Antibody and complement mediated lysis of felid herpesvirus 1 infected cells in vitro

The lysis of cells infected by felid herpesvirus 1 (FHV) by feline anti-FHV antibody and complement was demonstrated. Lytic activity was sensitive to dilution of both antibody and, especially, complement. It was first detected within 10 to 20 minutes, increased rapidly during the next 30 minutes of incubation and then rose more slowly in a linear manner. Using standard antibody and complement concentrations and assay duration, it was shown that FHV infected cells underwent significant (P less than 0.05) lysis from eight hours after infection in a system in which FHV-specific membrane antigen was first detected at three hours after infection and spread of FHV by the intracellular route began eight to nine hours after infection. The ability of antibody and complement to reduce FHV spread in this system was demonstrated by a significant (P less than 0.05) reduction in FHV plaque numbers, although the restriction of spread was not absolute. Chelation of divalent cations and heat inactivation of complement factor B revealed that the lytic system was dependent on factor B and Mg2+ but not Ca2+, suggesting involvement of the alternative pathway of complement activation.