Figure 5.

LVs Bearing COCV.G and PIRYV.G Envelope Are Resistant to Inactivation by Complement

Vectors were diluted 1:20 (v/v) with serum-free medium or heat-inactivated (HI) or fresh human and mammalian serum, incubated at 37°C for 1 hr, and then plated on HEK293T cells. The percentage of GFP-positive cells was measured 2 days later via flow cytometry. Measured titers were normalized to those of serum-free samples. (A) The reduction of titers by sera after heat-inactivation at 56°C for 1 hr was less than 30% for all LVs. (B) Substantial proportions of LVs with VSVind.G, but not COCV.G, PIRYV.G, or RDpro env, were inactivated by complement. The data shown represent relative titers ± SD for four experiments performed in duplicate. (C) The design and the cross-over points of the chimeric G proteins are represented in linear diagrams, in which white bars stand for wild-type (WT) VSVind.G sequences, and WT COCV.G sequences are represented by black hatched bars. The cross-over point between the two WT sequences is indicated by the amino acid number above the bar. (D) Sensitivity of LVs pseudotyped with chimeric G proteins to inactivation by several mammalian sera. Reductions of titers by HI sera were less than 30% for all LVs (data not shown). The data shown represent relative titers ± SD for four experiments performed in duplicate.