FIG 8.

Determination of the amino acids in the Env protein that are required for the FeLV TG35-2 phenotype. (A) The indicated mutant FeLV env genes, constructed using either the TG35-2 or TG35-4 (FeLV-A) env gene, were generated by site-directed mutagenesis or recombination of the VRA (18). The mutant FeLV env gene, mt3,4, was newly generated in this study. The env sequences other than the VRA, derived from TG35-2 or TG35-4 env, are referenced on the right. (B) The indicated Env-pseudotyped viruses were tested for infection in the MDTF, MDTF expressing feline THTR1 (MDTF-feTHTR1), and MDTF expressing feline RFC (MDTF-feRFC) cell lines. The infection units were indicated by log10 of β-galactosidase (LacZ)-positive cells per milliliter of supernatant. Data represent the averages from three independent experiments, with the standard deviations shown.