A new method to detect lymphocytic choriomeningitis virus-specific antibody

A plaque reduction method for measuring lymphocytic choriomeningitis virus-sensitizing antibody in human serum is described. One volume of virus and one volume of serially diluted human serum were mixed and incubated for 2 h at 37 °C. One volume of suitably diluted anti-human immune globulin antiserum was added and incubation continued for o'5 h. Residual infectivity was then determined by means of a plaque assay employing L cell monolayer cultures and a methyl cellulose containing overlay medium. Of 75 sera from as many persons, 20 were positive with titres ranging from 64o to 10240. All positive sera were from verified cases or from persons who had had occupational contact with the virus. Close correlation of results was found between this method and a neutralization test employing mice, the one exception indicating that the in vitro assay for sensitizing antibody is more sensitive than the mouse assay for neutralizing antibody