2, AAV2 / 6, AAV2 / 7, AAV2 / 8, AAV2 / 9 and AAV2 / 10. And the transduction efficiency of scAAV2 / 5 was significantly higher than conventional AAV2 / 5. Furthermore, pretreatment with carboplatin, which is a chemotherapeutic agent used in lung cancer chemotherapy, substantially increased AAV-mediated transgene expression. The scAAV2 / 5 vectors encoding human CD40L were used to tranduce CD40L into A549 cells, which were then co-cultivated with immature human dendritic cells (DCs). The in vivo antitumor activity was as in BALB / c nude mice (Interleukin 12 (IL-12) that was released was measured in the culture supernatant. Specificity of the immunostimulatory effect of CD40L was was by blocking with a monoclonal antibody binding to human CD40L. see A549 lung cancer. scAAV2 / 5-CD40L showed significant inhibitory effects on the growth of transplanted tumor cells as compared with control group. These studies suggest that recombinant AAV2 / 5-CD40L may provide an effective form of therapy for lung cancer. ) 2007 Elsevier Inc. All rights reserved.