Infectious titers of SIVmac-derived vectors pseudotyped with different viral GPs.

Vectors carrying the GFP marker gene were generated with the indicated GPs of retroviral or nonretroviral (stars) origins. TE671 target cells were infected with dilutions of nonconcentrated vector preparations and the percentage of GFP⁺ cells was determined 3 days after infection. Infectious titers were calculated as GFP IU/mL. In duplicate experiments, vector producer cells expressing the FPV-HA were treated with 2 U Clostridium perfringensneuraminidase (Sigma-Aldrich, Saint Quentin, Fallavier, France) for 24 hours to induce the release of HA-pseudotyped particles from the surface of producer cells (FPV-HA + NA). (B) Schematic representation of the RD114/TR chimeric GP in which the cytoplasmic domain of the RD114 GP was replaced with that of the MLV-A GP. The sequences of the 3 topologic domains, ectodomain, transmembrane, and cytoplasmic tail, are shown. The GALV/TR chimeric GP was modified in a similar manner. (C) Incorporation of RD114 and RD114/TR GPs in virions was assessed in immunoblots of SIV vector particles pelleted through 20% sucrose cushions, using anti-RD114 SU and anti-CA antibodies. The position of the molecular weight markers is shown (kd).