Lysis of herpes simplex virus-infected cells early in the infectious cycle by human antiviral antibody and complement

Abstract

Chang liver (CL) cells and human embryonic lung fibroblasts (MRC-5) were infected with type 1 herpes simplex virus (HSV), ant the time postinfection at which these cells became susceptible to lysis by antiviral antibody and complement of human origin was determined in a 51Cr release assay. Using a 1:2 dilution of fresh HSV antibody-positive human serum, we initially detected specific lysis by 4 h postinfection in HSV-infected CL cells and by 3 h postinfection in HSV-infected MRC-5 cells in suspension. MRC-5 cells were more completely lysed than CL cells. Protein inhibition studies with cycloheximide showed that all of the HSV-infected CL cells and most (83%) of the HSV-infected MRC-5 cells injured early in the infectious cycle were attacked because of newly synthesized viral surface antigens rather than because of adherent input virus. Suspension cells early in the infectious cycle were less completely lysed and required higher concentrations of both antiviral antibody and complement for lysis than cells that were in the later stages of infection (18 h postinfection). Guinea pig serum was inferior to human serum as a complement source for lysis of early infectious cycle cells. Lysis early in the infectious cycle was directly proportional to the multiplicity of infection and inversely proportional to the cell concentration. Infected cells in monolayers were lysed less readily and about 1 to 2 h later in the infectious cycle than infected cells in suspension. This difference was pronounced for CL cells, but modest for MRC-5 cells. These studies demonstrate that, despite previously held notions, HSV-infected tissue culture cells can be lysed by antiviral antibody and complement early in the infectious cycle before the initial production of progeny virus particles. The demonstration of lysis was highly dependent on experimental conditions, however, including cell type, suspension versus monolayer culture, cell density, and concentration of antibody and complement as well as the source of complement.