Characterization of measles virus-specific cytotoxic antibodies by use of a chronically infected cell line.
The complement-dependent cytotoxic effects of measles virus specific antibodies on a chronically infected cell line were studied by a microcytotoxicity assay. Cell damage was determined by trypan blue staining. Monospecific antisera against the hemagglutinin (HA) and the hemolysin (HL) of the virus were both cytotoxic. Rabbits, immunized with measles virus, developed cytotoxic antibodies in parallel with the appearance of antibodies against the measles virus HA and HL. Human sera with high antibody titers against HA and HL also gave a specific cytotoxic reaction. The main part of the activity was carried by IgG in rabbit sera tested within 2 weeks after primary immunization and only IgM. The serum reaction was characterized by a prozone. The maximal degree of cytotoxicity varied between tests performed on different occasions. Complement, at higher concentrations than were used for analysis of antibody-mediated cytolysis, caused a significant lysis of infected cells. Cerebrospinal fluid (CSF) samples containing measles virus-specific antibodies were investigated. CSF from patients with subacute sclerosing panencephalitis displayed a pronounced cytotoxicity without a prozone. CSF samples from four patients with multiple sclerosis were identified by a specific cytotoxic reaction despite low titers of antibodies against HA and HL.