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.