Spontaneous rubella carrier cultures derived from tissues of infants with congenital rubella were studied in an attempt to elucidate a possible mechanism for viral persistence observed in these infants. Chronically infected cells were found to have a reduced growth rate and the cultures appeared to have a shortened life span. The rubella carrier state was not dependent on serum inhibitors or rubella antibodies. Virtually every cell in the carrier population was found to be producing virus. The carrier cultures could not be cured by rubella antibodies. The rubella-infected cells were resistant to superinfection with vesicular stomatitis virus and herpes simplex virus but were susceptible to infection with echovirus 11. The replication of vesicular stomatitis virus was apparently blocked at an intracellular site, for the virus readily adsorbed to the chronically infected cells and entered into an eclipse phase; however no infectious virus developed. No evidence of interferon production by these cells could be obtained. It is postulated that clones of rubella-infected cells in vivo, with properties similar to those in carrier cultures developed in vitro from tissues of in utero infected infants, might explain the observed viral persistence noted in congenital rubella.

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