Acute and chronic infection of human lymphoblastoid cell lines with measles virus.

Several human continuous lymphoblastoid cell lines (LCL) having T or B characteristics were infected with low and high passage strains of measles virus. All of the cell lines were susceptible to one or the other or to both strains of measles virus with the production of typical syncytial giant cells and released cell-free infectious virus into the supernatant medium. There was no consistent pattern of susceptibility of LCL with either T or B characteristics to infection by measles virus. Viral induced cytolysis of the lymphoblastoid cells in many of the lines was marked, but in the LCL that could be maintained over longer periods of time, a state of chronic, less cytolytic and persistent infection could be established. The infection was characterized by the production of moderate amounts of cell-free infectious virus for up to 4 1/2 months after initial infection with little change in the number of viable cells in culture. Long-term low multiplicity of infection (MOI) experiments demonstrated that the cell-free infectious virus was being produced only by a small number of cells, but the majority of cells in culture contained measles antigen that was in a cell-restricted, noninfectious, or defective form. Electron microscopic examination of the chronically infected cells demonstrated that many of them contained aggregates of hollow tubular intranuclear nucleocapsids whose "stripped" appearance was in marked contrast to the larger granular intracytoplasmic nucleocapsids found during earlier stages of infection. It is theorized that the persistent infection of LCL may serve as a model in understanding the immune mechanisms which permit latent and chronic measles infection in man.