[Comparative study of the persistence of 3 RNA-containing viruses in a continuous cell culture of human origin].

A comparative study of chronic infecton of HEp-2 cells with tick-borne encephalitis (TBE), rabies (RV), and rubella (RuV) viruses was carried out. Throughout the entire period of chronic infection (CI) no signs of specific cell destruction by these viruses were observed. The infectious virus was regularly demonstrated in the culture fluid and chronically infected cells. The antigenic properties of the persisting viruses did not differ from those of the original strains. The persisting TBE and rabies viruses replicated in the susceptible cells at a higher temperature and formed plaques of a smaller size than the original virus. The number of chronically infected cells producing infectious virus was always less than the number of cells containing the virus-specific antigen. In all three types of chronic infection the cells supported virus persistence at 40 degrees C. In TBE and RuV chronically infected cells interference with heterologous viruses was marked while in HEp-2-RV homologous interference caused by formation of defective interfering particles was observed. Treatment of the cells with BUDR resulted in activation of the infection only in the HEp-2-TBE system. Experiments on transfection of the sensitive cells by using DNA from HEp-2-RV and HEp-2-RuV gave negative results. The importance of various factors in the mechanism of virus persistence in the chronically infected cells under study is discussed.