Fig 6.

ASLV virions, incubated with liposomes, with or without sTva, at pH 6.1 and pH 5.0. At pH 6.1, virion-liposome interactions were similar to those observed at neutral pH (A), although fusion products were occasionally found (A, right insert). (C) At pH 5.0, fewer intact virions and more fusion products (inset) were observed. (B and D) As at neutral pH, when the receptor was not present, virions and liposomes did not interact. (E to K) Tomographic slices of ASLV-liposome fusion products. (E) A fusion product (middle) is readily distinguishable from a virion (top right) or liposomes (bottom left). (F to K) Fusion products showed glycoproteins on their surfaces, contained patchy internal densities, and had diameters consistent with the fusion of an average-sized virus with a liposome. Arrows in panels I and J mark “compact” fusion-product contents. (J and K) Examples of fusion products that exhibited a partial layer of density beneath their membrane (arrowheads). Bars, 100 nm.