[Chronic rubella virus-induced infection of human continuous cells]

A stable chronically rubella virus-infected culture of HEp-2-BK cells existing for over 30 months has been obtained as a result of a single inoculation and further passages. This system is characterized by the lack of cell destruction and permanent production of infectious virus in titres of 2.5-6.3 lg PFU/ml. Synthesis of RNAs of the same classes as in the acute infection was demonstrated in the chronically infected cell culture (CICC) but virion RNA production was less marked. Only a portion of the cells in the population was found to carry the infectious virus. Virus-free cell clones were as susceptible to rubella virus as the control culture. The process of persistence proved to be resistant to virus-specific antibody as well as to the effect of higher (40 degree C) or lower (34 degree C) temperatures. Actinomycin D, 5-bromodeoxyuridine, and 5-iodo-2-deoxyuridine exerted no significant effect on virus reproduction in CICC which, combined with negative results of the experiments on transfection of the susceptible cultures with DNA preparations recovered from CICC, evidenced against the role of integration mechanisms in the establishment and maintenance of the HEp-2-BK system. A clear-cut interference with a heterologous virus was demonstrated in HEp-2-BK culture. The formation of the chronic form of infection in HEp-2-BK culture appears to be due to weak cytocidal properties of rubella virus and formation of endogenous interferon.