Reinfection-induced increase of rubella persistently infected cells in a macrophage-like cell line

The establishment and relevant characteristics of a long-term rubella persistent infected immortalised murine macrophage culture with a high proportion of persistent infected cells over uninfected is described. The high proportion of persistent infected macrophages was obtained through reinfection with the original virus. Prior to reinfection, 35–50% of the cells expressed viral antigen, 0.05–1.5% produced infective virus and extra-cellular virus was continuously produced with infective titers cyclically fluctuating between 102 and 107 TCID50/ml. After reinfection, the macrophages which expressed viral antigen and produced infective virus had increased to 75–90% and 30–45% respectively and extracellular virus was continuously produced with stable titer between 102–103 TCID50/ml. Furthermore, in the reinfected culture no significant variation was observed in the percentage of cells expressing antigen, producing virus and in the titer of extracellular virus for longer than a year of passages.