FIG. 6.

Inactivation of cell surface-bound MuLV-E and MuLV-A by treatment with citrate buffer (pH 3.0). (A) Cells were incubated for 2 h at 4°C with a mixture of LAPSN(MuLV-E) and G1nβgSvNa(MuLV-A); the cells washed and then mock treated or treated with citrate buffer (pH 3) as described in Materials and Methods. Each value represents the mean and SEM of 12 determinations in two separate experiments. (B) Cells were mock treated or treated with citrate buffer (pH 3) as described in the text. Immediately after treatment the cells were infected for 2 h at 37°C with a mixture of LAPSN(MuLV-E) and G1nβgSvNa(MuLV-A). Each value represents the mean and SEM of eight determinations in two separate experiments.