FIG. 3.

Treatment with NH₄Cl ablates fusion from within. VSV_IND-infected HECA2 cells (MOI = 2) were cultured in the presence of 1 and 20 mM NH₄Cl beginning at 3.5 hpi. At 9 (a, c, and e) and 24 (b, d, and f) hpi, the cells were fixed in methanol and stained with Giemsa stain. Giant cell formation was observed and recorded with an Nikon TMD microscope equipped with a 35-mm camera. (a and b) Untreated VSV_IND-infected HECA2 cells; (c and d) infected HECA2 cells treated with 1 mM NH₄Cl; (e and f) infected HECA2 cells treated with 20 mM NH₄Cl.