SELECTIVE CYTOTOXICITY OF RICIN A CHAIN IMMUNOTOXINS TOWARDS MURINE CYTOMEGALOVIRUS-INFECTED CELLS

Immunotoxins were constructed by linking immunoglobulins specific for murine cytomegalovirus (MCMV) to deglycosylated ricin A chain. Toxicit ies toward MCMV-infected and uninfected cells were determined by measu ring the inhibition of protein synthesis following a 48-h exposure to immunotoxins commencing 24 h after infection. The 50% inhibitory conce ntrations ranged from 0.4 to 4 mu g/ml for infected cells and from 22 to 120 mu g/ml for uninfected cells. Selectivity indices ranged from 3 0 to 157. Control immunotoxins, which were constructed identically exc ept that the immunoglobulin moiety had no specificity toward MCMV anti gens, had 50% inhibitory concentrations of 50 and 100 mu g/ml toward i nfected and uninfected cells, respectively.