FIG. 7.

A gp65-specific antiserum neutralizes virus infectivity. An infectious, cell-free stock of HHV-7 was generated, and preincubated for 60 min at room temperature with a diluted aliquot of rabbit polyclonal antiserum raised against the baculovirus-derived gp65-(His₆) protein. SupT1 cells were then incubated with the treated virus preparation (MOI of ∼0.1), and infection was monitored by light microscopic examination of syncytium formation at 72 h following virus infection. Panels: A, negative control (uninfected SupT1 cells, with no added virus); B, positive control (SupT1 cells infected with HHV-7 in the absence of any antiserum); C and E, SupT1 cells exposed to the virus-containing inoculum and preincubated with gp65-reactive immune serum at a dilution of either 1:25 or 1:100, respectively; D and F, SupT1 cells exposed to the virus-containing inoculum and preincubated with preimmune rabbit serum at a dilution of either 1:25 or 1:100, respectively. Note the presence of extensive syncytia in panels B, D, and F, but not in the panels in which the virus inoculum was treated with the gp65-specific serum (panels C and E). Magnification, ×250.